Controlled laser ablation of polymethyl methacrylate bone cement

The increasing numbers of re-operations carried out on total hip replacement patients causes considerable difficulty for orthopaedic surgeons. One particular problem lies in the removal of the bone cement inserted during the primary operation without causing damage to the bone. In order to develop a method for differentiating between polymethyl methacrylate (PMMA) bone cement and bone during laser ablation, the laser-induced fluorescence from PMMA has been studied and compared to that from the bone. An Oriel multispec spectrometer was used to analyse and record the radiation emitted during 248-nm excimer laser ablation. There was high-intensity fluorescence from bone relative to that from PMMA and several peaks occurred in the spectrum of bone which were absent from that of PMMA. Monitoring of this emission has enabled controlled laser ablation of bone cement in contact with bone to be achieved in vitro with no damage to the naked eye.     

Fatal fat embolism associated with polymethyl methacrylate bone cement.

Three fatalities after procedures involving the use of polymethyl methacrylate cement are reported. Autopsy studies showed varying degrees of pulmonary fat embolism although lack of correction of operative blood loss was the major factor.     

The dynamic volume changes of polymerising polymethyl methacrylate bone cement

The Swedish hip register found an increased risk of early revision of vacuum-mixed cemented total hip replacements. The influence of cement mixing technique on the dynamic volume change in polymerising PMMA is not well understood and may be relevant to this observation. Applying Archimedes' principle, we have investigated the dynamic volume changes in polymerising cement and determined the influence of mixing technique. All specimens showed an overall volume reduction: hand-mixed 3.4% and vacuum-mixed 6.0%. Regression analysis of sectional porosity and volume reduction showed a highly significant relationship. Hand-mixed porous cement showed a transient volume increase before solidification. However, vacuum-mixed cement showed a progressive volume reduction throughout polymerisation. Transient expansion of porous cement occurs at the critical time of micro-interlock formation, possibly improving fixation. Conversely, progressive volume reduction of vacuum-mixed cement throughout the formation of interlock may damage fixation. Stable fixation of vacuum-mixed cement may depend on additional techniques to offset the altered volumetric behaviour of vacuum-mixed cement.     

The dynamic volume changes of polymerising polymethyl methacrylate bone cement

The Swedish hip register found an increased risk of early revision of vacuum-mixed cemented total hip replacements. The influence of cement mixing technique on the dynamic volume change in polymerising PMMA is not well understood and may be relevant to this observation.

Applying Archimedes' principle, we have investigated the dynamic volume changes in polymerising cement and determined the influence of mixing technique. All specimens showed an overall volume reduction: handmixed 3.4% and vacuum-mixed 6.0%. Regression analysis of sectional porosity and volume reduction showed a highly significant relationship.

Hand-mixed porous cement showed a transient volume increase before solidification. However, vacuummixed cement showed a progressive volume reduction throughout polymerisation.

Transient expansion of porous cement occurs at the critical time of micro-interlock formation, possibly improving fixation. Conversely, progressive volume reduction of vacuum-mixed cement throughout the formation of interlock may damage fixation. Stable fixation of vacuum-mixed cement may depend on additional techniques to offset the altered volumetric behaviour of vacuum-mixed cement.     

Effects of self-blood on the molding process of polymethyl methacrylate bone cement

Objective：To evaluate whether the self-blood has influence on the molding process of polymethyl methacrylate （PMMA） bone cement,and to make sure whether it is valuable for the clinical practice.Methods：An in vitro study was performed to evaluate the prolonging-effect of self-blood on PMMA bone cement.The effect of prolonging was evaluated by the dough time （TD） and operable time （To）.Moreover,hardness test,squeezing value test and peak temperature test were also conducted to complete the evaluation of this program.Results：The self-blood,especially the plasma,could greatly prolong the handling time of PMMA bone cement without affecting its basic characteristics including hardness,leakage level and peak temperature.On the other hand,we found that in some abnormal conditions,for example with hyperlipemia,self-blood though can also prolong the handling time,would cause some sideeffects.Conclusion：We report a new effective way to prolong the handling time of PMMA bone cement by adding moderate amount of self-blood.But “individualized medicine” should be noticed because some abnormal conditions like hyperlipemia would cause undesired side-effects.     

