Procedure 4 Odontoid Screw Fixation
Indications
For surgical fixation of recent (less than 6 months old) type II and some high type III odontoid fractures (Figure 4-1, A and B)
Indications Pitfalls
• Type III fractures with significant vertebral body involvement because of poor proximal screw fixation
• Transverse ligament disruption (atlantodental interval [ADI] >3 mm). Although magnetic resonance imaging (MRI) has been recommended by some for evaluation of transverse ligament rupture, the authors do not recommend this modality unless neurologic deficits or increased ADI are identified. In the authors’ experience, transverse ligament rupture in the setting of odontoid fracture is very rare.
• Chronic nonunion. Fractures older than 6 months or fractures with sclerotic margins have a much lower fusion rate and should be treated by posterior atlantoaxial arthrodesis.
• Nonreducible canal compromise. Intraoperative reduction has been considered more feasible by a posterior approach in combination with atlantoaxial arthrodesis; however, the guide-tube system to be described allows realignment intraoperatively before placement of an odontoid screw. In the authors’ experience, almost all acute fractures are reducible with traction or intraoperatively.
• Anterior oblique fractures (posterior superior to anterior inferior) can be difficult to reduce and maintain in good alignment with odontoid screw fixation (Figure 4-2, A). Because the screw crosses the fracture line at an angle, and thus tends to pull the odontoid anteriorly, these fractures have lower fusion rates. In the authors’ previously reported series, patients with anterior oblique fractures had an approximately twofold greater risk of nonunion after odontoid screw fixation than did those with horizontal or posterior oblique fractures (anterior superior to posterior inferior) (Figure 4-2, B). By fixing these fractures with the odontoid positioned in a slightly posterior position and using a hard collar type of external orthosis, the authors have usually been able to achieve successful fixation and healing in these patients.
Indications Controversies
• Type III fractures (Figure 4-2, C)
• Chronic nonunion. Although it has been reported that chronic nonunion can be treated with curettage and odontoid screw fixation, the fusion rates are very low, and this fracture is probably better treated with posterior C1-C2 fusion.
• Treatment of the elderly. In the authors’ experience, this procedure is well tolerated in older patients and allows for early mobilization with fewer general medical complications. The incidence of temporary postoperative dysphagia is greater in this group.
• Most cost-effective alternative
• Procedure is suited for patients of all ages, including the elderly.
Examination/Imaging
Treatment Options
• Nontreatment may be considered for severely debilitated elderly patients.
• External orthoses have poor fusion rates except in younger patients. The worst fusion rates occur in older patients, patients with fractures with large gaps or subluxations, and those with comminuted fractures.
• Treatment with all forms of external orthosis requires close follow-up and 3 to 6 months of significant activity restrictions.
