In vitro determination of equine third metacarpal bone unloading, using a full limb cast and a walking cast.
OBJECTIVE
To improve fracture treatment, in vitro experiments were performed to study the influence of a full limb cast and a walking cast on the loading regimen of bones in the distal portion of the equine forelimb.


METHODS
6 forelimbs of 6 Shetland ponies.


METHODS
Loading of the third metacarpal bone was considered a representative measure for distal limb loading. Electrical resistance rosette strain gauges were attached to the dorsal, palmar, medial, and lateral surfaces of the midshaft of this bone in 6 forelimbs of 6 Shetland ponies. The limbs were tested in a pneumatic loading device to a maximal load of 1,500 N.


RESULTS
Both casts decreased the amount of compressive forces acting on the metacarpal bone. Application of a full limb cast resulted in a variable and eccentric decrease, remaining strains ranging from 84 to 7% of the baseline value. A walking cast was superior in that it gave a centric and more uniform reduction of compressive loading to < 11% of the baseline value. Moreover, a walking cast neutralized the bending and torsion components of the loading.


CONCLUSIONS
This study confirmed the clinical experience that a walking cast creates more reliable and favorable conditions for healing of fractures than does a full limb cast.
Brommer
H
H
Department of General and Large Animal Surgery, Faculty of Veterinary Medicine, Utrecht University, The Netherlands.
Back
W
W
Schamhardt
H C
HC
Rijkenhuizen
A B
AB
Barneveld
A
A
D000818:Animals; D001696:Biomechanical Phenomena; D002370:Casts, Surgical / Q000662:veterinary*; D004867:Equipment Design; D005552:Forelimb; D050723:Fractures, Bone / Q000601:surgery / Q000662:veterinary; D006734:Horse Diseases; D006736:Horses; D008124:Locomotion; D008297:Male; D008663:Metacarpus / Q000033:anatomy & histology / Q000502:physiology*; D013314:Stress, Mechanical