Changes in cervical spine curvature after uninstrumented one- and two-level corpectomy in patients with spondylotic myelopathy

OBJECTIVE: We studied changes in the cervical spine curvature in patients with cervical spondylotic myelopathy who underwent one- or two-level central corpectomy and iliac bone grafting without the use of instrumentation. METHODS: Curvature of the fused segment and of the whole cervical spine was evaluated on preoperative and follow-up x-rays in 93 patients (30 underwent one-level corpectomy, and 63 underwent two-level corpectomy). In 59 patients, the changes in the cervical spine curvature were studied using one follow-up x-ray; in the other 34 patients, the changes were studied on x-rays obtained at two or more follow-up visits. The sagittal alignment of the fused segment was categorized as lordotic (>+5 degrees), straight (+5 to -5 degrees) or kyphotic (>-5 degrees). The whole spine curvature also was recorded as lordotic, straight, or kyphotic. RESULTS: At a mean follow-up of 22.2 months (range, 6-71 mo), there was a mean change of -10.4 degrees in the segmental curvature (P < 0.001). The fused segment sagittal alignment also worsened (lordotic angles becoming straight or kyphotic and straight angles becoming kyphotic) in 44 patients (47%)(P < 0.001). However, serial studies in 34 patients (mean first and last follow-ups, 11.9 and 30.8 mo, respectively) did not demonstrate significant worsening of the kyphotic angle or the sagittal alignment over time (P = 0.9). Whole spine curvature worsened in 33 (35%) of the 93 patients (P < 0.001); serial studies did not reveal a significant change (P = 0.9). Patients improved in their functional status from a preoperative mean Nurick grade of 2.9 (range, 1-5) to a follow-up mean Nurick grade of 1.5 (range, 0-4) (P < 0.001). Patients with a kyphotic change in their whole spine curvature (n = 33) and those without such change (n = 60) had a similar functional outcome (mean change in Nurick grade, 1.5 and 1.4, respectively). CONCLUSION: Cervical spine curvature tended to undergo a kyphotic change at the fused segment in 47% of patients and a kyphotic change of the whole spine curvature in 35% of patients who underwent one- or two-level uninstrumented central corpectomy. This kyphotic change in the cervical spine, which stabilizes within 1 year after surgery, is not progressive, and it does not affect neurological outcome in these patients.