An in vitro optimized injectable calcium phosphate cement for augmenting screw fixation in osteopenic goats

Abstract

This study reports the proportioning and standardized mixing procedures for preparing a hydroxylapatite cement (tetracalcium phosphate and dicalcium phosphate) of desired viscosity and mechanical strength reproducibly for application in trauma surgery. The behavior and the biomechanical properties of the resulting bone cement in screw augmentation were then evaluated in our osteopenic goat model. The use of a shaker standardized the mixing procedure. The optimal volume of Na2HPO4 used to prepare the injectable cement was 0.45 mL/g, with averaged in vitro compressive strength of 48.29 +/- 5.62 MPa. Histology showed increasing tightly-coupled bone apposition on the cement surface without fibrous encapsulation as observed in the screw-only controls with time in the osteopenic goat model. The cement increased the initial screw pull-out force (54.7%, p = 0.005) significantly and the energy required to failure (54.7%, p < 0.05) significantly, and remained higher than the screw-only controls after 3 months (9.8% and 20.2%, respectively) and 6 months (20.2% and 44.7%, respectively). These results imply potential in the prevention of interfacial micromotions and subsequent fibrous tissue formation at the implant-bone interface resulting in a decreased risk of implant failure. The optimized cement in this study may serve as a good candidate for augmenting fixation of osteoporotic bone.

Self-Setting Calcium Orthophosphate Formulations: Cements, Concretes, Pastes and Putties

“…Therefore, a mixing procedure is very important because prior to be injected, a cement paste must be transferred from a mixing chamber into a syringe. Ideally, this should be done without trapping air bubbles by the cement paste [256]. Earlier, most calcium orthophosphate cements were manually mixed with aqueous solutions using a mortar and either a pestle or a spatula.…”

“…It allows mixing the cement paste within 60 -80 s and enables a rapid and reliable filling of the application syringe [34]. Besides, a cement powder and an aqueous solution might be placed into a syringe and mixed inside a shaker to produce a consistent cement paste of the desired viscosity [256]. A mechanical mixing was found to decrease both the mean viscosity of the curing cement paste and variability in the viscosity at a given time [258].…”

Biomechanical and finite element analyses of bone cement‐Injectable cannulated pedicle screw fixation in osteoporotic bone

“…Nevertheless, using PMMA-augmented pedicle screws is considered to be a precise and effective method. [11][12][13][14][15] In particular, PMMA-augmented screws designed with a cannulated PMMA-outflow tract have a bright application prospect. [42][43][44] According to these previous findings, the CICPS was designed so that its three side holes were arranged from smallest to largest at two fifths the distance from the distal end of the screw.…”

An approximate model for cancellous bone screw fixation

“…However the optimal relationship between cement distribution and strength properties has hitherto only been explored in an empirical manner. Studies have investigated the use of PMMA [ 44,32,18,6,10,20] while others have investigated the use of calcium phosphate cements [14,29] or calcium sulphate cements [24,22] and compared these bioresorbable/biodegradable cements to PMMA [22,35]. Page 4 Many of the studies are based on in vitro tests.…”