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The Role of Proximal Locking Fixation in Volar Distal Radius Fracture Fixation
Bowen Qiu, MD1, Leland E Gossett, MD1, Wayne Reizner, MD, MBA2 and Constantinos Ketonis, MD, PhD1, (1)University of Rochester Medical Center, Rochester, NY, (2)University of Rochester, Rochester, NY

Hypothesis: Displaced, unstable distal radius fractures are frequently treated with volar locked plating. We hypothesize that locking screws in the proximal plate would increase stiffness and load to failure in a comminuted distal radius model.
Methods: A comminuted metaphyseal distal radius fracture model was created by resecting a trapezoidal wedge of bone with a 10mm height at its volar aspect. A volar locked plate (Skeletal Dynamics, Miami, FL, USA) was applied to the volar aspect of the bone model. Threaded locking screws were used in all distal screw holes. Four diaphyseal screw configurations were tested: all cortical screws, locking screw in the distal most hole, locking screw in the proximal most hole, and locking screws in the proximal and distal hole. A non-locking screw was placed in the proximal most aspect of the elliptical screw hole in all configurations. All screws were placed in bi-cortical fashion. Samples were then placed into custom jigs, rigidly fixed to a mechanical testing system with a 10kN load cell (Instron ElectroPuls 10000, Norwood, MA, USA). A compressive load of 50N was applied to the samples to settle the samples into the jigs. The samples then went through a series of cyclical loading, followed by load to failure. Failure was defined as the closure of the 10mm gap or a decrease of >40% of the current load. Tukey's multiple comparison test was used for statistical analysis between groups with a p value of 0.05.
Results: There were no statistically significant differences found in initial construct stiffness. There were no differences found in motion amplitude between groups with cyclical loading at any force magnitude. There was no significant difference found in load to failure between groups. No failure of distal fixation was observed. In the all-NLS configuration, failure consistently occurred via toggling of the proximal screws allowing for proximal plate migration, whereas LS breakage or locking mechanism failure was seen in the LS configurations.
Conclusion:

  • Our study did not demonstrate biomechanical superiority with use of proximal locking screws in a synthetic bone model.
  • Mode of failure appeared to be different between LS and NLS configurations, with implant failure more commonly seen in LS configurations.
  • Further study is warranted to evaluate if a clinical benefit exists with proximal locking screws in volar plating of distal radius fractures.


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