Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Engineering Science

Program

Biomedical Engineering

Supervisor

Willing, Ryan

2nd Supervisor

Getgood, Alan

Co-Supervisor

Abstract

The posterolateral corner (PLC) is a complex of ligaments and soft tissues in the knee that primarily constrain external tibial rotation. Neglecting PLC injury is a contributing factor in graft failure following cruciate ligament reconstruction. This emphasizes the importance of understanding PLC injury mechanisms, considering their disposition to multi-ligament tears. The PLC can be damaged by hyperextension. Tibial torsion, a twisting of the tibia longitudinally relative to the femur, offsets the transverse knee alignment, consequently altering the loading of soft tissues. Therefore, the objective of this investigation was to determine if tibial torsion affects loading of PLC components during hyperextension, as an indication of an underlying injury pattern. A joint motion simulator was used to record flexion torque magnitudes following the sectioning of individual PLC components in cadaveric specimens. Tibial torsion affected the load distribution of PLC components.

Summary for Lay Audience

The posterolateral corner (PLC) complex is a collection of soft tissues and ligaments located at the back, outside corner of the knee joint. The primary components are the lateral collateral ligament (LCL), the popliteofibular ligament (PFL), and the popliteus tendon, which together constrain external tibial rotation. Isolated injury to this complex is rare. It is frequently damaged alongside anterior and posterior cruciate ligaments. Clinicians may prioritize treatment of these major ligaments, neglecting the injury to the PLC. Consequently, untreated PLC injuries lead to cruciate ligament graft failure [4].

The most common mechanism of PLC injury is a combination of forces involving varus stress and hyperextension of the knee joint, occurring in situations like motor vehicle accidents or athletics. Researchers from the Kliniek ViaSana (Mill, Netherlands) recognized that several patients with PLC injuries also exhibited underlying abnormal tibial torsion, a twisting of the tibia along its longitudinal axis, prompting consideration that tibial transverse malalignment may be a contributing factor to PLC injury. It is hypothesized that excessive external tibial torsion alters the loading pattern within the knee joint, thereby increasing the stress on specific ligaments. These increased loads may heighten PLC susceptibility to injury when subjected to hyperextension forces.

There is limited research exploring loading of the posterolateral corner complex during hyperextension stress in the presence of a torsional deformity. We aimed to pioneer this area of study by establishing the loading pattern of PLC components during hyperextension in patients with abnormal tibial alignment. We used a joint motion simulator to evaluate force contributions of PLC components. We measured joint reaction forces before and after cutting a soft tissue structure, attributing the change in forces to be representative of the loads passing through the cut tissue. Results indicate large contributions from the LCL and posterolateral capsule + PFL in restraining hyperextension. Simulated rotational deformities significantly influenced the loading pattern of PLC structures. Considering our findings, when a patient presents with a knee injury, tibial torsion, and describes a mechanism involving hyperextension, clinicians should be particularly vigilant in assessing for potential PLC damage.

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