Because single-level disk arthroplasty or arthrodesis in the lower subaxial spine improves headaches after surgery, we studied whether this effect may be better appreciated after two-level arthroplasty.Methods
We performed an independent post hoc analysis of two concurrent prospective randomized investigational device exemption trials for cervical spondylosis, one for single-level treatment and the other for two adjacent-level treatments.Results
For the one-level study, baseline mean headache scores significantly improved at 60 months for both the cervical disk arthroplasty (CDA) and anterior cervical diskectomy and fusion (ACDF) groups (p < 0.0001). However, mean improvement in headache scores was not statistically different between the investigational and control groups from 6 months through 60 months. For the two-level study, baseline mean headache scores significantly improved at 60 months for both the CDA and ACDF groups (p < 0.0001). The CDA group demonstrated greater improvement from baseline at all points; this difference was statistically significant at 6, 12, 24, 36, and 48 months but not at 18 and 60 months.Conclusion
Both CDA and ACDF at either one or two levels are associated with sustained headache relief from baseline. Patients undergoing two-level arthroplasty had significantly greater improvement in headache at all points except for at 18 and 60 months. This difference in improvement was not observed in patients undergoing single-level arthroplasty. The mechanism of greater headache relief after two-level arthroplasty remains unclear.