Ex VivoEquine Medial Tibial Plateau Contact Pressure With an Intact Medial Femoral Condyle, With a Medial Femoral Condylar Defect, and After Placement of a Transcondylar Screw Through the Condylar Defect

Abstract

Stifle flexion increases force, contact area, and stress load on the medial tibial plateau and is most pronounced caudally. An MFC defect alters load on the medial tibial plateau, and a transcondylar screw may reverse some of those changes.

Impact of a void in the equine medial femoral condyle on bone stresses and peak contact pressures in a finite element model

“…Two previous studies have measured contact pressure ex vivo on the proximal tibia under the equine medial meniscus, but they did not agree on the shape of the pressure maps. The present results are most similar to Bonilla et al, predicting substantial abaxial pressure in the middle of the meniscus that is increased when an MFC void is present. If the increase in stress is magnified when joint flexion is allowed, as was demonstrated ex vivo, this may provide a mechanism for meniscal damage in horses with MFC SBC.…”

“…This increase in stress occurs in the meniscal body, a common location of injury (Figure ), and may be exacerbated when the loaded stifle is flexed . Two previous studies have measured contact pressure ex vivo on the proximal tibia under the equine medial meniscus, but they did not agree on the shape of the pressure maps. The present results are most similar to Bonilla et al, predicting substantial abaxial pressure in the middle of the meniscus that is increased when an MFC void is present.…”

“…Very little data regarding normal equine stifle kinematics and mechanics are currently available because of the technical difficulties of instrumenting and imaging the in vivo stifle. Published studies regarding some aspects of stifle mechanics are limited to cadaveric specimens describing tibial pressure maps, bone density, ligament strain, and articular surface contact . Cadaveric studies are useful but are limited by a lack of muscle activity, the removal of some structures to apply instrumentation, inherent technology limitations (pressure sensors and strain gauges), and the difficulty in safely applying in vivo loads.…”

Equine meniscal degeneration is associated with medial femorotibial osteoarthritis

“…Furthermore, Bonilla et al . also reported that the centre of the equine tibial plateau, that has no meniscal tissue cover, sustained increased stress loads throughout stifle flexion and could contribute to fraying of the meniscal inner border or formation of meniscal body tears.…”

“…The change in equine meniscal conformation from a C-shape to an L-shape described by Fowlie et al [22] that arises during stifle flexion may place the meniscal inner border under tension and could explain the fraying frequently observed at this location in all 3 meniscal segments in the present study. Furthermore, Bonilla et al [23] also reported that the centre of the equine tibial plateau, that has no meniscal tissue cover, sustained increased stress loads throughout stifle flexion and could contribute to fraying of the meniscal inner border or formation of meniscal body tears.…”