Kinematic Analysis of Lateral Meniscal Oblique Radial Tears in the Anterior Cruciate Ligament–Deficient Knee

Abstract

Background:

Lateral meniscal oblique radial tears (LMORT) occur frequently in conjunction with anterior cruciate ligament (ACL) disruption and are anatomically distinct from meniscus root tears.

Hypothesis/Purpose:

The purpose of this study was to characterize the effects of LMORT types 3 (LMORT3) and 4 (LMORT4) lesions on joint stability and meniscal extrusion in ACL-deficient knees. Our hypothesis was that both lesions would promote significant increases in anterior translation and meniscal extrusion, with the LMORT4 lesion having a greater effect.

Study Design:

Controlled laboratory study.

Methods:

Two matched pairs of cadaveric knees (n = 4) were used to optimize the testing sequence. Additional cadaveric knees with LMORT3 (n = 8) and LMORT4 (n = 8) lesions created after ACL transection underwent robotic kinematic testing for anterior drawer and pivot-shift simulations with associated ultrasound-measured meniscal extrusion at clinically relevant knee flexion angles.

Results:

Optimization testing showed no differences on the effect of LMORT4 lesions for anterior translation and lateral meniscal extrusion with ACL-intact versus ACL-deficient knees. ACL deficiency and LMORT3 and LMORT4 lesions with ACL deficiency were associated with significantly greater anterior translation compared with ACL-intact state for both anterior drawer and pivot-shift testing at all flexion angles (P < .001). ACL deficiency with either LMORT3 or LMORT4 lesion was associated with significantly greater anterior translation than was ACL deficiency only (P < .005) for anterior drawer testing at 90° of flexion. Meniscal extrusion was greater with LMORT3 and LMORT4 lesions compared with ACL deficiency only (P < .05) for anterior drawer at 60° of flexion and for pivot shift at 15° of flexion. The LMORT4 lesion demonstrated increased anterior translation for anterior drawer (P = .003) at 60° of flexion (12%) as well as for pivot shift at 15° of flexion (7%) and 30° of flexion (13%) (P < .005) compared with ACL deficiency only.

Conclusion:

In this cadaveric model, the addition of an LMORT3 or LMORT4 lesion increased anterior laxity for both the anterior drawer and the pivot shift when compared with an isolated ACL tear. Lateral meniscal extrusion was also exacerbated by these LMORT lesions.

Clinical Relevance:

LMORT lesions, distinct from meniscus root tears, occur frequently in conjunction with ACL tears. This study characterized the biomechanical consequences of LMORT3 and LMORT4 lesions on joint stability and meniscal function, highlighting the importance of diagnosing and treating LMORT lesions at the time of ACL reconstruction.