Hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) are treatments of end-stage hip disease. Gait analysis studies comparing HRA and THA have demonstrated HRA results in a more normal gait than THA. The reasons may include the larger, more anatomic head diameter, the preservation of the femoral neck with restoration of the anatomical hip centre position and normal proprioception. This study investigated (1)whether femoral head size diameter affects gait; (2)whether gait still differs between THA and HRA patients even with comparable head diameters. We analysed the gait of 33 controls and 50 patients with unilateral hip replacement. Follow-up ranged from 9–68 months. In 27 hips a small femoral head size was used (≤ 36mm); in 23 hips a large head size (>36mm). The small size group consisted of 11 long femoral stem THA and 16 short-stem THA; the large group of 5 long-stem, 8 short-stem THA and 10 HRA patients. There were 14 females/19 males in the control group; 22 females/5 males in the small size group; 13 females/10 males in the large size group.Background
Methods
Accurate implant orientation is associated with improved outcomes after artificial joint replacement. We investigated if a novel augmented-reality (AR) platform (with live feedback) could train novice surgeons to orientate an acetabular implant as effectively as conventional training (CT). Twenty-four novice surgeons (pre-registration level medical students) voluntarily participated in this trial. Baseline demographics, data on exposure to hip arthroplasty, and baseline performance in orientating an acetabular implant to six patient-specific values on a phantom pelvis, were collected prior to training. Participants were randomised to a training session either using a novel AR headset platform or receiving one-on-one tuition from a hip surgeon (CT). After training, they were asked to perform the six orientation tasks again. The solid-angle error in degrees between the planned and achieved orientations was measured using a head-mounted navigation system.Background
Methods
Hip resurfacing arthroplasty (HRA) and total hip arthroplasty (THA) are treatments of end-stage hip disease. Gait analysis studies comparing HRA and THA have demonstrated that HRA results in a more normal gait than THA. The reasons may include the larger, more anatomic head diameter or the preservation of the neck of the femur with restoration of the anatomical position of the hip centre and normal proprioception. This study investigated (1) whether femoral head size diameter affects gait; (2) whether gait still differs between THA and HRA patients even with comparable head diameters. We retrospectively analysed the gait of 33 controls and 50 patients with a unilateral hip replacement, operated by the same surgeon. Follow-up ranged from 9–68 months. In 27 hips a small femoral head size was used (≤ 36mm); in 23 hips a large head size (>36mm). The small size group consisted of 11 long femoral stem THA and 16 short-stem THA and the large group of 5 long-stem THA, 8 short-stem THA and 10 HRA patients. There were 14 females/19 males in the control group; 22 females/5 males in the small size group; 13 females/10 males in the large size group.Background
Methods
Complications such as dislocations, impingement and early wear following total hip arthroplasty (THA) increase with acetabular cup implant malorientation. These errors are more common with low-volume centres or in novice hands. Currently, this skill is most commonly taught during real surgery with an expert trainer, but simulated training may offer a safer and more accessible solution. This study investigated if a novel MicronTracker® enhanced Microsoft HoloLens® augmented reality (EAR) headset was as effective as one-on-one expert surgeon (ES) training for teaching novice surgeons hip cup orientation skill. Twenty-four medical students were randomly assigned to EAR or ES training groups. Participants used a modified sawbone/foam pelvis model for hip cup orientation simulation. A validated EAR headset measured the orientation of acetabular cup implants and displayed this in the participant”s field of view. The system calculated the difference between planned and achieved orientation as a solid-angle error. Six different inclination and anteversion combinations, related to hypothetical patient-specific anatomy, were used as target orientations. Learning curves were measured over four sessions, each one week apart. Error in orientations of non-taught angles and during a concealed pelvic tilt were measured to assess translation of skills. A post-test questionnaire was used for qualitative analysis of procedure understanding and participant experience.Background
Methods
