Effect of three types of half-limb casts on in vitro bone strain recorded from the third metacarpal bone and proximal phalanx in equine cadaver limbs.

This research investigated the effects of three different types of equine half-limb casts on bone strains in horse cadaver limbs, using a mechanical testing machine. Outcomes demonstrated that all three types of cast significantly reduced bone stress, with the greatest reduction achieved by the weight-supporting cast, although this was not well tolerated by live horses.

Objective and Approach

• The key aim of this study was to understand the impacts that three differing half-limb casts have on the strains experienced by the proximal phalanx (P-1) and third metacarpal bone (MCIII) within equine cadaver limbs.
• This was done by employing a mechanical testing machine to produce forces of between 100 and 1,000 lbs on 12 horse cadaver limbs.
• In addition to this, casts were also evaluated on four live horses to determine levels of discomfort caused, alongside the cast’s capability to protect the distal portion of the limb from the weight-bearing loads applied.

Results

• All three methods of casting significantly minimized the strain on the P-1.
• Mean reductions in strain varied across the different types of cast: a 61% reduction was achieved using the standard half-limb cast, 84% with the transfixation pin cast, and a significant 97% reduction was observed when using the weight-supporting cast, with the weight being 500 lb.
• However, strain reduction in the MCIII was observed only when the weight-supporting cast was used.
• The weight-supporting cast was found to be uncomfortable by the two live horses on which it was tested.

Conclusions

• The study results demonstrate that each of the three types of half-limb casts significantly reduced the weight-bearing strain placed on the distal portion of the limb.
• Despite achieving near total reduction of strain on the P-1, the weight-supporting cast was not well received by live horses.
• Conversely, the transfixation pin cast which reduced the P-1 strain by over 80% at 500 lbs load was comfortably borne by live horses.
• The standard half-limb casts also significantly reduced P-1 stresses, although noticeably less so than the other casts.