An in vitro biomechanical comparison of two fixation methods for transverse osteotomies of the medial proximal forelimb sesamoid bones in horses.

The researchers carried out an in vitro comparison to ascertain the mechanical strength of two methods for repairing fractures in horse’s proximal sesamoid bones. They found that transfixation wiring proved to be stronger than screws placed in lag fashion during single cycle load-to-failure testing.

Study Methods and Materials

• The team utilized a total of 17 paired equine cadaver limbs, including 13 that were repaired and 4 in normal condition. These limbs comprised the suspensory apparatus third metacarpal bone, and first as well as second phalanges.
• The medical technique used was transverse osteotomy, a surgical procedure where a bone is cut across its long axis. The researchers tested two ways to repair the resultant fractures: Transfixation Wiring (TW) and screws placed in Lag Fashion (LS).
• The limbs were mounted in a loading apparatus for single cycle-to-failure testing to ascertain mechanical properties and strength of the TW and LS repair methods. The team defined yield failure and ultimate failure based on load displacement, visual evidence of failure, or change in the moment-fetlock angle curve.

Calculations and Measurements

• Many parameters were calculated and compared to determine the effectiveness of the TW and LS methods. These factors included: force on the suspensory apparatus, force on the suspensory apparatus per kg of body weight, fetlock joint moment, angle of fetlock dorsiflexion, specimen stiffness, and ram displacement.
• These calculations were achieved using individual dimensions of the specimen and the load applied to it.

Study Findings and Conclusion

• According to the results, the load on the suspensory apparatus, load per kg of body weight, moment, applied load and angle of fetlock dorsiflexion at yield failure were significantly higher for the TW-repaired when compared to the LS-repaired specimens.
• In most TW-repaired samples, before yield failure, a gap of around 3 to 5 mm was noticed.
• Considering these results, the study concluded that, in single cycle load-to-failure mechanical tests, TW offered more strength for yield failure than LS in repairing transversely osteotomized specimens of the medial proximal forelimb sesamoid bone.