Clinical Analysis Of Heterotopic Ossification After Single-segment Bryan Artificial Cervical Disc Replacement

BACKGROUND: Cervical spondylosis is a common disease in orthopaedics clinic.Since the 1950 s, the anterior cervical discectomy and fusion has been recognised,becoming the "gold standard" of operative treatmen[1-3]t. Discectomy and interbody fusion is a classical surgical procedure for the treatment of cervical spondylosis. The discectomy is the key to decompress the spinal cord and nerve root compression. The interbody fusion is to fill the gap left by the discectomy and it is to exchange cervical vertebra motion segment for cervical stability. Anterior cervical discectomy and fusion(ACDF) is a common operation method in the treatment of cervical spondylosis. However, there are many complications after rigid fixation and spinal fusion, such as secondary adjacent segment degeneration, leading to recurrence of symptoms even the second operation. With the innovation of technology, artificial cervical disc replacement(ACDR) comes into being. Goffin reported that Bryan artificial cervical disc replacement applied to the treatment of cervical spondylosis for the first time. Since then, it has been applied widely on clinic for it can effectively prevent adjacent segment degeneration while it can decompress compression[4-8].Bryan artificial cervical disc replacement can keep the height and activity of replacement segment and the adjacent segment and decompress compression, reduce the stress of adjacent intervertebral disc, maintain the normal spinal sequence, reduce the incidence of adjacent vertebral disease. But with the development of technology,postoperative complications, such as prosthesis subsidence, loosening or dislocation,attract people’s attention, and heterotopic ossification becomes the focus of attention.If heterotopic ossification even interbody fusion occurs after artificial cervical disc replacement, range of motion cervical spine weakens or loses, and adjacent segment degeneration is inevitable.OBJECTIVE: To investigate and research the formative factors of heterotopic ossification after single-segment Bryan artificial cervical disc replacement and analyze them.METHODS:52 patients with single-segment Bryan artificial cervical disc replacement in our department from January, 2007 to December, 2010 were analyzed,and they all were in accordance with the inclusive criteria. There were 30 men and 22 women at the age of 30-64 and with the average age of 48.38. 32 patients suffered from nerve-root type cervical spondylosis; 10 patients suffered from cervical spondylotic myelopathy and 10 suffered from mixed cervical spondylosis. X-ray images of anteroposterior, lateral, flexion and extension cervical vertebra of two weeks, 1 month, 2 months, 3 months, 6 months, 1 year and 2 years after surgery were analyzed. Mc Afee stage method was used to evaluate whether heterotopic ossification occurred. Flexion-extension X-ray images were used to measure the range of motion(ROM) of replacement segment, and neck disability index(NDI) and they were compared with preoperative X-ray images. At the same time, ages, gender,, amount of bleeding and relevant factors were analyzed.RESULTS: 52 cases were followed up. The follow-up time ranged from 2 weeks to 2years, and the average time was 10.5 months. Follow-up time was longer than 3months with the longest of 21 months. 8 patients had heterotopic ossification, and the incidence was 15.38%. It was found that gender, operation time had no obvious influences on heterotopic ossification; aged patients and patients with high amount of bleeding tended to develop heterotopic ossification. Heterotopic ossification had no obvious influences on range of motion and neck disability index.CONCLUSION: The results indicate that occurrence rate of heterotopic ossification after single-segment Bryan artificial cervical disc replacement is low in the near future, and the occurrence rate is related to amount of bleeding. The range of motion and neck disability index of lesion segment of patients with heterotopic ossification have no statistical difference compared with preoperative range of motion and neck disability index. Heterotopic ossification has no obvious effect on postoperative effect. Artificial cervical disc replacement is an effective method for treatment of degenerative cervical disease. But large, long-term clinical verifications are required to evaluate long-term effects.