Ball tip技术置入中上胸椎椎弓根螺钉的准确性评价

 【目的】通过与徒手置钉术的比较来评价一种新的椎弓根置钉技术——Ball tip技术置入中上胸椎椎弓根钉的准确性。【方法】自2009年3月至2011年5月，对40例需行中上胸椎椎弓根钉内固定的患者，术中应用ball tip技术或徒手置钉技术置入椎弓根钉。椎弓根球形探针包括一个金属球端和一个具有良好弹性的金属柄，金属球端的直径分别有1.5、2.5、3.5mm三种。Ball tip技术要点：按标准椎弓根钉进钉点定位，高速磨钻钻孔去除皮质，将椎弓根球形探针按直径从小到大依次缓慢敲入椎弓根内直至达到椎体前方骨皮质。术后采用CT扫描评价椎弓根钉钉道情况。同样方法评价同期徒手置钉组。【结果】采用Ball tip技术共置入104枚椎弓根钉，传统徒手技术置入98枚。术后CT扫描显示Ball tip组胸椎椎弓根钉钉道准确率为84.6%，16枚（15.4%）螺钉出现置钉不良，其中3枚（2.9%）穿透椎弓根内侧骨皮质；6枚（5.8%）穿透椎弓根外侧骨皮质；7枚（6.7%）穿透椎体前壁骨皮质。徒手置钉组准确率为65.3%，共有34枚（34.7%）置钉不良螺钉，其中10枚（10.2%）穿透椎弓根内侧骨皮质；16枚（16.3%）穿透椎弓根外侧骨皮质；8枚（8.2%）穿透椎体前壁骨皮质。两组置钉准确率的差异具有统计学意义（P<0.01），两组螺钉穿透椎弓根内侧、外侧骨皮质的差异具有统计学意义（P<0.05）。所有患者术中和术后均未出现神经、 血管和内脏损伤等并发症。【结论】与徒手置钉技术相比，Ball tip置钉技术，可更准确地置入中上胸椎椎弓根钉，减少因螺钉误置所导致的术后并发症。

Accuracy of Ball Tip Technique for Pedicle Screw Placement in the Upper and Middle Thoracic Spine

【Objective】 The aim in this study was to evaluate the accuracy of the ball tip technique in placing pedicle screws in the upper and middle thoracic spine,as compared with the conventional freehand technique.【Methods】 From March 2009 to May 2011,40 patients with instability or deformity of upper or middle thoracic spine underwent posterior surgery with pedicle screw placement via the ball tip or conventional free-hand technique.The ball tip probe consists of a metal flexible shaft with a ball-shaped metal tip which size includes 1.5,2.5,and 3.5 mm in diameter.Ball tip technique: A high speed bur is used to remove cortical bone and create a starting point,and then the ball tip probes is tapped gently by a hammer for making a guide hole through the pedicle into the vertebral body.The accuracy of the pedicle screw placements was evaluated on postoperative axial CT scanning.The same evaluation was applied for conventional free-hand technique group.【Results】 104 screws were evaluated in the ball tip group and 98 in the conventional free-hand group.88 screws(84.6%) were recognized as intrapedicular position in the ball tip group and 64(65.3%) in the conventional group.A significant difference in the accuracy of pedicle screw placement was observed between the 2 groups(P < 0.01).In the ball tip group,3 screws(2.9%) were classified as breaches of inner cortex of pedicle;6(5.8%) as breaches of outer cortex of pedicle;7(6.7%)as breaches of anterior cortex of vertebrae.In the conventional group,10 screws(10.2%) were classified as breaches of inner cortex of pedicle;16(16.3%) as breaches of outer cortex of pedicle;8(8.2%) as breaches of anterior cortex of vertebrae.A significant difference in the percentage of pedicle screws classified as pedicle breaches was determined between the 2 groups(P < 0.05).No vascular,pulmonary,or neurological injuries caused by thoracic pedicle screws placement occurred in either group.【Conclusion】 The ball tip technique enhanced the accuracy of pedicle screw placement in the upper and middle thoracic spine as compared with the free-hand technique.This technique can probably reduce the risk of complications from screw misplacements.