Threaded interbody fusion cage for adjacent segment degenerative disease after previous anterior cervical fusion

Anterior discectomy and fusion have been used for over 50 years in the treatment of degenerative disease of the cervical spine. However, as these procedures become more common, the long-term consequences are becoming more evident. One such consequence is degeneration of an adjacent segment, which can occur in up to 17% of patients undergoing cervical fusion. A threaded interbody fusion cage has often been used in a primary degenerative disorder of the cervical spine. However, there have been no studies in which these cages have been used in adjacent segments after previous cervical fusion. This is a retrospective review of 7 patients to determine the fusion rate, operative utility, and clinical outcomes using a threaded fusion cage construct in the treatment of cervical adjacent segment degeneration.

A standard low-profile interbody fusion cage was implanted after standard discectomy and local vertebral body bone graft in 7 patients with documented radiographic adjacent segment degeneration and clinical disease after anterior cervical fusion. Each patient underwent clinical and radiographic evaluation, and all 7 patients demonstrated signs of radiculopathy and/or myelopathy as well as radiographic signs of degeneration referable to a motion segment adjacent to previous cervical arthrodesis. These evaluations were repeated postoperatively. Patients were also asked to fill a preoperative and postoperative VAS, NDI, Prolo Economic-Functional Rating System, and CNDS for evaluation of outcome.

Each procedure was performed without complication. The mean VAS pain scale decreased 58% as a result of the surgery. The CNDS improved in all patients by an average of 42%. The NDI improved in all patients, with an average increase of 42%. The Prolo Economic-Function Status showed that 4 patients had an excellent outcome and 3 patients had a good outcome. There was no incidence of pseudoarthrosis in any procedure at the 24-month follow-up.

These preliminary results support the use of threaded interbody cages in adjacent segment degeneration of the cervical spine after previous anterior cervical fusion. Pain and functional scores improved in all cases. This technique should be among the possibilities for surgical treatment of degeneration of adjacent segments in patients with previous cervical spinal fusion.