Jnl Wrist Surg
DOI: 10.1055/s-0039-1685514
Scientific Article
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Impact of Screw Length on Proximal Scaphoid Fracture Biomechanics

Samik Patel
1  Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania
2  Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania
,
Juan Giugale
2  Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania
3  Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania
,
Nathan Tiedeken
2  Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania
3  Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania
,
Richard E. Debski
1  Department of Bioengineering, Swanson School of Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania
2  Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania
3  Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania
,
John R. Fowler
2  Orthopaedic Robotics Laboratory, University of Pittsburgh, Pittsburgh, Pennsylvania
3  Department of Orthopaedic Surgery, University of Pittsburgh, Pittsburgh, Pennsylvania
› Author Affiliations
Further Information

Publication History

11 June 2018

04 March 2019

Publication Date:
22 April 2019 (eFirst)

Abstract

Background Proximal scaphoid fractures display high nonunion rates and increased revision cases. Waist fracture fixation involves maximizing screw length within the cortex; however, the optimal screw length for proximal scaphoid fractures remains unknown.

Purpose The main purpose of this article is to compare stiffness and ultimate load for proximal scaphoid fracture fixation of various headless compression screw lengths.

Methods Eighteen scaphoids underwent an osteotomy simulating a 7 mm oblique proximal fracture. Screws of three lengths (10, 18, and 24 mm) were randomly assigned for fixation. Each specimen underwent cyclic loading with stiffness calculated during the last loading cycle. Specimens that withstood cyclic loading were loaded to failure.

Results No significant difference in stiffness between screw lengths was found. Ultimate load was significantly impacted by the screw length. A significant difference in ultimate load between a 10 and 24 mm screw was found; however, no significant difference occurred in ultimate load between an 18 and 24 mm screw.

Conclusions No significant difference in stiffness between all groups could be due to similarities in purchase in the proximal aspect. The 10 mm screw withstanding less ultimate load compared to the 24 mm screw could be due to the 10 mm screw gaining less purchase on either side of the fracture site compared to the 24 mm screw. Lack of significant difference in ultimate load between the 18 and 24 mm screw could be occurring because the fracture site is closer to the 18 mm screw midpoint, as distal threads are engaged closer to the fracture.

Clinical Relevance Maximizing screw length may not provide superior fixation biomechanically compared with fixation utilizing a 6 mm shorter screw for proximal scaphoid fractures.