KSSTA - 2026-04-06 - Journal Article
Joint line obliquity disruption negatively affects mid-term patient-reported outcomes following total knee arthroplasty.
Pflüger P, Pedrazzini A, Fischer L, Jud L, Vlachopoulos L, Fucentese SF
Topics
Key Takeaway
Each step-change in joint line obliquity disruption after TKA was associated with a 3.98-point worse WOMAC score (p=0.02) and 3.15-fold increased aseptic revision risk (p=0.04), while change in aHKA was not associated with either outcome.
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Summary
This retrospective cohort study examined whether changes in CPAK classification components—aHKA and JLO—predicted WOMAC scores and aseptic revision risk in 234 TKAs performed with patient-specific instrumentation at minimum 5-year follow-up. Using multi-stage robust regression adjusted for preoperative WOMAC and reintervention, JLO disruption independently predicted worse WOMAC (β=3.98, p=0.02) and higher aseptic revision risk (OR=3.15, p=0.04). Change in aHKA was not associated with either outcome, suggesting JLO preservation—not overall limb alignment correction—is the critical determinant of mid-term TKA success.
Key Limitation
Exclusive use of patient-specific instrumentation in a single cohort prevents determination of whether JLO disruption is a planning failure, an execution failure, or an implant-design constraint, and precludes comparison with conventional or robotic techniques.
Original Abstract
PURPOSE
The influence of change in coronal alignment on clinical outcomes following total knee arthroplasty (TKA) remains unclear. The Coronal Plane Alignment of the Knee (CPAK) classification can be broken up into arithmetic hip-knee-ankle (aHKA) angle and joint line obliquity (JLO) components, potentially identifying distinct failure mechanisms. This study investigated the influence of change in the magnitude and surgical accuracy of CPAK on patient-reported mid-term outcomes and the risk of aseptic revision.
METHODS
This retrospective cohort study included 216 patients (234 TKAs, median age 66 years, 65.3% women) undergoing patient-specific instrumentation in TKA with a minimum follow-up of 5 years. The change in CPAK was divided into aHKA and JLO components. Surgical accuracy was defined as deviation from the planned HKA angle. The primary outcome was the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). A secondary outcome was aseptic revision of TKA. Multi-stage method robust regression and logistic regression models were used, after adjustment for preoperative WOMAC scores and reintervention.
RESULTS
The median WOMAC score improved from 50 (interquartile range [IQR] 24.3) preoperatively to 11 (IQR 19) postoperatively. Our analysis of change in CPAK components revealed JLO disruption as the primary predictor associated with inferior outcomes, with each step change associated with worse WOMAC scores (β = 3.98, p = 0.02) and increased revision risk (odds ratio = 3.15, p = 0.04). In contrast, change in aHKA was not associated with either outcome.
CONCLUSION
Within the CPAK framework, JLO disruption emerged as the primary predictor of patient-reported inferior outcomes and risk of aseptic revision following TKA. Our current findings highlight the importance of preserving native JLO within personalized alignment strategies. Future prospective studies are needed to establish the acceptable degree of JLO change that maintains optimal joint kinematics and patient satisfaction.
LEVEL OF EVIDENCE
Level III.