John P. Dormans, Gokce Mik, and Purushottam A. Gholve
DEFINITION
The occipitocervical articulation is formed by the occiput, the atlas (C1), and the axis (C2). This functional unit provides a large degree of mobility and range of motion through the strong ligamentous structures and cup-shaped joints.
Over 50% of the total axial rotation occurs between the first and second vertebrae, while flexion–extension movement predominantly occurs at the occipitoatlantal junction.2
Excessive movement at this junction due to either bony or ligamentous abnormalities causes instability. A wide variety of pathologies such as genetic and congenital developmental abnormalities, trauma, tumors, and inflammatory and degenerative conditions can lead to upper cervical spine instability.
Depending on the degree of displacement and spinal canal compromise, cord compression and myelopathy may occur.
Major instability is usually addressed with surgical occipitocervical or C1–C2 arthrodesis. Since Foerster first described a technique for occipitocervical arthrodesis using fibular strut graft in 1927, several procedures have been reported with variable rates of fusion and techniques of stabilization.
In this chapter, brief information on upper cervical spine instability is given and general principles of occipitocervical and C1–C2 arthrodesis are discussed. Also our techniques developed for posterior occipitocervical fusion are described in detail.
ANATOMY
It is important to understand that the pediatric upper cervical spine is not a “miniature model” of the adult spine. The cervical spine approaches adult size and shape by ages 8 to 12, as growth cartilage fuses and vertebral bodies gradually lose their oval or wedge shape and become more rectangular.
The upper cervical spine has unique development, anatomy, and biomechanics.
The atlas develops from three ossification centers, a body and two neurocentral arches, which become visible by age 1 year (FIG 1A).
The neurocentral synchondroses fuse with the body at about 7 years of age and may be mistaken for fractures on radiographs.14
The axis is derived from five primary ossification centers: the two neural arches or lateral masses; the two halves of the dens; and the body.
There are two secondary centers: the ossiculum terminale and the inferior ring apophysis (FIG 1B).
The two halves of the odontoid are generally fused at birth but may persist as two centers, known as the dens bicornis.15
The dentocentral synchondrosis, which separates the dens from the body, closes between the ages of 5 and 7 (FIG 1B). Until the ossification is complete, it gives the appearance of a “cork in a bottle” on an open-mouth odontoid view.
The tip of the dens appears at age 3 years and is fused by age 12.
Occasionally, it remains as a separate ossiculum.11,15
After skeletal maturity the atlas does not have a body as such, and is shaped like a ring. The flat, cup-shaped articular surface under the occipital condyle allows for flexion, extension, and some bending. The dens articulates with C1 through the dorsal facet of the anterior arch. C1–C2 articulation allows for rotation.2 The vertebral artery passes through the foramen that is located in the transverse processes.
The ligamentous structure allows for a wide range of motion of the upper cervical spine while maintaining stability. The short ligaments at the base of the skull are as follows (FIG 1C):
Tectorial membrane, which is a continuation of the posterior longitudinal ligament that provides considerable support.
Cruciate ligament, which includes transfer ligaments, restrains against atlantoaxial anteroposterior translation.
Alar and apical ligaments, which run from foramen magnum to the odontoid, act as secondary stabilizers.
PATHOGENESIS
Fundamentally, upper cervical spine instability can develop from osseous or ligamentous abnormalities resulting from acquired or congenital disorders. As a result of instability, excessive motion and spinal cord compression may occur at the occipitoatlantal and atlantoaxial joint or both.
In nontraumatic conditions, ligamentous laxity (particularly in the transverse ligament) or abnormalities of the odontoid cause instability.
In Grisel syndrome, a type of atlantoaxial rotatory displacement, inflammation of the retropharyngeal space, caused by upper respiratory tract infections or by adenotonsillectomy, spreads through the pharyngovertebral veins to the ligaments of the upper cervical spine. This results in impairment of the transverse atlantal ligament and instability.21
In Down syndrome, the main cause of atlantoaxial instability is the laxity of the transverse ligament, which holds the dens against the posterior border of the anterior arch. Also, malformation of the odontoid can be observed in this condition.9
Klippel-Feil syndrome is associated with congenital cervical anomalies, such as occipitocervical synostosis, basilar impression, and anomalies of the odontoid, and can be associated with instability, stenosis, or both.
