Reliability of Preoperative MRI in the Prediction of ACL Tear Type.

Abstract

Background: Anterior cruciate ligament (ACL) injuries are common among active patients and can be managed with primary repair or reconstruction. The most important predictor of good outcomes after primary repair is a more proximal tear location. Preoperative magnetic resonance imaging (MRI) guides surgical decision making, but the accuracy of MRI in identifying tear location is understudied.

Purpose: To evaluate the accuracy of preoperative MRI in identifying ACL tear location.

Study design: Cohort study (diagnosis); Level of evidence, 2.

Methods: Patients who underwent ACL reconstruction or repair by 2 surgeons at a single, urban academic medical center between 2019 and 2024 were collected. Exclusion criteria included previous ACL surgery and inadequate preoperative or intraoperative imaging. The location of the ACL tear on preoperative MRI scan was retrospectively graded using the modified Sherman classification in a blinded manner. Reference diagnosis was the tear location as noted in the surgeon's operative note and confirmed with arthroscopic images. The primary endpoint was the accuracy of MRI for predicting intraoperative tear type.

Results: A total of 203 patients were included in this study. MRI accurately predicted the ACL tear type seen arthroscopically only 35.5% (72/203) of the time. When MRI did not match the arthroscopic diagnosis, the MRI was within 1 classification grade 74.8% (98/131) of the time. Of the incorrect gradings, 71.0% (93/131) were overclassifications (MRI tear classification more distal than found during arthroscopy). MRI was more sensitive in detecting proximal third (type II) and midsubstance (type III) tears (43.7% and 51.6%, respectively) than it was for detecting proximal avulsion (type I) tears (2.5%).

Conclusion: MRI was unreliable for determining the precise location of an ACL tear. MRI tended to overestimate how distal a tear was compared with arthroscopic findings, which may influence patient counseling, preoperative planning, and surgical decision making.