Poster 266: Sagittal Tibial Tubercle-Trochlear Groove Distance Predicts Patellofemoral Chondral Lesion Size and Is Associated With Postoperative Complications

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Objectives: The purpose of this study was to assess the association between sagittal tibial tubercle-trochlear groove (sTT-TG) distance and patellofemoral chondral lesion size in patients undergoing cartilage restoration procedures. Methods: A retrospective review of patients who underwent an osteochondral allograft (OCA) transplantation or autologous chondrocyte implantation (ACI) was conducted. Patients were included if they had an articular cartilage lesion located in the patella, trochlea, or both (bipolar lesions). Lesion size of individual patella and trochlear lesions were measured intra-operatively at implantation. Total lesion area was calculated as a sum of all present chondral lesions in the patellofemoral joint. The preoperative sTT-TG distance was measured independently on magnetic resonance imaging (MRI) by 2 authors and an Interclass Correlation Coefficient (ICC) was calculated. Categorical and linear regression models accounting for demographic variables and sTT-TG distance were used to assess the relationship between sTT-TG and lesion size. Results: Eighty patients (85 knees) composed of 50 women (mean age: 31.5±10.4 years) were included. Forty-one patients underwent OCA transplantation and 44 underwent ACI. Intra-rater (ICC: 0.99, 0.98) and inter-rater reliability (ICC: 0.96) were excellent for sTT-TG measurements. A bivariate correlation analysis demonstrated that sTT-TG was significantly inversely related to MRI defect size (-0.45, p<0.01). Similarly, sTT-TG was inversely related to patellar lesion size and total lesion area, but not trochlear lesion size (Table 1). When controlling for demographics, a more negative sTT-TG remained an independent predictor of larger defects on MRI and patellar lesions: 9.3 mm2 and 9.8 mm2 lesion size increase on MRI (p<0.001) and intraoperatively (p=0.01), respectively, for every 1 mm decrease in sTT-TG. For every 1 mm increase in sTT-TG, the risk of all complications occurring decreased by 14.1% (ß=0.859, p=0.007). Conclusions: In this cohort of patients undergoing patellofemoral cartilage restoration, a more negative sTT-TG distance is a predictor of larger patellar lesions and increased risk for all complications.