Weiser Lukas, Huber Gerd, Sellenschloh Kay, Viezens Lennart, Püschel Klaus, Morlock Michael M, Lehmann Wolfgang
Department of Trauma Surgery, Orthopaedic Surgery and Plastic Surgery, University Medical Center Göttingen, Robert-Koch-Str. 40, 37099, Göttingen, Germany.
Institute of Biomechanics, TUHH Hamburg University of Technology, Hamburg, Germany.
Eur Spine J. 2018 Aug;27(8):1964-1971. doi: 10.1007/s00586-018-5660-7. Epub 2018 Jun 9.
Cement augmentation of pedicle screws is known to increase their mechanical strength. Aim was to evaluate the impact of cement augmentation on pedicle screw fatigue strength in dependence of the bone mineral density (BMD).
Twenty-one human L2 vertebral bodies from donors between 19 and 96 years of age were used for in vitro experiments. BMD was measured using quantitative computed tomography (QCT). Two pedicle screws were inserted in each specimen and unilaterally augmented with bone cement. Fatigue testing was performed using a cranio-caudal sinusoidal, cyclic load (0.5 Hz) with increasing compression force (100 N + 0.1 N/cycles). Results were evaluated for the BMD groups: normal: BMD > 120 mg/cm, osteopenic: BMD 80-120 mg/cm, and osteoporotic: BMD < 80 mg/cm bone mass.
There was a significant correlation between fatigue force and BMD for the non-augmented and augmented screws (non-augmented R = 0.839, p < 0.001; augmented R = 0.551, p < 0.001). There was a significantly increased fatigue strength of the augmented screws over the non-augmented screws in the osteoporotic group (p = 0.001), while the differences in the other groups were not significant (normal p = 0.818/osteopenic p = 0.132).
The benefit of pedicle screw cement augmentation significantly depends on the bone mineral density and has the greatest extent of increased fatigue strength in osteoporotic vertebrae. Preoperative measurement of the BMD is strongly recommended to predict the benefit of augmentation and reinforce the decision for cement augmentation. These slides can be retrieved under Electronic Supplementary Material.
已知椎弓根螺钉骨水泥强化可增加其机械强度。本研究旨在评估骨水泥强化对椎弓根螺钉疲劳强度的影响，并分析其与骨密度（BMD）的关系。
使用21个来自19至96岁供体的人L2椎体进行体外实验。采用定量计算机断层扫描（QCT）测量骨密度。每个标本中植入两枚椎弓根螺钉，并对其中一侧进行骨水泥强化。使用颅尾方向的正弦循环载荷（0.5Hz），并逐渐增加压缩力（100N + 0.1N/循环）进行疲劳测试。根据骨密度分组评估结果：正常组：BMD＞120mg/cm；骨量减少组：BMD 80 - 120mg/cm；骨质疏松组：BMD＜80mg/cm骨量。
未强化和强化螺钉的疲劳力与骨密度之间存在显著相关性（未强化R = 0.839，p＜0.001；强化R = 0.551，p＜0.001）。骨质疏松组中，强化螺钉的疲劳强度显著高于未强化螺钉（p = 0.001），而其他组的差异不显著（正常组p = 0.818/骨量减少组p = 0.132）。
椎弓根螺钉骨水泥强化的益处显著取决于骨密度，在骨质疏松椎体中疲劳强度增加的程度最大。强烈建议术前测量骨密度，以预测强化的益处并加强骨水泥强化的决策。这些幻灯片可在电子补充材料中获取。