Odontoid anomalies include aplasia, hypoplasia, duplication, third condyle, persisting ossiculum terminale, and os odontoideum.
The atlantodental interval (ADI), which is measured from the anterior aspect of the dens to the posterior aspect of the anterior ring of the atlas, increases in atlantoaxial instability. It is a way of assessing the more important space available for the cord. The transverse ligament serves as the first line of defense, maintaining the atlanto–odontoid interval.
In older children (older than 8 years) and adults, the ADI should be 3 mm or less, while in younger children, the ADI should be 4 mm or less (some consider 4.5 to 5 mm acceptable).12
FIG 1 • Anatomy ossification centers of the atlas and axis during development, and the alar, apical, and transverse ligaments.
In children, we consider an ADI of 4 mm or more as evidence of atlantoaxial instability.
NATURAL HISTORY
Patients with upper cervical instability frequently have other associated pathologic conditions in the occipitocervical region such as spinal stenosis, basilar impression, cervical fusions, occipitalization, or congenital anomalies of the atlas or axis (dens), and central nervous system abnormalities.
When one encounters one of these conditions, others should be sought also.
Instability of the upper cervical spine and stenosis often are two major factors in the development of myelopathy.
Patients who are symptomatic at initial presentation are often at risk for progressive neurologic symptoms. Once cervical myelopathy develops it rarely resolves entirely.
Paralysis and death are rare but may be encountered in patients with upper cervical spine instability.
PATIENT HISTORY AND PHYSICAL FINDINGS
Upper cervical spine instability is rare in patients without predisposing conditions or trauma.
The instability is usually determined in radiographic examination of the children with syndromes or conditions known to have frequent involvement of the musculoskeletal system.19
An orthopedic surgeon is usually consulted for children with such conditions.
Clinical presentation can vary because of the associated syndromes and anomalies.
Patients may present with symptoms such as loss of range of motion, stiffness, mechanical pain of the head or neck, and torticollis.
It is not uncommon to see patients presenting with neurologic symptoms, which can vary from minor sensory or motor disturbances to established myelopathy. Neurologic symptoms or signs result from mechanical compression of the spinal cord or nerve roots.
Torticollis may be the presenting symptom of rotatory or postinfectious atlantoaxial instability.
According to the degree of compression and the affected site of the spinal cord, signs and symptoms can vary. They may include loss of physical endurance, difficulty walking, weakness, and upper motor neuron signs (spasticity, hyperreflexia, clonus, Babinski sign), which can be seen with anterior spinal column involvement.
Pain deficits and proprioception and vibratory sense deficits can be seen with posterior spinal column involvement.
Increased nasal resonance may also be observed. It may occur because of the decreased size of the nasopharynx resulting from anterior displacement of the atlas.
Vertebral artery distortion and insufficiency may lead to bizarre symptoms such as syncopal episodes, sudden postural collapse without unconsciousness, change in behavior, dizziness, and seizures.
In cerebellar involvement nystagmus, ataxia and incoordination are the common findings.
Neurogenic bladder and bowel, cranial nerve involvement, paraplegia, hemiplegia, and quadriplegia should be kept in mind; sometimes the patient presents with only one of these findings.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Standard radiographs include anteroposterior, open-mouth odontoid, and lateral (neutral and flexion–extension) cervical spine views.
Instability can be identified on the lateral flexion–extension view. Atlantoaxial instability is diagnosed on the basis of an increased ADI (FIG 2A).
In children older than 8 years and in adults, the ADI should be 3 mm or less, while in younger children the ADI should be 4 mm or less (some consider 4.5 to 5 mm acceptable).12
In children, we consider an ADI of 4 mm or more as evidence of atlantoaxial instability. This measurement does not always correlate with the degree of brainstem or cord compression (as seen on MRI), however. An asymptomatic patient may have instability.
Space available for the spinal cord (SAC) is measured from the posterior border of the dens to the anterior border of the posterior tubercle. According to Steel's rule of thirds,17 SAC should be about one third of the diameter of the ring of atlas (FIG 2A).
This safe zone allows for some degree of pathologic displacement. Displacement of more than one third of the diameter causes cord compression.
This measurement directly describes the space available for the spinal cord, which is highly associated with the neurologic involvement.
