Neuronavigation and 3D fluoroscopy-guided lag screw reduction and osteosynthesis for traumatic spondylolistheses of the axis: a path worth exploring?
OBJECTIVE In traumatic spondylolistheses of the axis, there is a marked heterogeneity of the observed injury patterns, with a wide range of the severity-from stable fractures, which can be treated conservatively with very good success, to highly unstable fractures, which should be treated surgically. A number of classification systems have been devised to assess the instability of the injuries and to derive a corresponding therapy recommendation. In particular, the results and recommendations regarding medium-severity cases are still inconclusive. Minimally invasive percutaneous procedures performed using modern techniques such as 3D fluoroscopy and neuronavigation have the potential for improvements in the therapeutic outcome and procedural morbidity against open surgical procedures and conservative therapy. METHODS A minimally invasive method using 3D fluoroscopy and neuronavigation for percutaneous lag screw osteosynthesis of the pars interarticularis was performed in 12 patients with a Levine-Edwards Type II fracture. Ten patients had an isolated hangman's fracture and 2 patients had an additional odontoid fracture of the axis (Type II according to the Anderson and D'Alonzo classification system). Complications, operating parameters, screw positions, and bony fusion were evaluated for the description and evaluation of the technique. RESULTS In 6 men and 6 women, percutaneous lag screw osteosynthesis was performed successfully. Correct placement could be verified postoperatively for all inserted screws. In the case series, nonunion was not observed. In all patients with a complete follow-up, a bony fusion, an intact vertebral alignment, and no deformity could be detected on CT scans obtained after 3 months. CONCLUSIONS The percutaneous pars interarticularis lag screw osteosynthesis is a minimally invasive and mobility-preserving surgical technique. Its advantages over alternative methods are its minimal invasiveness, a shortened treatment time, and high fusion rates. The benefits are offset by the risk of injury to the vertebral arteries. The lag screw osteosynthesis is only possible with Levine-Edwards Type II fractures, because the intervertebral joints to C-3 are functionally preserved. A further development and evaluation of the operative technique as well as comparison with conservative and alternative surgical treatment options are deemed necessary.