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View my account settingsINTRODUCTION
Ceramic-on-ceramic hip replacements have generated great interest in recent years due to substantial improvements in manufacturing techniques and material properties1. Microseparation conditions that could occur due to several clinical factors such as head offset deficiency, medialised cup combined with laxity of soft tissue resulting in a translation malalignment, have been shown to cause edge loading, replicate clinically relevant wear mechanisms2,3 and increase the wear of ceramic-on-ceramic bearings3,4. The aim of this study was to investigate the influence of increasing the femoral head size on the wear of ceramic-on-ceramic bearings under several clinically relevant simulator conditions.
MATERIALS AND METHODS
The wear of size 28mm and 36mm ceramic-on-ceramic bearings (BIOLOX®
INTRODUCTION
Retrieval and clinical studies of metal-on-metal (MoM) bearings have associated increased wear1 and elevated patient ion levels2 with steep cup inclination angles and edge loading conditions. The University of Leeds have previously developed a hip simulator method that has been validated against retrievals and shown to replicate clinically relevant wear rates and wear mechanisms3,4. This method involves introducing lateral microseparation to represent adverse joint laxity and offset deficiency. This study aimed to investigate the effect of microseparation representing translational malpostion, and increased cup inclination angle, representing rotational malposition, in isolation and combined on the wear of different sizes (28 and 36mm) MoM bearing in total hip replacement (THRs).
MATERIALS AND METHODS
The wear of size 28mm and 36mm MoM THRs bearings was determined under different
INTRODUCTION
Several clinical studies demonstrated long-term adjacent-level effects after implantation of spinal fusion devices[1]. These effects have been reported as adjacent joint degeneration and the development of new symptoms correlating with adjacent segment degeneration[2] and the trend has therefore gone to motion preservation devices; however, these effects have not been understood very well and have not been investigated thoroughly[3].
The aim of this study is to investigate the effect of varying the stiffness of spinal fusion devices on the adjacent vertebral levels. Disc forces, moments and facet joint forces were analyzed.
METHODS
The AnyBody Modeling System was used to compute the in-vivo muscle and joint reaction forces of a musculoskeletal model. The full body model used in this study consists of 188 muscle fascicles in the lumbar spine and more than 1000 individual muscle branches in total. The model has been proposed by de Zee et al.[3], validated by Rasmussen et al.[4] and by Galibarov et al.[5]. The new model[5] determines the individual motions between vertebrae based on the equilibrium between forces acting on the vertebrae from muscles and joints and the passive stiffness in disks and ligaments, figure 1a. An adult of 1.75 m and 75 kg with a spinal implant in L4L5 was modeled. This model was subjected to a flexion-extension motion using different elastic moduli to analyze and compare to a non-implanted scenario. The analyzed variables were vertebral motion, the disc reaction forces and moments, as well as facet joint forces in the treated and the adjacent levels: L2L3, L3L4, L4L5 and L5-Sacrum.
Introduction
Osteoarthritis (OA) represents a leading cause of disability and a growing burden on healthcare budgets. OA is particularly vexing for young, active patients who have failed less invasive therapies but are not ideal candidates for HTO or arthroplasty. Often, patients suffering in this wide therapeutic gap face a debilitating spiral of disease progression, increasing pain, and decreasing activity until they become suitable arthroplasty patients. An implantable unloading device was evaluated for the treatment of medial knee OA in this patient population.
Joint overload has been cited as a contributor to OA onset or progression. In response, the KineSpring® System (Moximed, Inc, USA) has been designed to reduce the load acting on the knee. The unloader is implanted in the subcutaneous tissue without violating the joint capsule, thus preserving the option of future primary arthroplasty. The implant may be particularly useful for young, active patients, given the reversibility of the procedure and the preservation of normal flexibility and range of motion.
Methods and Results
The KineSpring System was implanted in 79 patients with isolated medial knee OA, and the longest duration exceeds two and a half years. Treated patients were young and obese (mean age: 52 years, range 32–75; mean BMI: > 30 kg/m2, range 21–45). Acute implant success, adverse events, and clinical outcomes using validated patient reported outcomes tools were recorded at baseline, post-op, 2 and 6 weeks, and 3, 6, 12 and 24 months post-op. All centers received ethics committee approvals prior to enrolling patients in the study.
Mean surgical time was 72 min (range 45–153 minutes), and all patients were discharged after a few days. Patients recovered rapidly, achieving full weight bearing within 1–2 wks and normal range of motion by 6 weeks. Most patients experienced significant pain relief and functional improvement by six weeks, with results sustained beyond the two-year follow-up visit. WOMAC Pain improved from 43 at baseline to 13 at 2 years (p<0.001), WOMAC Function improved from 43 at baseline to 11 at 2 years (p<0.001), and WOMAC Stiffness improved from 52 at baseline to 18 at 2 years (p<0.001). Patients reported satisfaction with implant and its appearance.
Introduction
The most common method for accurate kinematic analysis of the knee arthroplasty uses bi-planar fluoroscopy and model-based RSA. The main challenge is to have access to reverse-engineered CAD models of the implant components, if not provided by the company, making this method impractical for a clinical study involving many types or sizes of implants. An alternative could be to reconstruct the 3D primitive features of the implant, such as cylindrical pegs, flat surfaces and circular boundaries, based on their 2D projections. This method was applied by Kaptein et al. (2006) for hip implants. However, despite its broad potential, it has not yet been applied for studying TKA kinematics. This study develops a methodology for feature-based RSA of TKA and investigates the range of accuracies in comparison to model-based RSA.
Methods
Joint-3D software was developed in the MATLAB programming language to segment and fit elementary 2D features such as circles, lines, and ellipses to the edges of the parts on the radiographs (Figure 1). The software has the capability to reconstruct the 3D location and orientation of the components based on their 2D projections. To test the accuracy of the system a standard primary knee replacement system (Zimmer NexGen) was implanted on bone replica models, and positioned at 0° to 120° flexion at 30° intervals, simulating a lunge activity. For each pose, a multi-planar radiography system developed in our lab (Amiri et al., 2011) was used to take a sagittal and a 15° distally rotated radiograph (Figure 2a).
Figure 1 shows the features C, L, and E segmented on the tibia and femur. The 3D reconstruction is performed based on a number of functions: Functions ‘
To determine the errors, model-based RSA measures were used as the reference using the reverse-engineered models of the components in JointTrack software (University of Florida).
Introduction
Poor clinical outcomes following total knee arthroplasty (TKA) can be related to improper alignment of the components. The main challenge is the variability in biomechanical references, especially in cases of severe deformity or dysplasia, and in determining the surgical landmarks intraoperatively. An intraoperative imaging tool can be very useful to assess the alignments when there is still a chance for correction. We investigated, on cadaveric specimens, the accuracy of using iso-centric (ISO-C) imaging (that reconstructs 3D from multiple 2D fluoroscopic images) for this purpose.
Methods
Six fresh frozen cadaveric knees were implanted with a standard TKA system and imaged using an ISO-C 3D C-arm (Arcadis Orbic ISO-C). Each knee was scanned two times with the Iso-C scanner and with appropriate image settings to capture the transepicondylar axis (TEA) and the tibial tubercle individually. A CT scan of each specimen was acquired as the reference for comparison.
The ISO-C 3D reconstructed volumes were analyzed on the C-arm. For the CT images, the 3D data were processed in Analyze software with the same objective. The surgical and clinical TEA was determined by moving and rotating an oblique cutting plane (Figure 1a:CT and 1c:ISO-C). This oblique slice was then moved distally to picture the femoral pegs (Figure 1b:CT and 1d:ISO-C). The angle between these two references (angle α in Figure 1) defined the rotational alignment.
For the tibial component, the first cutting slice was oriented parallel to the component. A second slice was defined just distal to the component, and then moved distally to find the tibial tubercle in the third slice. The orientation of the tibial component was determined by fitting a rectangular box to the component boundary (Figure 2a:CT and 2d:ISO-C). The bone orientation was defined by a line connecting the centroid of a polygon drawn over the boundary of the cortical bone (Figure 2b:CT and 2e:ISO-C) to the medial third of the tibial tubercle (Figure 2c:CT and 2f:ISO-C). Measurements were repeated five times, the overall accuracies determined in comparison to CT, and the correlation between the ISO-C and CT determined by the Spearman rank (
Background
Acetabular component malpositioning during hip arthroplasty increases the risk of dislocation, reduces range of motion and can be responsible for early wear and loosening. There have been numerous reports on the optimal orientation of the acetabular component in total hip arthroplasty (THA). Lewinnek et al recommended an abduction angle of 40°±10° and an anteversion of 15°±10° for cup alignment in THA. The purpose of the in vivo study was to compare computer assisted acetabular component insertion versus free-hand placement. The goal of the cadaveric study was to compare
Methods
A controlled randomized matched prospective study was performed in two groups of 30 patients. In the first group, cup positioning was assisted by an imageless computer assisted orthopaedics system, based on Bone Morphingâ (CAOS+ group). In the control group, a free-hand cup placement was performed (CAOS- group). A same cementless cup has been used in the two groups. All the patients were operated by the same surgeon through an anterolateral approach. Cup anteversion and abduction angles were measured on three-dimensional CT-scan reconstruction postoperatively for each patient by an independent observer with special cup evaluation software. In vitro, four clinicians were asked to register ten times in a randomly change order the anterior pelvic plane landmarks in four different acquisition conditions: a cutaneous acquisition, a draped cutaneous acquisition, ultrasound acquisition and a direct bone acquisition on two cadavers. The mean and standard deviation of error for each anterior pelvic plane acquisition method were expressed as rotation and tilt about the relevant reference plane and compared.
Aims/Hypothesis
The aims of this study were: 1) to quantitatively analyse the amount of knee extension that is achieved with +2mm incremental increases in the amount of distal femoral bone that is resected during TKA in the setting of a flexion contracture, 2) to quantify the amount of coronal plane laxity that occurs with each 2mm increase in the amount of distal femur resected. In the setting of a soft tissue flexion contracture, we hypothesized that although resecting more distal femur will reliably improve maximal knee extension, it will ultimately lead to increased varus and/or valgus laxity throughout mid-flexion.
Methods
Seven fresh-frozen cadaver legs from hip-to-toe underwent TKA with a posterior stabilized implant using a measured resection technique with computer navigation system equipped with a robotic cutting-guide, in this IRB approved, controlled laboratory study. After the initial tibial and femoral resections were performed, the posterior joint capsule was sutured (imbricated) through the joint space under direct visualization until a 10° flexion contracture was obtained with the trial components in place, as confirmed by computer navigation. Two distal femoral recuts of +2mm each where then subsequently made and after the remaining femoral cuts were made, the trail implants were reinserted. The navigation system was used to measure overall coronal plane laxity by measuring the mechanical alignment angle at maximum extension, 30°, 60° and 90° of flexion, when applying a standardized varus/valgus load of 9.8 [Nm] across the knee using a 4kg spring-load located at 25cm distal to the knee joint line.(Figure 1) Coronal plane laxity was defined as the absolute difference (in °) between the mean mechanical alignment angle obtained from applying a standardized varus and valgus stress at 0°, 30, 60° and 90°. Each measurement was performed three separate times and averaged.
The maximal extension angle achieved following each 2mm distal recut was also recorded. Two-tailed student's t-tests were performed to analyze whether there was difference in the mean laxity at each angle and if there was a significant improvement in maximal extension with each recut. P-values < 0.05 were considered significant.
Purpose
Our aim was to compare the passive kinematics and coronal plane stability throughout flexion in the native and the replaced knee, using three different TKA designs: posterior stabilized (PS), bi-cruciate substituting (BCS), and ultracongruent (UC). Our hypotheses were: 1.) a guided motion knee replacement (BCS) offers the closest replication of native knee kinematics in terms of femoral rollback 2.) the replaced knee will be significantly more stable in the coronal plane than the native knee; 3.) No difference exists in coronal plane stability between the 3 implants/designs throughout flexion.
Methods
After IRB approval, two cadaveric specimens were used for a pilot study to determine sample size. Five fresh-frozen hip-to-toe cadaveric specimens then underwent TKA using an anatomic measured resection technique with a computer-navigated robotic femoral cutting-guide. The PS, BCS, and UC TKA designs were implanted in each knee using the same distal and posterior femoral cuts to standardize the position of the implants. Computer navigation was then utilized to record the varus/valgus laxity of each implant at 0°, 30°, 60° and 90° of flexion while applying a standardized 9.8Nm moment.
Passive tibiofemoral kinematics were measured in a continuous passive motion machine from 10° to 110°. Femoral rollback on the tibia was calculated for the native and replaced knees by measuring the closest point (CP) on the femoral condyle to a transverse plane perpendicular to the mechanical axis of the tibia at each flexion angle.
Background
Hip arthroscopy is well established as a diagnostic and therapeutic tool in the native hip joint. However, its application in the symptomatic post-hip arthroplasty patient is still being explored.
Aims and Methods
We have described the use of hip arthroscopy in symptomatic patients following total hip replacement, resurfacing hip arthroplasty and partial resurfacing hip arthroplasty in 24 patients (study group), and compared it with arthroscopy of the native hip of 24 patients.
There is great interest to provide repeatable and durable treatments for arthritis localized to one or two compartments in the cruciate-ligament intact knee. We report a series of efforts to develop and characterize an implant system for partial knee resurfacing. We studied distal femoral morphology and found that the sagittal-plane relationships between the condylar and trochlear surfaces are highly variable (Figs 1 and 2). In response, we report the design of a multi-compartmental system of implants intended to anatomically resurface any combination of compartments (Fig 3). Finally, we report the results of a pilot fluoroscopic study of the in vivo knee kinematics in patients who received medial, medial plus patellofemoral and bi-condylar knee arthroplasty. The kinematic results suggest these treatments provide a stable knee with intact cruciate ligament function. This work shows various partial knee resurfacing treatments have the potential to provide excellent knee mechanics and clinical outcomes.
INTRODUCTION
Unicompartmental knee arthroplasty (UKA) can achieve excellent clinical and functional results for patients suffering from single compartment osteoarthritis. However, UKA is considered to be more technically challenging to perform, and malalignment of the implant components has been shown to significantly contribute to UKA failures. The purpose of this investigation was to determine the clinically realized accuracy of UKA component placement using surgical navigation and dynamically referenced tactile-robotics.
METHODS
Pre-op CT, post-op CT, and surgical plan were available for 22 knees out of the first 45 procedures performed using a new tactile-guided robotic system. 3D component placement accuracy was assessed by comparing the pre-operative plan with the post-operative implant placement (desired versus actual). Bone and implant models were obtained from postoperative CT scans taken immediately following the surgery. A 3D to 3D iterative closest point registration procedure was performed and the measured implant position was directly compared to the preoperative plan. Errors were assessed as single axis root-mean-square (RMS) entities.
Introduction
Navigated freehand cutting (NFC) technology simplifies bone cutting in laboratory trials by directly navigating implants and power tools [1]. Experiments showed that NFC bone cutting was faster than with conventional jigs. However, most delays occurred at the start of each cut [2]. Therefore, we further reduced starting times and gained more accuracy with a NaviPen and a ‘smart’ NaviPrinter [3]. There were used to physically mark a line on the bone surface indicating where each cut should start.
Materials & Methods
The OTM is a standalone wireless module composed of three main parts: a small laser projector, electronics for control and communication (WiFi), and a tracking frame. It is navigated in real-time with a Polaris tracker. Software routines on a proprietary NFC system compute its relative position to the target and dynamically re-calculate the image parameters. Such parameters are sent to the OTM for processing, image generation, and projection
Introduction
Genu recurvatum is a deformity rarely seen in patients receiving total knee arthroplasty. This deformity is defined as hyperextension of the knee greater than 5°. The incidence of recurvatum has been cited in the literature as less than 1%.
Purpose
The purpose of this study was to report data on 1510 consecutive total knee replacements (TKR) with navigation to demonstrate that the incidence of genu recurvatum is higher than what is cited in the literature.
IN THE PAST success of TKA has been measured by ROM with maximum flexion as a bench mark, along with good stability of the knee joint MAINLY IN EXTENSION. Due to changing demographics our TKA population has shifted to more active and demanding patients which want to return to normal daily living, including professional and recreational sports activities. With the patella in place, we define a ligament “balanced resection” technique using the elibra device, and are able to optimize our results and meet younger, more active patient's expectations. Our workflow consists of a flexion gap first technique, maximizing posterior condylar offset, hence maximizing flexion with optimal ligament balance.
This flexion gap is then transmitted to the extension gap, initially using custom made spacer blocks either neutral or angled in 1°, 2° or 3° applied to the elibra sensing device and more recently by using a specific designed extension gap balancer. The immediate and short term postoperative observations concerning femoral component rotation, patellar tracking, influence of patella in place versus subluxed on flexion gap balance, varus-valgus alignment and complete mitigation of ligament releases will be discussed.
Purpose
The purpose of this study was to compare joint line changes between posterior-stabilized (PS) and cruciate-retaining (CR) computer navigated total knee arthroplasties (TKA) and to evaluate the impact on functional outcome.
Background
Restoration of the native joint line has been a common goal in all TKA designs. Computer-navigated TKA in increasingly being favoured by many surgeons, due to increased precision and lesser complications. Few studies have reported the effect of computer navigated TKA on joint line restoration. It remains to be seen if the greater precision offered by computer-navigated TKA in restoration of joint line translates to improvement in functional outcome.
Background
Hemiarthroplasty of the hip involves the replacement of the femoral side of the joint with a metal prosthesis, resulting in metal-on-cartilage articulation. The two most common types of hemiarthroplasty used are the Austin Moore and the Thomson, both of which are available in either Titanium (Ti) or cobalt chromium (CoCr). Hemiarthroplasty may be more cost effective in elderly patients who have lower life expectancy and are less active.
Materials and Methods
Three Ti and two CoCr hemiarthroplasty components were obtained following revision surgery. Four had an articulating diameter of 44mm and the other was 46mm diameter. These five hemiarthroplasties were analysed using a Mitutoyo LEGEX322 co-ordinate measuring machine (CMM) (manufacturer's claimed scanning accuracy of 0.8μm). In each case a wear map was generated and the wear volume from the articulating surface was calculated using a bespoke MATLAB program.
Introduction
Unicompartmental knee arthroplasty (UKA) was first described over 30 years ago and allows replacement of a single compartment in patients who have isolated osteoarthritis.1 However, UKA is more technically challenging than total knee arthroplasty due to limited exposure as a minimally invasive procedure. In addition to component alignment and fixation, ligament balancing plays an important role in implant survival.2 Some failures of early UKA systems were attributed to a failure to adequately balance the knee. The development of robots to aid in performing the procedure has lead to renewed interest in this surgical technique.
The use of a robot-assisted system allows the orthopaedic surgeon to verify that balancing sought pre-operatively correlates with that obtained at surgery. Some studies have shown good post-operative mechanical alignment utilizing this method.3 The aim of this study was to examine the variation in pre-operative templated ligament balance and that obtained during the operation.
Methods
Data were prospectively collected on 52 patients (51 knees) undergoing robot-assisted unicompartmental knee arthroplasty by a single surgeon. For pre-operative planning, dynamic ligament balancing was obtained of the operative knee under valgus stress, prior to any bony cuts. Final intra-operative images with the prosthesis in place were taken without valgus stress. Positive values denoted loose ligamentous balancing while negative values indicated ligament tightness.
INTRODUCTION
Total hip arthroplasty (THA) is regarded as one of the most successful surgeries in medicine. However, recent studies have revealed that ideal acetabular cup implantation is achieved less frequently than previously thought, as little as 50% of the time. It is well known that malalignment of the acetabular component in THA may result in dislocation, reduced range of motion, or accelerated wear. This study reports accuracy of a tactile robotic arm system to ream the acetabulum and impact an acetabulur cup compared to manual instrumentation.
METHODS
12 fresh frozen cadaveric acetabulae were pre-operatively CT scanned and 3D templating was used to plan the center of rotation, and anteversion and inclination of the cup. Each specimen received THA, six prepared manually and six prepared with robotic arm guidance. Tactile, visual, and auditory feedback was provided through robotic guidance as well as navigated guided reaming and cup impaction. The robotic guidance constrained orientation of instruments thus constraining anteversion, inclination, and center of rotation for reaming, trialing, and final cup impaction. Post-operative CT scans were taken of each specimen to determine final cup placement for comparison to the pre-operative plans.
Introduction
In complex primary and revision total knee replacement (TKR) the operating surgeon may encounter proximal tibial bone defects. The correct management of such defects is fundamental to both the initial stability and long-term survival of the prosthesis. Cement or metal augments have been used to address some such type II unconstrained defects [1].
Aim
The aim of this finite element (FE) study was to analyse the comparative behaviour of cement and metal based augments and quantify the stresses within these different augments and underlying cancellous bone.
Introduction
In complex primary and revision total knee replacement (TKR) the operating surgeon may encounter proximal tibial bone defects. The correct management of such defects is fundamental to both the initial stability and long-term survival of the prosthesis. Block or wedge-shaped metal augments are used to address some such type II unconstrained defects1.
Aim
The aim of this finite element (FE) study was to assess the effects of block and wedge-shaped metal augments upon the shear stresses in the cement mantle at the bone-implant interface of an augmented TKR.
Introduction
Concerns regarding UHMWPE wear particle induced osteolysis in total hip replacement (THR, [1]) have led to alternative materials to be sought. Carbon-fibre reinforced poly-ether-ether-ketone (CFR-PEEK) has shown reduced wear in hip and knee configurations compared with conventional polyethylene [2-4]. The aim of this study was to investigate the wear performance of a ceramic-on-CFR PEEK THR through a simulator study.
Methodology
Five 36mm diameter Biolox Delta heads were paired with extruded CFR-PEEK cups and tested in a hip wear simulator (Simulator Solutions, UK) for 10 million cycles (Mc). Tests were performed in a Prosim hip simulator, which applied a twin peak loading cycle, with a peak load of 3kN. Flexion-extension of −15 to +30 degrees was applied to the head and internal-external rotation of +/− 10 degrees was applied to the cup, components were mounted anatomically. The lubricant was 25% (v/v) calf serum supplemented with 0.03% (w/v) sodium azide. Wear was assessed gravimetrically at several intervals adjusted for moisture uptake using loaded and unloaded soak controls.
Robotic assisted spine surgery was a breakthrough in the evolution of spinal surgery, gradually gaining its place as an alternative technique for conventional spinal procedures. As the general population's life expectancy increased so does the incidence of spinal pathology and with it emerged an urging need for a safer and more accurate means of treatment.
In our institute we apply the “Spine Assist” platform for a variety of spinal procedures as Vertebroplasties, biopsies, Pedicular screws insertion and an inter-vertebral fusion – GOLIF procedures.
This study is designed to analyze the learning curve of each procedure, regarding the amount of fluoro images (
All spinal procedures using the “Spine Assist” platform were included in this study; all took place from 2006 until September 2010.
Exclusion criteria were procedures with failed pre-op registration, and robotic assisted procedures that were converted to conventional fluoroscopic assisted during the operation.
Every single surgery of all types of procedures was analyzed regarding the amount of FI taken, FE time and net operation time. Pedicular screws insertion was grouped into sets of four, where the same parameters were evaluated.
Altogether we preformed 106 robotic assisted Vertebroplasty procedures. During this period a distinct learning curve was observed and analyzed. For the first ten Vertebroplasties an average of 12 FI were taken with a net operation time of 53.6 min per procedure. Analyzing the first 40 procedures has shown less FI per procedure (5 FI) and a net operation time of 48.6 min/procedure. Data drawn from the 51 following Vertebroplasties has set the standards of 4 FI with a net operation time of 25.6 min/procedure.
Two Vertebroplasty procedures were not completed due to failure of software registration.
Pedicular screws are a mean for stabilization of vertebral motion units. During a six years period 706 screws were inserted, out of whom 98 were inserted using percutaneous technique. Comparing the insertion of a set of 4 screws we found a significant improvement regarding the number of FI, FE time and the net operation time between the first ten procedures and the rest with a mean of 20 FI /4 FI and net screw insertion time of 82 min/ 25 min respectively. We found no difference in the parameters comparing percutaneous Vs open Pedicular screws insertion.
The mean accuracy of all procedures was 0.3 mm compared to the pre planned screw trajectory. No false route was detected in any of the 506 procedures.
This robotic assisted technique is a new and safe approach aiming to shorten the duration of the procedure, thus reducing the patient and surgeon exposure to radiogenic dose. The essence of robotic assisted surgery is a pre planned needle/screw trajectory aiming to reduce the possible intra-operative complication, inaccuracies and possible mishaps emerging during “free hand” procedures.
Gaining more experience using the spine assist platform, as shown in this detailed learning curve, enabled us to leverage the platform for ultra-accurate procedures as the percutaneous intervertebral fusion – GOLIF, Vertebroplasty for burst fractures etc.
Introduction
Obesity is a direct contributor to degenerative joint disease, and as the prevalence of obesity increases globally it is likely that more overweight patients will present for hip replacement surgery. There are reports that overweight patients in the UK's National Health Service, typically with a Body Mass Index (BMI) over 30 (BMI 30–39 obese, BMI≥40 morbidly obese), are being denied operations on the premise that they are at risk of significant complications. Enhanced Recovery Programmes (ERP) are designed to enable patients to recover quickly and return home safely within a few days. The aim of this study was to compare the outcome of hip replacements in obese and non-obese patients enrolled in our ERP.
Methods
We prospectively studied 350 patients who underwent primary and revision total hip replacements and were treated through our ERP form March 2010 to January 2011. The mean age was 68 (range 23–92 years). 130 patients (37%) were considered obese with a BMI of >30. 11 patients (3%) were considered morbidly obese with a BMI >40. They were age & sex-matched with the non-obese patients. Outcomes measured included: Length of stay, wound complications (including surgical site infections), deep vein thrombosis and blood transfusion requirements. Data was collected to 42 days following discharge.
INTRODUCTION
Electron beam melting is a promising technique to produce surface structures for cementless implants. Biomimetic apatite coatings can be used to enhance bone ingrowth. The goal of this study was to evaluate bone ingrowth of an E-beam produced structure with biomimetic coating and compare this to an uncoated structure and a conventionally made implant surface.
METHODS
Introduction
Numerous studies have been conducted to investigate the kinematics of the lumbar spine, and while many have documented its intricacies, few have analyzed the complex coupled out-of-plane rotations inherent in the low back. Some studies have suggested a possible relationship between patients having low back pain (LBP) or degenerative conditions in the lumbar region and various degrees of restricted, excessive, or poorly-controlled lumbar motion. Conversely, others in the orthopedic community maintain there has been no distinct correlation found between spinal mobility and clinical symptoms. The objective of this study was to evaluate both the in-plane and coupled out-of-plane rotational magnitudes about all three motion axes in both symptomatic and asymptomatic patients.
Methods
Ten healthy, 10 LBP, and 10 degenerative patients were CT scanned and evaluated under fluoroscopic surveillance while performing flexion/extension of the lumbar spine. Three-dimensional, patient-specific bone models were created and registered to fluoroscopic images using a 3D-to-2D model fitting algorithm.
Introduction
Kinematics tracking is the process by which the motion of the joints is studied. This motion consists of relative rotation and translation of the joint bones. Joint motion analysis is used in diagnosis of joint pathology, as well as studying the normal joint function. Currently, fluoroscopy is used in joint kinematics tracking. We are researching the use of pulse-echo A-mode ultrasound for the bone motion tracking instead of the fluoroscopy to avoid its radiation. In this work we performed feasibility study using simulation, and concluded that it is feasible to perform knee motion tracking with accuracy of 2 mm.
