Long-term, radiographic, longitudinal follow-up after treatment of cervical disc disease with the Bryan Cervical Disc Prosthesis

INTRODUCTION: The purpose of this longitudinal study is to assess the change in motion at the index level and in motion and disc degeneration at the adjacent levels after surgery for cervical disc disease with a Bryan Cervical Disc Prosthesis. METHODS: Patients were included if their preoperative range of motion (ROM) at the index level was >2°. Intervertebral disc degeneration was assessed using a scoring system ranging from 0 (no degeneration) to 9 (severe degeneration). Based on lateral radiographs, ROM was calculated using a custom motion analysis tool (measurement error: 0.3°). RESULTS: In total, 63 patients met the inclusion criterion. In April 2008, 61 patients had 4 years radiographic follow-up, 42 had 6 years, and 9 had 8 years follow-up. On average, preoperative ROM was 8.8+/-5.7° at index level, and 11.1+/-5.0° and 9.4+/-5.5° at the cranial and caudal adjacent levels. At index level, ROM increased 28% 6 months after surgery, but decreased again and stabilized around the preoperative value at 4 year (+6%), 6 year (+6%) and 8 year follow-up (-13%). At the adjacent levels, a similar trend was observed: ROM increased 22% (cranial) and 27% (caudal) 6 months after surgery, but stabilized at 4 year (cranial +14%; caudal +13%), 6 year (cranial -7%; caudal +26%) and 8 year follow-up (cranial -20%; caudal +17%). On average, the preoperative degeneration score was 2.4+/-2.0 at the index level, 1.1+/-1.5 at the cranial and 0.8+/-1.4 at the caudal adjacent level. At the cranial and caudal adjacent levels the degeneration score increased at 4 year (1.6+/-1.8 and 1.4+/-1.8) and at 6 year follow-up (1.9+/-1.9 and 1.8+/-2.0). At 8 years follow-up the degeneration scores were 2.3+/-2.5 for the cranial and 0.8+/-1.1 for the caudal adjacent level. There was a significant correlation between preoperative and postoperative degeneration for both adjacent levels (r>0.76). CONCLUSIONS: ROM at the index level is maintained up to 8 years after surgery. Moreover, the insertion of the prosthesis did not lead to an abnormal increase in ROM of the adjacent levels. The Bryan Cervical Disc Prosthesis seems to protect against acceleration of adjacent level degeneration as seen after interbody fusion.Walraevens J., Vander Sloten J., Demaerel P., Suetens P., van Loon J., Van Calenbergh F., Goffin J., ''Long-term, radiographic, longitudinal follow-up after treatment of cervical disc disease with the Bryan Cervical Disc Prosthesis'', 25th annual meeting of the European section of the Cervical Spine Research Society (CSRS-E), June 11-13, 2009, Uppsala, Sweden.status: publishe