In 1959, the halo traction apparatus was introduced by Perry and Nickel for perioperative stabilization of the cervical spine in patients with poliomyelitis1. Currently, its indications have been expanded to the treatment of traumatic cervical spinal injuries2-15, inflammatory diseases16-18, infections19-22, neoplasia23-26, and other occipitocervical anomalies27-30.
Despite the relatively successful results of stabilization and fusion of the cervical spine with halo-vest immobilization, high complication rates have been reported. Several retrospective studies have described complications associated with halo-vest immobilization, especially in the elderly31-40. Because of an increased rate of serious adverse events that have been reported in the recent literature, with death and pneumonia rates as high as 40% and 47%, respectively, there has been a growing tendency of restraint with regard to the use of the halo vest41-44.
Nonetheless, it has been the experience in our spine unit that patients treated with halo-vest immobilization have had a low rate of serious complications. We believe that improvements in technique as well as experience and awareness in both the prevention and the management of complications may have contributed to a lower rate of complications45-50. To our knowledge, no prospective, descriptive contemporary series of complications associated with halo-vest immobilization has been published.
The main purpose of this study was to perform a prospective investigation of the incidence of complications associated with the use of halo-vest immobilization. Our secondary objective was to examine the following literature-based hypotheses: (1) elderly patients (sixty-five years old or more) would have a higher risk of pneumonia and death41,43, (2) halo pin-loosening would be a risk factor for pin-site infection and penetration26,32,51, and (3) cervical fractures with facet joint involvement or dislocation would result frequently in the loss of alignment in patients managed with immobilization with a halo vest alone without additional surgical procedures52-54.
Materials and Methods
From January 2002 to December 2006, prospective data were collected on all patients treated with immobilization in a halo vest (Bremer Halo Systems; DePuy Spine, a Johnson and Johnson company, Jacksonville, Florida) after being referred to the spine unit of our hospital, which is both a level-I trauma center as well as a tertiary referral center for spinal disorders. Both trauma patients and those with a non-trauma-related disorder were included in this study, irrespective of diagnosis, comorbidities, prior operations, neurological status, delay in treatment, or duration of therapy. Patients in whom halo-vest immobilization was used as a supplement to anterior, posterior, or circumferential surgical fixation were also included.
The presence or absence of complications was defined as the primary outcome. Complications were categorized as major, intermediate, or minor. Major complications included death; deterioration of neurological status; acquired permanent neurological deficits, including nerve root pain and nerve palsies; and thromboembolism. Intermediate complications included pulmonary complications, such as respiratory distress, atelectasis, and pneumonia; halo-related complications, such as pin penetration through one or both tables of the skull, and halo ring-loosening; and independent loss of cervical spine alignment. Minor complications included temporary neurological conditions, such as peripheral nerve paresthesias, nerve root pain, nerve root palsy, and delirium; difficulties with swallowing; and independent halo-related complications, such as pin-loosening, pin-site infection, pressure sores, incorrect primary placement of the halo vest, and severe discomfort attributed to the halo and/or vest, or general low compliance with halo-vest use. All complications that occurred from the time of halo-vest placement to its removal were recorded. This period was regarded as the duration of follow-up.
Each patient underwent a thorough neurological examination at the time of admission. The presence, or absence, of a neurological deficit was recorded. Patients with spinal cord injury were graded according to the American Spinal Injury Association (ASIA) impairment scale55,56. Additional standard diagnostic investigations, including conventional cervical spine radiographs and computed tomography and/or magnetic resonance imaging of the cervical spine, were performed. Discoligamentous injury was identified with the use of radiographs, computed tomography (for instance, flexion teardrop fractures or facet joint subluxations), and/or magnetic resonance imaging54. Dislocations and fracture-dislocations were reduced as soon as possible, usually within twelve hours of arrival in our hospital. Placement and maintenance of the halo vest was performed according to commonly accepted standards46,48. The four pins were tightened to a maximum torque of 8 in-lb (0.90 Nm). In children and in patients with osteoporosis, fixation was augmented with the placement of six pins. For optimal halo-vest care after discharge, all patients returned to our outpatient clinics at least every other week for follow-up by specialized orthopaedic cast technicians.
