Tao Fenghua, Zhao Yingchuan, Wu Yungang, Xie Yang, Li Ming, Lu Yanghu, Pan Feng, Guo Fengjin, Li Feng
Department of Orthopedic Surgery, Renmin Hospital of Wuhan University, Wuhan, PR China.
J Spinal Disord Tech. 2010 Dec;23(8):e75-80. doi: 10.1097/BSD.0b013e3181d38f63.
Retrospective.
To compare the occurrence of the crankshaft phenomenon in patients with adolescent idiopathic scoliosis (AIS) who underwent hybrid, consecutive pedicle screw or interval pedicle screw instrumentation for posterior spinal fusion.
Scoliosis may progress after posterior spinal fusion in skeletally immature patients with AIS. The crankshaft phenomenon occurs when the anterior column continues to grow in the face of posterior fusion causing characteristic twisting of the fused segment. The optimal surgical method for preventing the occurrence of this complication has not been determined.
Sixty seven patients with AIS who underwent posterior fusion over a 6-year period were divided into groups according to fixation method: hybrid instrumentation, interval pedicle screw placement, or consecutive pedicle screw placement. Preoperative, postoperative, and follow-up radiographic measures, including Cobb angle, apical vertebral rotation (AVR), apical vertebral transposition (AVT), rib vertebral angle difference (RVAD) and trunk shift (TS) were assessed. The occurrence of the crankshaft phenomenon was determined.
The mean follow-up duration was 36 months. There were no between-the-group differences in demographics or preoperative or immediate postoperative measures. At the last follow-up, significant differences among the groups were apparent for Cobb angle, AVR, AVT, RVAD, and TS (all P<0.05). Cobb angle, AVR, AVT, RVAD, and TS significantly increased between the postsurgery and the last follow-up in the hybrid instrumentation group (all P<0.0167). Only TS increased significantly in the 2 other groups. There were 7 cases of crankshaft phenomenon occurrence in the hybrid instrumentation group (33%), but none in the other 2 groups.
These findings suggest that in skeletally immature patients with AIS, hybrid instrumentation cannot effectively prevent occurrence of the crankshaft phenomenon, whereas interval and consecutive pedicle screw instrumentation may be more (and equally) efficacious in this regard.
回顾性研究。
比较接受混合式、连续椎弓根螺钉或间隔椎弓根螺钉器械辅助后路脊柱融合术的青少年特发性脊柱侧凸（AIS）患者中曲轴现象的发生率。
在骨骼未成熟的AIS患者中，后路脊柱融合术后脊柱侧凸可能进展。当后路融合时前柱继续生长导致融合节段出现特征性扭转时，就会发生曲轴现象。预防这种并发症发生的最佳手术方法尚未确定。
将6年间接受后路融合术的67例AIS患者根据固定方法分为几组：混合式器械辅助、间隔椎弓根螺钉置入或连续椎弓根螺钉置入。评估术前、术后及随访时的影像学指标，包括Cobb角、顶椎旋转（AVR）、顶椎移位（AVT）、肋椎角差（RVAD）和躯干偏移（TS）。确定曲轴现象的发生情况。
平均随访时间为36个月。各组在人口统计学特征、术前或术后即刻指标方面无差异。在末次随访时，各组在Cobb角、AVR、AVT、RVAD和TS方面存在显著差异（均P<0.05）。混合式器械辅助组在术后至末次随访期间，Cobb角、AVR、AVT、RVAD和TS均显著增加（均P<0.0167）。其他两组仅TS显著增加。混合式器械辅助组有７例发生曲轴现象（33%），其他两组无1例发生。
这些研究结果表明,在骨骼未成熟的AIS患者中，混合式器械辅助不能有效预防曲轴现象的发生，而间隔和连续椎弓根螺钉器械辅助在这方面可能更有效（且效果相同）。
