[In vitro studies on various PMMA bone cements: a first comparison of new materials for arthroplasty]

A prospective randomized study of Refobacin Bone Cement R versus Palacos R + G

Aims

Refobacin Bone Cement R and Palacos R + G bone cement were introduced to replace the original cement Refobacin Palacos R in 2005. Both cements were assumed to behave in a biomechanically similar fashion to the original cement. The primary aim of this study was to compare the migration of a polished triple-tapered femoral stem fixed with either Refobacin Bone Cement R or Palacos R + G bone cement. Repeated radiostereometric analysis was used to measure migration of the femoral head centre. The secondary aims were evaluation of cement mantle, stem positioning, and patient-reported outcome measures.

Methods

Overall, 75 patients were included in the study and 71 were available at two years postoperatively. Prior to surgery, they were randomized to one of the three combinations studied: Palacos cement with use of the Optivac mixing system, Refobacin with use of the Optivac system, and Refobacin with use of the Optipac system. Cemented MS30 stems and cemented Exceed acetabular components were used in all hips. Postoperative radiographs were used to assess the quality of the cement mantle according to Barrack et al, and the position and migration of the femoral stem. Harris Hip Score, Oxford Hip Score, Forgotten Joint Score, and University of California, Los Angeles Activity Scale were collected.

Results

Median distal migration (y-axis) at two years for the Refobacin-Optivac system was -0.79 mm (-2.01 to -0.09), for the Refobacin-Optipac system was -0.75 mm (-2.16 to 0.20), and for the Palacos-Optivac system was -1.01 mm (-4.31 to -0.29). No statistically significant differences were found between the groups. Secondary outcomes did not differ statistically between the groups at the two-year follow-up.

Conclusion

At two years, we found no significant differences in distal migration or clinical outcomes between the three groups. Our data indicate that Refobacin Bone Cement R and Palacos R + G are comparable in terms of stable fixation and early clinical outcomes.

Release characteristics of enoxaparin sodium-loaded polymethylmethacrylate bone cement

BACKGROUND

This study aimed to prepare the polymethylmethacrylate (PMMA) bone cement release system with different concentrations of enoxaparin sodium (ES) and to investigate the release characteristics of ES after loading into the PMMA bone cement.

METHODS

In the experimental group, 40 g Palacos®R PMMA bone cement was loaded with various amount of ES 4000, 8000, 12,000, 16,000, 20,000, and 24,000 AXaIU, respectively. The control group was not loaded with ES. Scanning electron microscopy (SEM) was used to observe the surface microstructure of the bone cement in the two groups. In the experiment group, the mold was extracted continuously with pH7.4 Tris-HCL buffer for 10 days. The extract solution was collected every day and the anti-FXa potency was measured. The experiment design and statistical analysis were conducted using a quantitative response parallel line method.

RESULTS

Under the SEM, it was observed that ES was filled in the pores of PMMA bone cement polymer structure and released from the pores after extraction. There was a burst effect of the release. The release amount of ES on the first day was 0.415, 0.858, 1.110, 1.564, 1.952, and 2.513, respectively, from the six groups with various ES loading amount of 4000, 8000, 12,000, 16,000, 20,000, and 24,000 AXaIU, all reaching the peak of release on the first day. The release decreased rapidly on the next day and entered the plateau phase on the fourth day.

CONCLUSION

The prepared ES-PMMA bone cement has high application potential in orthopedic surgery. ES-PMMA bone cement shows good drug release characteristics. The released enoxaparin sodium has a local anti-coagulant effect within 24 h after application, but it will not be released for a long time, which is complementary to postoperative anti-coagulation therapy.

Loading with vancomycin does not decrease gentamicin elution in gentamicin premixed bone cement

Antibiotic loaded bone cements are used as drug delivery systems for the treatment of periprosthetic joint infections. They can be loaded with antibiotics during industrial component production (premixing) and during cement preparation (manually blending). Although double premixed antibiotic loaded bone cements are available, manually blending of a gentamicin premixed antibiotic loaded bone cement with vancomycin is still popular. We compared in vitro antibiotic elution and compressive strength of 0.5 g gentamicin premixed bone cement (PALACOS® R + G), 0.5 g gentamicin premixed bone cement (PALACOS® R + G) manually blended with 2.0 g vancomycin, 0.5 g gentamicin and 2.0 g vancomycin premixed bone cement (COPAL® G + V), 1 g gentamicin and clindamycin premixed bone cement (COPAL® G + C) and bone cement without an antibiotic (PALACOS® R) as control. Antibiotic concentration measurements were performed for 6 weeks and then compression strength was tested. Concentrations of gentamicin showed no significant differences between PALACOS® R + G, PALACOS® R + G with vancomycin and COPAL G® + V. After 48 h COPAL G® + C produced significantly higher gentamicin concentrations than the other formulations. After 12 h PALACOS® R + G with vancomycin produced significantly higher vancomycin concentrations, but had the lowest compression strength. We found no influence of vancomycin addition on gentamicin elution, irrespectively of the loading method. However, the manually vancomycin blended ALBC produced higher vancomycin concentrations. Compression strength after aging is reduced by loading with vancomycin.

