Coronal plane alignment of the knee classification in patients with osteoarthritis and the clinical outcomes of its alteration in total knee arthroplasty: a cross-sectional analysis of a Chinese cohort.

Abstract

Purpose: The optimal coronal alignment in total knee arthroplasty (TKA) remains debatable, necessitating a clear, simple, and universal classification system. The Coronal Plane Alignment of the Knee (CPAK) classification introduced in 2021 provides a nuanced method for categorizing knee alignment. This study aimed to evaluate the distribution of CPAK types among Chinese patients with osteoarthritis (OA) and clarify the differences in surgical outcomes among different CPAK types.

Methods: We analyzed the data from 961 patients with OA. All patient information was derived from a single-centre retrospective cohort. Radiological measurements from full-length radiographs were used to classify patients into CPAK types. Propensity score matching was used to compare outcomes among different CPAK types. Demographic and clinical data, information regarding patient satisfaction, and Knee Society Score (KSS), Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and Forgotten Joint Score (FJS) scores were also collected.

Results: Among Chinese patients with OA, the most common type was Type I (56.8%), followed by Type II (16.1%). After TKA, CPAK types IV and V, were predominant, accounting for 28% and 31% of patients; CPAK types did not change with OA progression. No significant differences in satisfaction, KSS, or WOMAC scores were observed among patients with CPAK types IV, V, and VII. However, Type V patients had significantly higher FJS scores, potentially due to corrected preoperative varus alignment.

Conclusion: This study established the CPAK type distribution among Chinese patients with OA to guide alignment strategies for TKA. Different CPAK types did not significantly affect overall satisfaction but influenced functional recovery, underscoring the need for personalized TKA approaches.