Methods
The idea of the proposed system is to attach a number of single-element ultrasound transducers to a brace as shown in Figure 1. This brace will have a commercially available optical or electromagnetic tracking system's probe attached to it to track the global motion of the brace. The ultrasound transducers will be responsible for transcutaneously detecting points over the surface of the bone. The bone's echo extracted from each signal at each transducer will be registered in the optical or electromagnetic tracker's coordinate frame to create a set of points acquired over the surface of the bone. These points represent the bone's position at that point of time. A 3D model of the bone is then registered to these points using the iterative closest point method (ICP) to estimate the bone's position. At each tracking step, the 3D model will be at a position close to the new position of the points set, because this process will be repeated at a rate of 100 Hz or more in order to ensure that the change in the bone's position between every two successive tracking steps is small enough to guarantee high tracking accuracy. In this work we simulated the mentioned process using real kinematics data obtained for a patient using fluoroscopy. 3D models of the proximal tibia and distal femur were segmented from CT scans of the patient's knee. These models were then moved using the kinematic data in incremental steps. Simulated points over the surface of the bones (simulating the points on the bone's surface to be acquired using ultrasound) were used to track the bones' simulated motion using another set of the bones 3D models which move only according to the registration with the simulated points. In other words, the tracking models follow the simulated points' motion. Simulation was performed using deep knee bend kinematics data.
Introduction
Are there really ‘conventional’ bearings, offering more security and less risk than the ‘alternative’ bearings that feature in the programme?
Alternative, when used as an adjective has 2 meanings: offering or expressing a choice, as in several alternative plans different from or functioning outside the usual or conventional:
eg alternative newspaper, alternative rock music, alternative medicine
This paper reviews the elements that make up the bearing couples available today in the developed world, and tests each bearing against these meanings.
Materials
what are the alternatives?
The materials available today fall into the following broad families:
The current generation of knee replacements are based upon assumptions from kinematic studies that preceded their designs. These implants were further limited by practical restrictions imposed by affordability, materials and manufacturing, and finally by the methods available to surgeons to prepare the bone and implant them. The early designs of knee seldom distinguished left from right, as the early kinematic work had not appreciated the very different functions of the medial and lateral compartments. Trochlea shape and position within devices was also limited by the published work on the way the knee bends. Surgical insertion has been limited to landmark based registration, and adjustment of the kinematics by soft tissue releases. However accurately such operations were performed, they could not restore normal function, as the kinematics of the joint were quite different from the normal knee.
Recently, we have begun to appreciate three distinct axes of the knee joint: the flexion axis, the extension axis and the trochlea axis. These can be reliably found from 3d imaging, but cannot be immediately established by eye, or by conventional jigs, which must rely on unreliable landmarks acquired in surgery.
The current market leaders in knee joint sales do not reflect these three axes in their joint designs, so the instrumentation used to insert them cannot restore the kinematics of the normal knee. The emerging partial replacements can be designed to take the axes and their resulting kinematics into account. If they are then inserted using robotic assistance, or patient specific guides, they can restore joints to these axes reliably. Knee function following such conservative surgery reflects this improvement in kinematics with higher functional scores and faster top walking speeds than has ever been possible using conventional devices inserted using the conventional landmark based surgical techniques.
Treatment of Paprosky type 3A and 3B defects in revision surgery of a hip arthroplasty is challenging. In previous cases such acetabular defects were treated with massive structural allograft bone reconstructions using cemented all-polyethylene cups. In our department we started using custom made triflanged cups to restore the articulation of the hip.
The triflanged cups were designed on the basis of CT-image analysis. We are using a new type of implant construction technique with additive technology. This is a production process consisting of ion beam sintering joining metal powder particles layer upon layer on the basis of a 3D model data. The production technique is similar to rapid prototyping manufacturing.
7 Patients have been treated with this new technique. The case studies will be presented with their clinical and radiographic follow-up.
We think that additive technology is a breakthrough in treating this kind of severe acetabular defects.
Introduction
Patellar stability is an important component for a correct kinematic behaviour of the knee that depends on several factors such as joint geometry, muscles strength and soft tissues actions. Patellofemoral (PF) maltracking can results in many joint disorders which can cause pain and mobility alterations. The medial patellofemoral ligament (MPFL) is an important stabilizing structure for the patellofemoral joint. The aim of this study was to analyze patellofemoral kinematics with particular attention to the contribution of MPFL on patella stability.
Methods
Using a navigation system PF kinematics during passive flexion/extension movements with quadriceps loaded at 60N, was recorded on 6 cadavers in three different anatomical conditions: intact knee, MPFL cut and MPFL reconstructed with graft. Test on patella was conducted without lateral force and with applied lateral force (25N). Tilt and lateral shift was evaluated in both cases at 0°. 30°, 60°and 90° of flexion.
INTRODUCTION
Symptomatic hip disorders associated with cam deformities are routinely treated with surgery, during which the deformity is resected in an effort to restore joint range of motion, reduce pain, and protect the joint from further degeneration. This is a technically demanding procedure and the amount of correction is potentially critical to the success of the procedure: under-resection could lead to continued progression of the OA disease process in the joint, while over-resection puts the joint at risk for fracture. This study compares the accuracy of a new robotically assisted technique to a standard open technique.
METHODS
Sixteen identical Sawbones models with a cam type impingement deformity were resected by a single surgeon simulating an open procedure. An ideal final resected shape was the surgical goal in all cases. 8 procedures were performed manually using a free-hand technique and 8 were performed using robotic assistance that created a 3-dimensional haptic volume defined by the desired post-operative morphology. All of 16 sawbones, including uncut one as well, were scanned by Roland LPX-600 Laser scanner with 1mm plane scanning pitch and 0.9 degree of rotary scanning. Post-resection measurements included arc of resection, volume of bone removed and resection depth and were compared to the pre-operative plan.
INTRODUCTION
Allograft reconstruction after resection of primary bone sarcomas has a non-union rate of approximately 20%. Achieving a wide surface area of contact between host and allograft bone is one of the most important factors to help reduce the non-union rate. We developed a novel technique of haptic robot-assisted surgery to reconstruct bone defects left after primary bone sarcoma resection with structural allograft.
METHODS
Using a sawbone distal femur joint-sparing hemimetaphyseal resection/reconstruction model, an identical bone defect was created in six sawbone distal femur specimens. A tumor-fellowship trained orthopedic surgeon reconstructed the defect using a simulated sawbone allograft femur. First, a standard, ‘all-manual’ technique was used to cut and prepare the allograft to best fit the defect. Then, using an identical sawbone copy of the allograft, the novel haptic-robot technique was used to prepare the allograft to best fit the defect. All specimens were scanned via CT. Using a separately validated technique, the surface area of contact between host and allograft was measured for both (1) the all-manual reconstruction and (2) the robot-assisted reconstruction. All contact surface areas were normalized by dividing absolute contact area by the available surface area on the exposed cut surface of host bone.
Summary sentence
The bowing of the femur defines a curvature plane to which the proximal and distal femoral anatomic landmarks have a predictable interrelationship. This plane can be a helpful adjunct for computer navigation to define the pre-operative, non-diseased anatomy of the femur and more particularly the rotational alignment of the femoral component in total knee arthroplasty (TKA).
Background and aims
There is very limited knowledge with regards to the sagittal curvature -or bowing- of the femur. It was our aim (1) to determine the most accurate assessment technique to define the femoral bowing, (2) to define the relationships of the curvature plane relative to proximal and distal anatomic landmarks and (3) to assess the position of femoral components of a TKA relative to the femoral bowing.
The Exeter stem is a polished cemented stem that has been associated with an excellent survivorship. However, this wedge shaped stem has also been associated with a relative higher risk for a peri-periprosthetic fracture due to the wedge-shaped configuration that can lead to a Vancouver type B2 fracture when the stem is being driven downwards inside the femoral canal by a traumatic blast. Traditionally, these fractures should be treated with a revision stem because the stem has become loosened in the fractured cement mantle. We present a case series of 5 cases where our treatment algorithm was to first let the non-displaced fracture to consolidate by 6 weeks of limited weight bearing as tolerated in order to conduct a second stage in-cement revision. This would simplify the revision procedure dramatically. However, all patients are currently pain free and do not require revision surgery although they are being monitored very closely.
We conclude that non-displaced Vancouver type B2 fractures can be approached by a 2 stage treatment algorithm where the initial step is to let the fracture consolidate with limited weight bearing.
INTRODUCTION
Recent studies indicated that the knee has a single flexion/extension axis but debated the location of this axis. The relationship of the flexion/extension axis in the coronal plane to the mechanical axis has received little attention. The purpose of this study was to investigate the relationship of the various axes and references with respect to the mechanical axis in the coronal plane
MATERIALS AND METHODS
Subjects were prospectively scanned into a Virtual Bone Database (Stryker Orthopaedics, Mahwah, NJ). Database is a collection of body CT scans from subjects collected globally. Only CT Scans that met the following qualifications were accepted: ≤1 mm voxels and had slice thickness that was equal to the spacing between the slices (≤ 1.0mm).
For each CT Scan, a frontal plane was created through the 2 most posterior points of the medial/lateral condyles and the most posterior point of the trochanter. Then, a transverse plane was created perpendicular to the frontal plane and bisects the 2 most distal points on the medial/lateral condyles. Finally, a saggital plane was created that was perpendicular to the frontal and transversal planes.
The following axes were identified: Mechanical Axis of the Femur (MAF) (line between the center of the femoral head and the center of the knee sulcus); Transepicondylar Axis Posterior Cylindrical Axis (PCA) (line between the Medial/Lateral Condylar Circle – best fit circle to three points identified on surface).
Measurements made: Angle of MAF and the Joint-Line (Femoral Joint Angle), Angle of the MAF and the Transepicondylar Axis (Femoral TE Angle), and Angle of the MAF and the Posterior Cylindrical Axis (Femoral PC angle). Angles measuring 90° were neutral or perpendicular to the MAF. Angles measured <90° were valgus and >90° were varus.
Introduction
It is well known that total knee arthroplasty (TKA) does not preserve normal knee kinematics. This outcome has been attributed to alteration of soft-tissue balance and differences between the geometry of the implant design and the normal articular surfaces. Bicompartmental knee arthroplasty (BKA) has been developed to replace the medial and anterior compartments, while preserving the lateral compartment, the anterior cruciate ligament (ACL), and the posterior cruciate ligament (PCL). In a previous study, we reported that unicompartmental knee arthroplasty did not significantly change knee kinematics and attributed that finding to a combination of preservation of soft-tissue balance and minimal alteration of joint articular geometry (Patil, JBJS, 2007). In the present study, we analyzed the effect of replacing trochlear surface in addition to the medial compartment by implanting cadaver knees with a bicompartmental arthroplasty design. Our hypothesis was that kinematics after BCKA will more closely replicate normal kinematics than kinematics after TKA.
Methods
Eight human cadaveric knees underwent kinematic analysis with a surgical navigation system. Each knee was evaluated in its normal intact state, then after BKA with the Deuce design (Smith & Nephew, Memphis, TN), then after ACL sacrifice, and finally after implanting a PCL-retaining TKA (Legion, Smith & Nephew). Knees were tested on the Oxford knee rig, which simulates a quadriceps-driven dynamic deep knee bend. Tibiofemoral rollback and rotation and patellofemoral shift and tilt were recorded for each condition and compared using repeated measures ANOVA for significance.
Knee mechanics - Knee forces during ADL and sports activities in TKA patients
Background
Tibiofemoral forces are important in the design and clinical outcomes of TKA. Knee forces and kinematics have been estimated using computer models or traditionally have been measured under laboratory conditions. Although this approach is useful for quantitative measurements and experimental studies, the extrapolation of results to clinical conditions may not always be valid. We therefore developed a tibial tray combining force transducers and a telemetry system to directly measure tibiofemoral compressive forces in vivo.
Methods
Tibial forces were measured for activities of daily living, athletic and recreational activities, and with orthotics and braces, for 4 years postoperatively. Additional measurements included video motion analysis, EMG, fluoroscopic kinematic analysis, and ground reaction force measurement. A third-generation system was developed for continuous monitoring of knee forces and kinematics and for classifying and identifying unsupervised activities outside the laboratory using a wearable data acquisition hardware.
Anterior knee pain is one of the most frequently reported musculoskeletal complaints in all age groups. However, patient's complaints are often nonspecific, leading to difficulty in properly diagnosing the condition. One of the causes of pain is the degeneration of the articular cartilage. As the cartilage deteriorates, its ability to distribute the joint reaction forces decreases and the stresses may exceed the pain threshold. Unfortunately, the assessment of the cartilage condition is often limited to a detailed interview with the patient, careful physical examination and x-ray imaging. The X-ray screening may reveal bone degeneration, but does not carry sufficient information of the soft tissues' conditions. More advanced imaging tools such as MRI or CT are available, but these are expensive, time consuming and are only suitable for detection of advanced arthritis. Arthroscopic surgery is often the only reliable option, however due to its semi-invasive nature, it cannot be considered as a practical diagnostic tool. However, as the articular cartilage degenerates, the surfaces become rougher, they produce higher vibrations than smooth surfaces due to higher friction during the interaction. Therefore, it was proposed to detect vibrations non-invasively using accelerometers, and evaluate the signals for their potential diagnostic applications.
Vibration data was collected for 75 subjects; 23 healthy and 52 subjects suffering from knee arthritis. The study was approved by the IRB and an Informed Consent was obtained prior to data collection. Five accelerometers were attached to skin around the knee joint (at the patella, medial and lateral femoral condyles, tibial tuberosity and medial tibial plateau). Each subject performed 5 activities; (1) flexion-extension, (2) deep knee bend, (3) chair rising, (4) stair climbing and (5) stair descent. The vibration and motion components of the signals were separated by a high pass filter. Next, 33 parameters of the signals were calculated and evaluated for their discrimination effectiveness (Figure 1). Finally the pattern recognition method based on Baysian classification theorem was used for classify each signal to either healthy or arthritic group, assuming equal prior probabilities.
The variance and mean of the vibration signals were significantly higher in the arthritic group (p=2.8e-7 and p=3.7e-14, respectively), which confirms the general hypothesis that the vibration magnitudes increase as the cartilage degenerates. Other signal features providing good discrimination included the 99th quantile, the integral of the vibration signal envelope, and the product of the signal envelope and the activity duration. The pattern classification yielded excellent results with the success rate of up to 92.2% using only 2 features, up to 94.8% using 3 (Figure 2), and 96.1% using 4 features.
The current study proved that the vibrations can be studied non-invasively using a low-cost technology. The results confirmed the hypothesis that the degeneration of the cartilage increases the vibration of the articulating bones. The classification rate obtained in the study is very encouraging, providing over 96% accuracy. The presented technology has certainly a potential of being used as an additional screening methodology enhancing the assessment of the articular cartilage condition.
Introduction
In this work, we present the first real-time fully automatic system for reconstruction of patient-specific 3D knee bones models using ultrasound raw RF data. The system was experimented on two cadaveric knees, and reconstruction accuracy of 2 mm was achieved.
Methods
To use the highest available contrast and spatial resolution in the ultrasound data, the raw RF signals were used directly to automatically extract the bone contours from the ultrasound scans. Figure 1 shows a sample ultrasound B-mode image for cadaver's distal femur, showing some of the scan lines raw RF signals as well as the final extracted contour using our method.
An ultrasound machine (SonixRP, Ultrasonix Inc) was used to scan the knee joint and the RF data of the scans are acquired by custom-built (using Visual C++) software running on the ultrasound machine. An optical tracker (Polaris Spectra, Northern Digital Inc) was attached to the ultrasound probe to track its motion while being used in scanning.
The scanning of the knee was performed at two flexion angles (full extension, and deep knee bend). At each position, the knee was fixed in order to collect scans that represent a partial surface of the bone (which will be later mutually registered to represent the whole bone's surface). Figure 4 shows fluoroscopy images of a patient's knee, showing the different articulating surfaces of the knee bones visible to the ultrasound at different flexion angles. Figure 5 shows a dissected cadaver's knee showing the articulating surfaces visible to ultrasound at 90 degrees flexion.
The custom-built software collects the RF data synchronized with the probe tracking data for each ultrasound frame. Each frame of the RF data is then processed to extract the bone contour. The bone contours are automatically extracted from the RF data frame with frame rate of 25 frames per second. Figure 2 shows a flowchart for the contour extraction process.
The extracted bone contours were then used by the our software, along with the ultrasound probe's tracking data, to reconstruct point clouds representing the bones' surfaces. These point clouds were then aligned to the mean model of the bone's atlas using ICP and integrated together to form 3D point cloud of the bone's surface. A 3D model of the bone is then reconstructed by morphing the mean model to match the point cloud. Figure 3 shows a flowchart for the point cloud and 3D model reconstruction process.
INTRODUCTION
Thermal necrosis of the femoral head, due to heat generation during cement polymerization, is a concern in hip resurfacing. Bone necrosis could cause fractures and/or implant loosening. Some authors1 found an inverse relationship between the size of the femoral component and the risk of revision after hip resurfacing. We postulate that smaller implants contain proportionally more cement than larger ones and that this could explain the effect of implant size on revision rate. As such, we investigated the relation between implant size and both, the average cement mantle thickness and the cement-filling index (fraction of cement volume and total volume within the implant).
MATERIALS AND METHODS
Nineteen human femoral heads, collected during total hip arthroplasty, were machined for hip resurfacing with original ReCap (Biomet) instruments. The head sizes were chosen so we could implant two resurfacing heads for each even size between 40 and 56 mm, and one for size 58 mm. Each reamed head was provided with a number of anchoring holes proportional to the head size and was kept at 37°C. After pressure-lavage with water at 20°C, polymeric replicas of the original Recap implants were cemented according to a strict protocol. The exact amount of Refobacin Bone Cement LV (Biomet) needed to fill half the volume of the implant was pored into the resurfacing head and 2.5 minutes after starting cement mixing, the implant was manually impacted on the reamed femoral head.
Specimens were scanned with computer tomography from the distal border of the resurfacing head to the top of the dome and CT-images were analyzed with an adapted version of validated segmentation software2. Based on gray values we identified four different elements: the polymeric stem and the outer shell of the implant, the cement-free cancellous bone and the cement mantle. Both, the average cement mantle thickness and the cement-filling index were calculated as described previously3.
Surface arthroplasty or resurfacing represents a significant development in the evolution of hip replacement. A hip resurfacing arthroplasty (HRA) is a bone conserving alternative to total hip arthroplasty (THA) that restores normal joint biomechanics and load transfer and ensures joint stability. Metal-on-metal (MoM) bearings have been preferred for these large diameter articulations because of their lower volumetric wear and smaller particulate debris compared to metal-on-poly-ethylene bearings. Of the many engineering factors which have contributed to the success of the MoM bearing, the metallurgy, diametral clearance, sphericity and surface finish were thought to be most important. More recently, adverse reactions to metal particles and ions generated by wear and corrosion of the metal surfaces have focused the attention on the importance of coverage angle and cup positioning. Currently, the scientific consensus is that cup coverage angle, diametral clearance and metallurgy have their importance in that order. Precise understanding of manufacturing variables is imperative in obtaining clinical consistency and safety in the patient. It is important to examine femoral fixation, bone remodelling, and wear of MoM implants. For the second and third generation MoM HRA various designs and biomaterials have been used. We have conducted a randomised, controlled trial comparing 9 different hip resurfacing prostheses. Clinical and radiographic outcome and whole blood, serum and urine metal ion levels are evaluated at 6 months, 1 year and 2 years in 180 patients with 9 different HRA designs and the differences are analyzed. Besides, the design quality of the 9 different metal-on-metal prostheses and their accessory instruments have been judged during the operation. The Durom with its Metasul history may claim a metallurgic advantage, and in combination with the highest coverage angle of all cups, it may be the best wear couple, as suggested by low ion measurements. However, as discussed above, an optimal bearing alone is not sufficient to achieve a successful hip resurfacing.
The surgical treatment of young adults with end-stage hip disease has been a challenge. Inferior THA survival in the young, perceived advantages of hip resurfacing versus THA and advancements in tribology, led to the introduction of 3rd generation Metal-on-Metal-Hip-Resurfacing-Arthroplasty (MoMHRA). To-date, thousands of such prostheses have been implanted worldwide in younger patients, yet little is known regarding long-term outcome. The only studies reporting greater than 10 year outcome come from designer centres with survivorship varying between 88.5–96% at 12 years. Arthroplasty Registries (AR) have reported less favourable survivorships with female gender and size having a negative effect on survival. In our independent hip resurfacing centre in Ghent, Belgium, a single surgeon has implanted more than 3500 HRA over more than 12 years. A cohort of 149 patients who received a Birmingham Hip Resurfacing (BHR) at a mean age of 50 years at surgery have now reached a minimum 10 years follow-up. The overall 12-year survival in these young adults is 93.1% (95% CI: 88.3–98.0), 99% in males and 87.3% in females. These survivorship data are superior to registry reported figures of THA amongst young patients and correspond well with previous reports from designer centres. The long-term survivorship and clinical outcome of the BHR are excellent in men, uninfluenced by preoperative diagnosis or age. However, survivorship in women is inferior and usually related to increased wear and reactions to metal debris.
Malpositioning of components with associated wear-induced soft tissue fluid collections is the most frequent factor leading to failure of a HRA. In our experience, mid-term outcome following revision is good and complication and re-revision rates can be low. Surgical experience, early intervention in cases of mal-positioned implants, clinical use of ion levels, implantation of larger ceramic-on-ceramic THA femoral heads and patient education are factors in improving outcome and reducing complication and re-revisions following HRA revision.
Background
There is no consensus on which glenoid plane should be used in total shoulder arthroplasty. Nevertheless, anatomical reconstruction of this plane is imperative for the success of a total shoulder arthroplasty.
Methods
Three-dimensional reconstruction CT-scans were performed on 152 healthy shoulders. Four different glenoid planes, each determined by three surgical accessible bony reference points, are determined. The first two are triangular planes, defined by the most anterior and posterior point of the glenoid and respectively the most inferior point for the Saller's Inferior plane and the most superior point for the Saller's Superior plane. The third plane is formed by the best fitting circle of the superior tubercle and the most anterior and posterior point at the distal third of the glenoid (Circular Max). The fourth plane is formed by the best fitting circle of three points at the rim of the inferior quadrants of the glenoid (Circular Inferior). We hypothesized that the plane with normally distributed parameters, narrowest variability and best reproducibility would be the most suitable surgical glenoid plane.
Humeral implant design in shoulder arthroplasty has evolved over the years. The third generation shoulder prostheses have an anatomic humeral stem that replicates the 3-dimensional parameters of the proximal humerus. The overall complication rate has decreased as a result of these changes in implant design. In contrast, the rate of periprosthetic humeral fractures has increased. To avoid stem-related complications while retaining the advantages of the third generation of shoulder implants, the stemless total evolutive shoulder system has been developed. The indications, the surgical technique, and the complications of this humeral implant in shoulder arthroplasty will be described.
INTRODUCTION
While standard instrumentation tries to reproduce mechanical axes based on mechanical alignment guides, a new “shape matching” system derives its plan from kinematic measurements using pre-operative MRIs. The current study aimed to compare the resultant alignment in a matched pair cadaveric study between the Shape Match and a standard mechanical system.
METHODS
A prospective series of Twelve (12) eviscerated torso's were acquired for a total of twenty four (24) limb specimens that included intact pelvises, femoral heads, knees, and ankles. The cadavers received MRI-scans, which were used to manufacture the Shape Match cutting guides. Additionally all specimen received “pre-operative” CT-scans to determine leg axes. Two (2) investigating surgeons performed total knee arthroplasties on randomly chosen sides by following the surgical technique using conventional instruments. On the contralateral sides, implantation of the same prosthesis was done using the Kinematic Shape Match Cutting Guides. A navigation system was used to check for leg alignement. Implant alignement was determined using post-operative CT-scans. For statistical analysis SPSS was used.
Introduction
As population grows older, and patients receive primary joint replacements at younger age, more and more patients receive a total hip prosthesis nowadays. Ten-year failure rates of revision hip replacements are estimated at 25.6%. The acetabular component is involved in over 58% of those failures. From the second revision on, the pelvic bone stock is significantly reduced and any standard device proves inadequate in the long term [Villanueva et al. 2008]. To deal with these challenges, a custom approach could prove valuable [Deboer et al. 2007].
Materials and methods
A new and innovative CT-based methodology allows creating a biomechanically justified and defect-filling personalized implant for acetabular revision surgery [Figure 1].
Bone defects are filled with patient-specific porous structures, while thin porous layers at the implant-bone interface facilitate long-term fixation. Pre-operative planning of screw positions and lengths according to patient-specific bone quality allow for optimal fixation and accurate transfer to surgery using jigs.
Implant cup orientation is anatomically analyzed for required inclination and anteversion angles. The implant is patient-specifically analyzed for mechanical integrity and interaction with the bone based upon fully individualized muscle modeling and finite element simulation.
INTRODUCTION
The cement quantity and distribution within femoral hip resurfacings are important for implant survival. Too much cement could cause thermal bone necrosis during polymerisation. Insufficient cement and cement-implant interfacial gaps might favour mechanical loosening. Exposed cancellous bone within the implant, might facilitate debris-induced osteolysis. This study assessed the impact of the cementing technique on the cement mantle quality in hip resurfacing.
METHODS
We prepared 60 bovine condyles for a 46 mm ReCap (Biomet) resurfacing and cemented polymeric replicas of the original implant using five different techniques: low-viscosity cement filling half the implant with and without suction (LVF+/−S), medium-viscosity cement spread inside the implant (MVF), medium-viscosity cement packed on bone (Packing) and a combination of both last techniques (Comb.). Half the specimens had six anchoring holes. Specimens were CT-scanned and analyzed with validated segmentation software [1].
We assessed, with an analysis of covariance, the effect of the cementing technique (fixed factor), the presence of anchoring holes (fixed factor) and the bone density (covariate) on the cement mantle quality.
INTRODUCTION
Resurfacing prostheses are implanted by impaction onto the prepared femoral head. Ceramic resurfacings can be proposed as an alternative to metal implants, combining bone conservation with mitigation of sensitivity reaction risks. With low wall-thickness required for bone conservation, their strength must be verified. This study aimed to assess a ceramic resurfacing prosthesis' strength under surgical loads using a computational model, tuned and verified with physical tests.
METHODS
Tests were conducted to obtain baseline impact data (Fig1 left). Ø58mm DeltaSurf prostheses (Finsbury Development Ltd., UK), made from BIOLOX Delta (CeramTec AG, Germany) ceramic were cemented onto 40pcf polyurethane foam stubs (Sawbone AG, Sweden) attached to a load cell (Instron 8874, Instron Corp., USA). Ten repeatable 2ms−1 slide hammer impacts were applied with a 745g mass. The reaction force at the bone stub base was recorded, and the cumulative impulse was calculated by integrating reaction force over time. A half-plane symmetry model was developed using LS-DYNA (ANSYS Inc., USA) explicit dynamic FE analysis software (Fig1, right). The bone stub was constrained, and the mallet was given an initial velocity of 2.0m/s. Outputs were the impact reaction force at the bone stub base, the impact duration and the peak tensile prosthesis stress.
First, the model was solved representing the experimental setup, to fit damping parameters. Then the damped model was used to predict the peak prosthesis stresses under more clinically representative loads from a 990g mallet. The smallest (Ø40mm) and largest (Ø58mm) prosthesis heads in the size range were analysed, with two impact directions: along the prosthesis axis, and with the impactor inclined at 10°.
Introduction
Increased oxidative stability of orthopedic implants can be achieved by adding an antioxidant, such as Vitamin E (VE) to UHMWPE[1]. The effect of shelf live and accelaterated aging in combination with shelf live on antioxidative effectiveness of VE needs to be investigated to better understand the long-time behavior of VE-blended UHMWPE in an oxidative environment. Currently, IR techniques provide detection limits as low as 0.05 %w/w[2], also it is known that thermo analytical techniques can push the limit of detection down to 10 ppm[3]. The goal of this study was to quantify VE in UHMWPE powder and compression molded UHMWPE with 11 different VE concentrations using FTIR and DSC techniques and to establish respective regression curves.
