Work

Underestimation of tibial tuberosity–trochlear groove distance in conventional knee magnetic resonance imaging compared to full‐extension imaging

Year: 2025

Type: article

Abstract: PURPOSE: To assess the effect of the knee flexion on the tibial tuberosity-trochlear groove (TT-TG) distance measurement by comparing conventional and whole-leg rotational magnetic resonance imaging (MRI). METHODS: This retrospective cohort study included 45 patients with patellar dislocations who had undergone both conventional knee MRI with the knee in slight knee flexion (20°-30°) and full-length rotational MRI in extension (0°-5°). TT-TG distances were determined by two independent observers using standardised landmarks. Measurement reproducibility was evaluated using intraclass correlation coefficients (ICCs) for both intra and interrater reliability (3-month interval). RESULTS: TT-TG distance values derived from conventional MRI were significantly smaller (13.4 ± 4.0 mm, 95% confidence interval [CI]: 12.2-14.6) compared to those from whole-leg rotational MRI (18.3 ± 4.4 mm [95% CI: 16.9-19.6]), yielding a mean difference of 4.8 ± 3.0 mm (95% CI: 3.9-5.8; p < 0.001). Both interrater (conventional MRI: ICC = 0.946 [95% CI: 0.901 - 0.971]; rotational MRI: ICC = 0.949 [95% CI: 0.899-0.973]) and intrarater reliability (conventional MRI: ICC = 0.995 [95% CI: 0.992-0.997]; rotational MRI: ICC = 0.991 [95% CI: 0.983-0.995]) were excellent across modalities. CONCLUSION: Conventional knee MRIs, performed with knee in slight flexion, are consistently smaller compared to those acquired in full extension whole-leg rotational MRI. Knee flexion, therefore, leads to a systematic underestimation of the TT-TG distance. Standardising knee position during imaging is essential to ensure accurate and comparable TT-TG assessments. LEVEL OF EVIDENCE: Level II, cohort study (diagnosis).

Source: Knee Surgery Sports Traumatology Arthroscopy

DOI: 10.1002/ksa.70237