title: Biomechanical evaluation of a bipedicular spinal fixation device: three different strength tests.
abstract: Disadvantages of thoracic posterior implants and developments in rod contouring in situ led to the design of a new spinal implant: the bipedicular spinal fixation device (BSF). The BSF is composed of two bifid hooks linked by a compression transverse connector and inserted into the costo-vertebral and costo-transverse joints. The aim of this biomechanical study was to determine the loading tolerance of the BSF. Three strength tests-a pull-out test, a lateral load-to-failure test and a uniaxial transversal compression test to failure-were performed using six human thoracic spines on an Instron testing device. Specimen evaluation consisted of: bone mineral density (BMD) measurement with the dual-energy X-ray absorptiometry (DEXA) technique, cortical thickness measurements and a morphometric study. The mean values for load-to-failure in the posterior and lateral tests were 324 N and 400 N respectively. The mean value of the uniaxial compression was 988 N. The mean BMD estimated by DEXA was 0.557 g/cm(2). The BSF loading tolerance was compatible with the in situ rod contouring technique requirements when we considered posterior and lateral pull-out tests. The transversal compression test determined the appropriate and efficient BSF tightening force.
authors.affiliation: Service de Chirurgie Orthopédique, du Rachis et de Traumatologie du Sport, Hôpital Civil de Strasbourg, 1 Place de l'Hôpital, 67091, Strasbourg, France. lbalabaud@wanadoo.fr
authors.forename: Laurent
authors.initials: L
authors.lastname: Balabaud
authors.forename: Emeric
authors.initials: E
authors.lastname: Gallard
authors.forename: Wafa
authors.initials: W
authors.lastname: Skalli
authors.forename: Bernard
authors.initials: B
authors.lastname: Dupas
authors.forename: Robert
authors.initials: R
authors.lastname: Roger
authors.forename: François
authors.initials: F
authors.lastname: Lavaste
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Steib
mesh_terms: D015502:Absorptiometry, Photon; D000368:Aged; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D002102:Cadaver; D006801:Humans; D016268:Internal Fixators / Q000592:standards* / Q000639:trends; D008297:Male; D008422:Materials Testing / Q000295:instrumentation*; D008875:Middle Aged; D013123:Spinal Fusion / Q000295:instrumentation* / Q000379:methods; D013314:Stress, Mechanical; D013904:Thoracic Vertebrae / Q000033:anatomy & histology / Q000502:physiology / Q000601:surgery*; D016474:Weight-Bearing / Q000502:physiology