Restoration of Anterior Tibial Translation Is Achievable With an Anterior Cruciate Ligament Reconstruction and Ramp Repair With Increasing Posterior Tibial Slope While Medial Meniscus Deficiency Requires Concomitant Slope-Correcting Osteotomy

Abstract

Background:

Previous studies have demonstrated that as posterior tibial slope (PTS) increases, increased force is transmitted through anterior cruciate ligament (ACL) grafts, but limited literature assesses PTS effects on anterior tibial translation (ATT) with concomitant medial meniscus (MM) pathology.

Purpose:

To investigate the effects of varying PTS angles on ATT in the presence of MM ramp tear and MM subtotal meniscectomy in the setting of ACL-sectioned and ACL-reconstructed knees.

Study Design:

Controlled laboratory study.

Methods:

Ten male matched-paired cadaveric knees underwent a posterior tibial osteotomy. Specimens were robotically assessed for ATT changes to an 88-N anterior tibial load at 30° and 90° of flexion. Slopes of 0°, 4°, 7°, 9°, 12°, 15°, 18°, and 21° were tested: ACL-intact, ACL-sectioned, ACL-sectioned and MM ramp tear, ACL reconstruction (ACLR) and MM ramp tear, and ACLR and MM ramp repair for group 1; and ACL-intact, ACL-sectioned, ACL-sectioned and subtotal medial meniscectomy, and ACLR and subtotal medial meniscectomy for group 2.

Results:

The baseline tibial position (BTP) and PTS in ACL-intact knees demonstrated a significant positive linear relationship (P < .001) at 30° of flexion. There was no significant ATT difference between ACL-sectioned states across all tested PTS angles at 30° of flexion (P > .63). The ACL-sectioned and MM ramp tear state had significantly increased ATT compared to the ACL-intact state at all tested PTS angles at 30° of flexion (P < .001). An ACLR and residual ramp tear had significantly increased ATT compared to the ACL-intact state at PTS angles of 4°, 7°, 9°, and 18° at 30° of flexion (P < .04). The ATT of the ACLR and ramp repair was not significantly different from that of the ACL-intact state at all PTS angles at 30° of flexion (P > .34). The ACLR and subtotal medial meniscectomy state had a significantly increased ATT compared to the ACL-intact state at PTS angles of 15° and 21° at 30° (all P < .04) and 18° and 21° at 90° of flexion (all P < .04).

Conclusion:

This biomechanical cadaveric study demonstrated that as PTS increases, the BTP in intact knees shifts anterior and the absolute amount of ATT with ACL sectioning does not increase as PTS increases. Also, increases in ATT were found for an ACLR with a nonrepaired MM ramp tear, while a concomitant ramp repair restored ATT to intact. Also, an ACLR with a subtotal medial meniscectomy resulted in increases in ATT with a PTS >12°.

Clinical Relevance:

A slope-reducing tibial osteotomy may be considered in knees with >12° PTS undergoing ACLR with a subtotal medial meniscectomy to optimally protect an ACLR graft. An MM ramp repair is needed with ACLR to restore ATT.