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Atlantoaxial Instability
Comprehensive guide to atlantoaxial instability - C1-C2 pathology, Down syndrome association, ADI measurement, surgical stabilization and fusion techniques for orthopaedic exam
πWhat is Atlantoaxial Instability?
Comprehensive guide to atlantoaxial instability - C1-C2 pathology, Down syndrome association, ADI measurement, surgical stabilization and fusion techniques for orthopaedic exam
π¬What Causes It?
- Down syndrome (15-20% have atlantoaxial instability) - lax ligaments due to collagen abnormality
- Rheumatoid arthritis - inflammation destroys transverse ligament and causes C1-C2 erosion
- Congenital bone abnormalities - os odontoideum (separate odontoid process), hypoplastic odontoid
- Trauma - fracture of odontoid (dens) or rupture of transverse ligament
- Infection - Grisel syndrome (pharyngitis causing inflammatory laxity)
- Connective tissue disorders - Ehlers-Danlos syndrome, Marfan syndrome (ligament laxity)
β οΈRisk Factors
You may be at higher risk if:
- Down syndrome - 15-20% have AAI, 1-2% develop symptomatic spinal cord compression
- Rheumatoid arthritis - 25-30% have C1-C2 involvement
- Previous neck trauma or fractures
- Family history of connective tissue disorders
- Participation in contact sports or gymnastics (especially with Down syndrome - now contraindicated)
π‘οΈPrevention
- βDown syndrome children: Screening cervical spine X-rays at age 3-5 years (before starting contact sports) and repeat at age 12 years - identify AAI before symptoms
- βSTRICT activity restrictions for Down syndrome with AAI: NO contact sports, gymnastics, diving, trampolining, soccer headers (Special Olympics banned list)
- βRheumatoid arthritis patients: Aggressive disease control with DMARDs and biologics reduces AAI incidence, cervical spine screening X-rays at diagnosis and every 2-3 years
- βConnective tissue disorder patients (Ehlers-Danlos, Marfan): Avoid high-impact activities and contact sports, regular cervical spine monitoring
- βPost-trauma: Prompt assessment and treatment of odontoid fractures or transverse ligament injuries prevents chronic AAI
- βGrisel syndrome prevention: Early treatment of pharyngitis/tonsillitis in children, awareness of torticollis as red flag (not just 'stiff neck')