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An assessment of mechanical properties and screw push-out for two 3.5-mm pearl-type locking plate systems

Giovanni Tremolada DVM, PhD1, Ryan Taggart DVM, MS2, Daniel D. Lewis DVM3, Ross H. Palmer DVM, MS1, and Nicolaas E. Lambrechts BVSc, MMedVet1
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  • 1 1Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins, CO 80526.
  • | 2 2Adelaide Veterinary Specialist and Referral Center, 102 Magill Rd, Norwood, SA 5067, Australia.
  • | 3 3Department of Small Animal Clinical Sciences, Comparative Orthopedics Biomechanics Laboratory, College of Veterinary Medicine, University of Florida, Gainesville, FL 32610.

Abstract

OBJECTIVE

To compare mechanical properties (stiffness, yield load, failure load, and deformation at failure) of 2 pearl-type locking plate system (PLS) constructs (PLS 1 and PLS 2) in a simulated fracture gap model and to compare screw push-out forces of the 2 PLSs with and without plate contouring.

SAMPLE

40 PLS constructs.

PROCEDURES

Mechanical properties of uncontoured PLS 1 (n = 8) and PLS 2 (8) constructs were evaluated in synthetic bone-plate models under axial compression. Screw push-out forces were evaluated in 6 uncontoured and 6 contoured PLSs of each type. Variables of interest were compared between PLS groups and between contoured and uncontoured plates by statistical methods.

RESULTS

Yield and failure loads were higher in the PLS 1 group than in the PLS 2 group, but stiffness did not differ significantly between groups. All constructs failed by plate bending, with greater deformation in the PLS 2 group. Push-out force to screw-plate uncoupling was higher in the PLS 2 group than in the PLS 1 group for uncontoured and contoured plates. Locking mechanism failure of PLS 1 specimens was through screw-thread stripping. The PLS 2 specimens failed by node deformation followed by screwhead stripping.

CONCLUSIONS AND CLINICAL RELEVANCE

Distinct mechanical differences were identified between the 2 PLSs. The clinical relevance of these differences is unknown. Further research including cyclic fatigue testing is needed to reveal more clinically pertinent information.

Contributor Notes

Address correspondence to Dr. Lambrechts (nic.lambrechts@colostate.edu).