Bone cement product and failure in total knee arthroplasty

Background and purpose - The bone cement market for total knee arthroplasty (TKA) in Norway has been dominated by a few products and distributors. Palacos with gentamicin had a market share exceeding 90% before 2005, but it was then withdrawn from the market and replaced by new slightly altered products. We have compared the survival of TKAs fixated with Palacos with gentamicin with the survival of TKAs fixated with the bone cements that took over the market. Patients and methods - Using data from the Norwegian Arthroplasty Register for the period 1997-2013, we included 26,147 primary TKAs in the study. The inclusion criteria were TKAs fixated with the 5 most used bone cements and the 5 most common total knee prostheses for that time period. 6-year Kaplan-Meier survival probabilities were established for each cement product. The Cox proportional hazards regression model was used to assess the association between bone cement product and revision risk. Separate analyses were performed with revision for any reason and revision due to deep infection within 1 year postoperatively as endpoints. Adjustments were made for age, sex, diagnosis, and prosthesis brand. Results - Survival was similar for the prostheses in the follow-up period, between the 5 bone cements included: Palacos with gentamicin, Refobacin Palacos R, Refobacin Bone Cement R (Refobacin BCR), Optipac Refobacin Bone Cement R (Optipac Refobacin BCR), and Palacos R + G. Interpretation - According to our findings, the use of the new bone cements led to a survival rate that was as good as with the old bone cement (Palacos with gentamicin).

Comparison of femoral component migration between Refobacin bone cement R and Palacos R + G in cemented total hip arthroplasty: A randomised controlled roentgen stereophotogrammetric analysis and clinical study

AIMS

The widely used and well-proven Palacos R (a.k.a. Refobacin Palacos R) bone cement is no longer commercially available and was superseded by Refobacin bone cement R and Palacos R + G in 2005. However, the performance of these newly introduced bone cements have not been tested in a phased evidence-based manner, including roentgen stereophotogrammetric analysis (RSA).

PATIENTS AND METHODS

In this blinded, randomised, clinical RSA study, the migration of the Stanmore femoral component was compared between Refobacin bone cement R and Palacos R + G in 62 consecutive total hip arthroplasties. The primary outcome measure was femoral component migration measured using RSA and secondary outcomes were Harris hip score (HHS), Hip disability and Osteoarthritis Outcome Score (HOOS), EuroQol 5D (EQ-5D) and Short Form 36 (SF-36).

RESULTS

Femoral component migration was comparable between Refobacin bone cement R and Palacos R + G during the two-year follow-up period with an estimated mean difference of 0.06 mm of subsidence (p = 0.56) and 0.08° of retroversion (p = 0.82). Five hips (three Refobacin bone cement R and two Palacos R + G) showed non-stabilising, continuous migration; the femoral cement mantle in these hips, was mean 0.7 mm thicker (p = 0.02) and there were more radiolucencies at the bone-cement interface (p = 0.004) in comparison to hips showing stabilising migration. Post-operative HHS was comparable throughout the follow-up period (p = 0.62). HOOS, EQ5D, and SF-36 scores were also comparable (p-values > 0.05) at the two-year follow-up point.

CONCLUSION

Refobacin bone cement R and Palacos R + G show comparable component migration and clinical outcome during the first two post-operative years. Hips showing continuous migration are at risk for early failure. However, this seems to be unrelated to cement type, but rather to cementing technique. Cite this article: Bone Joint J 2016;98-B:1333-41.

Not all approved antibiotic-loaded PMMA bone cement brands are the same: ranking using the utility materials selection concept

In the literature on in vitro characterization of approved antibiotic-loaded poly(methyl methacrylate) bone cement brands, there is no information on the basis for selection of a given brand for use in cemented arthroplasties. This shortcoming is addressed in the present study. It involved determining four key properties (fatigue limit, fracture toughness, polymerization rate, and phosphate buffered saline diffusion coefficient) for six brands and then using the mean property values, in conjunction with a materials selection methodology, called the utility concept, to rank the brands. It is emphasized that the present work is an illustration of a rational approach to selection of a cement brand and, as such, the study findings are not intended to be recommendations regarding clinical use or otherwise of a brand.

