Biomechanical In Vitro Test of a Novel Dynamic Spinal Stabilization System Incorporating Polycarbonate Urethane Material Under Physiological Conditions

Abstract

Posterior dynamic stabilization systems (PDSS) were developed to provide stabilization to pathologic or hypermobile spinal segments while maintaining the healthy biomechanics of the spine. Numerous novel dynamic devices incorporate the temperature and moisture dependent material polycarbonate urethane (PCU) due to its mechanical properties and biocompatibility. In this study, standardized pure moment in vitro tests were carried out on human lumbar spines to evaluate the performance of a device containing PCU. An environmental chamber with controlled moisture and temperature was included in the setup to meet the requirements of testing under physiological conditions. Three test conditions were compared: (1) native spine, (2) dynamic instrumentation, and (3) dynamic instrumentation with decompression. The ranges of motion, centers of rotation, and relative pedicle screw motions were evaluated. The device displayed significant stiffening in flexion–extension, lateral bending, and axial rotation load directions. A reduction of the native range of motion diminished the stiffening effect along the spinal column and has the potential to reduce the risk of the onset of degeneration of an adjacent segment. In combination with decompression, the implant decreased the native range of motion for flexion–extension and skew bending, but not for lateral bending and axial rotation. Curve fittings using the sigmoid function were performed to parameterize all load-deflection curves in order to enhance accurate numerical model calibrations and comparisons. The device caused a shift of the center of rotation (COR) in the posterior and caudal direction during flexion–extension loading.

Motion preservation surgery for scoliosis with a vertebral body tethering system: a biomechanical study

“…The ROM of the whole spine (T10-L3) and L1-L2 segment were calculated as described previously by Beckmann et al [18,23]. The Euler angles recorded by the magnetic tracking system were converted to rotation matrices for each sensor.…”

“…After the resin solidified, a strong fixation was created with the vertebrae and easy access to the segment structures for insertion of the instrumentations. Subsequently, the segments were stored at − 18 °C in sealable bags and thawed at 8 °C for 16 h (including embedding time) before testing [17,18].…”

“…The second tether was inserted without pretension. The sequence of the trials within each test condition and the groups were randomized to avoid bias such as screw loosening and softening effects of specimen degeneration [18,24].…”

Biomechanical Performance of BoneHelix® Compared with Elastic Stable Intramedullary Nailing (ESIN) in a Pediatric Tibia Fracture Model

“…Due to close similarities in anatomy and morphology, porcine bone is a suitable alternative to human bone for investigation of bone implants [31,32]. Specimens were stored at −18 • C and were thawed for over 16 h at 8 • C before testing [33,34]. Each tibia was separated from the knee joint and the fibula, and all soft tissue was removed from the bone.…”

Análisis biomecánico de la ligamentoplastía interespinosa con fibra de poliéster posterior a discectomía

“…10,11 Dentro de los dispositivos de estabilización dinámica en el área de la enfermedad de la columna lumbar, tenemos como ejemplos de implantes interespinosos el dispositivo DIAM (Metronic), Wallis (Spain Next), Minns, In-Space (Synthes). 12,13,14,15 La ligamentoplastía interespinosa (ILP) es un ejemplo de estabilización dinámica y fue introducido por primera vez por Senegas y colaboradores para el tratamiento de la espondilolistesis degenerativa después de una laminectomía extensa, restringiendo la flexión de la columna lumbar preservando el ligamento interespinoso y supraespinoso. 16 En la actualidad, el uso del ligamento de poliéster (Dallos ® ) en la ligamentoplastía interespinosa se extiende a diversas patologías de la columna lumbar después de una fijación y fusión vertebral, tras una discectomía clásica, espondilolistesis degenerativa, inestabilidad angulatoria de…”