AbstractsBiology & Animal Science

The availability of pre-operative data on the biomechanical stability of an annular repair device may influence the clinical management of lumbar spine surgery. Having the knowledge of the performance of various annular repair devices can assist in the selection of better choices for treatment. Numerous studies investigated the effect of various implants such as artificial nucleus replacement, repair or annular tears, novel annulus repair devices with full or partial discectomy etc. However, the area of nucleus and annulus repair technology still needs to be further researched upon to devise an alternative disc replacement device that would reduce pain, minimize the restriction of range of motion and decrease the degenerative effects on the adjacent segments. As a first step towards achieving this goal, an implant must be tested under appropriate biomechanical protocols to study its stability during complex physiological motion that is encountered clinically.This study determined the biomechanical performance of a novel annular repair device in an in-vitro in the human cadaveric lumbar spine. The test criterion was to evaluate implant migration during complex cyclic loading, study its effects on the range of motion of the functional spinal segment and intradiscal pressures. The overall stability of the device is studied under extreme physiological impact loading and the finite element analysis of the construct is conducted and compared to the in vitro data.Six human cadaveric lumbar functional spine unit specimens (L2-Sacrum < 70 years of age) were gathered for testing. Each cadaveric specimen (L2 - L5) was cleaned of all muscle and adipose tissue and dissected into L2-3 and L4-5 motion segments. Specimens were stored double bagged at -20° C and allowed to thaw at room temperature for 10 to 12 hours prior to any manipulation. Cadaveric vertebral samples provide a natural and appropriate geometric and material sample for study but may lead to significant variability due to natural patient variation. Thus, they were assessed with DEXA scans prior to use. Each specimen was stripped of soft tissue and disarticulated into separate functional spinal segments. Axial and lateral images of each vertebra were captured by fluoroscopy prior to any testing and quantified with digital analysis using Imaging software. Implant placement was confirmed under fluoroscopy. Specimens were cyclically loaded in load control through 250,000 cycles of ± 7.5 Nm of bending moment applied by offset superior-inferior loads at the cephalic endplate of the vertebral body potted in a rigid urethane compound mount in customized fixtures with a fixed moment arm. Loads were applied using an MTS servo hydraulic test frame. Following cyclic loading of the specimens, three dimensional motion tracking was performed on all the specimens. Fluoroscopy was obtained to establish the position of the implant using digital image analysis. Finally, specimens were impact loaded to failure in compression. Implant migration was studied using digital image analysis…