Impact of a void in the equine medial femoral condyle on bone stresses and peak contact pressures in a finite element model.
Authors: Frazer Lance L, Santschi Elizabeth M, Fischer Kenneth J
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Medial Femoral Condyle Voids and Stifle Biomechanics Subchondral bone voids in the equine medial femoral condyle (MFC) are commonly identified on imaging yet their clinical significance remains poorly understood. Frazer and colleagues used finite element modelling of a cadaveric yearling stifle to investigate how a 2-cm³ void affects loading patterns under physiological conditions (8000 N load, 155° extension). Compared to intact bone, the void substantially altered stress distribution: compression stress increased by 25%, shear stress by 50%, and tensile stress by 200%, with corresponding 30% increases in medial meniscal tension and shear. The model also demonstrated that small degrees of internal femoral rotation (2.5–5°) compounded these effects, increasing MFC peak stresses by 8–21%. These findings help explain why some MFC voids persist or progress rather than simply filling with fibrocartilage, and provide biomechanical rationale for secondary meniscal damage frequently observed clinically. For practitioners managing horses with imaging-identified MFC voids, these results underscore the importance of monitoring for meniscal pathology and considering the mechanical consequences of altered loading patterns, particularly in young horses where subtle rotational instabilities might compound stress concentration around the defect.
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Practical Takeaways
- •Subchondral bone voids in the medial femoral condyle create disproportionately high local stress concentrations that likely explain why these lesions persist and cause secondary meniscal damage—conservative management alone may be insufficient
- •Horses with medial femoral condyle voids may benefit from work modification to minimize internal femoral rotation and loaded extension, as rotation significantly increases stress at the lesion site
- •The substantial increase in meniscal stress (30%) suggests that medial femoral condyle voids frequently lead to secondary meniscal injury; early detection and management before meniscal involvement occurs is clinically important
Key Findings
- •A 2-cm³ medial femoral condyle void increased peak compression stress by 25%, shear stress by 50%, and tensile stress by 200% compared to intact bone
- •Medial femoral condyle voids increased tension and shear stress on the medial meniscus by 30%
- •Internal femoral rotation of 2.5° to 5° increased peak medial femoral condyle stresses by 8-21% under load