Complete ACL injuries are associated with higher static tibial subluxation than partial ACL injuries or intact ACLs measured on MRI.

Harmes, Johannes C; Ubl, Steffen T; Koch, Evamaria; Bouillon, Bertil; Günther, Daniel; Pfeiffer, Thomas R · J Exp Orthop · 2025

retrospective_cohort · Level III

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Abstract

To investigate static tibial subluxation on magnetic resonance imaging (MRI) as a potential method to quantify rotatory knee instability and differentiate between complete anterior cruciate ligament (ACL) injuries, partial ACL injuries, and intact ACL. Consecutive patients who underwent knee arthroscopy between 2016 and 2021 were retrospectively reviewed and divided into two groups according to arthroscopically verified ACL status: partial (p-ACL-I) or complete ACL injury (c-ACL-I). Patients with p-ACL-I required ACL-augmentation. The control group with an intraoperatively confirmed intact ACL (i-ACL) and a meniscus injury was 1:1 matched to p-ACL-I considering age, sex and body mass index (BMI). Static tibial subluxation in the medial (MC) and lateral compartment (LC) was measured on preoperative MRI. Intraclass correlation coefficients (ICC) were calculated for inter- and intrarater reliability. Pairwise <i>t</i>-test and multivariate logistic regression were used to identify differences with significance set at <i>p</i> < 0.05. The final analysis included 136 patients, 30 patients with p-ACL-I (8 female, 28 ± 10 years, BMI 27 ± 5 kg/m<sup>2</sup>), 24 patients with an i-ACL (6 female, 34 ± 11 years, BMI 28 ± 5 kg/m<sup>2</sup>) and 82 patients with c-ACL-I (26 female, 27 ± 11 years, BMI 26 ± 5 kg/m<sup>2</sup>). The static tibial subluxation was found to be greater in c-ACL-I (MC: 2.5 mm, LC: 6.8 mm) compared with the p-ACL-I (MC: -0.6 mm, LC: 1.7 mm) both in the MC and LC (<i>p</i> < 0.001). The static anterior tibial subluxation was greater in p-ACL-I (-1.1 mm) compared with i-ACL (-4.1 mm) in the MC (<i>p</i> = 0.01). However, no significant difference between p-ACL-I (1.6 mm) and i-ACL (0.9 mm) was found in the LC (<i>p</i> = 0.90). Intra- and interrater reliability analysis showed good to excellent agreement (ICC = 0.75-0.90). Residual fibres in p-ACL-I stabilized static anterior tibial translation. Preoperative static MRI subluxation measurement may help to differentiate between c-ACL-I and p-ACL-I who require surgical intervention, as an adjunct to the decisive dynamic examination of knee instability. Level III.