Influence of initial component temperature on the apparent viscosity and handling characteristics of acrylic (PMMA) bone cement

Abstract

The flow and polymerization characteristics of poly(methylmethacrylate) (PMMA) bone cement can be changed by manipulating the temperature of the bone cement components or the environment that they are prepared in. To quantify the effects of the initial component temperature (T(ic)) of acrylic bone cement on the rheological and handling characteristics, ASTM F451-99a compliant methods and clinically relevant testing methods were utilized. A rheometer was designed and fabricated using the dimensions of a clinical, commercially available, cement gun and nozzle. The influence on the apparent viscosity and handling characteristics (setting time, working time, and peak exotherm temperature) for a high viscosity (HV) commercially-available acrylic bone cement, Palacos R, were determined. The values of T(ic) used were 23 degrees C (room), 6 degrees C (refrigerator), and -14 degrees C (freezer). Using the apparent viscosity of a medium viscosity (MV) bone cement as a benchmark (Simplex P at room temperature), it was found that by adjusting the T(ic) the HV cement was able to mimic the flow characteristics of the MV cement. Lowering the T(ic) lowered the apparent viscosity of the bone cement. The effects of T(ic) on the polymerization of bone cement were studied in dynamic and static conditions. The dynamic test recorded temperature and torque from stirring resistance. Setting times were also determined using the ASTM exotherm mold method. The setting times determined by the dynamic testing conditions were consistently shorter than those determined by the ASTM method. Lowering the T(ic) increased the working and setting times; however, it did not have a significant effect on the peak exotherm temperature.

Pore distribution and material properties of bone cement cured at different temperatures

“…Cement also cures faster at higher temperatures, which decreases the amount of handling time [43]. Viscosity and flow characteristics would also be influenced [44]. This could be a positive or negative factor, depending on the needs of the surgeon.…”

Viscoelastic properties of injectable bone cements for orthopaedic applications: State‐of‐the‐art review

“…In the first, a rotational or capillary extrusion rheometer/viscometer was used 78–81. With this set‐up, the variation of the pressure gradient ( P ) with t m is obtained, which leads to the variation of the apparent or false viscosity of the cement (μ) through use of the Hagen‐Poiseuille equation: where R is the radius of the capillary/die, L is the length of the capillary, and Q is the volumetric flow rate of the cement dough (or the rate at which the cement dough is injected into the capillary).…”

“…For Palacos R, a decrease in the temperature at which the cement was stored prior to mixing ( T st ) led to a decrease in μ throughout the polymerization period 79. Alternatively, for this cement, the time taken to reach a specified viscosity increases with increase in T st 79.…”

Injectable Bone Cements for Spinal Column Augmentation: Materials for Kyphoplasty/Vertebroplasty

“…However, during polymerization of PMMA cement (or formation of HA crystals during setting in the case of calcium phophate cements), the viscosity increases slowly but exponentially with time from the moment of mixing the components until the fully cured state. 132 The interval in which bone cement can safely be injected is often called the working time or injection phase and is dependent on • the initial ratio of ingredients (monomer-to-polymer in PMMA cement and ratio of liquid-to-CaP in CaP cement); 40,133 • the presence of additives in PMMA cement or alternative solutions for CaP cement; 134,135 • the temperature of the components before mixing; 136 • the mixing process itself; 132 • the temperature of the environment ('room temperature') during polymerization/setting; 136 • considering the significant variations in working time under apparently identical circumstances: miscellaneous yet unidentified factors. 45 By trial and error, clinicians have found, rather unscientifically, that the optimal viscosity for safe injection resembles that of toothpaste or spaghetti; cement of lower viscosity (before the injection phase) led to frequent extravasation while cement displaying higher viscosity (after the injection phase) substantially reduced injectability.…”