Greater Knee Rotatory Instability After Posterior Meniscocapsular Injury Versus Anterolateral Ligament Injury: A Proposed Mechanism of High-Grade Pivot Shift.

Background: For anterolateral rotatory instability as a result of secondary soft tissue injuries in anterior cruciate ligament (ACL)-deficient knees, there is increasing interest in secondary stabilizers to prevent internal rotation (IR) of the tibia. Purpose: To determine which secondary stabilizer is more important in anterolateral rotatory instability in ACL-deficient knees. Study Design: Controlled laboratory study. Methods: The lower extremities of 10 fresh-frozen cadavers (20 extremities) without anterior-posterior or rotational instability were included. Matched-pair randomization was performed, with each side per specimen assigned to 1 of 2 groups. In group 1, the ACL was sectioned, followed by the anterolateral ligament (ALL); in group 2, the ACL was sectioned, followed by sequential sectioning of the posterolateral meniscocapsular complex (PLMCC) and posteromedial meniscocapsular complex (PMMCC). The primary outcome was the change in relative tibial IR during a simulated pivot-shift test with 5 N·m of IR torque and 8.9 N of valgus force. The secondary outcomes were the International Knee Documentation Committee grade in the pivot-shift test and the incidence of the grade 3 pivot shift. Results: In group 1, compared with baseline, the change in relative tibial IR at 0° of knee flexion was 1.4° (95% CI, -0.1° to 2.9°; P = .052) after ALL release. In group 2, it was 2.5° (95% CI, 0.4° to 4.8°; P = .007) after PLMCC release and 4.1° (95% CI, 0.5° to 7.8°; P = .017) after combined PLMCC and PMMCC release. Combined PLMCC and PMMCC release resulted in greater change of tibial IR with statistical significance at 0°, 15°, and 30° of knee flexion (P = .008, .057, and .004, respectively) compared with ALL release. The incidence of grade 3 pivot shifts was 10% in group 1 and 90% in group 2. Conclusion: Posterior meniscocapsular laxity caused an increase in relative tibial IR as much as ALL injury in ACL-deficient knees in our simulated laboratory test, and greater anterolateral rotatory instability occurred with posterior meniscocapsular injury compared with ALL injury. Clinical Relevance: Repair of the injured posterior meniscocapsular complex may be an important treatment option for reducing anterolateral rotatory instability in the ACL-deficient knee.

How to Perform Concomitant Medial Meniscus Pull-Out Repair With Medial Open-Wedge High Tibial Osteotomy Without Technical Failure.

Varus alignment of the knee joint (varus >5°) is known as a poor prognostic factor for medial meniscus root repair, and alignment correction is recommended in patients with varus deformity and medial meniscus root tears. However, simultaneous medial meniscus pull-out repair and high tibial osteotomy are technically demanding procedures due to the long surgical time, poor visualization, and breaking of the pull-out sutures during high tibial osteotomy procedures. In the present Technical Note, we will introduce a surgical method to perform 2 procedures simultaneously without technical difficulty. The main surgical techniques are as follows. (1) Release the superficial medial collateral ligament before arthroscopic medial meniscus pull-out repair, which secures sufficient working space and visualization. Therefore, the operation time could also be reduced by performing the arthroscopic procedure with the anterior portal. (2) Protect the pull-out sutures with an ENDOBUTTON reamer, which prevents pull-out sutures from breaking during the high tibial osteotomy procedure.