Variability in rod to bone distance needed in pelvic subcutaneous internal fixation to avoid nerve compression: A...

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical imaging

Background:

• Pelvic internal fixation is common for unstable pelvic ring injuries.
• A known complication is femoral nerve palsy due to rod compression.

Purpose of the Study:

• To evaluate sagittal inclinations of pelvic fixation rods.
• To assess the feasibility of using a single, pre-contoured rod with constant curvature.

Main Methods:

• 3D pelvic models from CT scans were used.
• Software simulated rod placement to measure sagittal inclination, rod-to-bone distance (RTB), and transverse inclinations.
• Acceptable sagittal inclination was defined as no interference in the compression risk area.

Main Results:

• Feasible sagittal inclinations ranged from 15° to 30°.
• Average RTB varied significantly (4.0±0.9mm to 25.4±11.4mm) within this range.
• Only 46% of subjects could accommodate a rod with constant curvature.

Conclusions:

• A 15mm rod-to-bone distance is not universally safe.
• Pre-contoured rods are not suitable for all patients.
• Patient-specific templating is crucial for pelvic internal fixation to minimize complications.