Prevalence and Classification of Injuries of Anterolateral Complex in Acute Anterior Cruciate Ligament Tears

PURPOSE: To report on the prevalence of injuries of the lateral compartment occurring in cases of apparently isolated acute anterior cruciate ligament (ACL) tears and to present a classification system of anterolateral complex injuries based on the data obtained. METHODS: Sixty patients operated on for an acute apparently isolated ACL tear, revealed by clinical examination and confirmed by magnetic resonance imaging, were prospectively selected. The lateral compartment was exposed and injuries were detected. Based on the data obtained, lesions of the anterolateral complex were classified as follows: Type I: multilevel rupture with individual layers torn at different levels with macroscopic hemorrhage involving the area of the anterolateral ligament (ALL) and extended to the anterolateral capsule. Type II: multilevel rupture with individual layers torn at different levels with macroscopic hemorrhage extended from the area of the ALL and capsule to the posterolateral capsule. Type III: complete transverse tear involving the area of the ALL near its insertion to the lateral tibial plateau, distal to the lateral meniscus. Type IV: bony avulsion (Segond fracture). The pivot-shift test was repeated intraoperatively after repair of lateral tears before the ACL reconstruction. RESULTS: Although magnetic resonance imaging was able to detect only bony injuries (Segond fracture), macroscopic tears of the lateral capsule were clearly identified at surgery in 54 of 60 patients and classified as follows: Type I: 19/60 Type II: 16/60 Type III: 13/60 Type IV: 6/60 In all cases, repair resulted in a marked reduction or apparent disappearance of the pivot-shift phenomenon. Statistical analysis showed a positive correlation between lesions of the lateral compartment, regardless of the type described, and a pivot shift graded 2 or 3. CONCLUSIONS: Because injuries of secondary restraints often occur in cases of acute ACL tears, recognition and repair of such lesions could be considered to help ACL reconstruction to better control rotational stability. LEVEL OF EVIDENCE: Level IV, therapeutic case series.