1. Occipito-atlantal dislocation. This is often fatal and those who survive require immediate immobilization in a halo. Traction should be avoided. Later posterior fusion should be considered.
2. Atlas fractures. These are rare.
3. Atlanto-axial instability. There are three principal patterns:
• Transverse ligament rupture can be acute or chronic. The chronic rupture is associated with Down's syndrome, Klippel—Feil syndrome and some skeletal dysplasias. In these cases, posterior fusion should be considered if the atlanto-dens interval is >10 mm, or if there is neurological compromise. The acute case is surgically stabilized.
• Odontoid peg fractures typically occur through the basal physis and the diagnosis is recognized on the lateral X-ray. Treatment consists of either a Minerva cast or a halo for 6 weeks. An os odontoideum is most probably an old undiagnosed peg fracture and if unstable or associated with neurological impairment, a C1/C2 fusion can be performed.
• Atlanto-axial rotatory instability classically presents with a torticollis, the 'cock robin' deformity, after an upper respiratory tract infection. Plain radiographs are difficult to interpret and the diagnosis is most easily made on CT. The condition should be treated seriously as cases of neurological deficit and even death are reported. Fielding and Hawkins classify four types:
Type 1: no AP shift.
Type 2: <4 mm anterior shift.
Type 3: >4 mm anterior shift.
Type 4: posterior shift of the atlas on the axis.
Treatment is usually a soft cervical collar and NSAIDs. In the more resistant cases, halter traction or even open reduction and posterior fusion, may be required.
4. C2 spondylolisthesis. The 'Hangman's fracture' is rare in children and treated by immobilization in a Minerva cast or halo.
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