Routine clinical and radiographic evaluation was performed at four, eight, and twelve weeks after the initial placement of the halo vest. The frequency of routine examination was increased in patients with an unstable cervical spine injury. Radiographs were made with the patient in the supine position if he or she was unable to stand or sit. Radiographic changes indicating malalignment of the cervical spine were defined as an increase of ≥3 mm of displacement or ≥10° of angulation on follow-up radiographs. If the cervical spine alignment was not satisfactory, adjustments in traction, translation, and angulation were made. When we were unable to align, or realign, the cervical spine appropriately in a halo vest, halo-vest immobilization was regarded as a failure and surgery was performed. Because there are currently no standardized and validated radiographic criteria for healing of cervical spine fractures, we used the following criteria: bridging osseous trabeculae or callus formation at the fracture site and the absence of abnormal motion on flexion-extension radiographs. If these criteria were not met after more than twenty-four weeks, halo-vest immobilization was regarded as a failure. Other possible reasons for failure requiring surgical treatment (for instance, progressive neurological impairment during halo-vest immobilization) were also recorded.
All complications were immediately recorded by the technicians in a standardized electronic data collection system. All medical records and imaging studies were reviewed in order to retrieve missing data. Data regarding consolidation of the initial fracture(s) or stable realignment of the cervical and upper thoracic spine were also collected from the medical records.
Frequency (indicated as a percentage) was used to describe the categorical variables and complications. The odds ratio, with a 95% confidence interval, was determined with univariate regression analysis for each examined hypothesis. Model building was performed with use of unconditional logistic regression to adjust for putative confounding variables for each hypothesis separately. In case a null hypothesis was rejected in univariate regression analysis, multivariate modeling with use of a specific, described subset of covariates, including possible confounders, was applied. In order to facilitate multivariate modeling, variables and potential confounders of interest were determined and recorded for each patient. All statistical analyses were considered significant when alpha was <0.05.
Source of Funding
There was no source of funding for this study.
During a five-year period, 239 patients were treated with halo-vest immobilization. A summary of demographic and clinical data of this study group is presented in Table I and Figure 1. The mean patient age at the time of treatment was fifty years (range, four to ninety-three years). The study group included seventy-nine patients (33%) who were more than sixty-five years old. The most common indication for halo-vest immobilization was trauma (199 patients; 83%). In total, 134 patients (56%) had no neurological impairment prior to the placement of the halo vest. Of the remaining 105 patients with a neurological injury, seventy-four patients (70%) had a complete or incomplete spinal cord injury. Prior to halo-vest placement, thirty-three patients (14%) had respiratory distress and/or needed mechanical ventilation. The mean duration (and standard deviation) of halo-vest immobilization was 60 ± 33.4 days (range, 1 to 197 days). The mean duration of immobilization in patients without supplemental surgery (68.7 ± 30.5 days) was significantly longer (p < 0.001) than in patients with supplemental surgery (46.2 ± 33.1 days). Specific details for the 199 trauma patients are summarized in Table II.
A total of twenty-six major, seventy-two intermediate, and 121 minor complications were encountered in the 239 patients. Fifteen other complications that were not associated with halo-vest treatment were also reported (Table III). Ninety-five patients (40%) did not experience any complications. Without having a major complication, one patient had six complications.
Fourteen patients (6%) died during the period of halo-vest immobilization. Only one death was directly related to the halo-vest treatment. This eighty-two-year-old man with cervical spine fractures at multiple levels had aspiration pneumonia develop during immobilization. He died twelve days after the initial placement of the halo vest. He was neurologically intact and had not undergone supplemental surgical treatment. A causal relationship between halo-vest immobilization and death remained unclear for three patients, whereas halo-vest immobilization could not be related to the death of the patients with certainty in the remaining ten patients. Five of the ten patients with complete cervical paralysis died after termination of mechanical life support. Clinical details of all fourteen patients are summarized in Table IV.
Permanent neurological impairment occurred in eight patients (3%). Deterioration of motor and sensory function occurred in four patients, including one patient who had radiographic evidence of instability of the cervical spine. One patient had intraoperative neurological deterioration during removal of a recurrent glioma. In three patients, positioning and tightening of a pin resulted in a permanent supraorbital or greater occipital nerve injury. Four thromboembolic events occurred. Three patients had a deep venous thrombosis develop, and one patient had a nonlethal pulmonary embolism.
