Cross-Sectional Areas and Volumes Occupied by Implants in Simulated Scaphoid Fractures.

Abstract

This study determined the volume of bone replaced by an implant at the proximal and distal poles of simulated scaphoid fractures. We also measured the cross-sectional area of the implant relative to the cross-sectional area of the scaphoid at 2 different simulated fracture locations. Microcomputed tomograhy scans of 7 cadaveric scaphoids were used to create 3-dimensional models in which transverse proximal pole and midwaist fractures were simulated. The volume occupied by 5 commonly used implants and the cross-sectional area occupied at the surface of the fractures was measured using a computer modeling software. For simulated proximal pole fractures, the implants replaced 1.5%-7.4% of the fracture cross-sectional area and 1.2%-6.4% of the proximal fragment bone volume. For midwaist fractures, the implants replaced 1.5%-6.8% of the fracture cross-sectional area and 1.8%-4.6% of the proximal pole volume. Although the different implant designs replaced different areas and volumes, all these differences were small and below 4%. This study provides data that relate to one aspect of fracture healing, specifically, the surface area occupied by 5 different implants in proximal and midwaist scaphoid fractures as well as the volume of bone replaced by the implant. As opposed to the impression provided by 2-dimensional planar imaging, when studied using a 3-dimensional model, the volume and surface area replaced by an implant represent a minimal percentage of scaphoid bone, suggesting a negligible clinical effect.