Mahar Andrew T, Brown David S, Oka Richard S, Newton Peter O
Children's Hospital, San Diego, MC5054, 3020 Children's Way, San Diego, CA 92123, USA.
Spine J. 2006 Sep-Oct;6(5):572-6. doi: 10.1016/j.spinee.2006.02.004. Epub 2006 Jul 24.
Anterior instrumentation is often used for correction of thoracic scoliosis. Loss of spinal correction may occur after failure at the bone-implant interface, and forces on the bone-implant interface during scoliosis correction remain unclear.
Evaluate two different mechanisms of loading associated with anterior scoliosis correction.
In vitro biomechanics lab.
Polyurethane foam and human cadaveric thoracic vertebral bodies were instrumented with transvertebral body screws. Bone-implant interface failure loads were measured during constrained, fixed-angle screw translation, as well as unconstrained translation allowing coronal plane screw rotation. Vertebral body staples were randomly assigned to both conditions.
Data were consistent across foam and cadaveric specimens. Failures occurred at significantly lower loads during unconstrained translation (with rotation) compared with constrained translation. Staple usage significantly increased the load to failure in both testing modes. In cadaveric bone, the constrained plowing load to failure was 562N+110N versus 188N+20N in the unconstrained testing. With a staple, these values increased to 694N+53N and 530N+100N, respectively.
The 280% increase in cadaveric failure loads when a staple was added in the unconstrained testing method exceeds previous reports. The unconstrained method of plow simulated anterior scoliosis instrumentation when a rod was cantilevered and compressed into position. Supplemental vertebral body staples may be clinically indicated, particularly at the ends of the construct where residual deforming forces remain the greatest.
前路器械常用于矫正胸椎侧弯。骨-植入物界面失效后可能会出现脊柱矫正丢失，而侧弯矫正过程中骨-植入物界面上的力仍不清楚。
评估与前路侧弯矫正相关的两种不同加载机制。
体外生物力学实验室。
用经椎体螺钉固定聚氨酯泡沫和人体尸体胸椎椎体。在受限的、固定角度的螺钉平移过程中，以及允许冠状面螺钉旋转的非受限平移过程中，测量骨-植入物界面失效载荷。椎体钉随机分配到两种情况。
泡沫和尸体标本的数据一致。与受限平移相比，非受限平移（带旋转）过程中失效时的载荷明显更低。在两种测试模式下，使用椎体钉均显著增加了失效载荷。在尸体骨中，受限犁削失效载荷为562N + 110N，而非受限测试中为188N + 20N。使用椎体钉时，这些值分别增加到694N + 53N和530N + 100N。
在非受限测试方法中添加椎体钉时，尸体失效载荷增加280%，超过了先前的报告。当棒被悬臂式放置并压缩到位时，非受限犁削方法模拟了前路侧弯器械。补充椎体钉在临床上可能是必要的，特别是在结构末端，那里残余变形力仍然最大。
