Aims Periprosthetic femoral fractures (PPF) are a serious complication of total hip arthroplasty (THA) and are becoming an increasingly common indication for revision arthroplasty with the ageing population. This study aimed to identify potential risk factors for PPF based on an analysis of registry data. Methods Cases recorded with PPF as the primary indication for revision arthroplasty in the German Arthroplasty Registry (Endoprothesenregister Deutschland (EPRD)), as well as those classified as having a PPF according to the International Classification of Diseases (ICD) codes in patients’ insurance records were identified from the complete datasets of 249,639 registered primary hip arthroplasties in the EPRD and included in the analysis. Results The incidence of PPFs was higher (24.6%; 1,483) than reported in EPRD annual reports listing PPF as the main reason for revision (10.9%; 654). The majority of fractures occurred intraoperatively and were directly related to the implantation process. Patients who were elderly, female, or had comorbidities were at higher risk of PPFs (p < 0.001). German hospitals with a surgical volume of < 300 primary procedures per year had a higher rate of PPFs (p < 0.001). The use of cemented and collared prostheses had a lower fracture risk PPF compared to uncemented and collarless components, respectively (both p < 0.001). Collared prostheses reduced the risk of PPF irrespective of the fixation method and hospital’s surgical volume. Conclusion The high proportion of intraoperative fractures emphasises the need to improve surgeon training and surgical technique. Registry data should be interpreted with caution because of potential differences in coding standards between institutions. Cite this article: Bone Joint J 2021;103-B(4):650–658.
Many failures in total joint replacement are associated to prosthesis‐to‐bone mismatch. With recent additive‐manufacturing, that is, 3D‐printing, custom‐made prosthesis can be created by laser‐melting metal powders layer‐by‐layer. Ankle replacement is particularly suitable for this progress because of the limited number of sizes and the poor bone stock. In this study a novel procedure is presented for subject‐specific ankle replacements, including medical‐imaging, joint modelling, prosthesis design, and 3D‐printing. Three shank‐foot specimens were CT‐scanned, and corresponding 3D bone models of the tibia, fibula, talus, and calcaneus were obtained. From these models, specimen‐specific implant sets were designed according to three different concepts, and 3D‐printed from cobalt‐chromium‐molybdenum powder. Accuracy of the overall procedure was assessed via distance map comparisons between original anatomical and final metal implants. Restoration of natural ankle joint mechanics was check after implantation of each of the three sets. In a special rig, a manually‐driven dorsi/plantar‐flexion was applied throughout the passive arc. Additionally, at three different joint positions, joint torques were imposed in the frontal and axial anatomical planes. Mean manufacturing errors were found to be smaller than 0.08 mm. Consistent motion patterns were observed over repetitions, with the mean standard deviation smaller than 1.0 degree. In each ankle specimen, mobility, and stability at the replaced joints compared well with the original natural condition. For the first time, custom‐made implants for total ankle replacements were designed, manufactured with additive technology and tested. This procedure is a first fundamental step toward the development of completely personalized prostheses. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
Background The influence of the surgical process on implant loosening and periprosthetic fractures (PPF) as major complications in uncemented total hip arthroplasty (THA) has rarely been studied because of the difficulty in quantification. Meanwhile, registry analyses have clearly shown a decrease in complications with increasing experience. The goal of this study was to determine the extent of variability in THA stem implantation between highly experienced surgeons with respect to implant size, position, press-fit, contact area, primary stability, and the effect of using a powered impaction tool. Methods Primary hip stems were implanted in 16 cadaveric femur pairs by three experienced surgeons using manual and powered impaction. Quantitative CTs were taken before and after each process step, and stem tilt, canal-fill-ratio, press-fit, and contact determined. Eleven femur pairs were additionally tested for primary stability under cyclic loading conditions. Results Manual impactions led to higher variations in press-fit and contact area between the surgeons than powered impactions. Stem tilt and implant sizing varied between surgeons but not between impaction methods. Larger stems exhibited less micromotion than smaller stems. Conclusions Larger implants may increase PPF risk, while smaller implants reduce primary stability. The reduced variation for powered impactions indicates that appropriate measures may promote a more standardized process. The variations between these experienced surgeons may represent an acceptable range for this specific stem design. Variability in the implantation process warrants further investigations since certain deviations, for example, a stem tilt toward varus, might increase bone stresses and PPF risk.
