, Volume 471, Issue 3, pp 1039-1044
Date: 27 Oct 2012

Locking Buttons Increase Fatigue Life of Locking Plates in a Segmental Bone Defect Model

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Topic
Tumor

Abstract

Background

Durability of plate fixation is important in delayed union. Although locking plates result in stronger constructs, it is not known if locking affects the fatigue life of a plate. Two locking screws on either side of the nonunion could decrease working length and increase strain in the plate. However, the reinforcing effect of the locking head on the plate may compensate, so that it is unclear whether locking reduces fatigue life.

Questions/purposes

We determined whether locking screws, compression screws, and locking buttons reduce or increase the fatigue life of a plate.

Methods

We tested fatigue life of four constructs using an eight-hole locking plate in a segmental defect model: (1) all locking screws (Locked; n = 5); (2) all compression screws (Unlocked; n = 5); (3) six compression screws with two locking buttons in the central holes (Button; n = 6); and (4) six compression screws with two open central holes (Open; n = 6).

Results

The Button group had the longest fatigue life (1.3 million cycles). There was no difference between the Locked and Unlocked groups. All of the constructs failed by fracture of the plates through a screw hole adjacent to the defect.

Conclusions

Locking screws did not improve fatigue life, however a locking button increased the fatigue life of a locking plate in a segmental bone defect model.

Clinical Relevance

Locking buttons in holes adjacent to a defect may improve durability, which is important when delayed union is a possibility.

Each author certifies that he or she, or a member of his or her immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/licensing arrangements, etc) that might pose a conflict of interest in connection with the submitted article.
All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request.
Clinical Orthopaedics and Related Research neither advocates nor endorses the use of any treatment, drug, or device. Readers are encouraged to always seek additional information, including FDA-approval status, of any drug or device prior to clinical use.
This work was performed in the Department of Orthopaedics, The Warren Alpert Medical School of Brown University and Rhode Island Hospital; Providence, RI, USA.
A comment to this article is available at http://dx.doi.org/10.1007/s11999-012-2743-3.