The relationship between the foramen magnum, atlas, and odontoid can be determined in lateral radiographs.
The ADI is measured from the anterior aspect of the dens to the posterior aspect of the anterior ring of the atlas (FIG 2A).
In older children (older than 8 years) and adults, the ADI should be 3 mm or less.
In younger children, the ADI should be 4 mm or less (some consider 4.5 to 5 mm acceptable).
The line of McRae connects the anterior rim of the foramen magnum to the posterior rim (FIG 2A).
The upper tip of the odontoid should normally be 1 cm below the anterior margin of the foramen magnum.
If the effective sagittal diameter of the canal (length of the line) is less than 19 mm, neurologic symptoms occur.
The line of Chamberlain is drawn from the posterior margin of the hard palate to the posterior margin of the foramen magnum (see Fig 2).
The tip of the odontoid should be 6 mm below this line. It bisects the line in basilar invagination. However, determination of the landmarks can be difficult on plain radiographs.
The McGregor line is drawn from the most caudal point of the occipital projection to the posterior edge of the hard plate (FIG 2A).
This line is one of the best for detecting basilar impression because the osseous landmarks can usually be seen at all ages. If the tip of the odontoid process lies more than 4.5 mm above this line, the finding is consistent with basilar impression.
The line of Wackenheim is drawn parallel to the posterior surface of the clivus (FIG 2A).
The inferior extension of the line should be in touch with the posterior tip of the odontoid. In basilar invagination it is over that line.
The Wiesel-Rothman line is drawn connecting the anterior and posterior arches of the atlas. Two lines are drawn perpendicular to this line, one through the basion and the other through the posterior margin of the anterior arch of the atlas (FIG 2B).
A change in the distance (x) between these lines of more than 1 mm in flexion and extension indicates increased abnormal translational motion.
The ratio of Power is calculated from a line drawn from the basion to the posterior arch of the atlas and a second line from the opisthion to the anterior arch of the atlas (FIG 2C). The length of the first line is divided by the length of the second.
FIG 2 • A. Lateral craniometry of the craniocervical junction with landmarks, commonly used lines, and methods for examining the relationship between the atlas, odontoid, and foramen magnum and measuring the space available for the spinal cord (SAC). The atlantodental interval (ADI) is measured from the anterior aspect of the dens to the posterior aspect of the anterior ring of the atlas. The McRae line connects the anterior rim of the foramen magnum to the posterior rim. The Chamberlain line is drawn from the posterior margin of the hard palate to the posterior margin of the foramen magnum. The McGregor line is drawn from the most caudal point of the occipital projection to the posterior edge of the hard palate. The Wackenheim line is drawn parallel to the posterior surface of the clivus. B. Method for calculating the Wiesel-Rothman line for atlanto-occipital instability. A line is drawn connecting the anterior and posterior arches of the atlas (line 1–2). Two lines are drawn perpendicular to this line, one through the basion and the other through the posterior margin of the anterior arch of the atlas (line 3). A change in the distance (x) between these lines of more than 1 mm in flexion and extension indicates increased abnormal translational motion. C. Lines used to calculate the Power ratio. A line is drawn from the basion (B) to the posterior arch of the atlas (C) and a second line from the opisthion (O) to the anterior arch (A) of the atlas. The length of the first line is divided by the length of the second. (Adapted from Copley LA, Dormans JP. Cervical spine disorders in infants and children. J Am Acad Orthop Surg 1998;6:204–214.)
A ratio of less than 1.0 is normal.
A ratio of 1.0 or more is abnormal and is diagnostic of anterior occipitoatlantal dislocation.
MRI is useful to identify pathologic changes at the dura mater and spinal cord as well as additional soft tissue pathologies.
Functional MRI scans performed in flexion and extension can be used to assess dynamic brainstem or cord compression.
CT scan can provide additional information regarding the bony anomalies.
In atlantoaxial rotational displacement, pathoanatomy is determined by fine-cut dynamic CT scan with left–right rotation of the head.
DIFFERENTIAL DIAGNOSIS
Pseudosubluxation
Os odontoideum
Congenital muscular torticollis
Ankylosing spondylitis
NONOPERATIVE MANAGEMENT
Children with known risk of upper cervical instability should be evaluated carefully. Especially patients with congenital syndromes associated with upper cervical spine instability should have periodic clinical and radiographic examinations until maturity.19
Upper cervical spine radiographs including anteroposterior (AP), lateral (neutral and flexion–extension views), and openmouth odontoid views are obtained periodically to assess and detect any trends and changes.
