Pharmacological mechanisms underlying the efficacy of antibodies generated by a vaccine to treat oxycodone use disorder.

Therapeutic vaccines offer a viable strategy to treat opioid use disorders (OUD) complementary to current pharmacotherapies. The candidate Oxy(Gly)4-sKLH vaccine targeting oxycodone displayed pre-clinical proof of efficacy, selectivity and safety, and it is now undergoing clinical evaluation. To further support its implementation in the clinic, this study tested critical in vivo neuropsychopharmacological properties of the Oxy(Gly)4-sKLH vaccine in rats. While repeated immunizations with Oxy(Gly)4-sKLH were necessary to maintain the antibody response overtime, exposure to free oxycodone did not boost oxycodone-specific antibody levels in vaccinated rats, limiting concerns of immune-related side effects. Immunization with Oxy(Gly)4-sKLH achieved sustained antibody titers over a period of five months following initial vaccination, supporting its potential for providing long-lasting protection. In vivo studies of selectivity showed that vaccination prevented oxycodone-induced but not methadone-induced antinociception, while still preserving the opioid antagonist naloxone's pharmacological effects. Vaccination did not interfere with fentanyl-induced antinociception or fentanyl distribution to the brain. These in vivo data confirm the previously reported in vitro selectivity profile of Oxy(Gly)4-sKLH. Vaccination extended oxycodone's half-life up to 25 h compared to control. While vaccination reduced the reinforcing efficacy of oxycodone in an intravenous self-administration model, signs of toxicity were not observed. These rodent studies confirm that active immunization with Oxy(Gly)4-sKLH induces highly specific and long-lasting antibodies which are effective in decreasing the reinforcing effects of oxycodone while preserving the efficacy of medications used to treat OUD and overdose.

Formulation and Characterization of Conjugate Vaccines to Reduce Opioid Use Disorders Suitable for Pharmaceutical Manufacturing and Clinical Evaluation.

This study focused on formulating conjugate vaccines targeting oxycodone and heroin for technology transfer, good manufacturing practice (GMP), and clinical evaluation. Lead vaccines used the highly immunogenic carrier protein keyhole limpet hemocyanin (KLH), which poses formulation problems because of its size. To address this barrier to translation, an oxycodone-based hapten conjugated to GMP-grade subunit KLH (OXY-sKLH) and adsorbed on alum adjuvant was studied with regard to carbodiimide coupling reaction time, buffer composition, purification methods for conjugates, conjugate size, state of aggregation, and protein/alum ratio. Vaccine formulations were screened for post-immunization antibody levels and efficacy in reducing oxycodone distribution to the brain in rats. While larger conjugates were more immunogenic, their size prevented characterization of the haptenation ratio by standard analytical methods and sterilization by filtration. To address this issue, conjugation chemistry and vaccine formulation were optimized for maximal efficacy, and conjugate size was measured by dynamic light scattering prior to adsorption to alum. An analogous heroin vaccine (M-sKLH) was also optimized for conjugation chemistry, formulated in alum, and characterized for potency against heroin in rats. Finally, this study found that the efficacy of OXY-sKLH was preserved when co-administered with M-sKLH, supporting the proof of concept for a bivalent vaccine formulation targeting both heroin and oxycodone. This study suggests methods for addressing the unique formulation and characterization challenges posed by conjugating small molecules to sKLH while preserving vaccine efficacy.

Safety and efficacy of an oxycodone vaccine: Addressing some of the unique considerations posed by opioid abuse.

Among vaccines aimed at treating substance use disorders, those targeting opioids present several unique medication development challenges. 1) Opioid overdose is a common complication of abuse, so it is desirable for an opioid vaccine to block the toxic as well as the addictive effects of opioids. 2) It is important that an opioid vaccine not interfere with the action of opioid antagonists used to reverse opioid overdose or treat addiction. 3) Some opioids are immunosuppressive and chronic ongoing opioid use could interfere with vaccine immunogenicity. 4) Although antibody-bound oxycodone is unable to enter the brain because of its size, it might still be able to activate peripheral opioid receptors. To assess vaccine impact on opioid toxicity, rats vaccinated with oxycodone conjugated to keyhole limpet hemocyanin subunit dimer (OXY-dKLH) adsorbed to alum or controls vaccinated with dKLH were compared with regard to oxycodone-induced hotplate analgesia and oxycodone-induced respiratory depression and bradycardia. Vaccination shifted the dose-response curves to the right, representing protection, for each of these endpoints. Naloxone was equally effective in both OXY-dKLH and control groups, providing complete and rapid reversal of respiratory depression. The administration of a long-acting naltrexone formulation during vaccination did not impair vaccine immunogenicity in mice. Similarly, serum anti-oxycodone antibody titers were not altered by continuous morphine infusion during vaccination compared to opioid-naïve controls. Competitive ELISA assay showed negligible or low affinity of immune antiserum for endogenous opioids or opioid antagonists. In vitro receptor binding assays showed that antibody-bound oxycodone does not activate mu opioid receptors. These data support further study of OXY-dKLH as a potential treatment for oxycodone abuse and suggest that vaccination might also reduce the severity of oxycodone overdose.

