Abstract
Category:
Ankle; Basic Sciences/Biologics
Introduction/Purpose:
Osteochondral lesions of the Talus (OLTs) are among the most common injuries that occur in the ankle joint and can be detrimental to the overall function. The size of the lesion is critical in determining the surgical treatment; for smaller lesion sizes, microfracture can be considered but for larger lesions joint level restoring surgical intervention might be required. In this study, talus OLTs with different areas and locations are modeled to biomechanically evaluate the ankle joint stability. Our study aims to evaluate the stress distribution and joint stiffness effect of OLTs on all the 9-cell partition zones of the talar dome in three different ankle positions during gait.
Methods:
A simplified ankle geometry of an adult female was computationally modeled with 1 mm of cartilage at both sides of the tibiotalar contact. Lesion geometries were created on the talar dome with 4.5, 6.4-, and 9-mm lesion diameters, at each grid partition location on the talus sectioned 1 (anterior) to 9 (posterior). To enhance lesion area fidelity, tilted talar planes were utilized to consider the curvature of the talar dome. The modified models were then transferred to finite element analysis software. The maximum and average von Mises stresses, and stiffness were the biomechanical parameters investigated.
Results:
Utilizing the design parameters designated for this study, 81 different OLTs are modeled and computationally simulated. It is revealed that the stress parameters are highly misleading and do not predict ankle stability. However, stiffness is found to be a more reliable parameter that has an inverse correlation with the lesion diameter. Zones 8 (posteromedial) and 7 (Figure) on the posterior, and zone 3 on the anterolateral, were observed to be the most critical zones with lesser stiffness which meant decreased ankle joint stability in neutral, dorsiflexion, and plantarflexion, respectively. Zone 9 (posteromedial) was found to be the least critical zone in regard to stiffness.
Conclusion:
In our Finite Element study, we have found that during the walking gait, lesions in zones 8, 7, and 3 significantly impact joint stability compared to other zones of the same lesion size. This suggests that certain areas have a more pronounced effect on joint stability than others. Our findings challenge the commonly accepted threshold of 150mm² for transitioning from microfracture to other cartilage-restoring surgeries, as it may not be universally valid for all zones.
