Brain abscess complicating the use of a halo orthosis

We report a case of brain abscess complicating the use of a halo orthosis in the treatment of a cervical spine injury suffered during wrestling. Four previous brain abscesses complicating the use of halo orthoses have been reported. All cases of abscess have been associated with overlying infection at the site of pin insertion. Our case and at least one of those previously reported may have been related to tightening of the halo pins after placement. Serious spine injuries occur rarely in wrestlers and are associated with the use of illegal holds and maneuvers in which one athlete is thrown to the mat. The pathophysiology and radiographic appearance of a unilateral facet dislocation are reviewed.     

Brain abscess and generalized seizure caused by halo pin intracranial penetration: case report and review of the literature

The objective of our study is to report a rare complication of halo pin insertion associated with an epileptic seizure and brain abscess, and to discuss the diagnostic and therapeutic approach to its management. The treatment of unstable cervical spine injuries with a halo vest is an established procedure. Complications of pin penetration such as brain abscess and seizure are rare, and need to be urgently treated. Intracranial abscess and seizure associated with the use of the halo device is an unusual complication, and only a few cases have been reported in the literature. A 21-year-old male had a halo vest placed for the management of an odontoid type II fracture, which he sustained from a motor vehicle accident. Ten weeks after halo ring placement he complained of headaches which relieved by analgesics. After 2 weeks he was admitted at the emergency unit in an unconscious condition after a generalized tonic-clonic seizure. The halo pins were displaced during the seizure and were removed at his admission. No drainage was noted from the pin sites, and a Philadelphia cervical collar was applied. A brain CT and MRI revealed intracranial penetration of both posterior pins and a brain abscess in the right parietal lobe. Computed tomography of the cervical spine revealed stable fusion of the odontoid fracture. Cultures from the pin sites were negative; however, intravenous wide spectrum antibiotic treatment was administered to the patient immediately for 4 weeks followed by oral antibiotics for additional 2 weeks. Anti-epileptic medication was also started at his admission. The patient was discharged from the hospital in 6 weeks without symptoms, continuing anti-epileptic medication. On the follow-up visits he had fully recovered without any neurologic sequelae. In conclusion, complications of halo pin penetration are rare which need immediate intervention. Any neurologic or infectious, local or generalized, symptom need to be investigated urgently with available imaging techniques and treated promptly. Pin over-tightening may cause bone penetration and possible deep cranial infection with serious complications.     

Subdural abscess associated with halo-pin traction

Osteomyelitis and intracranial abscess are among the most serious complications that have been reported in association with the use of the halo device. The cases of five patients who had formation of an intracranial abscess related to the use of a halo cervical immobilizer are described. All of the infections resolved after drainage of the abscess, débridement, and parenteral administration of antibiotics. Meticulous care of the pin sites is essential to avoid this serious complication. Additionally, since all of the infections were associated with prolonged halo-skeletal traction, this technique should be used with caution and with an awareness of the possible increased risks of pin-site infection and of formation of a subdural abscess.     

Pin loosening in a halo-vest orthosis: a biomechanical study

STUDY DESIGN: The cranial pin force history of a halo-vest orthosis was measured using an instrumented halo in a clinical study with three patients. Pin force values at the time of halo-vest application and at subsequent clinical visits during the halo-vest wear period were compared. OBJECTIVES: To document the pin force reduction in the cranial pins of a halo-vest orthosis in vivo. SUMMARY OF BACKGROUND DATA: The halo-vest is an orthosis commonly used to immobilize and protect the cervical spine. An important problem with halo-vest use is pin loosening. There have been no previous reports of pin force history in vivo. METHODS: A custom-built strain-gauged, open-ring halo was used to measure the compressive force and superiorly-inferiorly directed shear forces produced at the tips of the two posterior pins. The instrumented halo was applied to three patients with cervical spine fractures. Pin force measurements were recorded at the time of halo application and at subsequent follow-up visits during the entire treatment period. RESULTS: A mean compressive force of 343 +/- 64.6 N was produced at the pin tips during halo application with the patient in a supine position. On average, the compressive forces decreased by 83% (P = 0.002) during the typical halo-vest wear period. The compressive forces were substantially greater than the shear forces, which averaged only -11+/-30.2 N at the time of halo application and which did not change significantly with time. CONCLUSIONS: The study confirmed the hypothesized decrease in the compressive pin forces with time. All patients had developed at least some clinical symptoms of pin loosening at the time of halo-vest removal.     