Left-right differences in the proximal femur's strength of post-menopausal women: a multicentric finite element study.

UNLABELLED: The strength of both femurs was estimated in 198 post-menopausal women through subject-specific finite element models. Important random differences between contralateral femurs were found in a significant number of subjects, pointing to the usefulness of further studies to understand if strength-based classification of patients at risk of fracture can be affected by laterality issues. INTRODUCTION: Significant, although small, differences exist in mineral density and anatomy of contralateral proximal femurs. These differences, and their combined effect, may result in a side difference in femurs' strength. However, this has never been tested on a large sample of a homogenous population. METHODS: The strength of both femurs was estimated in 198 post-menopausal women through CT-derived finite element models, built using a validated procedure, in sideways fall conditions. The impact of the resulting asymmetry on the classification of subjects at risk of fracture was analysed. RESULTS: The small difference observed between sides (the right femur on average 4 % stronger than the left) was statistically significant but mechanically negligible. In contrast, higher random differences (absolute difference between sides with respect to mean value) were found: on average close to 15 % (compared to 9.2 % for areal bone mineral density (aBMD) alone), with high scatter among the subjects. When using a threshold-based classification, the right and left femurs were discordant up to over 20 % of cases (K always lower than 0.60) but the left femur was concordant (mean K = 0.84) with the minimum strength between right and left. CONCLUSION: Considering both femurs may be important when trying to classify subjects at risk of failure with strength estimates. Future studies including fracture assessment would be necessary to quantify the real impact.

Distinct functions of alternatively spliced isoforms encoded by zebrafish mef2ca and mef2cb.

In mammals, an array of MEF2C proteins is generated by alternative splicing (AS), yet specific functions have not been ascribed to each isoform. Teleost fish possess two MEF2C paralogues, mef2ca and mef2cb. In zebrafish, the Mef2cs function to promote cardiomyogenic differentiation and myofibrillogenesis in nascent skeletal myofibers. We found that zebrafish mef2ca and mef2cb are alternatively spliced in the coding exons 4-6 region and these splice variants differ in their biological activity. Of the two, mef2ca is more abundantly expressed in developing skeletal muscle, its activity is tuned through zebrafish development by AS. By 24hpf, we found the prevalent expression of the highly active full length protein in differentiated muscle in the somites. The splicing isoform of mef2ca that lacks exon 5 (mef2ca 4-6), encodes a protein that has 50% lower transcriptional activity, and is found mainly earlier in development, before muscle differentiation. mef2ca transcripts including exon 5 (mef2ca 4-5-6) are present early in the embryo. Over-expression of this isoform alters the expression of genes involved in early dorso-ventral patterning of the embryo such as chordin, nodal related 1 and goosecoid, and induces severe developmental defects. AS of mef2cb generates a long splicing isoform in the exon 5 region (Mef2cbL) that predominates during somitogenesis. Mef2cbL contains an evolutionarily conserved domain derived from exonization of a fragment of intron 5, which confers the ability to induce ectopic muscle in mesoderm upon over-expression of the protein. Taken together, the data show that AS is a significant regulator of Mef2c activity.

Correlative light and scanning X-ray scattering microscopy of healthy and pathologic human bone sections.

Scanning small and wide angle X-ray scattering (scanning SWAXS) experiments were performed on healthy and pathologic human bone sections. Via crystallographic tools the data were transformed into quantitative images and as such compared with circularly polarized light (CPL) microscopy images. SWAXS and CPL images allowed extracting information of the mineral nanocrystalline phase embedded, with and without preferred orientation, in the collagen fibrils, mapping local changes at sub-osteon resolution. This favorable combination has been applied for the first time to biopsies of dwarfism syndrome and Paget's disease to shed light onto the cortical structure of natural bone in healthy and pathologic sections.