Patients and parents should be educated about the diagnosis and natural history of the disorder and encouraged to report any symptoms as soon as they occur.
Because of bone and ligament abnormalities, patients with upper cervical spine instability have a greater risk of spinal cord injury even with minor trauma and even when they are asymptomatic.
As previously described, periodic observation should be done and if any progression is noticed, the patient should be prepared for appropriate surgical stabilization when indicated.
In children we consider an ADI of 4 mm or more as evidence of atlantoaxial instability. Documented significant instability at the atlanto-occipital or atlantoaxial joints is an indication for posterior arthrodesis of occiput–C2 and C1–C2 arthrodesis, respectively.
In some congenital disorders such as Morquio syndrome, progression of the instability is frequent; in these cases prophylactic fusion should be considered before neurologic symptoms occur.19
However, in Down syndrome, the patients with instability are usually asymptomatic and in most cases signs and symptoms progress slowly. Restriction of high-risk activities usually is appropriate. If the clinical symptoms persist or neurologic symptoms are starting to occur in the setting of significant instability, surgical treatment is indicated.9,16
Children with congenital fusion of cervical vertebrae (mostly in Klippel-Feil syndrome) should be restricted from high-risk sports. Patients with progressive symptomatic segmental instability or neurologic compromise are candidates for surgical stabilization.18
SURGICAL MANAGEMENT
The main indication for the posterior occiput–C1 or C1–C2 arthrodesis is instability of the atlanto-occipital or atlantoaxial joint.
For occipitoatlantal instability and instability with congenital or acquired (because of removal of tumor or laminectomy) defects of posterior elements, we developed two techniques of occipitocervical arthrodesis at our institution.
Rib graft technique
Iliac graft technique
Many techniques of atlantoaxial fusion using cables, transarticular screws, plates, and bone graft materials have been described. For isolated atlantoaxial instability, we commonly prefer the Gallie technique, the Mah modified Gallie technique, and the Brooks sublaminar wire technique.
Preoperative Planning
Plain radiographs and CT scans are reviewed and any osseous findings noted.
MRI evaluation for the spinal cord compression is recommended.
An appropriate halo ring is measured for the patient.
Somatosensory evoked potentials, transcortical motorevoked potentials, and electromyography are the preferred neurologic monitoring modalities.
Flexible fiberoptic intubation with manual in-line axial stabilization should be considered to minimize cervical motion during intubation maneuvers.
Positioning
After induction of general anesthesia in the supine position, a halo ring is applied, and the patient is carefully turned to the prone position.
The halo device is fixed to the Mayfield positioning device, which is securely fixed to the operating table (FIG 3).
Lateral fluoroscopy or radiography should be done before starting the procedure to confirm the alignment of the occiput and cervical spine.
Donor sites (rib or ilium) are also prepared for graft harvesting.
Approach
The posterior midline incision is made from the occiput to the intended distal fusion site (usually C2) for occipitocervical arthrodesis.
The paraspinal muscles are elevated with a Cobb elevator and retracted laterally. Excessive lateral dissection should be avoided to prevent any damage to the vertebral artery, which runs in a serpentine course in relationship to the C2 vertebra.
For occipitocervical arthrodesis, the dissection is carried proximally to the occipital protuberance and distally to the level planned to include the fusion.
For atlantoaxial arthrodesis, the dissection is started from the lower occiput and the surgeon identifies the posterior arch of the atlas, the bifid spinous processes, and the lamina of the axis.
The surgical exposure of vertebra is limited up to the intended level of fusion to prevent unintentional inclusion of the adjacent level in the fusion mass.
FIG 3 • A. Prone position with halo fixed to Mayfield positioning device (Integra Corporation). B. Side view.
TECHNIQUES
OCCIPITOCERVICAL ARTHRODESIS WITH ILIAC GRAFT
At the level below the transverse sinus, four transverseoriented holes are drilled through both cortices of the occiput with a high-speed diamond drill.7
The holes are aligned transversely with two on each side of the midline. At least 1 cm of intact bone should be left between the holes to prevent wire pullout through the skull (TECH FIG 1A).
