Abstract
BACKGROUND
This scientific work is a non-interventional, experimental and prospective comparative study of two very high-viscosity PMMA bone cements: DePuy CMW 2G and Palacos® fast R+G. Reference product: Palacos® R+G.
Fast-setting PMMA bone cements are used in the endoprothetics of the patella and knee (in Australia) and are also used to cement an artificial acetabulum (in the UK). Are there any differences regarding the characteristics of the two fast-setting PMMA bone cements?
MATERIALS AND METHODS
All cements were mixed as specified by the manufacturer and analysed on the following parameters: handling properties (mixing, waiting, working and hardening phase), powder/liquid-ratio, mechanical properties (ISO 5833:2002 and DIN 53435), fatigue strength (ISO 16402) and elution profile. All tests were done in an acclimatised laboratory with temperatures set at 23.5°C ± 0.5°C and a humidity of >40%. Of two batch numbers, 11 units of each bone cement were tested.
RESULTS AND DISCUSSION
The handling properties of the two tested PMMA bone cements Palacos® fast R+G and CMW 2G are highly similar (n=12). CMW 2G reaches the mixing and waiting phase approximately 20s later than Palacos® fast R+G. Palacos® fast R+G has a similar working, but a shorter hardening phase than CMW 2G.
In addition, working with Palacos® fast R+G was advantageous due to its green dye. Palacos® fast R+G has a higher powder/liquid-ratio of 2.550. Due to the higher powder percentage, the cement has a shorter mixing and waiting phase than CMW 2G with a ratio of 2:1.
Both analysed bone cements fulfil the quasi-static properties of ISO 5833:2002 and DIN 53435. Palacos® fast R+G was far superior in its ISO compressive strength (MPa) shown through one-way analysis of variance (ANOVA) (p<0.01) and independent two sample t-test (p<0.01) at 0.05 level of significance (n=20)(Fig. 1). CMW 2G has a higher quasi-static ISO bending strength (MPa) than Palacos® fast R+G, but the same test shows a much higher fatigue strength (ISO 16402) of Palacos® fast R+G (n=5) (Fig. 2).
Palacos® R+G and Palacos® fast R+G show a similar elution profile (n=3), whereas CMW 2G shows a much lower antibiotic elution over time. CMW 2G releases approximately 1/3 of gentamicin per mould body after 24h. After day 3 and 5, CMW 2G has a significantly lower gentamicin release than Palacos® fast R+G (Fig. 3). Palacos® fast R+G has a higher gentamicin release, due to its hydrophilic polymer basis, which is identical to Palacos® R+G. CMW 2G contains pure PMMA and is therefore more hydrophobic than the other two tested cements.
CONCLUSION
Handling with Palacos® fast R+G was advantageous due to its green dye. Because of the shorter handling phases of Palacos® fast R+G, it is superior as it minimises the length of surgeries. Mechanical properties according (ISO 5833:2002 and DIN 53435) were comparable. Palacos® fast R+G has a statistically significant higher ISO compressive strength (MPa). Palacos® fast R+G also showed higher fatigue strength (ISO 16402). Palacos® fast R+G was far superior in matters of gentamicin release over time.
