A Biomechanical Analysis of Oblique Metacarpal Metadiaphyseal Fracture Fixation in a Cadaver Model

Edgar Garcia-Lopez; Jeremy Wafong Siu; Jeffrey W Kwong; Robin N Kamal; Nicole Schroeder; Lauren M Shapiro

doi:10.1016/j.jhsa.2024.08.009

A Biomechanical Analysis of Oblique Metacarpal Metadiaphyseal Fracture Fixation in a Cadaver Model

J Hand Surg Am. 2024 Oct 1:S0363-5023(24)00401-5. doi: 10.1016/j.jhsa.2024.08.009. Online ahead of print.

Authors

Edgar Garcia-Lopez¹, Jeremy Wafong Siu², Jeffrey W Kwong², Robin N Kamal³, Nicole Schroeder², Lauren M Shapiro²

Affiliations

¹ Department of Orthopedic Surgery, University of California, San Francisco, CA. Electronic address: edgar.garcia-lopez@ucsf.edu.
² Department of Orthopedic Surgery, University of California, San Francisco, CA.
³ Department of Orthopedic Surgery, Stanford University, Redwood City, CA.

PMID: 39352346
DOI: 10.1016/j.jhsa.2024.08.009

Abstract

Purpose: Although metacarpal fractures are typically managed nonoperatively, when surgical management is indicated, metacarpal fractures are commonly treated with crossed Kirschner wires (K-wires), which may limit early range of motion. Intramedullary implants are increasing in use with the potential advantage of early range of motion; however, stability in oblique metacarpal neck fractures remains a theoretical concern. The purpose of this study was to determine the biomechanical stability of noncompressive intramedullary fixation for oblique metacarpal neck fractures compared with crossed K-wire fixation.

Methods: The index, long, and small metacarpals were harvested from three matched pairs of fresh-frozen cadavers. Oblique fractures at the metadiaphyseal region were created in each metacarpal. Each metacarpal was randomized to noncompressive, threaded intramedullary nail fixation or fixation with two crossed K-wires. Specimens were mounted in a Materials Testing System load frame and axially loaded until failure. Load to failure (LTF), stiffness, and load to 2 mm displacement were calculated from load-displacement curves. Differences in peak LTF, stiffness, and load to 2 mm displacement between noncompressive intramedullary fixation and crossed K-wire fixation were evaluated.

Results: The noncompressive intramedullary fixation cohort had a significantly higher LTF (1,190.9 ± 534.7 N vs 297.0 ± 156.0 N) and stiffness (551.3 ± 164.6 N/mm vs 283.0 ± 194.5 N/mm) when compared with the crossed K-wire fixation cohort. Load at 2 mm displacement was greater in the noncompressive intramedullary fixation cohort compared with crossed K-wire fixation (820.5 ± 203.9 vs 514.1 ± 259.6).

Conclusions: For oblique metadiaphyseal metacarpal fractures, noncompressive intramedullary fixation provides a biomechanically superior construct under axial loading in terms of LTF, stiffness, and load to 2 mm of displacement compared with crossed K-wire fixation.

Clinical relevance: Noncompressive intramedullary nails may be an alternative to K-wire fixation for the treatment of oblique metadiaphyseal metacarpal fractures.

Keywords: Biomechanics; fracture; intramedullary; metacarpal; surgery.