The use of hip resurfacing arthroplasty (HRA) has largely regressed due to the fear of metal-on-metal bearings. However committed HRA users continue to assert the functional advantages that a geometry retaining implant would have on a patient”s hip. Currently worldwide, HRA is only recommended to men who demand an active lifestyle. Despite this precarious indication, it is not clear to what extent HRA has on higher activity function. The aim of this study was to determine the functional extent to which could be achieved with HRA. The primary objective is to assess the loading pattern change for patients implanted with HRA at high walking speeds and inclinations. The second objective is to compare their loading features to a healthy group to determine if a normal gait pattern could be achieved. Between 2012 and 2016, a total of 28 prospective unilateral HRA patients were analysed on an instrumented treadmill from a single centre. All 28 patient patients had a uniform implant type and had no other lower limb operations or disease. Perioperative plain orthogonal radiographs were used to measure hip length and global hip offset change. A healthy control group (n=35) were analysed to compare. All HRA patients gait characteristics were assessed at incrementally higher speeds and inclinations to determine the extent of improvement HRA has on a challenging activity. A Student t-test along with a multivariate analysis was done with significance set at α=0.05. Weight and height variance was accounted with Hof normalisation. The HRA and control group were reasonably matched for age (57 vs 55yrs), BMI (27 vs 25) and height (175 vs 170cm) respectively. Hip measurements revealed less than 5mm change for all cases. The mean time from initial preoperative gait assessment to postoperative assessment was 30 months (24–48months). The mean top walking speed for controls was 1.97m/s and postoperatively 2.1 m/sec for the HRA group. The significant (p<0.001) loading change during flat walking can be seen with restoration of symmetry. Walking at an inclination demonstrated a marked change during weight acceptance (p<0.001) and a loading pattern returning to near normal. This prospective study found HRA patients walking faster than age matched controls. They demonstrated a significant change in their loading pattern, by significantly shifting load from the unaffected side to the implanted side. Uphill walking, an activity which requires more hip flexion, demonstrated a change in stance phase which was near normal. This small comparative study confirms near physiological function can be achieved with HRA at higher activity levels.
Trust in the validity of a measurement tool is critical to its function in both clinical and educational settings. Acetabular cup malposition within total hip arthroplasty (THA) can lead to increased dislocation rates, impingement and increased wear as a result of edge loading. We have developed a THA simulator incorporating a foam/Sawbone pelvis model with a modified Microsoft HoloLens® augmented reality (AR) headset. We aimed to measure the trueness, precision, reliability and reproducibility of this platform for translating spatial measurements of acetabular cup orientation to angular values before developing it as a training tool. A MicronTracker® stereoscopic camera was integrated onto a HoloLens® AR system. Trueness and precision values were obtained through comparison of the AR system measurements to a gold-standard motion capture system”s (OptiTrack®) measurements for acetabular cup orientation on a benchtop trainer, in six clinically relevant pairs of anteversion and inclination angles. Four surgeons performed these six orientations, and repeated each orientation twice. Pearson”s coefficients and Bland-Altman plots were computed to assess correlation and agreement between the AR and Motion Capture systems. Intraclass correlation coefficients (ICC) were calculated to evaluate the degree of repeatability and reproducibility of the AR system by comparing repeated tasks and between surgeons, respectively.Background
Methods
Hip resurfacing remains a safe and effective option according to registry data. Results in women were less reliable, in part owing to soft tissue impingement. Biolox Delta ceramic bearing couples are now in widespread use with very low complication rates. We set about merging these three elements to develop a novel hip resurfacing arthroplasty. Contours of both acetabular and femoral components were generated from biometric data, adapted to the constraints of ceramic machining, to ensure that radii blended from the bearing surface avoiding any sharp boundaries. Plasma spray coating with titanium and hydroxyapatite direct onto ceramic was developed and tested using shear, tensile and taber abrasion testing. Wear testing was carried out to 5 million cycles according to the ASTM. Destructive testing was carried out in a variety of test conditions and angles. Cadaveric testing demonstrated stability using a single use disposable instruments for both conventional and patient specific procedures. Very low dose CT enabled the entire interface to be observed as the Ceramic is radiolucent, enhancing migration analysis, which will be undertaken at 4 intervals to confirm stability. Functional scores and gait analysis will be used in the safety study. The CE study recruitment is underway, with first in human trials starting in summer 2017. PMA submission will follow the safety study. Commercial release of the device in Europe is unlikely before 2019, and in the USA may not be until 2027. The path to novel device development in 2017 is very costly in time and money.
