gms | German Medical Science

Objective: Dorsal spondylodesis using a rod and either pedicle or lateral mass screw system is an alternative to anterior fusion techniques in degenerative, infectious, traumatic and tumorous cervical instability. For thoracolumbar instability undergoing pedicle screw fixation, the relation between improperly placed pedicle screws and lower fusion rates is established. A similar investigation was not yet performed in cervical dorsal spondylodesis.

Method: In 84 patients with cervical instability (trauma n=30, degeneration n=25, tumor n=13, infection n=12, other n=4) dorsal spondylodesis using a total of 460 screws, mainly lateral mass and pedicle screws, was performed. The accuracy of screw placement was assessed with postoperative CT. Lateral mass screws being too lateral or too close/in the facet joint, and pedicle screws breaching the pedicle medially or laterally or reaching the disc space were considered to be improperly placed. In all patients, a CT scan was re-done after one year for proof of fusion.

Results: Using the CT criteria, 11% of all lateral mass screws, 23.1% of all C7 pedicle screws and 12% of all upper thoracic pedicle screws were improperly placed. Revision was done only in 2 patients (2.4%) because of new radicular pain. Solid fusion was documented in 80 of 84 patients (95.2%) after one year.

Conclusions: In contrast to thoracolumbar pedicle screw fixation, improperly placed lateral mass and cervicothoracic pedicle screws have no or a very minor impact on solid fusion one year after surgery in all types of cervical instability.