American Society of Biomechanics Clinical Biomechanics Award 2017: Non-anatomic graft geometry is linked with asymmetric tibiofemoral kinematics and cartilage contact following anterior cruciate ligament reconstruction


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Abstract

Background:Abnormal knee mechanics may contribute to early cartilage degeneration following anterior cruciate ligament reconstruction. Anterior cruciate ligament graft geometry has previously been linked to abnormal tibiofemoral kinematics, suggesting this parameter may be important in restoring normative cartilage loading. However, the relationship between graft geometry and cartilage contact is unknown.Methods:Static MR images were collected and segmented for eighteen subjects to obtain bone, cartilage, and anterior cruciate ligament geometries for their reconstructed and contralateral knees. The footprint locations and orientation of the anterior cruciate ligament were calculated. Volumetric, dynamic MR imaging was also performed to measure tibiofemoral kinematics, cartilage contact location, and contact sliding velocity while subjects performed loaded knee flexion-extension. Multiple linear regression was used to determine the relationship between non-anatomic graft geometry and asymmetric knee mechanics.Findings:Non-anatomic graft geometry was related to asymmetric knee mechanics, with the sagittal plane graft angle being the best predictor of asymmetry. A more vertical sagittal graft angle was associated with greater anterior tibial translation (β = 0.11Symbol, P = 0.049, R2 = 0.22), internal tibial rotation (β = 0.27Symbol, P = 0.042, R2 = 0.23), and adduction angle (β = 0.15Symbol, P = 0.013, R2 = 0.44) at peak knee flexion. A non-anatomic sagittal graft orientation was also linked to asymmetries in tibial contact location and sliding velocity on the medial (β = −4.2Symbol, P = 0.002, R2 = 0.58) and lateral tibial plateaus (β = 5.7Symbol, P = 0.006, R2 = 0.54).Interpretation:This study provides evidence that non-anatomic graft geometry is linked to asymmetric knee mechanics, suggesting that restoring native anterior cruciate ligament geometry may be important to mitigate the risk of early cartilage degeneration in these patients.Highlights:Used MRI to determine link between graft geometry and post-operative knee mechanics.Observed a posterior bias in the graft tibial tunnel location relative to native.Non-anatomic graft geometry was linked to abnormal kinematics and cartilage contact.Graft sagittal plane orientation was the best predictor of abnormal knee mechanics.Provides support for restoring native anterior cruciate ligament geometry.

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