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Arthrodesis of the Proximal Interphalangeal Joint in the Horse: A Cyclic Biomechanical Comparison of Two and Three Parallel Cortical Screws Inserted in Lag Fashion

Authors

  • JAMES L. CARMALT MA, VetMB, MVetSc, Diplomate ABVP & ACVS,

    1. Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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  • LANA DELANEY DVM,

    1. Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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  • DAVID G. WILSON DVM, Diplomate ACVS

    1. Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, Saskatoon, SK, Canada
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  • Funding was provided by the Western College of Veterinary Medicine-Equine Health Research Fund.

  • Dr. Delaney's current address is Edmonton Equine Veterinary Services (1998) Inc., 12215 William Short Road NW, Edmonton, AB, Canada T5B 2B7.

Corresponding author: Dr. James L. Carmalt, Department of Large Animal Clinical Sciences, Western College of Veterinary Medicine, University of Saskatchewan, 52 Campus Drive, Saskatoon, SK, Canada S7N5B4. E-mail: carmalt_vet@hotmail.com.

Abstract

Objective— To compare the biomechanical cyclic fatigue properties of 2 and 3 parallel transarticular 5.5 mm cortical screws used in arthrodesis of the proximal interphalangeal (PIP) joint.

Study Design— Randomized block design, for horse, fixation method (2 versus three 5.5 mm cortical screws), side (right, left) and end (front, hind) in cadaveric equine limbs.

Sample Population— Cadaveric adult equine fore- and hindlimbs (n=5 pairs each).

Methods— Two parallel 5.5 mm cortical screws were inserted in lag fashion, transarticularly through the PIP joint in 1 limb of a pair, and in the contralateral limb, three 5.5 mm cortical screws were inserted in similar fashion. Constructs were then tested in 3-point bending in a dorsal-to-palmar (plantar) direction using a materials testing machine using a cyclic load of −500 to −3500 N at a rate of 6 Hz.

Results— There was no significant difference in displacement at failure, force at failure or number of cycles between limbs. Forelimb constructs tended to fail at a greater mean displacement than hindlimb constructs but this difference was not significant (P=.06). There was no statistical difference in any tested biomechanical variable between left- and right-sided limbs.

Conclusions— There was no significant difference in the number of cycles to failure for the 2 methods tested.

Clinical Relevance— Two 5.5 mm cortical screws inserted in parallel for PIP joint arthrodesis is surgically simpler, results in comparable biomechanical performance in the current model and should perform as well as three 5.5 mm screws under cyclic fatigue conditions.

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