骨质疏松对椎弓根螺钉稳定性影响的实验研究

Experimental study of the effect of osteoporosis severity on pedicle screw fixation

目的评价不同骨质疏松程度条件下,椎弓螺钉的稳定性,为椎弓根内固定在合并有骨质疏松症的患者中的选用提供力学理论基础。方法采用新鲜尸体脊柱标本,根据骨密度检测结果,按临床诊断标准分成骨质正常、骨量减少、骨质疏松和重度骨质疏松四个水平。然后,每个骨密度水平,植入普通椎弓根螺钉24枚,进行螺钉轴向拔出实验,测定最大拔出力、刚度和能量吸收值三项指标,对所测指标进行骨密度水平间的对比分析。结果骨密度水平从正常下降到重度疏松程度,最大拔出力、刚度均随之下降,组间比较均存在显著性差异(P<0.05)。正常骨密度水平的能量吸收值显著高于骨质疏松、重度疏松(P<0.05),但与骨量减少水平相比并无统计学差异(P>0.05)。另外,骨量减少水平的能量吸收值显著性高于重度骨质疏松水平(P<0.05),但与骨质疏松水平相比较无显著性差异(P>0.05)。结论反映椎体骨质质量的骨密度是决定椎弓根螺钉稳定性的重要因素。

Objective To evaluate the stability of pedicle screw fixation in patients with varied level of osteoporosis, and to provide theoretical evidence for clinical application of pedicle screw in patients with osteoporasis. Methods Fresh cadaver spines were stratified into four levels： normal, osteopenia, osteoporosis and severe osteoporosis, according to the value of bone mineral density （BMD）. The vertebrae were bilaterally instrumented pedicle screws, resulting in 24 screws per BMD level. Screw pullout tests were conducted. On the load-stroke curve, the maximum pullout strength, stiffness, and energy absorption were tested. The differences among all BMD levels were compared. Results The maximum pullout strength and stiffness of pedicle screw decreased along with the decline of BMD from normal to severe osteoporosis levels, and significant differences were found between any two groups （P 〈 0. 05）. The absorbed energy of normal level group was significantly higher than that of osteoporosis level or severe osteoporosis level （ P 〈 0, 05 ） , but there was no statistical difference compared with that of osteopenia level （ P 〉 0.05 ）. Additionally, the absorbed energy of osteopenia level was significantly higher than that of severe osteoporosis （ P 〈 0.05 ） , but there was no significant difference compared with that of osteoporosis level （P 〉 0.05）. Conclusion BMD, which can reflect the bone quality of vertebrae, is an important factor that can predict the fixation strength of pedicle screw.