Abstract
Objectives:
Ruptures of the anterior cruciate ligament (ACL) are often associated with injuries to the anteromedial structures, with partial ruptures of the superficial medial collateral ligament (sMCL) being the most common type thereof. The aim of this study was to investigate whether ACL reconstruction (ACLR) alone is sufficient to restore native joint kinematics in cases of combined ACL rupture and partial sMCL rupture, or whether additional anteromedial reconstruction (AMR) is necessary.
Methods:
12 cadaveric knee specimens were tested in a six degrees of freedom robotic test setup (Kuka KR 60-3, operated by simVitro). The following movements were performed under 200 N axial compression at 0°, 30°, 60°, and 90° of flexion: anterior tibial translation (ATT) force with 89 N; valgus (VL) torque with 8 Nm; external rotation (ER) torque with 5 Nm; Slocum test (combined ATT and ER (ATTER)).
The following test conditions were conducted sequentially:
native
ACL deficiency (ACL cut)
ACLR: tensioning using a load cell
ACL cut + anteromedial (deep medial collateral ligament/anteromedial retinaculum) insufficiency (AM cut)
ACLR, AM cut
ACLR, AM cut, AMR: AMR with pedicled semitendinosus tendon graft
ACL cut, AM cut, partial sMCL insufficiency (psMCL cut): Pie-crusting of the sMCL up to a 20 % loss of tension
ACLR, AM cut, psMCL cut
ACLR, AM cut, psMCL cut, AMR
ACL cut, AM cut, total sMCL deficiency (sMCL cut)
ACLR, AM cut, sMCL cut, AMR
Statistical analysis was performed using mixed linear models.
Results:
For ATT, only the conditions with ACL insufficiency showed significant differences from the native state (p < 0.01 in each case) which could be restored by isolated ACLR.
For ATTER, ACL insufficiency alone had no significant impact on translation, but translation increased significantly after ACL cut + AM cut (p < 0.01). This instability increased gradually after psMCL cut and sMCL cut (Fig. 1). In the psMCL cut and sMCL cut conditions, ACLR alone was not sufficient to restore the native state (p < 0.001 compared to the native state). Only ACLR + AMR showed full restoration of the native state.
When evaluating the forces on the ACLR (Fig. 2), ATTER displayed a significant additional load on the ACLR after AM cut, psMCL cut and sMCL cut (p < 0.05). The effect of AM cut and psMCL cut could be redressed by an AMR (no significant difference to the native state).
Conclusion:
Insufficiency of anteromedial structures leads to an increased ATT in ER which in case of a partial sMCL lesion could not be fully redressed by ACLR alone. Only the combination of ACLR and AMR led to a full restoration of the native joint kinematics. Thus, additional anteromedial stabilization should be considered in cases of ACL insufficiency with (partial) lesions of the dMCL and sMCL.