2015 ISAKOS Biennial Congress ePoster #1235

Biomechanical Implications of Posteromedial Meniscocapsular Separation on ACL Strain And Tibia Translation

Cory M. Edgar, MD, PhD, Farmington, CT UNITED STATES
James Kristpher Ware, MD, Farmigton, CT UNITED STATES
Connor Ziegler, MD, Farmington, CT UNITED STATES
Robert A. Arciero, MD, Farmington, CT UNITED STATES
University of Connecticut, New England Musculoskeletal Intitute, Farmigton, CT, USA

FDA Status Cleared

Summary: Posterior-medial meniscocapsular lesions lead to a significant increase in anterior tibia translation and ACL strain at 30, 60 and 90 compared to native state, which improves with arthroscopic repair.

Abstract:

Introduction

Rupture of the anterior cruciate ligament (ACL) tears is highly associated with concomitant meniscus pathology, the majority localized within the posterior horn1-3 There exists a unique type of peripheral posterior horn medial meniscus injury occurs at the meniscocapsular junction, so called “ramp lesion”.4-6 It’s reported prevalence has a large range 3.1-16.8%, but it is highly associated with ACL rupture and found at the time of reconstruction. Increased awareness of this lesion begs the question of its importance and if repair is clinically necessary to support ACL reconstructions. The purpose of this presentation is to provide a comprehensive review of the lesion to include research done on the biomechanical importance, the prevalence in a consecutive series of 337 patients from a single surgeon, the mri detection sensitivity and a repair technique with review of anatomy based on cadaver dissection.

Methods

Eight fresh cadaver knees, age < 45, without evidence of meniscus damage determined by arthroscopy were utilized for testing (6F, 2M). A differential variable reluctance transducer was placed in the ACL to record strain during tibial displacement from a neutral reference fixed femur. Testing was performed at 0 °, 30°, 60°, and 90° of knee flexion, ten cycles of anterior-posterior loads were applied to the limit of 150 N.
Posteromedial meniscocapsular injuries were made arthroscopically with posterior medial portal by cutting the capsule attachment with a blade. Repair was performed as previously described 7 utilizing #2 fiberwire and spectrum curved suture passer, standard 3 suture repair per lesion. Knees were tested in three different states: native state, with defect, and repair condition.

Results

Tibial displacement and Strain in the ACL increased after posteromedial meniscocapsular lesion creation. The effect was most prominent at 30 degrees of flexion and was statistically significant (Figure 1). More importantly, the translation and strain returned to near baseline in all samples, and in some case actually decreased compared to the native state after meniscocapsular repair.
Conclusion:Disruption of the posteromedial meniscocapsular junction significantly increases the strain in an intact ACL and increases anterior tibia translation with a constant applied 150N force. This change is correctable back to native values or better following repair of the junction tear.
Clinical Relevance: Posteromedial meniscocapsular injuries represent an important and often missed lesion associated with acute ACL ruptures. When left untreated, these lesions predispose to increased anterior tibial translation and increased ACL strain. Repairing these lesions at the time of ACL reconstruction is important in restoring knee biomechanics and minimizing stress on the ACL graft.