Methods & Materials
GUR 1050 UHMWPE resin (Ticona, Germany) was blended with VE (DSM, Netherlands) to the following target concentrations (%w/w): 0.01, 0.02, 0.05, 0.1, 0.25, 0.35. Concentrations of 0.001, 0.002, 0.003, 0.004, 0.005 were obtained by mixing of the 0.1 powder with virgin GUR 1050 powder. VE-free GUR 1050 was used as reference. Samples of blended resin were compression molded in a low oxygen environment atmosphere at Zimmer Inc. (Warsaw, IN). Subsequently the blocks were microtomed, creating films with a thickness of 200µm for each concentration. The VE concentration was measured using infrared (IR) spectroscopy (BioRad FT6000). The ratios were calculated by normalizing the integrated ether C-O(R) signal (1232cm−1 to 1275cm−1) and the integrated hydroxyl C-O(H) signal (1190cm−1 to 1228cm−1) using the twisting CH bond (1980cm∗∗∗∗∗ to 2100cm−1) as reference peak area. Oxidative induction time (OIT) at 200°C was measured according to ASTM D 3895–98 using blended and mixed powder samples.
Studies have indicated that the shallow Ultra High Molecular Weight Polyethylene (UHMWPE) acetabular socket or the socket with no head center inset can significantly increase the risk of hip joint dislocation. A previous study suggested the rim loading model in UHMWPE socket and metal femoral head can generate an intrinsic dislocating force component pushing head out of socket. Recently there has been renewed interest in dual mobility articulations due to the excellent stability. The outer bearing couple of the dual mobility articulations are comprised of the UHMWPE femoral head and metal acetabular socket while inner bearing is the locked conventional metal-poly construct. The acetabular socket is also featured by an anatomically shaped head inset wall. The purpose of this study was to theoretically compare the intrinsic dislocating force between conventional metal head on UHMWPE socket articulations and the poly head on metal socket articulations used in the dual mobility cup under direct loading.
The 3-D finite element analysis (FEA) models were same as previous study but with different material combinations. Sixty FEA model assemblies were consisted of CoCr or UHMWPE femoral heads and their corresponding 10mm thick generic UHMWPE or CoCr acetabular sockets. There were five different head center insets of 0, 0.5, 1, 1.5 and 2mm for each of six bearing diameters of 22, 28, 32, 36, 40 and 44mm for either sockets. The joint load of 2,446N was applied through the femoral head center as the same fashion as previous study. The dislocating force generated by the joint loading force intrinsically pushed femoral head out of socket. FEA results were verified with two data points of physical testing of actual UHMWPE 28mm ID liners with 0 and 1.5mm head center insets.
The highest dislocating force was 1,269N per 2,446N of rim loading force for the 0mm head center inset in poly cup with 22mm CoCr femoral head or the case of easiest to dislocate. The lowest dislocating force was 17.7N per 2,446N force for the 2mm inset in CoCr socket with 44mm poly head which therefore was the least likely to dislocate. The average dislocating force decreased by 78% from metal head- poly cup couple to poly head - metal cup couple. The dislocating force decreased as the head center inset and head size increased in all material cases.
The study suggests that not only the head center inset and head size but also the bearing material combinations can affect the intrinsic dislocating force component. The dual mobility poly head and metal socket couple generates less intrinsic dislocating force in all comparable conditions for conventional metal head and poly socket couple. During the hip separation and vertical placement of the cup, all variables found in this study may play the important rules to maintain joint stability. The stiffened cup rim reduces the deformation and thus reduces the potential cup wedge effect to generate dislocating force. The result of this study should provide the guidance to improve acetabular cup design for better joint stability.
Bone preserving hip arthroplasty devices are appealingfor use in young patients because their high-demand activities and extended lifetimes makes the prospect of multiple revisions a reality. Therefore prostheses which ensure a straightforward revision with a low complication rate and good clinical outcome are favourable for young and active patients.
Modern hip resurfacing serves these conditions and shows very good mid-term and now longer term (10 and 13 years) results especially in osteoarthritis. With other diagnoses like avascular necrosis, deformities of the femoral head in m. Perthes or slipped femoral epiphysis (SUFE), or in large bone cysts and erosive arthritis the bone stock of the femoral head gives insufficient support to the femoral component. In these conditions the alternative to a resurfacing procedure had been a stemmed total hip arthroplasty (THA).
The Birmingham Mid Head Resection device (BMHR; Smith&Nephew Orthopaedics) is an alternative to resurfacing and to a stemmed THA. The BMHR device consists of an uncemented short stem made of titanium alloy and a large diameter cobalt-chrome head. The stem does not enter the femoral canal thus facilitating future revisions. The metal-on-metal bearing is the same as in resurfacing. The instrumentation allows switching from a planned BHR to the BMHR. The BMHR uses the unique anatomy of the head neck junction to prepare internally a cone that matches the frustoconical section of the BMHR stem. Thus a cement free press fit can be achieved. This maintains anatomical load transmission and avoids osteopenia of the proximal fenur.
Since 2006 we have performed 662 BMHR implantations. The indications were osteoarthritis in about 70%, dysplasia in 20%, AVN 5,5%, posttraumatic OA in 3%, SUFE and m. Perthes in 1%. Complications occured in 3,2%. Fractures of the femoral neck occured in 8 patients, 4 of them caused by technical errors in the beginning, 3 because of higher risk indication. All revisions were performed successfully and the cup was retained. Low grade infections in 2 cases with one stage revision and 3 unstable cups needed to be reinserted. All revisions were successful. One early dislocation was treated by closed reduction, another remained unstable and was treated by THA. In conclusion we continue to use the BMHR to bridge the gap between resurfacing and stemmed THA because the complications we experienced are not inevitable and had become very rare with our growing experience.
Recent trends in surgical techniques for THR, i.e. MIS and anterior approaches, have spawned an interest in and possible need for shorter femoral prostheses. Although, early clinical investigations with custom short stems have reported very encouraging results, the transition to off-the-shelf (OTS) versions of shorter length prostheses has not met with the same degree of success. Early reports with OTS devices have documented unacceptably high and significant incidences of implant instability, migration, mechanical/aseptic failure, and technical difficulty in achieving reproducible implantation outcomes. They have highlighted the absolute need for a better understanding of the consequences of changes in implant design as well as for improvements in instrumentation and surgeon training.
Two basic questions must be addressed. First, what is the purpose of a stem? And second, can stem length be reduced and if so by how much can this be safely done. What are the effects of stem shortening and are there other design criteria which must take on greater importance in the absence of a stem to protect against implant failure.
To examine these questions a testing rig was constructed which attempts to simulate the in vivo loading situation of a hip, fig. 1. Fresh cadaveric femora were tested with the femora intact and then with femoral components of varying stem length implanted to examine the distribution of stresses within the femur under increasing loads as a function of stem length.
Our studies indicated that a stem is not an absolute requirement in order to achieve a well functioning, stable implant. However in order to reduce the possibility of mechanical failure a reduced stem or stemless implant absolutely must have three important characteristics to its design. First, it must have sufficient medial/lateral dimension to provide stability against subsidence and varus stress; second it must have a flat posterior surface, parallel and in contact with the posterior endosteal surface of the proximal femur with which to maximize A/P stability against flexion/extension forces (As a consequence of this design feature, appropriate anteversion must be achieved in the neck region of the prosthesis and not by rotation of the implant within the proximal metaphyseal cavity of the femur); and third, the implant must also have a cross-sectional geometry that will stabilize against torsional loading about the long axis of the femur.
Therefore, simply reducing the length of an existing implant to accommodate changes in surgical techniques may not be a reasonable or safe design change. Such shortened versions of existing stem designs must be rigorously tested before being released for general use. The required design parameters outlined above have been clinically validated in custom fabricated implants. They have been shown to reduce aseptic loosening and migration of a short stem femoral implant. This report will provide the clinical review of a multi-center experience with the first 150 off-the-shelf “Lateral Flare” short stem implants.
Background
Total hip arthroplasty for Crowe type IV developmental dysplasia of the hip is a technically demanding procedure. Restoration of the anatomical hip center frequently requires limb lengthening in excess of 4 cm and increases the risk of neurologic traction injury. However, it can be difficult to predict potential leg length change, especially in total hip arthroplasty for Crowe type IV developmental hip dysplasia. The purpose of the present study was to better define features that might aid in the preoperative prediction of leg length change in THAs with subtrochanteric femoral shortening osteotomy for Crowe type IV developmental dysplasia of the hip.
Patients and Methods
Primary total hip arthroplasties with subtrochanteric femoral shortening osteotomy were performed in 70 hips for the treatment of Crowe type IV developmental hip dysplasia. The patients were subdivided into two groups with or without iliofemoral osteoarthritis. Leg length change after surgery was measured radiographically by subtracting the amount of resection of the femur from the amount of distraction of the greater trochanter. Preoperative passive hip motion was retrospectively reviewed from medical records and defined as either higher or lower motion groups.
Shoulder arthroplasty has experienced exponential growth in the past 10–15 years, largely due to improvements in anatomical design, increased application of technology to address various clinical pathology, and improved access to experienced shoulder surgeons. Glenohumeral arthritis has historically been the most common indication for a shoulder replacement, and glenoid wear has been the main concern with regards to longevity of the prosthesis. Attempts to improve glenoid components involve alterations in peg or keel configuration, as well as the introduction of metal backed constructs. Early experience with metal backed components led to very poor results with often catastrophic loosening and destruction of glenoid bone. Proximal humerus fractures are another common indication for a shoulder arthroplasty, and in these cases, tuberosity fixation and healing are the challenge precluding a consistently successful result. More recently, base plate fixation in the setting of a reverse shoulder arthroplasty has come to the forefront as a significant factor.
Trabecular metal technology has emerged as a compelling method of enabling powerful bone ingrowth to the surfaces of arthroplasty components. Trabecular metal is composed of tantalum. It is used to form a carbon scaffold which has a modulus between that of cancellous and cortical bone, thus has some flexibility when made into an independent construct. Vapor deposition onto arthroplasty surfaces provides a bone ingrowth surface. There is interest in utilizing trabecular metal for glenoid and tuberosity fixation in particular.
Trabecular metal proximal coated stems provide an ingrowth surface for tuberosity fixation in the setting of proximal humerus fractures. Long term results are still pending. Because the metal is much less stiff then other metals, trabecular metal has recently been used along the back of polyethylene glenoids. The original design had a problem with fracture at the base of the pegs. A redesigned component instituting a cruciate design was implemented, and is currently available on a limited release basis with promising early results. The use of trabecular metal on the deep surface of the reverse arthroplasty baseplate and the proximal aspect of the reverse stem has led to successful fixation, allowing cementless fixation of both the humeral and glenoid components.
Learning objectives of this presentation include: Understand the mechanical characteristics of trabecular metal and its bone ingrowth characteristics. Familiarize with currently available prosthetics incorporating trabecular metal technology. Case presentations utilizing trabecular metal coated components.
Cementless arthroplasty has progressed substantially in the recent decades from pressfit implantation to porous-coated and later HA-coated implant fixation as its ultimate current state-of-the-art incarnation. As a consequence ever younger and older patients have received the benefits of hip and other arthroplasty although attention to age-related factors is key to success. Key factors for success, from the implant perspective, are adequate primary stability of the device in the bone supported by design and surface structure variables that together with optimal implant biocompatibility result in durable osseo-integration of the device. The high activity levels of younger patients but similarly the generally inferior muscular condition of elderly patients require special attention for the stability of the hip joint with avoidance of impingement. Also bone quality may be a topic for consideration to avoid problems. Excellent survival rates past twenty years are documented in both literature and registries with quantitative studies confirming the excellent implant stability and bone quality. With an optimal consideration for patient related factors as well as anatomic reconstruction of the arthroplasty, modern cementless arthroplasty provides every patient an outlook on both excellent long term functionality and survival.
Introduction
Multiple techniques exist for performance of Total Knee Arthroplasty (TKA). In April 2010, MyKnee® Patient-Specific Instrumentation (Medacta International, SA, Castel San Pietro, Switzerland) was approved for use in TKA in the United States. The present retrospective study seeks to evaluate early results of this technique. 29 consecutive patients (30 consecutive TKA operations) underwent TKA using the MyKnee cutting-blocks. These results were compared to 30 consecutive patients utilizing Standard TKA method. The findings represent the author's first MyKnee patients, and thus early learning curve for this technique. IRB approval for retrospective research was obtained prior to the evaluation of the data.
Methods
30 consecutive patients (14 males, 16 females) underwent TKA using the MyKnee technique. Pre-operative long-standing radiographs were taken and compared to 6-week post-operative radiographs. Intraoperative data includes the femoral and tibial resections thickness: Distal Medial femoral, Distal Lateral femoral, Posterior Medial Femoral, Posterior Lateral femoral, Medial Tibia, and Lateral Tibia. These were compared to the Planned vs. Actual resections. Tourniquet time was recorded as a measure of speed of surgery. These were compared to 30 consecutive patients using Conventional TKA technique. Intraoperative complications were also recorded.
Background
Cemented femoral stems have an excellent long-term outcome. Modern cement techniques should be used to optimize femoral stem fixation. Bleeding from the bone surface during cemented hip arthroplasty compromises the bone-cement interface. However, no studies have examined this bleeding in vivo nor the effect the different cleaning methods used. In the present study we evaluated bleeding patterns and efficacy of cleaning methods used in third generation cementing techniques.
Methods
We prospectively performed a medulloscopy with a 10 mm laparoscope in 200 primary hip arthroplasties. Intramedullary bleeding was evaluated after femoral canal preparation and use of the different cleaning methods. The femoral canal was divided into three areas to facilitate comparison. The intramedullary bleeding was standardized on a four point scale. A non-parametric repeated measures ANOVA was used for statistical analysis.
Introduction
Increasing numbers and incidence rates of noisy (squeaking, scratching or clicking) ceramic-on-ceramic (CoC) total hip arthroplasties (THA) are being reported. The etiology seems to always involve stripe wear producing a stick-slip effect in the bearing which excites vibrations. As stripe wear is also found in silent CoC bearings, a theory has been developed that the vibrations become audible only via amplification through the vibrating stem. This was supported by showing that the excitation frequency and the resonance frequency of the plain stem are similar [1]. However, stem resonance in-vivo would be influenced by the periprosthetic bone damping and transmitting stem vibrations. Thus, if stem resonance is conditional for noisy COC hips, these should show periprosthetic bone different to silent hips.
This study compares stem fit&fill and periprosthetic bone between noisy and silent CoC hips.
Methods
In a consecutive series of 186 primary CoC hips with identical stems, cups (Stryker ABG-II) and femoral heads (Alumina V40, 28mm) a dedicated patient questionnaire [2] identified 38 noisy hips (incidence rate: 20.4%, squeakers: n=23). Stem fit&fill and cortical wall thickness (CWT, medial and lateral) were measured on post-op AP x-rays according to an established method [3, Fig 1]. Measurements were repeated by a single blinded observer in a control group of silent hips matched for gender, age, stem size and follow-up time (4.6yrs). Fit&fill and CWT were compared between the noisy and silent group at proximal, mid-stem and distal level and on the medial and lateral side.
Introduction
Patient satisfaction becomes an important aspect in clinical practice causing a shift from clinician-administered scales (CAS) towards patient-administered measurement outcomes (PROMs). Besides, clinical outcome can objectively be evaluated using inertia-based motion analysis (IMA). This study evaluates different outcome measures by investigating the 1) effect of replacing CAS by PROMS on outcome assessment, 2) redundancy between scales, 3) additional value of IMA in outcome scoring.
Methods
This cross-sectional study included 27 primary unilateral total knee arthroplasty patients (m/f=12/19; age=66.2 yrs), 6 weeks (n=12) and 6 months (n=15) postoperative, who covered a wide range of the scores. One CAS (Knee Society Score (KSS; knee and function subscore), two PROMs (Knee Injury and Osteoarthritis Outcome Score Physical Shortform (KOOS-PS), Visual Analogue Scale satisfaction (VAS)) and a functional test (IMA block step test) were completed. For IMA, patients stepped up and down a 20cm block starting with the affected and followed by the non-affected leg, while wearing an inertia-sensor (3D accelero- and gyrometer) at the lower back (fig. 1). IMA-parameters like performance time (s), bending angle (°), pelvic-obliquity angle (°), were calculated using self-designed algorithms. Differences between legs were determined by ratios (affected/non-affected leg). Pearson's correlations were done, considering r<0.4 poor, 0.4<r<0.7 moderate, r>0.7 strong.
Introduction
Computer aided surgery aims to improve surgical outcomes with image-based guidance. Navigated Freehand bone Cutting (NFC) takes this further by eliminating the need for cumbersome mechanical jigs. Multiple previous experiments on plastic and porcine bones, performed by surgeons with different level of expertise, suggested that the NFC technique was feasible. This study pushes NFC further by using the technique to perform complete total knee replacement (TKR) surgeries on cadavers (including implant cementing of tibia and femur).
Materials and Methods
A single surgeon performed a series of TKR surgeries on full cadaveric legs. Cruciate sacrificing implants were selected because these were considered more challenging for a freehand cutting approach due to the extra number and complexity of the cuts needed around a posterior stabilizing post recess when present.
A proprietary NFC prototype system was used, with real time graphics to indicate where/how to cut the bone without jigs. The system comprised a navigated smart oscillating saw, reciprocating saw and drill without any of the conventional jigs typically used in TKR.
The tasks performed included (and were grouped) to include pre-surgical planning, incision, placement of navigation pins & markers on tibia and femur, bone registration, marking and cutting, cut surface digitization (for quality assessment), implant placement and cementing, assessment of implant fit and location, and pin removal and wound closing.
Introduction
Conversion of immovable hip to a total hip arthroplasty provides a solution, improving function, reducing back and knee pain, and slowing degeneration of neighboring joints associated with hip dysfunction while the mobilization by total hip arthroplasty is rather uncommon and challenging surgery.
Materials and methods
Since 1998 we have performed 28 uncemented total hip arthroplasties for arthrodesed or ankylotic Hip. Among them 25 hips in 24 patients (four males and 20 females) with minimum of six months follow-up were evaluated. Thirteen hips were arthrodesed and twelve hips were ankylotic. One patient had arthrodesed hip in one side and ankylotic one in the other side. The mean age at the surgery was 63 (42 to 80). Two patients were Jehovah's witnesses. All 13 arthrodeses had been performed at other hospitals due to developmental dysplasia (11 hips), tuberculous coxitis (one hip), and infection after osteotomy (one hip). The underlying disease for the ankylosis was tuberculous coxitis for one hip and dysplastic osteoarthritis for 12 hips. Spongiosa Metal Cup (GHE, ESKA Orthodynamics AG, Lübeck, Germany) was used for 21 hips (screw fixation was added for two hips), Alloclassic Cup (Zimmer GmbH, Winterthur, Switherland) for one hip, Bicon Plus Cup (Smith & Nephew AG, Rotkreuz, Switherland) for one hip, and Müller's Reinforcement Ring (Zimmer GmbH, Winterthur, Switherland) for two hips. The bearing couple was ceramic on ceramic (Biolox forte, Ceramtec AG, Prochingen, Germany) for 14 hips, ceramic on polyethylene for eight hips, and metal on metal for three hips. Spongiosa Metal Stem (GHE, ESKA Orthodynamics AG, Lübeck, Germany) was used for 15 hips, SL Plus Stems (Smith & Nephew AG, Rotkreuz, Switherland) for nine hips, and Alloclassic Stem (Zimmer GmbH, Winterthur, Switherland) for one hip. All surgeries were carried out through an anterolateral approach. Twelve hips required the adductor tenotomy against the stiffness. The average follow-up period was 3.7 (0.5 to 10.6) years.
Commercial C-arm fluoroscopes are routinely used to analyze human skeletal joints during motions such as deep knee bends, or chair rises. Such diagnostics are used to characterize pre and post operative arthoplasty results, particularly in association with total joint replacement procedures. Stationary fluoroscopes restrict the patient motion and load conditions, thus diminishing the diagnostic utility of the results. A new class of fluoroscopy has been developed in which a robotic mechanization is used to allow selected joints to be x-rayed while the human subjects perform natural motions such as walking. The tracking fluoroscope system (TFS) is a mobile robot that acquires real-time x-ray records of hip, knee, or ankle joint motion while the patient walks normally. Because the fluoroscope line of sight dynamically tracks the joint of interest, the TFS provides clearer and contained joint images.
The technical features of the TFS will be reviewed, recent development testing summarized, and the results of preliminary patient trials presented.
Introduction
Shoulder motion results from a complex interaction between the interconnected segments of the shoulder girdle. Coordination is necessary for normal shoulder function and is achieved by synchronous and coordinated muscle activity. During rotational movements, the humeral head translates on the glenoid fossa in the anterior-posterior plane. Tension developed by the rotator cuff muscles compresses the humeral head into the glenoid fossa. This acts to limit the degree of humeral head translation and establishes a stable GH fulcrum about which the arm can be moved. Previous studies have been limited by the use of contrived movement protocols and muscular coordination has not been previously considered with regard to shoulder rotation movements. This study reports the activation profile and coordination of 13 muscles and 4 muscle groups during a dynamic rotational movement task based on activities of daily living.
Methods
Eleven healthy male volunteers were included in the study. Electromyography (EMG) was recorded from 13 muscles (10 surface and 3 fine-wire intramuscular electrodes) using a wireless EMG system. EMG was recorded during a movement task in which the shoulder was consecutively rotated internally (phase 1) and externally (phase 2) with a weight in the hand. Muscle group data was calculated by ensemble averaging the activity of the individual component muscles. Mean signal amplitude and Pearson correlation coefficient (PCC) analysed muscle activation and coordination, respectively.
Background
In a mobile-bearing unicondylar knee arthroplasty (UKA) stability is very important for the knee function and to prevent dislocation of the insert. A tension-guided technique to determine the position of the optimal posterior bone cut should theoretically lead to a better varus-valgus stability. The goal of this study was to measure the difference in valgus laxity in flexion and extension between a tension-guided and spacer-guided system for mobile-bearing UKA. Also clinical function was evaluated between the groups.
Patients and Methods
A tension-guided UKA system (BalanSysTM, Mathys, Bettlach, Switzerland) was compared with a retrospective group of a spacer-guided system (Oxford, Biomet Ltd, Bridgend, UK). A total of 30 tension-guided UKAs were placed and compared to 35 spacer-guided prostheses. Valgus laxity was measured at least 6 months postoperatively in both groups using stress radiographs. The flexion stress radiographs were made fluoroscopically aided in 70 degrees of knee flexion. Laxity measurements in extension were performed on stress radiographs obtained with the Telos device. Knee Society Scores (KSS) were obtained at follow-up.
Introduction
After total knee arthroplasty (TKA) with a PCL-retaining implant the location of the tibiofemoral contact point should be restored in order to obtain normal kinematics. The difficulty during surgery is to control this location since the position of the femur on the tibia cannot easily be measured from the back of the joint. Therefore, we developed a simple “spacer technique” to check the contact point indirectly in 90° flexion after all bone cuts are made by measuring the step-off between the distal cut of the femur and the anterior edge of the tibia with a spacer in place. The goal of this experiment was to investigate whether this new PCL balancing approach with the spacer technique created the correct contact point location.
Methods
Nine fresh-frozen full leg cadaver specimens were used. After native testing, prototype components of a new PCL-retaining implant were implanted using navigation and a bone-referenced technique. After finishing the bone cuts of tibia and femur, the spacer was inserted in flexion and positioned on the anterior edge of the bony surface to measure the step-off. If necessary, an extra cut was made to balance the PCL.
The specimen was mounted on the knee kinematics rig and a squat with constant vertical ankle force (130N) and constant medial and lateral hamstrings forces (50N) was performed between 30° and 130° of knee flexion. The trajectories of the reflective tibial and femoral markers were continuously recorded using six infrared cameras. The projections of the femoral condylar centers on the horizontal plane of the tibia were calculated and compared.
Purpose
Dysplastic acetabulum (DDH) have some difficulty even if with conventional approach of THA. Indication or contraindication is not clear with MIS THA. The purpose of this study was to evaluate complications with mini antero-lateral approach for DDH patients.
Materials & Methods
1523 DDH hips were evaluated. Follow-up periods were averaged 36 mos. (24–74). 612 were Crowe I, 628 of II, and 283 of III. Crowe IV hips were contra-indicated. Leg length discrepancy (LLD) before and after surgery, OR time, complications during and after surgery, and length of hospital stay were evaluated.
Purpose
Crowe IV complete dislocated hips were thought to be difficult for primary THA. Correction for leg length discrepancy associated with nerve palsy or tough to reduction during surgery. Purpose of this study was to evaluate 3.5cm total leg length correction for any type of Crowe IV patients setting in anatomical positioning of acetabular cup with femoral shortening osteotomy.
Materials & Methods
24 hips were evaluated averaged 28 months after primary THA. Correction length of center of rotation, amount of femoral shortening, Harris hip score, and abductor muscle power recovery with MicroFet 2 caluculator. Bilateral cases were preformed with 6 months interval. Length of femur and tibia compared to contralateral normal side were evaluated from plain radiograms.
The objective of this study is to determine the knee joint forces when rising from a kneeling position. We have developed a new type of knee prosthesis which is capable of attaining Japanese style sitting. To run the simulations and experiments needed to assess the performance of this prosthesis, it is necessary to know what forces act on the knee during deep flexion. Because these data are lacking, we created a 2D mathematical model of the lower leg to help determine knee joint forces during deep flexion. Healthy subjects of ten males (age of 25±4years, height of 170.3±9.1cm, and weight of 67.0±22.2kg) and five females (25±3years, 161±7.1cm, 47.7±6.2kg) participated in the experiment. Ground reaction force and joints angles were measured using a force plate and a motion recording system respectively. The collected data were entered into our mathematical model, and the muscle forces and the knee joint forces were calculated. To verify our model, we first used it to run simulation of middle and high flexions of the knee joint. In vivo data for these actions are available in the literature, and the results from our simulation were in good agreement with these data. We then collected the data and run simulation when rising from a kneeling position under the conditions shown in Fig. 1. They were a) double leg rising (both legs are aligned) without using the arms, b) ditto but using the arms, c) single leg rising (legs are in the front and the rear respectively) without using the arms, and d) ditto but using the arms. We obtained the following results. The statistics of the maximum values on the single knee joint for each condition were; a)
Introduction
Novel hydrogel implants, TRUFIT® bone plugs, have been developed by Smith & Nephew to replace worn-out cartilage surfaces, restoring mobility and relieving joint pain. There is limited information, however, on the biomechanical properties of the implants. Therefore, appropriate mechanical testing and modelling must be carried out to assess their mechanical properties for load bearing applications.
In this study, compressive properties of TRUFIT® bone and dual layer implants were examined under selected physiological loading conditions. The bone layer of the implant was also modelled using a biphasic poroviscoelastic (BPVE) material constitutive law and the results from the model are compared with those from the experiments.
Materials and Methods
TRUFIT® CB plugs, with diameters of 11 and 5mm, were sectioned to obtain single layer bone and dual layer samples, with an aspect ratio of 0.86. Specimens were tested in confined and unconfined compressions at two constant strain rates of 0.002/sec (walking) and 0.1/sec (impact) [1-3] on a MTS servo-hydraulic test machine equipped with a bionix envirobath. All samples were tested in phosphate buffered saline (PBS) solution at 37 °C. A preload of 0.1 MPa was applied and preconditioning (10 cycles of 0.008 strain) at a constant strain rate of 0.005 sec−1 [4] was used. The compressive modulus was calculated from the slope of the linear part of the stress-strain curve. In addition, whilst stress relaxation tests were performed on the bone samples in unconfined compression up to 5% strain, at a strain rate of 0.01/s (running) [1-2].
Metal-on-Metal devices generate significantly lower volumetric wear than conventional total hip replacements. However, clinically some patients may suffer some form of laxity in their joints leading to subluxation of the joint, which in turn may cause edge loading of an implant thereby increasing the chances of failure due to higher than expected wear.
