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

Yi-Suk Kim; Seungbum Koo; Jun Ho Kim; Jungyeun Tae; Joon Ho Wang; Jin Hwan Ahn; Ki-Mo Jang; Jongmin Jeon; Do Kyung Lee

doi:10.1177/23259671231188712

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

Orthop J Sports Med. 2023 Sep 6;11(9):23259671231188712. doi: 10.1177/23259671231188712. eCollection 2023 Sep.

Authors

Yi-Suk Kim¹, Seungbum Koo², Jun Ho Kim³, Jungyeun Tae⁴, Joon Ho Wang⁵, Jin Hwan Ahn⁶, Ki-Mo Jang⁷, Jongmin Jeon⁸, Do Kyung Lee⁸

Affiliations

¹ Department of Anatomy, Catholic Institute for Applied Anatomy, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.
² Department of Mechanical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.
³ Department of Orthopedic Surgery, Kyunghee University Hospital at Gangdong, Kyunghee University School of Medicine, Seoul, Republic of Korea.
⁴ Konyang University School of Medicine, Daejeon, Republic of Korea.
⁵ Department of Orthopedic Surgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea.
⁶ Department of Orthopaedic Surgery, Saeum Hospital, Seoul, Republic of Korea.
⁷ Department of Orthopaedic Surgery, Anam Hospital, Korea University College of Medicine, Seoul, Republic of Korea.
⁸ Department of Orthopedic Surgery, Changwon Samsung Hospital, Sungkyunkwan University School of Medicine, Changwon, Republic of Korea.

Abstract

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.

Keywords: anterolateral ligament; anterolateral rotatory instability; posterior meniscocapsular laxity; ramp lesion; tibial internal rotation anterolateral rotatory instability.