There were seventy-two intermediate complications, forty-five of which were related to halo-vest immobilization. Respiratory function was seriously impaired in twenty-seven patients (11%). Of the twelve patients who had pneumonia develop, six had acquired pneumonia during mechanical ventilation. Halo vest-related complications included loss of alignment of the cervical or upper thoracic spine (twenty-three patients; 10%), loosening of the halo ring (seven patients; 3%), and pin penetration through the outer table of the skull (fifteen pins in thirteen patients; 5%). All twenty-three patients with radiographic evidence of loss of alignment had been treated with halo-vest immobilization only. No patient had pin penetration through the inner table of the skull. Consequently, no patient with pin penetration had leakage of cerebrospinal fluid, epidural abscess formation, or meningitis. Two patients experienced a double-sided pin penetration, resulting in a total of fifteen pin penetrations.
There were 121 minor complications. All twenty minor neurological complications (9%) were temporary. Thirteen patients (6%) had difficulties swallowing during the period of halo-vest immobilization. There were eighty-eight minor complications directly related to the halo vest. These complications ranged from incorrect initial placement of the halo vest in three patients to pin-site infections in twenty-nine patients (12%). No patient had osteomyelitis develop.
Twenty-five patients (11%) underwent surgical stabilization because halo-vest treatment was regarded as a failure. Appropriate alignment of the cervical spine was not achieved in seven patients during initial placement of the halo vest. Despite adjustments in traction and angulation, the spine could not be reduced properly in the halo vest in eight of the twenty-three patients with loss of alignment during halo-vest immobilization. The remaining reasons for failure of halo-vest immobilization were nonunion (five patients), progressive neurological impairment (three patients), and progressive respiratory difficulties and low patient compliance in the halo vest (both in one patient). Two additional trauma patients were switched to a brace after forty-eight and fifty-two days because of halo pin penetration. Although these fractures consolidated with brace therapy, these patients were regarded as having failure of halo-vest immobilization.
Univariate regression analysis was performed to examine the three postulated hypotheses.
First, during halo-vest immobilization, patients who were more than sixty-five years old did not have a significantly increased risk of pneumonia (odds ratio, 0.66; 95% confidence interval, 0.17 to 2.52; p = 0.543) or death related to the halo-vest immobilization (odds ratio, 2.05; 95% confidence interval, 0.284 to 14.84; p = 0.467).
Second, although halo pin-loosening was not significantly related to the development of a pin-site infection (odds ratio, 2.43; 95% confidence interval, 0.73 to 8.01; p = 0.135), it was significantly related to pin penetration through the outer table of the skull (odds ratio, 4.54; 95% confidence interval, 1.12 to 18.40; p = 0.021). In addition, univariate regression analysis also showed pin-site infection to be significantly related to pin penetration (odds ratio, 5.26; 95% confidence interval, 1.59 to 17.38; p = 0.003). After a model including sex, age, pin-loosening, pin-site infection, duration of halo-vest immobilization, and indication for halo-vest use was developed, only pin-site infection appeared to be significantly related to pin penetration (odds ratio, 4.34; 95% confidence interval, 1.22 to 15.51; p = 0.024).
Third, in 164 trauma patients who were intentionally treated with halo-vest immobilization alone, cervical fractures with facet joint involvement or dislocations were significantly related to radiographic loss of alignment during follow-up (odds ratio, 2.81; 95% confidence interval, 1.06 to 7.44; p = 0.031). The inclusion of sex, age, pin-loosening, and halo-loosening in a model did not alter this significant relationship.
To our knowledge, the present investigation is the first prospective cohort study of complications associated with halo-vest immobilization. In 1986, Garfin et al.31 reported on complications in 179 patients, but the number of deaths and the pneumonia rate were not reported in that study. In the same year, Glaser et al.32 reported on complications associated with halo-vest immobilization in 245 trauma patients. Only one death was reported. In contrast, Majercik et al.41 recently reported that pneumonia developed in twenty-one (47%) of forty-five elderly patients managed with immobilization in a halo vest. Eighteen elderly patients (40%) died, and fourteen of the deaths were a result of pneumonia. Horn et al.40 reported thirty-one complications in twenty-two patients who were more than seventy years old. Eight patients died, and five of those deaths were at least in part attributable to the halo-vest immobilization.
