Ramp Lesion Subtypes: Prevalence, Imaging, and Arthroscopic Findings in 2156 Anterior Cruciate Ligament Reconstructions.

BACKGROUND Ramp lesions are defined as a particular type of injury within the posterior horn of the medial meniscus and its meniscocapsular attachments. Five subtypes have been described: type 1, meniscocapsular lesion; type 2, partial superior lesion; type 3, partial inferior lesion or hidden type; type 4, complete tear in the red zone; and type 5, complete double tear. PURPOSE (1) To determine the prevalence of different subtypes of ramp lesions in patients undergoing arthroscopic anterior cruciate ligament reconstruction (ACLR). (2) To describe the characteristics of ramp lesions based on imaging and diagnostic arthroscopy. STUDY DESIGN Cross-sectional study; Level of evidence, 3. METHODS All patients who underwent arthroscopic ACLRs between November 2015 and November 2018 by 2 senior surgeons at 1 institution were evaluated retrospectively (1) to describe the subtypes of ramp lesions diagnosed intraoperatively using transnotch arthroscopic exploration of the posteromedial compartment and (2) to look for any factors significantly associated with these subtypes. The following parameters were studied: demographics; history and clinical findings including time between injury and surgery, side-to-side laxity, and pivot shift; lesions missed on magnetic resonance imaging (MRI) scans and medial proximal tibial bone contusion visible on MRI scans; and arthroscopic confirmation of ramp lesion (ie, prevalence), associated lateral meniscal tear, or medial chondral tear. RESULTS Out of 2156 primary or revision arthroscopic reconstructions, 334 ramp lesions were confirmed, giving a prevalence of 15.5%. The subtype distribution was as follows: type 1, 47.9%; type 2, 4.8%; type 3, 11.4%; type 4, 28.7%; type 5, 7.2%. Multivariate analysis showed that gross pivot shift was significantly associated with complete ramp tears (odds ratio, 4.8; 95% CI, 1.7-17.2). Hidden lesions (type 3, inferior partial tear in the red zone) were the most likely to be missed on preoperative MRI (45.9%). CONCLUSION In a population undergoing ACLR, the prevalence of ramp lesions was 15.5%. Among the subtypes of ramp lesion, the most common was a meniscocapsular junction tear (type 1). Partial inferior tears (type 3) were the most likely to be missed on preoperative MRI scans. Gross pivot shift was significantly associated with complete ramp tears (types 1, 4, and 5).