Biomedical Engineering Reference
In-Depth Information
found elsewhere [567, 568], while an experimental study on calcium
orthophosphate cement impregnated with dideoxy-kanamycin B is
also available [569].
Although most materials currently used as drug carriers are
polymers, in the specific field of the pharmacological treatment of
skeletal disorders, self-setting calcium orthophosphate formulations
have an added value due to their bioactive character and injectability.
Further details and additional examples of the drug delivery
application of calcium orthophosphate cements are well described
elsewhere [29, 36, 37].
5.8.6
Brief Conclusions on the Medical Applications
To conclude this part, one should stress that despite several
encouraging results, not every surgeon' expectation has been
met yet [569]. First of all, self-setting calcium orthophosphate
formulations are not superior to autografts, despite offering primary
stability against compressive loading [570, 571]. One of the main
concerns of clinicians is to reach higher rates of bioresorption,
an improvement of bone reconstruction and to a lesser extent,
higher mechanical resistance [33]. Besides, clinical application of
the cements in comminuted fractures revealed penetration of the
viscous paste into the joint space [572-574]. The interested readers
are referred to a paper on cement leakage during vertebroplasty
[575]. To date, cadaveric studies have already shown that using
calcium orthophosphate cements with conventional metal fixation
in certain fractures of the distal radius, tibial plateau, proximal femur
and calcaneus can produce better stability, stiffness and strength
than metal fixation alone. Early clinical results have revealed a
reduced time to full load bearing when the cements were used for
augmentation of tibial plateau and calcaneal fractures, more rapid
gain of strength and range of motion when used in distal radius
fractures and improved stability in certain hip fractures [471, 507].
However, surgeons reported on difficulties in filling the vertebral
bodies (a bad injectability of present formulations) and other
problems, such as filter pressing and cement decohesion, observed
during vertebral body injection that resulted in bone instability due to
low mechanical strength as well as long setting times of the cements
[576]. This happens due to not only low mechanical properties
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