Predictors of post-operative decline in knee flexion after cruciate-retaining total knee arthroplasty

Purpose

This study aimed to identify risk factors associated with deterioration in knee flexion range of motion (ROM) following cruciate-retaining total knee arthroplasty (CR-TKA).

Methods

A total of 129 consecutive patients who underwent CR-TKA and completed a 2-year follow-up were included. A decrease of ≥9° in flexion ROM was considered clinically significant. Patients were classified into two groups based on the change in flexion ROM at 2 years post-operatively: Group D (≥9° decrease; n = 44) and Group C (<9° decrease; n = 85). Demographic data were compared using Student's t test or Fisher's exact test. Logistic regression analysis was performed to identify factors associated with ROM deterioration. Receiver operating characteristic (ROC) curve analysis was conducted to determine cut-off values for the identified factors.

Results

Demographic characteristics were comparable between the two groups. Preoperative flexion ROM was significantly higher in Group D than in Group C (128.6 ± 9.5° vs. 115.5 ± 12.3°, p < 0.001). Logistic regression analysis revealed that greater preoperative flexion ROM (odds ratio [OR], 1.18; 95% confidence interval [CI], 1.10–1.27; p < 0.001), a larger distal medial femoral resection (DMFR) (OR, 1.98; 95% CI, 1.14–3.43; p = 0.015) and lower anterior-posterior translation at 30° of flexion 1 year post-operatively (1y30AP) (OR, 0.73; 95% CI, 0.57–0.93; p = 0.012) were independently associated with a ≥9° reduction in flexion ROM. ROC analysis identified cut-off values of >130.0° for preoperative flexion ROM (AUC: 0.80, 95% CI: 0.72–0.88), >7.5 mm for DMFR (AUC: 0.60, 95% CI: 0.50–0.71) and <5.1 mm for 1y30AP (AUC: 0.62, 95% CI: 0.51–0.72).

Conclusions

Preoperative flexion ROM, DMFR and 1y30AP were associated with worse flexion ROM at 2 years following CR-TKA.

Level of Evidence

Level III, retrospective comparative study.