The Reliability of Classifying the Morphology of Anterior Cruciate Ligament Remnants during Surgery

Arthroscopic classification of the torn anterior cruciate ligament (ACL) morphology is fundamental for clinical studies on emerging techniques such as repair and preservation. At present, the most acknowledged classification is Crain description of four morphological patterns. The purpose of the study was to analyze the intra- and interobserver reliability of Crain classification in patients undergoing ACL reconstruction surgeries. The study included 101 patients who had ACL reconstruction surgery between the years 2014 and 2017. The morphological pattern of ACL remnant scar formation during surgery was observed and classified according to Crain by three orthopaedic surgeons. Inter- and intraobserver reliabilities were measured using kappa statistics. Intraobserver reliability for the Crain classification ranged from 0.63 to 0.83 (substantial to almost perfect agreement). Interobserver reliability was 0.51 (moderate agreement). In almost a third of the cases, observers reported on additional morphological pattern of scar formation that was not well defined by Crain. A modified classification of four patterns was suggested: (A) without scar tissue, (B) with adhesion to the femoral notch (wall or roof), (C) with adhesion to the notch and posterior cruciate ligament (PCL), and (D) with adhesion to the PCL. Reanalysis of these four morphological configurations resulted in interobserver reliability of 0.82 (almost perfect agreement). In conclusion, the Crain classification of torn ACL remnant morphology has moderate interobserver reliability; however, a suggested classification with modified and additional configurations has almost perfect reliability and may be useful for studies on ACL repair and preservation.