Reliability of Tibial Tubercle–Trochlear Groove Distance for Assessing Tibial Tubercle Lateralization: A Study Comparing Different Anatomic References

Background: The tibial tubercle–trochlear groove (TT-TG) distance is a measurement used to quantitatively assess tibial tubercle lateralization (TTL), and it has important reference value for the treatment of patellar dislocation (PD). However, TT-TG distance accuracy has been questioned, so many new parameters have been proposed. Purpose: To compare which of the TT-TG, tibial tubercle–midepicondyle (TT-ME), tibial tubercle–Roman arch (TT-RA), tibial tubercle–tibial intercondylar midpoint (TT-TIM), and tibial tubercle–mid inter-epicondyle trochlea intersection (TT-MIELTI) distances better reflect TTL in patients with PD. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: A total of 96 patients who had undergone surgery for PD and 96 patients without PD (controls) were included in the study. The patients had all undergone computed tomography examination. The TT-TG, TT-ME, TT-RA, TT-TIM, TT-MIELTI distances and the TTL distance were measured independently by 2 surgeons in a blinded and randomized fashion. The t test was used to detect whether the parameters were significantly different between the 2 groups. The TTL distance was used as a reference value for lateralization of tibial tubercle. Pearson correlation coefficients were calculated to determine correlations between the defined measurements. Results: The intra- and interobserver reliability of the defined measurements was excellent. All parameters except for TT-TIM distance were significantly larger in the PD group than the control group ( P < .01 for all). There was a moderate correlation ( r = 0.601) between the TT-TG distance and TTL, and other parameters were less correlated with TTL. Conclusion: Among 5 the parameters tested, the TT-TG distance still had the highest correlation with TTL and was able to reflect TTL better in patients with PD. The role of TT-TIM distance in the assessment of PD needs further study.