Halo Skeletal Fixation: Techniques of Application and Prevention of Complications

The halo skeletal fixator provides the most rigid cervical immobilization of all orthoses. However, complications such as pin loosening and infection are common. Appreciation of local anatomy and adherence to established application guidelines should minimize pin-related problems. A relatively safe zone for anterior pin placement is located 1 cm above the orbital rim and superior to the lateral two thirds of the orbit. Posterior pin-site locations are less critical; positioning on the posterolateral aspect of the skull, diagonal to the contralateral anterior pins, is generally desirable. Pins should enter the skull perpendicular to the cortex, with the ring or crown sitting below the widest portion of the skull and passing about 1 cm above the helix of the ear. Pins are inserted at a torque of 8 in-lb and retightened once to 8 in-lb at 48 hours. A loose pin can be retightened to 8 in-lb if resistance is met; otherwise, a loose pin should be replaced at a nearby site. Superficially infected pins are managed with local pin care and oral antibiotics. Persistent or severe infections require pin replacement to a nearby site, parenteral antibiotic therapy, and incision and drainage as needed. In-ability to maintain acceptable cervical reduction with a halo fixator is an indication for alternative treatment, such as internal fixation or traction.     

Halo pin intracranial penetration and epidural abscess in a patient with a previous cranioplasty: case report and review of the literature.

STUDY DESIGN: Report of a patient with an epidural abscess after halo pin intracranial penetration at the site of a previous cranioplasty. OBJECTIVES: To report a rare case of intracranial penetration at the site of a previous cranioplasty associated with epidural abscess, and to discuss the diagnostic and therapeutic approach to its management. SUMMARY OF BACKGROUND DATA: The most serious complications associated with use of halo device occur when pins penetrate the inner table of the skull, resulting in cerebrospinal fluid leak and rarely in an intracranial abscess. However, no mention of intracranial halo pin penetration at the site of a previous cranioplasty was found in the literature. METHODS: A 64-year-old man with ankylosing spondylitis had a halo vest placed for management of a fracture dislocation through the C5-C6 intervertebral disc space associated with left C6 radiculopathy. One week later, the patient experienced fever and headache associated with pain, redness, and drainage at the site of the insertion of the left posterior pin. Computed tomography of the brain showed a 1.5-cm intracranial penetration of the halo pin through a previous cranioplasty of the temporal bone, associated with epidural abscess and cerebral edema in the left temporoparietal lobe. The pins and the halo vest were removed, the pin site was cleaned, and a Philadelphia cervical collar was applied. Staphylococcus epidermidis grew on the culture of drainage from the pin site. The patient started immediate intravenous antibiotic treatment for 2 weeks, followed by oral antibiotics for 2 additional weeks. RESULTS: The patient had gradual improvement of his symptoms within the first 48 hours. At the latest follow-up visit, he had fully recovered and his fracture had healed. CONCLUSIONS: The halo device should not be used for patients with a previous cranioplasty, especially if the pins cannot be inserted at other safe areas of the skull. A thorough medical history and physical examination of the skull are important before the application of a halo device. Computed tomography of the skull may be necessary before elective halo application for patients with concomitant head trauma, confusion, or intoxication and for patients with a previous cranioplasty to ascertain the safest pin sites.     

Complications of halo fixation of the cervical spine

Halo fixators play an integral role in stabilizing the cervical spine. They are most widely used after upper cervical to midcervical spine fractures and dislocations and as a supplement to various surgical fixation techniques. Compared with supine cervical traction techniques, halo fixators allow early patient mobilization and shorten hospital stays. The incidence of halo-fixator complications remains high. Minor complications include pin loosening, localized infection, periorbital edema, superficial pressure sores, and unsightly scars. Major complications include pin penetration, osteomyelitis, subdural abscess, nerve palsies, fracture overdistraction, and persistent instability. Many of these potential complications can be avoided with proper pin placement and meticulous pin care.     

头环背心在颈椎外科的应用

作者观察了用头环背心治疗多种原因所致颈椎不稳定的应用效果。用头环背心治疗了１０７例颈椎不稳定的病人，病种包括结核、损伤、肿瘤和畸形。病人分为非手术治疗组和融合术组。融合术包括寰枢椎后路融合术、枕颈融合术和下颈椎融合术。各种融合术都在头环背心的固定下施行，不用任何内固定。测量了２３例病人用头环背心固定前后的肺功能。１０７例病人中有８９例获得了随访，平均随访时间２５个月，非手术组的病人在头环背心固定下均恢复了颈椎的稳定性。在３１例行寰枢椎后路融合术的病人中有２９例融合成功（９４％），３６例行枕颈融合术的病人中有３２例达到了骨性愈合（８９％）。用头环背心固定的平均时间是１３３天，最长的４５０天。统计学结果显示：用头环背心固定后病人肺活量的均数与固定前相比差异有非常显著性（Ｐ＜０．０１），固定后肺活量减少约１３％。并发症包括颅钉松动（２４例）、钉孔感染（４例）、复位丢失（４例）、颅钉穿透颅骨内板（３例）、背心下皮肤压疮（１例）。作者认为头环背心对颈椎失稳的病人是一种安全、有效的外固定器材。借助这种装置，部分需行颈椎融合术的病人可以免去内固定，使手术更安全、简便。头环背心可使病人的肺活量减少。     

