The Benefits of Cement Augmentation of Pedicle Screw Fixation Are Increased in Osteoporotic Bone: A Finite Element Analysis.

Study Design: Biomechanical study using a finite element model of a normal and osteoporotic lumbar vertebrae comparing resistance with axial pullout and bending forces on polymethylmethacrylate-augmented and non-augmented pedicle screws.

Objective: To compare the effect of cement augmentation of pedicle screw fixation in normal and osteoporotic bone with 2 different techniques of cement delivery.

Summary Of Background Data: Various clinical and biomechanical studies have addressed the benefits of cement augmentation of pedicle screws, but none have evaluated whether this effect is similar, magnified, or attenuated in osteoporotic bone compared with normal bone.

Comparison of biomechanical function at ideal and varied surgical placement for two lumbar artificial disc implant designs: mobile-core versus fixed-core.

Study Design: Finite element model.

Objectives: To estimate the effect of lumbar mobile-core and fixed-core artificial disc design and placement on the loading of the facet joints, and stresses on the polyethylene core.

Summary Of Background Data: Although both mobile-core and fixed-core lumbar artificial disc designs have been used clinically, the effect of their design and the effect of placement within the disc space on the structural element loading, and in particular the facets and the implant itself, have not been investigated.