[The mid-term effects of Bryan cervical disc prosthesis on sagittal alignment of overall cervical spine and the functional spinal unit].

ABSTRACT

OBJECTIVE: To 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. METHODS: Eighteen 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. RESULTS: All 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). CONCLUSIONS: The 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.