Bisphosphonates (BP) are the first-line treatment for preventing fragility fractures. However, concern regarding their efficacy is growing because bisphosphonate is associated with over-suppression of remodelling and accumulation of microcracks. While dual-energy X-ray absorptiometry (DXA) scanning may show a gain in bone density, the impact of this class of drug on mechanical properties remains unclear. We therefore sought to quantify the mechanical strength of bone treated with BP (oral alendronate), and correlate data with the microarchitecture and density of microcracks in comparison with untreated controls. Trabecular bone from hip fracture patients treated with BP (n = 10) was compared with naïve fractured (n = 14) and non-fractured controls (n = 6). Trabecular cores were synchrotron scanned and micro-CT scanned for microstructural analysis, including quantification of bone volume fraction, microarchitecture and microcracks. The specimens were then mechanically tested in compression.Objectives
Methods
The current, most popular recommendation for cup orientation, namely the Lewinnek box, dates back to the 70's, that is to say at the stone age of hip arthroplasty. Although Lewinnek's recommendations have been associated with a reduction of dislocation, some complications, either impingement or edge loading related, have not been eliminated. Early dislocations are becoming very rare and most of them probably occur in “outlier” patients with atypical pelvic/hip kinematics. Because singular problems usually need singular treatments, those patients need a more specific personalised planning of the treatment rather than a basic systematic application of Lewinnek recommendations. We aim in this review to define the potential impacts that the spine-hip relations (SHRs) have on hip arthroplasty. We highlight how recent improvements in hip implants technology and knowledge about SHRs can substantially modify the planning of a THR, and make the «Lewinnek recommendations» not relevant anymore. We propose a new classification of the SHRs with specific treatment recommendations for hip arthroplasty whose goal is to help at establishing a personalized planning of a THR. This new classification (figures 1 and 2) gives a rationale to optimize the short and long-term patient's outcomes by improving stability and reducing edge loading. We believe this new concept could be beneficial for clinical and research purposes.
The accurate positioning of the total knee arthroplasty affects the survival of the implants(1). Alignment of the femoral component in relation to the native knee is best determined using pre- and post-operative 3D-CT reconstruction(2). Currently, the scans are visualised on separate displays. There is a high inter- and intra-observer variability in measurements of implant rotation and translation(3). Correct alignment is required to allow a direct comparison of the pre- and post-operative surfaces. This is prevented by the presence of the prostheses, the bone shape alteration around the implant, associated metal artefacts, and possibly a segmentation noise. Create a novel method to automatically register pre- and post-operative femora for the direct comparison of the implant and the native bone.Background
Aim
Clear operative oncological margins are the main target in malignant bone tumour resections. Novel techniques like patient specific instruments (PSIs) are becoming more popular in orthopaedic oncology surgeries and arthroplasty in general with studies suggesting improved accuracy and reduced operating time using PSIs compared to conventional techniques and computer assisted surgery. Improved accuracy would allow preservation of more natural bone of patients with smaller tumour margin. Novel low-cost technology improving accuracy of surgical cuts, would facilitate highly delicate surgeries such as Joint Preserving Surgery (JPS) that improves quality of life for patients by preserving the tibial plateau and muscle attachments around the knee whilst removing bone tumours with adequate tumour margins. There are no universal guidelines on PSI designs and there are no studies showing how specific design of PSIs would affect accuracy of the surgical cuts. We hypothesised if an increased depth of the cutting slot guide for sawblades on the PSI would improve accuracy of cuts. A pilot drybone experiment was set up, testing 3 different designs of a PSI with changing cutting slot depth, simulating removal of a tumour on the proximal tibia (figure 1) A handheld 3D scanner (Artec Spider, Luxembourg) was used to scan tibia drybones and Computer Aided Design (CAD) software was used to simulate osteosarcoma position and plan intentioned cuts (figure 1). PSI were designed accordingly to allow sufficient tumour. The only change for the 3 designs is the cutting slot depth (10mm, 15mm & 20mm). 7 orthopaedic surgeons were recruited to participate and perform JPS on the drybones using each design 2 times. Each fragment was then scanned with the 3D scanner and were then matched onto the reference tibia with customized software to calculate how each cut (inferior-superior-vertical) deviated from plan in millimetres and degrees (figure 3). In order to tackle PSI placement error, a dedicated 3D-printed mould was used.Introduction
