Improvement of Cervical Sagittal Angulation Using Dynamic Stabilization Implant

Introduction:

This is a consecutive case prospective study to evaluate the results of anterior cervical decompression and fusion (ACDF) using the Acromed "DOC" system. Previous investigators have shown that most anterior cervical fusions show some amount of settling during the maturation phase. The "DOC" system is designed to allow controlled intervertebral settling in order to maintain load–sharing necessary for successful fusion and prevent instrumentation failure.

Methods:

38 patients(20 females, 18 males)underwent ACDF using the "DOC" systems. Average age was 46 years(range 33–69). Eight patients had single–level procedures, 24 multiple levels, 5 corpectomies and 1 corpectomy and multi–level ACDF. Autologous iliac crest graft was used in 24 patients; 13 had iliac allograft and 1 fibular allograft. Instrumentation ranged from C3 to T1. Average follow–up was 82 days (range 25–142 days). Indications for surgery were trauma (2 patients), cervical spondylotic radiculopathy (25), and/or myelopathy(2) and herniations(9). X–rays were reviewed by an independent radiologist at two time points and evaluated for settling, sagittal alignment and subluxation. The first time point was intra– or preoperatively; the second was at an average of 1 3 weeks follow–up (range 4–26 weeks). Based on the most recent film, the levels treated were assessed as either "fused", "fusing/incorporating", or "not fused".

Results:

Average settling noted was 1.2mm. Most patients had settled by 4 weeks postoperatively. The average sagittal angle initially was 1 degree lordotic (range 43 degrees kyphosis to 19 degrees lordosis) and postoperatively was 6 degrees lordotic(range 12 degrees kyphosis to 27 degrees lordosis). Change in sagittal angle was 5 degrees lordotic(range 17 degrees kyphosis to 33 degrees lordosis). Postoperatively, 85.7% of patients had total resolution of neck pain while 14.3% had mild residual pain. Arm pain resolved in 85.7% of patients postoperatively; 11.4% had mild residual pain and 2.9% had moderate residual pain. Based on an average follow–up of 13 weeks (4–26 weeks), an 84.8% fusion rate was seen. The remainder was not fully incorporated at the time. Two cases of mild screw back out from platform and one case of screws through the disc space inferiorly were seen. Six patients had dysphagia, sore throat or airway problems, one of which was significant and required temporary PEG tube placement. Four patients had complaints of pain or tingling at the donor site.

Discussion/Conclusion:

The Acromed "DOC" system provides excellent dynamic stabilization of anterior cervical fusions, improves sagittal alignment postoperatively and enhances fusion rates. No instrumentation failure requiring revision surgery occurred in this series.