More negative sagittal tibial tuberosity-trochlear groove distances are correlated with larger patellofemoral chondral lesion size.

Purpose: The purpose of this study is to assess the association between sagittal tibial tuberosity-trochlear groove (sTT-TG) distance and patellofemoral chondral lesion size in patients undergoing cartilage restoration procedures.

Methods: A retrospective cohort analysis of patients who underwent an osteochondral allograft transplantation or matrix-induced autologous chondrocyte implantation in the patellofemoral compartment, from 2010 to 2020, were included if they had patellofemoral high-grade lesions, magnetic resonance imaging (MRI) and minimum 2-year follow-up. The preoperative sTT-TG distance was measured independently on axial T2-weighted MRI sequences by two authors, each at least two weeks apart. Intraoperative lesion size was reported according to operative report measurements by the attending surgeon. An interclass correlation coefficient (ICC) was calculated to assess intra- and inter-rater reliability, and categorical data analysis and linear regression models were used to assess the relationship between sTT-TG and lesion size.

Results: A total of 80 patients (50 females) with a mean age of 31.5 ± 10.4 years, body mass index of 27.0 ± 5.9 kg/m and follow-up of 61.5 ± 21.4 months were included. A total of 107 lesions were present: 63 patients with unipolar (patella = 41, trochlea = 22) and 22 with bipolar lesions. The mean MRI defect size was 1.6 ± 1.0 cm and the mean intraoperative defect size was 3.8 ± 2.4cm. Intra- (ICC: 0.99,0.98) and inter-rater reliability (ICC: 0.96) were excellent for both MRI defect size and sTT-TG measurements. The mean sTT-TG was -4.8 ± 4.9 mm and was significantly inversely related to MRI defect size (-0.45, p < 0.01), intraoperative patellar lesion size (-0.32, p = 0.01), total lesion area (-0.22, p = 0.04), but not trochlear lesion size (-0.09, p = 0.56). Multivariable regression demonstrated a more negative sTT-TG remained an independent variable correlated with larger MRI-measured patellofemoral defect sizes and intraoperative patellar lesions.

Conclusion: A more negative sTT-TG was an independent variable correlated with larger patellofemoral lesions in patients undergoing patellofemoral cartilage restoration.

Level Of Evidence: Level III, Diagnostic.