Biomaterials in skull base surgery

Reconstruction materials and techniques for the base of the skull have undergone rapid developments and differentiation in recent years. While mostly autotransplants, collagens or resorbable alloplastic materials are preferred for duraplasties, pronounced organ-specific differences can be observed in the reconstruction of hard tissues. The use of polymethylmethacryl bone cement, once wide-spread, has decreased greatly due to the release of toxic monomers. Bony autotransplants are still used primarily for smaller skull-base defects, intraoperatively formable titanium nets may be also used for larger fronto- or laterobasal reconstructions of bony defects. Defects in visible areas are increasingly closed with preformed titanium or ceramic implants, which are planned and fitted to the individual patient using preoperative CT imaging. At the skull base, this applies especially to reconstructions of the frontal sinus. For extensive reconstructions of the orbita, titanium nets and non-resorbable plastics have proven valuable; in closing smaller defects especially of the orbital floor, resorbable implants based on Polyglactin 901 are also used.

Revision of tibial TKA components: bone loss is independent of cementing type and technique: an in vitro cadaver study

BACKGROUND

Different bone cements and various cementation techniques can lead to different bone loss in revision surgery. We investigated the degree of tibial bone loss depending on different cements and techniques.

METHODS

30 tibia specimens were matched into three groups (10 each). In all cases Genesis II tibia component were implanted. In two groups, the tibia base plate alone was cemented with Palacos® R+G and Refobacin® Bone Cement R. In the third group, both tibial base plate and tibial stem were cemented with Palacos® R+G. Afterwards, the specimens were axial loaded with 2000 N for 10,000 cycles. Tibial components were explanted and the required time to explantation was recorded. Bone loss after explantation was measured by CT.

RESULTS

On CT, there was no significant difference in bone loss between cementing techniques (p = 0.077; 95% CI -1.14 - 21.03) or the cements themselves (p = 0.345; 95% CI -6.05 - 16.70). The required time to explantation was 170.6 ± 54.89, 228.7 ± 84.5, and 145.7 ± 73.0 seconds in the first, second, and third groups, respectively.

CONCLUSIONS

Cement technique and type do not influence tibial bone loss in simulated revision surgery of the tibial component in knee arthroplasty.

A prospective randomised radiostereometric analysis trial of SmartSet HV and Palacos R bone cements in primary total hip arthroplasty

Background

Introduction of new bone cements into clinical practice should include radiostereometric studies.

Materials and methods

A prospective randomised radiostereometric study was performed, comparing SmartSet HV and Palacos R acrylic bone cements (without antibiotics) using third-generation cementing techniques in primary total hip arthroplasty. Thirty-five patients (36 hips) undergoing Charnley total hip arthroplasty were randomised to receive either of the two cements and were followed with repeated clinical, radiographic and radiostereometric examinations over 24 months. Twenty-seven patients (28 hips) attended 2 years postoperatively.

Results

The mean distal translation observed was −0.15 mm for SmartSet HV and −0.16 mm for Palacos R. The mean rotation around the longitudinal axis was 0.9° for SmartSet HV and 1.2° for Palacos R. The Merle d’Aubigne Postel score was the maximum of 18 points for all patients in both groups.

Conclusions

No statistically significant difference in stem fixation with use of SmartSet HV and Palacos R was found at 2-year follow-up.

Physical aging and the creep behavior of acrylic bone cements

The creep deformation of two acrylic bone cements, Palacos R+G and SmartSet GHV, was investigated for different physical aging times ranging from 45 min to 2 (1/2) years. The experiments were carried out in a three-point-bending set-up in 37 degrees C Ringer's solution applying 10 MPa or 25 MPa creep loads. Both bone cements exhibit a significant decrease of their creep compliance with increasing physical aging time. The experimental data were analyzed with a creep law discussed in the context of physical aging by Struik, and a modified Burgers' model which can be used to separate the strain response of the bone cements into an elastic, a visco-elastic and a creep component. The creep behavior of the bone cements could be described essentially with only one parameter of Struik's creep law. The analysis with the modified Burgers' model showed that physical aging influences all model parameters which are directly related to the mobility of the polymer chains. The effect of physical aging should be taken into account particularly if the mechanical performance of bone cements shortly after curing is investigated.