A comparison between micro-CT and histology for the evaluation of cortical bone: effect of polymethylmethacrylate embedding on structural parameters.

Cortical bone microstructure is an important parameter in the evaluation of bone strength. The aim of this study was to validate the characterization of human cortical bone microarchitecture using microcomputed tomography. In order to do this, microcomputed tomography structural measurements were compared with those obtained through histological examination (the gold standard). Moreover, to calculate structural parameters, microcomputed tomography images have to be binarized with the separation between bone and nonbone structures throughout a global thresholding. As the effect of the surrounding medium on the threshold value is not clear, an easy procedure to find the global uniform threshold for a given acquisition condition is applied. This work also compared the structural parameters of microcomputed tomography cortical sample scan in air or embedded in polymethylmethacrylate; histology was used as a reference. For each acquisition condition, a fixed threshold value was found and was applied on the corresponding microcomputed tomography image for the parameters assessment. Twenty cortical bone samples were collected from human femur and tibia diaphyses. All samples were microcomputed tomography scanned in air, embedded in polymethylmethacrylate, rescanned by microcomputed tomography, examined by histology and finally compared. A good correspondence between the microcomputed tomography images and the histological sections was found. Paired comparisons in cortical porosity, Haversian canal diameter and Haversian canal separation between histological sections and microcomputed tomography cross sections, first in air and then embedded in PolyMethylMethAcrylate, were made: no significant differences were found. None of the comparisons showed significant differences for cortical porosity, Haversian canal diameter and Haversian separation over a three-dimensional volume of interest, between microcomputed tomography scans in air and with samples embedded in PolyMethylMethAcrylate. The very good correlation between bone structural measures obtained from microcomputed tomography datasets and from two-dimensional histological sections confirms that microcomputed tomography may be an efficient tool for the characterization of cortical bone microstructure. Moreover, when the corresponding threshold value for each condition is used, structural parameters determined by microcomputed tomography are not affected by the surrounding medium (PolyMethylMethAcrylate).

Quality control protocol for in vitro micro-computed tomography.

The aim of this work was to present and discuss a quality control protocol for in vitro micro-computed tomography (microCT), based on the adaptation of the quality control protocols for medical computed tomography. The importance of establishing a quality control protocol is related to the opportunity to identify problems on time comparing the microCT images acquired in different time points, and in this way to verify the performance of the device. The proposed quality control protocol was applied for a long-time monitoring period to verify the stability of the micro-tomographic system over time. The protocol proposed in this study was applied to the histomorphometric characterization of bone tissue, but it can be used on a wide range of in vitro microCT applications. Noise and uniformity tests, taken and adapted to micro-tomographic system by medical standard guidelines of quality control, were performed by the use of a water phantom. An accuracy test was designed and performed by the use of a morphometric calibrated phantom. All these tests were performed during a long-time monitoring period to control the stability of the system. Specific control charts and monitoring parameters for each test were used to represent the monthly measures collected during 20 months and an out of control condition was defined. The reference values (baseline), calculated to control the stability of micro-tomographic system over time, were calculated during acceptance/status test. During the period, no out of control conditions in noise, uniformity and accuracy tests were recorded. However, a changing condition was found in noise test, as showed by using statistical C (P < 0.01) and Kruskal-Wallis (P < 0.05) tests. In particular, a Wilcoxon rank sum test with Bonferroni correction (P < 0.0125) was applied in noise test to investigate which of the comparisons among first five acquisitions of year 2004 (group B.L.) and each group was significant (P < 0.0125). The noise showed a slight but significant increase over the years compared to baseline value; however, no out of control conditions were recorded. Nonetheless, a maintenance service to control the performance of mechanical components of microCT was required and performed.

Dependence of mechanical compressive strength on local variations in microarchitecture in cancellous bone of proximal human femur.

