Spatial measurement for safe placement of screws within the scaphoid using three-dimensional analysis

Area of Science:

• Orthopedic Surgery
• Biomechanical Engineering
• Radiology

Background:

• Successful fixation of scaphoid fractures relies on precise headless screw placement.
• Accurate screw positioning is essential to avoid intraosseous collisions and ensure optimal healing.
• Current methods may lack precise intraoperative guidance for screw trajectory.

Purpose of the Study:

• To ascertain the safe angular placement of headless screws within the scaphoid bone.
• To establish a reliable guide for screw positioning during volar percutaneous fixation of scaphoid fractures.

Main Methods:

• Three-dimensional (3D) reconstruction of scaphoid bone models from computed tomography (CT) scans of 13 male subjects.
• Virtual insertion of a Herbert screw model into the 3D scaphoid models to determine collision-free angles.
• Application of measured safe angles to simple anteroposterior (AP) and lateral radiographs.

Main Results:

• The safe angle range in the anteroposterior view was 8° to 27° relative to the scaphoid's long axis.
• The safe angle range in the lateral view was 2° to 26° relative to the scaphoid's long axis.
• These angular ranges provide a quantifiable guide for screw placement.

Conclusions:

• Defined angular ranges offer a valuable reference for safe headless screw placement in scaphoid fractures.
• This method can enhance the precision of volar percutaneous screw fixation, potentially reducing complications.
• The findings support the use of 3D modeling and radiographic measurements for surgical planning.