In contrast to these high rates of serious complications, only three (4%) of seventy-nine elderly patients in our study had pneumonia develop and six elderly patients (8%) died without termination of life support. As a result of these low numbers, no significant risk factors related to these outcomes could be identified in the elderly patients. Since the deaths of only two elderly patients were possibly related to halo-vest immobilization, we believe that the major cause of death should be attributed to the serious comorbidities that are often seen in this group (Table IV). Therefore, the indications for halo-vest immobilization in elderly patients should be assessed on a case-by-case basis.
A recently proposed injury classification system and treatment algorithm for subaxial cervical fractures emphasized the importance of discoligamentous injury and proposed surgical treatment in these patients57. The high failure rate of nonoperative treatment seen in these types of injury patterns in our patients supports the basic premise of this treatment algorithm.
Hayes et al.48 described a classification system for major and minor complications in a narrative review. In the present study, we defined major complications as permanent physical impairment or death. Temporary complications were classified into intermediate and minor groups. For instance, pneumonia was considered an intermediate complication. However, if it led to death, it was considered a major complication. We believe that the use of well-defined categories of complications will place a practical and valuable emphasis on them in future reviews.
Several studies have proposed technical improvements as well as prevention and management strategies to reduce the number of direct halo-related complications45-50. Despite frequent checkups and meticulous halo-vest care, we observed pin-loosening, pin-site infection, and pin penetration frequently; however, no pin penetration through the inner table of the skull was reported. Recently, Saeed et al.51 concluded that, with early diagnosis and appropriate treatment, serious morbidity and mortality can be avoided in patients with pin penetration. Our study confirms that awareness of and responsiveness to minor complications can indeed prevent subsequent morbidity.
We believe that the recording of complications in this prospective study was more meticulous than in previously published retrospective studies. Given the possible underestimation of occurrences of complications in retrospective studies, it is rather remarkable that our rates of minor complications, such as pin-loosening and pin-site infection, are lower than those reported in the large series described by Garfin et al.31 and are comparable with those in the study of elderly patients by Horn et al.40.
Although not applied extensively in multivariate analysis, the number of prospectively collected covariates was another major strength of this study. Before a prospective database was created, a literature search was conducted to define and include all relevant variables and complications described in previous studies. After all, adjusting for putative confounders is the only way to identify valid risk factors properly. Since comorbidities and associated injuries appear to be frequently associated with mortality, these variables are of particular interest.
Some limitations of this study warrant consideration. Patient follow-up, that is, the duration of halo-vest immobilization, ranged from one day to 6.5 months, with a mean duration of sixty days. In our clinic, the duration of isolated halo-vest immobilization and combined surgical and halo-vest treatment is generally three months and six weeks, respectively. Because of the short preoperative halo-vest treatment in several patients, the number of early deaths, and the failures of halo-vest immobilization, the mean duration of halo-vest immobilization was decreased substantially. No power calculation was performed prior to the onset of this study.
A broad spectrum of comorbidities, including spinal cord injury and respiratory distress, was seen prior to the placement of the halo vest in both the trauma patients and the patients with a non-trauma-related disorder. With regard to these considerable numbers of comorbidities, and given the small number of major and intermediate complications, defining a relationship between use of halo-vest immobilization and outcomes, such as pneumonia and death, needs to be done rather cautiously. The present study emphasizes the complexity and multiple etiologies of major complications occurring during halo-vest immobilization.
In conclusion, compared with previous retrospective reports, we found lower rates of mortality and pneumonia during halo-vest immobilization and no increased risk of pneumonia or death related to halo-vest immobilization among elderly patients. Nevertheless, the total number of minor complications was substantial. This study confirms that awareness of and responsiveness to minor complications can prevent the subsequent development of serious morbidities and perhaps reduce mortality. Halo-vest immobilization remains a viable treatment modality in selected patients.