In this study, the effect of subluxation on MoM implant wear was investigated on a hip joint simulator.
Materials & Methods
Two groups of 44 mm MoM devices were tested, n=3 in each group. The devices were subjected to 1 and 2 mm of subluxation. The flexion/extension was 30° and 15° respectively, internal/external rotation was ±10°, and cup inclination was 35°. The force was Paul type stance phase loading with a maximum load of 3 kN, with ISO swing phase load of 0.3 kN, run at 1 Hz.
The test was carried out on a ProSim deep flexion & subluxation hip wear simulator (SimSol, UK). Rather than separating the head and the cup (microseparation), or reducing the swing phase load, this simulator is equipped with a novel mechanism to achieve translation of the head, while subjecting the devices to subluxation. During the swing phase, a controlled lateral force necessary for the translation of the head is applied by a cam mechanism, head retraction will then take place on heel strike.
The lubricant used was new born calf serum with 0.2 wt. % sodium azide concentration diluted with de-ionised water to achieve average protein concentration of 20 g/l. Lubricant was changed every 250k cycles. Gravimetric wear measurements have been taken at 0.25 & 0.5 Mc stages.
Results
Tests conducted with 1mm (Group 1) and 2mm (Group 2) subluxation significantly increased volumetric wear compared to standard hip simulator tests [1]. At 0.5 million cycles, group 1 and 2 produced an average volume loss of 4.38±0.98 mm3 (95% CL) and 7.07±1.64 mm3 (95% CL) respectively.
Fast-track THA and TKA is a dynamic process combining clinical and logistical enhancements to ensure the best outcome for all patients regarding faster early functional recovery and reduced morbidity. Focus is on reducing convalescence by ensuring a smooth pathway with the best available clinical treatment from admission to discharge – and beyond. Main focus areas include pain treatment, mobilization, organizational aspects, traditions, and care principles. Outcome is typically evaluated as: a) length of stay in hospital (LOS), patient satisfaction, and reduced convalescence in the form of earlier achievement of functional milestones; b) safety aspects (reduced morbidity and mortality in the form of complications and readmissions in general and dislocations/manipulations in specific); c) feasibility (can the track be applied to other subgroups of patients, i.e. bilaterals or revisions?); and d) economic savings. Favorable outcomes regarding all these parameters have been documented for fast-track THA and TKA which has also resulted in the development of a Rapid Recovery Programme (Biomet).
LOS is now 1–2 days for unselected patients in leading departments with few readmissions, high patient satisfaction and economic savings. In Denmark, the nationwide median LOS is now 4 days and improved logistic features include homogeneous entities, regular staff, high level of continuity, preoperative information including intended LOS, admission on the day of surgery and functional discharge criteria. The improved clinical features include both intraoperative (spinal anesthesia, local infiltration analgesia (LIA), plans for fluid therapy, small standard incisions, no drains, compression bandages and cooling) and postoperative (deep venous thrombosis prophylaxis starting 6–8 hours postoperatively, multimodal opioid-sparing analgesia, early mobilization and discharge when functional criteria are met) facilitating early rehabilitation and discharge.
Future challenges include identification of high-pain responders to improve multimodal pain treatment; identification of high-risk patients regarding complications in fast-track set-ups; how to reduce postoperative cognitive dysfunction; how to reduce orthostatic intolerance; and when how and to whom to initiate and give rehabilitation.
Introduction
To obtain a better range of motion and to reduce the risk of dislocation, neck and cup anteversion are considered very important. Especially for the reduction of the risk of dislocation, the mutual alignment between neck and cup anteversion (combined anteversion) is often discussed. A surgeon would compare the neck direction to the calf direction with the knee in 90 degrees flexion. When an excessive anteversion was observed, the neck anteversion would be reduced using modular neck system or setting the stem a little twisted inside the canal with the tradeoff of the stem stability. Another choice would be the adjustment of cup alignment. Combined anteversion is defined the summation of cup anteversion in axial plane and stem anteversion in axial plane. But in realty the impingement occurs with 3 dimensional relationships between neck and cup with very complicated geometries. In that meaning, the definition of the angles could be said ambiguous too. The bowing of the femur also makes the relationships more complicated. Upon those backgrounds, we have been performing 3D preoperative planning for total hip arthroplasty on every case. In the present study, in vivo position of the stem in each case was determined then the anteversion observed on surgical view and anteversion around femoral mechanical axis are compared using 3D CAD software.
Materials and Methods
Ten recent cases from our hip arthroplasty with 3D preoperative planning were reviewed for this purpose. The bone geometries were obtained from CAT scans with very low X-ray dose using Mimics® (Materialize, Belgium). Preoperative planning for Revelation stem® (DJO, USA) was performed using Mimics® (Materialize, Belgium). Femoral mechanical axis was defined as a line between center of femoral head and the middle point of medial and lateral epicondyle of the femur. Then mechanical anteversion is assessed from posterior condylar line. On the other hand, the calf was rotated 90 degrees around epiconlylar axis of each femur, and in vivo stem position was estimated then, stem axis was aligned perpendicular to the view. The anteversion in the surgical view was assessed from that view as the angle toward the calf. (Fig. 1) Using in vivo stem alignment, the impingement angle was also assessed.
INTRODUCTION
Patellofemoral joint (PFJ) replacement is a successful treatment option for isolated patellofemoral osteoarthritis. With this approach only the involved joint compartment is replaced and the femoro-tibial joint remains intact. Minimizing periprosthetic bone loss, which may occur due to the stress shielding effect of the femoral component, is important to insure long-term outcomes. The objective of this study was to investigate, using finite element analyses, the effects of patellofemoral replacement on the expected stress distribution of the distal femur eventually leading to changes in bone density.
METHODS
MRI images of a healthy knee were acquired, segmented and reconstructed into a 3D physiological model of the bony and cartilaginous geometries of distal femur and patella with patellar tendon and insertion of the quadriceps tendon. This model was modified to include PFJ replacements with either a Journey PFJ or a Richards II PFJ prosthesis, and a Genesis II TKA (Smith&Nephew, Memphis, TN). The prosthetic components were incorporated in the intact model based on the manufacturer's instructions or previously described surgical techniques (Figure 1).
Cortical bone was modeled with orthotropic properties, while homogeneous linear isotropic elasticity was assumed for trabecular bone, cartilage, cement and femoral components materials. The patellar tendon was given Neo-Hookean behavior. UHMWPE patellar buttons for all designs were assigned non-linear elasto-plastic material.
The simulated motion consisted of a 10 second loaded squat, starting from 0° until a flexion angle of 120° matching experimental kinematics tests performed in previous in-vitro analysis on physiological cadaveric legs [1-2]. The patella model was constrained fixing the distal part of the patellar ligament and applying a quadriceps force distributed on the quadriceps insertion on the proximal surface of the patella.
During the dynamic simulation the average Von Mises stress was calculated in two regions of interest (ROI) defined in the femoral bone: one anterior and one proximal. The location of the ROIs was defined to fit the same regions as used in a previous bone mineral density analysis following patellofemoral arthroplasty (height 1cm, length 1cm).
Introduction
Alumina-on-alumina bearings exhibit low wear rates in vitro and one commonly used ceramic implant is the Trident system (Stryker, Mahwah, NJ). There are some reports of incomplete seating of the ceramic liner in the Trident acetabular shell. However, it is often difficult to detect incomplete seating intraoperatively. We sought to prevent incomplete seating using intraoperative radiography.
Materials and Methods
We retrospectively reviewed 19 hips in 17 patients who had undergone primary total hip arthroplasty using a Trident shell with a metal-backed alumina liner between 2007 and 2010. There were 16 women and 1 man, with an average age of 45.7 years. Preoperative diagnosis revealed 14 cases of osteoarthritis and 5 cases of osteonecrosis. All procedures were performed using a posterolateral approach with PSL cups. The minimum follow-up time was 12 months (average 28 months). All procedures included an intraoperative anteroposterior view radiograph to evaluate cup seating. If incomplete seating was recognized we reinserted the liner. Postoperatively, radiographs (supine anteroposterior and cross table lateral views) and computed tomography were performed in all cases in order to assess any residual incomplete seating. We investigated whether it was possible to avoid incomplete seating using intraoperative radiography.
Introduction
Minimally invasive, computer navigated techniques are gaining popularity for total knee replacement (TKA). While these techniques may have the potential to provide improved functional outcomes with more rapid recovery, little quantitative data exists comparing long-term gait function following surgery with different exposure approaches. This study compares functional gait differences between surgical approach groups two year following TKA. Kinetics, kinematics, and temporospatial parameters were assessed to determine if differences exist between groups in long term follow-up.
Methods
This study was approved by the Banner IRB (Sun Health Panel). 95 subjects volunteered to participate in the study and signed informed consent prior to testing. The subjects were prospectively randomized to one of four surgical approach groups, mini-midvastus (MV), mini-subvastus (SV), mini-parapatellar (MP), and standard parapatellar (SP). These subjects were also compared to 45 age-matched, asymptomatic controls. Surgery was performed by one of two fellowship trained orthopedic surgeons specializing in adult reconstruction. Subjects were assessed in the gait laboratory two years after receiving surgery. Three dimensional kinetic and kinematic data were captured using a ten-camera passive marker system, a modified Helen Hayes marker set (Eagle-4, Motion Analysis, Santa Rosa, CA), and four floor embedded force platforms (AMTI Inc., Watertown, MA). Subjects were instructed to walk at a self selected speed down an 8 meter walkway. Kinetic and kinematic data were post processed using EVaRT and OrthoTrak 6.23 biomechanical software (Motion Analysis, Santa Rosa, CA). Statistical analyses were performed using SPSS (v14.0, SPSS Inc, Chicago, IL) and included a one-way ANOVA and post hoc testing.
Introduction
The current standard of care for postoperative support during ambulation is a walker and accompanying gait belt. The use of a walker necessitates awkward body positioning, adequate upper body strength, and prohibits natural foot over foot progression during gait. Additionally, use of a gait belt necessitates that the therapist remains immediately beside or behind the patient, limiting the view of the patient's gait pattern and placing the therapist and patient at risk should the patient fall. The Secure Tracks™ (Fig 1) is a patient support device which runs in an overhead track and supports the patient in the periaxillary region, providing a more natural body position and foot progression while limiting the risk of falls. This prospective randomized study compares the rate of ambulation and other clinical outcomes measures in a population of total knee replacement recipients postoperatively.
Methods
A total of 31 unilateral total knee recipients were enrolled in this prospective randomized comparison between the standard of care gait training and the Secure Tracks device. IRB approval was obtained from the relevant oversight board. Patients were permitted to weight-bear as tolerated starting the evening of their surgical procedure. Patients were instructed to walk until they felt fatigued or unsafe and were not encouraged or discouraged to stop. The therapists tracked the distance each patient walked during each of their ambulation sessions and also recorded any incidence of falls or other adverse events. A timed up and go test (TUG) and Visual Analogue Scale for pain (VAS) were also administered at the time of consent, at discharge from the hospital, and at the 2 week clinic followup appointment.
Introduction
Precision Freehand Sculpting(PFS), is a hand-held semi-active robotic technology for bone shaping that works within the surgical navigation framework. PFS can alternate between two control modes – one based on control of exposure of the cutting bur (“Exposure Control”) and another based on the control of the speed of the cutting bur (“Speed Control”). In this study we evaluate the performance of PFS in preparing the femoral bone surface for unicondylar knee replacement (UKR).
Methods
The experiment is designed to prepare a synthetic bone for unicondylar knee replacement (UKR). The implant plan is mapped to individual specimen using a jig that fit in a unique and repeatable way to all specimens. During bone preparation, the PFS handpiece and the specimen are both tracked with the Polaris Spectra (Northern Digital Inc.) using passive reflective markers. The cutting plan is specified so that the specimens can receive a specially designed implant after the cut is finished. The implant is a modified commercial design with three planar back faces and two pegs. In addition there are 10 conical divots on the implant surface that can be used to register the implant after it is placed on the prepared bone surface. The distal and distal-anterior facets were cut with a 5 mm cylindrical bur using Extension Control. The posterior facet and the post holes were cut using 6 mm spherical bur using Speed Control.
Three subjects cut 5 specimens each. One subject was an experienced PFS user. The second user was somewhat less experienced, and the third user was completely inexperienced with the use of PFS. The performance was evaluated in terms of the implant fit and the performance time. The final implant fit was characterized using a MicroScribe MX desktop coordinate measuring arm.
Introduction
A new conservative hip stem has been designed to address the complex problem of total hip arthroplasty in the younger population.
Objectives
To assess the stability and strain distribution of a new conservative hip stem.
Surgical navigation in joint replacement has been developed for more than 10 years. After the initial enthusiastic period, it appears that few surgeons have included this technology into their routine practice. The reasons for this backflow are lack of evidence of any clinical superiority for navigation implanted prostheses, higher costs and longer operative time. However, navigation systems have evolved, and might still belong to the future of joint replacement.
Although most studies did not observe clinically relevant differences between navigated and conventional joint replacement, some registry studies identified significant advantages in favor of navigation: less blood loss, less early revision, subtle but relevant functional improvement… If TKR may be more forgiving, there is a trend to use less invasive implants (UKR), which are technically more demanding and may benefit from navigation. Ligamentous balancing may be more accurate and more reproducible with the help of navigation, and in that way patient specific templates may benefit from navigation. New techniques (short stem hip implants, hip resurfacing) have a relevant learning curve which may be fastened with navigation support.
Another key point may be the individual joint reconstruction: anatomy is different from one patient to the other, and navigation may help detecting these subtle differences to adapt a more physiological joint reconstruction, instead reconstructing all joints on the same model.
New navigation systems now available are designed in a more user-friendly style, with more straightforward workflow, and may be adapted to every surgeon's need.
Finally, navigation system may act as documentation and quality control system for health care providers, as well as a very powerful research tool for scientists and manufacturers.
INTRODUCTION
Unicompartmental knee arthroplasty (UKA) allows replacement of a single compartment in patients who have isolated osteoarthritis as a minimally invasive procedure. However, limited visualization of the surgical site provides challenges in ensuring accurate alignment and placement of the prosthesis.
With robot-assisted surgery, correct implant positioning and ligament balancing are obtainable with increased accuracy. To date, there has not been a large series reported in the literature of UKAs performed with robotic assistance. The aim of this study was to examine the clinical outcomes of robot-assisted UKA patients.
METHODS
510 patients who underwent robotic-assisted UKA between July 2008 and June 2010 were identified (average age 63.7 years, range: 22 to 28 years). Clinical outcomes were evaluated using the Oxford Knee Score (OKS) and patients without recent follow-up were phoned. Revision rate and time to revision were also examined.
Introduction
Total hip prostheses which use a ceramic head within a metal liner are a relatively recent innovation. As such, survivorship rates from independent centres alongside explant analysis are rare. The early clinical experience with this novel ceramic-on-metal (CoM) bearing couple is reported alongside explant analysis of failed devices.
Methods and materials
All CoM hips implanted between 2008 and 2009 at a single hospital by a single surgeon were reviewed. Radiographs were analysed using EBRA software to determine acetabular cup inclination and anteversion angles. Blood metal ion concentrations were measured using inductively coupled plasma mass spectroscopy (ICPMS). Explants were measured for bearing surface and taper wear using a high precision co-ordinate measuring machine (Mitutoyo Legex 322, manufacturer's claimed accuracy 0.8µm). The roughness of the articulating surfaces of heads and liners was measured with a non-contact profilometer (ZYGO NewView 5000, 1nm resolution).
Introduction
This study was performed to evaluate the minimum 5-year clinical and radiological results of liner cementation into a stable acetabular shell using a metal-inlay, polyethylene liner during revision total hip arthroplasty (THA).
Methods
Sixty-six hips (63 patients) that underwent revision THA using a metal-inlay polyethylene liner cementation were included. The causes of revision were; polyethylene wear in 37 cases, femoral stem loosening in 20 cases, ceramic head fracture in 4 cases, and recurrent dislocation in 5 cases. Clinical results were graded at final follow-up using Harris hip scores, and radiographs were evaluated to determine acetabular component inclination, the stabilities of acetabular and femoral components, correction of hip centers, and the progression of osteolysis.
Introduction
Ion analysis has been used as one of the key indicators to assess the performance of MoM devices in patients. Modular devices, in particular having larger overall surface area (the stem and sleeve), and locking interfaces (head – bore, sleeve- taper and sleeve-bore, stem-taper surfaces) than other MoM devices are expected to release greater number of ions. Concerns have been expressed that the ion release at the taper junction might be a potential cause leading to the failure of the implant [Garbuz
The aim of this study was to look into the wear and the associated ion release from the taper junction and the articulating surface of modular devices.
Method
For the first time a novel design has been used to isolate the taper junction on modular devices on the hip simulators in order to compare the wear at the taper junction and articulating surface. The taper junction has been isolated in a small gaiter, while the head and cup were contained in a large gaiter. CoCrMo sleeves having an offset of +8 mm have been used on 50 mm modular heads along with Ti6Al4V stems. The acetabular components were standard BHR cups. Three devices (Smith & Nephew, UK) have been tested with newborn calf serum as a lubricant (in the large gaiter) and also as the medium containing the taper junction (in the small gaiter). The serum samples from the articulating surface and taper junction were analysed using HR-ICPMS. The locking interfaces at the taper junction have been left intact throughout the duration of the test. Both the head and the cup have been tested under anatomical conditions using the standard implant development centre's (IDC) profile for 2 million cycles (Mc). The lubricant was newborn calf serum with 0.2% sodium azide diluted with de-ionised water to achieve protein concentration of 20 mg/ml. The flexion/extension was 30°/15° and the internal/external rotation was ±10°. The force was Paul-type stance phase loading with a maximum load of 3 kN and a standard ISO swing phase load of 0.3 kN. The frequency was 1 Hz, with an 8 hour stop after every 16 hours of testing.
Introduction
Total hip arthroplasty (THA) using the direct anterior approach (DAA) in a supine position is a minimally invasive surgery that reduces postoperative dislocation. Excellent exposure of both the acetabulum and proximal femoral part is important to reduce intraoperative complications. Generally, two surgical assistants need to hold four retractors to maintain excellent exposure of the acetabulum. We examined intra- and postoperative complications as indicators of the efficiency of using the “Magic Tower” (MT) device compared with a non-MT group.
Material and Method
Twenty consecutive DAA THAs using MT were analyzed, and 20 DAA THAs not using MT were also analyzed. MT is a retractor-holding device, and has an arm structure that can be moved in a wide variety of directions. This device holds a retractor stably, and each movement of the arm can be locked by one click. Operating time, blood loss, length of skin incision, intraoperative complications, and number of assistants were recorded. Postoperative radiographs were obtained to evaluate implant position.
Introduction
Alignment and positioning of implants is important in total knee arthroplasty (TKA). Identifying the femoral hip center (FHC) without fluoroscopy or computer navigation is considered difficult. The Complete Compass system (CoCo) is a femoral extramedullary guidance system designed to identify the FHC. This apparatus provides an accurate representation of the femoral functional axis in the coronal plane without a computer navigation system. We compared postoperative implant alignment of patients undergoing total knee arthroplasty between CoCo and intraoperative computer navigation.
Materials and Methods
Twenty-five consecutive TKAs using CoCo were analyzed. CoCo has a pivotal arm with a pivotal shaft arranged to extend perpendicular to the coronal plane. A marker is attached to the pivotal arm to depict a circular arc on the marking plate with rotation of the pivotal arm. The pivotal shaft is placed at the intercondylar notch of the femur. The distance from the pivotal shaft to the marker is equal to the distance from the intercondylar notch of the femur to the FHC of the patient based on preoperative measurements in the coronal plane. This apparatus has a level of the horizontal plane and the condition of the pivotal shaft is able to match neutral positions in the sagittal and axial planes. The intersection of two arcs drawn by using CoCo with the hip joint in abduction and adduction indicates the FHC position. Postoperative coronal and sagittal views radiographs were obtained. Twenty-five TKAs implanted using computer navigation were also analyzed for postoperative alignment. For two groups, targeted implant position was 90° in both planes for the femoral functional axis.
Introduction
Some authors have reported that if PCL is resected, flexion gap(FG) will become wider than extension gap(EG). Sacrifice or sparing of PCL influences the equality of EG and FG. Meanwhile, measured resection technique(MRT) and gap technique(GT) has different system to adjust gap and balance. There are no criteria for choosing between CR or PS component and MRT or GT nevertheless its influences on gap and balance in TKA.
Materials and Methods
EG and FG were measured intra-operatively with PCL intact to assess the characteristics of EG and FG. EG was created ordinarily. To measure FG before the final femoral cutting with PCL intact, small temporary FG was created by a pre-cut of the femoral posterior condyle with a 4-in-1 femoral cutting guide bigger than the measured size. After removal of all osteophytes, the gaps were measured by a tension device. To compare both gaps, FG was corrected by the amount of the pre-cut. According to EG and corrected FG, a component type was selected. If there was enough FG with PCL intact, CR component was implanted and if not, PS component was selected. If necessary, soft tissue was released. Finally, the optimal size of the femoral component for adequate EG and FG was estimated and rotation of the femoral component was decided. One hundred and fifty three knees with osteoarthritis were investigated.
Objectives
All Polyethylene Tibial components in Total Knee Arthroplasty have been in use for some years, studies showing equivalent results to Total Knee Arthroplasty (TKA) with metal-backed Tibial components at 10 years have shown no significant difference between the two on radiostereometric analysis and revision rates[1].
Post operative patient outcome data using standard metal-backed Tibial components is widely reported in the literature. This study is looking at patient outcomes following All-polyethylene tibial component TKA. We hypothesize that using standard patient outcome measures, an improvement comparable with that expected for metal-backed tibial component TKA will be shown with All-polyethylene tibial component TKA.
Methods
Between August 2006 and August 2008, 229 all-polyethylene tibial component TKA were implanted at the elective orthopedic unit. The choice of implant was entirely dependent on surgeon's preference.
Of the 229 patient's, 225 details were available for review, 27 did not wish to take part in the study and 1 patient died a year following surgery of an unrelated illness. The remaining 197 patients agreed to take part in the study.
The patient's were contacted either in person or over the telephone and asked to completed questionnaires for standard knee scoring.
These included: the Oxford Knee Score (OKS), the WOMAC Score and the SF-12 Score, both pre-operatively and post operatively.
Introduction
The advantages of the direct anterior approach (DAA) for total hip arthroplasty include the preservation of external rotators and hip abductors thus leading to quicker recovery times. To our knowledge, there is no objective method in the literature to predict the level of difficulty for femoral exposure through the DAA. It would be beneficial to the surgeon learning the DAA to assess difficulty pre-operatively to avoid prolonged operative times. The purpose of this study was to develop a predictive model of femoral exposure difficulty in the DAA using a combination of demographic data and radiographic measurements.
Methods
305 post-operative radiographs of consecutive THA's in patients (184 female, 120 male) with primary or secondary osteoarthritis, mean age 64.6 (range 26–91, SD=11.43) performed through the DAA by one of the co-investigators from 12/2005 to 12/2009 were retrospectively reviewed by two separate observers. The observers were blinded to the difficulty level of femoral exposure. Standard post-operative AP pelvis films were assessed with TraumaCad software (TraumaCad 2.2, Voyant Health, Columbia, MD) to make radiographic measurements as shown in Figure 1–2. Each radiograph was calibrated using the size of the femoral head implant. Exclusion criteria included films that had inadequate coverage of the entire pelvis, mal-rotation, or poor exposure. Statistical analysis was performed using STAT 9.1 (StatCorp; College Station, Texas, USA). A two-sided Kruskal–Wallis test was utilized for non-parametric data. Chi-squared tests and Fisher's Exact Test were used to compare proportions. Statistically significant associations were then added to a multivariate model predicting an outcome of difficult exposure.
INTRODUCTION
Electron-beam-irradiated
MATERIALS & METHODS
Both pure UHMWPE and Vitamin E added (0.3% w/w) resin was used to produce bulk specimens via vacuum direct compression molding at 220°C under 25 MPa for 30 min. Cylindrical pins (3.5 mm diameter, 40 mm length) for ESR measurement were then machined and placed in vacuum packaging. The pins were irradiated at 300 kGy, with half of each test group annealed at 80°C for 24 hours. Free radical measurements were made using a high-sensitive X-band ESR operating at 9.44 GHz. Detection of Vitamin E radicals was performed by comparing the characteristic symmetrical spectrum of oxidized Vitamin E to the spectra observed for the pins using both g-value and linewidth as references. Crosslink density was measured via gel fraction analysis and was performed in accordance with ASTM D2765. Thin sections (20 × 40 mm2, 200 μm) were machined from the bulk specimens, which were then placed in vacuum packaging, irradiated and annealed at the same conditions as those for the ESR measurements. Two of these thin sections were then placed in a stainless-steel cage (200 µm pore diameter) and were immersed in decahydronaphtalene at 200°C for 24 hours. These specimens were then extracted using soxhlet extractor at 100°C for 24 hours and dried in vacuum at 150°C for 12 hours.
INTRODUCTION
For cementless TKA, highly crosslinked UHWMPE is traditionally used with modular components because of manufacturing and sterilization complexities of monoblock metal-backed components. However, it would be very useful to have a highly crosslinked UHMWPE monoblock metal-backed cementless component to address historical clinical issues. The purpose of this study was to evaluate the wear properties of a unique process for achieving a monoblock metal-backed cementless component featuring highly crosslinked polyethylene to standard highly crosslinked UHWMPE.
MATERIALS AND METHODS
The knee system used for testing consisted of cobalt chrome femoral components and tibial trays (Triathlon®, Stryker Orthopaedics, Mahwah, NJ). Modular tibial inserts were machined from GUR 1020 polyethylene that was irradiated to 30 kGy and annealed three times (Modular, n=5) (X3, Stryker Orthopaedics, Mahwah, NJ). Monoblock tibias were direct compression molded to a metal substrate and then irradiated to 30 kGy and annealed three times. For the purposes of this test, the polyethylene was removed from the monoblock component and machined into a standard tibial insert (Monoblock, n=5).
A 6-station knee simulator was utilized for testing (MTS, Eden Prairie, MN). All motion and loading was computer controlled and waveforms followed ISO 14243-3 [1]. Testing was conducted at a frequency of 1 Hz for 3 million cycles. The lubricant used was Alpha Calf Fraction serum (Hyclone Labs, Logan, UT) diluted to 50% with a pH-balanced 20-mMole solution of deionized water and EDTA [2]. The serum solution was replaced and inserts were weighed for gravimetric wear at least every 0.5 million cycles. Standard test protocols were used for cleaning, weighing and assessing the wear loss of the tibial inserts [3]. Soak control specimens were used to correct for fluid absorption with weight loss data converted to volumetric data (by material density). Statistical analysis was performed using the Student's t-test with significance determined at the 95% confidence level (p < 0.05).
INTRODUCTION
Wear and fracture of patellar components has been frequently reported as a failure mode for cemented and press-fit patellar components. Malalignment of the patellar components may cause higher contact stresses, which may lead to excessive wear, delamination, and/or component fracture.
MATERIALS AND METHODS
A 6 station MTS (Eden Prairie, MN) knee joint wear simulator and Alpha Calf Fraction serum (Hyclone Labs, Logan, UT) diluted to 50% with a pH-balanced 20-mMole solution of deionized water and EDTA was used (protein level = 20 g/l) for testing. Asymmetric, all-polyethylene, patellar components with an overall construct thickness of 11 mm (Duracon®, Stryker Orthopaedics, Mahwah, NJ) were used. Appropriately sized cobalt-chrome femoral components articulated against the patellae.
