Dynamic computed tomography assessment of patellofemoral and tibiofemoral kinematics before and after total knee arthroplasty: A pilot study.

Purpose: To develop and evaluate the clinical feasibility of a dynamic computed tomography (CT) protocol for assessing patellofemoral (PF) and tibiofemoral (TF) kinematics before and after total knee arthroplasty (TKA), and to quantify postoperative kinematic changes in a pilot study.

Methods: In this prospective single-centre study, patients with primary osteoarthritis scheduled for cemented TKA underwent dynamic CT scans preoperatively and at 1-year follow-up during active flexion-extension-flexion. Preoperatively, the femur, tibia and patella were segmented using a neural network. Postoperatively, computer-aided design (CAD) implant models were aligned to CT data to determine relative implant-bone orientation. Due to metal artefacts, preoperative patella meshes were manually aligned to postoperative scans by four raters, and averaged for analysis. Anatomical coordinate systems were applied to quantify patellar flexion, tilt, proximal tip rotation, mediolateral translation and femoral condyle anterior-posterior translation. Descriptive statistics were reported, and interoperator agreement for patellar registration was assessed using intraclass correlation coefficients (ICCs).

Results: Ten patients (mean age, 65 ± 8 years; 6 men) were analysed across a shared flexion range of 14°-55°. Postoperatively, the patella showed increased flexion (median difference: 0.9°-3.9°), medial proximal tip rotation (median difference: 1.5°-6.0°), lateral tilt (median difference: 2.7°-5.5°), and lateral shift (median difference: -1.5 to -2.8 mm). The medial and lateral femoral condyles translated 2-4 mm anterior-posteriorly during knee flexion. Interoperator agreement for patellar registration ranged from good to excellent across all parameters (ICC = 0.85-1.00).

Conclusion: This pilot study demonstrates that dynamic CT enables in vivo assessment of PF and TF kinematics before and after TKA. The protocol quantified postoperative kinematic changes and demonstrated potential as research tool. Further automation is needed to investigate relationships between these kinematic patterns and patient outcomes in larger-scale studies.

Level of evidence: Level III.