Surgical loupes and a headlamp are recommended for this procedure.
Using a high-speed diamond burr, the surgeon makes a transverse-oriented trough into the base of the occiput to fit the rectangular superior part of the iliac autograft.
A single corticocancellous autograft (3 × 4 cm) is harvested through an oblique incision over the posterior superior iliac spine.
A rectangular graft is taken. The surgeon creates a notch in the inferior base of the graft to be suitable for the base of the spinous process of the second or third vertebra (TECH FIG 1B).
16 or 18-gauge wire is passed through the burr holes on each side of the midline and the wire is looped on itself (TECH FIG 1C,D).
A sublaminar wire is placed under the ring of C2 or C3 (or passed through the base of the spinous process, if structurally sufficient, or if there is canal stenosis).
The left side of the graft accepts the left end of the wire and the right end of the graft accepts the right end of the wire (TECH FIG 1E).
The edges of the graft are contoured to fit appropriately into the occipital trough and around the base of the spinous process (TECH FIG 1F).
The wires are tightened over the graft in figure 8 shape. After satisfactory tightening the edges of the wire are cut and bent away from skin (TECH FIG 1G,H).
Intraoperative fluoroscopy or radiography is used to confirm the alignment of the occiput and cervical spine, stability, and the position of the graft and wires.
The graft should be structurally stable at the end of the procedure.
Flexion–extension of the halo frame, better contouring of the graft, and appropriate tightening of the wires can be used to make adjustments in reduction and alignment.
TECH FIG 1 • A. Four transverse-oriented occipital burr holes and rectangular trough. B. Corticocancellous rectangular graft with a notch at the inferior base of the graft. C. A Luque wire is passed through the occipital burr hole and another wire is passed sublaminarly under the arch of C2 or through the base of the C2 spinous process. D. Occipital wire is looped on itself. E. Schematic drawing showing occipital wire looped on itself and the wire passed through the base of the C2 spinous process. F. Graft (arrow) placed between the occiput and C2. G. The wires are tightened over the graft in a figure 8 shape, twisted, and cut. H. Schematic drawing showing the graft placement and securing with wires.
OCCIPITOCERVICAL ARTHRODESIS WITH RIB GRAFT
An oblique incision overlying the posterior rib allows for adequate exposure.3
The muscle fibers are separated and dissection is carried down to the periosteum of the rib.
Adequate rib is exposed and cut.
The size of the rib graft is greater than the area to be fused because part of the rib is used as morcelized graft.
Using a rib cutter, the graft is cut distally and proximally and removed (TECH FIG 2A).
Irrigation fluid is placed in the surgical site and positive pressure applied to check for pleural leaks.
If a pleural tear is detected, air can be removed from the chest cavity by using a red rubber tube and suction.
A larger leak may require placement of a thoracostomy drainage tube.
In all patients, a chest radiograph should be taken after rib harvest to rule out pneumothorax.
Two full-thickness structural grafts are prepared to fit the arthrodesis site.
The rib grafts can span large defects and fit nicely into large or abnormally shaped skull, and we find this best for young infants.
16 or 18-gauge wire is looped through the burr holes on each side of the midline (see TECH FIG 1C).
The burr holes are drilled and aligned similarly to the ones described for the iliac graft technique.
There is no need to create a groove at the base of the occiput.
Braided cable or no. 5 Mersilene sutures may be used instead of wire.
With Mersilene sutures there is a reduced risk of cutting out in thin bone of poor quality.
After this, purchase of two wires is made to the posterior elements of most caudal vertebra on each side of the midline by sublaminar wiring.
Suitable grafts on either side are then secured to the occiput and lamina of the most caudal vertebra by wires.
The stability of the grafts is checked under radiographic control and the wires are then crimped and cut (TECH FIG 2B,C).
Adjustments are made by flexion–extension of the halo frame, contouring of the graft, and appropriate tightening of the wire.
Intraoperative radiographs are obtained to confirm acceptable reduction, alignment, and placement of the graft.
For both techniques, morcellized autograft is packed into the arthrodesis site. The wound is closed in layers.
The halo vest is worn for 8 to 12 weeks after both techniques to maintain postoperative stability (TECH FIG 2D,E).
