Properties of nanofiller-loaded poly (methyl methacrylate) bone cement composites for orthopedic applications: a review.

There is a large body of literature on new generations of poly (methyl methacrylate) bone cements that address one or more of the material's shortcomings. Among these are cements in which one of the constituents is a nanofiller, such as nano-sized barium sulfate, multiwalled carbon nanotubes, natural nanoclay, mesoporous silica nanoparticles, or oleic acid-capped silver nanoparticles. This article is a review of the literature on the properties of these nanofiller-loaded bone cements (NFLBCs). Some key characteristics of the literature are that (1) in a number of studies, clinically relevant properties were determined, examples being maximum exotherm, setting time, fatigue life, and compressive modulus; (2) in some studies, properties were not determined in accordance with approved bone cement testing specifications, an example being fatigue life; and (3) there are a number of clinically relevant properties that were not determined in any of the studies, examples being fatigue crack propagation rate and dynamic compression creep life. These observations, as well as other considerations, suggest 12 areas for future study, such as determination of dynamic creep compliance (using nanoindentation), determination of compressive fatigue life for cements to be used in vertebral compression fracture augmentation, elucidation of toughening mechanism(s) in each type of NFLBC, and conducting well-designed clinical trials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 105B: 1260-1284, 2017.

Evaluation of two novel aluminum-free, zinc-based glass polyalkenoate cements as alternatives to PMMA bone cement for use in vertebroplasty and balloon kyphoplasty.

Vertebroplasty (VP) and balloon kyphoplasty (BKP) are now widely used for treating patients in whom the pain due to vertebral compression fractures is severe and has proved to be refractory to conservative treatment. These procedures involve percutaneous delivery of a bolus of an injectable bone cement either directly to the fractured vertebral body, VB (VP) or to a void created in it by an inflatable bone tamp (BKP). Thus, the cement is a vital component of both procedures. In the vast majority of VPs and BKPs, a poly(methyl methacrylate) (PMMA) bone cement is used. This material has many shortcomings, notably lack of bioactivity and very limited resorbability. Thus, there is room for alternative cements. We report here on two variants of a novel, bioactive, Al-free, Zn-based glass polyalkenoate cement (Zn-GPC), and how their properties compare to those of an injectable PMMA bone cement (SIMPL) that is widely used in VP and BKP. The properties determined were injectability, radiopacity, uniaxial compressive strength, and biaxial flexural modulus. In addition, we compared the compression fatigue lives of a validated synthetic osteoporotic VB model (a polyurethane foam cube with an 8 mm-diameter through-thickness cylindrical hole), at 0-2300 N and 3 Hz, when the hole was filled with each of the three cements. A critical review of the results suggests that the performance of each of the Zn-GPCs is comparable to that of SIMPL; thus, the former cements merit further study with a view to being alternatives to an injectable PMMA cement for use in VP and BKP.

Percutaneous vertebroplasty and kyphoplasty for the stand-alone augmentation of osteoporosis-induced vertebral compression fractures: present status and future directions.

Enormous research efforts are being expended on two minimally invasive procedures: percutaneous vertebroplasty (VP) and kyphoplasty (KP). The present report, which is a detailed critical review of VP and KP that emphasizes their biomechanics aspects, is divided into six parts. In the first two parts, succinct descriptions are given of osteoporosis-induced vertebral body (VB) compression fractures as the underlying pathology to be treated with VP and KP, the theory of VP and KP, and the techniques used in performing these procedures. Concerns about VP and KP, such as the high radiation exposure burden that may be imposed on both patient and medical personnel and extravasation of the injectable bone cement, are discussed in the third part. Detailed discussions of fourteen issues/questions, such as the extent to which VP or KP affects various biomechanical measures of the augmented VB and those adjacent to it and the appropriate volume of the cement to use, are presented in the fourth part. Ideas for future research, such as development of a new generation of injectable bone cements and identification of an appropriate animal model, are covered in the fifth part. The final section contains a summary of the most salient points/observations made in the report.

Alendronate in bone cement: fatigue life degraded by liquid, not by powder.

