Premixed rapid-setting calcium phosphate composites for bone repair

Abstract

Although calcium phosphate cement (CPC) is promising for bone repair, its clinical use requires on site powder-liquid mixing. To shorten surgical time and improve graft properties, it is desirable to develop premixed CPC in which the paste remains stable during storage and hardens only after placement into the defect. The objective of this study was to develop premixed CPC with rapid setting when immersed in a physiological solution. Premixed CPCs were formulated using the following approach: Premixed CPC = CPC powder + nonaqueous liquid + gelling agent + hardening accelerator. Three premixed CPCs were developed: CPC-monocalcium phosphate monohydrate (MCPM), CPC-chitosan, and CPC-tartaric. Setting time for these new premixed CPCs ranged from 5.3 to 7.9 min, significantly faster than 61.7 min for a premixed control CPC reported previously (p < 0.05). SEM revealed the formation of nano-sized needle-like hydroxyapatite crystals after 1 d immersion and crystal growth after 7 d. Diametral tensile strength for premixed CPCs at 7 d ranged from 2.8 to 6.4 MPa, comparable to reported strengths for cancellous bone and sintered porous hydroxyapatite implants. Osteoblast cells attained a normal polygonal morphology on CPC-MCPM and CPC-chitosan with cytoplasmic extensions adhering to the nano-hydroxyapatite crystals. In summary, fast-setting premixed CPCs were developed to avoid the powder-liquid mixing in surgery. The pastes hardened rapidly once immersed in physiological solution and formed hydroxyapatite. The cements had strengths matching those of cancellous bone and sintered porous hydroxyapatite and non-cytotoxicity similar to conventional non-premixed CPC.

Properties of Powder Composite Polyhydroxybutyrate–Chitosan-Calcium Phosphate System

“…Besides the lower degree of transformation (approx. 74 %) of microcrystalline calcium phosphate cement components to very fine globular nanohydroxyapatite particles was detected in these composites after 7 days of setting [30]. Similar values of CS (11 MPa) were found in CPC chitosan composites (15% of chitosan addition in hardening liquid) with 90% degree of the transformation of calcium phosphates after 7 days of setting [31].…”

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…Other polymers, such as polyphosphazene, might be used as well [460][461][462]. Other examples of polymer/calcium orthophosphate cement formulations might be found elsewhere [463,464].…”

Untitled

“…Calcium phosphate cement has been successfully used in clinics as bone repair biomaterial for many years [31][32][33][34][35][36] . However, poor mechanical properties limit any further applications [37][38][39] .…”