Dynamic void behavior in polymerizing polymethyl methacrylate cement

Cement mantle voids remain controversial with respect to survival of total hip arthroplasty. Void evolution is poorly understood, and attempts at void manipulation can only be empirical. We induced voids in a cement model simulating the constraints of the proximal femur. Intravoid pressure and temperature were recorded throughout polymerization, and the initial and final void volumes were measured. Temperature-dependent peak intravoid pressures and void volume increases were observed. After solidification, subatmospheric intravoid pressures were observed. The magnitude of these observations could not be explained by the ideal gas law. Partial pressures of the void gas at peak pressures demonstrated a dominant effect of gaseous monomer, thereby suggesting that void growth is a pressure-driven phenomenon resulting from temperature-dependent evaporation of monomer into existing trapped air voids.     

The long-term in vivo behavior of polymethyl methacrylate bone cement in total hip arthroplasty

Background and purpose

The long-term success of cemented total hip arthroplasty (THA) has been well established. Improved outcomes, both radiographically and clinically, have resulted mainly from advances in stem design and improvements in operating techniques. However, there is concern about the durability of bone cement in vivo. We evaluated the physical and chemical properties of CMW1 bone cements retrieved from patients undergoing revision THA.

Methods

CMW1 cements were retrieved from 14 patients who underwent acetabular revision because of aseptic loosening. The time in vivo before revision was 7–30 years. The bending properties of the retrieved bone cement were assessed using the three-point bending method. The molecular weight and chemical structure were analyzed by gel permeation chromatography and Fourier-transform infrared spectroscopy. The porosity of the bone cements was evaluated by 3-D microcomputer tomography.

Results

The bending strength decreased with increasing time in vivo and depended on the density of the bone cement, which we assume to be determined by the porosity. There was no correlation between molecular weight and time in vivo. The infrared spectra were similar in the retrieved cements and in the control CMW1 cements.

Interpretation

Our results indicate that polymer chain scission and significant hydrolysis do not occur in CMW1 cement after implantation in vivo, even in the long term. CMW1 cement was stable through long-term implantation and functional loading.The concept behind Charnley low-friction arthroplasty was established in the 1960s, and the fundamental principles have remained unchanged since then. Several clinical studies have recently reported the long-term success of total hip arthroplasty (THA). Wroblewski et al. (2009) reported good results using Charnley low-friction arthroplasty with a follow-up of 30–40 years. Overall, 90% of hips were free from pain, and activity was normal in 59% of the patients. Carrington et al. (2009) reported the results of the Exeter Universal cemented femoral component after 15–17 years. With an endpoint of revision for aseptic loosening, the survivorship at 17 years was 100% for the femoral component and 90% for the acetabular component. With all reasons for reoperation as the endpoint, the survivorship was 81%. A variety of cemented stems designed according to various concepts have been used, and several improvements have been incorporated into the operating techniques (Madey et al. 1997, Noble et al. 1998, Scheerlinck and Casteleyn 2006). Although self-curing polymethyl methacrylate (PMMA) bone cements have been used for fixation of the implants for the past 50 years, the composition of the cements has remained essentially unaltered. The ultra-long clinical and radiographic success of cemented THA may depend on the mechanical and chemical longevity of the bone cements in vivo.Several authors have reported on the in vivo behavior of PMMA bone cement in the implanted joint. Some studies have shown aging of PMMA in vivo. Hughes et al. (2003) showed a decrease in molecular weight and hydrolysis of PMMA associated with long-term implantation. Looney and Park (1986) reported a reduction in flexural strength but not in compressive strength. Fernandez-Fairen and Vazquez (1983) analyzed the compressive properties of the retrieved CMW1 cements and found a decrease in the compressive modulus and strength after long implantation periods. By contrast, Ries et al. (2006) concluded that the most important factor for the mechanical properties of bone cement in vivo is not the implant duration but the porosity. It remains unknown whether the mechanical and chemical properties of bone cement change in vivo, and how these changes affect the long-term outcome of cemented THA. We investigated various properties, including molecular weight, chemical structure, bending properties, density, and porosity in retrieved bone cements.     