The patellae were cemented (Simplex, Stryker Orthopaedics, Mahwah, NJ) to delrin fixtures, which placed the patella in 10° of lateral tilt (Figure 1). This angle was chosen based off the work of Huang et al, which was one of the larger average tilt angles reported
The loading and kinematic profiles used for testing were published previously (maximum axial load: 2450N and maximum patellofemoral angle: 54°. Variations of the loading profile were studied by evaluating the effects of heavier patients, which increased the maximum axial load to 3100N(250lb patient) and 3750N(300lb patient) (Figure 2). Lateral offset was tested to evaluate the effect of malalignment. Increments of 1mm were analyzed starting from the neutral position, eventually reaching a maximum lateral offset of 5mm.
A 6-dof load cell was placed beneath the patella fixturing to capture dynamic loads (ATI, Apex, NC). The axial and medial/lateral shear loads where used to calculate the resultant medial/lateral shear force being applied to the patellar pegs.
Introduction
Ceramic femoral heads have proven to be more scratch resistant with better wettability and improved wear characteristics compared to metal heads in the laboratory setting. The objective of this study was to compare long-term survivorship and in vivo wear rates of ceramic and metal femoral heads against conventional polyethylene articulation in young patients.
Materials and Methods
Thirty-one matched pair of alumina and metal femoral heads against conventional polyethylene in young patients (≤ 65 years) were analyzed for wear and failures for mechanical reasons. The match was based on gender and age at the time of surgery. All procedures were performed between June 1989 and May 1992 by a single surgeon via posterolateral approach, using non-cemented RB (Ranawat-Bernstein) stems, HG II (Harris-Galante) cups, 4150 conventional polyethylene and 28mm femoral heads.
Hospital for Special Surgery (HSS) hip score was used for clinical analysis. Wear measurements were performed between the initial anteroposterior standing pelvis radiographs, at a minimum of one year after the index procedure to eliminate the effect of bedding-in period, and the latest follow-up. Two independent observers analyzed polyethylene wear rates using the computer-assisted Roman 1.70 software. In revision cases, the wear rates were calculated from radiographs prior to revision surgery. A pair student t test was performed to analyze the statistical difference. Two-tailed ρ values less than 0.05 were considered statistically significant.
Introduction
The optimal goal for cup positioning in hip arthroplasty in individual patients is affected by many factors including surgical exposure, femoral anteversion, and pelvic tilt. Some navigation systems ignore pelvic tilt and are based strictly on the anterior pelvic plane while others incorporate pelvic tilt, as measured in the supine position on the operating table. Neither approach incorporates knowledge of preoperative spino-pelvic flexibility or predictions of the change in spino-pelvic attitude or flexibility following surgery. While prior studies have shown little change in pelvic tilt postoperatively, one recent study based on gait analysis, suggested that changes in pelvic tilt are not predictable. The current study aims to assess changes in pelvic tilt following surgery.
Methods
24 patients, 12 male and 12 female, underwent THA using CT-based navigation. Each patient had supine and standing AP pelvis radiographs both pre-operatively and at a minimum of 1 year post-operatively. Pelvic tilt on each radiograph was measured using a noncommercial two-dimensional/three-dimensional matching application. (HipMatch; Institut for Surgical Technology and Biomechanics, Bern, Switzerland). This software application uses a fully auto- mated registration procedure that can match the three- dimensional model of the preoperative CT with the projected pelvis on a postoperative radiograph. This method has been validated and for measurement of cup position for example showed a mean accuracy of 1.7° +/− 1.7° (rang-4.6° to 5.5°) in the coronal plane and 0.9° +/− 2.8° (rang-5.2° to 5.7°) in the sagittal plane compared with postoperative CT measurements. The software showed a good consistency with an intraclass correlation coefficient (ICC) for inclination of 0.96 (95% confidence interval [CI]: 0.93 to 0.98) and for anteversion of 0.95 (95% CI: 0.91 to 0.98). A good reproducibility and reliability for both inclination and anteversion was found with an ICC ranging from 0.95 to 0.99. No systematic errors in accuracy were detected with the Bland- Altman analysis. Using the HipMatch 2D/3D application, changes in pelvic tilt before and after surgery were assess in both the supine and standing positions.
Introduction
Robotic-guided arthroplasty procedures are becoming increasingly common, though to our knowledge there are no published studies on robotic cutting guides in TKA. We introduced a new computer-navigated TKA system with a robotic cutting-guide into a community-based hospital and characterized the accuracy and efficiency of the technique with respect to bone cutting, component alignment and final limb alignment, and tourniquet time.
Methods
The first 100 cases from a single-surgeon were retrospectively reviewed following IRB approval. Intra-operative bone-cut accuracy and overall limb alignment as measured by the computer were collected and divided into consecutive quartiles: Group I, cases 1–25; Group II, cases 26–50; Group III, cases 51–74; Group IV, cases 75–100. All resections were planned neutral to the mechanical axis. Postoperative component alignment and the overall mechanical axis limb alignment in the coronal plane were also measured on standing long-leg AP radiographs by two independent observers at a minimum six weeks post-op. This mechanical radiographic alignment was available for 62 cases. Tourniquet time (the time prior to incision until after cementation) and robotic cutting guide use time were also analyzed.
INTRODUCTION
Multiple video fluoroscopic analyses have been performed to determine the in vivo kinematic patterns of total knee arthroplasty (TKA) and non implanted knees. Unfortunately, many of these studies were not correlated with bearing surface forces and possible failure modes that could be detected with a sound sensor. Therefore, the objective of the present study was to conduct a comparative analysis of the kinematic data derived for all subjects having a TKA who were analyzed over the past seventeen years at our laboratory and to determine how these patterns correlate with bearing surface forces and joint sound.
METHODS
Initially, femorotibial contact positions and axial rotation magnitudes were derived for subjects having either a non implanted or implanted knee. Non implanted knees consisted of normal and anterior cruciate ligament (ACL) deficient knees (ACLD). Implanted knees consisted of posterior stabilized (PS) fixed (PSF) and mobile (PSM) bearing, posterior cruciate ligament retaining (PCR) fixed (PCRF) and mobile (PCRM) bearing, posterior cruciate sacrificing mobile (PCSM) bearing and ACL retaining fixed (ACRF) bearing TKA. Each subject, while under fluoroscopic surveillance, performed a weight-bearing deep knee bend and/or normal gait. Using a three-dimensional (3D) model fitting approach, the relative pose of knee implant components were determined in 3D from a single-perspective fluoroscopic image by manipulating a CAD model in three-dimensional space. Anterior/posterior (A/P) contact positions for both the medial and lateral condyles and axial rotation of the femoral component relative to the tibial component were assessed. Then, a subset of these subjects were further analyzed to determine their in vivo bearing surface forces and joint sound using a more recently derived protocol for analyzing audible signals.
Introduction
Failure of total knee arthroplasty (TKA) is mainly caused by biological reactions against wear particles generated at the implant. So far, wear has been mainly attributed to polyethylene (PE) and much effort has been put into understanding and optimizing the wear mechanism of PE in recent years. However, evaluation of metal wear particles and ion release in TKR has been neglected so far although the implants present large metal surface areas. In the present study we aimed to analyse the wear performance of TKA and to study the kinetics of metal ion and particle release. We hypnotized that due to abrasion and corrosion TKA will release relevant levels of Cobalt (Co), Chromium (Cr), Molybdenum (Mo) and Titanium (Ti).
Methods
Implants were subjected to an in-vitro simulation applying physiological loadings and motions for 5 million walking cycles. Wear processes were determined gravimetrically and by measuring the release of Co, Cr, Mo and Ti ions using HR-ICP-MS. Surface alterations were determined through surface roughness measurements.
Introduction
The anterior approach to primary total hip arthroplasty is an unfamiliar approach to most surgeons that is considered to be minimally invasive based on the premise that there is less soft tissue damage and quicker post-operative recovery time. We present our experience of using the anterior approach exclusively by a single surgeon at multiple surgical centers for a period of 3.5 years.
Method
709 consecutive patients undergoing primary hip arthroplasties from 8/2007 to 12/2010 through a direct anterior approach were performed by single surgeon with extensive training in the approach. The procedure was performed with the patient supine on a fracture table (Trumph arch table extension) through an anterior approach as described by Dr. Joel Matta through a Smith-Peterson interval. Intra-operative data and complications were collected prospectively and to avoid missing any complications, electronic medical records (Alteer) were retrospectively reviewed.
Introduction
Malrotation of the femoral component is a cause of patellofemoral maltracking after TKA. Its precise effect on the patellofemoral (PF) mechanics has not been well quantified. The aim of this study was to investigate the effect of malrotation of the femoral component on PF initial contact area, initial contact pressure and wear after 4 million full gait cycles in TKA using a knee simulator. Moreover, the influence of the counterface material (CoCr or OxZr) on PF wear was also investigated.
Materials & Methods
Femoral components (FCs) were cemented onto specially designed fixtures, allowing positioning of the FC in different angles of axial rotation. Patellar buttons and FCs were then mounted in a Prosim knee simulator.
Introduction
Optimal knee joint function obviously requires a delicate balance between the osseous anatomy and the surrounding soft tissues, which is distorted in the case of joint line elevation (JLE). Although several studies have found no correlation between JLE and outcome, others have linked JLE to inferior results. The purpose of this in vitro investigation was to evaluate the effect of JLE on tibiofemoral kinematics and collateral ligament strains.
Materials and Methods
Six cadaver knees were equipped with reflective markers on femur and tibia and CT scans were made. A total knee arthroplasty (TKA) was performed preserving the native joint level. The knees were then tested in passive flexion-extension and squatting in a knee kinematics simulator while marker positions were recorded with an optical system. During squatting quadriceps forces were measured as well as tibio-femoral contact pressures. Finally, a revision TKA was performed with JLE by 4 mm. The femoral component was downsized and a thicker insert was used. The knees were again tested as before.
Based on the bony landmarks identified in the CT scans and the measured trajectories of the markers, relative tibiofemoral kinematics could be calculated as well as distance changes between insertions of the collateral ligaments.
Statistical tests were carried out to detect significant differences in kinematic patterns, ligaments elongation, tibiofemoral contact pressures and quadriceps forces between the primary TKA and after JLE.
INTRODUCTION
Glenosphere disengagement can be a potential serious default in reverse shoulder arthroplasty [1]. To ensure a good clinical outcome, it is important for the surgeon to obtain an optimal assembly of the glenosphere - base plate system during surgery. However interpositioning of material particles (bone, soft tissue) between the contact surface of the glenosphere and the base plate and/or a misalignment of the glenosphere relative to the base plate can result in a suboptimal assembly of the glenosphere – base plate system [2]. This misalignment is typically caused by unwanted contact between the glenosphere and the scapula due to inadequate reaming. Both defects prevent the Morse taper from fully engaging, leading to a system configuration for which the assembly was not designed to be loaded in vivo. This study quantifies the influence these defects have on the relative movement between the glenosphere and metaglene.
MATERIALS AND METHODS
A biaxial test setup [Fig. 1] was developed to mechanically load the glenoidal assembly (base plate + glenosphere) of 5 Depuy® Delta Xtend 38 prostheses. The setup allows applying a cyclic loading pattern to the glenoidal component with a constant actuator load of 750 N. Each of the 5 samples was tested for 5000 cycles on 3 defects: an interpositioning of 150 µm thick (0.48 mm3) and two local underreaming defects, pushing one side of the glenosphere up 0.5 mm and 1 mm respectively, hence causing a misalignment. The relative movement was recorded using 4 Linear Variable Differential Transducers (LVDTs). The cycling frequency is 1 Hz.
Traditional instrumentation relies on rigid IM rods to determine the distal femoral resection which influences size and orientation of the femoral component. Anterior femoral bowing may unexpectedly affect implant sizing. The purpose of this study was to determine the sensitivity of a flexible rod to the femoral anterior bow versus a traditional rod.
A database of 93 Asian bone models from CT images was utilized. The bones were subdivided into those having proximal third, distal third, or overall femoral bows. Only the latter group was selected for further analysis, which consisted of 54 with an average bow of 98cm (±20cm). The rigid and flexible rods were placed iteratively so that the proximal portion of the rod touched the anterior cortical-cancellous boundary and no portion of the rod protruded through that boundary. The flexible rod was allowed to flex, as a substantially thin central portion flexes exclusively in the sagittal plane. The relative angle difference between the position of the flexible and rigid rod were calculated.
Three femura were chosen from the subset with bows of 123cm, 100cm and 78cm. The femura showed differences between the rigid and flexible rod of 7.5°, 4.5° while no significant angle measured for the smallest bow. Implants were virtually assembled onto the bones and the greatest bowed femur's component reduced one size from the rigid to the flexible rod orientation.
The results of this study show that higher bowed femura yielded larger angular deviations between rigid and flexible rods. For higher bowed femura, the flexible rod allows smaller components to be implanted. The flexible rod serves the same purpose as a conventional rod by defining the distal valgus orientation but allows component orientation in the sagittal plane closer to the femoral bow.
Introduction
Several in vitro and in vivo studies have found correspondence between transepicondylar axis (TEA) and functional flexion axis (FFA) in healthy subjects. In addition some studies suggest that the use of FFA for rotational alignment of femoral implant may be more accurate than TEA. Ostheoarthritis (OA) may modify limb alignment and therefore flexion axis, introducing a bias at different flexion ranges during kinematic acquisition. In this study we want to understand whether OA affects somehow the FFA evaluation compared to TEA and whether the FFA could be considered a usable reference for implant positioning for osteoarthritic knees
Methods
We included a group of 111 patients undergoing TKA. With a navigation system, we recorded intraoperative kinematic data in three different ranges of motion (0°-120°; 35°-80°; 35°-120°). We compared the difference in orientation of FFA (computed with the mean helical axis method) in the three ranges as also the difference with the TEA on frontal and axial planes. The correlation of preoperative limb deformity with FFA and TEA was also performed.
Metal-on-metal hip resurfacing prostheses are a relatively recent intervention for relieving the symptoms of common musculoskeletal diseases such as osteoarthritis. While some short term clinical studies have offered positive results, in a minority of cases there is a recognised issue of femoral fracture, which commonly occurs in the first few months following the operation. This problem has been explained by a surgeon's learning curve and notching of the femur but, to date, studies of explanted early fracture components have been limited.
Tribological analysis was carried out on fourteen retrieved femoral components of which twelve were revised after femoral fracture and two for avascular necrosis (AVN). Eight samples were Durom (Zimmer, Indiana, USA) devices and six were Articular Surface Replacements (ASR, DePuy, Leeds, United Kingdom). One AVN retrieval was a Durom, the other an ASR. The mean time to fracture was 3.4 months. The AVNs were retrieved after 16 months (Durom) and 38 months (ASR).
Volumetric wear rates were determined using a Mitutoyo Legex 322 co-ordinate measuring machine (scanning accuracy within 1 micron) and a bespoke computer program. The method was validated against gravimetric calculations for volumetric wear using a sample femoral head that was artificially worn in vitro. At 5mm3, 10mm3, and 15mm3 of material removal, the method was accurate to within 0.5mm3. Surface roughness data was collected using a Zygo NewView500 interferometer (resolution 1nm).
Mean wear rates of 17.74mm3/year were measured from the fracture components. Wear rates for the AVN retrievals were 0.43mm3/year and 3.45mm3/year. Mean roughness values of the fracture retrievals (PV = 0.754, RMS = 0.027) were similar to the AVNs (PV = 0.621, RMS = 0.030), though the AVNs had been in vivo for significantly longer.
Theoretical lubrication calculations were carried out which found that in both AVN retrievals and in seven of the twelve cases of femoral fracture the roughening was sufficient to change the lubrication regime from fluid film to mixed. Three of these surfaces were bordering on the boundary lubrication regime. The results show that even before the femoral fracture, wear rates and roughness values were high and the implants were performing poorly.
Introduction
Post traumatic arthritis of the knee can be a conseguence of distal femur fracture and retained hardware can complicate any further surgical option including arthroplasty. Both staged surgical procedures to remove before the hardware or simultaneous procedure of arthroplasty and removal of hardware have been indicated with an increased risk of complications. Aim of this study is to present a consecutive series of TKA following distal femur fracture using a computer assisted technique without the removal of retained hardware assessing both the efficacy of navigation in managing these complex cases as “routinary” primary arthroplasties.
Material and Methods
A consecutive series of 16 patients treated with a computer assisted TKR following femoral fracture and with retained hardware were included in the study (group A). The interval between the fracture and operation averaged 5.8 years (range 1–12 years), the retained hardwares was an intramedullary nail in 6 cases, distal lateral plates in 7 cases and screws in 4 cases. All patients in group A were matched with a patient who had undergone to a computer assisted TKR using the same implant and software because of atraumatic knee arthritis in the same period (group B). Patients were matched in terms of age, gender, pre-operative range of motion, pre-operative arthritis severity according to Albaack classification, type and grade of deformity and implant features (cruciate retaining or sacrificing). There were 10 male and 6 female for each group, the mean pre-operative age was 64.3 years (range: 54–72) for the group A and 65.4 years (range: 53–74) for the group B. The mean pre-operative flexion was 85.5 degrees (range: 65–115) and 88.1 degrees (range: 70–115) for the post traumatic group and the matched group respectively.
Introduction
Readmission after Total Hip Arthroplasty (THA) or Total Knee Arthroplasty (TKA) places a great burden on the health care system. As reimbursement systems place increased emphasis on quality measures such as readmission rates, identifying and understanding the most common drivers for readmission becomes increasingly important.
Methods
We queried an electronic database for all patients who underwent THA or TKA at our institution from 2006 through 2010. We identified those who were readmitted within 90 days of discharge from the initial admission and set this as our outcome variable. We then reviewed demographic and clinical data such as age, index procedure, length of stay (LOS), readmission diagnosis, co-morbidities and payer group and set these as our variables of interest. We used chi-square tests to characterize and summarize the patient data and logistic regression analyses to predict the relative likelihood of patient readmission based on our control variables. Statistical significance was defined as p <0.05.
BACKGROUND
Our modified procedure for rotational acetabular osteotomy (RAO) aimed to reduce operative invasion of soft tissue and to minimize incision length.
SURGICAL TECHNIQUE
A shortened skin incision (10–15 cm versus 20–30 cm in traditional RAO) is curved over greater trochanter and exposed by transtrochanteric approach. Medial gluteus muscle is retracted to expose the ilium without detachment from iliac crest. Similarly the rectus femoris muscle tendon was retracted, not excised, from the anterior inferior iliac spine. The lateral part of the osteotomized ilium is cut in lunate and trapezoid shape to form the bone graft instead of the outer cortical bone of the ilium.
INTRODUCTION
Total shoulder arthroplasty (TSA) implants are used to restore function to individuals whose shoulder motions are impaired by osteoarthritis. To improve TSA implant designs, it is crucial to understand the kinematics of healthy, osteoarthritic (OA), and post-TSA shoulders. Hence, this study will determine in vivo kinematic trends of the glenohumeral joints of healthy, OA, and post-TSA shoulders.
Methods
In vivo shoulder kinematics were determined pre and post-operatively for five unilateral TSA subjects with one healthy and a contralateral OA glenohumeral joint. Fluoroscopic examinations were performed for all three shoulder categories (healthy, OA, and post-TSA) for each subject shoulder abduction and external rotation. Then, three-dimensional (3D) models of the left and right scapula and humerus were constructed using CT scans. For post-operative shoulders, 3D computer-aided design models of the implants were obtained. Next, the 3D glenohumeral joint kinematics were determined using a previously published 3D to 2D registration technique. After determining kinematics, relative Euler rotation angles between the humerus and scapula were calculated in MATLAB® to determine range of motion (ROM) and kinematic profiles for all three shoulder categories. The ROMs for each category were compared using paired t-tests for each exercise.
Also, the location of the contact point of the humerus on the glenoid was found. This allowed the vertical translation from the most superior to most inferior contact point (SI contact range) to be calculated as well as the horizontal translation from the most anterior to most posterior contact point (AP contact range). The SI and AP contact ranges for all shoulder categories were compared using paired t-tests for each exercise.
Orthopaedic companies spend years and millions of dollars developing and verifying new total knee arthroplasty (TKA) designs. Recently, computational models have been used in the hopes of increasing the efficiency of the design process. The most popular predictive models simulate a cadaveric rig. Simulations of these rigs, although useful, do not predict in vivo behavior. Therefore, in this current study, the development of a physiological forward solution, or predictive, rigid body model of the knee is described.
The models simulate a non-weight bearing extension activity or a weight-bearing deep knee bend (DKB) activity. They solve for both joint forces and kinematics simultaneously and were developed from the ground up. The models are rigid body and use Kane's dynamical equations. The model began with a simple two dimensional non-weight bearing extension activity model of the tibiofemoral joint. Step by step the model was expanded. Quadriceps and hamstring muscles were added to drive the motion. Ligaments were added represented by multiple non-linear spring elements. The model was expanded to three-dimensions (3D) allowing out of plane motions and calculation of medial and lateral condylar forces. The patella was added as its own body allowing for simulation of the patellofemoral joint. The model was then converted to a weight bearing deep knee bend activity. A pelvis and trunk were added and muscles were given physiological origin and insertion points. A modified proportional-integral-derivative (PID) controller was implemented to control the rate of flexion and also to assist in joint stability by adjusting the force in individual quadriceps muscles. A method for representing articulating geometry was developed. Once the deep knee bend model was fully developed (Figure 1) it was converted back to a non-weight bearing extension model (Figure 2) resulting in simulations of a normal knee performing a weight bearing and non-weight bearing activity. The tibiofemoral kinematic results were compared to in vivo kinematics obtained from a fluoroscopy study of five normal subjects. Parameters from the CT models of one of these subjects (Subject 3) were used in the model.
The model kinematics behave as the normal knee does in vivo. The kinetic results were within reasonable ranges with a maximum total quadriceps force of 0.86 BW and 4.73 BW for extension and DKB simulations, respectively (Figure 3 and Figure 4). The maximum total tibiofemoral forces were 1.26 BW and 3.70 BW for extension and DKB, respectively. The relationship between the quadriceps force, patella ligament force and patellofemoral forces are consistent with how the extensor mechanism behaves (Figure 3 and Figure 4). The patellofemoral forces are low between 0 and 20 degrees flexion and the patella ligament and quadriceps forces are close in magnitude from 0 to around 70 degrees flexion when the patellofemoral forces increase and the quadriceps forces increase relative to the patella ligament force. The model allows for virtual implantation of TKA geometry and after kinematic and kinetic validation from in vivo TKA data can be used to predict the behavior of TKA in vivo.
Over the past decade, there has been an increase in the number of total knee arthropalsty (TKA). Demand of TKA for the young patients who often have high physical demands is also increasing. However, the revision rate in such young patients is much higher due to polyethylene (PE) wear and instability (Julin J, Acta Orthop 2010). Therefore, next generation total knee prostheses are expected to decrease PE wear and to provide stability.
Although
Patients who underwent bilateral staged TKAs were more likely to prefer medial pivot prosthesis or ACL-PCL retaining prosthesis than the other types of prostheses, because they feels “more stable overall” (Pritchett JW, J Arthroplasty 2011).
The excellent mid-term clinical results of those newly introduced total knee prosthesis, such as alumina medial pivot TKA (Iida T, ORS 2008), medial pivot TKA (Mannan K, JBJS Br 2009, Kakachalions T, Knee 2009), ACL-PCL retaining TKA (Clouter JM, JBJS Am 1999), and highly cross-linked PE (Hodrick JT, CORR 2008), have been reported.
From the point of view of
Introduction
Anterior cervical decompression and fusion (ACDF) is considered a standard surgical treatment to degenerative discogenic diseases. Lately, the question arises whether or not ACDF significantly influences the progression of adjacent disc degeneration (ADD). The etiology of ADD is obscure and it has not been fully understood whether ADD is a consequence of fusion or it represents the aging pathway of the degenerative cervical process, thus making it a controversial topic [1-3]. There have been several discussions about the possibility of ACDF altering biomechanical conditions at adjacent segments, therefore resulting in increased load and excessive motion [3,4]. The purpose of this study was to compare the cervical segmental motion pre- and post-ACDF using novel 3D analytical techniques.
Methods
Nine patients (2F/7M, mean age: 54.1 years, range 36–76 y.o.) underwent ACDF due to symptomatic cervical degenerative discogenic disease. One-level ACDF was performed in 4 patients, whereas 2-level ACDF was done in five, using cylindrical titanium porous cage implants. Pre- and post (postoperative periods ranged from 11-months, 25 days to 12-months, 22 days, mean postoperative period: 12.09 months) surgery, dynamic-CT examinations were conducted in neutral, flexion and extension positions. Subject-based 3D CT models were created for segmental motion analysis (Fig. 1). Six-degrees-of-freedom 3D segmental movements were analyzed using a validated Volume-Merge methods (accuracy: 0.1 mm in translation, 0.2°in rotation) [5]. The segmental translation was evaluated by the segmental translations of gravity centers of endplates (Fig. 2). Disc-height distribution was measured using a custom-written Visual C++ routine implementing a lease-distance calculation algorithm. The mean translation distance was calculated for the each adjacent level (Fig. 2). Differences of segmental motions and mean disc height between pre- and post-surgery at each level were compared by the Wilcoxon signed rank test. Results were presented mean±SEM.
INTRODUCTION
Prosthetic joint related-infections (PJRI) are severe complications in orthopaedic surgery.
MATERIAL AND METHODS
35 staphylococcal strains
Summary
Single use instrumentation had a significant reduction on OR Turnover time and instrument setup/clean up time compared to traditional instrumentation.
Introduction
Recently, focus has shifted to improving OR efficiency by surgeons and hospital admin. The purpose of this study was to determine the effect of traditional instrumentation vs. single use instrumentation (SUI) on OR efficiency in navigated primary TKA.
A functional total knee replacement has to be well aligned, which implies that it should lie along the mechanical axis and in the correct axial and rotational planes. Incorrect alignment will lead to abnormal wear, early mechanical loosening, and patellofemoral problems. There has been increased interest of late in total knee arthroplasty with robot assistance. This study was conducted to determine if robot-assisted total knee arthroplasty is superior to the conventional surgical method with regard to the precision of implant positioning.
Twenty knee replacements of ten robot-assisted and another ten conventional operations were performed on ten cadavers. Two experienced surgeons performed the surgery. Both procedures were undertaken by one surgeon on each cadaver. The choice of which was to be done first was randomized. After the implantation of the prosthesis, the mechanical-axis deviation, femoral coronal angle, tibial coronal angle, femoral sagittal angle, tibial sagittal angle, and femoral rotational alignment were measured via three-dimensional CT scanning. These variants were then compared with the preoperative planned values.
In the robot-assisted surgery, the mechanical-axis deviation ranged from −1.94 to 2.13° (mean: −0.21°), the femoral coronal angle ranged from 88.08 to 90.99° (mean: 89.81°), the tibial coronal angle ranged from 89.01 to 92.36° (mean: 90.42°), the tibial sagittal angle ranged from 81.72 to 86.24° (mean: 83.20°), and the femoral rotational alignment ranged from 0.02 to 1.15° (mean: 0.52°) in relation to the transepicondylar axis. In the conventional surgery, the mechanical-axis deviation ranged from −3.19 to 3.84°(mean: −0.48°), the femoral coronal angle ranged from 88.36 to 92.29° (mean: 90.50°), the tibial coronal angle ranged from 88.15 to 91.51° (mean: 89.83°), the tibial sagittal angle ranged from 80.06 to 87.34° (mean: 84.50°), and the femoral rotational alignment ranged from 0.32 to 4.13° (mean: 2.76°) in relation to the transepicondylar axis. In the conventional surgery, there were two cases of outlier outside the range of 3° varus or valgus of the mechanical-axis deviation. The robot-assisted surgery showed significantly superior femoral-rotational-alignment results compared with the conventional surgery (p=0.006). There was no statistically significant difference between robot-assisted and conventional total knee arthroplasty in the other variants. All the variants were measured with high intraobserver and interobserver reliability.
In conclusion, Robot-assisted total knee arthroplasty showed excellent precision in the sagittal and coronal planes of the three-dimensional CT. Especially, better accuracy in femoral rotational alignment was shown in the robot-assisted surgery than in the conventional surgery despite the fact that the surgeons who performed the operation were more experienced and familiar with the conventional surgery than with robot-assisted surgery. It can thus be concluded that robot-assisted total knee arthroplasty is superior to the conventional total knee arthroplasty.