Methods
Trochlear geometry of modern femoral implants is designed for the mechanical alignment (MA) technique for Total Knee Arthroplasty (TKA). The biomechanical goal is to create a proximalised and more valgus trochlea to better capture the patella and optimize tracking. In contrast, Kinematic alignment (KA) technique for TKA respects the integrity of the soft tissue envelope and therefore aims to restore native articular surfaces, either femoro-tibial or femoro-patellar. Consequently, it is possible that current implant designs are not suitable for restoring patient specific trochlea anatomy when they are implanted using the kinematic technique. This could cause patellar complications, either anterior knee pain, instability or accelerated wear or loosening. The aim of our study is therefore to explore the extent to which native trochlear geometry is restored when the Persona® implant (Zimmer, Warsaw, USA) is kinematically aligned. A retrospective study of a cohort of 15 patients with KA-TKA was performed with the Persona® prosthesis (Zimmer, Warsaw, USA). Preoperative knee MRIs and postoperative knee CTs were segmented to create 3D femoral models. MRI and CT segmentation used Materialise Mimics® and Acrobot Modeller® software, respectively. Persona® implants were laser-scanned to generate 3D implant models. Those implant models have been overlaid on the 3D femoral implant model (generated via segmentation of postoperative CTs) to replicate, BACKGROUND
METHODS
Hip resurfacing arthroplasty (HRA) is currently regaining positive attention as a treatment of osteoarthritis in young, active individuals[1]. The procedure is complex and has low tolerance for implant malpositioning [2]. ‘Precision tools', such as imageless navigation and patient specific instruments, have been developed to assist with implant positioning but have not been shown to be fully reliable [3]. The aim of this study is to present and validate the first step of novel quality control tool to verify implant position intra-operatively. We propose that, before reaming of the femoral head, a handheld structured light 3D scanner can be used to assess the orientation and insertion point of femoral guide wire. Guide wires were placed into the heads of 29 solid foam synthetic femora. A specially designed marker (two orthogonal parallelepipeds attached to a shaft) was inserted into the guide wire holes. Each bone (head, neck and marker) was 3D scanned twice (fig 1). The insertion point and guide wire neck angle were calculated from the marker's parameters. Reference data was acquired with an optical tracking system. The measurements calculated with the 3D scans were compared to the reference ones to evaluate the precision. The comparison of the test retest measurements done with the new method are used to evaluate intra-rater variability.Introduction
Methods
The mechanical alignment (MA) for Total Knee Arthroplasty (TKA) with neutral alignment goal has had good overall long-term outcomes. In spite of improvements in implant designs and surgical tools aiming for better accuracy and reproducibility of surgical technique, functional outcomes of MA TKA have remained insufficient. Therefore, alternative, more anatomicaloptions restoring part (adjusted MA (aMA) and adjusted kinematic alignment (aKA) techniques) or the entire constitutional frontal deformity (unicompartment knee arthroplasty (UKA) and kinematic alignment (KA) techniques) have been developed, with promising results. The kinematic alignment for TKA is a new and attractive surgical technique enabling a patient specific treatment. The growing evidence of the kinematic alignment mid-term effectiveness, safety and potential short falls are discussed in this paper. The current review describes the rationale and the evidence behind different surgical options for knee replacement, including current concepts in alignment in TKA. We also introduce two new classification systems for “implant alignments options” (Figure 1) and “osteoarthritic knees” (Figure 2) that would help surgeons to select the best surgical option for each patient. This would also be valuable for comparison between techniques in future research.
