The Scaphoid Safe Zone: A Radiographic Simulation Study to Prevent Cortical Perforation Arising from Different Views

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Radiology

Background:

• Scaphoid fractures are common, and internal fixation is a standard treatment.
• Iatrogenic perforation of the scaphoid cortex during fixation can lead to complications.
• Radiographic assessment of screw placement is crucial but may not always reflect actual risk.

Purpose of the Study:

• To simulate and quantify the risk of iatrogenic scaphoid cortical bone perforation during internal fixation.
• To identify critical zones for potential perforation based on simulated surgical approaches.
• To provide guidance for surgeons on optimal screw placement to minimize perforation risk.

Main Methods:

• 3D scaphoid reconstructions from CT data were used to simulate surgical approaches.
• Safe zones (SZ) and risk zones (RZ) were defined by comparing 2D radiographic views with 3D models.
• Perforation probabilities were calculated for different screw types and quadrants.

Main Results:

• Volar approach: 25% perforation risk with screws, 36% with k-wires.
• Dorsal approach: 18% perforation risk with screws, 30% with k-wires.
• Highest perforation risk identified in the ulnar-dorsal scaphoid zone.

Conclusions:

• Screws appearing close to the scaphoid cortex on AP and lateral radiographs pose a significant perforation risk.
• Particular caution is advised for the ulnar-dorsal and radial-dorsal quadrants.
• Utilizing diagrams of safe zones is recommended for accurate internal fixator placement assessment.