Title. Longitudinal Intravital Imaging to Quantify the “Race for the Surface” Between Host Immune Cell and Bacteria for Orthopaedic Implants with S. aureus Colonization in a Murine Model. Aim. To assess S. aureus vs. host cell colonization of contaminated implants vis intravital multiphoton laser scanning microscopy (IV-MLSM) in a murine model. Method. All animal experiments were approved by IACUC. A flat stainless steel or titanium L-shaped pin was contaminated with 10. 5. CFU of a red fluorescent protein (RFP) expressing strain of USA300LAC, and surgically implanted through the femur of global GFP-transgenic mice. IV-MLSM was performed at 2, 4, and 6 hours post-op. Parallel cross-sectional CFU studies were performed to quantify the bacteria load on the implant at 2,4,6,12,18 and 24 hours. Results. 1) We developed a high-fidelity reproducible IV-MLSM system to quantify S. aureus and host cell colonization of a bone implant in the mouse femur. Proper placement of all implants were confirmed with in vivo X-rays, and ex vivo photos. We empirically derive the ROI during each imaging session by aggregating the imaged volume which ranges from (636.4um × 636.4um × 151um) = 0.625 +/- 0.014 mm. 3. of bone marrow in a global GFP-transgenic mouse. 2) IV-MLSM imaging acquisition of the “race for the surface”.In vitro MPLSM images of implants partially coated with USA300LAC (RFP-MRSA) were verified by SEM image. Results from IV-MLSM of RFP-MRSA and GFP. +. host cell colonization of the contaminated implants illustrated the mutually exclusive surface coating at 3hrs, which to our knowledge is the first demonstration of “the race for the surface” between bacteria and host cells via intravital microscopy. 3) Quantifying the “race for the surface” with CFU verification of S. aureus on the implant. 3D volumetric rendering of the GFP. +. voxels and RFP+ voxels within the ROI were generated in Imaris. The voxel numbers suggeste that the fight for the surface concludes ∼3hrs post-infection, and then transitions to an aggressive MRSA proliferation phase. The results of WT control demonstrate a significant increase in CFU by 12hrs post-op for both stainless steel (P<0.01) and titanium (P<0.01). Conclusions. We developed IV-MLSM to quantify the “Race for the Surface” between host cells and contaminating S. aureus in a murine
INTRODUCTION. The increasing incidence of periprosthetic femoral fractures (PFF) after total hip arthroplasty presents growing concerns due to challenges in treatment and increased mortality. PFF are often observed when the prosthesis is implanted in varus, especially with blade-type stems. To help elucidate its impact on the PFF risk, the specific research question is: What is the effect of misalignment of a blade-type stem (resulting in down-sized prosthesis) on 1)the distribution and magnitude of cortical stresses and 2)implant-bone micromotion. METHOD. We developed two finite element models consisting of an average female
Background. A careful consideration of change of the rotational profiles of total limb after unilateral total knee arthroplasty is necessary. The aim of the present study was to evaluate the discrepancies of rotational profiles of total limb between operated and non-operated limb following unilateral total knee arthroplasty. Methods. We conducted a retrospective analysis the CT data from 32 patients undergoing primary unilateral total knee arthroplasty using measured resection technique, which
Background. Total knee arthroplasty (TKA) surgical techniques attempt to achieve equal flexion and extension gaps to produce a well-balanced knee, but unexplainable unhappy patients persist. Mid-flexion instability is one proposed cause of unhappy patients. There are multiple techniques to achieve equal flexion and extension gaps, but their effects in mid-flexion are largely unknown. Purpose of study. The purpose of the study is to determine the effects that changing
Introduction. Although total hip arthroplasty is a very successful operation, complications such as: dislocation, aseptic loosening, and periprosthetic fracture do occur. These aspects have been studied in large populations for traditional stem designs, but not for more recent short stems. The design rationale of short stems is to preserve bone stock, without compromising stability. However, due to their smaller bone contact area, high peak stresses and areas of stress shielding could appear in the proximal femur, especially in the presence of atypical bone geometries. In order to evaluate this aspect, we quantified the stress distribution in atypical proximal
Introduction. Polyetheretherketone (PEEK) has been proposed as an implant material for femoral total knee arthroplasty (TKA) components. Potential clinical advantages of PEEK over standard cobalt chrome alloys include modulus of elasticity and subsequently reduced stress shielding potentially eliminating osteolysis, thermal conduction properties allowing for a more natural soft tissue environment, and reduced weight enabling quicker quadriceps recovery. Manufacturing advantages include reduced manufacturing and sterilization time, lower cost, and improved quality control. Currently, no PEEK TKA implants exist on the market. Therefore, evaluation of mechanical properties in a pre-clinical phase is required to minimize patient risk. The objectives of this study include evaluation of implant fixation and determination of the potential for reduced stress