Halo Brace

Anatomy and Physiology

Clinicians need a thorough understanding of cranial anatomy to ensure proper pin placement. The designated "safe zone" for pin insertion is situated approximately 1 cm superior to the lateral two-thirds of the orbit rim (eyebrow), just below the level of the largest cranial circumference, which is approximately 0.5 to 1 cm above the pinna of the ears. The most medial aspect of this safe zone is roughly 4.5 cm from the midline in the sagittal plane, with pin placement being intentionally avoided in more medial areas. Medial to this region lies the supraorbital and supratrochlear nerves (from lateral to medial), both serving as terminal branches of the ophthalmic division of the trigeminal nerve, responsible for providing sensation to the frontoparietal scalp and certain areas of the nasal bridge.[7] 

The frontal sinus, situated medially to the safe zone, should be avoided during pin placement due to its thinner bone thickness, which increases the risk of pin perforation. Notable anatomical structures lateral to this safe zone comprise the temporal bone (which is thinner), the temporalis muscle, and the zygomaticotemporal nerve. Placing anterior pins too laterally may lead to complications such as perforation, irritation upon mandibular movement, and numbness or paresthesias along the temporal region.[8]

Indications

Indications for Definite Use of Halo Braces in Adults

• Occipital condyle fracture with associated atlantooccipital ligamentous injury or evidence of instability.

• Bilateral occipital condyle fractures; halo vest immobilization may be considered for enhanced immobilization.

• Atlantooccipital dislocation without abnormal computed tomography (CT) criteria for instability but showing moderately abnormal magnetic resonance imaging (MRI) indicative of ligamentous injury.

• Type II Jefferson (atlas) fracture with evidence of transverse atlantal ligament disruption.

• Type II odontoid fractures in young patients (C2).

• Levine types II and IIA Hangman fractures (axis).[9][10][11][12][13][14]

Indications for Temporary Use of Halo Braces in Adults

• Indications may include adjunctive immobilization postoperatively following cervical spine surgery.

Indications for Definite Use of Halo Braces in Pediatric Patients

• Atlantooccipital dislocation, atlantoaxial subluxation, burst fracture of C1 (Jefferson fracture), atlas fractures, unstable odontoid fractures or os odontoideum, persistent atlantoaxial rotatory subluxation, idiopathic or congenital scoliosis, and preoperative reduction in patients with spinal deformity.[15][16][17]

Contraindications

The 2 types of contraindications for halo braces—absolute and relative—are provided below.

Absolute:

• Cranial fractures and/or severe bone deficiency 
• Patients requiring a craniotomy 
• Severe soft-tissue disruption and/or scalp infection over and or near proposed pin sites 

Relative:

• Polytrauma
• Pneumothorax 
• Penetrating chest injury
• Pulmonary contusion 
• Obesity
• Barrel-shaped chest 
• Advanced age (individuals aged 65 or older, with increased risk for complications and death) [18]

Equipment

Required equipment for this procedure includes: 

• Anesthetic agent: Lidocaine with epinephrine 1% solution, 10 to 20 mL
• Needle: 22- to 25-gauge
• Syringe: 10 to 20 mL 
• Gloves: Sterile and non-sterile examination gloves
• Antiseptic solution: Povidone-iodine solution or another form of antiseptic skin preparation solution 
• Crash cart: Containing a manual resuscitator and an endotracheal tube in case of airway management or any cardiopulmonary complications
• Sterile halo ring: Pre-selected size, measured from the largest head circumference
• Sterile halo pins: A total of 5, including 1 spare
• Halo pin locknuts: A total of 5, 1 serving as a spare
• Halo torque screwdriver or breakaway wrenches: If wrenches are used, 4 of them will be required.
• Ratchet wrenches
• Halo vest: Pre-selected size, measured from the circumference of the chest at the xiphoid process
• Halo upright post (4) and connecting rods (2)

Personnel

Ideally, a team of 2 to 3 clinicians is necessary to apply halo braces. The team comprises a physician and an assistant, who may be a nurse, physician assistant, or resident physician. 

Preparation

The patient (or next of kin/health care proxy if the patient is obtunded) should be educated about the procedure and the risks/benefits involved. After consent is obtained, the proper equipment and personnel should be present at the bedside. Patients should be moved into a controlled environment, procedure room, or operating room. Sedation, either partial or complete, may be used. General anesthesia is not required; however, an anesthesiologist must be present in a controlled operating room setting.