Aseptic loosening is one of the major reasons for re-revisions of cementless revision stems. Insufficient primary stability is associated with bone characteristics and the surgical process. This study aimed to investigate how femur morphology and preparation methods influence the primary stability of revision stems. The Femur morphology was described by the upper femoral curvature (UFC) and an individualized Dorr type classification based on the ratio between the canal-to-calcar ratio (CCR*) and the cortical index (CI*) introduced as the cortical-canal shape (CCS). Manual and powered reaming in combination with helical and straight reamers were used to prepare the bone cavity of 10 cadaveric human femur pairs. Forces during stem impaction were recorded (Reclaim, Depuy Synthes). Micromotion at the bone-implant interface during cyclic axial loading and torsional load to failure was determined. The CCS and impaction forces (R 2 = 0.817, p < 0.001) or torsional strength (R 2 = 0.577, p < 0.001) are inversely related. CCS did not correlate with micromotion during axial loading (R 2 = 0.001, p > 0.999), but proximal femoral curvature did (R 2 = 0.462, p = 0.015). Powered reaming and straight reamers led to an improved torsional strength (both: p = 0.043). The Individualized Dorr classification CCS and UFC allows a good estimation of the primary stability of revision stems. For severely curved Dorr type-C femurs, an alternative anchorage method should be considered clinically.
Category: Hindfoot Introduction/Purpose: Surgical restoration of the morphology of deformed tarsal bones caused by severe arthritis and complex fracture may require surgical procedure such as custom 3D printed total talar replacement, extensive bone reconstruction of complex fractured bones, etc. There are variations in the tarsal bones between individuals and with advances in medical imaging/personalized manufacturing techniques such as additive manufacturing; reliance on the contralateral side of the patient becomes important. The purpose of this study is to evaluate the left to right symmetry characteristics of tarsal bones utilizing weightbearing computed tomography in order to effectively and reliably use the 3D morphology of the contra-lateral foot. Methods: 15 bilateral data sets from weightbearing CT scans were used from a foot and ankle unit. The images were processed to produce 3-dimensional computer models of the distal tibia, talus, talar dome and calcaneus. The left and right tarsal bones in each pair were first mirror-imaged and then registered using a 3D optimal registration technique. After the registration, a distance-mapping algorithm was used to determine the surface-to-surface distance distribution between the paired and registered bones (Figure 1). Maximum surface-to-surface distance indicated the level of asymmetry between the bones. In addition, the volume and surface area of each bone was established and the percentage difference in volume and surface area were established providing an additional measure of left-to-right asymmetry. Figure 1 – Surface-to-surface distance map shiwing the left-to-right deviations (in millimeters) for a talus and distal tibia for one subject. Results: The results indicated a left-to-right volume mean difference of less than 2.6% for the talus, 3.1% for the distal tibia and 2.3% for the calcaneus. The mean difference of the surface area was 2.4% for the talus, 1.9% for the distal tibia and 1.6% for the calcaneus. The distance mapping showed a maximum average surface-to-surface left-to-right deviation of 0.8 mm for the talus, 0.4 mm for the talar dome, 0.65 mm for the distal tibia and 0.95 mm for the calcaneus. Conclusion: Based on the results of this study, morphometric analysis showed high level of bilateral symmetry indicating that restoration of the tarsal bone based on the contra-lateral foot is a feasible and reliable approach. The study established the level of confidence with which such an approach can be implemented.
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