shielding using the PEEK femoral TKA component. Methods and Materials. Experimental and computational analysis was performed to evaluate the biomechanical response of the femoral component (Freedom Knee, Maxx Orthopedics Inc., Plymouth Meeting, PA; Figure 1). Fixation strength of CoCr and PEEK components was evaluated in pull-off tests of cemented femoral components on cellular polyurethane foam blocks (Sawbones, Vashon Island, WA). Subsequent testing investigated the cemented fixation using cadaveric distal femurs. The reconstructions were subjected to 500,000 cycles of the peak load occurring during a standardized gait cycle (ISO 14243-1). The change from CoCr to PEEK on implant fixation was studied through computational analysis of stress distributions in the cement, implant, and the cement-implant interface. Reconstructions were analyzed when subjected to standardized gait and demanding squat loads. To investigate potentially reduced stress shielding when using a PEEK component, paired cadaveric femurs were used to measure local bone strains using digital image correlation (DIC). First, standardized gait load was applied, then the left and right
INTRODUCTION. The Woodpecker pneumatic broaching system facilitates femoral preparation to achieve optimal primary fixation of the stem in direct anterior hip replacement using a standard operating table. The high-frequency axial impulses of the device reduce excess bone tension, intraoperative femoral fractures and overall operating time. The Woodpecker device provides uniformity and enhanced control while broaching, optimizing cortical contact between the
Background. Total knee arthroplasty (TKA) surgical techniques attempt to achieve equal flexion and extension gaps to produce a well-balanced knee. Anterior knee pain, which is not addressed by flexion-extension balancing, is one of the more common complaints for TKA patients. The variation in patellofemoral balance resulting from the techniques to achieve equal flexion and extension gaps has not been widely studied. Purpose of study. The purpose of the study is to determine the effects on cruciate retaining (CR) TKA patellofemoral balance when equal flexion and extension gaps are maintained while changing
Introduction. On the basis of a proposal by Noble, the marrow cavity form can be classified into three categories: normal, champagne-fluted and stovepipe. In the present study, three typical finite element femoral models were created using CT data based on Noble's three categories. The purpose was to identify the relationship of stress distribution of the surrounding areas between femoral bone marrow cavity form and hip stems. The results shed light on whether the distribution of the high-stress area reflects the stem design concept. In order to improve the results of THA, researchers need to consider the instability of a stem design based on the stress distributioin and give feedback on future stem selection. Methods. As analyzing object, we selected SL-PLUS and BiCONTACT stems. To develop finite element models, two parts (cortical bone and stem) were constructed using four-node tetrahedral elements. The model consisted of about 60,000 elements. The material characteristics were defined by the combination of mass density, elastic coefficient, and Poisson's ratio. Concerning the analysis system, HP Z800 Workstation was used as hardware and LS-DYNA Ver. 971 as software. The distal end of the femur was constrained in all directions. On the basis of ISO 7206 Part 4,8 that specifies a method of endurance testing for joint prostheses, the stem was tilted 10°, and a 1500 N resultant force in the area around the hip joint was applied to the head at an angle of 25° with the long axis. Automatic contact with a consideration of slip was used. Result. The maximum stress on
Background. Recent studies reported that the kinematic alignment of an implant is more physiological than the traditional methods, and therefore results in better clinical outcomes. They found that for kinematic alignment of the implant, the femoral component should be positioned valgus 2 degrees and tibial component in varus 2 degrees without femoral rotation. Other study also claimed that kinematically aligned TKA does not cause any significant failure; rather, it restores the function of the knee. Therefore kinematic alignment was raised for further patient's functional satisfaction. Purpose. The purpose of our study is to certify correlation between parameters of implant position and postoperative clinical outcomes after kinematic alignment of TKA. Materials and methods. We obtained 32 patients with primary osteoarthritis who need surgical treatment. During operation we targeted tibial varus of 2 degree and femoral valgus of 2 degree on coronal plane, and neutral rotation on axial plane of the knee. ROM (range of motion) was checked at final visit to office with radiology. Average follow up was 44.5 months (range 36–60). We used the Pearson correlation coefficient to determine any relationship between coronal deformity and PCA or TRA for the entire population and individually for each gender. Clinical outcomes including post op active knee ROM, TRA (the angle between the perpendicular line to the TEA and Akagi's line), varus and valgus angle of the knee were also analyzed. Results. Clinical outcomes including post op knee scoring and ROM was improved. There were negative linear relationships between the femoral component rotation (internal and external) and active and passive range of motion after kinematic alignment of TKA. And we also found a negative linear relationship between the tibial rotation of the component and active and passive range of motion. And we also found a negative linear relationship between the gamma angle and active and passive range of motion. The gamma angle is most powerful predictive parameter of postoperative range of motion of the knee. Conclusion. The alignment of the component set into the kinematic alignment of the knee: internal rotation of
