Weight‐bearing computed tomography reveals greater anterior tibial translation and femorotibial rotation than magnetic resonance imaging in chronic anterior cruciate ligament deficiency: A prospective observational study

PURPOSE: To compare anterior tibial translation and femorotibial rotation measurements obtained from conventional supine, non-weight-bearing magnetic resonance imaging (MRI) and weight-bearing computed tomography (WBCT) in patients with chronic anterior cruciate ligament (ACL) tears. METHODS: WBCT of the knee acquired in full extension and at 30° of flexion was prospectively compared with conventional supine, non-weight-bearing MRI in patients with chronic ACL tears. Medial and lateral anterior tibial translation and femorotibial rotation were measured across imaging modalities and knee positions. Associated intra-articular and peripheral lesions were assessed on MRI. Statistical comparisons were performed using Friedman's test with Sidak post hoc analysis, and effect sizes were calculated using Cohen's d. RESULTS: Twenty-three patients with chronic ACL tears (8-24 months) were included. Mean lateral anterior tibial translation was significantly greater on WBCT at 30° of flexion compared with MRI (8.6 ± 3.4 mm vs. 4.0 ± 3.6 mm; p < 0.001), demonstrating a large effect size, with no difference in extension (3.1 ± 3.4 mm; p = 0.705). Medial anterior tibial translation was higher on WBCT in extension than on MRI (6.0 ± 3.0 mm vs. 3.1 ± 2.4 mm; p = 0.003), with no difference at 30° of flexion. Femorotibial rotation was greater on WBCT at 30° of flexion (12.0 ± 5.6° vs. 7.3 ± 5.5°; p < 0.001) and lower in extension (3.6 ± 4.7° vs. 7.3 ± 5.5°; p = 0.002), both with large effect sizes. CONCLUSION: Anterior tibial translation and femorotibial rotation measurements differed between MRI and WBCT, with load-bearing imaging revealing greater, position-dependent measured values under weight-bearing conditions. These findings suggest that WBCT may provide clinically relevant information on functional instability that complements MRI and may assist in preoperative assessment and surgical planning in patients with chronic ACL deficiency. LEVEL OF EVIDENCE: Level III.