TECH FIG 2 • A. Adequate rib is exposed and harvested. B. Rib graft is placed and fixed with braided cables and #5 Mersilene suture. C. Schematic drawing showing the rib graft fixed with wire. D,E. A 5-year-old-boy immobilized with a halo vest postoperatively. (C: Adapted from Cohen MW, Drummond DS, Flynn JM, et al. A technique of occipitocervical arthrodesis in children using autologous rib grafts. Spine 2001;26:825–829.)
POSTERIOR C1–C2 ARTHRODESIS
The preoperative planning is similar to that for the occipitocervical arthrodesis described earlier in the section.
Gallie Technique
After exposing the posterior arch of the atlas and spinous process of the axis, the two free ends of a single 16 or 18-gauge wire are passed beneath the posterior arch of the atlas from a superior-to-inferior direction.10
The free ends are passed beneath the posterior arch and are brought around superiorly to loop on themselves.
A rectangular corticocancellous autograft is harvested from the posterior iliac spine.
A notch is created at the distal part of the graft. This part will be placed across the spinous process of the axis.
The notched graft is placed between the posterior portion of the arch of C1 and the posterior spinous process of C2.
Now the free ends of the looped wire are brought down over the graft and passed below the spinous process.
TECH FIG 3 • Gallie technique for atlantoaxial arthrodesis.
The free ends of the wire are tightened and twisted over the graft (TECH FIG 3).
Morcellized bone grafts may be packed into the fusion area to add additional support.
Intraoperative fluoroscopy is necessary to check for satisfactory reduction and alignment of C1–C2.
Mah Modified Gallie Technique
In 1989, Mah described a modification of the Gallie technique.13
All the steps of the Mah technique are similar to the Gallie technique, except that a threaded Kirschner wire is placed through the spinous process of the C2 and both ends of the Kirschner wire are cut, leaving about 2.5 cm of the total wire.
The free ends of the looped wire are brought down below the free ends of the threaded Kirschner wire (TECH FIG 4).
The free ends of the wire are tightened, secured, and crimped over the graft.
TECH FIG 4 • Mah modified Gallie technique for atlantoaxial arthrodesis.
Brooks Technique
A standard posterior midline incision is used to expose the posterior arch of C1 and the lamina of C2.1
Two sublaminar wires are passed under both C1 and C2 laminas, one on each side of the midline.
Unlike the Gallie technique, two separate corticocancellous grafts are required in this technique. A single rectangular iliac crest graft is harvested; it can be separated into two equal parts.
Each iliac crest graft is cut into a trapezoid-like shape (one end is narrower than the other) so that they can be wedged between the C1 and C2 posterior arches (TECH FIG 5A).
The grafts are snugly wedged into place. The wires are then tightened around the grafts, twisted, and cut (TECH FIG 5B).
TECH FIG 5 • Brooks arthrodesis. A. Lateral view demonstrating a wedge-shaped graft between the spinous processes to prevent hyperextension. The graft is shaped so that one end is narrower than the other to achieve a good fit. B. The grafts are snugly wedged between the C1 and C2 posterior arches, and the wires are tightened around the grafts.
POSTOPERATIVE CARE
Postoperative management includes halo vest immobilization for 8 to 12 weeks.
Using a standardized method of halo application reduces the rate of complications associated with halo use in children.5
The rate of pin-track infection with prolonged use of a halo device in children is similar to that in adults. Particular care should be taken to keep the pin-track sites clean.6
Short-term antibiotic treatment is usually satisfactory in decreasing inflammation at the pin site.
When a bony union is documented radiographically, the halo device is removed.
Patients can gradually return their daily activities.
Special care should be taken to avoid excessive flexion or extension of the neck.
Long-term follow-up is necessary for evaluation of potentially progressing junctional instability below the level of fusion.
The additional stress placed on the adjacent vertebrae below the level of fusion may result in instability with time.8
OUTCOMES
The senior author (JPD) presented results of the CHOP technique for occipitocervical arthrodesis in 38 children with more than 2 years of follow-up.20
Thirty-four patients were treated with iliac crest autograft and posterior wiring, or with rib autograft and posterior wiring, and the remaining four with Luque contoured rod and autograft.
Thirty-four patients had bony union, three patients had fibrous union, and one patient had nonunion.
