Restoration of anatomical knee phenotype is associated with improved postoperative clinical outcomes after total knee arthroplasty.

Abstract

Background: A comprehensive assessment of knee phenotypes is crucial for optimizing surgical realignment strategies in total knee arthroplasty (TKA). This study aimed to investigate the relationship between the restoration of preoperative phenotypes, such as joint line orientation (JLO) and alignment, and clinical outcomes following TKA.

Methods: A retrospective review was performed on the records of 1052 primary osteoarthritic knees that underwent mechanically aligned (MA) TKA between March 2016 and October 2021. Patient-reported outcome measures (PROMs) were assessed preoperatively and at 2 years postoperatively. Patients were categorized according to the coronal plane alignment of the knee (CPAK) classification system, which incorporates the arithmetic hip-knee-ankle angle (aHKA) as an indicator of constitutional alignment and JLO. Clinical outcomes were compared between patients whose knee phenotype was maintained and those in whom it was not restored.

Results: Among osteoarthritic knees, the majority (59.4%) were classified as CPAK type I (varus aHKA, apex distal JLO) preoperatively. Using mechanical axis techniques, the native phenotype was restored in 127 (12.1%) of the 1052 cases. These patients demonstrated significantly better postoperative clinical outcomes, as measured by WOMAC function and Forgotten Joint Scores (FJS), compared with the non-restored group (P < 0.05). When alignment was adjusted through detailed analyses of patients with maintained alignment between preoperative and latest follow up assessments, the significant differences in WOMAC function and FJS outcomes between restored JLO and non-restored JLO groups persisted (all P < 0.05). No significant association was observed between the restoration of aHKA and clinical outcomes.

Conclusion: The restoration of the anatomical knee phenotype, particularly JLO, is associated with improved postoperative PROMs, notably in functional outcomes, following TKA. These findings underscore the clinical importance of prioritizing preoperative JLO for optimizing surgical outcomes, rather than focusing exclusively on overall limb alignment.