Halo Fixation Research Articles

The halo skeletal fixator: current concepts of application and maintenance.

The halo device provides the most rigid cervical immobilization of all cervical orthoses. Despite its established efficacy, reported complications include pin loosening (36% to 60%), pin-site infection (20% to 22%), severe pin discomfort (18%), ring migration (13%), pressure sores (4% to 11%), unacceptable scars (9% to 30%), nerve injury (2%), dysphagia (2%), prolonged bleeding at pin sites (1%), and dural puncture (1%). Appreciation of skull anatomy and established application guidelines can help minimize these complications. A relative "safe zone" for anterior pin placement is located 1 cm above the orbital rim, superior to the lateral two thirds of the orbit. This position avoids injury to the nearby frontal sinus (medially), temporalis fossa (laterally), and sensory nerves (supraorbital and supratrochlear nerves medially, and zygomaticotemporal nerve laterally). Posterior pin positions are less critical, located roughly diagonal to the contralateral anterior pins. Pins should enter the skull perpendicular to the cortex, with the ring or crown sitting below the equator of the skull, passing about 1 cm above the helix of the ear. Pins are inserted at 8 in-lbs and re-tightened once at 48 hours. A loose pin can be re-tightened to 8 in-lbs if resistance is met; otherwise, a loose pin requires replacement in a nearby site. Superficially infected pins are managed with oral antibiotics and local pin care. Refractory infections require pin removal, parenteral antibiotics, and incision and drainage as indicated. Dysphagia (difficulty in swallowing), produced by exaggerated cervical extension, may necessitate repositioning of the C-spine. Dural pin puncture is managed with hospitalization, antibiotics, and elevation of the head of the bed to decrease cerebrospinal fluid pressure and allow dural healing.(ABSTRACT TRUNCATED AT 250 WORDS)

A device for stable intra-operative positioning and for reduction of unstable injuries of the cervical spine

The Problem Unstable and displaced fractures and dislocations of the cervical spine should be reduced as early as possible using image intensification in instances of conservative or operative treatment. For the maintenance of the reduction the halo fixator has proved to be eminently suitable. To position patients on the operating table the halo vest must be removed creating a dangerous situation: a recurrence of the displacement or dislocation. Proper and stable positioning of the cervical spine maintaining the physiologic lordosis is also very important during the fusion of less unstable injuries. With the presently available devices it is impossible to change the chosen position during the intervention which is of great disadvantage having undesirable consequences. Special headrests are available for positioning. The longitudinal traction is maintained with a Crutchfield tongue, a Glisson sling, or with straps around the chin of the patient. The attached extension ropes run over a special attachment with pulleys at the head of the operating table; extension is achieved by weights. A calibrated distraction which can be altered at will during surgery is not possible with these methods. A reduction in more than one plane and maintainance of a stable positioning resisting vibrations is also not possible with these devices. These conditions, however, must be met for a perfect reduction and a speedy uneventful course of surgery particularly in instances of certain injuries such as fractures of the dens or pathological fractures. It is for these reasons that we developed a device meeting these conditions (Figure 1).

Investigation of How Different Halos Influence Pin Forces

This study investigated the effect of the size and material of halo rings on the pin force produced at the halo pin-calvarium complex. Loosening of halo pins has been a problem with using the halo-vest apparatus to stabilize cervical spine fractures. One standard halo pin and seven different halo rings were used to test the anterior pin hole of each ring at a constant torque of 8 inch-pounds (0.9 Nm). Pin force fluctuated from halo to halo, and decreased as the nut was tightened. Identical torques applied to different halos will not guarantee the same magnitude of pin force for halo fixation.

Diagnosis and Management of Occipital Condyle Fractures

THE AUTHORS RECENTLY treated three cases involving fractures of the occipital condyle. First described by Bell in 1817, this lesion has proven to be very rare, with only 32 cases previously reported in the literature. Plain films often do not reveal any abnormality, making diagnosis difficult. High-resolution computed tomography has been demonstrated to be very sensitive in diagnosing this lesion. This fact was borne out in the authors' series. All of the authors' patients were managed either with a Philadelphia collar or with halo fixation, with excellent outcomes.

Diagnosis and Management of Occipital Condyle Fractures

The authors recently treated three cases involving fractures of the occipital condyle. First described by Bell in 1817, this lesion has proven to be very rare, with only 32 cases previously reported in the literature. Plain films often do not reveal any abnormality, making diagnosis difficult. High-resolution computed tomography has been demonstrated to be very sensitive in diagnosing this lesion. This fact was borne out in the authors' series. All of the authors' patients were managed either with a Philadelphia collar or with halo fixation, with excellent outcomes.

Management of Traumatic Supraorbital Neuroma

Traumatic neuromas represent proliferative overgrowth of axons, Schwann cells, and fibroblasts at the proximal end of nerve injury or transsection. Although common elsewhere, traumatic neuromas have rarely been noted in the orbits. All but one of these reported lesions occurred after orbital surgery. We present a patient with a painful traumatic neuroma of the supraorbital nerve due to application of a halo fixation device. Neuroma resection and microneural repair resulted in prompt resolution of symptoms without compromise of nerve function.

Management of Traumatic Supraorbital Neuroma

Traumatic neuromas represent proliferative overgrowth of axons, Schwann cells, and fibroblasts at the proximal end of nerve injury or transsection. Although common elsewhere, traumatic neuromas have rarely been noted in the orbits. All but one of these reported lesions occurred after orbital surgery. We present a patient with a painful traumatic neuroma of the supraorbital nerve due to application of a halo fixation device. Neuroma resection and microneural repair resulted in prompt resolution of symptoms without compromise of nerve function.

Occipitocervical arthrodesis in children.