Human cancellous bone is a heterogeneous material. Despite this, most of the published studies report correlations between mechanical properties and morphometric parameters averaged on the whole specimen. This work investigated whether local variations in morphometric parameters were linked to the localized failure regions of cancellous bone. Additionally, it was examined whether local values of morphometric parameters can predict the ultimate stress better than the average bone volume fraction (BV/TV). Cylindrical cancellous bone specimens extracted along the primary compressive group of human femoral heads were studied. These were microCT-imaged to assess the morphometric parameters, compressed to determine the ultimate stress, and rescanned by microCT to visualize the failure region. Failure involved slightly less than half of the free height of the specimens. Significant differences were found in the morphometric parameters calculated in the failure and in the non-failure regions. The cross-sections containing minimum BV/TV values were those most often located inside the failure region (83%, p<0.001). Regression analysis confirmed that variations in BV/TV best describe variations in ultimate stress (R2=0.84) out of the averaged morphometric parameters. The prediction of ultimate stress increased when minimum or maximum values of the morphometric parameters were taken, with the highest prediction found by considering the minimum BV/TV (R2=0.95). In conclusion, due to the heterogeneity of cancellous bone, there may exist regions characterized by a different microarchitecture, where the bone is weaker and consequently is more likely to fail. These regions mostly contain minimum values in BV/TV, which were found to predict ultimate stress better than average BV/TV.

Structural parameters and mechanical strength of cancellous bone in the femoral head in osteoarthritis do not depend on age.

For normal bone, aging has been associated with a decrease of both density and failure strength, and with the development of pathologies such as osteoporosis. Conversely, it has been reported that another common disease, osteoarthritis, may alter these age-related changes in cancellous bone, suggesting that it may have a protective role against osteoporosis and the correspondent fracture risk. It was reported that in the principal compressive region of the femoral head in osteoarthritis the bone density does not depend on age. However, it is not clear if this independence on age of the cancellous bone density corresponds also to a reduced dependence on age of the strength to failure. The present work examined cancellous bone from the principal compressive region of the femoral head of 37 patients having severe osteoarthritis. The aim was (1) to investigate the dependence on age of both the structural parameters and the ultimate stress and (2) to investigate the relationships between the ultimate stress and the structural parameters. Using X-ray microcomputed tomography, three-dimensional structural parameters, such as bone volume fraction, direct trabecular thickness and structure model index were calculated. Then the specimens were compressed to failure to determine the ultimate stress. It was found that none of the investigated structural parameters did depend on age, and also the ultimate stress did not depend on age (p>0.05 for all regressions on age). In addition, the ultimate stress was significantly correlated with the structural parameters, primary with the minimum bone volume fraction and the average bone volume fraction (R(2)=0.95 and R(2)=0.84, respectively). These findings show that severe osteoarthritis or a related factor may change the age dependences of both the structural parameters and the mechanical properties usually reported for normal cancellous bone. These results suggest for this pathology to have a protective role against the age-related decrease in density, the age-related deterioration of the microarchitecture and the age-related decrease of the failure strength for the cancellous bone in the principal compressive region of the human femoral head.

MicroCT examination of human bone specimens: effects of polymethylmethacrylate embedding on structural parameters.

X-ray microtomography permits the nondestructive investigation of trabecular and cortical bone specimens without special preparation of the sample. To do a quantitative characterization, the cross-section images have to be binarized, separating bone from nonbone. For this purpose, a widely used method is uniform thresholding. However, for commonly available microtomography scanners which use a polychromatic X-ray source, it is unclear what effect the surrounding medium (e.g. air, saline solution, polymethylmethacrylate) has on the threshold value used for the binarization. In the literature an easy procedure to find the optimal uniform threshold value for a given acquisition condition is reported. By applying this procedure, the present work investigated whether a microtomography scan of trabecular bone samples in air or embedded in polymethylmethacrylate gave the same results in terms of structural parameters. The gold standard, that is, histological sections, was used as a reference. Two fixed threshold values were found, one for the microtomography scans performed in air and one for the scans with the same samples embedded in polymethylmethacrylate. These were applied on the correspondent microtomography images for the estimation of structural parameters, such as bone volume fraction, direct trabecular thickness, direct trabecular separation and structure model index. Paired comparisons were made in bone volume fraction between histological sections and microtomography cross-sections for the same bone samples scanned first in air and then embedded in polymethylmethacrylate, by which no significant differences were found. Paired comparisons were also made in bone volume fraction, direct trabecular thickness, direct trabecular separation and structure model index for the same samples over volumes of interest of 4 x 4 x 4 mm3 between microtomography scans in air and scans with the samples embedded in polymethylmethacrylate. Neither these comparisons showed significant differences. This leads to the conclusion that structural parameters estimated by microtomography for human trabecular bone samples scanned either in air or embedded in polymethylmethacrylate are not affected by the surrounding medium (i.e. presence or absence of polymethylmethacrylate), provided that the corresponding optimal threshold value is applied for each acquisition condition.