NOTE: The authors thank orthopaedic cast technicians Ruud Hiensch, Iris Lindhout, Denis Verheul, Lody Muskita, Arjan Oet, Mendel van Griethuyzen, and Matthijs Marres for their support in the registration of complications; Dr. Paul Westers for his time and expertise with the statistical analyses; and Dr. Kornelis A. Poelstra and Ms. Etty Massingham-De Rooij for their assistance in the preparation of this manuscript.
Disclosure: The authors did not receive any outside funding or grants in support of their research for or preparation of this work. Neither they nor a member of their immediate families received payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, division, center, clinical practice, or other charitable or nonprofit organization with which the authors, or a member of their immediate families, are affiliated or associated.
Investigation performed at the Spine Unit of University Medical Center Utrecht, Utrecht University, Utrecht, The Netherlands
1. Perry J, Nickel VL. Total cervical-spine fusion for neck paralysis. J Bone Joint Surg Am. 1959;41:37-60.
2. Polin RS, Szabo T, Bogaev CA, Replogle RE, Jane JA. Nonoperative management of Types II and III odontoid fractures: the Philadelphia collar versus the halo vest. Neurosurgery. 1996;38:450-7.
3. Rockswold GL, Bergman TA, Ford SE. Halo immobilization and surgical fusion: relative indications and effectiveness in the treatment of 140 cervical spine injuries. J Trauma. 1990;30:893-8.
4. Vieweg U, Schultheiss R. A review of halo vest treatment of upper cervical spine injuries. Arch Orthop Trauma Surg. 2001;121:50-5.
5. Bucholz RD, Cheung KC. Halo vest versus spinal fusion for cervical injury: evidence from an outcome study. J Neurosurg. 1989;70:884-92.
6. Chan RC, Schweigel JF, Thompson GB. Halo-thoracic brace immobilization in 188 patients with acute cervical spine injuries. J Neurosurg. 1983;58:508-15.
7. Cooper PR, Maravilla KR, Sklar FH, Moody SF, Clark WK. Halo immobilization of cervical spine fractures. Indications and results. J Neurosurg. 1979;50:603-10.
8. Ersmark H, Kalen R. A consecutive series of 64 halo-vest-treated cervical spine injuries. Arch Orthop Trauma Surg. 1986;105:243-6.
9. Hossain M, McLean A, Fraser MH. Outcome of halo immobilisation of 104 cases of cervical spine injury. Scott Med J. 2004;49:90-2.
10. Kayser R, Weber U, Heyde CE. Verletzungen des kraniozervikalen ubergangs. Orthopade. 2006;35:244-69.
11. Lesoin F, Jomin M, Kabbaj K, Guieu JD, Lacheretz M. Indications for halo immobilization of the cervical spine. Acta Neurochir (Wien). 1982;65:183-91.
12. Lind B, Sihlbom H, Nordwall A. Halo-vest treatment of unstable traumatic cervical spine injuries. Spine. 1988;13:425-32.
13. Treatment of subaxial cervical spinal injuries. Neurosurgery. 2002;50(3 Suppl):S156-65.
14. Management of combination fractures of the atlas and axis in adults. Neurosurgery. 2002;50(3 Suppl):S140-7.
15. Reilly TM, Sasso RC, Hall PV. Atlantoaxial stabilization: clinical comparison of posterior cervical wiring technique with transarticular screw fixation. J Spinal Disord Tech. 2003;16:248-53.
16. Omura K, Hukuda S, Katsuura A, Saruhashi Y, Imanaka T, Imai S. Evaluation of posterior long fusion versus conservative treatment for the progressive rheumatoid cervical spine. Spine. 2002;27:1336-45.
17. Clarke MJ, Cohen-Gadol AA, Ebersold MJ, Cabanela ME. Long-term incidence of subaxial cervical spine instability following cervical arthrodesis surgery in patients with rheumatoid arthritis. Surg Neurol. 2006;66:136-40.
18. Matsuyama Y, Kawakami N, Yoshihara H, Tsuji T, Kamiya M, Yukawa Y, Ishiguro N. Long-term results of occipitothoracic fusion surgery in RA patients with destruction of the cervical spine. J Spinal Disord Tech. 2005;18 Suppl:S101-6.
