Faculty Collaboration Database

Biomechanical evaluation of locking plate radial shaft fixation: unicortical locking fixation versus mixed bicortical and unicortical fixation in a sawbone model. J Hand Surg Am 2007 Sep;32(7):971-5

Date

09/11/2007

Pubmed ID

17826548

DOI

10.1016/j.jhsa.2007.05.019

Scopus ID

2-s2.0-34548395927 (requires institutional sign-in at Scopus site)   43 Citations

Abstract

PURPOSE: Compression plating is a commonly accepted technique for treating diaphyseal forearm fractures. The purpose of this study was to evaluate the stabilizing effects of two hybrid fixations that replace the end screws of a locked unicortical fixation with bicortical (locked or unlocked) screws and to compare these hybrid fixations to an unlocked bicortical fixation.

METHODS: Sixteen composite radius sawbones were equally divided into 4 groups. We performed a midshaft osteotomy and plate fixation on the volar surface with 1 of 4 different constructs: 3 unlocked bicortical screws on each side (unlocked bicortical), 3 locked unicortical screws on each side (locked unicortical), or with 2 unicortical locked screws near the fracture and 1 bicortical unlocked (unlocked hybrid) or locked (locked hybrid) screw distant from the fracture on each end (LCP system, Synthes USA, Paoli, PA). Specimens were tested in nondestructive 4-point bending and torsion on a servo-hydraulic material testing system. The construct stiffness was obtained from the linear portion of the load-displacement curves after 3 cycles of preconditioning. The results from all groups were compared using analysis of variance and post hoc Bonferroni tests.

RESULTS: Under torsional loads, replacing the end screws of a locked unicortical configuration with bicortical screws significantly improved the construct stiffness: 57.6% increase for the locked screws and 51.6% increase for the unlocked. In anteroposterior (AP) bending, the highest improvement over the locked unicortical configuration came from the locked hybrid constructs (42.9% increase). When compared with the unlocked bicortical configuration, both hybrid constructs provide equivalent stability in torsion but superior stability in AP bending.

CONCLUSIONS: Replacing a single set of unicortical locked screws with locked or unlocked bicortical screws distant from the fracture site improves torsional stability of the construct by more than 50%, giving stability equal to standard unlocked plating. The hybrid fixation, however, with locked bicortical end screws has the best stability in AP bending.

Author List

Roberts JW, Grindel SI, Rebholz B, Wang M

Authors

Steven I. Grindel MD Professor in the Orthopaedic Surgery department at Medical College of Wisconsin
Mei Wang PhD Associate Professor in the Orthopaedic Surgery department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Analysis of Variance
Bone Plates
Bone Screws
Diaphyses
Fracture Fixation, Internal
Humans
Materials Testing
Models, Biological
Prosthesis Design
Radius Fractures
Torsion, Mechanical