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Comparative Study
. 2017 Oct;31(10):531-537.
doi: 10.1097/BOT.0000000000000879.

Comparison of 4 Methods for Dynamization of Locking Plates: Differences in the Amount and Type of Fracture Motion

Julia Henschel  1 , Stanley Tsai, Daniel C Fitzpatrick, J Lawrence Marsh, Steven M Madey, Michael Bottlang
Affiliations
Comparative Study

Comparison of 4 Methods for Dynamization of Locking Plates: Differences in the Amount and Type of Fracture Motion

Julia Henschel et al. J Orthop Trauma. 2017 Oct.

Abstract

Background: Decreasing the stiffness of locked plating constructs can promote natural fracture healing by controlled dynamization of the fracture. This biomechanical study compared the effect of 4 different stiffness reduction methods on interfragmentary motion by measuring axial motion and shear motion at the fracture site.

Methods: Distal femur locking plates were applied to bridge a metadiaphyseal fracture in femur surrogates. A locked construct with a short-bridge span served as the nondynamized control group (LOCKED). Four different methods for stiffness reduction were evaluated: replacing diaphyseal locking screws with nonlocked screws (NONLOCKED); bridge dynamization (BRIDGE) with 2 empty screw holes proximal to the fracture; screw dynamization with far cortical locking (FCL) screws; and plate dynamization with active locking plates (ACTIVE). Construct stiffness, axial motion, and shear motion at the fracture site were measured to characterize each dynamization methods.

Results: Compared with LOCKED control constructs, NONLOCKED constructs had a similar stiffness (P = 0.08), axial motion (P = 0.07), and shear motion (P = 0.97). BRIDGE constructs reduced stiffness by 45% compared with LOCKED constructs (P < 0.001), but interfragmentary motion was dominated by shear. Compared with LOCKED constructs, FCL and ACTIVE constructs reduced stiffness by 62% (P < 0.001) and 75% (P < 0.001), respectively, and significantly increased axial motion, but not shear motion.

Conclusions: In a surrogate model of a distal femur fracture, replacing locked with nonlocked diaphyseal screws does not significantly decrease construct stiffness and does not enhance interfragmentary motion. A longer bridge span primarily increases shear motion, not axial motion. The use of FCL screws or active plating delivers axial dynamization without introducing shear motion.

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Conflict of interest statement

M. Bottlang, D. C. Fitzpatrick, and S. M. Madey hold patents related to dynamization of osteosynthesis constructs, receive royalties from Synthes and Zimmer Biomet and serve on the Zimmer speaker bureau. The remaining authors report no conflict of interest.

Figures

FIGURE 1.
FIGURE 1.
Strategies to dynamize a locked plating construct (LOCKED) for distal femur fractures. Editor's Note: A color image accompanies the online version of this article.
FIGURE 2.
FIGURE 2.
A, Distal femur plate with alternating locked and nonlocked holes; (B) 3 distinct screws used with standard femur plate; (C and D) active plate with screw holes located in elastically suspended sliding elements. Editor's Note: A color image accompanies the online version of this article.
FIGURE 3.
FIGURE 3.
Construct stiffness achieved with the 4 strategies for plate dynamization, relative to the LOCKED control construct.
FIGURE 4.
FIGURE 4.
Axial motion at the near and far cortex, achieved with the 4 strategies for plate dynamization, relative to the LOCKED control construct. Editor's Note: A color image accompanies the online version of this article.
FIGURE 5.
FIGURE 5.
Resulting transverse shear, resulting from the 4 strategies for plate dynamization, relative to the LOCKED control construct. Editor's Note: A color image accompanies the online version of this article.
See this image and copyright information in PMC

References

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