| Popis: |
Background: Discrepancies in bone resection between the medial and lateral compartments is very common in total knee replacement (TKA) when mechanical alignment (MA) is used. The purpose of this study was to explore whether and how joint line orientation affects the gross amount of bone resected in mechanically aligned TKA.Methods: A total of 112 patients (137 knees) diagnosed with osteoarthritis (OA) were included. Bone resection simulations were conducted in the coronal view using full-length weight-bearing radiographs per the technical parameters of MA, and the feasibility of simulated osteotomy was verified via intraoperative caliper measurement. Correlation and regression analyses were conducted comparing the amount of bone resected and various parameters, including hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), joint line congruency angle (JLCA), and medial proximal tibial angle (MPTA). Moreover, any intraoperative bone resection adjustments that were made were retrospectively collected using a medical record query system.Results: All knees in the current case series could be artificially divided into 4 subgroups: 84 varus knees (61.3%) with valgus femurs in subgroup 1, 32 varus knees (23.4%) with varus femurs in subgroup 2, 14 valgus knees (10.2%) with varus tibias in subgroup 3, and 7 valgus knees (5.1%) with valgus tibias in subgroup 4. Simulated bone resection thickness was highly consistent with intraoperative measurements. MPTA and mLDFA were positively correlated with the amount of bone resected in subgroup 1. The regression equation was: Maximum resection thickness (mm) = 0.556*mLDFA (deg.) + 0.098*MPTA (deg.) -39.74; R2=0.808. Similarly, intraoperative bone resection adjustments also showed a correlation with mLDFA in subgroup 1.Conclusions: Deformities in knee OA can be divided into 4 subgroups based on the alignment of extremities and the joint line orientation. When TKA is performed in varus knees with valgus femurs using conventional instruments and mechanical alignment techniques, the amount of bone resected in the coronal plane demonstrates a linear relationship with the patient’s mLDFA. |
