The Design And Biomechanical Testing Of A New Vertebral Expander

ObjectiveTo develop a new Thoracolumbar vertebral body expander, clarifying its compositionand structure, the principle features. To compare two kyphoplasty techniques in cadavericfractured vertebrae: an experimental vertebral expander system and balloon kyphoplasty.Investigate its clinical feasibility by testing the biomechanical stability.Methods1．Design the new vertebral expander system：Measure twenty normal persons’ T11～L5vertebral segment pedicle transversediameter, sagittal diameter and length of the pedicle channel （from pedicle edge cortexcenter to vertebral bottom margin midpoint）,and test the height of vertebral body. Basingon lumbar imaging data, we put forward design ideas, and draw blueprint. Watsoncompany is commissioned to manufacture the sample.2．The biomechanical mechanical testing of new vertebral expander comparing withthe traditional balloon kyphoplasty：Totally28selected human vertebrae were harvest from4fresh—frozen cadaverspines(T11～L5,age55～83years,averaged75.5years,male1and female3).The specimenswere disarticulated,excised the soft tissue possibly and remove the posterior elements tomore readily facilitate the mechanical testing.All these specimens were randomly dividedinto2groups:an experimental vertebral expander system（experimental groups） andballoon kyphoplasty（comparison groups）.Each group contains a total of14vertebralbodies.Height measurements of all these vertebrae were taken with digital calipers accurateto0.02mrn to record the anterior height before creating a simulated vertebral compression fracture using a HD-5000B frequency converting control material testing machine(HuahuiTesting Instruments,Yangzhou, supported by the orthopaedic laboratory of Suzhouuniversity). Anterior height and strength of all these vertebrae were takenagain.Subsequently all the vertebral bodies were operated kyphoplasty with experimentalvertebral expander system（experimental groups）and balloon kyphoplasty(comparisongroups). The vertebral altitude change and strength change before and after operation, thedifference of the injection quantity of bone cement between experimental groups andcomparison groups were comparative analysed in the process of experiment.Results1. From top to bottom, lumbar pedicle transverse diameter, sagittal diameter widensincreasingly.The vertebral (T11～L5)sagittal diameter were significantly higher thanvertebral body transverse diameter.（P<0.05）2. The biggest power provided by the new vertebral body expander can reach172.26+/-23.73N, the maximum height can reach14mm in the fully open. Anterior height andstrength of both experimental groups and comparison groups were improved obviouslybefore and after operation. And the result of experimental groups is better than controlgroups.（P<0.05）ConclusionThe design and fabrication of the new vertebral expander system comply with lumbarpedicle structural features. It can raised the edge of fractured vertebral body and createcertain internal cavity in the fractured vertebral body successfully. Therefore, this new typeof vertebral body dilator is a new way to treat vertebral compression fracture.