Cook, Cristi R.

Objectives: Objectives: Previous analyses have characterized the incidence of lateral meniscus oblique radial tears (LMORT) commonly seen with ACL tears, and their impact on joint and meniscus stability in the presence of ACL deficiency. Purpose: To determine the clinically relevant kinematics associated with LMORT lesions untreated versus arthroscopic repair versus partial meniscectomy in combination with anterior cruciate ligament reconstruction (ACLR). Methods: Sixteen cadaver knees underwent robotic testing for anterior drawer (AD) and pivot shift (PS) simulations at multiple knee flexion angles in intact and ACL-deficient states, followed by sequential testing of arthroscopic ACL reconstruction (ACLR), creation of a LMORT 3 lesion, LMORT 3 repair, and partial meniscectomy (PM; n=8). The same testing sequence was performed for LMORT 4 lesions (n=8). Changes (Δ) from the intact state for anterior translation, internal rotation, and valgus displacements, as well as ultrasoundographic measurements of meniscal extrusion, were measured and comparatively analyzed. Results: ACLR restored kinematics in ACL-deficient knees to intact levels for all metrics tested. For AD, ACLR + LMORT3 tear and PM resulted in significantly greater anterior translation (0.8-2.1 mm differences) compared to ACL-intact at all angles ( P < 0.05) and compared to ACLR at 60 o and 90 o ( P < 0.014). For PS, ACLR + LMORT3 tear had significantly more anterior translation (1-1.4 mm differences) at 15 o than intact knees (P=0.041), and at 0 o and 15 o for PM ( P < 0.03). ACLR + LMORT4 tear and PM resulted in significantly greater anterior translation (0.9-2.3 mm differences) for AD ( P < 0.04) and PS testing ( P < 0.05) compared to intact and ACLR knees at all angles tested. ACLR+LMORT 3 repair and ACLR+LMORT4 repair restored kinematics to ACLR and intact levels at all angles tested. ACLR + LMORT3 tear ( P < 0.008) and both LMORT4 tear and PM ( P < 0.05) resulted in increased meniscal extrusion (1.8-11 mm differences) compared to intact and ACLR statuses at all tested angles for AD and PS while repairs restored meniscus stability to ACLR and intact levels. Conclusions: Untreated LMORT 3 and 4 tears increased anterior translation, pivot shift, and meniscus extrusion even after ACLR, while partial meniscectomy further exacerbated these detrimental effects. In contrast, arthroscopic side-to-side repair of LMORT lesions effectively restored measured knee kinematics. UPLOAD- https://planion-client-files.s3.amazonaws.com/AOSSM/blobs/6bf43418-abf1-49bd-b78b-cc0c501a2da0/1/AOSSM_Abstract_Images.docx UPLOAD- https://planion-client-files.s3.amazonaws.com/AOSSM/blobs/b0f0bf53-a166-4cec-bf73-176ea452b905/1/AOSSM_Abstract_CHART.docx

Background: Lateral meniscal oblique radial tears (LMORTs) affect joint and meniscal stability in anterior cruciate ligament (ACL)–deficient knees. Purpose: To determine the clinically relevant kinematics associated with the most common posterior horn LMORT lesion types, types 3 (LMORT3) and 4 (LMORT4), untreated versus arthroscopic repair versus partial meniscectomy in combination with ACL reconstruction (ACLR). Study: Controlled laboratory study. Methods: Sixteen cadaveric knees underwent robotic testing for anterior drawer and pivot-shift simulations at multiple knee flexion angles in ACL-intact and ACL-deficient states, followed by sequential testing of arthroscopic ACLR, LMORT3 lesion, LMORT3 repair, and partial meniscectomy (n = 8). The same testing sequence was performed for LMORT4 lesions (n = 8). Results: ACLR restored kinematics in ACL-deficient knees to intact levels for all metrics tested. For anterior drawer, ACLR + LMORT3 tear and partial meniscectomy resulted in significantly greater anterior translation compared with ACL-intact at all angles ( P < .05) and compared with ACLR at 60° and 90° ( P < .014). For pivot shift, compared with ACL-intact knees, ACLR + LMORT3 tear resulted in significantly more anterior translation at 15° ( P = .041); and for ACLR + partial meniscectomy, at both 0° and 15° ( P < .03). ACLR + LMORT4 tear and partial meniscectomy resulted in significantly greater anterior translation for anterior drawer ( P < .04) and pivot-shift testing ( P < .05) compared with intact and ACLR knees at all angles tested. ACLR + LMORT3 repair and ACLR + LMORT4 repair restored kinematics to ACLR and intact levels at all angles tested. ACLR + LMORT3 tear ( P < .008) and both LMORT4 tear and partial meniscectomy ( P < .05) resulted in increased meniscal extrusion compared with intact and ACLR statuses at all tested angles for anterior drawer and pivot shift, while repairs restored meniscal stability to ACLR and intact levels. Conclusion: Untreated LMORT tears increased anterior translation, pivot shift, and meniscal extrusion after ACLR, while partial meniscectomy further exacerbated these detrimental effects in this cadaveric model. In contrast, arthroscopic side-to-side repair of LMORT lesions effectively restored measured knee kinematics. Clinical Relevance: LMORT lesions are common with ACL tears and adversely affect joint stability and meniscal extrusion. This study highlights the importance of repair of LMORT 3 and 4 lesions at the time of ACLR.

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.