19. Spies EH, Haag M, Reichelt A. Diagnose und konservative Therapie der cervicalen Spondylitis. Z Orthop Ihre Grenzgeb. 1997;135:323-7.
20. Kanaan IU, Ellis M, Safi T, Al Kawi MZ, Coates R. Craniocervical junction tuberculosis: a rare but dangerous disease. Surg Neurol. 1999;51:21-6.
21. Gupta SK, Mohindra S, Sharma BS, Gupta R, Chhabra R, Mukherjee KK, Tewari MK, Pathak A, Khandelwal N, Suresh NM, Khosla VK. Tuberculosis of the craniovertebral junction: is surgery necessary? Neurosurgery. 2006;58:1144-50.
22. Brenner A, Donkersloot P. Cervical destructive spondylodiscitis: a report on three cases. Neurosurg Rev. 1991;14:65-7.
23. Grillo Ruggieri F, Ruelle A, Cavazzani P, Andrioli GC. Halo-vest and radiotherapy. An alternative approach to cervical spine metastases. Panminerva Med. 1988;30:81-6.
24. Abitbol JJ, Botte MJ, Garfin SR, Akeson WH. The treatment of multiple myeloma of the cervical spine with a halo vest. J Spinal Disord. 1989;2:263-7.
25. Smith SR, Saunders PW, Todd NV. Spinal stabilisation in plasma cell disorders. Eur J Cancer. 1995;31:1541-4.
26. Hashimoto Y, Doita M, Hasuda K, Korosue K. Intracerebral pneumocephalus and hemiparesis as a complication of a halo vest in a patient with multiple myeloma. Case report. J Neurosurg. 2004;100(4 Suppl Spine):367-71.
27. Metz-Stavenhagen P, Krebs S, Seidel T, Kramer F, Volpel HJ. Behandlung der Skoliose und Skoliokyphose bei Neurofibromatosis Recklinghausen. Orthopade. 2000;29:524-34.
28. Hefti F. Kongenitale Fehlbildungen an der Wirbelsaule. Orthopade. 2002;31:34-43.
29. Wong AS, Massicotte EM, Fehlings MG. Surgical treatment of cervical myeloradiculopathy associated with movement disorders: indications, technique, and clinical outcome. J Spinal Disord Tech. 2005;18 Suppl:S107-14.
30. Lowry DW, Pollack IF, Clyde B, Albright AL, Adelson PD. Upper cervical spine fusion in the pediatric population. J Neurosurg. 1997;87:671-6.
31. Garfin SR, Botte MJ, Waters RL, Nickel VL. Complications in the use of the halo fixation device. J Bone Joint Surg Am. 1986;68:320-5.
32. Glaser JA, Whitehill R, Stamp WG, Jane JA. Complications associated with the halo-vest. A review of 245 cases. J Neurosurg. 1986;65:762-9.
33. Baum JA, Hanley EN Jr, Pullekines J. Comparison of halo complications in adults and children. Spine. 1989;14:251-2.
34. Caird MS, Hensinger RN, Weiss N, Farley FA. Complications and problems in halo treatment of toddlers: limited ambulation is recommended. J Pediatr Orthop. 2006;26:750-2.
35. Schulze W, Esenwein SA, Muller EJ, Russe O, Muhr G. Komplikationen beim Halo-Fixateur. Zentralbl Neurochir. 2001;62:2-9.
36. Strohm PC, Muller ChA, Köstler W, Reising K, Sudkamp NP. Halo-Fixateur—Indikationen und Komplikationen. Zentralbl Chir. 2007;132:54-9.
37. Muller EJ, Wick M, Russe O, Muhr G. Management of odontoid fractures in the elderly. Eur Spine J. 1999;8:360-5.
38. Lögters T, Hoppe S, Linhart W, Habermann C, Windolf J, Rueger JM, Briem D. Zur Problematik des Halofixateurs beim alten Patienten: Ergebnisse einer retrospektiven Untersuchung. Unfallchirurg. 2006;109:306-12.
39. Tashjian RZ, Majercik S, Biffl WL, Palumbo MA, Cioffi WG. Halo-vest immobilization increases early morbidity and mortality in elderly odontoid fractures. J Trauma. 2006;60:199-203.
