Spinopelvic mismatch is associated with patient-reported outcome measures after total knee arthroplasty at a mean follow-up of 15 years.

Background: Total knee arthroplasty (TKA) is widely performed; yet, up to 25% of patients are dissatisfied with outcomes. Our aim was to evaluate the association between a spinopelvic mismatch and patient-reported outcomes after TKA.

Methods: This was a retrospective study of 101 TKAs performed for osteoarthritis, at a mean 14.6 (range, 10.0-18.0) years post-surgery. Postoperative knee joint perception was evaluated as 'artificial', with or without restrictions, or 'natural'. Age, sex and the spinopelvic mismatch were compared between the 'artificial' (n = 54) and 'natural' (n = 47) perception groups. Multiple logistic regression analysis was used to identify predictive factors of an artificial perception, with a receiver operating characteristic curve to identify cut-off values for significant factors.

Results: A spinopelvic mismatch, defined as a pelvic incidence minus lumbar lordosis (PI-LL) ≥ 10°, was associated with an artificial perception (odds ratio, 1.57; 95% confidence interval, 1.29-3.22; P = 0.023). An artificial joint perception was related to lower Knee Injury and Osteoarthritis Outcome Score-Joint Replacement (KOOS-JR, P = 0.021) and EuroQol 5-Dimension (EQ-5D, P = 0.025) scores. The cut-off PI-LL of 11° differentiated the groups with a sensitivity of 87.0% and specificity of 91.9%. Postoperative KOOS-JR (P < 0.001), EQ-5D (P = 0.014), satisfaction (P = 0.015), knee extension angle (P = 0.024), and perception (P = 0.032) differed between the groups when the PI-LL threshold was set at 10°.

Conclusion: A spinopelvic mismatch (PI-LL ≥ 10°) is associated with a risk of artificial perception of function after TKA. Measurement of the PI-LL could assist patients and surgeons to predict TKA outcomes.