Traumatic Spondylolisthesis of the Axis — NEJM
Traumatic Spondylolisthesis of the Axis
Overall, the clinical evidence regarding traumatic spondylolisthesis of the axis is very low and mainly based on small case series, expert opinion, laboratory findings, and theoretical considerations.
5 Traumatic Spondylolisthesis of the Axis (Hangman’s Fracture) D
The traumatic spondylolisthesis of the axis accounts to 5% of all cervical spine injuries and is defined by a bilateral separation of the C2 vertebral body from the neural arch. The precise location of the fracture line may vary widely. For understanding the pathobiomechanics, the involvement of the C2–C3 disk is essential. Although its synonym “hangman's fracture” suggests an extension moment as primary injury mechanism, flexion moments are also proven to cause such fracture morphology. The axial force vector (distraction versus compression) is thought to have a significant effect on the neurologic involvement. The most widely accepted classifications, according to Effendi and modified by Levine, regard the displacement of the C2 vertebral body and possible locking of the facet joints. For decisions on conservative versus surgical therapy, a definitive statement about the stability is essential. The stability is determined by involvement of the C2–C3 disk and longitudinal ligaments, which frequently cannot be assessed by X-ray or computed tomography alone. The assessment of this soft tissue injury therefore requires additional imaging either by magnetic resonance imaging to display the disk and longitudinal ligaments or dynamic fluoroscopy to assess functional behavior of the C2–C3 motion segment. If stability is proven, an immobilization of the cervical spine in a semirigid cervical collar is sufficient. Unstable lesions require surgical stabilization. The standard procedure is an anterior C2–C3 diskectomy and fusion, because of the lower morbidity of the anterior approach and the motion preservation between C1 and C2. In rare cases (irreducible locked facet joints, the necessity of decompression of the vertebral artery, contraindication for anterior approach), a posterior approach is sometimes necessary. Isolated direct screw osteosynthesis is of little value, because it only makes sense in cases with an intact C2–C3 disk, which is usually regarded as stable and therefore might be treated conservatively.