Poster 219: Posterior Sagittal Position of the Tibial Tubercle as Measured by the Sagittal Tibial Tubercle – Trochlear Groove Distance Correlates with an Increased Risk for Surgery in Patients with Patellofemoral Chondral Lesions

OBJECTIVES: The etiology of isolated patellofemoral (PF) cartilage defects without patellar instability is currently incompletely understood. The purpose of the present study was to evaluate the variation in knee sagittal alignment in patients with and without PF cartilage wear. METHODS: This was a single-center, retrospective review of patients that underwent a cartilage restoration procedure for isolated PF cartilage wear from 2014-2020. Patients were matched in a 1:2:2 ratio for age, sex, and BMI to anterior knee pain diagnosis and meniscectomy procedure cohorts as controls. Exclusion criteria included knee flexion angle >10°, elevated Caton-Deschamps index (CDI>1.3), increased sulcus angle (>145°), increased patellar tilt (>5°), elevated coronal TT-TG (>15mm), varus/valgus malalignment (>5°), or ICRS patellofemoral cartilage defects of ≥3 in either control group. The sagittal TT-TG (sTT-TG) distance was measured on preoperative axial T2 magnetic resonance imaging (MRI) and was defined as the distance between a point at the nadir of the trochlear cartilage and the most anterior point of the tibial tubercle. Comparisons between the 3 groups were made using ANOVA testing with Bonferroni corrections. Reliability was assessed with the interclass correlation coefficient (ICC). Odds ratios were calculated based on a sTT-TG measurement threshold obtained from a receiver operative characteristic curve graph. RESULTS: Two hundred and thirty-five patients (47 cartilage restoration, 94 anterior knee pain, 94 meniscectomy) were included. Mean age, BMI, and height were 33.8 +/- 8.7 and 26.7 +/- 5.7, 170.6 +/- 24.3 respectively, with 130 males (55%) and 105 females (45%). There were no significant differences between groups for age, BMI or sex(p>0.05). Mean sTT-TG was significantly more posterior in the cartilage restoration group compared to the meniscectomy group (-2.5 mm +/-5.9 vs 1.72 mm +/- 5.3, p<0.001). The anterior knee pain group sTT-TG was between the meniscectomy and cartilage restoration groups, but was not significantly different from either (p=0.067, p=0.13). Interrater reliability was excellent (ICC=0.927, p<0.001). Patients with a posterior translation of -2.15 or greater were 2.12 times more likely to undergo a cartilage restoration procedure (OR 2.12, 95% CI 1.1 to 4.1). CONCLUSIONS: Cartilage restoration procedure patients had a significantly more posterior tibial tubercle than partial meniscectomy controls. Anterior knee pain patient sagittal TT-TG was between both groups, but was not significantly different from either. Patients with sTT-TG of <-2.15 mm were 2.12 x more likely to have a cartilage restoration procedure.