Spinal fixation using acrylic bone cement: mechanical property measurements

[Cement augmentation in spinal surgery]

Bone cement has been used in spinal surgery for as long as 50 years. In contemporary spinal surgery, cement augmentation of fractured osteoporotic vertebrae in the form of vertebroplasty/kyphoplasty as well as cement augmentation of pedicle screws in instrumented procedures of any etiology are established as standard procedures. Both procedures are very effective, although the benefits of vertebroplasty/kyphoplasty procedures have been controversially discussed in the past. Overall, complications rarely occur. The most relevant complication is cement leakage, which is asymptomatic in the majority of cases but in the worst case might lead to neurological deficits, embolic events and even circulatory collapse. Prevention of cement leakage is therefore crucial. Risk factors for cement leakage and preventive measures are presented in a comprehensive review based on the available literature.

Materials and design of spinal implants--a review

Man-made devices have been implanted into the body to relieve pain, to restore function, and to facilitate healing. The subjects of this review are the materials, and to a lesser extent, the design aspects of the numerous implants that are available to the surgeon in dealing with the ailing spine. Often it is the material aspects of such devices that are responsible for their success or failure. It may be that osteoconductive properties are desired for implants to assist fusion, whereas as inert a material as possible would be preferred for interpositional barriers. The materials composing the instrumentation used to facilitate healing of spinal fractures would ideally have properties that optimize strength and biocompatibility, while at the same time minimizing imaging artifacts and allowing a gradual transfer of load from the instrumentation to the vertebral body (i.e., viscoelastic effects). The application of biomaterials and biomechanics to the design of spinal devices is obvious; what may be more subtle though is what the in vivo interactions of these will be. The study of such aspects must continue in order to better evolve the designs and subsequent results of implanted spinal devices.

Mechanical properties of bone cement: a review

Many authors have examined the mechanical properties of bone cement and the various factors that affect its mechanical behavior. This article presents a comprehensive survey on the reported mechanical properties of bone cement. Variables that influence the mechanical properties, such as handling characteristics, strain rate, loading modes, additives, porosity, blood inclusion, in vivo environment, temperature, etc. have also been reviewed. The importance of specifying these variables in reporting test results on the mechanical properties of bone cement is pointed out. Previous attempts to improve the mechanical properties of bone cement are also summarized. Future research areas important for fully characterizing the physical properties of PMMA are also suggested.