High-grade trochlear dysplasia is associated with a more negative sagittal tibial tuberosity-trochlear groove distance: A retrospective cohort study.

Purpose: To identify demographic or radiographic predictors of sagittal tibial tuberosity-trochlear groove (sTT-TG) distance utilizing a cohort of patellofemoral surgical patients.

Methods: Patients who underwent an osteochondral allograft (OCA) transplantation or autologous chondrocyte implantation (ACI) from 2010 to 2020 were included if they had patellofemoral high-grade lesions and preoperative magnetic resonance imaging (MRI). Patient demographics, radiographic measurements such as coronal TT-TG, Caton-Deschamps index (CDI), and trochlear dysplasia were recorded. The preoperative sTT-TG distance was measured independently on axial T2-weighted MRI sequences by two authors at least two weeks apart. An interclass correlation coefficient (ICC) was calculated to assess intra- and inter-rater reliability of sTT-TG measurements, and univariate and multivariable linear regression models were used to assess the relationship between sTT-TG and any demographic or radiographic predictors.

Results: Seventy-three knees composed of 44 females and 29 males with a mean age of 31.0 ± 10.1 years, a mean BMI of 26.8 ± 6.1, and a mean follow-up of 60.4 ± 21.0 months were included. Thirty-four of these (46.6 %) underwent OCA transplantations and 39 (53.4 %) underwent ACI/MACIs. Thirty-one (42.4 %) knees were determined to have evidence of trochlear dysplasia. Twenty-four patients were found to have high grade trochlear dysplasia (grades B, C and D) and 7 patients were found to have low grade trochlear dysplasia (grade A). The mean sTT-TG of the entire cohort was -5.3 ± 4.9 mm. Interobserver reliability for sTT-TG measurements was excellent with an ICC of 0.95 (0.927-0.969, p < 0.001). There was a significant difference in sTT-TG between patients who had no trochlear dysplasia, low-grade trochlear dysplasia and high grade trochlear dysplasia (-3.51 ± 3.96 vs. -6.17 ± 4.29 vs. -9.25 ± 5.32, p < 0.001). On multivariate regression, trochlear dysplasia remained the only significant predictor of sTT-TG (β = -2.25, p = 0.005). Post-hoc analysis showed that both low- and high-grade dysplasia were associated with significantly more negative sTT-TG values compared to patients without dysplasia, though no significant difference was observed between the low- and high-grade groups.

Conclusion: Trochlear dysplasia was associated with a more negative sagittal tibial tuberosity-trochlear groove (sTT-TG) distance, with increasing severity of trochlear dysplasia correlated with a relatively more posterior tibial tuberosity.

Level of evidence: Level III; diagnostic cross-sectional study.