C1-2 Posterior Cervical Fusion

Nonhealed Odontoid Fractures (Types II and III)

• Patients initially treated with immobilization who develop pseudarthrosis are not ideal candidates for subsequent anterior odontoid screw fixation attempts because the material from the pseudarthrosis occupies the fracture line, which often prevents contact between the fractured surfaces.

• Type III odontoid fractures with atlantoaxial joint fracture combinations and type III odontoid fractures with associated Jefferson fracture are unstable and may be treated with posterior C1-2 stabilization.

• Patients may also have ligamentous laxity and thus C1-2 instability. Ligamentous instability of C1-2 is identified with measurements of the atlantodental interval on flexion and extension views. Normally, this interval should not exceed 2 to 3 mm in adults. When the atlantodental interval exceeds 5 mm in nonrheumatoid patients and when it exceeds 7 to 8 mm in rheumatoid patients, there is instability of the C1-2 complex and posterior C1-2 fixation is indicated.

• Atlantoaxial rotatory dislocations are an indication for C1-2 fixation. This problem can often be treated via a posterior reduction and fusion approach (see Fig. 55.2).

• Congenital malformations of C2 (e.g., os odontoideum, odontoid agenesis), degenerative diseases, inflammatory diseases (e.g., rheumatoid arthritis), tumors, and infections (e.g., osteomyelitis) can produce instability of the atlantoaxial complex requiring C1-2 fixation.

• Postsurgical dynamic instability relating to odontoidectomy or C1 and C2 laminectomies with or without removal of adjoining facets is an indication for posterior C1-C2 fixation.