Poster 336: Reliability of Preoperative MRI in the Prediction of ACL Tear Type
Authors: Darden Christon , Kantrowitz David , Bienstock Dennis , Jalloh Hulaimatu , Gladstone James , Anthony Shawn 
Published: October 2024

Objectives: Anterior cruciate ligament (ACL) tears are among the most frequent ligament injuries in the United States. Most of these injuries are treated surgically, depending on patient-specific factors. Management of these injuries includes nonoperative management with stepwise rehabilitation or surgical treatment with ACL repair or reconstruction. Patient goals, a clinical evaluation, and preoperative MRI imaging are generally assessed to inform the choice of treatment.  Classification of ACL tear-type based on stump morphology is critical to preoperative planning, as it can determine a patient’s eligibility for ACL preservation techniques. We aim to determine the efficacy of preoperative magnetic resonance imaging (MRI) in predicting ruptured ACL stump morphology and thus assist in preoperative planning and decision-making. Methods: This retrospective observational study utilized chart review from the case log of a single surgeon at an urban tertiary institution. The review identified patients who underwent the Bridge Enhanced ACL Repair (BEAR) procedure between January 1, 2022 and August 31, 2023. The inclusion criteria included patients who underwent a primary ACL repair with the BEAR technique and had adequate intraoperative and MRI images available for review. Patients excluded were those with inadequate intraoperative imaging or MRI imaging that was unavailable for review. For each patient included, the two senior authors assessed the morphology of the ACL stump on MRI (sagittal T2, coronal T2) and intraoperative arthroscopy images in a blinded manner and assigned a classification grade to each. The MRI-based morphology and the intraoperative image morphology of the tears were classified based on a system validated by DeFelice et al, which includes types 1 to 5 based on the location of the tear from most proximal to most distal. The correlation between the preoperative MRI assessment and the intraoperative arthroscopic assessment was interrogated using simple linear regression quantified with the Pearson correlation coefficient. Results: A total of 35 patients that underwent the BEAR procedure were identified. One patient was excluded due to inadequate intraoperative images. Of the remaining patients, 13 (38.2%) were male and 21 (61.8%) were female. The average patient age was 31, with a median age of 28. Most patients were injured while skiing (32.4%), while the second and third most prevalent mechanisms of injury were nonsports-related (23.4%) and soccer injuries (17.6%), respectively. Of the MRI tears that were analyzed, 9 (26.5%) were classified as type 1, 19 (55.9%) were type 2, and 5 (14.7%) were type 3. There were no tears identified as types 4 or 5 tears. Of the arthroscopic images that were analyzed, 21 (61.8%) were classified as type 1, 10 (29.4%) were type 2, 3 (8.8%) were type 3. Similarly, there were no tears identified as types 4 or 5. MRI accurately predicted the ACL tear type seen arthroscopically 55.9% (19/34) of the time. Of the (15) cases in which MRI did not correlate with the arthroscopic tear type, the MRI classification grade was within 1 grade of the arthroscopic grade 93.3% of the time (14/15). In the cases in which MRI was not correct in its grading, 93.3% of them (14/15) were classified as too high of a grade (MRI perceiving the tear to be more distal than it was in actuality). The Pearson correlation coefficient assessing the correlation between MRI identified tear type and arthroscopy identified tear type was 0.56. Conclusions: MRI accurately predicted the ACL tear type seen arthroscopically in only 55.9% of patients. In >90% of incorrect predictions, arthroscopy determined the ACL tear to be one classification more proximal than predicted by MRI. Our results demonstrate that while preoperative MRI can be useful in identifying approximate ACL tear location, it is essential to examine the ACL at time of arthroscopy for final determination of ACL stump size and viability for ACL restoration procedures. Moreover, a greater percentage of patients may be eligible for an ACL restoration procedure than predicted by preoperative MRI, highlighting the importance of discussing both ACL repair and ACL reconstruction with patients preoperatively. [Figure: see text]