gms | German Medical Science

Objectives: Concomitant injuries to the Kaplan fibres (KF), the anterolateral complex (ALC) including the anterolateral ligament and the lateral meniscus (LM) in combination with anterior cruciate ligament (ACL) tears have been linked to increased anterolateral rotatory instability (ALRI). The purpose of this prospective study was to investigate the effect of KF, ALC and LM injuries on preoperative ALRI in ACL-deficient knees. It was hypothesized that concomitant injuries lead to a higher quantitative pivot shift compared to knees with intact structures.

Methods: A prospective registry study was conducted and patients who underwent primary unilateral ACL injury within 100 days after trauma were included. Exclusion criteria contained injuries to the collateral ligaments, bucket-handle meniscus tears or foreign bodies and BMI>35 kg/m². The pivot shift test was preoperatively performed in general anaesthesia and quantified using the PIVOT iPad application by one of three principal investigators (fellowship-trained orthopaedic surgeons). In doing so the anterior translation of the lateral tibia plateau (ATLT) was measured of both the injured and uninjured knee, and side-to-side difference (SSD) was calculated. The pivot shift test was additionally graded according to IKDC criteria. Injuries to the KF, ALC and LM were diagnosed on acute preoperative magnetic resonance imaging (MRI) scans and confirmed during surgery. The patients were grouped for analysis accordingly. Student's t-test was used to compare means and statistical significance was set to p<0.05.

Results and conclusion: 109 patients with a mean age of 30.7±11.6 years were included in this study (67 male/52 female, 63 right/46 left, BMI: 25.0 ± 3.9 kg/m²). The ATLT was significantly higher in the injured knees compared to the healthy ones (2.92±1.53 mm vs. 1.66±1.00 mm, p<0.001). The quantified pivot shift was also significantly correlated with the clinical IKDC grading (r=0.39; p<0.01). Concomitant injuries to the KF, ALC, LM or a combination of the above structures had no significant effect on the SSD of ATLT during quantified pivot shift (n.s.).

In disagreement with our hypothesis, concomitant injuries to peripheral anterolateral soft-tissue structures did not significantly increase ALRI in this cohort of ACL-injured knees. Even combined injuries to those structures had no significant effect on ATLT. Based on these findings, a high-grade pivot shift cannot simply be explained by the presence of concurrent injuries but several other patient specific factors (e.g. bony morphology, hyperlaxity) need to be considered when ALRI is assessed.