Effect of Cortical Screw Diameter on Reduction and Stabilization of Type III Distal Phalanx Fractures: An Equine Cadaveric Study.
OBJECTIVE
To compare reduction of type III distal phalangeal fractures using 4.5 and 5.5 mm cortical screws placed in lag fashion and an intact hoof capsule model.


METHODS
Cadaveric experimental study.


METHODS
Hooves from 12 adult horses (n=24).


METHODS
Sagittal fractures were created in pairs of distal phalanges after distal interphalangeal joint disarticulation and were reduced with either 4.5 or 5.5 mm cortical screws placed in lag fashion. Contralateral phalanges served as non-reduced controls. Fracture reduction following screw placement was assessed by comparing pre-reduction and post-reduction fracture gap measurements from radiographs using paired t-tests. Effects of incremental loading (0, 135, 270, 540, 800, 1070, and 1335 kg) on fracture gaps in 6 phalanges reduced with 4.5 mm screws and 5 phalanges reduced with 5.5 mm screws were measured from fluoroscopic images and assessed by 2-way ANOVA. Significance was set at P<.05.


RESULTS
Type III distal phalanx fractures were reliably created. Only 5.5 mm cortical screws, not 4.5 mm screws, significantly reduced fracture gaps and constrained fracture gap expansion 3 cm distal to the articular surface. Compressive loading closed the fracture gaps at the articular surface in both non-reduced control groups and those reduced with either 5.5 or 4.5 mm screws.


CONCLUSIONS
The 5.5 mm cortical screws were more effective than 4.5 mm screws in reducing type III distal phalanx fractures and restricting distal fracture gap expansion under load.
Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois.
Alastair T
AT
Kay
Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois.
Sushmitha
S
Durgam
Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois. matt1@illinois.edu.
Matthew
M
Stewart
Department of Veterinary Clinical Medicine, University of Illinois, Urbana, Illinois.
Stephen
S
Joslyn
Department of Pathobiology, University of Illinois, Urbana, Illinois.
David J
DJ
Schaeffer
Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois.
Gavin
G
Horn
Department of Mechanical Science and Engineering, University of Illinois, Urbana, Illinois.
Richard
R
Kesler
Veterinary Diagnostic Laboratory, University of Kentucky, Lexington, Kentucky.
Peter
P
Chew
D000818:Animals; D001863:Bone Screws / Q000706:statistics & numerical data / Q000662:veterinary*; D002102:Cadaver; D005260:Female; D005592:Fracture Fixation / Q000379:methods / Q000662:veterinary*; D050723:Fractures, Bone / Q000601:surgery / Q000662:veterinary*; D006724:Hoof and Claw / Q000601:surgery; D006736:Horses / Q000293:injuries* / Q000601:surgery*; D008297:Male; D050277:Toe Phalanges / Q000601:surgery*