Dislocation is a common complication after proximal and total femur prosthesis reconstruction for primary bone sarcoma patients. Expandable prosthesis in children puts an additional challenge due to the lengthening process. Hip stability is impaired due to multiple factors: Resection of the hip stabilizers as part of the sarcoma resection: forces acts on the hip during the lengthening; and mismatch of native growing acetabulum to the metal femoral head. Surgical solutions described in literature are various with reported low rates of success. Assess a novel 3D surgical planning technology by use of 3D models (computerized and physical), 3D planning, and Patient Specific Instruments (PSI) in supporting correction of young children suffering from hip instability after expandable prosthesis reconstruction following proximal femur resection. This innovative technology creates a new dimension of visualization and customization, and could improve understanding of this complex problem and facilitate the surgical decision making and procedure.Background
Objective
The increase in revision joint replacement surgery and fractures of bone around orthopaedic implants may be partly addressed by keeping bone healthy around orthopaedic implants by inserting implants with mechanical properties closer to the patient's bone properties. We do not currently have an accurate way of calculating a patient's bone mechanical properties. We therefore posed a simple question: can data derived from a micro-indenter be used to calculate bone stiffness? We received ethical approval to retrieve femoral heads and necks from patients undergoing hip replacement surgery for research. Cortical bone from the medial calcar region of the femoral neck was cut into 3×3×6mm cuboid specimens using a diamond wafering blade. Micro-indentation testing was performed in the direction of loading of the bone using a MicroMaterials (MicroMaterials, UK) indenter, using the high load micro-indentation stage (see Figure 1). To simulate in vivo testing, the samples were kept hydrated and were not fixed or polished. From the unloading curve after indentation, the elastic modulus was calculated, using the Oliver-Pharr method using the indentation machine software. To assess which microindentation machine settings most precisely calculate the elastic modulus we varied the loading and unloading rates, load and indenter tip shape (diamond Berkovich tip, 1mm diameter Zirconia spherical tip and 1.5mm diameter ruby spherical tip). Following this, for 11 patients' bone, we performed compression testing of the same samples after they were indented with the 1.5mm diameter ruby spherical tip to assess if there was a correlation between indentation values of apparent elastic modulus and apparent modulus values calculated by compression testing (see Figure 2). Platens compression testing was performed using an Instron 5565 (Instron, USA) materials testing machine. Bluehill compliance correction software (Instron, USA) was used to correct for machine compliance. The strain rate was set at 0.03mm/s. The apparent elastic modulus was calculated from the slope of the elastic region of the stress-strain graph. The correlation between values of apparent modulus from compression testing and indentation were analyzed using IBM SPSS Statistics 22.Introduction
Methods
Surgical planning of long bone surgery often takes place using outdated 2D axes on 2D images such as long leg standing X-rays. This leads to errors and great variation between intra- and inter- observers due to differing frames of reference. With the advent of 3D planning software, researchers developed 3D axes of the knee such as the Flexion Facet Axis (FFAx) and Trochlear Axis (TrAx), and these proved easy to derive and reliable. Unlike 2D axes, clinicians and scientists can use a single 3D axis to obtain measurements relative to other 3D axes, in all three planes Deriving a 3D axis also does not require an initial frame of reference, such as in trying to derive the 2D Posterior Condylar Axis (PCAx), whereby a slight change in slice orientation will affect its position. However, there is no 3D axis derived for the tibial plateau yet. Measurements of tibial joint line obliquity are with a 2D axis drawn on AP long leg standing X-rays. The same applies to tibial plateau rotation, as measured by 2D axes drawn on axial CT/MRI slices. this study aimed to to develop a novel new 3D axis for the tibial plateau to quantify both tibial plateau joint line obliquity and axial rotation. Materialise software version 8.0 (Materialise Inc., Belgium) handled segmentation of CT data and for analysis of bony morphology. A line joining the centroids of the medial and lateral tibial plateaus formed the TCAx (Fig1). A line joining the middle coordinate of the TCAx, to the centre of the best-fit sphere between the medial and lateral malleolus formed the Tibial Mechanical Axis (TMAx). A standard frame of reference aligned 72 tibias with the TCAx horizontal in the axial view, and the TMAx aligned parallel to the global reference coordinate system vertical axis. Tibial joint line obliquity was the angle between the TCAx and TMAx on the medial side, also known as the Medial Tibial Plateau Angle (MPTA)(Fig2). The authors compared reliability and accuracy of the TCAx against three other rotational axes of the tibia as described in the literature.Background
Methods
