The force exerted by the halo pin. A study comparing different halo systems

Area of Science:

• Biomechanics
• Orthopedic Devices
• Neurosurgery

Background:

• Halo systems are critical orthopedic devices for stabilizing severe cervical spine injuries.
• Understanding the biomechanical forces exerted by halo pins is essential for safe and effective clinical application.
• Variability in halo pin fixation can influence patient outcomes and device performance.

Purpose of the Study:

• To biomechanically compare the forces exerted by the halo pin across seven different halo systems.
• To investigate the influence of lubrication and interface material on halo pin force.
• To provide data for optimizing halo system design and application.

Main Methods:

• Seven halo systems were tested under controlled biomechanical conditions.
• Torque values ranging from 2 to 8 in-lb were applied to the halo pins.
• Force at the skull end was measured using a load cell with dry, lubricated (saline), and cadaveric bone interfaces.

Main Results:

• Significant variation in skull-end force was observed across different halo systems for equivalent applied torque.
• The presence of saline on the threads (lubrication) led to a wide range of force outputs.
• Cadaveric bone interface also demonstrated considerable variability in force transmission.

Conclusions:

• The biomechanical performance of halo pins is highly dependent on the specific halo system used.
• Lubrication and the nature of the interface material (e.g., bone) substantially affect the force exerted by the halo pin.
• Clinical application of halo systems requires careful consideration of these variables to ensure predictable and adequate fixation.