Ninety-seven percent of the patients (37 children) showed baseline or improved neurologic status at the most recent follow-up.
Complications included.
Superficial infection treated with oral antibiotics (three patients)
Postoperative pneumonia (one patient)
Pin-tract infection: most of the patients treated with a halo ring had superficial pin-site infection. All but two patients were treated with oral antibiotics. One patient required intravenous antibiotics and the other required a pin change.
In 11 patients (29%), we had a distal extension of the fusion mass, seven patients had fusion at one additional level, and four patients had fusion at two additional levels.
COMPLICATIONS
Graft or wire breakage
Nonunion, insufficient fusion
Additional fusion levels and loss of motion
Junctional instability distal to the fusion mass
Infection
Deep wound infection
Meningitis
Pin-tract infections (halo)
Neurologic injury
Donor site morbidity
REFERENCES
· Brooks AL, Jenkins EB. Atlanto-axial arthrodesis by the wedge compression method. J Bone Joint Surg Am 1978;60:279–284.
· Bogduk N, Mercer S. Biomechanics of the cervical spine. I: Normal kinematics. Clin Biomech 2000;15:633–648.
· Cohen MW, Drummond DS, Flynn JM, et al. A technique of occipitocervical arthrodesis in children using autologous rib grafts. Spine 2001;26:825–829.
· Copley LA, Dormans JP. Cervical spine disorders in infants and children. J Am Acad Orthop Surg 1998;6:204–214.
· Copley LA, Dormans JP, Pepe MD, et al. Accuracy and reliability of torque wrenches used for halo application in children. J Bone Joint Surg Am 1993;85:2199–2204.
· Dormans JP, Criscitiello AA, Drummond DS, et al. Complications in children managed with immobilization in a halo vest. J Bone Joint Surg Am 1995;77:1370–1373.
· Dormans JP, Drummond DS, Sutton LN, et al. Occipitocervical arthrodesis in children. J Bone Joint Surg Am 1995;77A:1234– 1240.
· Dormans JP, Wills BPD. Junctional instability and extension of fusion mass associated with posterior occipitocervical arthrodesis in children. Presented at POSNA 2004 Annual meeting, St. Louis, MO, April 2004.
· Doyle JS, Lauerman WC, Wood KB, et al. Complications and longterm outcome of upper cervical spine arthrodesis in patients with Down syndrome. Spine 1996;21:1223–1231.
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· Locke GR, Gardner JI, VanEpps EF. Atlas-dens interval (ADI) in children: a survey based on 200 normal cervical spines. AJR Am J Roentgenol 1966;97:135–150.
· Mah J, Thometz J, Emmans J, et al. Threaded K-wire spinous process fixation of the axis for the modified Gallie fusion in children and adolescents. J Pediatr Orthop 1989;9:675–679.
· Ogden JA. Radiology of postnatal skeletal development: XI. The first cervical vertebra. Skeletal Radiol 1984;12:12–20.
· Ogden JA. Radiology of postnatal skeletal development: XII. The second cervical vertebra. Skeletal Radiol 1984;12:169–177.
· Segal LS, Drummond DS, Zanotti RM, et al. Complications of posterior arthrodesis of the cervical spine in patients who have Down syndrome. J Bone Joint Surg Am 1991;73:1547–1554.
· Steel HH. Anatomical and mechanical considerations of the atlantoaxial articulation. In Proceedings of the American Orthopaedic Association. J Bone Joint Surg Am 1968;50:1481–1482.
· Tracy MR, Dormans JP, Kusumi K. Klippel-Feil syndrome: clinical features and current understanding of etiology. Clin Orthop Relat Res 2004;424:183–190.
· Wills BPD, Dormans JP. Nontraumatic upper cervical spine instability in children. J Am Acad Orthop Surg 2006;14:233–245.
· Wills BPD, Drummond DS, Schaffer A, et al. Posterior occipitocervical arthrodesis in children: intermediate and long-term outcomes. Presented at AAOS 2005 Annual Meeting, Washington, DC, February 2005.
· Wilson BC, Jarvis BL, Handon BC. Nontraumatic subluxation of the atlantoaxial joint: Grisel's syndrome. Ann Otol Rhinol Laryngol 1987;96:703–708.