Head sizes used in total hip arthroplasty (THA) has increased drastically from the original 22mm used by Charnley. This is due to two factors: the use of hard-on-hard materials for the bearing articulation and the increasing problem of dislocation.
The tribological aspect
Hard-on-hard materials enable mixed or fluid film lubrication due to their good wettability. The development of a fluid film layer is encouraged by smaller surface pressures (larger area) and higher velocity at the articulating interface (larger radius), suggesting that larger diameters exhibit better lubrication and such less wear. This was effectivly proven in pre-clinical simulator studies and used as argument to increase the diameters of metal-on-metall and ceramic-on-ceramic bearings. Clinically the tribological advantage of larger diameters has not yet been shown. For hard-on-soft bearings the situation is different. Due to the bad wettability of Polyethylene (PE), the abrasive wear regime is dominant. This means that the longer wear path of a larger diameter will inevitably carry a larger amount of wear debris. Despite this relation, the heads used in combination with PE were also increased up to 40mm diameter, justified by the overall greatly reduced wear amount of the new generation(s) of cross-linked PE and favourable simulator results. First in-vivo studies have shown that larger heads carry larger amounts of wear particles. Whether this increase is relevant with respect to osteolysis is still unclear and will have to be shown in longer term studies.
The biomechanical aspect
Larger heads require a larger “jumping” distance until they dislocate. Consequently the use of larger heads reduces dislocation rates, which was shown in multiple clinical studies. However, the reduction in dislocation rate achieved by increasing diameters varies greatly. Some centres achieve dislocation rates below 1% with 28mm heads, other centres require 36mm heads to achieve the same result. No study shows any further advantage with head diameters larger than 36mm. Despite their obvious biomechanical advantage with regard to stability, larger heads also have large disadvantages. Larger heads carry inevitably larger friction moments, requiring better anchoring of the components. In unfavourable conditions (start-up, break-down of lubrication film), friction moments of hard-on-hard bearings can get very high and reach or even exceed the losening torque of the head on the taper. Depending on the head impaction foce during assembly, the loosening torques amount to 8 to 17Nm. Movement at the head-taper connection possibly causes wear and increased corrosion at this interface. Larger head diameters also require thinner shells and/or liners, leading to problems with liner chipping or incomplete seating. Large head diameters have also lead to the use of sub-hemispherical cups with reduced covering surface, increasing the risk of fluid film break down due to edge loading if not well positioned. Finally, larger heads might give the surgeon a wrong feeling of security regarding a sub-optimal positioned cup.
The question regarding “the optimal” head diameter is open for discussion and needs to consider the bearing material used. Head size should be limited to a reasonable compromise, which based on the information currently available, could be 36mm. Join the “36 and under” club.
Navigation has shown to improve limb and component alignment during total knee arthroplasty (TKA). However, most navigation systems involve bulky and expensive hardware, increased operative time and cost. A novel hand-held image-free navigation device has been recently approved with the aim to reduce inventory, cost and surgical time with its small size and quick registration features. We aimed to determine limb and component alignment and validate the accuracy of the iPod based navigation system.
Intraoperative navigation data for proximal tibia and distal femur cuts, femoral component rotation, limb alignment and component alignment in routine imageless navigation system (Ci Navigation, Brainlab) was compared with the novel iPod-based hand-held navigation system (DASH, Smith & Nephew) in 20 TKAs. Postoperative full-length hip-to-ankle and lateral radiographs were evaluated to measure the hip-knee-ankle (HKA) angle and coronal and sagittal alignment of the femoral and tibial component.
The iPod-based navigation system showed good agreement with the Ci Navigation system for limb alignment, tibial and distal femoral cuts in the majority of the limbs despite its quick registration feature. The iPod-based system is hence a positive step towards making navigation systems for TKA more compact, user-friendly, time and cost-effective.
There is ample data to confirm that Computer-assisted total knee replacement improves alignment of the limb when compared with the conventional technique. There is also published evidence that optimum alignment correlates with longevity of implants. CAS enables accurate component alignment of both femoral and tibial components. It enables accurate restoration of the posterior tibial slope which has important consequences for flexion range and stability of the component in flexion especially if mobile bearing implants are considered. CAS also aids in correctly orienting rotation of the femoral component; this has value in minimizing patellar maltracking. We will present our data showing accurate restoration of joint line and posterior femoral offset. As CAS ensures alignment, rotation, sizing and positioning of components, the surgeon is free to devote his efforts to ensuring soft-tissue balance and stability, since TKA is really a ‘soft-tissue’ operation.
How CAS is of immense value in deformity correction and soft-tissue balancing will be illustrated with examples. It helps in better understanding and quantification of the effects of soft-tissue release on flexion-extension gaps and this is of great value not only for minimal deformities (to minimise releases) but also for severe deformities (to ensure complete correction by adequate release). CAS is invaluable in helping equalize flexion-extension gaps; how it can help balance the flexion gap to the extension gap by ‘virtual surgery’ will be depicted with examples. It is particularly useful in presence of hardware in the femur or tibia and for concomitant extra-articular deformity.
We have also found a consistent improvement in recovery of functional milestones with CAS with similar results for both unilateral and bilateral TKAs. Furthermore, there is evidence to support that ensuring alignment has important benefits in improving functional and quality of life scores. In addition, those with alignment of mechanical axis within 3 degrees of normal have been shown to have a shorter stay in hospital by 2 days. Studies have shown reduced blood loss and incidence of emboli after CAS TKA.
Using CAS routinely for all cases, the author is ‘time neutral’. While there is always room for improvement with evolving technologies and CAS is no exception, it already has enormous benefits in the performance and outcome of TKA, and is an important part of the surgical armamentarium for a successful knee arthroplasty.
Introduction
Achieving high flexion after total knee arthroplasty is very important for patients in Asian countries where deep flexion activities are an important part of daily life. The Bi-Surface Total Knee System (Japan Medical Material, Kyoto, Japan), which has a unique ball-and-socket mechanism in the mid-posterior portion of the femoral and tibial components, was designed to improve deep knee flexion and long-term durability after total knee arthroplasty (Figure 1). The purpose of this study was to determine the in vivo three dimensional kinematics of Bi-Surface Total Knee System in order to evaluate and analyze the performance of this system with other conventional TKA designs currently available in the market today.
Materials and Methods
Three dimensional kinematics were evaluated during a weight-bearing deep knee bend activity using fluoroscopy and a 2D-to-3D registration technique for 66 TKA. Each knee was analyzed to determine femorotibial kinematics, including weight-bearing range of motion, anterior/posterior contact position, and tibio-femoral rotation.
It is very important to fix implant to bone. Bioactive materials as hydroxyapatite or glass-ceramics have bone-bonding ability. Hydroxyapatite-coating is applied to cementless THA or TKA. I and coworkers investigated bone-bonding mechanism of bioactive material and found that bone-like apatite formation play key role for bonding. If the surface of metal is changed to form apatite on it in body, the inert metal changes into bone-bonding material. We developed alkaline and heat treatment of titanium to change titanium to bone –bonding material as follows. At first, titanium is dipped in 5N NaOH solution for 24 hours, at second the metal is washed in pure water and finally it is sintered in 500 degree C for 2 hours. The treated surface has bioactivity, bone bonding ability like hydroxyapatite. The advantage of this treatment over hydroxyapatite-coating procedure is to treat the porous surface without any change of pore figures. As to hydroxyapatite-coating procedure, pore of the small diameter is filled with hydroxyapatite and pore figures are change. We applied this alkaline and heat treatment to cementless THA and its good results of more than ten years was reported.
Porous titanium can be changed to bioactive material by alkaline and heat treatment. This bioactive porous titanium was found to have a property of material-induced osteoinduction, that is, the bone formation in pore of porous titanium implanted in canine back muscle. They can be used for bone substitute for big bone defect. We used two procedures to make porous titanium, sintering of titanium powder with spacer particle of ammonium sulfate and selective lazar melting. The latter procedure can produce any type of pore structure of titanium. Selective laser melting was employed to fabricate porous Ti implants (diameter 3.3 mm, length 15 mm) with a channel structure comprising four longitudinal square channels, representing pores, of different diagonal widths, 500, 600, 900, and 1200 micrometer. These were then subjected to chemical and heat treatments to induce bioactivity. Significant osteoinduction was observed in widths 500 and 600 micrometer, with the highest observed osteoinduction occurring at 5 mm from the end of the implants. A distance of 5 mm probably provides a favorable balance between blood circulation and fluid movement.
New bioactive bone cement is another topic of the application of bioactive titanium in this lecture. The bone cement contains barium sulphate for radiocontrast. We developed a procedure to replace barium sulphate with bioactive titanium powder. This new bone cement has not only better biocompatibility than conventional cement but also bone bonding ability. It is potent material for the fixation of implant to bone. I will speak the evaluation of this cement using canine model of THA.
Background
Calcium phosphate cement (CPC) is a promising biomaterial which can be used in numerous medical procedures for bone tissue repairing because of its excellent osteoconductivity. An injectable preparation and relatively short consolidation time are particularly useful characteristics of CPC. However, the low strength of CPC and its brittleness restrict its use. One method for toughening brittle CPC is to incorporate fibrous materials into its matrix to create a composite structure. Fibers are widely used to reinforce matrix materials in a variety of areas.
Objective
We hypothesized that there must be an optimal fiber length and structure which can balance these conflicting aspects of fiber reinforcement. The purpose of this study is to prove our conjectures that adding a small amount of short fibers significantly improves the hardness and the toughness of CPC while maintaining its injectability with a syringe and that fiber morphologies that have crimps and surface roughness are favorable for reinforcing.
Purpose
There are concerns of soft-tissue reactions such as metal hypersensitivity or pseudotumors for metal-on-metal (MoM) bearings in hip arthroplasty, however, such reactions around ceramic or polyethylene bearings are incompletely understood. The present study was conducted to examine the capabilities of ultrasound screening and to compare the prevalence of periarticular soft-tissue lesions among various types of bearings.
Methods
Ultrasound examinations were conducted in 163 hips (153 patients) with arthroplasty after mean a follow-up of 8.1 years (range, 1–22 years). This included 39 MoM hip resurfacings (M-HR) including 30 Birmingham hip resurfacings (BHR) and 9 ADEPT resurfacings; 36 MoM total hip arthroplasties (M-THA) with a large femoral head including 26 BHR and 10 ADEPT bearings; 21 ceramic-on-ceramic THAs (C-THA) of Biolox forte alumina bearings; 24 THAs with a conventional polyethylene liner (cPE-THA) including 19 Lubeck and 5 Omnifit systems; and 43 THAs with a highly cross-linked polyethylene liner (hxPE-THA) including 28 Crossfire and 15 Longevity liners. All procedures were performed in the lateral position through the posterior approach without trochanteric osteotomy. The M-HR group had a significantly higher frequency of male patients than the C-THA, cPE-THA, and hxPE-THA groups, and the patients in the M-HR group were younger than those in the other four groups. Ultrasound images were acquired as a still picture and in video format as the hip moved in flexion and rotation, and 4 qualitative classifications for periarticular soft-tissue reactions were determined as normal pattern, joint-expansion pattern (marked hypoechoic space between the anterior capsule and the anterior surface of the femoral component), cystic pattern (irregularly shaped hypoechoic lesions), and mass pattern (a large mass extending anterior to the femoral component). Magnetic resonance imaging (MRI) was subsequently performed in 45 hips with high-frequency encoding bandwidths. For the reliability of ultrasound screening, positive predictive value, negative predictive value, and the accuracy of the presence of abnormal patterns on ultrasound were calculated using the abnormal lesions on MRI as a reference.
Purpose
Ceramic-on-ceramic bearings in total hip arthroplasty (CoC THA) have theoretical advantages of wear resistance and favorable biocompatibility of ceramic particles to the surrounding bony and soft tissue. Long-time durability of CoC THA has been expected, however, clinical results over 10 years after operation were scarcely reported. In the present study, clinical results at follow of 10 years were examined for CoC THAs with a changeable femoral neck which allowed correction of anteversion of the femoral component in cases with abnormal femoral anteversion in dysplastic hips.
Methods
During 1997 and 2000, 203 cementless CoC THAs in 158 patients were conducted in our hospital. Six patients died because of unrelated causes and 5 patients were lost to followup, and the remaining 188 hips in 147 patients were analyzed at the mean followup period of 10.8 years (3.7 to 13.5). There were 24 men and 123 women, and the average age at operation was 54 years (26 to 73). The hip diseases for operation were osteoarthritis in 165 hips, osteonecrosis of the femoral head in 21 hips and failure of hemiarthroplasty in 2 hips. The operation was performed in the lateral position through the posterior approach without trochanteric osteotomy. The articulation was composed of Biolox forte alumina liner fitted into beads-coated hiemispherical titanium shell, and a 28-mm Biolox forte alumina femoral head (Cremascoli). The femoral component was either AnCA stem or custom-designed stem, coupled with a modular neck allowing selection of 5 variable offsets and anteversions (Cremascoli). Clinical and radiological findings, and complications during the followup period were analyzed.
Introduction
The new Knee Society Score has been developed and validated, in part, to characterize better the expectations, components of satisfaction, and the physical activities of the younger, more diverse modern population of TKA patients. This study aims to reveal patients' activity levels' post-TKA and to determine how it contributes to their subjective evaluation of the surgery.
Methods
As part of a multi-centered and regionally diverse study sponsored by the Knee Society, the new Knee Society Score (KSS) was administered 243 patients (44% male; avg 66.4years; 56% female, avg 67.7years) following primary TKA (follow up > 1year, avg. 25mos). The new, validated KSS questionnaire consists of a traditional objective component, as well as subjective components inquiring into patient symptoms, satisfaction, expectations and activity levels as well as a survey of three physical activities that are viewed as important to the patients. Responses were analyzed as a whole group and as subgroups of male and female and as younger (<65) and older (>65).
Introduction
Knee prostheses retrieved at revision often show patterns and severity of damage neither seen nor predicted from standard wear simulator testing. We hypothesized that this is because these implants are exposed to combinations of loads and motions that are more damaging than the simple loading profiles utilized in laboratory testing. We examined the magnitude, direction, and combination of forces and moments acting on the knee during various activities in order to guide the future development and testing of high-performance knee replacements.
Methods
In vivo data from five patients with instrumented tibial implants were obtained from an open database (www.orthoload.com). We determined the direction and magnitude of forces and moments that the knee experiences during the following common physiologic activities: stair descent, stair ascent, deep knee bend, one leg stance, and walking. In order to capture the loading pattern, we investigated the three component forces and moments acting on the knee at several high demand points for each of these activities. The e-tibia data were compared to the loading profiles used in conventional laboratory testing (ISO 14243-1).
Statement of Purpose
Meniscal tears are common knee injuries that subsequently lead to degenerative arthritis, attributed to changes in stress distribution in the knee. In such cases there is need to protect the articular cartilage by repairing or replacing the menisci. While traditionally, meniscal replacement involves implantation of allografts, problems related to availability, size matching, cost and risk of disease transmission limit their use. Another optional treatment is that of biodegradable scaffolds which are based principally on tissue engineering concepts. The variability in body response to biodegradable implants and the quality of the tissue formed still pose a problem in this respect, under intense knee loading conditions. Moreover, biological solutions are mostly limited to younger patients <40 years old. Therefore, the goal of this study was, to develop a synthetic meniscal implant which can replace the injured meniscus, restore its function, and relieve pain.
Methods
A composite, non-fixed self-centering discoid-shaped meniscus implant (NUsurafce®, AIC, Memphis, TN), composed of polycarbonate-urethane (PCU) and reinforced circumferentially with UHMWPE fibers is proposed (Fig. 1). The implant geometry was based on an extensive MRI study of over 100 knee scans [1]. The proposed structure aims to mimic the circumferential collagen reinforcement of the natural meniscus. Biomechanical evaluation of the implant was focused on in-vitro measurements of contact pressure under the implant in cadaver knees and computational finite element (FE) analyses [2,3]. Pressure distribution on the tibial plateau (under the meniscus implant) was measured by pressure sensitive films (Tekscan, MA) and quantified with respect to the natural meniscus. FE analyses were used to evaluate internal stress and strains, and to support the selection of optimal implant configuration. The last pre-clinical step was a large-animal (sheep) study in which the cartilage condition was evaluated microscopically over six months [4].
Introduction
Metal-on-polycarbonate urethane (MPU) is a cutting-edge new bearing technology for hip arthroplasty. The acetabular component consists of a 2.7mm-thick polycarbonate-urethane liner inserted into a specially manufactured uncemented titanium shell coated with hydroxyapatite [(HA) Fig. 1]. The liner is pliable and biomechanically mimics human cartilage. In vitro studies have shown minimal wear, fluid film lubrication, physiological load transmission and shock absorption capacity equal to the normal hip. This system includes prosthetic heads of a diameter 12mm less than the socket diameter. The aim of this study was to clinically assess patients treated with this novel technology in a retrospective single centre study.
Methods
Twenty-seven patients with osteoarthritis treated with MPU bearing arthroplasty were included. Mean patient age was 67.9±10.35 years (44–84). Sixteen patients were female and 11 were male. Twenty-four of these had an uncemented HA-coated stem while 3 had a hip resurfacing metal femoral component. All patients were operated on by a single surgeon using a postero-lateral approach.
The various disorders of the patellofemoral joint, from pain syndrome to maltracking and arthritis, form a significant subset of knee disorders (Callaghan and Selfe 2007). Several studies have shown significant geography and gender based variation in incidence rates of these disorders and of osteoarthritis in general (Woolf 2003). A number of previous studies have examined patellar shape in this context, focusing primarily on the use of 2D measurements of bony geometry to classify patellar shapes and identify high-risk groups (Baumgartl 1964; Ficat 1970).
Recent developments in imaging and statistical analysis have enabled a more sophisticated approach, characterised by statistical shape models which account for three dimensional shape differences (Bryan 2008). Incorporating soft tissue data into these analyses, however, has been a challenge due to factors including the necessity of multi-modality images, absence of repeatable landmarks, and complexity of the surfaces involved. We present here a novel method which has potential to significantly improve analysis of soft tissue geometry in joints. It is built using Arthron, a UCD-developed biomechanics analysis software package.
The shape modelling process consists of three phases: pre-processing, consistent surface parameterization, and statistical shape analysis. The pre-processing phase consists of several mesh processing operations that prepare the input surfaces for shape modelling. Consistent surface parameterizations are implemented using the minimum description length (MDL) correspondence method (Davies 2002) [Fig. 1]. The statistical shape analysis phase involves the reporting and visualization of geometric variation at the input surface. An algorithm was developed to measure the cartilage thickness at each node on the patellar surface mesh. The initial step in this process was to calculate surface normal vectors at each point. These vectors were then projected through the cartilage surface model in order to calculate the thickness [Fig. 2]. The Matlab software was used to aggregate all cartilage thickness values in a given subgroup and after being normalised for the average patellar centroid size for the subgroup, these thicknesses were visualised on the average shape.
Pilot study data consisted of 19 Caucasian (7 female, 12 male) and 13 Japanese (7 female, 6 male) subjects. These data originated from studies performed by DePuy Orthopaedics Inc. Initial results show ethnicity effects in cartilage thickness to be more significant than gender effects [Fig. 3]. After correcting for patellar centroid size, male subjects display 9% greater average thickness than female subjects, while Caucasian subjects display 17% greater average thickness than Asian subjects. Areas of statistically significant differences (t < 0.05) were found to coincide with expected areas of patellofemoral contact through the flexion cycle, showing the potential for the thickness differential to impact upon patellar kinematics. Principal component analysis of the thickness distributions gives more detailed information about modes of variation.
With further development, this method has potential to enable sophisticated analysis of localised variation in soft tissue geometry, thereby improving understanding of the impact of joint geometry on disease formation.
Background
Short stem has potential advantages of bone and muscle preservation. Current papers demonstrate that direct anterior approach (DAA) is a significant minimally invasive muscle-sparing approach to total hip arthroplasty. Theoretically, a short length stem with a reduced lateral shoulder is the most appropriate design for DAA.
Objectives
To clarify the necessity of the standard length stem in tapered-wedge stem.
Introductions
In cruciate-retaining total knee arthroplasty (TKA), among many factors influencing post-operative outcome, increasing the tibial slope has been considered as one of the beneficial factors to gain deep flexion because of leading more consistent femoral rollback and avoiding direct impingement of the insert against the posterior femur. In contrast, whether increasing the tibial slope is useful or not is controversial in posterior-stabilized (PS) TKA, Under such recognition, accurate soft tissue balancing is also essential surgical intervention for acquisition of successful postoperative outcomes in TKA. In order to permit soft tissue balancing under more physiological conditions during TKAs, we developed an offset type tensor to obtain soft tissue balancing throughout the range of motion with reduced patello-femoral(PF) and aligned tibiofemoral joints and have reported the relationship between intra-operative soft tissue balance and flexion angles. In this study, we therefore assessed the relationship between intra-operative soft tissue balance assessed using the tensor and the tibial slope in PS TKA.
Materials and methods
Thirty patients aged with a mean 72.6 years were operated PS TKA(NexGen LPS-Flex, Zimmer, Inc. Warsaw, IN) for the varus type osteoarthritis. Following each bony resection and soft tissue release using measure resection technique, the tensor was fixed to the proximal tibia and femoral trial prosthesis was fitted. Assessment of the joint component gap (mm) and the ligament balance in varus (°)was carried out at 0, 10, 45, 90and 135degrees of knee flexion. The joint distraction force was set at 40lbs. Joint component gap change values during 10-0°,45-0°, 90-0°, 135-0° flexion angle were also calculated. The tibial slopes were measured by postoperative lateral radiograph. The correlation between the tibial slope and values of soft tissue balance were assessed using linear regression analysis.
Remarkable strides made in medical technology and techniques of total knee arthroplasty over past 5 years. These changes have included: minimally invasive surgical techniques, pain management, navigation, kinematic design of prosthesis and recently custom fitted surgical guides based on the anatomic axis. To date, there has been little documentation of the use of these custom-cutting surgical guides.
There has been significant controversy as to the necessity of using the neutral alignment of the mechanical axis for this surgery for a long lived replacement. A recent study by Pagnano et al in 2008 demonstrated that it could not be confirmed that improvement in the mechanical axis to zero would lead to a long-term improvement in survivorship, and it was noted that there was actually a slight trend for the outliers to be more successful. A recent study (Three-Dimensional Morphology and Kinematics of the Distal Part of the Femur Viewed in Virtual Reality Eckhoff et al, JBJS 2005) provides kinematic and morphologic validation for a single cylindrical flexion-extension axis of the knee. This fixed flexion-extension axis is best approximated by the axis of cylinders, fit to the circular posterior femoral condyles, and is designated the cylindrical axis of the knee.
An innovative surgical technique of total knee arthroplasty has been developed using MRI-based custom fitting cutting blocks. This technique advocates the use of an individual knee MRI, utilizes the cylindrical axis and proceeds with precise measurements of the arthritic knee. Proprietary software creates a 3-dimensional model of the knee and then corrects the deformity virtually, and recreates the knee's pre-arthritic alignment. Guides are designed to fit on diseased bone and set transverse resection and rotation and enable implant placement that restores joint to pre-disease position.
32 patients were enrolled in this IRB-approved study of total knee replacement. Pre-operative standing anterior-posterior lower extremity x-rays were required for assessment of the degree of malalignment. Patients with a malalignment greater than 15 degrees were excluded from the study. Only 26 knees with varus alignment were in the final study group since the valgus group was very small in number. Computer navigation appears to provide the most precise kinematic measurement of the knee, and was used during the operation to assess and quantitate the pre-operative, intra-operative, and post-operative alignment and potential correction. The pre-operative pathologic malalignment was documented by navigation and the post-operative alignment did demonstrate some correction of this malalignment back to the presumed pre-arthritic alignment.
Change in alignment of 26 varus knees was documented as the following: Pre-op AP standing XRay: average 6.9 degrees varus; Pre-op Navigation: average 6.3 degrees varus; Post-op Navigation: average 3.4 varus degrees. This resulted in post-operative correction of the varus knee to 2.9 degrees.
Documentation of resections planes was noted as the following: Femur AP Resection 3.0 degrees valgus (r: 3.5 varus-4.0 valgus); Femur Distal Resection: 3.7 degrees flexion (r: 2.5 ext-10.0 flex); Femur Rotation Resection: 3.6 degrees internal rotation (r: 2.5 ext-7.5int); Tibia AP Resection 3.3 degrees varus (r: 2.0 valgus-6.0 varus); Tibia Slope Resection: 3.7 degrees posterior (r: 0.5 ant-9.0 post).
This study did support the premise that custom-fitting surgical guides locate the cylindrical axis, as determined by Eckhoff et al. This may provide the patient with less soft tissue stress and allowing a quicker return to function as reported in earlier studies. This surgeon did recognize obstacles using the custom-fitting surgical guides including determining the extent of debridement of soft tissue and osteophytes to allow appropriate capture of the blocks, as well as the risk of PCL injury. Navigation can be used as a training tool to aid in the prevention of significant error.
By locating the cylindrical axis, the natural kinematics of the knee are addressed, including the soft tissue tension. As the mechanical axis is being challenged, we look to the cylindrical axis as our potential objective, unique for each patient. Further validated studies are required, to understand the operative kinematics and the long term effects of the cylindrical axis.
Different types of highly cross-linked polyethylene (HXLPE) have been introduced widely in acetabular cups in hip prostheses to reduce the incidence of wear debris-induced osteolysis. Also, we reported that HXLPE cups with 28-mm alumina ceramic femoral head exhibited lower wear than conventional PE cups. Recently, the combination of HXLPE cup and larger diameter femoral head is used widely to prevent dislocation. In this study, we examined the wear of HXLPE with 32-mm alumina ceramic femoral head and compared it with the wear of HXLPE with 28-mm alumina ceramic femoral head.
The in vivo wear of 60 HXLPE cups (Aeonian; Kyocera Corp., Kyoto, Japan, currently Japan Medical Materials Corp., Osaka, Japan) with 28-mm alumina ceramic femoral head with clinical use for 3.1–9.1 years (mean 7.4 years) and eight HXLPE cups with 32-mm alumina ceramic femoral head used for 2.3–3.2 years (mean 2.8 years) were examined by radiographic analysis.
The early wear rate for the first year of HXLPE cups with 28-mm and 32-mm alumina ceramic femoral head were 0.24±0.10 mm/year and 0.29±0.12 mm/year respectively. There was no significant difference in both femoral head groups (p>0.05). The steady wear rate after 1 year were 0.001±0.03 mm/year and −0.03±0.10 mm/year respectively. There was no significant difference either in both femoral head groups (p>0.05).
These findings from this radiographic analysis suggest that the early wear rate in the first 1 year probably represents the creep deformation in bedding-in stage; and the steady wear rate after 1 year probably represents mainly the wear than of the creep deformation. By the radiographic analysis, HXLPE cups in both femoral head groups exhibited low steady wear rate.
In conclusion, we expect that the combination of HXLPE cup and 32-mm diameter alumina ceramic femoral head has favorable wear properties with possibility of prevention of dislocation in long-term clinical use.
Radiation cross-linked ultrahigh molecular weight polyethylene (UHMWPE) is the bearing of choice in joint arthroplasty. The demands on the longevity of this polymer are likely to increase with the recently advancing deterioration of the performance of alternative metal-on-metal implants. Vitamin E-stabilized, cross-linked UHMWPEs are considered the next generation of improved UHMWPE bearing surfaces for improving the oxidation resistance of the polymer. It was recently discovered that in the absence of radiation-induced free radicals, lipids absorbed into UHMWPE from the synovial fluid can initiate oxidation and result in new free radical-mediated oxidation mechanisms. In the presence of radiation-induced free radicals, it is possible for the polymer to oxidize through both existing free radicals at the time of implantation and through newly formed free radicals
Purpose
Hip arthroplasty is a good treatment option for displaced femoral neck fracture in elderly patients. However, neuromuscular disease such as cerebral infarction or hemorrhage can be a concerning problem for THA since dislocation after operation can frequently occur. The purpose of this prospective study was to evaluate the functional results of modified minimally invasive (MI) two-incision total hip arthroplasty (THA) with the use of large-diameter (>38mm) metal-on-metal articulation in patients with muscle weakness.