The halo vest: principles of application and management of complications

BACKGROUND: The halo skeletal device commonly is used both as primary treatment and as an adjunct to internal fixation in patients with cervical spinal injuries. For optimal outcome, the multidisciplinary team should have a basic understanding of the indications, design rationale, and complications associated with the halo skeletal fixator. DESIGN: Literature review. FINDINGS: The halo device provides the most rigid form of external cervical immobilization. Adherence to established application guidelines is critical to minimize morbidity. Safe zones for pin placement have been delineated. Protocols for management of pin-site infections have been established to appropriately manage these unfortunate complications. CONCLUSION: Although the halo is an effective form of cervical immobilization, complications with its use are encountered periodically. Familiarity with the design rationale, proper method of application, and potential complications can help to minimize the morbidity of this commonly used device.     

Six-pin halo fixation and the resulting prevalence of pin-site complications

BACKGROUND: In spite of the many advances in halo application technique, the prevalence of complications associated with the use of halo fixation remains high, particularly at the pin sites. Many practitioners do not use more than four pins for halo application in adults because they believe that it increases the risk of complications. The purpose of this study was to investigate the use of six pins in halo application, in order to determine if the extra pins increased fixation strength without increasing the overall pin-site complication rate. METHODS: The first part of our study consisted of force-deflection tests conducted on models of the skull fitted with either a four or a six-pin halo to determine if the six-pin halo provided greater fixation strength. Each skull model was placed in a servocontrolled hydraulic test machine; an axial distraction force was then applied until failure occurred. The second part of the study was a retrospective analysis of sixty-three patient records to document the prevalence of pin-site complications in patients treated with a six-pin halo system; these findings were then compared with established complication rates associated with four-pin halos. RESULTS: In the force-deflection tests, the mean load to failure of the six-pin halo construct (2879 N [647 lb]) showed the system to be significantly stronger (p = 0.0033) than the four-pin halo construct (1681 N [378 lb]). Of the sixty-three patient records reviewed, five (8% [95% confidence interval, 1% to 15%]) revealed pin-loosening; no infection was recorded for these five patients. One of the sixty-three patients had redness and erythema at "multiple sites," but these areas healed well. Another presented with infection at all six sites; this was recorded as an allergic reaction. CONCLUSIONS: Six-pin halo fixation results in greater halo strength and cervical spine stabilization without increasing the risk of pin-site complications. Clinical Relevance: Our findings are relevant for current clinical practice as the high complication rates associated with halo application have deterred some practitioners from using this type of fixation. The use of six pins, along with an improved protocol for halo application and care, may contribute to a more successful treatment outcome with fewer complications.     

The effect of pin location on the rigidity of the halo pin-bone interface

Optimal insertion of halo fixation pins to maximize the rigidity of the interface between the halo pins and the outer table of the skull is important in reducing the incidence of pin loosening. An in vitro biomechanical study was performed using cadaver skulls to investigate the effects of pin location on the rigidity of this pin-bone interface. Halo pins were inserted at nine positions within a recommended "safe zone" for pin insertion. It was found that the rigidity of the pin-bone interface progressively decreased as pins were inserted more superiorly on the calvaria. The rigidity of the interface did not change significantly when the location of the pins was varied in the horizontal axis. This reduction in interface rigidity associated with inserting pins more superiorly on the skull may be related to an increase in the angle of insertion of the pins with respect to the surface of the calvaria. Based on this study, a change in the technique of halo pin insertion is recommended. Pins should be placed as inferiorly as possible, close to the supraorbital ridge, to achieve the most perpendicular angle of insertion and thus the most rigid fixation. The improved rigidity obtained with perpendicular pin insertion may minimize the rate of pin loosening and other complications associated with use of the halo orthosis.     