骨基质明胶颗粒/骨水泥复合材料固定人工关节假体的实验研究

[目的]探讨骨基质明胶颗粒(BMG)复合骨水泥(PMMA)用于人工关节假体固定的可行性.[方法]制备成年新西兰白兔股骨中上段15 mm骨缺损,于髓腔内置入直径3 mm的钛棒并以骨水泥或BMG/PMMA复合材料固定,模拟人工股骨头置换术之动物模型,分别进行术后步态、X线检查、生物力学、组织学检查观察.[结果]术后第2d～12周两组动物均可正常行走;术后24h力学检测示两种固定方法无显著性差异;随着时间的延长,骨缺损无短缩;X线及组织学检查示复合材料组钛棒周围有成骨现象,扫描电镜见复合材料内有骨长入.[结论]BMG颗粒/PMMA复合材料固定假体时显示出可靠的力学性能及诱导成骨能力,将可能使其成为一种新的假体固定方法.     

Characterisation of in vivo release of gentamicin from polymethyl methacrylate cement using a novel method

Purpose

The purpose of this study was to investigate the in vivo elution kinetics of gentamicin from bone cement by assessing antibiotic levels in the urine.

Methods

Urinary samples of 35 patients who had undergone primary total hip arthroplasty were collected post-operatively. Gentamicin concentrations were analysed using the fluorescence polarisation immunoassay technique.

Results

The mean duration of urinary gentamicin release in all cases was 43 days (range 13–95). There was still detectable gentamicin at the final collection in 20 % (7/35) of cases, and in these cases, the mean gentamicin release was 71 days.

Conclusions

From the assessment of urinary gentamicin, we were able to demonstrate the biphasic gentamicin elution from bone cement. In addition, there were detectable concentrations of the antibiotic from the urinary samples for prolonged periods of up to two to six months. Our study indicates that the assessment of urinary antibiotics can offer a non-invasive method of monitoring the in vivo release kinetics of antibiotics from bone cement.     

The effect of polymethyl methacrylate on latex-free surgical gloves

In the current medical environment of increased awareness about latex sensitivity, more patients are presenting with known latex allergy. One such patient presented to us for total knee arthroplasty. During this procedure, we noticed holes in our latex-free surgical gloves when polymethyl methacrylate (PMMA) was being handled. Through subsequent testing of different brands of latex-free surgical gloves with various brands of bone-cement, we found that Allergard latex-free surgical gloves are destroyed by contact with PMMA. Biogel Neotech and Duraprene latex-free gloves show no such destruction. These results indicate that Allergard gloves should not be used in procedures in which bone-cement is employed. Biogel Neotech and Duraprene latex-free gloves are an acceptable alternative.     

Intravenous polymethyl methacrylate after cemented hemiarthroplasty of the hip

Current cementing techniques used during hip arthroplasty aim to maximize the bond at the bone-cement interface in an effort to increase the longevity of the prosthesis. To accomplish this, one must generate high intramedullary pressures, which are known to be associated with complications such as cement implantation syndrome. We record a rare complication following cement pressurization of a hip hemiarthroplasty that resulted in intravenous polymethyl methacrylate (PMMA). This complication however, is not associated with a significant morbidity or mortality, but it is important to identify and distinguish from a femoral cortical defect, which can be created during surgery.     

Histopathological evaluation of polymethyl methacrylate as an embolic agent

Summary Polymethyl methacrylate (PMMA) microspheres were used as an embolic agent to reduce the vascularity in eight patients with intracranial vascular tumours. Post embolization angiograms showed 30–60% reduction in the vascularity of the tumours. No patient developed any neurological complications in the immediate post-embolization period. These eight patients subsequently underwent surgery for the removal of their tumours. During surgery there was minimal blood loss and a good plane of cleavage was obtained between the tumour and the adjacent brain. The surgical specimens were examined histopathologically for the effects of PMMA. PMMA microspheres, in contrast to other cyano-acrylates — Isobutyl-2-cyano-acrylate (IBCA) — did not elicit either inflammatory reaction or mural angionecrosis within the wall of the embolised vessels. The histopathological studies suggest that PMMA microspheres are an inert material and can be used as an adjunct in the management of intracranial vascular tumours.     