Patients and Methods
19 consecutive patients (19 hips) with displaced femoral neck fracture with muscle weakness were enrolled. There were 11 patients with cerebral infarction, 4 patients with cerebral hemorrhage and 4 patients with Parkinson's disease. In the lateral position, an anterolateral approach between the gluteus medius and tensor fascia lata and a posterior approach between the piriformis and gluteus medius were used.
Surgical morbidity, functional recovery, radiological implantation properties, range of motion (ROM) and complications were assessed.
Purpose
The purpose of this study is to know the peri-operative morbidity, clinical and radiographical outcomes of conversion THA from failed transtrochanter rotational osteotomy (TRO).
Patients and methods
From 2003 January to 2009 January, there were 18 hips(18 patients) who underwent conversion THA from TRO for osteonecrosis of the femoral head (ONFH) (Group I). The mean duration from TRO to conversion THA was 2.6 years. We made a matched control group of 18 primary THA for ONFH (Group II) and we evaluated perioperative morbidity and complications in each group. For the clinical evaluation, we checked Harris hip score (HHS) and WOMAC score. For the radiographical evaluation, we evaluated implant position, stability and osteolysis.
Introduction
Patient demand for a less invasive surgical approach reducing the trauma induced to the joint has resulted in the development of Minimally Invasive Surgery (MIS). Although the length of the surgical incision is appealing to patients, the changes are not purely cosmetic. The surgery should not violate the extensor mechanism in any way. Incisions into the quadriceps tendon or into the vastus medialis muscle make the approach less difficult but this violation will slow the recovery and affect the ROM of the knee. In Asian knees, authors found the variation of VMO, which is essential in early functional recovery in TKA patient, is so much, so new clinical test for MIS QS should be needed to show location relationship between the upper pole of the patella and the insertion of VMO itself to avoid unnecessary injury of VMO during TKA.
Purpose
The purpose of this comparison study was to verify whether MIS QS TKA can be a more functional and better method in treatment of advanced degenerative arthritis comparing with mini MIS TKA.
Introduction
Recently robotic-assisted total knee replacement has become a new emerging method of artificial joint implantation, especially in Europe and Asia. We have belived that robotic cutting would result in an improved clinical outcome due to the better fit and alignment of the prosthesis but that has never been proven to our knowledge. The purpose of this study was to compare robotic-assisted implantation of a total knee replacement with conventional manual implantation.
Methods
We reviewed 72 patients who were scheduled for total knee arthroplasty, divided to have either conventional manual implantation of a Zimmer LPS prosthesis (30 patients: Group I) or robotic-assisted implantation of such a prosthesis (32 patients: Group II). The five-axis ROBODOC was used for the robotic-assisted procedures. Radiographs were made at this interval and analyzed for evidence of loosening, prosthetic alignment, and other complications. Independent T-test or Mann-Whitney test was used for statistical analysis at probability level of 95%. SPSS for Windows was used.
Introduction
Previous fluoroscopic studies compared total knee arthroplasty (TKA) kinematics to normal knees. It was our hypothesis that comparing TKA directly to its non-replaced controlateral knee may provide more realistic kinematics information. Using fluoroscopic analysis, we aimed to compare knee flexion angles, femoral roll-back, patellar tracking and internal and external rotation of the tibia.
Material and methods
15 patients (12 women and 3 men) with a mean age of 71.8 years (SD=7.4) operated by the same surgeon were included in this fluoroscopic study. For each patient at a minimum one year after mobile-bearing TKA, kinematics of the TKA was compared to the controlateral knee during three standardized activities: weight-bearing deep-knee bend, stair climbing and walking. A history of trauma, pain, instability or infection on the non-replaced knee was an exclusion criteria. A CT-scan of the non-replaced knee was performed for each patient to obtain a 3-D model of the knee. The Knee Osteoarthitis Outcome Score (KOOS) was also recorded.
Background
There is much research on metal on metal hip resurfacing arthroplasty (HRA) but few studies have reported the outcome with respect to implant characteristics from non-specialist centres.
Aim
To report the survival, clinical and radiological outcomes of a single surgeon series of HRA with an average follow-up of 5 years.
Introduction
Most surgeons utilize one of three axis options in conventional total knee arthroplasty (TKA), the transepicondylar axis (TEA), Whiteside's line (WSL) or the posterior condylar axis (PCA) with an external rotation correction factor. Each option has limitations and no clear algorithm has been determined for which option to use and when. Many surgeons believe the TEA to be the gold standard for determining rotation however it can be difficult to access intraoperatively. WSL and PCA have been used as surrogates for determining axial rotation in conventional TKA but may also be prone to error. MRI based preoperative planning systems overcome intraoperative limitations while accounting for the individual anatomy of each patient, thus helping optimize femoral component rotation. The goal of this study was to examine if coronal plane deformity had any effect on the relationship of conventional referencing options such as WSL and PCA to the TEA.
Methods
Utilizing a preoperative planning software based on MRI, we compared the preoperative posterior femoral condyle resections for three different axis options in 176 TKA. The difference in bone resection amount was used to determine the rotational differences between the axis options in all knees. Assuming that the TEA was the ideal rotational axis, we compared the TEA to both WSL and PCA. A 1-sample t-test and paired t-test were then used to determine if there was a significant rotational difference between the various axis options when accounting for degree and direction of preoperative deformity in the coronal plane.
Introduction
Many uncemented femoral implant designs have had successful outcomes in total hip arthroplasty (THA). Different uncemented stem designs achieve initial and long term stability through shape, size, coating and fit. There is increasing emphasis on bone preservation, particularly in younger and more active patients. The desire to optimize load transfer has led to the development of short stems that seek to achieve fixation in the proximal femur. Short stems designed to achieve stability by engaging the metaphysis or the proximal femoral necks are currently in clinical use. The purpose of this study was to examine the extent to which five stems designed to achieve proximal fixation contact the bone in the proximal femur. Using three-dimensional CT models of 30 femurs, we assessed the fit, fill and contact of each of the five different implants.
Methods
Using three-dimensional computerized templating software designed to navigate robotic surgery, pre-operative CT scans of 30 patients were analyzed. Each of five femoral implant designs (TRILOCK, ARC, ABGII, CITATION, ACCOLADE) was then optimized for size and fit based on manufacturer technique guide and design rationale. The proximal femoral metaphysis was divided into four zones in the axial plane. Five contact points were determined on the frontal plane using anatomical landmarks. Each zone was assessed for cortical contact and fill of the bone-implant interface. We graded contact from 1 to 5, with 5 being 100% contact.
Introduction
Joint reconstruction remains a successful and popular surgery with advances in approaches, implants and techniques continually forthcoming. Various methods of skin closure exist to address issues in efficiency, aesthetics, and barrier to infection. While subcuticular skin closure techniques offer an aesthetic advantage to conventional skin stapling, no measurable differences have been reported. Furthermore, newer barbed sutures, such as the V-loc absorbable suture,
Methods & Materials
A retrospective chart review was conducted of 278 consecutive primary joint reconstruction cases performed by a single surgeon in 12 months from July 2009 through June 2010. Pre-operative history & physical reports were evaluated for co-morbidities (i.e diabetes mellitus), smoking status and body mass index (BMI). Operative dictations by the attending surgeon provided information on the surgical procedure, use of drain, wound closure technique and type of suture/staple used for skin closure. Skin was closed by the primary surgeon and his chief resident. Wounds were closed via staple gun or subcuticular stitch (3-0 Biosyn vs V-Loc) in a consecutive manner, depending on the surgeon's preference in that period. Post-operative clinic notes were reviewed to determine the occurrence of wound complications, issuance of antibiotic prescriptions, or return to the operating room. The cohort consisted of 106 males and 161 females at an average age of 63 years (range: 18–92). Overall, there were 153 procedures at the knee (including TKA, uni-compartmental arthroplasty, patello-femoral arthroplasty) and 125 procedures at the hip (including THA and hemi-arthroplasty).
Introduction
It is thought that socioeconomic status and cultural upbringing influence the patient based outcomes of total joint arthroplasty. Previous studies have shown that patients in a lower socioeconomic class had surgery at an earlier age, increased comorbidities, increased severity of symptoms at presentation, and less satisfaction with the outcome. The purpose of this study was to compare the 1) reasons for undergoing total joint replacement and 2) satisfaction with the outcome among patients in different cultures and socioeconomic categories. We hypothesized that the overall reasons for undergoing surgery would be similar among all groups.
Method
Patients undergoing total hip or knee arthroplasty were divided into groups based on their country of residence and socioeconomic status. The patients were asked to rank their reasons for undergoing surgery preoperatively from 1 to 4 according to importance. They were also asked to state how much relief of pain or improvement in function they expected to obtain. They were then asked to complete a questionnaire assessing their satisfaction with surgery 6 months post-operatively. These results were then compared across the three groups.
INTRODUCTION
Many studies have looked at the effects of titanium tibial baseplates compared to cobalt chrome baseplates on backside wear. However, the surface finish of the materials is usually different (polished/unpolished) [1,2]. Backside wear may be a function not only of tray material but also of the locking mechanism. The purpose of this study was to evaluate the wear performance of conventional polyethylene inserts when mated with titanium tibial trays or cobalt chrome tibial trays that both have non-polished topside surfaces.
MATERIALS AND METHODS
Three titanium (Ti) trays were used along with three cobalt chrome (CoCr) trays. The Ti trays underwent Type II anodization prior to testing. All trays were Triathlon® design (Stryker Orthopaedics, Mahwah, NJ). Tibial inserts were manufactured from GUR 1020 conventional polyethylene then vacuum/flush packaged and sterilized in nitrogen (30 kGy). Appropriate sized CoCr femoral components articulated against the tibial inserts (Triathlon®, Stryker Orthopaedics, Mahwah, NJ).
Surface roughness of the tibial trays was taken prior to testing using white light interferometry (Zygo Corp, Middlefield, CT). A 6-station knee simulator (MTS, Eden Prairie, MN) was used for testing. Two phases were conducted. The first phase used a normal walking profile, as dictated by ISO 14243-3 [3]. The second phase used waveforms created specifically for stair climbing kinematics. Testing was conducted at a frequency of 1 Hz for 2 million cycles for each test with a lubricant of Alpha Calf Fraction serum (Hyclone Labs, Logan, UT) diluted to 50% with a pH-balanced 20-mMole solution of deionized water and EDTA (protein level = 20 g/l) [4]. The serum solution was replaced and inserts were weighed for gravimetric wear at least every 0.5 million cycles. Standard test protocols were used for cleaning, weighing and assessing the wear loss of the tibial inserts [5]. Soak control specimens were used to correct for fluid absorption with weight loss data converted to volumetric data (by material density). Statistical analysis was performed using the Student's t-test (p<0.05).
INTRODUCTION
Biomaterial-related infections are an important complication in orthopaedic surgery [1], and
MATERIAL AND METHODS
A 18mm diameter rod of Ti–6Al–4V alloy ELI grade according to the standard ASTMF136-02 supplied by SURGIVAL was cut into 2 mm thick disk specimens, ground through successive grades of SiC paper to 1200 grade, degreased with a conventional detergent and rinsed in tap water followed by deionised water. The specimens were then chemically polished (CP).
The disks were anodized only on one side by using a two electrode cell in a suitable electrolyte. TiO2 barrier layers, without fluoride (BL), were produced by anodizing in 1 M H2SO4 at 15 mA cm-2 to 90 V, reaching 200 nm of thickness.
Fluoride barrier layers (FBL) were produced in an electrolyte containing 1 M NH4H2PO4 and 0.15 M NH4F, at constant voltage controlled at 20 V for 120 min at 20°C; the thickness of the layer is 140 nm.
Laboratory biofilm-forming strains of
Introduction
We introduce the concept of total knee arthroplasty (TKA) fingerprinting as a tool to characterize and graphically convey the sensitivity of a TKA design to surgical variability in implant component position and patient-related anatomic factors. Identifying sensitive directions preoperatively which would cause undesirable effects may decrease revision surgery by informing surgical decisions and planning. To provide several examples of TKA fingerprinting, we estimated and compared the contact forces in a single TKA type for several configurations, simulating surgical variability and patient-related anatomical factors during a loaded deep squat. The purpose of this study is not to analyze the behavior of this specific TKA design but rather to illustrate a tool that could be used to show, in general, how surgical errors or anatomical factors can alter patello-femoral (PF) and tibio-femoral (TF) contact forces compared to its own reference configuration.
Materials and methods
Computed tomography images of one full cadaveric leg were used to generate 3D models of the bones and to obtain a physiological knee model assuming standard positions of the main soft tissue insertions.
A fixed bearing posterior stabilized knee TKA design was considered in this study. The prosthesis was a medium size, replaced both cruciate ligaments and resurfaced the patella. Following standard surgical procedure, the TKA was virtually implanted, thus defining its reference configuration. Each derivative replaced knee model was then obtained by changing the values of one parameter, or a combination of two, in a range based on literature and surgical experience (Table 1).
A 10 s loaded squat to 120° was performed for each configuration, with a constant vertical hip load of 200 N. These settings match the experimental tests performed in a previous in-vitro analysis on cadaver legs. Each replaced model was developed and analyzed using a validated musculoskeletal modeling software.
The model of the knee included TF contacts and PF contacts of the TKA components, passive soft tissues and active muscle elements. The external forces (ground reaction and weights), the muscle forces (quadriceps and hamstrings) and the frictional forces are applied to the knee joint through the machine. The mechanical properties of the tissues were obtained from literature. With these settings, for each model, both the maximum PF and TF contact forces have been evaluated.
Background
Osteotomies around the knee have been used to correct lower limb mal-alignment for over 50 years. The procedure is technically demanding and carries specific risks of neurovascular injury, incorrect planning and execution, and insufficient fixation. In recent years, with the advent of locking plates, fixation techniques have improved significantly but the correct planning and execution of the operation remains difficult. Despite the availability of CT and MRI 3D imaging, surgical planning is still traditionally performed on 2D plain X-rays [1]. Especially with multi-planar deformities, this technique is prone to error. The aim of this clinical pilot study is to evaluate the feasibility of virtual pre-operative three-dimensional planning and correct execution of osteotomies around the knee with the aid of patient specific surgical guides and locking plates.
Patients and methods
Eight consecutive patients, presenting with significant malalignment of the lower limb were included in the study. Pre-operative CT scans of the affected limb and the normal contra-lateral side were obtained and 3D models of the patient's anatomy were created, using dedicated software (Mimics® 3-matic®, Materialise, Leuven Belgium) [2]. These models were used to evaluate the required surgical correction. The healthy contralateral limb was mirrored and geometrically matched to the distal femur or proximal tibia of the healthy side. A virtual opening wedge correction of the affected bone was used to match the geometry of the healthy contralateral bone. Standard lower limb axes measurements confirmed correction of the alignment [3]. Based on the virtual plan, surgical guides were designed to perform the planar osteotomy and achieve the planned wedge opening and hinge axis orientation (see figure 1). Apart from guiding the osteotomy, the patient specific surgical guide also guided drilling of the planned screw holes. Post-operative assessment of the correction was obtained through planar X-rays, CT-scan and full leg standing X-ray.
Introduction
The published results of the use of a dual mobility cup to prevent instability in primary and revision total hip arthroplasty (THA) have established its efficacy. However, the monoblock, porous cobalt chromium cup design makes secure fixation difficult to achieve, limiting its use in patients with significant acetabular deformity or bone loss. Recently, a modular version of the dual mobility cup was introduced, consisting of a conventional porous shell with holes to allow augmented screw fixation, a highly polished modular metal liner, and a standard bipolar femoral head. The purpose of this report is to present its various indications, the surgical technique, and report our initial results.
Methods
With IRB approval and FDA clearance, we implanted the modular dual mobility (MDM) cup in 15 patients undergoing primary and 5 patients undergoing revision THA deemed high risk for instability. Indications included septic and aseptic revision surgery, developmental hip dysplasia, avascular necrosis, recurrent dislocations, hemiarthroplasty conversion to THA, periprosthetic fracture, abductor insufficiency requiring augmented repair, and hypermobility from auto-immune inflammatory disease.
Introduction
Readmission after Total Hip Arthroplasty (THA) or Total Knee Arthroplasty (TKA) places a great burden on the health care system. As reimbursement systems place increased emphasis on quality measures such as readmission rates, understanding the causes for readmission becomes increasingly important.
Methods
We queried an electronic database for all patients who underwent THA or TKA at our institution from 2006 through 2010. We identified those who had been readmitted within 90 days of discharge from the initial admission. We then collected clinical and demographic data as well as readmission diagnoses by ICD-9 code. We compared rates of readmission using chi-squared test.
In Total Hip Arthroplasty (THA) bone loss is recovered by using compacted porous bone chips. The technique requires the morsellised allograft to be adequately compacted to provide initial stability for the prosthesis in order to prevent early massive subsidence and to induce bone remodeling. Therefore the bone grafts provide initial stability and an environment in which revascularization and incorporation of the graft into the host skeleton may occur. Acetabular reconstruction with impacted morsellised cancellous grafts and cement leads to satisfactory long-term results. In the acetabular impact-grafting procedure, a hammer and an impaction stick is used for manual compaction. Another technique uses a hammer driven by compressed air, which could lead to higher density and improved stability of bone chips in the acetabulum. The aim of this study was to compare two different compaction modes for bone impaction grafting for the acetabulum. The hypothesis was that a pneumatic impaction method would produce less variable results than the manual impaction mode and lead to better compaction results of the bone chips in less time.
Bone mass characteristics were measured by force and distance variation of a penetrating punch, which was lowered into a plastic cup filled with bone chips. For each compaction method and for each time interval (0, 3, 6, 9, 12, 15 and 30 [s] of compaction time) 30 measurements of force and distance variations were taken. From the measurements of force and distance variations bulk density, contact stiffness, impaction hardness and penetration resistance were calculated before and after the established time intervals of compaction. Since not all data was normally distributed the non-parametric U-Test was used for comparison of the two impaction methods. Particle size distribution was determined using sieve analysis according to Din 18123 standard after the compaction experiments.
Results have shown that the pneumatic method leads to higher values in impaction hardness, contact stiffness and bulk density and is more suitable to increase the primary stability of the implant. The differences in bulk density, impaction hardness and contact stiffness where statistically significant (p<0.01). No significant differences were found between the two different methods concerning the penetration resistance. The coefficient of uniformity Cu, calculated from the particle size distribution determined by the sieve analysis, has a value of 3.8.
The particle size distribution is comparable to the results published in literature. Pneumatic impaction achieves higher density values in less time with less force applied and results in more reproducible outcomes when used. It reduces therefore the risk of bone fracture, as smaller peak forces are used for less time. However for optimal osteointegration it is not recommended to achieve maximum density. Further clinical studies should determine a reference value for optimal growth-in of osteocytes. Manual impaction shows more variable results and depends much on the experience of the surgeon. The pneumatic hammer is therefore a suitable tool to standardize the impaction process for acetabular bone defects.
In minimally invasive direct anterior total hip arthroplasty double offset broach handles are used, in order to facilitate the preparation of the femoral canal. The maximum value of the main force peak and the impulse of two types of double offset broach handles (A European version, B American version) were compared to a single offset broach handle (S). Results have demonstrated that the highest values of the main force peak and force impulse were found in the single offset broach handle. Broach handle A had higher impulse values and lower maximum force values compared to broach handle B. In double offset broach handles less energy is transmitted to the tip. Broach handle A has a lower force peak than B and therefore a reduced risk of bone fracture.
Introduction
The orthopaedic market offers more than two hundred different hip femoral stems. Of these, very few have undergone scientific studies with published results. The differences of designs of the stem are mainly related to surface texture and geometry sections. The development of a new cemented hip prosthesis is certainly a very hard task if aiming the improvement of actual performance.
Materials and Methods
This study presents the influence of geometric variables in a novel hip stem concept which was based on the comparison of the performance of the best cemented stems actually in the market. The study was developed using finite element analysis and experiments with in vitro femoral replacements. A numerical simplified model of the hip replacement was designed to generate the final geometry of the femoral stem section. After an in vitro cemented commercial stem was done, with the best cemented stem a Lubinus, Charnley, Stanmore and Müller. Realistic numerical models also allowed us to determine cement mantle stresses of commercial femoral stems that were compared with those obtained for the new concept stem. The new model was then prototyped and tested through in vitro fatigue tests. Finally fatigue tests were also performed to determine the density of cracks in the cement mantles, as well as debonding for both conventional and new designs.
Background
Polyethylene (PE) as a bearing material for total joint replacements (TJR) represents the golden standard for the past forty years. However, over the past decade it becomes apparent that PE wear and the biological response to wear products are the limiting factor for the longevity of TJRs. For this reason research has focused onto PE wear particle analysis. A particle analysis highly depends on the methodological work and results often show discrepancies between different research groups. From there, our hypothesis was, that an often unattended influencing factor is the optical magnification which has been used for particle analyses.
Material and Methods
In the present study samples of a previous conducted knee wear simulator test were used. Wear particles were isolated from the bovine serum using an established method1. Briefly the serum was digested with hydrochloric acid and a continuous stirring and heating. Particles were filtered onto 20nm alumina filters and analyzed using high resolution field emission gun scanning electron microscopy (FEG-SEM). Filters were analyzed on the same points using three different magnifications: 5000, 15000 and 30000. To describe the size and morphology of the particles the equivalent circle diameter (ECD), aspect ratio (AR), roundness (R) and form factor (FF) were specified according to ASTM F 1877-05. The estimated total number (ETN) of particles was calculated based on the number of particles recovered on the filter, the analyzed area, the dilution, evaporation and the total serum volume.
Background
Polyethylene (PE) wear is known as a limiting factor for total knee replacements (TKR). Thus, preclinical wear testing is an important tool to assess the suitability of new designs and new materials. However, standardized testing (e.g. according to ISO 14243) does not cover the individual situation in the patient. Consequentially, this study investigates the following two parameters: Testing-Frequency: Patients with TKR's show a humiliated walking frequency (down to 0,5Hz) compared to standardized testing (1Hz±0.1). In the first part of this study, the influence of a decreased test frequency on the PE wear behavior is investigated Interval of lubricant replacement: For in-vitro testing bovine serum is used as a substitute for the synovial fluid. Physiologically a continuous regeneration and removement of destructed components is taking place. In contrast, for simulator testing the bovine serum is typically changed completely every 500.000 cycles/steps. Therefore the goal of the second part of this study was to test if the serum replacing interval affects the PE wear behavior.
Material and Methods
Wear tests were conducted on an AMTI force controlled knee simulator. A cruciate substituting (ultracongruent) implant design (TC Plus, Smith & Nephew, Rotkreuz, Switzerland) was used.
First, a reference wear study with a test frequency of 1Hz and a lubricant replacement interval (RI) of 500.000 cycles according to ISO 14243-1:2009 was carried out. Tests were run to a total of 5 million cycles.
A second wear test was run with a reduced frequency of 0.5 Hz. The reduced frequency resulted in an extended testing period for the same number of cycles. To exclude an influence of the extended time period, the lubricant was changed, in the first half of testing every 500.000 cycles corresponding to 12 days (cycle depending (CD)), and in the second part every 250.000 cycles corresponding to 6 days (time depending (TD)). Tests were run to a total of 3 million cycles.
A third test was run with a frequency of 1 Hz. For this test a reduced serum RI of 150.000 cycles was choosen. This test was run to a total of 1.500.000 cycles.
Based on numerous national registries, cemented hip replacements have globally better long-term results than uncemented hip replacements. For example, following data have been published in national registries:
These registries demonstrated clearly that cemented fixation should be definitively preferred than uncemented fixation… Despite this evidence, uncemented fixation is more and more used in the majority of the countries performing total hip replacements.
A recent paper analysed the Swedish situation and may give some reasons for explaining this paradox. A Cox proportional hazards model was used to analyze the Relative Risk (RR) of revision for different type of implants and/or fixation for 170,413 total hip arthroplasties. The RR was adjusted for sex, age, and underlying diagnosis. If the RR is lower than 1, less revisions are seen with uncemented fixation and less revisions are seen with cemented fixation when the RR is higher than 1. The figure 1 summarizes the table 6 of this publication.
This figure naturally confirms that globally cemented fixation has a lower revision burden with an adjusted RR of 1.5 (revision of any component for aseptic loosening) than uncemented fixation. This difference in the revision is controlled by the cups, where the adjusted RR for uncemented cups is 1.8. Stems demonstrate an opposite behaviour with a lower revision burden for uncemented fixation with an adjusted RR of 0.4.
Analysing the revision rate of the 5 most common implants (cemented versus uncemented), the adjusted RR for aseptic loosening is lower than 1 for both cups and stems. The difference of the RR between all cups (RR: 1.8) and the 5 most common cups (RR: 0.5) indicates undeniably that some cup have a major influence on the revision rate of uncemented systems.
This analysis allows to draw following conclusions: In national registries, cemented fixation is globally superior. The lower clinical results of uncemented fixation seem to be controlled by badly designed uncemented implants. Modern uncemented implants have as least equivalent results than cemented implants. Based on these results, uncemented fixation will be the key fixation for this century.
Introduction
Historically, amputation or rotationplasty were the treatment of choice in skeletally immature patients. The introduction of expandable endoprostheses in the late 1980s offered the advantages of limb-salvage and limb length equality at skeletal maturity and a promising alternative with improved cosmetic results and immediate weight bearing.
Objective
to describe the Rizzoli experience in reconstruction with three different types of expandable prostheses in growing children with malignant bone tumors of the femur, assess the outcome of limb salvage in these patients, analyze survival and complications related to these prostheses used over time.
Complications of the patellofemoral (PF) joint remain a common cause for revision of total knee replacements. PF complications, such as patellar maltracking, subluxation, dislocation and implant failure, have been linked to femoral and patellar component alignment. Computational analyses represent an efficient method for investigating the effects of patellar and femoral component alignment and loading on output measures related to long term clinical success (i.e. kinematics, contact mechanics) and can be utilized to make direct comparisons between common patellar component design types. Prior PF alignment studies have generally involved perturbing a single alignment parameter independently, without accounting for interaction effects between multiple parameters. The objective of the current study was to determine critical alignment parameters, and combinations of parameters, in three patellar component designs, and assess whether the critical parameters were design specific.
A dynamic finite element (FE) model of an implanted PF joint was applied in conjunction with a 100-trial Monte Carlo probabilistic simulation to establish relationships between alignment and loading parameters and PF kinematics, contact mechanics and internal stresses (Figure 1). Seven parameters, including femoral internal-external (I-E) alignment, patellar I-E, flexion-extension (F∗∗∗∗∗E) and adduction-abduction (A-A) rotational alignment, and patellar medial-lateral (M-L) and superior-inferior (S-I) translational alignment, as well as percentage of the quadriceps load on the vastus medialis obliquus (VMO) tendon, were perturbed in the probabilistic analysis. Ten output parameters, including 6-DOF PF kinematics, peak PF contact pressure, contact area, peak von Mises stress and M-L force due to contact, were evaluated at 80 intervals during a simulated deep knee bend. Three types of patellar component designs were assessed; a dome-compatible patellar component (dome), a medialized dome-compatible patellar component (modified dome), and an anatomic component (anatomic). Model-predicted bounds at 5 and 95% confidence levels were determined for each output parameter throughout the range of femoral flexion (Figure 2). Traditional sensitivity analysis, in addition to a previously described coupled probabilistic and principal component analysis (probabilistic-PCA) approach, were applied to determine the relative importance of alignment and loading parameters to knee mechanics in each of the three designs.