Technique or Treatment

For adults, the procedure is performed in the following steps:

1. The patient lies supine on a bed/gurney, with the head positioned 8 to 10 inches beyond the edge supported by a head positioner, typically included in a halo application kit.
2. The largest circumference of the cranium is measured in the coronal plane to determine the appropriate halo ring size. The halo ring should provide 1 to 2 cm of space between the scalp and the ring, usually positioned 0.5 to 1 cm above the pinna of the ears and the orbit. Using sterile gloves, clinicians confirm the measurement by placing the sterilized ring over the head.
3. Halo vest size is determined by measuring the circumference of the chest at the xiphoid process.
4. When holding the ring in place, the pin-site locations should be identified. The ring should be positioned one-half centimeter above the eyebrows, ensuring it is centered with equal space from the ring to the cranium circumferentially.
5. Posterior pins should be placed directly opposite the anterior pins bilaterally from the safe zone. The skin at all 4 pin sites should be prepared using a sterile technique with a povidone-iodine solution or other antiseptic solutions. 
6. Each pin site should then be anesthetized with 1% lidocaine with epinephrine, using a 22- to 25-gauge needle with a 10- or 20-mL syringe, depending on the required anesthesia.
7. Once the ring position is satisfactory, the positioning pins (already on the halo ring) are advanced by hand to hold the halo ring in place temporarily.
8. Sterile pins are then advanced through the circles in the halo ring and onto the skin at all 4 points. The patient is asked to close their eyes before the anterior pins are advanced through the skin and onto the cranium. This helps prevent patients from having permanently open eyes and being unable to close them from anterior pins, causing skin tension. 
9. Simultaneously, tighten one anterior pin and the diagonally opposite posterior pin by hand, ensuring perpendicular advancement to the cranium. Once all 4 pins are finger-tight and at 90° angles to the cranium, use the preset torque screwdriver provided with the halo application set/kit. Tighten pins with the torque screwdriver at 2 in-lb increments, proceeding diagonally in an alternating fashion onto all 4 pins. The torque screwdriver displays the in-lb measurement to accurately record increments. All 4 pins must be secured with 8 in-lb of torque.
10. Once this level of torque is achieved, the locknuts should be applied to each pin, and the temporary positioning pins can be removed.
11. The vest application begins with the posterior portion, which is divided into an anterior and a posterior section connected by straps. The assistant applies the posterior vest underneath while the clinician stabilizes the head to maintain reduction.
12. After it is applied and centered, the posterior vest is bilaterally attached to the fixed halo ring with uprights. The upright bars must be parallel for optimal stability, with the anterior crossbar aligned parallel to the posterior.
13. The anterior vest portion is then applied and connected to the posterior portion using the appropriate straps. Following this, the anterior uprights are attached to the halo ring.
14. The anterior and posterior uprights are connected with crossbars bilaterally, ensuring that all uprights are at 90° angles to the crossbars for stability.
15. The flexion and extension of the ring to the uprights are adjusted accordingly.
16. Finally, all screws, pins, and nuts are rechecked to ensure appropriate tightening.
17. All wrenches and necessary tools should be taped to the anterior vest shell to ensure accessibility in case of an emergency for vest removal or bolt/pin tightening as needed by the clinician.
18. Pin sites should be uncovered for cleaning with hydrogen peroxide or betadine solution every day or every other day. Using a cotton swab to mobilize the surrounding skin around each pin site is recommended to minimize the risk of pin site infection.
19. Each halo pin should be retorqued to 8 in-lb 24 hours after application. The halo fixator should be rechecked 2 days after the original application, followed every 3 to 4 weeks to ensure pin sites are appropriately tightened.[8][19]

For pediatric patients, certain technique modifications include:

• The torque applied to each pin is lower, with insertional torque ranging from 1- to 5 in-lb of pressure, thereby reducing the risk of pin perforation through the cranium. 
• The number of pins ranges from 8 to 12, increasing surface area and reducing the risk of pin perforation.
• The pin location is still at the safe zone anteriorly. Place posterior pines opposite from anterior pins.
• The brace/vest must be custom-fitted for children aged 2 and older. For toddlers aged 2 or younger, it is recommended to use a Minerva cast.
• CT may help pin placement by avoiding cranial sutures and thin regions of the skull. However, CT scans provide a lot of radiation exposure to pediatric patients, where the risks may outweigh the benefits.[6][17][6]

Complications

Complications of this procedure include:

• Greater occipital nerve palsy, supraorbital nerve palsy, and supratrochlear nerve palsy.

• Orbital roof fracture and orbital cellulitis.

• Abducens nerve palsy, which is more common in pediatric patients, wherein cranial nerve VI injury occurs during brace placement with applied traction. Symptoms may include diplopia, leading to the loss of lateral gaze on the affected side. Treatment typically involves releasing traction while closely observing; many cases resolve spontaneously.

• Nerve root pain.

• Pin penetration.

• Neck pain or stiffness.

• Pin and halo ring loosening, which is often believed to be caused by bone resorption at the pin site. 

• Pin site infection, which may necessitate oral antibiotic therapy if pin site drainage persists without loosening. If an abscess develops, the affected pin site must be removed, and a new site must be established along with incision and drainage. Severe cases may lead to osteomyelitis of the skull, with rare occurrences of cerebral abscesses or subdural empyema.

• Restricted arm motion due to the vest.

• Redislocation or loss of reduction at the fracture site.

• Respiratory impairment, including pneumonia or respiratory suppression, potentially leads to conditions such as pneumonia or acute respiratory distress syndrome (ARDS). This condition is more prevalent in patients aged 65 and older.

