The Effect of Knee Flexion Angle for Graft Fixation During Single-Bundle Anterior Cruciate Ligament Reconstruction

At the present time, there is no consensus about the position of the knee during tensioning anterior cruciate ligament (ACL) graft fixation at the time of reconstruction, although it can be assumed to be one of the key factors for successful ACL reconstruction (ACLR). In studies that have investigated transtibial ACLR, it was suggested that 20 degrees is the ideal KFA to optimize graft force and the relative Antero-Posterior (AP) tibiofemoral relationship, while several other authors have advocated fixation in full extension to avoid overconstraining the knee. In the setting of anatomic ACLR, it has been reported that the tensioning of the graft at 30 degrees of knee flexion was associated with loss of knee extension when the anatomic femoral tunnel was chosen. Previous studies have performed gait analysis during walking in 24 patients with ACLR with hamstring autograft where graft fixation was performed at 25 degrees of knee flexion. In these study, the trans tibial (TT) technique resulted in significantly greater anterior femoral translation than healthy controls during the swing phase and excessive tibial internal rotation (IR) was found at midstance. In knees repaired with the anteromedial portal (AMP) technique, subjects were significantly less extended (5 degrees) compared with controls in late stance phase. While the AMP technique has the potential to improve overall joint stability, patients were shown to have increased difficulty with knee extension. It has also been demonstrated that since the anteromedial (AM) and posterolateral (PL) bundles of the ACL are at their longest in knee extension, the best angle for fixation would be near full extension. The aforementioned studies support the concept that anatomic ACL has an increased likelihood of anisometry and as a result the chosen KFA for fixation becomes increasingly important.

The lack of consensus regarding the optimal KFA in ACLR is reflected in the practice patterns of surgeons. A survey of Canadian Orthopaedic Surgeons demonstrated that 40% of surgeons fix the ACL at a 30 degree KFA while 30% perform fixation in full extension. The purpose of this study is to conduct a randomized controlled trial to determine if the KFA during ACLR graft fixation has an effect on postoperative outcomes. Patients undergoing single bundle BPTB ACLR will be randomized to have the surgical repair done with a KFA of either 0 degrees, or 30 degrees (measured by sterile goniometer) during anterior cruciate ligament (ACL) fixation. Patients will be followed for 24 months post surgery, with a number of qualitative patient surveys and clinical measurements being collected at 3, 6, 12 and 24 months post op, with changes being compared to baseline survey response and clinical measurement scores.

Inclusion criteria

• Male and female patients older than 16 years old with an isolated anterior cruciate ligament injury as diagnosed by clinical examination and MRI
• No pre-existing arthritis as defined by the Kellgren-Lawrence radiographic rating system
• Patients treated with an initial period of rehabilitation to eliminate swelling, optimize quadriceps strength and restore range of motion
• Surgical management with a transtibial or anteromedial portal single-bundle ACLR with bone patella tendon bone (BPTB) autograft by a fellowship-trained sports medicine surgeon.
• Provision of Informed Consent

Exclusion criteria

• Acute ACL injuries that have not undergone an initial period of physical therapy in order to restore the aforementioned parameters
• Associated grade III injury to the MCL (medial opening >10mm at 30 degrees of knee flexion or any medial opening in extension);
• Presence of a PCL or posterolateral corner injury
• Lack of informed consent.