Objective: To evaluate the influence of the shell angle of cervical artificial disc on long-term effectiveness of cervical artificial disc replacement (CADR).
Methods: The clinical data of 71 patients who were treated with single-level CADR with Bryan prosthesis between December 2003 and December 2007 and followed up more than 10 years, were retrospectively analyzed. There were 44 males and 27 females with an age of 26-69 years (mean, 45.9 years). According to the shell angle of the cervical artificial disc which was measured on the postoperative lateral X-ray film, the patients were divided into kyphotic group (shell angle was negative) and non-kyphotic group. The following evaluation indexes before operation and at last follow-up were compared between 2 groups. Radiographic indexes included the range of motion (ROM) of cervical spine, the ROM of operated level, Cobb angle of operated level (the negative value indicated that the segmental kyphosis occurred at operated level), paravertebral ossification (PO) grades (grades 3 and 4 were high grade PO). Clinical indexes included Japanese Orthopaedic Association (JOA) score, neck disability index (NDI), and overall effectiveness evaluation (Odom criteria).
Results: There were 24 patients in kyphotic group and 47 patients in non-kyphotic group. There was no significant difference in baseline data including gender, age, and operated level between 2 groups ( P>0.05). All the patients in 2 groups were followed up 121-165 months (mean, 128 months). There was no significant difference in preoperative ROM of cervical spine and ROM of operated level between 2 groups ( P>0.05); but the preoperative Cobb angle of operated level in kyphosis group was significantly lower than that in non-kyphotic group ( t=2.636, P=0.013). There was no significant difference in ROM of cervical spine at last follow-up between 2 groups ( t=1.393, P=0.168), however, the ROM and the Cobb angle of operated level in kyphotic group were significantly lower than those in non-kyphotic group ( P<0.05). According to the Cobb angle of operated level at last follow-up, there were 9 patients (37.5%) with segmental kyphosis in kyphotic group and 7 patients (14.9%) in non-kyphotic group, showing significant difference ( χ2=4.651, P=0.031). There was a significant difference in PO grades between 2 groups ( Z=2.894, P=0.004) at last follow-up. In kyphotic group, there were 10 patients (41.7%) with low grade PO and 14 patients (58.3%) with high grade PO; and in non-kyphosis group, there were 36 patients (76.6%) with low grade PO and 11 patients (23.4%) with high grade PO. There was no significant difference in JOA scores and NDI before operation and at last follow-up, and the JOA improvement rate, NDI decline, and Odom criteria score at last follow-up between 2 groups ( P>0.05).
Conclusion: The shell angle of cervical artificial disc may lead to a decrease in the postoperative segmental ROM, and an increased occurrence of segmental kyphosis and high incidence of PO.
目的: 探讨人工颈椎间盘角对人工颈椎间盘置换术（cervical artificial disc replacement，CADR）后远期疗效的影响。.
方法: 回顾分析 2003 年 12 月—2007 年 12 月 71 例行单节段 Bryan 假体 CADR 且随访超过 10 年的患者临床资料，其中男 44 例，女 27 例；年龄 26～69 岁，平均 45.9 岁。根据术后出院前侧位 X 线片测量的人工颈椎间盘角结果将患者分为后凸组（人工颈椎间盘角为负值）和非后凸组，比较两组患者术前和末次随访时以下指标：影像学指标 ［颈椎整体活动度、手术节段活动度、手术节段 Cobb 角（负值表明手术节段存在局部后凸畸形）、椎旁骨化（paravertebral ossification，PO）分级（3、4 级为高等级）］；临床功能指标 ［日本骨科协会（JOA）评分、颈椎功能障碍指数（NDI）、整体疗效评估（Odom 评分）］。.
结果: 71 例患者分为后凸组 24 例、非后凸组 47 例，两组患者性别、年龄、手术节段等一般资料比较差异无统计学意义（ P>0.05），具有可比性。两组患者均获随访，随访时间 121～165 个月，平均 128 个月。术前两组患者颈椎整体活动度及手术节段活动度比较，差异均无统计学意义（ P>0.05）；后凸组手术节段 Cobb 角显著低于非后凸组（ t=2.636， P=0.013）。末次随访时，两组颈椎整体活动度比较差异无统计学意义（ t=1.393， P=0.168），但后凸组手术节段活动度和 Cobb 角均显著低于非后凸组（ P<0.05）。根据末次随访时的手术节段 Cobb 角，后凸组局部后凸畸形 9 例（37.5%），非后凸组 7 例（14.9%），比较差异有统计学意义（ χ2=4.651， P=0.031）。两组 PO 分级比较差异有统计学意义（ Z=2.894， P=0.004）；其中后凸组低等级 PO 10 例（41.7%）、高等级 PO 14 例（58.3%），非后凸组低等级 PO 36 例（76.6%）、高等级 PO 11 例（23.4%）。两组患者术前及末次随访时的 JOA 评分、NDI，以及末次随访时 JOA 改善率及 Odem 评分、手术前后 NDI 差值比较，差异均无统计学意义（ P>0.05）。.
结论: 人工颈椎间盘角后凸可能会导致 CADR 术后远期手术节段活动度降低，局部后凸和高等级 PO 的发生率增高。.
Keywords: Shell angle of cervical artificial disc; cervical artificial disc replacement; long-term effectiveness; paravertebral ossification; segmental kyphosis.