INTRODUCTION. Recently the evolution of prosthesis technology allows the surgeon to replace entire limbs. These special prostheses or megaprostheses were born for the treatment of severe oncological bone loss. Recently, however, the indications and applications of these devices are expanding to other orthopaedic and trauma situations. Since some years we are implanting megaprostheses in non-oncological conditions such as septic post-traumatic failures represented by complex non-unions and critical size bone defects. The purpose of this study is to retrospectively evaluate the clinical outcome of this treatment and register all the complications and infection recurrence. MATERIAL AND METHOD. Between January 2008 and January 2016 we have treated 55 patients with septic post-traumatic bone defects In 48/55 cases we perform a 2 steps procedure: 1° step: resection, debridment, devices removal and antibiotic spacer implantation; 2° step: spacer removal and megaprosthesis implantation. In 7/55 patients in whom all the femur was infected, we performed a one step procedure by the complete removal of the femur and a megaprosthesis (Total Femur) implantation. RESULTS. We obtained good results from a clinical, laboratory and radiological point of view with restoration of the function of the affected limb. Only in 5/55 cases the infection recurred. All the Total
When performing limb salvage operations for malignant bone tumours in skeletally immature patients, it is desirable to reconstruct the limb with a prosthesis that can be lengthened without surgery at appropriate intervals to keep pace with growth of the contra-lateral side. We have developed a prosthesis that can be lengthened non-invasively. The lengthening is achieved on the principle of electromagnetic induction. The purpose of this study was to look at our early experience with the use of the Non Invasive Distal Femoral Expandable Endoprosthesis. A prospective study of 17 skeletally immature patients with osteosarcoma of the distal
Background. One of the serious postoperative complications associated with joint replacement is bacterial infection. In our recent investigations, iodine supported titanium implants demonstrated antibacterial activity in both in vitro studies and clinical trials. But it is not clear whether iodine treated titanium implants produce strong bonding to bone. This study evaluated the bone bonding ability of titanium implants with and without iodine surface treatments. Methods. Titanium rods were implanted in intramedullary rabbit femur models, in regard to the cementless hip stem. The implant rods were 5mm in diameter and 25mm in length. Half of the implants were treated with iodine (ID implants) and the other half were untreated (CL implants). The rods were inserted into the distal
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
We present a novel method to derive the surface distance of an osteosynthesis plate w.r.t. the patient-specific surface of the distal femur based on 2D X-ray images. Our goal is to study from clinical data, how the plate-to-bone distance affects bone healing. The patient-specific 3D shape of the femur is, however, seldom recorded for cases of femoral osteosynthesis since this typically requires Computed Tomography (CT), which comes at high cost and radiation dose. Our method instead utilises two postoperative X-ray images to derive the femoral shape and thus can be applied on radiographs that are taken in clinical routine for follow-up. First, the implant geometry is used as a calibration object to relate the implant and the individual X-ray images spatially in a virtual X-ray setup. In a second step, the patient-specific femoral shape and pose are reconstructed in the virtual setup by fitting a deformable statistical shape and intensity model (SSIM) to the images. The relative positioning between
Background. Patellofemoral complications have dwindled with contemporary total knee designs that market anatomic trochlear grooves that intend to preserve normal patella kinematics. While most reports of patellofemoral complications address patella and its replacement approach, they do not focus on shape of trochlear grooves in different prostheses [1]. The purpose of this study was to characterize 3D geometry of trochlear grooves of contemporary total knee designs (NexGen, Genesis II, Logic, and Attune) defined in terms of sulcus angle and medial-lateral offset with respect to midline of femoral component in coronal view and to compare to those of native femurs derived from 20 osteoarthritic patient CT scans. Materials and Methods. Using 3D models of each implant and native femur, sulcus location and orientation were obtained by fitting a spline to connect sulcus points marked at 90°, 105°, 130°, and 145° of femoral flexion (Fig A). Implant reference plane orientations were established using inner facets of distal and posterior flanges. Reference planes of native femurs were defined using protocols developed by Eckhoff et al. [2] where coronal plane was defined using femoral posterior condyles and greater trochanter. In the coronal plane, a best fit line was used to measure sulcus angle and medial-lateral offset with respect to midline at the base of trochlear groove (Fig B). Results. With exception to Logic (0° sulcus angle & 0 mm offset), contemporary knee designs include high valgus angulations (4° to 18°) with laterally-biased offsets (3 to 5 mm). The native sulcus angle on average was slightly valgus, but varied significantly among the cohort (−0.2° ± 4.6°). Native trochlear groove offset was biased laterally (2.5 ± 1.7 mm). Discussion. We observed a considerable geometric deviation between native
