[Mid-term effectiveness of anterior decompression and fusion with nano-hydroxyapatite/polyamide 66 cage in treatment of cervical spondylotic myelopathy].

OBJECTIVE: To assess the mid-term effectiveness of anterior decompression and fusion with nanohydroxyapatite/polyamide 66 (n-HA/PA66) cage in treatment of cervical spondylotic myelopathy.

METHODS: A retrospective study was made on 48 patients with cervical spondylotic myelopathy who underwent anterior decompression and fusion with n-HA/PA66 cage between August 2008 and January 2010. There were 33 males and 15 females with an average age of 54.5 years (range, 42-72 years). The disease duration was 3-12 months (mean, 6 months). The affected segments included 35 cases of single segment (C3, 4 in 7, C4, 5 in 18, and C5, 6 in 10) and 13 cases of double segments (C3-5 in 7 and C46 in 6). Of 48 patients, 28 was diagnosed as having intervertebral disc protrusion, 12 as having ossification of posterior longitudinal ligament, and 8 as having vertebral osteophyte; 35 patients underwent single segmental anterior corpectomy and fusion, and 13 patients underwent single segmental anterior discectomy and fusion. The pre- and post-operative radiographs (cervical anteroposterior and lateral X-ray films and three-dimensional CT scans) were taken to measure the segmental height and lordosis angle. Brantigan et al assessment standard and visual analogue scale (VAS) and Japanese Orthopaedic Association (JOA) scores were used to evaluate the graft fusion and the improvement of clinical symptoms, respectively.

RESULTS: All patients were followed up for 46 months on average (range, 36-54 months). No cage breaking, displacement, or sliding was found. At last follow-up, 36 cases were rated as Brantigan grade E, 10 cases as grade D, and 2 cases as grade C; the fusion rate was 96%. Both segmental height and lordosis angle were corrected significantly at immediate and 6 months after operation and last follow-up than those before operation (P < 0.05), but no significant difference was found among different time points after operation (P > 0.05). At last follow-up, the cage subsidence was (1.3 +/- 1.0) mm. The VAS and JOA scores at 6 months after operation and last follow-up were significantly improved when compared with preoperative scores (P < 0.05), and the scores at last follow-up were superior to ones at 6 months after operation (P < 0.05).

CONCLUSION: The mid-term effectiveness of anterior decompression and fusion with the n-HA/PA66 cage in patients with cervical spondylotic myelopathy is satisfactory because it can effectively restore and maintain segmental height and lordosis angle and promote osseous fusion.