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Traditional mechanical methods for implant and bone cement removal during total hip arthroplasty (THA) revision surgeries typically lead to surrounding tissue damage and increased risk of femoral fractures. Transcutaneous induction heating is a promising new removal approach as it causes softening of the thermoplastic bone cement, and thus prevents damage to the surrounding tissue during removal and increases stability post-revision. However, precise knowledge of the heat transfer between implant and bone cement is necessary to minimize the risk of thermal damage to surrounding tissues. In this context, knowledge of the thermal contact conductance (TCC) at the interface of Co28Cr6Mo hip stems and PMMA-based bone cement is a key issue. The present study addresses the challenge of measuring TCC by proposing an inverse method of determination using infrared thermography measurements of the heating process and a finite element simulation with a variable parameter for the TCC. Results indicate TCC values of 3,125 ± 275 Wm - 2 K - 1 for dry interfaces and 5,100 ± 300 Wm - 2 K - 1 for wet interfaces. The influence of heat conduction on bone cement surface temperature is significant, impacting the measured surface temperatures by 15-19% for wet and 23-30% for dry interfaces. These findings are crucial for the design of heating procedures and minimization of thermal damage during induction heating assisted THA revisions., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2025. The Author(s).)

In modern knee arthroplasty, surgeons increasingly aim for individualised implant selection based on data-driven decisions to improve patient satisfaction rates. The identification of an implant design that optimally fits to a patient's native kinematic patterns and functional requirements could provide a basis towards subject-specific phenotyping. The goal of this study was to achieve a first step towards identifying easily accessible and intuitive features that allow for discrimination between implant designs based on kinematic data. A squat-cycle was simulated on eight fresh frozen specimens mounted in a weight-bearing knee rig, each initially tested under native conditions, and then after implantation with four different implant types (CR/CS, MS, LS, and PS). The kinematic signals of these five configurations were compared to determine whether key differences between implants could be detected leveraging two methodological approaches: (1) statistical parametric mapping to directly compare waveforms and (2) simple paired t-tests to compare the three-dimensional coordinates of the functional centres of rotation determined using a previously published REference FRame Alignment Method (REFRAME). While statistical parametric mapping of the kinematic data revealed only small differences in certain comparisons (e.g. LS vs. PS, and MS vs. LS) under lenient statistical testing conditions, the application of REFRAME showed clear differences between implants (for all implant combinations except for CR/CS vs. LS), even under conservative statistical testing. Since for most implant combinations, significant differences in the centres of rotation were found using REFRAME, this approach could present a suitable tool for discriminating between the kinematics of different implant types. Preoperative assessment of joint kinematics, combined with this REFRAME application, could therefore provide a key approach for improved clinical selection of implant type., Competing Interests: Declarations. Competing interests: B.Braun Aesculap AG (Tuttlingen, Germany) provided research support for this study. Some of the authors (AS, AOV, AM and TMG) are employees of B.Braun Aesculap AG (Tuttlingen, Germany). AOV, AS, and AM are all listed as co-inventors on a pending patent application submitted by B.Braun Aesculap AG under number DE102022125697A1, which claims a system for standardising axis orientation and position in kinematic data, used in this study. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript., (© 2025. The Author(s).)