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.
OBJECTIVE
To determine effect of 3 half-limb casts on bone strains recorded from the proximal phalanx (P-1) and third metacarpal bone (MCIII) of equine cadaver limbs, using a mechanical testing machine.


METHODS
12 equine cadaver limbs and 4 live horses.


METHODS
Bone strains were recorded at middorsal P-1 and the dorsal cortical aspect of the distal third of MCIII while limbs were variably loaded with 100 to 1,000 lb of force. To determine ability of the cast to protect the distal portion of the limb from weight-bearing loads, strains were recorded with the limb in 1 of the 3 casts and with it unsupported. To determine cast-induced discomfort, weight-supporting and transfixation pin casts were evaluated on 2 live horses


RESULTS
All 3 casts significantly reduced bone strain at P-1. Significant differences were observed: mean 61% reduction for the standard half-limb cast, 84% for the transfixation pin cast, and 97% for the weight-supporting cast at weight-bearing force of 500 lb. Only the weight-supporting cast significantly reduced strains recorded from MCIII. The weight-supporting cast was not well tolerated by 2 live horses.


CONCLUSIONS
The 3 casts significantly reduced transfer of weight-bearing forces to the distal portion of the limb. The weight-supporting cast effectively reduced strain on the P-1 to near 0, but was well tolerated by live horses. The transfixation pin cast reduced strain on the P-1 by > 80% at weight-bearing loads of 500 lb, and live horses were comfortable. Standard half-limb casts significantly reduced strains on the P-1, but to a lesser degree than did other casts.
Schneider
R K
RK
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman 99164, USA.
Ratzlaff
M C
MC
White
K K
KK
Hopper
S A
SA
D000818:Animals; D001842:Bone and Bones / Q000502:physiology*; D002370:Casts, Surgical / Q000662:veterinary*; D018409:Foot Injuries / Q000662:veterinary*; D005552:Forelimb / Q000502:physiology; D005593:Fracture Fixation, Internal / Q000379:methods / Q000662:veterinary; D050723:Fractures, Bone / Q000628:therapy / Q000662:veterinary*; D006724:Hoof and Claw / Q000293:injuries / Q000502:physiology; D006736:Horses / Q000293:injuries* / Q000502:physiology; D066298:In Vitro Techniques; D007794:Lameness, Animal / Q000503:physiopathology; D008663:Metacarpus / Q000293:injuries* / Q000502:physiology; D013314:Stress, Mechanical; D016474:Weight-Bearing / Q000502:physiology