eMedicine Specialties > Sports Medicine > Spine

Atlantoaxial Injury and Dysfunction

Chris G Koutures, MD, FAAP, Specialist Physician/Intercollegiate Athletics Team Physician, California State Fullerton Student Health; Consulting Staff, Department of Pediatrics and Sports Medicine, Gladstein and Koutures, A Professional Corporation
Chantal D Simpson, MD, Staff Physician, Department of Emergency Medicine, Lincoln Hospital of New Jersey; John Munyak, MD, Associate Program Director, Director of Sports Medicine Education, Department of Emergency Medicine, Lincoln Medical and Mental Health Center
Contributor Information and Disclosures

Updated: Mar 7, 2008

Introduction

Background

Disability and instability of the unique atlantoaxial joint result in controversies regarding the management of acute trauma and also the screening evaluation of particular at-risk individuals. The purposes of this article are to define atlantoaxial instability (AAI); describe the relatively rare symptomatic lesions with significant morbidity and mortality; and, finally, discuss the rationale for and against screening and restricting the activities of at-risk individuals.

Definition

AAI, also known as atlantoaxial subluxation, is radiologically identified increased mobility or laxity between the body of the first cervical vertebra (atlas) and the odontoid process of the second cervical vertebra (axis).^{1, 2, 3, 4, 5} The subluxation can be anterior, posterior, or lateral, and symptoms occur as a result of cervical cord impingement.

Epidemiology

Although traumatic lesions involving the atlantoaxial region are relatively rare, certain disease states and conditions present a higher theoretic risk of instability due to increased atlantoaxial joint laxity.

Surveys indicate 10-25% of patients with trisomy 21 have AAI.^{6, 7} Two thirds of these cases are due to laxity of transverse ligament, whereas one third are due to abnormal odontoid development. Although this association has been depicted on radiographs, the clinical incidence of serious cervical spine injury is not increased in this population compared with other populations.

About 25% of patients with rheumatoid arthritis have atlantoaxial instability, which is thought to be due to chronic inflammation.⁸ Congenital skeletal dysplasias may cause resultant odontoid hypoplasia. Marfan syndrome may involve ligamentous laxity, and acute inflammatory processes can affect the retropharyngeal, neck, or pharyngeal spaces.

For excellent patient education resources, visit eMedicine's Back, Ribs, Neck, and Head Center and Sports Injury Center. Also, see eMedicine's patient education article Neck Strain.

Frequency

United States

Approximately 15-25% of all patients with trisomy 21, and about 25% of patients with rheumatoid arthritis have atlantoaxial injury or dysfunction.^{6, 7, 8}

Functional Anatomy

The articulation of the odontoid process of C2 (axis) with the anterior arch of C1 (atlas) allows for 50% of cervical lateral rotation. The transverse and alar ligaments maintain joint integrity and limit posterior motion of the odontoid process relative to the C1 anterior arch. Abnormal posterior translation (or subluxation) can cause cervical cord impingement with the potential for significant neurologic compromise and even death.

Sport-Specific Biomechanics

During extremes of cervical flexion or extension, competent transverse and alar ligaments limit posterior translation of the odontoid process. Incompetent ligaments or a damaged odontoid process can allow for significant translation and potential damage in cases of cervical hyperflexion or hyperextension in which axial compression is delivered to the head and cervical spine. Given the potentially serious sequelae of significant atlantoaxial dysfunction, patients with defined instability are restricted from participating in contact sports and in sports requiring significant cervical flexion or extension.^{1, 4, 9}

Clinical

History

Most patients with atraumatic AAI are asymptomatic.^{1, 2, 3, 4, 5} Clinical evidence of the condition is usually not detected until the subluxation is severe enough to cause damage to the spinal cord. Many patients do not present with active disease; rather, these patients are evaluated because of requests for screening radiography or for guidance regarding sports participation. This condition is rarely discovered as an incidental finding during radiologic evaluation for an acute neck injury. During such evaluations, the clinician must obtain a full history to provide adequate management, such as the following:

