Patellar Tendon-Lateral Trochlear Ridge Distance Is More Specific Than Tibial Tubercle-Trochlear Groove for Patellofemoral Instability.
Abstract
Purpose
To assess the reliability, predictability, and discriminative capacity of 3 anatomic measurements, tibial tubercle-trochlear groove (TT-TG), tibial tubercle-posterior cruciate ligament, and patellar tendon-lateral trochlear ridge (PT-LTR), where PT-LTR may offer a complementary approach to assessing recurrent patellofemoral instability (PFI) risk.
Methods
Patients diagnosed with PFI before primary patellofemoral stabilization surgery at a single institution between 2022 and 2024 were included. A control group without PFI was propensity matched 1:1 for age, sex, and laterality. Magnetic resonance images were evaluated to measure TT-TG, tibial tubercle-posterior cruciate ligament, and PT-LTR. A priori power analysis determined the cohort size. Statistical analyses compared differences between the PFI and control groups with Student t-tests, receiver operating characteristic analyses, and area under the curve with resultant sensitivity, specificity, and an optimal cutoff.
Results
Patients included 50 knees with PFI (28 women, 22 men; mean age 18 ± 5 years). The control group included 50 knees (27 women, 23 men; mean age 18 ± 4 years). Excellent inter- and intra-rater reliability (intraclass correlation coefficient > 0.7) was shown for TT-TG and PT-LTR in the PFI and control groups. The distances for TT-TG, tibial tubercle-posterior cruciate ligament, and PT-LTR were significant predictors (P ≤ .025) of PFI. The average PT-LTR distance difference for the PFI and control groups was 7.0 mm (P < .001). PT-LTR showed an area under the curve of 0.80 and, when ≥4.6 mm, was 66% sensitive and 92% specific for PFI.
Conclusions
The PT-LTR distance is a reliable and discriminative metric for identifying PFI in both pediatric and adult populations. A PT-LTR cutoff value of 4.6 mm showed diagnostic discrimination and substantially high specificity for recurrent PFI, indicating strong ability to identify patients with instability. LEVEL OF EVIDENCE Level III, retrospective case control study.