The halo vest immobilizer (HVI) is a device that restrains the cranium to the torso, for both adult and pediatric patients. This device provides the most rigid form of external immobilization for the upper cervical spine (occipitocervical and atlantoaxial junction). When compared to conventional cervical orthoses (CO), it is the best choice for immobilizing the upper cervical spine since it can restrict atlantoaxial joint flexion-extension by 75% versus only 45%, respectively. When applied, there is intercalated paradoxical motion (least controlled being lateral bending) within the sub-axial cervical spine (at/below C3), and therefore conventional cervical orthoses are more effective in immobilizing this region. Originally developed, in 1959 by Perry and Nickel, to provide cervical immobilization for occipitocervical fusion in poliomyelitis patients, this device application protocol and vest design has since evolved allowing for a multitude of uses including the definite treatment of upper cervical spine trauma (most common), preoperative reduction of spinal deformities, and postoperative adjuvant stabilization. Examples for definitive treatment are occipital condyle fractures, occipitocervical dislocation, C1 (most Common), and C2 fractures, with an anticipated average healing time of 3 to 4 months. When used as definitive treatment, the success rate has been reported to be around 85%. However, this is directly affected by proper indication, application, and management of the device. The HVI does come with risks, which has made providers reluctant to use as definitive treatment, especially in the elderly. In the pediatric population, this device can be used for cervical spine trauma (definitive or conjunction with surgical management), severe scoliosis, and arthrodesis. HVI is also safe for toddlers (less than 4 years old), however, ambulation should be restricted within this age group. Pediatric and toddler populations have reduced skull thickness. Therefore there are differences in HVI application, which include using a higher number of pins (8-12) onto the cranium, with a lower insertion torque force (1 to 5 inch-lb). The HVI has been shown to have successful outcomes for managing some cervical spine injuries. However, there are strict indications for its use in the pediatric and adult population, particularly the elderly.
Providers must understand the anatomy of the frontal cranium as it is essential for guiding anterior pin placement. The described “safe zone” is an area located 1cm superior, over the lateral two-thirds of orbit rim (eyebrow) and just below the level of the largest cranial circumference (found 0.5 to 1cm above the top of the ears). The most medial portion of the safe zone is approximately 4.5 cm from the midline in the sagittal plane, and pin placement medial to this should be avoided. Medial to this region lies the supraorbital and supratrochlear nerves (from lateral to medial), both being terminal branches of the ophthalmic division of the trigeminal nerve, which provide sensation to the frontoparietal scalp and portions of the nasal bridge. The frontal sinus is medial to the safe zone as well and should be avoided since it’s thinner and more susceptible to pin perforation. Important anatomy lateral to this “safe zone” includes the temporal bone (thinner), temporalis muscle, and the zygomaticotemporal nerve. If anterior pins are placed too lateral, perforation, irritation with mandibular motion, and numbness or paresthesias along the temporal region can occur, respectively.
Indications for definite use in adults include:
Indications for temporary use in adults:
Indications for definitive use in pediatric patients include:
Required equipment for this procedure include:
Ideally, a minimum of two person teams is required. This includes the physician and an assistant (nurse, physician assistant, or resident).
The patient (or next of kin/health care proxy if the patient is obtunded) should be educated about the procedure along with the risks/benefits that are involved. Once 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 full, may be used. General anesthesia is not required, however, if used, an anesthesiologist must be present, and preferred to be done so in an operating room.
For adults, the procedure is performed in the following steps:
For pediatric patients, certain Technique modifications include:
Complication rates are higher in children than adults, 70% vs. 35%, respectively. These include:
Providers have a multitude of treatment options ranging for nonoperative external immobilization, to operative stabilization for cervical spine injuries and deformities in both adults and children. In recent history, the halo vest immobilizer has become a less utilized form of external immobilization due to its known common complications, advancement in cervical surgical fixation/fusion, and the understanding to accept more pseudoarthrosis that occurs from elderly immobilization with CO. The HVI, however, can still provide the most rigid form of external immobilization, therefore when indicated (patients who may not tolerate surgery or younger patients), it can still serve as a successful treatment option.
Treatment success with HVI is directly proportional to following proper indications, application, and, most importantly, maintenance and management protocols of the device, which should be carried throughout the whole immobilization period (average of 12 weeks). This includes re-tightening of the pins 24 to 48 hours after original placement, with follow up every 3 to 4 weeks thereafter. Pin site care must be performed daily or every other day to help limit pin site infection. Radiographs are taken at provider follow up appointments, to confirm the reduction remains acceptable.
Additionally, further imaging such as CT scans may help with pre-procedure pin placement planning, as anatomic variation does exist in pediatric patients. This can help avoid pin placement at cranial sutures, thin cranium regions, and overall help limit the risk of complications.
Once a provider becomes familiar with the important anatomy, and technical steps for safe pin placement and proper halo application, this procedure serves as an essential tool for a cervical spine provider's practice. Despite complications that can commonly occur (often minor), successful treatment with the HVI has been reported to be as high as 85%. Therefore the HVI may serve as a reasonable option, when indicated, for certain cervical spine injuries.
Application of the halo vest immobilizer (HVI) is a team guided procedure, requiring at least 3 individuals, including a clinician, nursing staff, and/or physician assistants/residents. Before the procedure is initiated, the clinician must designate each assistant's roles, thus eliminating any confusion as to what is expected from each other.
During HVI applications, It is critical that all team members understand basic principles of sterile technique and maintaining a sterile field, as it is required from the part of this procedure (halo ring and pin placement). Before the procedure, patient information regarding age and past medical history must be obtained, as it has been reported that patients with advanced age (older than 65 years) and cardiopulmonary complications are at higher risk for complications with HVI. Additionally, all required imaging of the cervical spine that is needed for an accurate diagnosis must be performed before the HVI application. This will help eliminate any unnecessary application of the HVI for injuries where it isn't indicated. A crash cart must be at the bedside as well, in case airway access is needed at any time prior, during, or after the procedure.
An interprofessional team that provides an integrated approach in managing the maintenance of HVI application is important in first recognizing complications early, as well as preventing them from producing morbidity and mortality. In a recent prospective cohort study evaluating 239 patients who were treated with HVI following cervical spine trauma, the rates of mortality and pneumonia complications were found to be relatively low. Elderly populations (older than 65years) did not represent an increased risk of pneumonia or death, however, there were a substantial number of minor complications between all age groups. Minor complications comprised a total of 121 of the 239 patients. The most common minor complications being the loss of cervical alignment, which occurred in 164 trauma patients, and pin site infections, which occurred in 12% of the patient. However, as shown by this studies' relatively low mortality and pneumonia rate, it confirmed that responsiveness and awareness of these such minor complications can help prevent the further development of morbidities and reduce mortality, especially when a team-based approach is applied to these patients. [Level 3]
To help prevent the more common minor complications, such as pneumonia and pin site infections, incentive spirometer and Pin site care must be performed daily, respectively. This can be ordered by the provider and performed by trained nursing staff. If such complications are suspected, medical professionals such as pulmonologists and infectious disease physicians must be consulted to prevent further morbidity and progression. To prevent pin loosening, spine providers and or residents must check the torque of all pins 24 hours after the initial application, followed by every three weeks thereafter.
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