Addition of gentamicine to polymethyl methacrylate for therapy of infectious bone diseases. Expeimental in vivo tests]

In experimental in vivo tests the therapeutic effect of Gentamicin added to Palacos is detected in a standardized osteomyelitic infection caused by Staph. aureus haemolyticus. The number of germ populations is reduced significantly by the antibiotic which is released in a microbiologically active concentration. On the other hand the number of germ populations in control trials (without adding an antibiotic) is remaining on a high level. During the time of the tests the appearance of other bacterial is registrated.     

Long-term efficacy of biomodeled polymethyl methacrylate implants for orbitofacial defects

OBJECTIVE: To report the long-term efficacy of custom polymethyl methacrylate implants using high-resolution computed tomographic modeling in the reconstruction of complex orbitofacial defects secondary to trauma. METHODS: Nine patients with complex orbitofacial bone defects after trauma were evaluated for this retrospective, nonrandomized, noncomparative study. All the patients underwent reconstruction using custom, heat-cured polymethyl methacrylate implants. Patients were followed up postoperatively and evaluated for complications. RESULTS: Nine consecutive patients (5 men and 4 women) aged 28 to 63 years who underwent surgical reconstruction using prefabricated, heat-cured polymethyl methacrylate implants were included in the study. The interval between injury and presentation ranged from 1 month to 40 years. There were no significant complications, including infection, extrusion, or displacement of the implant. In all of the patients, wound healing was uneventful, with antibiotic drugs administered perioperatively. Mean follow-up was 4.3 years from the first visit (range, 6 months to 10 years). CONCLUSIONS: Computed tomographic biomodeled, prefabricated, heat-cured polymethyl methacrylate implants are well tolerated in the long term. Their advantages include customized design, long-term biocompatibility, and excellent aesthetic results.     

Macrophage exposure to polymethyl methacrylate leads to mediator release and injury

To understand further the role of macrophages in the loosening of cemented arthroplasty, several in vitro effects of polymethyl methacrylate (PMMA) particle exposure in these cells were studied. The kinetics of arachidonic acid and derived inflammatory mediator release was characterized following macrophage exposure to either PMMA or control polystyrene particles. Temporal release of radiolabeled products by [14C]arachidonate-labeled cells was determined by sequential scintillation counting. Significant dose-dependent release of arachidonic acid mediators by macrophages was observed within half an hour of exposure to either PMMA or styrene particles. Unexposed control cells incubated in media alone did not release detectable amounts of radiolabeled products. The leakage of intracellular lactate dehydrogenase (LDH), a marker of cell injury, was detected spectrophotometrically 4 h following exposure to PMMA but not styrene. PMMA-induced LDH release was dose dependent. In contrast, polystyrene exposure failed to increase LDH release above unexposed control cells. These in vitro studies reveal that macrophages rapidly released arachidonic acid and derived inflammatory mediators in response to both PMMA and styrene particles. However, cells exposed to PMMA are lethally damaged, as reflected by the subsequent leakage of their intracellular LDH. We propose that a similar sequence of events may occur when macrophages encounter PMMA particles at the bone-cement interface. This is characteristic of a foreign body granulomatous response.     

Contamination of polyethylene cups with polymethyl methacrylate particles: an experimental study

The articulating surfaces of 6 ultra-high molecular weight polyethylene cups were exposed to curing polymethyl methacrylate (PMMA) bone-cement and examined with scanning electron microscopy and laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS). Three of the cups were exposed to blood and bone-cement, and the rest were exposed to bone-cement only. After removal of the bone-cement bulk, PMMA particles were found and identified in all 6 cups. The particles were verified by identifying zirconium with energy-dispersive x-ray fluorescence spectroscopy in 5 cups and with LA-ICPMS in 1 cup. The degree of surface contamination was estimated with LA-ICPMS. The number of zirconium-containing particles detected was on average 10 to 20/mm2. PMMA bone-cement left in polyethylene cups during polymerization can contaminate the articulating surface with adherent PMMA particles.