Tibial Tuberosity Anteromedialization for Patellofemoral Chondral Disease: Prognostic Factors

Abstract

Background: Tibial tuberosity anteromedialization (TTA) is a well-established treatment option for patellofemoral chondral disease that is resistant to nonoperative treatment. However, the prognostic factors of this procedure are unknown. Purpose: To analyze the prognostic factors correlated with the midterm outcomes of TTA for patellofemoral chondral disease and determine the survivorship. Study Design: Case series; Level of evidence, 4. Methods: Indications of TTA for chondral disease included skeletal maturity, age <65 years, <grade 3 Kellgren-Lawrence degeneration, and isolated patellofemoral pain for ≥6 months despite nonoperative treatment. Inclusion criteria were (1) patellofemoral chondral disease, (2) TTA with or without lateral release, and (3) minimum 2-year follow-up. Exclusion criteria were (1) previous knee surgeries, (2) previous patellar dislocations, (3) inflammatory/rheumatic conditions, (4) major combined procedures other than lateral release, (5) focal chondral lesions amenable to cartilage repair, and (6) severe trochlear dysplasia. The patients were prospectively evaluated radiographically and clinically using the Western Ontario and McMaster Universities Osteoarthritis Index–Short-Form (WOMAC-SF) and Kujala scores. Different clinical and radiological data were collected (preoperative, intraoperative, and postoperative) and correlated with the outcomes using multiple logistic regression. The Kaplan-Meier survivorship was also evaluated. Results: From January 2003 to December 2013, among 76 eligible patients, 69 patients (78 knees, 74.4% female) were included, with a mean follow-up of 67.9 ± 34.5 months (range, 24-163 months) and a mean age at the time of surgery of 43.5 ± 16.1 years. The mean preoperative WOMAC-SF (17.8 ± 5.3) and Kujala (49.3 ± 15.6) scores significantly ( P < .001) improved after surgery (WOMAC-SF: 6.6 ± 6.9; Kujala: 74.2 ± 20.5). The patients graded their operated knee as 7.2 ± 2.1 of 10 points, on average, and stated that they would undergo the surgery again in 58 (74.4%) cases. A WOMAC-SF score of >7 points (34.6% of knees) in the multiple regression model was associated with age >45 years (odds ratio [OR], 10.4; 95% CI, 2.0-55.0) and increased femoral anteversion (OR, 7.9; 95% CI, 1.4-44.1). A Kujala score of <80 points (61.5% of knees) was associated with age >45 years (OR, 12.0; 95% CI, 2.6-56.2) and foot pronation (OR, 5.1; 95% CI, 1.3-20.4). Patient satisfaction of <7 of 10 points (32.1% of knees) was associated with positive postoperative patellofemoral crepitus (OR, 3.6; 95% CI, 1.1-11.7). The Kaplan-Meier survivorship of TTA with dissatisfaction (<5/10 points) as an end point was 94% at 43 months, 88% at 77 months, and 77% at 108 months. Conclusion: Overall, good outcomes and survivorship (77% at 108 months) were obtained in this case series. However, 25.6% of the patients would not undergo the surgery again. Increased age, increased femoral anteversion, foot pronation, and postoperative patellofemoral crepitus were identified as negative prognostic factors.