Poster 270: Joint Preservation and Complications of Tibial Tubercle Osteotomy at a Minimum of 5- Year Follow-up

OBJECTIVES: To report the incidence of complications after TTO at a minimum of 5-year follow-up. As a secondary outcome, we aimed to identify predictors of postoperative complications. As a tertiary outcome, we aimed to report the rate of progression of knee osteoarthritis. We hypothesized that recurrent instability following TTO is rare and the rate of progression of knee osteoarthritis is slow METHODS: Patients undergoing primary TTO between January 1, 2010, and December 31, 2015, and having a minimum of 5-year clinical follow-up data were included. Exclusion criteria were patients with shorter than 5-year follow-up, revision TTO, TTO following total knee arthroplasty, concomitant anterior cruciate ligament reconstruction, history of or concomitant distal femoral osteotomy, history of soft tissue procedures or trochleaplasty for patellar instability, congenital patella dislocation or patellar instability secondary to a congenital disorder/syndrome. Clinical and radiographic outcomes were collected on a RedCAP database. Risk factors for complications were identified using multivariable logistic regression analysis. RESULTS: A total of 72 (50 female/22 male) patients were included in the analysis. The median age was 22.0 years. The mean follow-up period was 104.8 months (67-138). Sixty-four patients underwent anteromedialization TTO and 8 underwent medialization TTO. The median BMI was 26.4 kg/m(2). Sixty-six patients had isolated TTO, and 11 patients had TTO and concomitant medial patellofemoral ligament reconstruction. One screw was used in 5 patients and 2 screws in 67 patients. Tibial tubercle was distalized in 25 patients and not distalized in 47 patients. Fifty-six patients reported they never smoked before their surgery and 15 patients reported they smoked at some point in their lives before the surgery. The overall complication rate was 30.5% (22/72). The incidence of major complications was 6.9%. Univariate logistic regression analysis on complications revealed patients who ever smoked are more likely to experience a postoperative complication (OR=4.33 (1.29, 14.53), p-value = 0.018). Multivariable model for complication, using TTO Procedure as the main predictor revealed TTO procedure (TTO vs TTO+STP), number of screws, and distalization didn’t affect complication rates. Multivariable model for complication, using TTO Technique (AMZ vs MZ) as the main predictor, revealed no difference in TTO technique. The mean radiographic follow-up was 67 moths. The preoperative rate of patients with Kellgren-Lawrence grade III-IV increased from 11.7% to 18.8% at the last follow-up. The rate of patients with an osteophyte on knee radiographs was 33.3% before surgery and increased to 39.1% at the last follow up. Of 72 patients, 12 were athlete. Rate of return to sports was 91.6% (11/12) after TTO procedure. Mean time to return to sports was 27.6±10.2 weeks. CONCLUSIONS: Tibial tubercle osteotomy is a viable option for the treatment of patellar instability with low recurrence and major complication rates at mid and long-term follow-up. It successfully prevents and slows the progression of knee osteoarthritis by changing the contact biomechanics. Patients who smoke should be counseled about the increased risks of complications before the surgery.