Safe zones for Halo pin Placement

Courtesy: Harry Benjamin Laing MRCS, Ortho M8, FRCS(Tr and Orth) Tutorials

Historical Background

• The concept of halo traction can be traced back to ancient Egypt.

• Its modern application for spinal deformity correction was revived in 1971 by Pierre Stagnara.

• Halo gravity traction was reintroduced as a safe and effective method for managing severe thoracic kyphoscoliosis.

---

Principle of Halo Gravity Traction

• Halo gravity traction works by inducing gradual soft-tissue relaxation.

• The spine is progressively lengthened using the patient’s body weight as a counterforce.

• This gradual correction reduces stress on the spinal cord and surrounding soft tissues.

• It allows partial deformity correction before definitive surgery.

---

Indications

• Severe spinal deformity greater than 90 degrees in any plane.

• Rigid or neglected spinal deformities.

• Severe thoracic kyphoscoliosis associated with compromised pulmonary function.

• Patients in whom acute correction would pose a high neurological risk.

• As a staged preoperative strategy before definitive spinal fusion.

---

Preoperative Workup and Imaging

• Requires thorough preoperative evaluation and meticulous planning.

• Rigorous screening protocols are essential.

Clinical and Laboratory Evaluation

• Screening for methicillin-resistant Staphylococcus aureus colonization.

• Pulmonary function testing to assess respiratory reserve.

• Sleep studies to evaluate for nocturnal hypoventilation or sleep apnea.

Imaging

• Standing full-length spine radiographs for scoliosis assessment.

• Dedicated cervical spine radiographs.

• Computed tomography scan for detailed bony anatomy and planning.

---

Equipment Required

• Sterile halo holding pins:

  • 10 to 12 pins in children younger than 2 years.

  • 6 to 8 pins in children older than 2 years.

• Halo ring:

  • Typically made of carbon fiber, steel, or other rigid metals.

  • Size selected approximately 2 centimeters larger than the head circumference.

• Pin driver and torque-limiting wrench to ensure controlled pin insertion.

---

Pin Placement and Safe Zones

• Pin placement follows 3 defined safe zones to minimize complications.

Anterior Pins

• Positioned laterally to avoid:

  • Frontal sinus

  • Supraorbital nerve

  • Supratrochlear nerve

Lateral Pins

• Placed just above the pinna.

• Aligned with the external auditory meatus.

Posterior Pins

• Positioned directly opposite the anterior pins.

• Pins are inserted perpendicular to the skull through skin and bone to maximize fixation stability.

---

Traction Protocol

• Initial traction weight:

  • 0.45 kilograms in very young children.

  • 2.5 to 5 kilograms in children nearing skeletal maturity.

• Traction weight is increased gradually by 1 to 3 pounds per day.

• Target traction weight is typically 33% to 50% of the patient’s body weight.

• Traction is maintained using:

  • Halo gravity traction bed

  • Wheelchair frame

  • Walker frame

---

Post-Application Monitoring

• Serial neurological examinations are mandatory.

• Careful assessment of cranial nerve function is essential.

• Regular inspection and care of pin sites.

• Ongoing cervical spine monitoring to detect early complications.

---

Advantages of Halo Gravity Traction

• Gradual soft-tissue relaxation reduces deforming forces on the spine.

• Progressive spinal lengthening allows safer deformity correction.

• Can be used in the preoperative setting to improve surgical safety.

• Increases rib-to-pelvis distance and rib separation at the curve apex.

• Functional improvements may include:

  • Improved pulmonary function

  • Improved feeding tolerance

  • Expansion of the thoracic and abdominal cavities

---

Limitations and Disadvantages

• Lack of consensus regarding:

  • Exact degree of deformity requiring traction

  • Optimal amount of correction to be achieved

• Significant variation exists in:

  • Timing of initiation

  • Duration of traction

  • Integration with definitive surgery

  • Complication management protocols

---

Complications

• Most commonly reported complications include:

  • Pin site infections

  • Pin loosening

  • Patient discomfort

  • Cranial nerve palsies

• These complications can be minimized by:

  • Gradual increase in traction weight

  • Close neurological monitoring

  • Meticulous pin site care

---

Summary

• Halo gravity traction is a valuable and effective adjunct in the management of severe pediatric spinal deformities.

• It enables gradual deformity correction while reducing neurological and pulmonary risks.

• When applied with careful patient selection, meticulous technique, and vigilant monitoring, it significantly improves both surgical safety and functional outcomes.