Lehman Ronald A, Polly David W, Kuklo Timothy R, Cunningham Bryan, Kirk Kevin L, Belmont Philip J
Department of Orthopaedic Surgery and Rehabilitation, Walter Reed Army Medical Center, Washington, DC, USA.
Spine (Phila Pa 1976). 2003 Sep 15;28(18):2058-65. doi: 10.1097/01.BRS.0000087743.57439.4F.
A biomechanical study on cadaveric thoracic vertebrae using pullout strength, insertional torque, and bone mineral density to determine the optimal sagittal trajectory of thoracic pedicle screws.
To perform a biomechanical study on cadaveric thoracic vertebrae using insertional torque, pullout strength, and bone mineral density to determine the optimal biomechanical sagittal trajectory for placement thoracic pedicle screws. We compared the straight-forward (paralleling the vertebral endplate) with anatomic trajectory (directed along the true anatomic axis of the pedicle).
Thirty cadaveric thoracic vertebrae were harvested and evaluated with dual-energy x-ray absorptiometry to assess bone mineral density. Matched, fixed-head pedicle screws were then randomly assigned by side and placed using the straight-forward or anatomic technique under fluoroscopic visualization while recording the maximum insertional torque. Pullout strength testing was then performed.
The maximum insertional torque for the straight-forward technique was 2.58 +/- 0.14 (SE) in pounds, whereas the anatomic technique averaged 1.86 +/- 0.14 (SE) in pounds (P = 0.0005). The maximum insertional torque at the neurocentral junction for the straight-forward technique averaged 1.89 +/- 0.17 (SE) in-lbs. (73% of maximum insertional torque), whereas the anatomic trajectory averaged 1.39 +/- 0.11 (SE) in pounds (75% of maximum insertional torque) (P = 0.007). The average pullout strength using a straight-forward trajectory was 611 +/- 50 (SE) N compared to the anatomic trajectory, which averaged 481 +/- 54 (SE) N (P = 0.034). The pullout strength correlated with mean bone mineral density for both the straight-forward (r = 0.461, P = 0.027) and anatomic (r = 0.598, P = 0.004) techniques.
The straight-forward technique results in a 39% increase in maximum insertional torque and a 27% increase in pullout strength compared to the anatomic technique. The maximum insertional torque at the neurocentral junction resulted in a 36% increase using the straight-forward technique versus the anatomic trajectory. Bone mineral density directly correlates with pullout strength for both techniques.
一项关于尸体胸椎的生物力学研究，采用拔出强度、插入扭矩和骨密度来确定胸椎椎弓根螺钉的最佳矢状轨迹。
利用插入扭矩、拔出强度和骨密度对尸体胸椎进行生物力学研究，以确定胸椎椎弓根螺钉置入的最佳生物力学矢状轨迹。我们将直接（平行于椎体终板）与解剖轨迹（沿椎弓根的真正解剖轴方向）进行了比较。
采集30个尸体胸椎，用双能X线吸收法评估骨密度。然后将匹配的、固定头部的椎弓根螺钉按侧别随机分配，并在透视下使用直接或解剖技术置入，同时记录最大插入扭矩。随后进行拔出强度测试。
直接技术的最大插入扭矩为2.58±0.14（标准误）磅，而解剖技术平均为1.86±0.14（标准误）磅（P = 0.0005）。直接技术在神经中央交界处的最大插入扭矩平均为1.89±0.17（标准误）英寸-磅（最大插入扭矩的73%），而解剖轨迹平均为1.39±0.11（标准误）磅（最大插入扭矩的75%）（P = 0.007）。与解剖轨迹相比，采用直接轨迹的平均拔出强度为611±50（标准误）N，解剖轨迹平均为481±54（标准误）N（P = 0.034）。直接技术和解剖技术的拔出强度均与平均骨密度相关（直接技术：r = 0.461，P = 0.027；解剖技术：r = 0.598，P = 0.004）。
与解剖技术相比，直接技术导致最大插入扭矩增加39%，拔出强度增加27%。与解剖轨迹相比，采用直接技术在神经中央交界处的最大插入扭矩增加了36%。两种技术的骨密度均与拔出强度直接相关。