• Arrhythmia and dysphagia.

• Cranium or dural puncture.

• Pneumocranium resulting from frontal sinus pin penetration.

• Pressure ulcers developing underneath the vest or cast vest.

• Loss of immobilization at the fracture site, particularly in unstable injuries, where cervical reduction may occur due to the "snaking motion." This motion involves rotation in opposite directions, hyperextension of the upper cervical spine, and hyperflexion of the subaxial cervical spine. The motion becomes more pronounced when transitioning from the prone position, where the halo vest may loosen, to the supine position. Therefore, regular checking and re-tightening of vest straps (not halo pins) are crucial. If this complication persists, using a form-fitting cast vest may be considered. Excessive snaking motion may lead to inadequate healing and nonunion of fractures or injured sites.

• Failure to thrive, particularly in older patients.

• Incisor diastasis, which was reported in a patient with osteogenesis imperfecta.[8][17][20][21][22][23][24][25][26][27][28]

Clinical Significance

Clinicians have a multitude of treatment options available for managing cervical spine injuries and deformities in both adult and pediatric populations, ranging from nonoperative external immobilization to operative stabilization. Despite the declining use of the halo vest immobilizer due to prevalent complications and advancements in cervical surgical fixation/fusion and the pseudoarthrosis that occurs from immobilization with cervical orthoses, it remains a viable option.[29] The halo vest immobilizer continues to offer the most rigid form of external immobilization and can be a successful treatment choice in appropriate cases, such as patients who may not tolerate surgery or in younger individuals.

The success of treatment with halo vest immobilization correlates directly with adhering to proper indications, application, and, crucially, maintenance and management protocols of the device. Notably, it is essential to maintain appropriate management and upkeep throughout the immobilization period, which typically lasts around 12 weeks.[5] This involves re-tightening the pins 24 to 48 hours after initial placement, with subsequent follow-ups every 3 to 4 weeks. Daily or alternate-day pin site care is necessary to minimize the risk of infection. Additionally, radiographs are obtained at follow-up appointments to ensure adequate alignment.

Additional imaging modalities, such as CT scans, may aid in pre-procedure planning for pin placement, particularly in pediatric patients with common anatomical variations. This approach can mitigate the risk of complications by avoiding pin placement in thin cranial regions or near cranial sutures. Clinicians must have a thorough understanding of important anatomy and technical steps for safe pin placement and proper halo application before proceeding with the procedure. Despite the possibility of complications, which are typically minor, successful treatment with halo vest immobilization has been reported in up to 85% of cases. Therefore, the halo vest immobilizer may represent a reasonable option for managing cervical spine injuries in appropriate situations.[4]

Enhancing Healthcare Team Outcomes

The application and follow-up management of a halo brace requires a collaborative approach among healthcare professionals to mitigate complications, comorbidities, and overall mortality rates. The application of the halo vest immobilizer is an interprofessional procedure, ideally performed by a team of 2 to 3 clinicians comprising a physician and an assistant such as a nurse, physician assistant, or resident physician. Before the commencement of the procedure, the leading physician must assign specific roles to each assistant, clarifying expectations for each team member and minimizing confusion. Open communication and collaboration among all interprofessional team members are essential to achieve the best possible outcomes for this procedure.

When applying a halo vest, all healthcare team members must be proficient in applying sterile techniques and maintaining a sterile field, as these are essential for aspects of this procedure, such as halo ring and pin placement. Before initiating the procedure, patient information, including their age and past medical history, must be obtained, as patients with advanced age and cardiopulmonary complications are at higher risk for complications.[27] In addition, all cervical spine imaging must be completed for accurate diagnosis before applying the halo vest immobilizer. Furthermore, a crash cart must be readily available at the bedside in case airway access is required before, during, or after the procedure.

An interprofessional team adopts an integrated approach to managing the halo brace, focusing on identifying potential complications and minimizing morbidity and mortality. According to a recent prospective cohort study involving 239 patients treated with halo vest immobilization following cervical spine trauma, the rates of mortality and pneumonia complications were found to be relatively low. Older patients did not demonstrate an increased risk of pneumonia or death. However, a significant number of minor complications were observed across all age groups.

Out of the 239 patients, minor complications were reported in 121 cases. The most frequent minor complications included loss of cervical alignment observed in 164 trauma patients and pin site infections occurring in 12% of the patients. These findings suggest relatively low mortality and pneumonia rates. Recognizing minor complications is crucial for preventing additional health concerns and decreasing the risk of death. A team-based approach to managing this patient population can be especially effective in achieving these outcomes.[30]

Daily incentive spirometer exercises and pin site care are essential to prevent complications such as pneumonia and pin site infections. Clinicians can order these interventions, which can be carried out by trained nursing staff. If complications such as pneumonia or pin site infections are suspected, consultation with medical professionals, such as pulmonologists and infectious disease clinicians, is necessary to prevent further patient morbidity. To prevent pin loosening, a spine-specialized clinician should check the torque of all pins 24 hours after the initial application and then every 3 weeks thereafter.[19]