椎弓根螺钉应用于骨质疏松椎体的生物力学研究

本文采用7具老年腰椎标本,共35个椎体,DEXA测试其BMD,随机分为5组,应用生物力学测试方法,研究下列补救措施对螺钉牢固性的影响:①按放横向连接装置;②钉道内填充骨水泥;③钉道内填充骨屑;④更换直径较大的螺钉;⑤单纯安置Dick螺钉。所有标本平均BMD为0.695±0.14g/cm_2。⑤组单纯安置Dick钉的最大拔出力232±92.4N,①～④组最大拔出力与⑤组比较,分别增加了93％（P<0.01）、94％（P<0.01）、139％（P<0.01）、33％（P>0.05）。研究表明,横向装置、骨水泥、骨屑可提高螺钉的牢固性,直径较大的螺钉并不能提高其在骨质疏松椎体内的稳定性,重度骨质疏松可能是手术禁忌症。

A BIOMECHANICAL STUDY ON PEDICLE SCREW FIXATION IN OSTEOPROTIC LUMBER SPINE

Pedicle screw fixation in osteoprotic bone is known to be poor. This study was designed to compare four methods which can improve the screw fixation stiffness. Seven cadaveric lumbar spines with osteoprosis were obtained and BMD was evaluated using a DEXA.A11 spines were separated into 35 vertebraes, and then divided into five groups randomly. The screw were inserted using one of the five methods: (1)two screw in the same vertbrae were linked with transverse plate; (2)with bone cement into screw hole; (3)with bone pieces picked into screw hole;(4)be instead by using a larger diameter screw; and (5)with simple Dick screw fixation as control. Axial pull-out force and screw displacement were measured. The results showed that: the pull-out force was increased (compared with group 5) 93% (P<0.01) in groupl, about onefold (P<0.01) in group 2, 139% (P<0.01) in group3 and 33% (P>0.05) in group 4. It is concluded that: transverse plate, bone cement, bone pieces can improve the stability of screw. But when the vertbrae with serious osteoprosis, these methods are no clinical value. There is no significant ents with serious osteoprosis.