40. Horn EM, Theodore N, Feiz-Erfan I, Lekovic GP, Dickman CA, Sonntag VK. Complications of halo fixation in the elderly. J Neurosurg Spine. 2006;5:46-9.
41. Majercik S, Tashjian RZ, Biffl WL, Harrington DT, Cioffi WG. Halo vest immobilization in the elderly: a death sentence? J Trauma. 2005;59:350-88.
42. Chapman J, Bransford R. Geriatric spine fractures: an emerging healthcare crisis. J Trauma. 2007;62(6 Suppl):S61-2.
43. Frangen TM, Zilkens C, Muhr G, Schinkel C. Odontoid fractures in the elderly: dorsal C1/C2 fusion is superior to halo-vest immobilization. J Trauma. 2007;63:83-9.
44. Maak TG, Grauer JN. The contemporary treatment of odontoid injuries. Spine. 2006;31(11 Suppl):S53-61.
45. Botte MJ, Byrne TP, Abrams RA, Garfin SR. Halo skeletal fixation: techniques of application and prevention of complications. J Am Acad Orthop Surg. 1996;4:44-53.
46. Botte MJ, Garfin SR, Byrne TP, Woo SL, Nickel VL. The halo skeletal fixator. Principles of application and maintenance. Clin Orthop Relat Res. 1989;239:12-8.
47. Dormans JP, Criscitiello AA, Drummond DS, Davidson RS. Complications in children managed with immobilization in a halo vest. J Bone Joint Surg Am. 1995;77:1370-3.
48. Hayes VM, Silber JS, Siddiqi FN, Kondrachov D, Lipetz JS, Lonner B. Complications of halo fixation of the cervical spine. Am J Orthop. 2005;34:271-6.
49. Kang M, Vives MJ, Vaccaro AR. The halo vest: principles of application and management of complications. J Spinal Cord Med. 2003;26:186-92.
50. Vertullo CJ, Duke PF, Askin GN. Pin-site complications of the halo thoracic brace with routine pin re-tightening. Spine. 1997;22:2514-6.
51. Saeed MU, Dacuycuy MA, Kennedy DJ. Halo pin insertion-associated brain abscess: case report and review of literature. Spine. 2007;32:E271-4.
52. Fisher CG, Dvorak MF, Leith J, Wing PC. Comparison of outcomes for unstable lower cervical flexion teardrop fractures managed with halo thoracic vest versus anterior corpectomy and plating. Spine. 2002;27:160-6.
53. Dvorak MF, Fisher CG, Aarabi B, Harris MB, Hurbert RJ, Rampersaud YR, Vaccaro A, Harrop JS, Nockels RP, Madrazo IN, Schwartz D, Kwon BK, Zhao Y, Fehlings MG. Clinical outcomes of 90 isolated unilateral facet fractures, subluxations, and dislocations treated surgically and nonoperatively. Spine. 2007;32:3007-13.
54. Halliday AL, Henderson BR, Hart BL, Benzel EC. The management of unilateral lateral mass/facet fractures of the subaxial cervical spine: the use of magnetic resonance imaging to predict instability. Spine. 1997;22:2614-21.
55. Maynard FM Jr, Bracken MB, Creasey G, Ditunno JF Jr, Donovan WH, Ducker TB, Garber SL, Marino RJ, Stover SL, Tator CH, Waters RL, Wilberger JE, Young W. International standards for neurological and functional classification of spinal cord injury. American Spinal Injury Association. Spinal Cord. 1997;35:266-74.
56. Clinical assessment after acute cervical spinal cord injury. Neurosurgery. 2002;50(3 Suppl):S21-9.
57. Vaccaro AR, Hulbert RJ, Patel AA, Fisher C, Dvorak M, Lehman RA Jr, Anderson P, Harrop J, Oner FC, Arnold P, Fehlings M, Hedlund R, Madrazo I, Rechtine G, Aarabi B, Shainline M; Spine Trauma Study Group. The subaxial cervical spine injury classification system: a novel approach to recognize the importance of morphology, neurology, and integrity of the disco-ligamentous complex. Spine. 2007;32:2365-74.