The significance of the pelvic incidence measurement as a possible predictor of TKA outcome.

PURPOSE

To evaluate the association between the sagittal alignment of the pelvis and residual knee flexion contracture after total knee arthroplasty (TKA). This is important as a flexion contraction can be associated with the risk of poor outcomes and patient satisfaction after TKA.

METHODS

This was a retrospective, case-control, study of 200 osteoarthritic knees, contributed by 200 patients, over a mean follow-up of 2.4 years. The following factors were compared between patients 'with' (46 knees) and 'without' (154 knees) a residual flexion contracture ≥ 10° after TKA: age, sex, pelvic incidence (PI), anterior femoral bowing, femoral component flexion angle (FFA), and patient-reported outcomes. Logistic regression and receiver operating characteristic curve analyses were used to identify predictive factors.

RESULTS

The following factors were predictive of a residual flexion contracture ≥ 10°: a pelvic incidence ≥ 55° (odds ratio, 1.29; 95% confidence interval, 1.05-1.59; P = 0.031) and the FFA (odds ratio, 1.08; 95% confidence interval, 1.03-1.14; P = 0.044). A pelvic incidence cutoff of 55° yielded a significant between-group difference, with a sensitivity of 78.4% and specificity of 89.9% to differentiate a residual knee flexion contracture ≥ 10° (P = 0.001), patient satisfaction (P = 0.029), EuroQol 5-Dimension score (P = 0.028), anterior femoral curvature (P = 0.031), and Knee Injury and Osteoarthritis Outcome Score-Joint Replacement score (P = 0.046).

CONCLUSION

A pelvic incidence > 55° is associated with a residual knee flexion contracture ≥ 10° after TKA. The significance of the pelvic incidence measurement as a possible predictor of TKA outcome was highlighted, including its impact on patient satisfaction.

LEVEL OF EVIDENCE

III.