Radiopacity of tantalum-loaded acrylic bone cement.

Radiopacifying agents are commonly added to bone cements to enhance the visibility of the cement in radiography. The radiopacifiers usually employed may, however, have undesired effects on the mechanical properties of the cement. A potentially new radiopacifier is tantalum, which in the present work was evaluated in terms of radiopacity. Bone cements containing different percentages of tantalum were compared with plain bone cement as well as with formulations containing different percentages of the commonly used radiopacifier barium sulphate. The radiopacity was assessed quantitatively and qualitatively, by measuring with a digital densitometer the optical density of the cement on X-ray films, and consulting the expertise of ten orthopaedic surgeons. It was found that tantalum does present radiopacity, but not as high as barium sulphate under the specific conditions applied to this study.

A physical phantom for the calibration of three-dimensional X-ray microtomography examination.

X-ray microtomography is rapidly gaining importance as a non-destructive investigation technique, especially in the three-dimensional examination of trabecular bone. Appropriate quantitative three-dimensional parameters describing the investigated structure were introduced, such as the model-independent thickness and the structure model index. The first parameter calculates a volume-based thickness of the structure in three dimensions independent of an assumed structure type. The second parameter estimates the characteristic form of which the structure is composed, i.e. whether it is more plate-like, rod-like or even sphere-like. These parameters are now experiencing a great diffusion and are rapidly growing in importance. To measure the accuracy of these three-dimensional parameters, a physical three-dimensional phantom containing different known geometries and thicknesses, resembling those of the examined structures, is needed. Unfortunately, such particular phantoms are not commonly available and neither does a consolidated standard exist. This work describes the realization of a calibration phantom for three-dimensional X-ray microtomography examination and reports an application example using an X-ray microtomography system. The calibration phantom (external size 13 mm diameter, 23 mm height) was based on various aluminium inserts embedded in a cylinder of polymethylmethacrylate. The inserts had known geometries (wires, foils, meshes and spheres) and thicknesses (ranging from 20 microm to 1 mm). The phantom was successfully applied to an X-ray microtomography device, providing imaging of the inserted structures and calculation of three-dimensional parameters such as the model-independent thickness and the structure model index. With the indications given in the present work it is possible to design a similar phantom in a histology laboratory and to adapt it to the requested applications.

Behavior of Hylamer polyethylene in hip arthroplasty: comparison of two gamma sterilization techniques.

Hylamer polyethylene was introduced in the 1990s as an alternative to conventional polyethylene. Its chemical and physical properties, and especially its high crystallinity, were claimed to improve resistance to wear. Initially Hylamer devices were sterilized by gamma radiation in air, then the technique was changed and gamma radiation was performed in the absence of oxygen. Clinical experience has shown the early loosening of some devices made from Hylamer. The aim of this study was to ascertain whether early wear and consequent osteolysis was linked to the sterilization method. We retrospectively compared 31 patients with hip prostheses with Hylamer liners sterilized by gamma radiation in air (group 1) with 30 patients with the same prosthesis, but sterilized in the absence of oxygen (group 2). The groups were similar for sex, age, disease, head diameter and material. Mean follow-up was 84 months and no clinical signs of failure were present. Radiographic measurement revealed that wear of group 1 was significantly greater than that of group 2 (0.23 mm/year vs 0.09 mm/year, p=0.001). Periacetabular and femoral osteolysis in group 1 was significantly greater than group 2. In conclusion, the method of sterilization might have influenced the outcome of Hylamer polyethylene liners.

Comparison of asynchronous and realtime teleconsulting for orthopaedic second opinions.

