生物力学评价颈椎前路椎弓根螺钉植入骨质疏松椎骨内的稳定性

Biomechanical evaluation on the stability of anterior cervical pedicle screw fixation for osteoporosis

背景:前路颈椎间盘切除植骨融合是治疗颈椎病的有效术式,该术式能够提供坚强固定且植骨融合率相对较高。但是,对于2个节段以上同时受累的颈椎,由于植骨跨度较大,内固定和植骨块稳定性较差,容易产生植骨融合失败、假关节形成等并发症,影响疗效。目的:观察颈椎前路椎弓根螺钉植入骨质疏松椎骨内的生物力学稳定性。方法:纳入12具人颈椎骨,包括6具骨密度正常颈椎骨和6具骨质疏松颈椎骨,共60个椎骨标本资料进行分析,将30个骨质疏松椎骨标本植入颈椎前路椎弓根螺钉设为颈椎前路椎弓根螺钉组,将30个骨密度正常椎骨标本植入前路椎体螺钉设为前路椎体螺钉组。从上述两组中根据骨密度值抽取40个椎骨,分别设置为即时正常骨密度组、即时骨密度疏松组、疲劳正常骨密度组以及疲劳骨质疏松组,每组10个椎骨。采用双能X射线骨密度仪测定各椎体骨密度值,采用Electro Force 3510材料试验机对两种螺钉进行生物力学指标测试。结果与结论:颈椎前路椎弓根螺钉组骨矿盐含量、椎体螺钉拔出力、椎体螺钉拔出刚度、椎弓根螺钉拔出力、椎弓根螺钉拔出刚度均显著高于前路椎体螺钉组(P<0.05)。颈椎前路椎弓根螺钉即时正常骨密度标本最大轴向拔出力、即时骨质疏松标本最大轴向拔出力、疲劳正常骨密度标本最大轴向拔出力、疲劳骨质疏松标本最大轴向拔出力均显著高于高于前路椎体螺钉(P<0.05)。结果证实,与颈椎前路椎体螺钉相比,颈椎前路椎弓根螺钉在骨质疏松椎骨内生物力学性能更加稳定。

BACKGROUND：Anterior cervical discectomy and bone graft fusion are effective method to treat cervical spondylosis. This method can provide firm fixation and the fusion rate is high. However, for cervical vertebra involved in more than two segments, the stability of fixator and bone graft is poor due to big bone graft span, which may easily cause fusion failure and pseudarthrosis, and impact curative effects. OBJECTIVE：To investigate biomechanical stability of anterior cervical pedicle screw implantation for osteoporosis in the vertebra. METHODS：A total of 12 human cervical vertebrae were col ected, including 6 vertebrae with normal bone density and 6 vertebrae with osteoporosis. Data of 60 vertebra specimens were analyzed. 30 osteoporotic specimens＆amp;nbsp;implanted in anterior cervical pedicle screw were set as anterior cervical pedicle screw group. 30 normal specimens implanted in anterior cervical pedicle screw were set as anterior vertebral screw group. According to bone density, 40 vertebrae were col ected in above two groups, and were considered as normal bone mineral density group, instant osteoporosis group, fatigue normal bone mineral density group, and fatigue osteoporosis group （n=10）. Bone mineral density of each vertebra was detected using dual-energy X-ray absorptiometry. Biomechanical index of two kinds of screws was detected using ElectroForce 3510 material testing machine. RESULTS AND CONCLUSION：Bone mineral content, vertebral screw pul-out strength, vertebral screw pul-out stiffness, pedicle screw pul-out strength, and pedicle screw pul-out stiffness were significantly higher in the anterior cervical pedicle screw group than in the anterior vertebral screw group （P〈0.05）. The maximum axial pul-out strength of normal bone mineral density group, instant osteoporosis group, fatigue normal bone mineral density group, and fatigue osteoporosis group was significantly higher than in the anterior vertebral screw group （P〈0.05）. The results confirmed that osteoporotic vertebral biomechanical performance is more stable in anterior pedicle screws compared with the anterior vertebral screw.