OBJECTIVETo investigate the mid-term radiological outcome of sagittal alignment of overall cervical spine and the functional spinal unit after replacement surgery with Bryan cervical disc prosthesis.

METHODSEighteen patients with cervical disc disorder were performed cervical disc replacement with 20 Bryan discs from November 2005 to May 2010, including single-level 16 cases and bi-level 2 cases. The patient consisted of 13 males and 5 females with age ranging from 38 to 59 years (average, (47 ± 6) years). Fourteen cases with overall cervical lordotic alignment and segmental lordotic alignment per-operatively (group 1) and 4 others with segmental kyphotic alignment and overall cervical kyphotic alignment per-operatively (group 2). The overall sagittal alignment (C(2-7)) and segmental sagittal alignment were measured pre-operatively, post-operatively and at final follow-up to evaluate the outcome.

RESULTSAll cases obtained the follow-up with an average of (24 ± 5) months (range 12 to 53 months). To the mean overall cervical alignment, there were 9.9° ± 1.9° per-operatively, 12.8° ± 2.1° post-operatively and 11.6° ± 1.8° at final follow-up in group 1 and -1.8° ± 0.8° per-operatively, 7.3° ± 1.3° post-operatively and 5.0° ± 2.1° at final follow-up in group 2. There were statistical significance between per-operatively and post-operatively (t = -2.987 and -5.058, P < 0.05) and no statistical significance between post-operatively and final follow-up (P > 0.05) in both groups. To the mean segmental alignment there were 2.6° ± 0.8° per-operatively, 5.4° ± 1.0° post-operatively and 4.3° ± 0.9° at final follow-up in group 1 and -3.0° ± 0.8° per-operatively, 3.8° ± 1.3° post-operatively and 0.3° ± 2.8° at final follow-up in group 2. There were statistical significance between per-operatively and post-operatively in both groups (t = -3.829 and -4.086, P < 0.05) and between post-operatively and final follow-up in group 1 (t = 2.630, P < 0.05)but not in group 2 (P > 0.05).

CONCLUSIONSThe Bryan cervical disc prosthesis has a good mid-term outcome for maintaining sagittal alignment of overall cervical spine and the functional spinal unit. Long-term follow-up should be needed to assess the long-term functionality of the prosthesis.