We studied a teleconsulting service for second opinions in orthopaedics. Three units of the national insurance organization for accidents at work were connected to a large orthopaedic hospital in Bologna. During a 20-month study, 65 consultations were provided: 51 (78%) by asynchronous (store-and-forward) consulting and 14 (22%) by realtime videoconferencing. All the consultations made use of radiology images (radiographs, computerized tomography scans, magnetic resonance imaging scans and ultrasound scans). Video-messages and still images were commonly used to support the asynchronous consultations. More data were transmitted on average for an asynchronous teleconsultation (8 MByte) than in a videoconference (5 MByte). The average time spent by orthopaedic specialists was slightly longer in videoconferences (21 min, SD 8) than in asynchronous teleconsultations (19 min, SD 8). The clinicians confidence in their diagnosis was generally good but was lower in asynchronous consultations. The main problem affecting the telemedicine service was the lack or the low quality of the information received from the referring sites. The clinical complexity of the case and the organizational requirements were declared to be the main factors affecting the choice of consulting procedure. The study showed that the asynchronous method was preferred in the majority of cases and could be easily integrated into clinical practice, although there were some concerns about the diagnostic quality of the information transmitted.

Proton magnetic relaxation in bone marrow related to age and bone mineral density: low-resolution in vitro studies.

Detailed analysis of proton spin-spin and spin-lattice relaxation behaviors of the bone marrow in the presence of trabecular bone network was performed at low-resolution (B(0) = 0.496T) on rat vertebrae specimens deprived of spinal cord. Two groups of samples, from young and old healthy animals, were investigated before cellular necrosis had started. BMD measurements were carried out to quantify the expected age-related modifications of the trabecular bone network. 1H-MR measurements were also performed on the same samples, deprived of marrow and saturated with water, in order to control the validity of a possible interpretation of the marrow 1H-MR characteristics, in terms of marrow components, and to investigate the possible employment of these samples to study the trabecular bone network properties. We pointed out that: 1) a bimodal distribution of T(2i) and T(1i) values (distinguishing "fast" and "slow" relaxations) describes satisfactorily all the 1H-MR experimental decays; 2) age-related modifications of the trabecular bone network are marked by correlate variations of the BMD value and of the proton spin-spin relaxation rates in water saturated samples; 3) age-related modifications of marrow are underlined by variations of the average value of the "fast" T(2i) and of the "slow" T(1i) relaxation time distributions, which could be attributed to the marrow components different from the fat granules of the adipose cells. Our results suggest that studies in vitro on bone tissue, by 1H-MR techniques at low-resolution, may contribute to a better bone function characterization and, therefore, to a better clinical utilization of MRI techniques.

CCD film digitizers in clinical practice: evaluation of the main properties.

Until hospitals convert to 'filmless' radiology departments, computerized display and archival of x-ray images will necessitate devices to transform conventional X-ray films into digital images. Current methods for digitizing x-ray films include laser based and Charged Couple Device (CCD) based scanners. There is now much interest in the use of CCD devices for demanding applications, with the lower cost of ownership contributing towards the diffusion of CCD scanners. We report a study comparing the performance of three CCD based systems (an x-ray film digitizer, and two low cost flatbed scanners), looking at characteristic curve, useful optical range with respect the noise, repeatability, Modulation Transfer Function (MTF), and geometric distortion. In addition, we evaluated the potential and limitations of these devices in the clinical assessment of x-ray films. The most important weakness of CCD devices derived from the stability and the noise of CCD detectors, mostly affecting the useful optical range in the darker regions of x-ray films. Spatial resolution and geometric distortion were confirmed be the real points of strength of CCD technology. Therefore, the most appropriate system for each user depends on what type of clinical decision will be made following inspection of the digitised images.

The effect on the fatigue strength of bone cement of adding sodium fluoride.

New bone cements that include several additives are currently being investigated and tested. One such additive is sodium fluoride (NaF), which promotes bone formation, facilitating implant integration and success. The influence of NaF on the fatigue performance of the cement as used in biomedical applications was tested in this paper. In fact fatigue failure of the cement mantle is a major factor limiting the longevity of a cemented implant. An experimental bone cement with added NaF (12 wt%) was investigated. The fatigue strength of the novel bone cement was evaluated in comparison with the cement without additives; fatigue tests were conducted according to current standards. The load levels were arranged based on a validated, statistically based optimization algorithm. The curve of stress against number of load cycles and the endurance limit were obtained and compared for both formulations. The results showed that the addition of NaF (12 wt%) to polymethylmethacrylate (PMMA) bone cement does not affect the fatigue resistance of the material. Sodium fluoride can safely be added to the bone cement without altering the fatigue performance of the PMMA bone cement.