Bisphosphonates have the potential to reduce osteolysis, a phenomenon that has been postulated to play a key role in aseptic loosening of total joint replacements. Bisphosphonates may contribute to the in vivo longevity of total joint replacements. Some authors have suggested there are decreases in flexural strength and flexural modulus of the cured cement when a liquid form of disodium pamidronate is added to a commercially available acrylic bone cement (Palacos R). We proposed that it is comparatively easier to blend a bisphosphonate in powder form into an acrylic bone cement than it is when the drug is in liquid form; and that the cement's fatigue life is decreased when the bisphosphonate is added in liquid rather than in solid form. The bisphosphonate and bone cement used were alendronate sodium and Cemex XL, respectively. The fatigue tests were done using phosphate buffered saline solution at 37 degrees +/- 1 degrees C. The data supported both hypotheses. Our findings should guide orthopaedic surgeons when using bisphosphonate-impregnated acrylic bone cements in total joint replacements. Bisphosphonates are endogenous pyrophosphate analogs in which a carbon atom replaces the central oxygen atom. These therapeutic agents may be classified into nitrogen and non-nitrogen containing types. Some examples are alendronate, pamidronate, ibandronate, risedronate, etidronate, clodronate, and zoledronate. There are many targets and mechanisms of action of this family of drugs, therefore making them efficacious against diverse clinical conditions such as osteoporosis, periprosthetic bone loss subsequent to total joint replacement, tumor cell proliferation, apoptosis and angiogenesis, Charcot neuroarthropathy, rheumatoid arthritis, ankylosing spondylitis and spondyloarthropathies, and arterial calcification. It has been proposed that some bisphosphonates are effective against the mechanisms that have been suggested as being implicated in aseptic loosening of total joint replacements, these being osteoclast-mediated bone resorption and wear particle-induced osteolysis. A meta-analysis of randomized controlled trials showed that alendronate and pamidronate had beneficial effects maintaining periprosthetic bone for as much as 1 year after a total joint replacement.

Injectable bone cements for use in vertebroplasty and kyphoplasty: state-of-the-art review.

Vertebroplasty (VP) and kyphoplasty (KP) are minimally invasive surgical procedures that have recently been introduced for the medical management of osteoporosis-induced vertebral compression fractures. The aim of VP is to stabilize the fractured vertebral body, while the goals of KP are to stabilize the fractured vertebral body and to restore its height to as near its prefracture level as possible. Both procedures involve injection of the setting dough of an injectable bone cement (IBC) into the fractured vertebral body, thereby highlighting the indispensable role that the IBC plays. Although there is a very large literature on IBCs, no detailed critical review of it has been published. Such a review is the subject of the present work, which is in seven parts. The review opens with a succinct introduction to VP and KP. The topics covered in the parts that follow are: (1) a listing of the 18 most desirable properties of an IBC (e.g., easy injectability, high radiopacity, and a resorption rate that is neither too high nor too low); (2) descriptions of the four classes of IBCs (calcium phosphates, acrylic bone cements, calcium sulfates, and composites); (3) concerns that have been raised with regard to the use of IBCs (such as the potential for thermal necrosis of tissue at the peri-augmentation site, when an acrylic bone cement is used); (4) explicative summaries of the main findings of literature studies on the influence of nine factors (such as powder particle size, powder-to-liquid ratio, and the method used to mix the powder and the liquid) on the values of various properties of IBCs; (5) explicative summaries of the main findings of literature studies on five fundamental matters, such as the aging mechanism of the powder, the thermokinetics of a setting dough, and the influence of the type of IBC used on various ex vivo biomechanical performance measures of VP- and KP-augmented vertebral bodies; and (6) descriptions of topics in six areas for future research, such as the determination of an overall index of the fatigue performance of an IBC and the development of internationally recognized standardized testing protocols to employ when a synthetic cancellous bone void model is used in the rapid in vitro screening of IBCs. The review ends with a summary of the most salient points and observations made.

Effect of an accelerated aging protocol on viscoelastic properties of UHMWPE.

The values of two viscoelastic properties (storage modulus and loss angle) of four sets of ultra-high-molecular-weight polyethylene specimens were obtained. Two sets comprised specimens that had been sterilized (using gamma radiation in air or ethylene oxide gas) while the other two sets comprised specimens that were sterilized and then exposed to an accelerated aging protocol that, in the literature, has been proposed as simulating 5 years of real-time shelf aging. An analysis of the present results from the four specimen sets and those obtained, in a previous study by the present author, on specimens machined from real-time shelf aged tibial inserts suggests that the claim made for the accelerated aging protocol may be conservative.