Atlantoaxial Instability Treatment & Management
- Author: Daniel P Leas, MD; Chief Editor: Jeffrey A Goldstein, MD more...
There are no pharmacologic interventions for atlantoaxial instability (AAI). Because of the chronicity of the instability at the time of presentation in most cases, corticosteroids have little, if any, impact on neurologic findings and may present many undesirable outcomes. In the acute traumatic setting, corticosteroids remain controversial in the literature. Current guidelines provided by the American Academy of Neurological Surgeons (AANS) include level I evidence against the use of corticosteroids or gangliosides in the acute trauma patient.
Unless symptoms of spinal cord compression occur, AAI requires no treatment. Once symptoms arise, cervical spine stabilization is indicated until surgical stabilization is performed.
In persons with rotatory displacement, the time of presentation dictates the treatment. Most of these patients' conditions resolve spontaneously, and additional care is not sought.
Patients presenting with subluxation of less than 1 week's duration are treated with a soft collar and rest for a week. If close follow-up fails to document reduction, a period of halter traction with analgesics and muscle relaxants is warranted. If this fails, halo bracing can be undertaken.
In patients with rotatory displacement of more than 1 month's duration, a period of halo traction for 3 weeks is tried. Usually, two types of patients are in this group: (1) those whose subluxation resolves with bracing but recurs when bracing stops and (2) those who usually present with a fixed deformity.
The treatment goals for persons with AAI are to protect the spinal cord, stabilize the spinal column, decompress neural tissue, and reduce any deformity. In most cases, the injury is purely ligamentous and unlikely to heal. Therefore, these injuries are typically treated with posterior C1-2 fusion. If computed tomography (CT) revealed a bony avulsion injury as the source of failure, a trial of halo bracing may be initiated.
On the basis of the Fielding and Hawkins grading scale, the following general treatment recommendations may be made:
Type I - Stable subluxations, treated conservatively in a collar
Type II - Potentially unstable, treated at the physician's discretion
Type III - Unstable, requires surgical stabilization
Type IV - Unstable, requires surgical stabilization
Potential surgical options for C1-2 fixation fusion include the following[34, 35, 36, 37, 38, 4, 39, 40, 41, 42, 43, 44, 45, 46, 47] :
Transarticular screws (TASs) along the posterior elements
Screw-rod constructs (SRCs) along the C1 lateral mass and C2 pedicle (or the C2 spinous process if the C2 pedicle is not accessible)
Posterior sublaminar wiring as described by Brookes or Gallie
The surgeon should always be wary of associated adjacent injuries or pathology so as to include potential fusion extension cranially to the occiput or to caudal vertebral segments. For example, rheumatoid arthritis (RA) can also have cranial settling or subaxial instability. In addition, possible poor bone quality should be considered in selecting the method of fixation.
In a 2014 meta-analysis of the literature, Elliot et al compiled 69 articles reviewing both TASs and SRCs.[48, 49, 50] Although there were some relevant differences in population characteristics (eg, age, graft source, and gender), outcomes were generally comparable and successful. Rates of fusion were 97.5% and 94.6%, favoring SRC; differences in the rates of vertebral artery injury (4.1% vs 2.0%) and malpositioned screws (7.1% vs 2.4%) were noted, also favoring SRC.
It is important to highlight an anatomic anomaly known as the arcuate foramen, through which the vertebral artery travels in approximately 15% of the population. The presence of this anomaly necessitates adapting the trajectory of the C1 lateral mass screw so as to prevent iatrogenic injury to the transiting artery.[51, 52]
C1 laminar hooks with C2 pedicle screw fixation appear to be an effective mode of treatment in the trauma population, though the limited evidence currently available does not support a change in practice.
Pediatric patients account for the majority of cases of nontraumatic rotatory displacement. Initially, these patients are treated with a halo brace; however, if this treatment is unsuccessful because of a fixed deformity or recurrent deformity, posterior fusion of C1-2 is required.
Posterior cervical spinal fusion can successfully treat symptomatic AAI in many cases.[54, 55] Surgery is most successful for treating patients with ligamentous instability and less successful in treating patients with osseous instability. Optimal results have been obtained in patients with severe pain and mild myelopathy. Thus, detecting symptoms early is preferable for the most successful treatment.
Surgery is not recommended for individuals without spinal cord involvement due to an unclear natural history of AAI.
In individuals with RA, the goals of surgery are to relieve neural compression, relieve pain, and address instability. Indications for surgery include the following :
Atlantoaxial subluxation (AAS) of greater than 8 mm with evidence of cord compression on dynamic flexion-extension view
Posterior atlantodental (or atlanto-dens or atlas-dens) interval (ADI) of 14 mm or less
More than 3.5 mm of subaxial subluxation
Progressive neurologic deficit
Special care should be taken to avoid excessive flexion or extension of the neck.
Extreme caution should be used in performing any procedure with sedation or neck manipulation on patients with known risk factors for, or a previous diagnosis of, AAI. Neutral positioning of the neck should be maintained during these procedures and all surgical procedures, especially otorhinolaryngologic procedures. Care also should be taken during anesthetic administration to avoid trauma to the atlantoaxial joint.
Children should be monitored closely postoperatively for any signs of neurologic involvement.
Before participation in sports, evaluations are recommended to detect neurologic involvement.
Spinal cord compression can arise or worsen if susceptible patients are subjected to extreme ranges of motion. Special care should be taken to avoid excessive flexion or extension of the neck.
Special Olympics, Inc, currently requires that all children with Down syndrome who compete in Special Olympics games undergo radiographic and neurologic examinations to exclude AAI. Individuals with AAI are restricted from participation in certain activities that may result in cervical spine injury. These include gymnastics, diving, pentathlon, butterfly stroke, diving starts in swimming, high jump, soccer, and certain warmup exercises.
In 1983, the American Academy of Pediatrics Committee on Sports Medicine and Fitness issued a statement in agreement with the recommendations and requirements of the Special Olympics. However, a review of evidence in 1995 caused the committee to rescind their recommendations that all children with Down syndrome should be screened radiographically.
Although no indication exists that children with asymptomatic AAI are at increased risk for subluxation or progression to symptomatic AAI or that routine screening by radiographs is necessary, recommendations vary.
Consultations that may be considered include the following:
Neurosurgeon or orthopedic spine surgeon
In children without a preexisting diagnosis, a geneticist or endocrinologist
Individuals with predisposing factors should be monitored carefully for neurologic symptoms indicative of symptomatic AAI. In individuals with Down syndrome and an ADI of greater than 5 mm, the recommendation is to avoid contact sports or activities with high risk of flexion injury. When the ADI is more than 10 mm or neurologic findings develop, a fusion is recommended.
Regular assessments of the history and physical examinations, including evaluations before participation in sports, are recommended to detect neurologic involvement.
Patients also should be monitored carefully for development of symptoms, though the association between AAI and neurologic symptoms is unclear.
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