In vitro comparison of the standard short limb cast and three configurations of short limb transfixation casts in equine forelimbs.

This research studied the stability of horse forelimbs under different types of casts, finding that transfixation casts (which use pins) are significantly stronger than standard short limb casts.

Experiment Design

• The experiment was set up to test the axial stability (how well the bones keep their alignment under pressure) of equine (horse) forelimbs after undergoing an oblique proximal phalangeal osteotomy – a surgical operation where a section of the horse’s phalanx (a bone in the hoof) is diagonally cut and removed.
• The stability was tested under the influence of a standard short limb cast (a simple wraparound plaster or fiberglass cast) or one of three types of transfixation cast (cast systems that use pins to further stabilize the bone). The three types of transfixation casts tested were: parallel pins (where the pins run parallel to the bone), divergent pins (where the pins angle away from each other), or parallel pins with a metal walking bar included.

Methodology

• The forelimbs were put under a load of 4,448 Newtons (approximately 1,000 pounds), at which displacement (movement away from the normal position) at the site of the osteotomy (surgical cut in the bone) was recorded.

Results and Conclusion

• The study found that the axial stability provided by the standard short limb casts was significantly lower than that provided by any form of transfixation cast. This suggests that for horses undergoing oblique proximal phalangeal osteotomies, transfixation casts may be a superior choice in order to maintain proper bone alignment during the healing phase.
• However, the study did not find significant differences in axial stability between the three types of transfixation casts (parallel pins, divergent pins, or parallel pins with a walking bar). This means that all three types of transfixation casts deliver comparable stabilizing force to the horse’s limb, making any one of them a potential choice.