Feasibility and accuracy of intraoperative 3D surface scanning to assess femoral component alignment relative to the native distal femoral articular surface in total knee arthroplasty

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PURPOSE: Intraoperative three-dimensional (3D) surface scanning is not routinely used in total knee arthroplasty (TKA) but may allow real-time evaluation of the native joint surface anatomy, enabling intraoperative evaluation and potential adaptation of implant alignment. METHODS: In this experimental study, four unembalmed knee joints from post-mortem donors underwent computer tomography scanning to generate ground-truth 3D bone models. A handheld structured-light surface scanner was then used to capture the 3D structure of the distal femur and the patella at different stages during TKA. Fiducial markers were used to compare registration accuracy between a marker-based and an anatomical landmark-based approach. Conformity between the native anatomy and the femoral component was numerically quantified. Simulated variations of the implant positioning were compared with the initial position. RESULTS: Scanning took 40-60 s per scan; the resulting point cloud was utilized to create a 3D model in 3 min on average, capturing anatomic details with an accuracy of ~0.2 mm. Aligning scans based on bony landmarks was more accurate compared to marker-based registration. Surface conformity comparisons between the femoral component and the native anatomy demonstrated consistent agreement at the distal and posterior condyles, whereas greater deviations were observed in the trochlear region. Simulated sagittal and mediolateral adjustments of the implant orientation were associated with measurable changes in trochlea surface conformity. CONCLUSION: This study demonstrates the technical feasibility of intraoperative structured-light 3D surface scanning for the analysis of femoral and patellar surface geometry, allowing for quantitative assessment of femoral component orientation relative to the native anatomy in a controlled experimental setting. The use of 3D scanning hardware may allow for faster acquisition of high-resolution surface data, compared to conventional imaging techniques. The small sample size and absence of in vivo validation limit the scope of the findings, requiring further studies to evaluate clinical application. LEVEL OF EVIDENCE: Level V, experimental feasibility study based on post-mortem studies.

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