Preoperative Patello-femoral Alignment Affects Anterior Knee Pain After Primary Total Knee Arthroplasty Without Patellar Resurfacing.

BACKGROUND

Anterior knee pain (AKP) after total knee arthroplasty (TKA) results in dissatisfaction with the surgical outcomes. This study aimed to investigate risk factors for AKP after TKA using radiographic assessments.

METHODS

This retrospective matched-pair, case-control study included 284 patients who underwent primary fixed-bearing, posterior-stabilized TKA from 2016 to 2020, with a minimum follow-up of 2 years. The inclusion criterion was varus osteoarthritis in the knees without patellar resurfacing. The exclusion criteria were the use of bone graft or metal block, valgus knees, and patellar resurfacing. The patellar tilt angle, lateral patello-femoral angle, length of the tibial tuberosity to the trochlear groove, hip-knee-ankle angle, patellar height, and trochlear dysplasia index were measured. Patients were divided into 2 groups according to the presence of AKP based on the Feller score (≤ 20 points) at a 2-year follow-up, then a 1:2 propensity matching was performed. Risk factors for AKP were identified through logistic regression analyses. A total of 135 patients were enrolled in this study after matching.

RESULTS

The preoperative patellar tilt angle, lateral patello-femoral angle, tibial tuberosity to the trochlear groove, and trochlear dysplasia index significantly differed between the groups (P < 0.05), but not the postoperative parameters (P > 0.05). The Western Ontario and McMaster Universities total score and Feller score were significantly different postoperatively. (P < 0.05) Logistic regression analyses revealed that the preoperative patellar tilt angle, preoperative trochlear dysplasia index, and preoperative lateral patellofemoral angle were significant risk factors.

CONCLUSIONS

Care should be exercised when performing TKA in patients who have a large patellar tilt angle, a small lateral patello-femoral angle, and a small trochlear dysplasia index preoperatively, as there can be an increased risk of postoperative AKP in TKA with unresurfaced patellae. Surgeons may consider counseling patients about their increased risk of AKP if these factors are present preoperatively.

LEVEL OF EVIDENCE

Ⅲ.