In vitro comparison of transfixation and standard full-limb casts for prevention of displacement of a mid-diaphyseal third metacarpal osteotomy site in horses.
OBJECTIVE
To compare transfixation and standard full-limb casts for prevention of in vitro displacement of a mid-diaphyseal third metacarpal osteotomy site in horses.


METHODS
6 forelimbs from 6 horses euthanatized for reasons not related to the musculoskeletal system.


METHODS
A 30 degrees osteotomy was performed in the mid-diaphysis of the third metacarpal bone. Two 4.5-mm cortical bone screws were placed across the osteotomy site to maintain alignment during casting. Two 6.35-mm Steinmann pins were placed from a lateral-to-medial direction in the distal aspect of the radius. A full-limb cast that incorporated the pins was applied. An extensometer was positioned in the osteotomy site through a window placed in the dorsal aspect of the cast, and after removal of the screws, displacement was recorded while the limb was axially loaded to 5,340 N (1,200 lb). Pins were removed, and the standard full-limb cast was tested in a similar fashion.


RESULTS
The transfixation cast significantly reduced displacement across the osteotomy site at 445 N (100 lb), 1,112 N (250 lb), 2,224 N (500 lb), and 4,448 N (1,000 lb), compared with the standard cast.


CONCLUSIONS
A full-limb transfixation cast provides significantly greater resistance than a standard full-limb cast against axial collapse of a mid-diaphyseal third metacarpal osteotomy site when the bone is placed under axial compression. Placement of full-limb transfixation casts should be considered for the management of unstable fractures of the third metacarpal bone in horses.
Hopper
S A
SA
Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Washington State University, Pullman 99164-7060, USA.
Schneider
R K
RK
Johnson
C H
CH
Ratzlaff
M H
MH
White
K K
KK
D000818:Animals; D002102:Cadaver; D002370:Casts, Surgical / Q000662:veterinary*; D018483:Diaphyses; D005552:Forelimb; D005594:Fracture Fixation, Intramedullary / Q000662:veterinary; D006736:Horses; D008663:Metacarpus; D009984:Orthopedic Fixation Devices / Q000662:veterinary*; D010027:Osteotomy / Q000379:methods / Q000662:veterinary*