• In obtaining the history, a review of any current or past neck trauma, head injury, or fall is essential, especially in children. Previous spine trauma may have resulted in an improperly healed odontoid injury that causes instability and neurologic symptoms years later.
• A complete review of the patient's medical history is also important because many medical conditions are associated with an increased incidence of AAI.
• In individuals examined for screening radiography or sport-specific counseling, it is important to obtain a full description of past symptoms as well as their desired sports participation. Certain organizations, such as the Special Olympics, have a mandatory radiographic requirement for participation in certain events.⁶ Screening neurologic examination and review of symptoms is also part of the preparticipation evaluation.
• Individuals with symptomatic AAI may present with nonspecific symptoms, including neck pain, limited range of motion, and torticollis.
  • A history of worsening symptoms (eg, headache, fatigue, transient upper-extremity paresthesias) with neck flexion is particularly revealing.
  • Other symptoms may include distal muscle weakness and spasticity, gait disturbance, and bowel and/or bladder dysfunction.
  • Quadriplegia due to cord compression is another dramatic presentation.

Related eMedicine topics:
Spinal Cord Trauma and Related Diseases
Torticollis

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Physical

• In any case of suspected head or cervical spine injury (including cases of unconsciousness or altered mental status) primary on-field management of the patient includes an assessment of the airway, breathing, and circulation (ABCs), with immediate stabilization of the cervical spine in a neutral position.
  • Great caution must be placed into maintaining the airway without compromising the injured cervical spine. Note: If intubation is needed in the field, use the jaw-thrust maneuver rather than cervical extension.
  • The injured athlete should not be moved in any fashion until he or she is properly placed on a rigid backboard and the head and neck is immobilized with a rigid cervical collar and head stabilization device.
  • For an athlete wearing a helmet and/or shoulder pads, special precautions must be taken. For example, the helmet and pads should be removed only if the responders are trained in the proper technique or if the initial screening radiographs are negative.
• Arranging for expedient and safe transport is another immediate priority.
• A complete neurologic examination can wait until the athlete is in a more controlled environment.
• Any athlete who leaves the field with neck pain, limited cervical range of motion, extremity weakness, or paresthesias should be considered at high risk for a cervical spine injury. The athlete should be removed from the activity pending a full evaluation before any considerations of return to play.
• High-dose intravenous steroids should be considered in patients with suspected cervical cord injuries to reduce spinal cord swelling.
• Formal physical examination of the spine and extremities should be limited until unstable lesions of the cervical spine are ruled out. Once the atlantoaxial joint and cervical spine are deemed stable, further examination can proceed.
  • In the office setting, the clinician must use the history to rule out potentially unstable lesions before performing a full physical examination.
  • The cervical neck examination includes an assessment of the cervical range of motion, palpation of the cervical spine, and performance of the Spurling maneuver (ie, axial load on head with neck extension and lateral rotation toward each shoulder). Paresthesias radiating past either shoulder signify a positive Spurling maneuver for cervical nerve root impingement.
  • Full reflex, motor, and sensory examination of the upper extremity is also indicated, with the neck in neutral as well as in a flexed position.
  • The physical findings are often completely normal in patients with radiographically documented AAI but who have no symptoms.

Causes

Symptomatic AAI is due to acute trauma, usually cervical hyperflexion, hyperextension, or a direct axial load on the head or cervical spine. Although this type of injury can occur in any athlete, certain conditions predispose an individual to AAI dysfunction and disability. These include congenital odontoid anomalies, such as odontoid aplasia, odontoid hypoplasia, and a separate odontoid process; os odontoideum, which is due to nonunion of an early childhood fracture and which creates an unstable lesion or ligamentous laxity; and acute or chronic inflammatory processes.

Related eMedicine topic:
Os Odontoideum

References

• Athletes With Disabilities
• Atlantoaxial Injury and Dysfunction
• Brachial Plexus Injury
• Cervical Disc Injuries
• Cervical Discogenic Pain Syndrome
• Cervical Facet Syndrome
• Cervical Radiculopathy
• Cervical Spine Acute Bony Injuries
• Cervical Spine Sprain/Strain Injuries
• Concussion
• Myofascial Pain in Athletes
• Repetitive Head Injury Syndrome
• Thoracic Outlet Syndrome

• Back, Ribs, Neck, and Head Center
• Sports Injury Center
• Neck Strain Overview
• Neck Strain Causes
• Neck Strain Symptoms
• Neck Strain Treatment