The dome component demonstrated the least amount of variation in contact mechanics and internal stresses, particularly in the 30–100° flexion range, with respect to alignment and loading variability. The modified dome had substantially reduced M-L contact force when compared with the dome. The anatomic design, while wide bounds of variability were predicted, had consistently greater contact area and lowered contact pressure than the dome and modified dome designs. The anatomic design also reproduced more natural sagittal plane patellar tilt than the other components. All three designs were most sensitivity to femoral I-E alignment. Thereafter, sensitivity to component alignment was design specific; for the anatomic component, the main alignment parameter was F-E, while for the domed components it was a combination of F-E and translation (M-L and S-I) (Figure 3). Understanding the relationships and design-specific dependencies between alignment parameters can add value to surgical pre-operative planning, and may help focus instrumentation design on those alignment parameters of primary concern.
Experimental knee simulators for component evaluation or
An existing finite element model of the KKS was modified to extend the capability, and improve the fidelity, of the computational model beyond the experimental setup. An actuator to allow anterior-posterior (A-P) motion of the hip was included and used to prescribe relative hip-ankle A-P kinematics during the simulations. The quadriceps muscle, which in the experimental simulator consisted of a single quadriceps bundle with a point-to-point line of action, was divided into four heads of the quadriceps with physiological muscle paths. The hamstrings muscle, which was not present in the experiment, was represented by point-to-point actuators in four bundles. A flexible control system was developed which allowed control of the quadriceps and hamstrings actuators to match a knee flexion profile, similar to actuation of the experimental KKS, but also allowed control of the compressive tibiofemoral (TF) joint force, medial-lateral (M-L) load distribution, internal-external (I-E) torque and A-P load at the joint. A series of sensors, measuring all six load components on the medial and lateral compartments of the tibial insert, as well as knee flexion angle, were incorporated into the simulation. Instantaneous measurements from the sensors were fed to a control system, implemented within an Abaqus/Explicit user subroutine (Figure 1). The controller was used to drive actuators in the FE model to match target
Introduction
A decrease of 15% in femoral off-set (FO) was reported to generate a weakness of the abductor muscle after THA, which may increase the risk of limping and dislocation. However, this value was defined under experimental conditions using a CYBEX machine, which does not correspond to daily life activities. To our best knowledge, there is no reported study about the effect of the FO alteration on the gait, following THA.
Materials and Methods
To assess the functional consequences of an alteration in the FO, a prospective comparative study was carried out and it included patients who underwent THA for primary osteoarthritis.
In order to select only patients with an isolated FO alteration, the three-dimensional hip anatomy was analysed preoperatively and post-operatively with CT-scans using HipPlan Software. Three groups were defined according to the FO alteration: 15% decrease, restored and 15% increase. The exclusion criteria were: the presence of an arthroplasty or of an associated pathology on the contra-lateral or the same limb, a spine disease and a non-restoration of the other hip parameters (center of rotation, limb length). 26 patients were included: 12 restored, 9 decreased FO and 5 increased FO. The patients were composed of 20 women and 6 men with an average age of 67.7 ± 9 years. All the patients were assessed clinically, pre-operatively and 1 year after surgery with 4 scores: the Poste Merle d'Aubigné score, the Harris score, the womac score and the quality of life score SF12.
A gait analysis was performed at 1 year follow-up using an ambulatory device (Physilog (3)) under normal walking conditions. The patients were asked to walk at their usual normal speed for 30 metres in a standardized corridor: Each limb was compared to the contra-lateral healthy limb.
This talk reviews the topic of patellofemoral arthroplasty from a historical, technical, and clinical perspective. Emphasis is placed on the design rationale, surgical technique, and 11 year clinical results of so-called “patient-matched” or “patient-specific” patellofemoral arthroplasty in which the trochlear implant is matched to the anatomy of the individual patient through the use of pre-operative computerized imaging scans. The implants are inlayed into the articular cartilage without any intra-operative femoral bone resection. Clinical results involving patient-matched patellofemoral arthroplasty are presented with an average follow-up of 11 years. Case studies reviewing our experience with patient-matched trochlear implants in the setting of femoral trochlear dysplasia are also presented.
Patient-specific patellofemoral arthroplasty is a safe and effective treatment for patients with isolated patellofemoral arthritis. The results compare favorably with off-the-shelf patellofemoral arthroplasties that have been reported on over the past thirty years and can be carried out more efficiently.
We believe the key elements that contribute to the success of patient-matched patellofemoral arthroplasty are as follows: (a) a strict inclusion criteria based on pre-operative radiographic evaluation; (b) a meticulous attention to soft-tissue balance and patellofemoral tracking at the time of arthroplasty; and (c) a patient-specific design and manufacturing methodology that ensures accurate and precise anatomic fit while simultaneously providing proper patellofemoral alignment and medial-lateral constraint.
Infection and skin ulcer are major problems in Total Knee Arthroplasty (TKA) and Bipolar Hip Prosthesis (BHP). Sugar (sucrose) has been used for wound care in many countries because it absorbs fluid, stimulates granulation, and suppress growth of bacteria. Trafermin ∗∗∗∗∗ recombinant human basic fibroblast growth factor ∗∗∗∗∗ FGF ∗∗∗∗∗ accelerates granulation process and improves quality of wound healing. We have used sucrose and trafermin for treatment of infection after TKA and BHP.
Six infected TKA with skin ulcer and one infected BHP with fistula were treated with Trafermin and sugar. TKA were performed in four osteoarthritis and two rheumatoid arthritis, and BHP was for femoral neck fracture. Implants were removed in three cases because of deep infection. One was male and six were female, average age were 60.8 years old ranged 43 to 77. Follow-up period were one to 5 years. Four cases were related to MRSA. Sugar treatment were performed for two to 23 weeks, and Trafermin was sprayed once a day for two to 16weeks. In BHP case, sugar therapy was performed intermittently.
In two deep infected TKA cases, infection ceased in one to 4 month and revision TKA were performed. In other four TKA cases, infection were ceased in two to 16 weeks. In BHP case, fistula closed in three years.
Combination of Trafermin and sugar is useful for management of infection and skin ulcer after TKA and BHP
Introduction
The tribological performance of grooved surfaces has been thoroughly analyzed, and such surfaces are thought to have great potential for hard-on-hard joint prosthesis. In related research, femtosecond laser-induced periodic surface structures (FLIPSSs) have been well developed to achieve grooved structures with submicron spacing (700nm) and amplitude (200nm). In this study, submicron-scale periodic grooved structures were made on SUS440C using a femtosecond laser, and its tribological performance was evaluated by both a pin-on-plate reciprocating sliding test and a ring-on-disk test.
Method
The pin-on-plate reciprocating test was performed using PAO6 (30.51cP at 37°C) as the lubricant. The pin and plate specimens were made of SUS440C and were polished to a surface roughness of 0.02μm Ra. The pin specimens were columnar in shape, and radial periodic grooved structures (700nm spacing x 200nm amplitude) were formed on the pin's outer periphery (from 4mm to 5mm in diameter).
The ring-on-disk test was performed using lubricants with different viscosity: PAO6 and PAO2 (4.60cP at 37°C). The ring-on-disk specimens were made of SUS440C and were polished to a surface roughness of 0.03μm Ra. Along the surface of the ring specimens, material was removed to create 4 elevated sections at 0°, 90°, 180° and 270°. These 4 sections were then polished and concentric grooved structures (700nm spacing x 200nm amplitude) were created along a 1.4mm circumferential path within each of these areas.
INTRODUCTION
In patients with neural disorders such as cerebral palsy, three-dimensional marker-based motion analysis has evolved to become a well standardized procedure with a large impact on the clinical decision-making process. On the other hand, in knee arthroplasty research, motion analysis has been little used as a standard tool for objective evaluation of knee joint function. Furthermore, in the available literature, applied methodologies are diverse, resulting in inconsistent findings [1]. Therefore we developed and evaluated a new motion analysis framework to enable standardized quantitative assessment of knee joint function.
MATERIALS AND METHODS
The proposed framework integrates a custom-defined motion analysis protocol with associated reference database and a standardized post-processing step including statistical analysis. Kinematics are collected using a custom-made marker set defined by merging two existing protocols and combine them with a knee alignment device. Following a standing trial, a star-arc hip motion pattern and a set of knee flexion/extension cycles allowing functional, subject-specific calibration of the underlying kinematic model, marker trajectories are acquired for three trials of a set of twelve motor tasks: walking, walking with crossover turn, walking with sidestep turn, stair ascent, stair descent, stair descent with crossover turn, stair descent with sidestep turn, trunk rotations, chair rise, mild squat, deep squat and lunge. This specific set of motor tasks was selected to cover as much as possible common daily life activities. Furthermore, some of these induce greater motion at the knee joint, thus improving the measurement-to-error ratio. Kinetics are acquired by integrating two forceplates in the walkway. Bilateral muscle activity of 8 major muscles is monitored with a 16 channel wireless electromyography (EMG) system. Finally, custom-built software with an associated graphical user interface was created for automated and flexible analysis of gait lab data, including repeatability analysis, analysis of specific kinematic, kinetic and spatiotemporal parameters and statistical comparisons.
Introduction
An important factor in the functional results after total knee arthroplasty (TKA) is the achieved maximal flexion. To date, a TKA still provides dissimilar flexion capabilities compared to the healthy knee, which could be due to the mismatch between the normal knee geometry and the implant geometry. The implant design of the Journey (Smith&Nephew) aims to replicate the normal knee function. According to the manufacturer of the Journey system, it intends to replicate PCL and ACL function, accommodates deep flexion, induces normal tibiofemoral axial rotation and provides proper patellar tracking throughout the entire range of flexion (‘guided motion’). The objective of this study is to investigate the maximal knee flexion one year after surgery of the Journey and its predecessor the Genesis II (Smith&Nephew). In addition, clinical and functional outcomes will be evaluated.
Methods
A total of 124 patients presenting with noninflammatory osteoarthritis received the Journey or the Genesis II prosthesis, by randomization. The primary outcome was defined as the maximum flexion angle on a lateral X-ray performed with the patient lying on a bench and using manual force on bending the knee. Secondary outcomes were: active flexion (lying and standing), Knee Society System score (KSS), Patella Scoring System (PSS), number of adverse events (AE) and satisfaction. The changes in KSS and PSS between the pre-operative situation and 1 year after surgery were calculated as: δKSS = KSS1 year – KSSpre-op, and δPSS = PSS1 year – PSSpre-op. Two-sided t-tests and non-parametric alternatives were performed in order to test for differences between the Journey and the Genesis II group.
The Parva stem has been designed in order to achieve a good cervical and interthrocanteric primary fixation associated with a reliable fit at the isthmus level.
The stem has been conceived to address the larger possible variety of proximal femoral anatomic variations too.
Ability to adapt to patients anatomies being one of the major limitations of earlier neck preserving implants.
The stem therefore features innovative design concepts including the latest generation Modular Neck System, coupled with a revolutionary metal powder manufacturing process and surface engineering technology.
Our first 150 cases with minimum 1 year follow up are presented. All patients have been followed employing the Harris Hip Score and the reduced WOMAC questionnaire to judge their degree of satisfaction.
Particular care has been posed to analyze results for those patients anatomies (i.e. Very Valgus or Varus femurs) where normally neck sparing stems have problems to correctly fit in.
The feed-back we had with this very innovative implant is very encouraging.
Further data collection and longer follow up will be needed in order to confirm these early promising results.
Introduction
Especially in young patients, total hip implants with proven long-term follow-up data should be used. Despite this, almost all patients under 30 years old will face a revision of their hip prosthesis during their life time because of their life expectancy. Therefore, all the used implants should be revisable with reliable outcome. Although, several studies have evaluated the outcome of different THA implants in patients under 30, only few report the long term follow-up of 10 years or more. None of them present the outcome of the revised total hips.
Methods
We retrospectively reviewed prospectively collected data of 48 consecutive patients (69 hips), all received a cemented implant and in case of acetabular bone stock deficiency (29 hips), a reconstruction with bone impaction grafting (BIG) was performed. Mean age at surgery was 24.6 years (range, 16.0–29.0 years). Two patients were lost to follow-up. As far as we know, no revisions are performed in these two patients and their data are included in the study up to their last radiographic control. All failed hips were revised with again cemented implants and, if needed, bone impaction grafting. For the primary THA Kaplan-Meier survival curves at 10- and 15-year endpoint revision for any reason and revision for aseptic loosening were calculated. Separate survival rates at 10- and 15- year were calculated for the BIG group versus the non-BIG group. The outcome of the revised hips was studied and reported with re-revision as the endpoint.
Background
Because of the long life expectancy of young total hip arthroplasty (THA) patients and the limited durability of prosthetic implants in young patients, surgeon's always must take into account that the primary THA will be revised in the future. Therefore, not only the survival of the primary total hip in young patients is important, but we would also like to accentuate the revisability of a primary THA in this specific and high demanding patient population.
Methods
Based on our philosophy, we always use cemented hip in young patients, if needed with acetabular bone impaction grafting. 343 consecutive cemented THA in 270 patients under the age of 50 years were evaluated, all implanted between 1988 and 2006. We also assessed the results of the revised THA (n=53) within the same population. Clinical, radiographical and survival of primary and revision THA were evaluated.
INTRODUCTION
Surgical site infections (SSI) in orthopaedics are a major source of postoperative morbidity. Although perioperative antibiotic prophylaxis is a common practice, orthopaedic infections are still high in numbers, due to the increasing use of osteosynthesis material and implants. Implants are avascular and can be easily colonized with biofilm-producing germs. For both, effective prophylaxis and treatment of orthopaedic infections, the right choice of the antibiotics used, the mode of application (only systemic or systemic & local), the timing, dosage and the duration of antibiotics are of extremely high importance. Their inappropriate use does not only lead to failures in prevention or treatment of infections, but may also promote microbial resistance development and may cause serious side effects for the patients.
SELECTION & USE OF ANTIBIOTICS
Introduction
Fixed Flexion deformity (FFD) is a common deformity amongst patients due to undergo TKR. For their correction surgical algorithm is documented. Resection of distal femur and clearing off posterior recess are two essential steps. In balancing these knees it is suggested to resect extra distal Femur to gain extension space.
Aim
To demonstrate full FFD correction without resecting extra distal Femur.
INTRODUCTION
Knee simulators are being used to evaluate wear. The current international standards have been developed from clinical investigations of the normal knee [1, 2] or from a single TKA patient [3, 4]. However, the forces and motions in a TKA patient differ from a normal knee and, furthermore, the resulting kinematic outcomes after TKA will depend on the design of the device [5]. Consequently, these standard tests may not recreate in-vivo conditions; therefore, the goal of this study was to perform a novel wear simulation using design-specific inputs that have been derived from fluoroscopic images of a deep knee bend.
METHODS
A wear simulation was developed using fluoroscopic data from a pool of eighteen TKA patients performing a deep knee bend. All patients had a Sigma CR Fixed Bearing implant (DePuy) and were well functioning (Knee Society Score > 90). A single patient was selected that represented the typical motions, which was characterized by early rollback followed by anterior motion with an overall modest internal tibial rotation (Figure 1). The relative motion between the femoral and tibial components was transformed to match the coordinate system of an AMTI knee wear simulator [6] and a compressive load input was derived using inverse dynamics [7]. The resulting force and motions (Figure 2) were then applied in a wear simulation with 5 MRad crosslinked and remelted polyethylene for 3 Mcyc at 1 Hz. Components were carefully positioned and each joint (n=3) was tested in 25% bovine calf serum (Hyclone Laboratories), which was recirculated at 37±2°C [3]. Serum was supplemented with sodium azide and EDTA. Wear was quantified gravimetrically every 0.5 Mcyc using a digital balance (XP250, Mettler-Toledo) with load soak compensation.
INTRODUCTION
Telemetric implants have provided us with invaluable data as to the in vivo forces occurring in implanted knee joints. However, only a few of them exists. The knee is one of the most studied joints in the human body and various mathematical knee models have been used in the past to predict forces. However, these simulation studies have also been carried out on a small group of patients limiting their general usefulness in understanding overall trends of knee behavior. Therefore, it is the purpose of this research to study the implant forces experienced by a large group of patients so as to have a better understanding of the overall magnitudes and their variability with knee flexion.
METHODS
The patients were selected from a large database of over 3000 knees for which kinematic analysis had previously been carried out using fluoroscopy. The criteria used for selection was that the patients had a successful knee implant (HSS >90) and were able to perform a weight bearing deep knee bend of at least 110 degrees. The patients were randomly chosen without any other restrictions. The kinetic analysis was carried on a cohort of over 100 patients using a previously published inverse dynamic rigid body model. This model, which has been validated using telemetric data, is capable of predicting the contact forces on the medial and lateral condyles of the knee. Analysis was carried out till 130 degrees of flexion to remove any effect of thigh calf contact that the model does not incorporate. 20 normal knees were also included for comparison.
Background and Objective
Total hip arthroplasty (THA) has been applied to treat pain and disability in patients with post-traumatic arthritis after acetabular fracture for many years. However, the midterm and long-term results of THA for this unique population are still controversial. According to previous studies, we found that uncemented acetabular reconstructions were usually performed in patients who were most likely to have the best results and an abnormal acetabular structure was usually the reason for THA failure. In this study, we evaluated the midterm results of using uncement acetabular components to treat posttraumatic arthritis after acetabular fracture. In addition, we investigated the effects of different acetabular fracture treatments and fracture patterns on THA.
Materials and Methods
Between January 2000 to December 2003, 34 uncemented acetabular reconstructions were performed in 34 patients for posttraumatic arthritis after acetabular fractures. Among them, 31 patients underwent complete clinical and radiographic follow-up for an average of 6.3 years (range, 3.1–8.4 years). There were 22 men and 9 women. The patients' average age was 51 ± 12 years (range, 27–74 years) at the time of arthroplasty. The average interval from fracture to THA was 5.58 ± 4.42 years (range, 0.75–17.5 years). Of the 31 patients, 19 had undergone ORIF (open-reduction group) and 12 had received conservative treatment for the acetabular fractures (conservative-treatment group). Then, 14 had simple pattern fractures (simple group) and 17 had complex pattern fractures (complex group). After midterm follow-up, the radiographic and clinic results of the different groups were compared.
Introduction
This study compares the incidence of post-operative complications (within 90 days) following primary total knee arthroplasty (TKA) and unicompartmental knee arthroplasty (UKA).
Methods
2,919 Consecutive patients were retrospectively reviewed over 5 years at three institutions; 2,290 underwent primary TKA and 629 underwent UKA. Simultaneous bilateral procedures and diagnoses other than osteoarthritis were excluded. Regression analysis was performed to isolate the effects of TKA versus UKA on the rate of post-operative complications.
Background
Various postoperative evaluations using fluoroscopy have reported in vivo knee flexion kinematics under weight bearing conditions. This method has been used to investigate which design features are more important for restoring normal knee function. The objective of this study is to evaluate the kinematics of a Posterior-Stabilized TKA in weight bearing deep knee flexion using 2D/3D registration technique.
Patients and methods
We investigated the in vivo knee kinematics of 9 knees (9 patients) implanted with a Posterior Stabilized TKA (Triathlon PS, Stlyker Orthopedics, Mahwah, NJ). Under fluoroscopic surveillance, each patient did a deep knee flexion under weight-bearing condition. Femorotibial motion including tibial polyethylene insert were analyzed using 2D/3D registration technique, which uses computer-assisted design (CAD) models to reproduce the spatial position of the femoral, tibial components from single-view fluoroscopic images. We evaluated the knee flexion angle, femoral axial rotation, antero-posterior translation of contact points, and post-cam engagement were evaluated.
Each
We report the outcome at a minimum of 10 years follow-up for 80 polished tapered stems performed in 53 patients less than 35-years-old with a high risk profile for aseptic loosening. Forty-six prosthesis were inserted for inflammatory hip arthritis and 34 for avascular necrosis. The mean age at surgery was 28 years in the inflammatory arthritis (17–35) and 27 years in the avascular necrosis (15–35) patients. At a mean follow-up of 14.5 years in the inflammatory arthritis group and 14 years in the avascular necrosis group respectively, survivorship of the 80 stems with revision of the femoral component for any reason as an endpoint was 100 % (95 % CI). Re-operation was because of failure of four metal-backed cups, 3 all polyethylene cups and one cementless cup. None of the stems were radiographically loose. All but two femoral components subsided within the cement mantle to a mean of 1.2 mm (0 tot 2.5) at final follow-up. Periarticular osteolysis was noted in 4 femurs in zone 7. This finding was associated with polyethylene wear and was only seen in those hips that needed revision for a metal backed cup loosening. Our findings show that the polished tapered stem has excellent medium-term results when implanted in young patients with high risk factors for aseptic loosening.
INTRODUCTION
Wear induced osteolysis, material property degradation and oxidation remain a concern in cobalt chrome on polyethylene THR. ECIMA is a cold-irradiated, mechanically annealed, vitamin E blended HXLPE developed to maintain mechanical properties, minimise wear and improve long-term oxidation resistance. This study aimed to compare the
METHODS
Twelve liners (Corin, UK) underwent a 3 million cycle (mc) hip simulation. Three UHMWPE (GUR1050, Ø32 mm, γ sterilised), three HXLPE (GUR1020, Ø40 mm, 75 kGy γ, EtO sterilised) and six ECIMA (0.1 wt% vitamin E GUR1020, Ø40 mm, 120 kGy γ, mechanically annealed, EtO sterilised) liners articulated against CoCrMo femoral heads (Corin, UK). Wear testing was performed in accordance with ISO 14242 parts 1 and 2, in calf serum, with a maximum force of 3.0 kN and at a frequency of 1 Hz. Volumetric wear rate was determined gravimetrically.
ASTM D638 type V specimens were machined from ECIMA material for uniaxial tension testing. Ultimate tensile strength (UTS), yield strength and elongation values were measured. These values were compared to mechanical data available for the other material types.
Following completion of the ECIMA wear testing, three of the tested liners were cut in half. One half of each was subject to accelerated ageing in accordance with ASTM F2003-02, while the other half was tested as received. Each liner half was cross-sectioned and a microtome was used to section 200μm thick slices from each cross-section. Oxidation analysis was performed using a Fourier Transform Infra-red technique in accordance with ASTM F2102-01 throughout the thickness of each liner half. Average oxidation indices for each sample were determined.
INTRODUCTION
Bone resorption around hip stems, in particular periprosthetic bone loss, is a common observation post-operatively. A number of factors influence the amount of bone loss over time and the mechanical environment following total hip replacement (THR) is important; conventional long stem prostheses have been shown to transfer loads distally, resulting in bone loss of the proximal femur. More conservative, short stems have been recently introduced to attempt to better replicate the physiological load distribution in the femur. The aim of this study was to evaluate the bone mineral density (BMD) change over time, in a femur implanted with either a short or a long stem.
METHODS
Finite element models of two implants, a short (Minihip, Corin, UK) and long (Metafix, Corin, UK) hip stem were used to simulate bone remodeling under a physiological load condition (stair climbing). The magnitudes and directions of the muscle forces and joint reaction force were obtained from Heller et al (2001, 2005). An unimplanted femur was also simulated.
A strain-adaptive remodelling theory (Scannel & Prendergast 2009) was utilised to simulate remodelling in the bone after virtual implantation. COMSOL Multiphysics software was used for the analysis. The strain component of the remodelling stimulus was strain energy density per unit mass. This was calculated in the continuum model from the strain energy density, and apparent density.
Bone mass was adapted using a site-specific approach in an attempt to return the local remodelling stimulus to the equilibrium stimulus level (calculated from the unimplanted femur). The minimal inhibitory signal proposed by Frost (1964), was included in the model and described by a ‘lazy zone’, where no bone remodelling occurred.
The three dimensional geometry of the femur was constructed from computed tomography data of the donor (female, 44 years old, right side). Elemental bone properties were assigned from the Hounsfield Unit values of the CT scans. The elastic modulus of the bone was assumed to be isotropic and was determined using a relationship to the apparent bone density (Frost 1964, Rho 1995). The Poisson's ratio for the bone regions varied between 0.2 and 0.32 depending on the apparent density of the bone (Stulpner 1997).
The period of implantation analysed was 2 years. The muscle forces and joint contact loads applied were ramped linearly from zero to full load over a period of two weeks, representing the estimated post operative rest period of a patient.
Background
Synthetic interbody spinal fusion devices are used to restore and maintain disc height and ensure proper vertebral alignment. These devices are often filled with autograft bone to facilitate bone bridging through the device while providing mechanical stability. Nonporous polyetheretherketone (PEEK) devices are widely used clinically for such procedures.1
Methods
Twenty-five goats underwent anterior cervical discectomy and fusion using a
Introduction
Opponents of patellar resurfacing during Total Knee Arthroplasty (TKA) note unique complications associated with resurfacing. Problems include over-stuffing (the creation of a composite patellar-prosthesis thickness greater than the native patella) that may contribute to reduced range of motion; and creation of a patellar remnant that is too thin (in order to avoid over-stuffing) that may contribute to post-operative fracture. Factors including surgical technique, prosthesis design and patient anatomy may contribute to these problems. This study was performed to define the native patellar anatomy, and to compare the effect of differences in component thickness between manufacturers.
Methods
This retrospective, IRB approved study reviewed 803 knees that underwent primary TKA between 2005 and 2011 with a single surgeon. Patellar resurfacing was performed with a round, polyethylene component from one of two different implant designs using the same surgical technique. Data recorded for each patient included: gender; patellar thickness before and after resurfacing; the dimensions and manufacturer of the prosthesis. The residual patellar bone thickness after resection was calculated.
Pin-on-disk studies have demonstrated the role that cross-shear plays in polyethylene wear. It has been found that applying shear stresses on the polyethylene surface in multiple directions will increase wear rates significantly compared to linear sliding. Hip and knee joint replacements utilize polyethylene as a bearing surface and are subjected to cross-shear motions to various degrees. This is the mechanism that produces wear particles in hip and knee arthroplasty bearings and if excessive may lead to osteolysis, implant loosening, and failure. The amount of cross-shear is dependent on the bearing diameter and the angular motion exerted onto the bearing due to the gait of the patient. This study will determine the effect of sliding curvature (angular change per linear sliding distance) on the wear rate of polyethylene. Virgin polyethylene blocks were machined with a 28mm diameter bearing surface and against 28mm cobalt chromium femoral heads in a hip simulator. Dynamic loading was applied simulating walking gait but the motion differed between testing groups. Typical walking gait testing utilizes 23° biaxial rocking motion, in this study, 10°, 15°, 20°, and 23° biaxial rocking motions resulting in various sliding curvatures. Sliding motion path is described in Figure 1 and is a function of the bearing radius and the rocking angle. With increased rocking angle, the sliding distance reduces per cycle and the sliding path becomes more curved (more angular change per linear distance of sliding). Despite a significant increase in sliding distance at higher rocking angles, wear rates were relatively unchanged and ranged from 57mm3/mc to 62mm3/mc. Wear rates per millimeter increased exponentially with reduced sliding arc radius (smaller rocking angle) as shown in Figure 2. This study suggests that wear of polyethylene is highly dependent on sliding path curvature. The sliding path is largely a function of the bearing diameter and the patient activity. Large bearing diameter implants have been recently introduced to increase joint stability. Sliding distance increases proportional to the bearing radius which has led to some concerns regarding increased wear in larger bearings. However, in vitro wear studies have not shown this trend. Increased bearing diameter also increases the sliding path curvature which this study has shown to cause a reduction in wear roughly proportional to the radius of the bearing. Therefore, the increase in wear due to sliding distance is offset by the reduction in wear caused by the sliding curvature resulting in no significant change in wear with increased bearing diameter. Curved sliding path causes a change in surface shear direction which has been shown to increase wear of polyethylene. This study confirms that increased cross-shear in the form of more angular change per linear sliding distance can increase wear of polyethylene exponentially