Determination of minimum required halo pin force

Area of Science:

• Biomechanics
• Orthopedic Devices
• Spinal Stabilization

Background:

• Halo vests are crucial for spinal immobilization.
• Current halo systems may require overtightening of pins, leading to loosening.
• Minimizing pin loosening is essential for patient safety and treatment efficacy.

Purpose of the Study:

• To establish design guidance for a novel halo system.
• To determine the optimal initial halo pin force for secure fixation.
• To reduce the necessity of overtightening halo pins.

Main Methods:

• Biomechanical testing using cadaver head constructs.
• Utilized a custom halo fixture and a tensile testing machine.
• Evaluated initial pin forces of 120, 240, and 360 N, measuring disengagement force.

Main Results:

• Linear regression predicted disengagement forces of 80, 320, and 570 N for initial forces of 120, 240, and 360 N, respectively.
• The lower 95% prediction interval indicated a need for 230 N initial pin force.
• This force is sufficient to counteract a 186 N maximum vertical load during patient use.

Conclusions:

• An average initial pin force of 230 N is necessary to prevent halo pin disengagement.
• This finding provides critical data for designing improved halo systems.
• Optimized pin forces can enhance the safety and effectiveness of halo vest applications.