The Insufficient Coverage of Lateral Trochlear Resection is Correlated to the Tibiofemoral Alignment Parameters in Kinematically Aligned TKA: A Retrospective Clinical Study

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Abstract
Background: The mismatching of the femoral component and trochlear resection surface is very common in kinematically aligned total knee arthroplasty (KA-TKA) when conventional prostheses are employed. This mismatching is mainly manifested in the insufficient coverage of the bone cut surface of the lateral trochlea. The aim of present study is to explore whether this mismatch is related to the alignment parameters of the tibiofemoral joint. Methods: 45 patients (52 knees) who underwent KA-TKA in our hospital were included. There were 16 patients (16 knees) received surgery using patient specific instrumentations, and conventional instruments with caliper and other special tools were employed in the other 29 patients (36 knees). The widths of exposed resection bone surface at the middle (MIDexposure) and distal (INFexposure) levels on the lateral trochlear were measured as dependent variables, while the hip-knee-ankle (HKA) angle, mechanical lateral distal femoral angle (mLDFA), joint line convergence angle (JLCA), medial proximal tibial angle (MPTA) and transepicondylar axis angle (TEAA) were measured as independent variables. Correlation analysis and subsequent linear regression were conducted among the dependent variables and various alignment parameters of the tibiofemoral joint. Results: The incidence of insufficient coverage of the lateral trochlear cut bone surface was 86.5%, with MIDexposure and INFexposure being 2.3 (0-6mm) and 2.0 (0-5mm), respectively. The widths of two levels of exposed bone resection were significantly correlated to mLDFA and HKA, but were not related to TEAA. Conclusions: the insufficient coverage of trochlear resection surface in KA-TKA is negatively correlated with the degrees of valgus of the distal femoral joint line and the degrees of varus of the knee. The present study suggest that in the development of KA-specific prostheses, attention should be paid to the effects of tibiofemoral alignment parameters on the prosthetic matching of the trochlear resection surface.

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