Radiologic Measurement of Tibial Tuberosity-Trochlear Groove (TT-TG) Distance by Lower Extremity Rotational Profile Computed Tomography in Koreans

BACKGROUND: Tibial tuberosity-trochlear groove (TT-TG) distance is important in the assessment and treatment of patellofemoral disorders. However, normal and pathological TT-TG values have not been established in Koreans. The purpose of this study was to evaluate the TT-TG distance in the Korean population using lower leg rotational profile computed tomography (CT) scans. METHODS: One hundred rotational profile CT scans were retrospectively collected from patients without knee joint problems aged between 25 to 82 years. TT-TG distances were measured, and statistical analysis was performed. Each CT scan was measured twice in a blinded, randomized manner by three reviewers. Patients with pre-existing knee joint problems were excluded from the study; hence 15 of the 100 patients were excluded because of deformity or unreadable CT scans. Thus, 85 of the 100 patients were included in the study. RESULTS: Interobserver and intraobserver reliability of TT-TG distance measurements was good. The median TT-TG distance for this Korean population was 11.24 mm (mean, 10.24 ± 0.8 mm). TT-TG distance measured nearly 2 mm less on rotational profile CT scans. CONCLUSIONS: Some of the TT-TG distances on rotational profile CT scans were significantly correlated, indicating that they could be accepted. Furthermore, the values on CT scans showed good reliability. In this study, the TT-TG distance in normal Korean people was approximately 10.24 mm without significant differences in TT-TG values between genders.