The Tibial Tubercle‐Trochlear Groove Distance Has Higher Accuracy and Moderate Inter‐observer Reliability Compared With the Tibial Tubercle‐Roman Arch and Tibial Tubercle‐Midepicondyle Distances

PURPOSE: To assess the interobserver reliability of the assessment of the tibial tubercle-trochlear groove (TT-TG) distance, tibial tubercle-Roman arch (TT-RA) distance, tibial tubercle-midepicondyle (TT-ME) distance, and tibial tubercle-posterior cruciate ligament (TT-PCL) distance; to compare the diagnostic value of imaging parameters for detecting pathological tibial tubercle lateralization; and to analyze whether the TT-PCL distance has diagnostic value. METHODS: Patients with patellar dislocation and with meniscus injury or anterior cruciate ligament injury admitted to our hospital from January 2019 to July 2025 were retrospectively reviewed. The TT-TG distance, TT-RA distance, TT-ME distance, and TT-PCL distance between the meniscus injury or anterior cruciate ligament injury (control group) and patellar dislocation (case group) were compared using the unpaired t-test or Mann-Whitney U test. The receiver operating characteristic curve was used to calculate the area under the curve, diagnostic threshold, sensitivity, and specificity for the TT-TG distance, TT-RA distance, and TT-ME distance. Three observers measured all parameters, and the intraclass correlation coefficient (ICC) was used to assess interobserver reliability. RESULTS: Magnetic resonance imaging was obtained from 50 patients with the clinical diagnosis of patellar dislocation and from 50 patients with meniscus injury or anterior cruciate ligament injury. Regarding age, sex, and side of injury, there were no statistically significant differences between the 2 groups (P > .05). The TT-TG distance [(18.02 ± 3.02) mm], TT-RA distance [(21.49 ± 3.67) mm], and TT-ME distance [(15.63 ± 3.88) mm] in the case group were significantly different from the TT-TG distance [(10.52 ± 3.00) mm], TT-RA distance [(14.18 ± 3.30) mm], and TT-ME distance [(8.85 ± 3.37) mm] in the control group (P < .001). The TT-PCL distance, however, showed no statistically significant difference between the groups: 21.45 (18.87, 22.76) mm (cases) versus 20.02 (18.29, 22.67) mm (controls) (P > .05). The area under the curve was 0.965 for the TT-TG distance, 0.936 for the TT-RA distance, and 0.904 for the TT-ME distance. All interobserver reliability ICC values for the TT-TG distance were greater than 0.75; all interobserver reliability ICC values for the TT-RA distance were greater than 0.85, and all interobserver reliability ICC values for the TT-ME distance were greater than 0.85. CONCLUSIONS: The TT-TG distance has lower interobserver reliability than the TT-RA and TT-ME distances. The TT-PCL distance does not differ between patients with patellar dislocation and those without. LEVEL OF EVIDENCE: Level III, retrospective comparative case series.