A technique for occipitocervical arthrodesis was used in seven patients whose ages ranged from three to thirteen years. The indication for the arthrodesis was occipitocervical instability secondary to various forms of dysplasia. There were no non-unions, and internal fixation was used in only one patient. Six patients were immobilized postoperatively with halo fixation. There was only slight limitation of cervical motion after fusion; we believe that the limitation was due to increased motion in the vertebral segments caudad to the level of fusion. Six patients had full flexion, and only three patients had decreased rotation. We found that, in young patients, occipitocervical arthrodesis by means of the described procedure was both safe and effective.

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 Effect of Pin Location on the Rigidity of the Halo Pin-Bone Interface

Abstract 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 pinbone 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. (Neurosurgery 26:238-241. 1990)

Möglichkeiten und Grenzen der Therapie von Halswirbelverletzungen mit dem Halo-Fixateur

74 patients were treated with a Halo-thoracic brace in the Department of Traumatology of the AK St. Georg between 1980 and 1986. Of these, 61 had fractures of the cervical spine, nine had tumor-osteolysis, and four had inflammatory destructions of the vertebrae. In almost all cases of fractures of the upper cervical spine (C0-C2) bone healing occurred with applying the Halo fixation alone. In the middle and lower cervical spine, however, secondary operative measures were often necessary because of persistent instabilities, redislocations or neurologic disturbances. New experience in the palliative treatment of malignant osteolysis of the cervical spine shows, that restabilisation of the segments concerned can be achieved by the combined use the Halo apparatus, surgical resection of the involved vertebral bodies with bone grafting and radiotherapy. A new radiolucent Halo apparatus broadens diagnostic and therapeutic facilities.

A biomechanical analysis of halo fixation in children.

The use of prolonged halo stabilisation in a child is increasingly indicated for trauma and congenital instability of the cervical spine, but complications of pin fixation in this age group are frequent. We have analysed four aspects of the mechanics of the halo pin: the forces applied by each of six surgeons was shown to vary widely, penetration of the inner table occurred relatively easily, friction at the pin-halo interface influenced forces, and the skull thickness measured by CT scan varied from 1.1 mm to 4.3 mm in children under six years of age. We recommend CT scanning of the skull before elective halo application in young children to ascertain the safest pin sites.

Complications in the use of the halo fixation device.

Complications in the use of the halo fixation device.

Structural behavior of the halo orthosis pin-bone interface: biomechanical evaluation of standard and newly designed stainless steel halo fixation pins.

The structural response of the halo orthosis pin-bone interface to transverse loading was evaluated on an Instron testing machine using fresh cadaver calvarium sections. Commercially available stainless steel (control) pins and newly designed stainless steel experimental pins were evaluated. Cyclic loading tests and load-to-failure tests were performed. Of the many designs tested, one pin demonstrated an improvement in structural properties at the pin-bone interface compared with the control pin. Furthermore, the new pin design was more resistant to insertional torque reduction when subjected to cyclic loading after insertions at 4 and 6 in-lb. Both the control and experimental pins exhibited improved structural behavior at 8 in-lb of insertional torque compared to the currently recommended 6 in-lb.

Skull osteology as it affects halo pin placement in children.

Skull bone thicknesses of 18 pediatric skulls were measured by means of computerized tomography scans to determine optimal sites for placement of halo pins. Skulls were grouped to assess changes with age: Group 1, 1-2 years; Group 2, 2-5 years; and Group 3, 5-12 years. At the antero- and posterolateral portions of the calvaria, the average total thickness was 3.7 and 3.9 mm, respectively, in Group 1; this value increased relatively linearly to 6.1 and 5.9 mm, respectively, in Group 3. At the temporal fossa, the average thickness increased from 3.0 mm in infants to 4.1 mm in preteenagers. These findings confirm clinical recommendations that halo fixation pins should be placed anterolaterally and posterolaterally where the bones are thickest.

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.

Brain abscess as a complication of cranial traction

A case of cerebral abscess developing as a late complication of cervical traction by means of Crutchfield tongs is reported and compared with 18 published cases of cerebral abscess after cranial traction with tongs or halo fixation. Penetration of the inner table by the pins of the tongs or halo unit seems to be the main cause of this complication. The literature is reviewed.

Spinal cord injury without radiographic abnormalities in children.

Spinal cord injury in children often occurs without evidence of fracture or dislocation. The mechanisms of neural damage in this syndrome of spinal cord injury without radiographic abnormality (SCIWORA) include flexion, hyperextension, longitudinal distraction, and ischemia. Inherent elasticity of the vertebral column in infants and young children, among other age-related anatomical peculiarities, render the pediatric spine exceedingly vulnerable to deforming forces. The neurological lesions encountered in this syndrome include a high incidence of complete and severe partial cord lesions. Children younger than 8 years old sustain more serious neurological damage and suffer a larger number of upper cervical cord lesions than children aged over 8 years. Of the children with SCIWORA, 52% have delayed onset of paralysis up to 4 days after injury, and most of these children recall transient paresthesia, numbness, or subjective paralysis. Management includes tomography and flexion-extension films to rule out incipient instability, and immobilization with a cervical collar. Delayed dynamic films are essential to exclude late instability, which, if present, should be managed with Halo fixation or surgical fusion. The long-term prognosis in cases of SCIWORA is grim. Most children with complete and severe lesions do not recover; only those with initially mild neural injuries make satisfactory neurological recovery.

Brain abscess as a complication of halo fixation

Brain abscess as a complication of halo fixation

Brain abscess as a complication of halo fixation.

The clinical course of a patient with a brain abscess that developed at the pin site of a halo brace is described. The care of the patient with the halo brace and methods to prevent complications are discussed.