Dalal Aliasgar, Upasani Vidyadhar V, Bastrom Tracey P, Yaszay Burt, Shah Suken A, Shufflebarger Harry L, Newton Peter O
Department of Orthopaedic Surgery, University of Illinois, Chicago, IL, USA.
J Spinal Disord Tech. 2011 Jun;24(4):251-7. doi: 10.1097/BSD.0b013e3181edebc4.
Retrospective radiographic outcome analysis.
To compare residual postoperative apical vertebral rotation between uniplanar versus polyaxial bilateral pedicle screw constructs in thoracic adolescent idiopathic scoliosis (AIS).
Vertebral rotation is a component of the 3-dimensional deformity of AIS. The correction of vertebral rotation is an important goal of surgery. A comparison of uniplanar versus polyaxial screws has yet to be studied.
A review of a multicenter database of Lenke type 1 to 3 AIS patients who underwent surgical correction of thoracic AIS by posterior segmental pedicle screw instrumentation and fusion with either uniplanar or polyaxial pedicle screws and 5.5-mm steel rod constructs was performed. Curves greater than 100 degrees were excluded to control for the propensity to use polyaxial screws to correct larger curves. Postoperative apical vertebral rotation of thoracic curves was graded as 0, 1, or 2 based on a computed tomography scan-validated radiographic method that uses the relative position of the screw tips to grade apical vertebral rotation at the 6-week and 1-year postoperative visits. By this grading method, higher grades correspond to greater residual apical vertebral rotation.
Two hundred and ten patients met the inclusion criteria. The uniplanar screw group included 95 patients whereas the polyaxial screw group had 115 patients. The respective mean preoperative thoracic Cobb angle of 58±12 and 60±13 degrees (P=0.1), first erect postoperative coronal correction of 72% and 74% (P=0.38), and 1-year correction of 70% and 76% (P=0.07) were not significantly different between the uniplanar and polyaxial groups. At 6 weeks postoperation, the uniplanar group had 34% of patients with grade 0 rotation, 52% with grade 1, and only 14% with grade 2 thoracic apical vertebral rotation. In the polyaxial group, only 14% of patients were grade 0, 35% were grade 1, and 51% were the most rotated grade 2. This was a significant difference in the distribution of the axial rotation grades (P<0.001), with less residual apical vertebral rotation with the use of uniplanar screws. The same pattern of results was found at 1-year postoperative evaluation (P<0.001).
There was little difference in the coronal plane correction of thoracic curves between the 2 types of screws. However, the uniplanar pedicle screw group had a larger proportion of patients with greater thoracic apical vertebral derotation (less residual apical vertebral rotation) compared with the polyaxial screw group. This can be attributed to the increase in rotational leverage afforded by uniplanar screws during intraoperative bilateral direct apical vertebral derotation maneuvers.
回顾性影像学结果分析。
比较青少年特发性脊柱侧凸（AIS）患者行单平面与多轴双侧椎弓根螺钉内固定术后椎体顶椎残留旋转情况。
椎体旋转是AIS三维畸形的一个组成部分。矫正椎体旋转是手术的一个重要目标。单平面螺钉与多轴螺钉的比较尚未得到研究。
回顾一个多中心数据库，该数据库纳入了Lenke 1至3型AIS患者，这些患者接受了后路节段性椎弓根螺钉内固定及融合术，使用的是单平面或多轴椎弓根螺钉及5.5毫米钢棒内固定。排除曲线大于100度的病例，以控制使用多轴螺钉矫正更大曲线的倾向。根据一种计算机断层扫描验证的影像学方法，将胸段曲线术后顶椎旋转分为0、1或2级，该方法利用螺钉尖端的相对位置在术后6周和1年随访时对顶椎旋转进行分级。通过这种分级方法，分级越高，顶椎残留旋转越大。
210例患者符合纳入标准。单平面螺钉组95例，多轴螺钉组115例。单平面组与多轴组术前胸段Cobb角分别为58±12度和60±13度（P = 0.1），术后首次直立位冠状面矫正分别为72%和74%（P = 0.38），1年矫正分别为70%和76%（P = 0.07），差异均无统计学意义。术后6周，单平面组0级旋转患者占34%，1级占52%，2级胸段顶椎旋转仅占14%。多轴组中，0级患者仅占14%，1级占35%，2级（旋转最严重）占51%。轴向旋转分级分布存在显著差异（P<0.001），使用单平面螺钉时顶椎残留旋转较少。术后1年评估也发现了相同的结果模式（P<0.001）。
两种类型的螺钉在胸段曲线冠状面矫正方面差异不大。然而，与多轴螺钉组相比，单平面椎弓根螺钉组中胸段顶椎去旋转程度更大（顶椎残留旋转更少）的患者比例更高。这可归因于单平面螺钉在术中双侧直接顶椎去旋转操作过程中提供的旋转杠杆作用增加。
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