Summary

The integrity and injury of the anterolateral ligament of the knee is underreported on routine MRI assessments in patients with sports-related ACL injuries and lateral compartment involvement but can be adequately visualized and characterized for improved diagnosis.

Abstract

Background

The anterolateral ligament (ALL) provides rotational knee stability and has gained growing interest in recent years. While its existence has been known for over a century, new augmentation techniques have spurred the debate on its clinical importance. Previous studies have shown that 11-30% of patients demonstrate persistent rotational instability following anterior cruciate ligament (ACL) reconstruction. The accuracy of preoperative imaging diagnosis may impact treatment decisions. The primary goal of this study was to determine the rate of ALL reporting on routine magnetic resonance imaging (MRI) and compare the results to a secondary review by a fellowship-trained musculoskeletal radiologist based on ALL visualization, and injury characterization. We hypothesized that ALL as an anatomic structure and its related injuries are underreported on routine MRI assessments.

Methods

The study was based on a retrospective review of an institutional database with records from 2015 to 2019. Inclusion criteria consisted of patients with sports-related ACL injuries treated with primary reconstructions, concomitant injuries in the lateral compartment, and existing pre-operative Magnetic Resonance Imaging (MRI) read by a musculoskeletal radiologist. Exclusion Criteria were defined as ACL revisions, chronic ACL injuries, and non-sports-related injuries. ALL visualization was defined as fully, partially or not visualized. Injury characterization was defined as Grade I: Mild or Intermediate Sprain, Grade 2: Severe Sprain or Partial Tear, and Grade III: Complete Tear or Avulsion as previously described. The primary evaluation of the complete MRI was reviewed by musculoskeletal radiologist in a setting of an acute injury. A secondary review of the same MRI was performed by another musculoskeletal radiologist with a focus on ALL integrity.

Results

Among 1544 ACL injuries, 204 met the study selection criteria. The mean age was 21.2 (13-39) years with 34% females 66% males. Most injuries occurred during recreational sports (n=90), followed by high school (n=83), college (n=29), and professional sports (n=2). The most frequent sports type was soccer (n=58), followed by football (n=57), basketball (n=41), and other sports (n=49). The ALL-visualization rate on routine MRI reports was 0% compared to the secondary review with a rate of 99.5% (203/204). 134 ALLs were fully visualized, 69 partially, and 1 was not visualized. 138 ALL injuries were missed on routine MRI reports with 27.9% characterized as grade 1, 30.4% as grade 2, and 9.3% as grade 3. Overall, 68% of patients with sports-related ACL tears demonstrated a concomitant ALL injury which was missed on the initial MRI assessment.

Conclusion

Concomitant ALL injuries are not recognized on routine MRI reports in patients with ACL tears. However, visualization and injury characterization using standard MRI protocols and grading systems can be highly effective and provide guidance for orthopedic surgical management. Education and heightened awareness of the ALL as an anatomic structure may improve the diagnostic accuracy for routine MRI reporting.