Periprosthetic fractures involving the femoral meta/diaphysis can be treated in various fashions. The overall incidence of those fractures after primary total knee arthroplasties (TKA) ranges from 0.3 to 2.5%, however, can increase above 30% in revision TKA, especially in older patients with poorer bone quality. Various classifications suggest treatment algorithms. However, they are not followed consequently. Revision arthroplasty becomes always necessary if the implant becomes loose. Next, it should be considered in case of an unhappy TKA prior to the fracture rather than going for an osteosynthesis. Coverage of the associated segmental bone loss in combination with proximal fixation, can be achieved in either cemented or non-cemented techniques, with or without the combination of osteosynthetic fracture stabilization. Severe destruction of the metaphyseal bone, often does not allow adequate implant fixation for the revision implant and often does not allow proper anatomic alignment. In addition the destruction might include loss of integrity of the collaterals. Consequently standard or even revision implants might not be appropriate. Although first reports about partial distal femoral replacement are available since the 1960´s, larger case series or technical reports are rare within the literature and limited to some specialised centers. Most series are reported by oncologic centers, with necessary larger osseous resections of the distal
Introduction. Primary stability is essential for long-term performance of cementless femoral components. There is debate as to whether collars contribute to primary stability. The results from experimental studies and finite element (FE) analysis have been variable and contradictory. Subtle differences in performance are often swamped by variation between cadaveric specimens in vitro, whereas FE studies tend to be performed on a single femur. However, FE studies have the potential to make comparisons of implant designs within the same cohort of femurs, allowing for subtle performance differences to be identified if present. This study investigates the effect of a collar on primary stability of a femoral prosthesis across a representative cohort of femurs. Materials and Methods. FE models were generated from QCT scans of eight cadaveric femurs taken from the Melbourne Femur Collection (4 male and 4 female; BMI: 18.7 – 36.8 kg.m-2; age: 59 – 80 years) which were of joint replacement age. Heterogeneous bone material properties were assigned based on the CT greyscale information. Each
The Lubinus SP2 femoral stem has a 10 year survivorship of 96%. Curiosity lies in that force-closed stem designs such as the Exeter appear to be more superior to that of the composite-beam like the Lubinus which performs best compared with all other stem types. Biomechanical comparisons of the stress distributions between native and implanted human femora with a cemented Lubinus stem simulating an everyday clinical activity were made. Rosette strain gauges were placed onto fourth generation composite cortical sawbone femora and placed within a hemipelvis rig simulating the dynamic position of the femur during single-legged stance. The femora were then implanted with the Lubinus and principal strain measurements calculated for both intact and implanted femora. These values correlate directly with stress. Statistical calculations were carried out including a two-way ANOVA and Student's unpaired t-test so as to ascertain any relationship between the intact and implanted femora strain values. There were significant decreases (p<0.05) in principal tensile and principal compressive strains upon implantation in the proximal and distal areas of the femur. However, there were insignificant changes (p>0.05) in principal tensile strains at the mid-stem and insignificant changes (p>0.05) in principal compressive strains at both the mid-stem and distal areas. This is the largest biomechanical study to be carried out on this stem and the first in the English language. Changes in principal stresses were not significant in all aspects of the
BACKGROUND. In vitro tests have shown that when a force is applied to the proximal femur within the range of directions spanned during physiological activities, the direction of principal strain vary by a very narrow angle (Cristofolini et al, 2009, J. Engng. Med.). This shows that the anatomy and the distribution of inhomogeneous and anisotropic material properties of the bone tissue make the structure of the proximal femur optimized to withstand a wide range of loading directions. The increasing use of hip resurfacing is associated with early neck fractures of the