Changes in coronal plane alignment of the knee classification do not significantly influence outcomes after restricted kinematic alignment total knee arthroplasty.
retrospective_cohort · Level III
Where this comes from
- Record sourced from PubMed, PMID 41416243.
- Also identified by DOI 10.1002/jeo2.70602 and PMC identifier 12709653.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The coronal plane alignment of the knee (CPAK) classification helps understand knee alignment variability, guiding personalised total knee arthroplasty (TKA) strategies. However, evidence regarding the impact of postoperative CPAK classification changes on patient-reported functional outcomes after restricted kinematic alignment (rKA) TKA remains limited. This study aimed to investigate whether CPAK classification changes after TKA with rKA influence functional outcomes, measured by the International Knee Society score (IKS). A retrospective cohort study included 464 patients who underwent primary TKA with a posterior stabilised implant (KNEO<sup>®</sup>) between January 2020 and May 2024. The inclusion criteria were primary or secondary osteoarthritis with complete radiographic and clinical follow-up at 2 years; patients with incomplete data or intraoperative complications requiring implant change were excluded. Pre- and postoperative CPAK classifications were compared, and functional outcomes were assessed using IKS knee and function scores at 2 years of follow-up. Radiographic assessment was performed on standing long-leg radiographs by a single experienced observer. A significant redistribution of CPAK classifications was observed postoperatively (<i>p</i> < 0.001), with 22.2% of CPAK I changing to CPAK II and 19.1% changing to CPAK V. In total, 33.3% of all knees retained their initial CPAK classification. No significant differences were observed in the postoperative IKS Knee (85.2 ± 12.3 vs. 83.9 ± 11.8; <i>p</i> = 0.62) or IKS Function scores (78.5 ± 13.1 vs. 76.9 ± 12.7; <i>p</i> = 0.54). Given the small sample sizes within certain CPAK subtype transitions, subgroup analyses were not feasible. Changes in CPAK classification following rKA-TKA were common but did not significantly influence functional outcomes at 2 years. These findings suggest that CPAK phenotype transition alone may not be a reliable predictor of clinical success, although larger studies are needed to explore subtype-specific effects. Level IV.