The halo skeletal fixator. Principles of application and maintenance

The halo skeletal fixator, originally developed for use in patients with poliomyelitis, is now widely used with many types of cervical spine instabilities. Despite its demonstrated effectiveness, certain problem areas, including pin loosening and infection, have been identified. These problems have subsequently inspired detailed studies of skull osteology, biomechanics of pin fixation, and comparisons of techniques of application. Based on these studies, specific recommendations concerning the application and maintenance of the halo have developed. Anterior pin sites should be located in the safe zone approximately 1 cm superior to the orbital rim, cephalad to the lateral two-thirds of the orbit, and below the greatest circumference of the skull. The optimal posterior pin sites are located posterolaterally, diagonal to the corresponding contralateral anterior pins. Pins should be inserted perpendicular to the skull, tightened to eight inch/pounds (0.90 Newton-meter), and retightened once at 48 hours. A subsequent loose pin may be retightened once to eight inch/pounds if resistance is met; otherwise, it should be removed and a new one placed in a different location. Infected pins require antibiotic therapy, wound care, and possibly pin-site change and wound debridement.     

The halo fixator

The halo fixator may be used for the definitive treatment of cervical spine trauma, preoperative reduction in the patient with spinal deformity, and adjunctive postoperative stabilization following cervical spine surgery. Halo fixation decreases cervical motion by 30% to 96%. Absolute contraindications include cranial fracture, infection, and severe soft-tissue injury at the proposed pin sites. Relative contraindications include severe chest trauma, obesity, advanced age, and a barrel-shaped chest. In children, a computed tomography scan of the head should be obtained before pin placement to determine cranial bone thickness. Complications of halo fixation include pin loosening, pin site infection, and skin breakdown. A concerning rate of life-threatening complications, such as respiratory distress, has been reported in elderly patients. Despite a paucity of contemporary data, recent retrospective studies have demonstrated acceptable results for halo fixation in managing some upper and lower cervical spine injuries.     

The effect of angled insertion on halo pin fixation

This study evaluated the effect of angled insertion of halo pins on the biomechanical characteristics of the halo pin-calvarium complex. Halo pins were inserted into isolated calvarium sections at 90 degrees, 75 degrees, and 60 degrees to the surface of the bone at an insertional torque of 0.68 N-m (6 inch-pounds). Initial rigidity, load at failure, and deformation at failure of the pin-bone complex were assessed during transverse shear loading. The structural properties of the pin-bone complex were maximized at loads approaching failure when pins were inserted perpendicular (90 degrees) to the bony surface and significantly decreased at more acute angles of insertion. Perpendicular insertion of halo pins maximizes the structural properties of the complex formed by the halo pin and the calvarium. This improved structural behavior may minimize the incidence of pin loosening clinically, and may reduce the frequency of other complications currently associated with the use of the halo orthosis.     

Determination of minimum required halo pin force

The motivation for this study is to provide design guidance for a new halo system that minimizes pin loosening. If halo pin loosening can be substantially decreased with a new halo system, then the current standard of care of overtightening halo pins will not be necessary. Accordingly, there is a need to determine the halo pin force that should be applied to ensure adequate fixation. A biomechanical test was performed using cadaver head constructs, a custom halo fixture, and a tensile testing machine in an attempt to determine the relationship between the force required to dislodge a halo ring and the initial halo pin force. Three cadaver head constructs were tested at initial pin forces of 120, 240, and 360 N. For each test, the halo was pulled from a cadaver head with a displacement rate of 2.5 mm/min until the halo ring disengaged from the head. The vertical force that caused disengagement of the halo from the head was determined from the resulting load-displacement curves. A linear regression of the data predicts disengagement forces of 80, 320, and 570 N, respectively, for initial pin forces of 120, 240, and 360 N. The 95% prediction interval of disengagement forces for initial pin forces of 120, 240, and 360 N were +/-130, 120, and 130 N, respectively. A previously published study reported the maximum vertical load on a halo orthosis during patient usage to be 186 N. The lower 95% prediction interval from this study indicates that an average initial pin force of 230 N is necessary to prevent halo pin disengagement from a 186-N vertical load.     

Comparison of halo complications in adults and children

A retrospective analysis of 128 patients who underwent halo vest application for a variety of cervical spine problems was undertaken to determine complications associated with its use. Ninety-three (72%) were available for review. In comparison with a recent report, the complication rate was much lower. Only 8% of adults had major problems, consisting of pin tract infection and significant pin loosening requiring replacement. However, 39% (5 of 13) children had major problems. This report details our method of halo application and follow-up care.     