Across much of medicine, activity levels predict life expectancy, with low levels of activity being associated with increased mortality, and higher levels of activity being associated with longer healthier lives. Resurfacing is a technically demanding procedure that has suffered significant fallout from the failure of a couple of poorly performing designs. However strong evidence associates resurfacing with improved life expectancy in both the short and longer term following surgery. We wondered if there was any relationship between the function of hips following surgery and the extent of that surgery. Could a longer stem inside the femur be the reason for a slightly reduced step length? We proposed the nul hypothesis that there was no clinically relevant difference between stem length and gait. After informed consent each subject was allowed a 5 minute acclimatisation period at 4km/hr on the instrumented treadmill (Kistler Gaitway, Amherst, NY). Their gait performance on an increasing incline at 5, 10 and 15%. At all 0.5km incremental intervals of speed, the vertical component of the ground reaction forces, center of pressure and temporal measurements were collected for both limbs with a sampling frequency of 100Hz over 10sec. They were also asked to log onto our JointPRO website and report their function using Oxford, EQ5D, and Imperial scores. Owing to current restrictions in indications, the patient groups selected were not comparable. However, from our database of over 800 patients who have been through the gait lab. 82 subjects were tested from 2 diagnostic groups (29 conventional THR, 27 hip resurfacing) and compared with a slightly younger group of 26 healthy controls. Patients were excluded if less than 12 months postop, or with any other documented joint disease or medical comorbidities which might affect gait performance. Body weight scaling was also applied to the outputted mechanical data to correct for mass differences. All variables for each subject group were compared to each other using an analysis of variance (ANOVA) with Tukey post hoc test with significance set at α=0.05.Intro
Method
Constitutional knee varus increases the risk of medial OA disease due to increase in the knee adduction moment and shifting of the mechanical axis medially. Hueter-Volkmann's law states that the amount of load experienced by the growth plate during development influences the bone morphology. For this reason, heightened sports activity during growth is associated with constitutional varus due to added knee adduction moment. In early OA, X-rays often show a flattened medial femoral condyle extension facet (EF). However, it is unknown whether this is a result of osteoarthritic wear, creep deformation over decades of use, or an outcome of Hueter-Volkmann's law during development. A larger and flattened medial EF can bear more weight, due to increased load distribution. However, a flattened EF may also extrude the meniscus, leading meniscus degeneration and joint failure. Therefore, this study aimed to investigate whether varus knees have flattened medial EFs of both femur and tibia in a cohort of patients with no signs yet of bony attrition. Segmentation and morphology analysis was conducted using Materialise software (version 8.0, Materialise Inc., Belgium). This study excluded knees with bony attrition of the EFs based on Ahlbäck criteria, intraoperative findings, and operation notes history. Standard reference frames were used for both the femur and tibia to ensure reliable and repeatable measurements. The hip-knee-angle (HKA) angle defined varus or valgus knee alignment. Femur: The femoral EFs and flexion facets (FFs) had best-fit spheres fitted with 6 repetitions. (Fig1) Tibia: The slopes of the antero-medial medial tibial plateau were approximated using lines. (fig2)Background
Methods
Financial and human cost effectiveness is an increasing evident outcome measure of surgical innovation. Considering the human element, the aim is to restore the individual to their “normal” state by sparing anatomy without compromising implant performance. Gait lab studies have shown differences between different implants at top walking speed, but none to our knowledge have analysed differing total hip replacement patients through the entire range of gait speed and incline to show differences. The purpose of this gait study was to 1) determine if a new short stem femoral implant would return patients back to normal 2) compare its performance to established hip resurfacing and long stem total hip replacement (THR) implants. 110 subjects were tested on an instrumented treadmill (Kistler Gaitway), 4 groups (short-stem THR, long-stem THR, hip resurfacing and healthy controls) of 28, 29, 27, and 26 respectively. The new short femoral stem patients (Furlong Evolution, JRI) were taken from the ongoing Evolution Hip trial that have been tested on the treadmill minimum 12months postop. The long stem total hip replacements and hip resurfacing groups were identified from our 800+ patient treadmill database, and only included with tests minimum 12 months postop and had no other joint disease or medical comorbidities which would affect gait performance. All subjects were tested through their entire range of gait speeds and incline after having a 5 minute habituation period. Speed were increased 0.5kmh until maximum walking speed achieved and inclines at 4kmh for 5,10,15%. At all incremental intervals of speed 10seconds ere collected, including vertical ground reaction forces (normalized to body mass), center of pressure and temporal measurements were for both limbs (fs=100Hz). Symmetry Index(SI) were calculated on a range of features comparing leg with implanted hip to the contralateral normal hip. Group means for each feature for each subject group were compared using an analysis of variance (ANOVA) with Tukey post-hoc test with significance set at α=0.05.Introduction
Method
