Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2023 Jan 5;5(2):189-195.
doi: 10.1016/j.jhsg.2022.12.002. eCollection 2023 Mar.

Ideal Length and Diameter for Intramedullary Screw Fixation of Metacarpal Fractures: A Biomechanical Study

Kent T Yamaguchi Jr  1 , Scott Telfer  1 , Nicholas Iannuzzi  1 , Don Hoang  1 , Jerry I Huang  1
Affiliations

Ideal Length and Diameter for Intramedullary Screw Fixation of Metacarpal Fractures: A Biomechanical Study

Kent T Yamaguchi Jr et al. J Hand Surg Glob Online. .

Abstract

Purpose: This biomechanical study evaluated the effect of intramedullary screw diameter and length relative to 3-point bending force and torsional force when used to stabilize metacarpal shaft fractures.

Methods: Transverse osteotomies were made in the proximal metacarpal shaft in 36 middle finger metacarpal fourth-generation composite Sawbones. To compare screw diameters, antegrade intramedullary screws of 30-mm length were placed in 6 metacarpals, which included 4.7-mm Acutrak 2, Standard Acutrak 2 (4.0 mm), and Mini-Acutrak 2 (3.5 mm) screws. To compare screw lengths, metacarpals were fixated with Standard Acutrak 2 screws of 26, 30, or 34 mm in length, with screw tips bypassing the osteotomy by 6, 10, or 14 mm, respectively. A 6 degrees of freedom robot was used for torsional and 3-point bending testing.

Results: Increasing screw diameter demonstrated significant differences in both 3-point bending and torsional strengths. Maximum torsional loads were 69 Ncm (4.7-mm Acutrak 2), 45 Ncm (Standard Acutrak 2), and 27 Ncm (Mini-Acutrak 2) (P < .05). Loads to failure in the 3-point bending tests were 916 N (4.7-mm Acutrak 2), 713 N (Standard Acutrak 2), and 284 N (Mini-Acutrak 2) (P < .05). Differing screw lengths demonstrated significant differences with maximum torsional loads when comparing the 26-mm screws (22 Ncm) with 30- and 34-mm screws (45 and 55 Ncm, respectively) (P < .05). The 3-point dorsal bending strengths were significantly different between the 26-mm screws (320 N) and 30- and 34-mm screws (713 N and 702 N, respectively) (P < .05).

Conclusions: The results demonstrated significantly higher torsional strength and resistance to 3-point bending with larger intramedullary screw diameters. Further, when selecting the intramedullary screw length, the screw tip should pass at least 10 mm beyond the fracture.

Clinical relevance: This study provided biomechanical evidence to guide surgeons in selecting intramedullary screw diameter and length for treating metacarpal fractures.

Keywords: Biomechanics; Intramedullary screw; Metacarpal fracture fixation; Minimally invasive.

PubMed Disclaimer

Figures

Figure 1
Figure 1
Illustrative images of the test set up for A torsional tests and B 3-point bending tests. Note that some components have been removed to allow for clear visualization.
Figure 2
Figure 2
Metacarpal displacement versus force for 3-point bending tests for range of screw diameters.
Figure 3
Figure 3
Metacarpal rotation versus torque for torsional load tests for range of screw diameters.
Figure 4
Figure 4
Metacarpal displacement versus force for 3-point bending tests for range of screw lengths.
Figure 5
Figure 5
Metacarpal rotation versus torque for torsional load tests for range of screw lengths.
See this image and copyright information in PMC

Similar articles

See all similar articles

Cited by

References

    1. Nakashian M.N., Pointer L., Owens B.D., Wolf J.M. Incidence of metacarpal fractures in the US population. Hand (N Y) 2012;7(4):426–430. - PMC - PubMed
    1. de Jonge J.J., Kingma J., van der Lei B., Klasen H.J. Fractures of the metacarpals. A retrospective analysis of incidence and aetiology and a review of the English-language literature. Injury. 1994;25(6):365–369. - PubMed
    1. Cheah A.E., Yao J. Hand fractures: indications, the tried and true and new innovations. J Hand Surg Am. 2016;41(6):712–722. - PubMed
    1. Adams J.E., Miller T., Rizzo M. The biomechanics of fixation techniques for hand fractures. Hand Clin. 2013;29(4):493–500. - PubMed
    1. Büchler U., Fischer T. Use of a minicondylar plate for metacarpal and phalangeal periarticular injuries. Clin Orthop Relat Res. 1987;214(214):53–58. - PubMed

LinkOut - more resources