Comparative studies of cervical spine anterior stabilization systems - Finite element analysis

Resorbable plating system stabilizes tissue‐engineered intervertebral discs implanted ex vivo in canine cervical spines

“…In this context, degradation of the PLGA system is expected to promote a gradual change in load distribution between the TE‐IVD and the PLGA plate, unlike the case of existing interbody spinal fusion techniques and external fixation devices previously evaluated in human cadaveric spines . Mackiewicz et al confirmed in a finite element study that introducing highly stiff stabilizing plates into cervical spine motion segments increases stress in the endplate of adjacent segments and that plates that allow greater range of motion show up to 30% reduction of adjacent plates resulting stress . Matge et al discussed clinical and radiological observations that suggest dynamic cervical implants as a promising alternative to total disc replacement, anterior cervical discectomy and spinal fusion, and they indicate that preserving motion segment biomechanics reduces stress on facet joints and development of adjacent segment disease.…”

“…[29][30][31][32] Mackiewicz et al confirmed in a finite element study that introducing highly stiff stabilizing plates into cervical spine motion segments increases stress in the endplate of adjacent segments and that plates that allow greater range of motion show up to 30% reduction of adjacent plates resulting stress. 33 Matge et al 34 discussed clinical and radiological observations that suggest dynamic cervical implants as a promising alternative to total disc replacement, anterior cervical discectomy and spinal fusion, and they indicate that preserving motion segment biomechanics reduces stress on facet Figure 3D), since the inclined shape of the endplate in the ventral side combined with the lack of anchoring for the implant resulted in a wedge-like extrusion. These observations were consistent with the mechanism of extrusion observed in the displaced implants of our in vivo canine study.…”

“…We adapted the cell preparation methods from previously established protocols. 8,9 Briefly, we harvested cervical IVDs from three skeletally mature canine spines (18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36) Similarly, we based the TE-IVD fabrication process on established techniques. 9,15 First, we mixed encapsulated canine NP cells (25 × 10 6 cells/mL) in 3% wt./vol.…”

Intraoperative biomechanics of lumbar pedicle screw loosening following successful arthrodesis

“…A theoretical stress analysis of monotonic cantilever loading in transverse compression and bending and press‐fit by screw insertion was performed to estimate the stresses in peri‐implant pedicle bone with or without loosening of the screw. The trabecular bone of the pedicle was assumed to have an effective modulus of 42.8 MPa and a Poisson ratio of 0.25, while the cortical bone was assigned a modulus of 21 GPa and a Poisson ratio of 0.37 (Appendix Table SA1) . The modulus of the titanium screws was assumed to be 180 MPa.…”

“…The trabecular bone of the pedicle was assumed to have an effective modulus of 42.8 MPa and a Poisson ratio of 0.25, while the cortical bone was assigned a modulus of 21 GPa and a Poisson ratio of 0.37 (Appendix Table SA1). [29][30][31][32] The modulus of the titanium screws was assumed to be 180 MPa. Loading of the spine causes cantilevered loads and moments to be transmitted through the instrumentation, resulting in both a transverse load and moment to be distributed to the surrounding trabecular bone along the embedded length of the screw.…”