In vivo bone response to porous calcium phosphate cement

Abstract

We conducted an in vivo experiment to evaluate the resorption rate of a calcium phosphate cement (CPC) with macropores larger than 100 microm, using the CPC called Biocement D (Merck Biomaterial, Darmstadt, Germany), which after setting only shows pores smaller than 1 microm. The gas bubble method used during the setting process created macroporosity. Preset nonporous and porous cement implants were inserted into the trabecular bone of the tibial metaphysis of goats. The size of the preset implants was 6 mm and the diameter of the drill hole was 6.3 mm, leaving a gap of 0.3 mm between implant surface and drill wall. After 2 and 10 weeks, the animals were euthanized and cement implants with surrounding bone were retrieved for histologic evaluation. Light microscopy at 2 weeks revealed that the nonporous implants were surrounded by connective tissue. On the cement surface, we observed a monolayer of multinucleated cells. Ten weeks after implantation, the nonporous implants were still surrounded by connective tissue. However, a thin layer of bone now covered the implant surface. No sign of cement resorption was observed. In contrast, the porous cement evoked a completely different bone response. At 2 weeks, bone formation had already occurred inside the implant porosity. Bone formation even appeared to occur as a result of osteoinduction. Also, at their outer surface, the porous implants were completely surrounded by bone. At 2 weeks, about 31% of the initial cement was resorbed. After 10 weeks, 81% of the initial phosphate cement was resorbed and new bone was deposited. On the basis of these observations, we conclude that the creation of macropores can significantly improve the resorption rate of CPC. This increased degradation is associated with almost complete bone replacement.

Interlaboratory studies on in vitro test methods for estimating in vivo resorption of calcium phosphate ceramics

“…Resorbable calcium phosphates include β-tricalcium phosphate (β-TCP), α-tricalcium phosphate, carbonated hydroxyapatite, low-crystalline hydroxyapatite, and a certain range of biphasic hydroxyapatite and β-TCP. These calcium phosphates are not only osteoconductive but are also gradually resorbed in a long period of time after implantation [1][2][3][4][5][6][7][8][9][10]. The rate of resorption needs to be optimized depending on the intended purpose and be balanced with bone tissue regeneration for successful clinical treatments.…”

May dubel be a solution for pullout problem of the pedicle screws at osteoporotic spine?

“…The use of PMMA cement for pedicle screw augmentation has been reported in literature (4,6,23,24,27) Kyphoplasty-based or vertebroplasty-based pedicle screw augmentations are performed to yield significantly greater pullout strength (1,6,28). PMMA, calcium phosphate and injectable bioactive ceramic resins have all been used to augment vertebral screws (7-9, 12,17,20,21,23,26,29,31,32).…”

Self-Setting Calcium Orthophosphate Formulations

“…Besides, pore forming CO 2 bubbles appear at hardening of apatite-forming formulations, consisting of an acidic calcium orthophosphate, such as MCPM or DCPD, and either CaCO 3 [30,50,[69][70][71] or NaHCO 3 [373][374][375]. Furthermore, addition of an effervescent porogen formulation comprised from NaHCO 3 (54.52%) and citric acid monohydrate (45.48%) has been suggested [376].…”

“…In a dense, mineralized biomaterials such as hardened calcium orthophosphate formulations, which provide a barrier to the free diffusion of circulating hormones, growth factors, and cytokines, it is questionable whether the local responses at the periphery of the material regulate osteoconduction [22]. The tissue response to injectable calcium orthophosphate formulations is well described in literature [373,408,423,440,441]. Recent histological and mechanical evaluation in a sheep vertebral bone void model is available elsewhere [442].…”