Biomechanical comparison of two locking plate constructs under cyclic torsional loading in a fracture gap model

A. Bilmont; S. Palierne; M. Verset; P. Swider; A. Autefage

doi:10.3415/VCOT-14-12-0181

Veterinary and Comparative Orthopaedics and Traumatology, Inhaltsverzeichnis

Vet Comp Orthop Traumatol 2015; 28(05): 323-330
DOI: 10.3415/VCOT-14-12-0181

Original Research

Schattauer GmbH

Biomechanical comparison of two locking plate constructs under cyclic torsional loading in a fracture gap model

Two screws versus three screws per fragment

A. Bilmont

¹Université de Toulouse, INP, Ecole Nationale Vétérinaire de Toulouse, Unité de Recherche Clinique, Laboratoire de Biomécanique, Toulouse, France

,

S. Palierne

¹Université de Toulouse, INP, Ecole Nationale Vétérinaire de Toulouse, Unité de Recherche Clinique, Laboratoire de Biomécanique, Toulouse, France

,

M. Verset

¹Université de Toulouse, INP, Ecole Nationale Vétérinaire de Toulouse, Unité de Recherche Clinique, Laboratoire de Biomécanique, Toulouse, France

,

P. Swider

²Université de Toulouse, Institut de Mécanique des Fluides de Toulouse (IMFT) UMR CNRS 5502, Toulouse, France

,

A. Autefage

¹Université de Toulouse, INP, Ecole Nationale Vétérinaire de Toulouse, Unité de Recherche Clinique, Laboratoire de Biomécanique, Toulouse, France

› Institutsangaben

Abstract

Summary

Objectives: The number of locking screws required per fragment during bridging osteo-synthesis in the dog has not been determined. The purpose of this study was to assess the survival of two constructs, with either two or three screws per fragment, under cyclic torsion.

Methods: Ten-hole 3.5 mm stainless steel locking compression plates (LCP) were fixed 1 mm away from bone surrogates with a fracture gap of 47 mm using two bicortical locking screws (10 constructs) or three bicortical locking screws (10 constructs) per fragment, placed at the extremities of each LCP. Constructs were tested in cyclic torsion (range: 0 to +0.218 rad) until failure.

Results: The 3-screws constructs (29.65 ± 1.89 N.m/rad) were stiffer than the 2-screws constructs (23.73 ± 0.87 N.m/rad), and therefore, were subjected to a greater torque during cycling (6.05 ± 1.33 N.m and 4.88 ± 1.14 N.m respectively). The 3-screws constructs sustained a significantly greater number of cycles (20,700 ± 5,735 cycles) than the 2-screws constructs (15,600 ± 5,272 cycles). In most constructs, failure was due to screw damage at the junction of the shaft and head. The remaining constructs failed because of screw head unlocking, sometimes due to incomplete seating of the screw head prior to testing.

Clinical significance: Omitting the third innermost locking screw during bridging osteosynthesis led to a reduction in fatigue life of 25% and construct stiffness by 20%. Fracture of the screws is believed to occur sequentially, starting with the innermost screw that initially shields the other screws.

Keywords

Cyclic testing - locking plate - screw - torsion

Volltext

Referenzen

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