Complications in the use of the halo fixation device

The medical records of 179 patients were reviewed to identify complications related to the use of the halo external skeletal-fixation device. The complications that were identified included pin-loosening in 36 per cent of the patients, pin-site infection in 20 per cent, pressure sores under either a plastic vest or a plaster cast in 11 per cent, nerve injury in 2 per cent, dural penetration in 1 per cent, dysphagia in 2 per cent, cosmetically disfiguring scars in 9 per cent, and severe pin discomfort in 18 per cent. One hundred and eighty (25 per cent) of the 716 pins used had become loose at least once, and an infection had developed at sixty-seven pin sites (9 per cent). Two-thirds of the pins that were loose or associated with infection required change or removal. These complication rates, particularly of pin-loosening and infection, are exceedingly high. Attention to details in pin application, pin maintenance, and proper pin-site care may minimize the number of complications.     

Analysis of halo-orthoses application in children less than three years old

Purpose To evaluate the safety and efficacy of halo immobilization in children younger than 3 years. Methods All children less than 3 years of age who were placed in a halo-orthosis at a tertiary pediatric center were reviewed to determine the indications, safety, and efficacy of this method. Adequacy of immobilization and correct technique was established considering the chronology of maturation (skull and brain development). The functional outcome was analyzed. Results Ten patients (<3 years old) were identified from a total of 150 where halo ring/vest immobilization was used. There were six boys and four girls, with an average age of 2 years (range 10 months to 2 years and 10 months). The average time of immobilization in the halo-orthosis was 75 days (range 33–168 days), and the average follow-up time was 5 years and 2 months (range 1–12 years). There were two halo-related problems and four related to the index procedure. Halo-related problems included pin-site infection in one patient, and three pins loosening in another. There were four complications associated with the index procedure, all early in the series, including three cases of pseudarthrosis and one patient that had an insufficient decompression of basilar invagination. Two of the three failed fusions occurred at the occipito-cervical junction, which prompted us to develop new techniques for fusion at this level. Conclusions Halo-orthosis is a relatively safe and reliable device for immobilization of the upper cervical spine in children less than 3 years old. Understanding the developmental anatomy and a limited CT scan are helpful in pin placement. We recommend the use of a multiple pin construct, perpendicular insertion, and precise tightening with good pin-site care and frequent follow-up. The benefits seem to outweigh the risks in this population, considering the mechanical advantages of the halo-orthosis. The authors certify that their institution has approved the reporting of this study, that all the investigations were conducted in conformity with ethical principles of research, and informed consent was obtained.     

Intracranial penetration of a halo pin causing an epileptic seizure

A 71-year-old man with ankylosing spondylitis and an unstable fracture of the 6th and 7th cervical vertebrae was managed with a halo vest. Eight weeks following application the halo had shifted because of a loose pin. The patient's only complaint at the time was a headache but this was followed two days later by a seizure. An MR scan of the brain showed a swollen cortex under the right dorsal pin as a result of a perforation of the internal lamina by the pin. The halo was removed and anti-epileptic medication commenced. The patient had no further seizures.     

Management of cervical spinal fractures in ankylosing spondylitis with posterior fixation

STUDY DESIGN: Introduction of a posterior approach for internal fixation of fractures of the ankylosed cervical spine. OBJECTIVES: To evaluate the clinical outcome of patients with ankylosing spondylitis and cervical spinal fractures treated with posterior instrumentation and a collar orthosis. SUMMARY OF BACKGROUND DATA: Cervical spinal fractures in patients with ankylosing spondylitis almost always extend completely across the vertebral segment to include both anterior and posterior elements. Treatment with immobilization alone is often inadequate. Generalized spinal rigidity and exaggerated thoracic kyphosis may hinder anterior exposure. Posterior approaches have been described but generally require postoperative halo immobilization. In the authors' technique for patients whose spinal alignment is relatively well preserved, a posterior exposure is used that achieves three-point internal fixation along multiple segments. The complications associated with halo immobilization are avoided. METHODS: Seven patients with ankylosing spondylitis and fractures of the cervical spine were stabilized with posterior instrumentation. Patients were immobilized after surgery with either a cervical collar or a sternal occipital mandibular immobilizing brace and observed for neurologic outcome, radiographic evidence of bony fusion, and complications. RESULTS: No patient experienced neurologic deterioration with surgery. Two patients died at acute rehabilitative facilities after discharge. Radiographic evidence of fusion was observed in the five patients available for follow-up. CONCLUSIONS: Patients with ankylosing spondylitis and cervical spinal fractures can be adequately treated with lateral mass plating and interspinous wiring of autologous rib graft. Adequate postoperative immobilization can be attained with a cervical collar and does not require a halo vest.