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Vertebral compression fractures are caused by many factors including trauma and osteoporosis. Osteoporosis induced fractures are a result of loss in bone mass and quality that weaken the vertebral body. Vertebroplasty and kyphoplasty, involving cement augmentation of fractured vertebrae, show promise in restoring vertebral mechanical properties. Some complications however, are reported due to the performance characteristics of commercially available bone cements. In this study, the biomechanical performance characteristics of two novel composite (PMMA-CaP) bone cements were studied using an anatomically accurate human cadaveric vertebroplasty model. The study involves mechanical testing on two functional cadaveric spinal unit (2FSU) segments which include monotonic compression and cyclical fatigue tests, treatment by direct cement injection, and microscopic visualization of sectioned vertebrae. The 2FSU segments were fractured, treated, and mechanically tested to investigate the stability provided by two novel bone cements; using readily available commercial acrylic cement as a control. Segment height and stiffness were tracked during the study to establish biomechanical performance. The 2FSU segments were successfully stabilized with all three cement groups. Stiffness values were restored to initial levels following fatigue loading. Cement interdigitation was observed with all cement groups. This study demonstrates efficient reinforcement of the fractured vertebrae through stiffness restoration. The pre-mixed composite cements were comparable to the commercial cement in their performance and interdigitative ability, thus holding promise for future clinical use. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:2067-2074, 2017., (© 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)

There is a growing body of the literature on new cement formulations that address the shortcomings of PMMA bone cements approved for use in vertebroplasty (VP) and balloon kyphoplasty (BKP). The present study is a contribution to these efforts by further characterization of two pre-mixed CaP filler-reinforced PMMA bone cements intended for VP; namely, PMMA-HA and PMMA-brushite cements. Each of these cements showed acceptable levels of various properties determined in porcine vertebral bodies. These properties included radiographic contrast, maximum exotherm temperature setting time, cement extravasation, stiffness change after fatigue loading, change of VB height after fracture following fatigue loading, and interdigitation. Each property value was comparable to or better than that for a PMMA bone cement approved for use in BKP. Thus, the results for the composite bone cements are promising., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Purpose of Review: To discuss recent advances in percutaneous minimally invasive vertebral augmentation techniques used in the treatment of osteolytic and osteoporotic compression fractures., Recent Findings: Recent data have shown that outcomes in patients with vertebral compression fractures treated with vertebral augmentation techniques have been encouraging. Several studies demonstrated the positive effects of vertebral augmentation on maintenance of postoperative pain reduction at long-term follow-up. There is more evidence on the relationship between vertebral augmentation and adjacent segment vertebral compression fractures. In addition, the literature verifies that good outcomes can be expected in patients with spinal metastases and multiple myeloma., Summary: The incidence of symptomatic vertebral compression fractures is on the rise. For those patients with severe pain or progressive collapse due to osteoporotic or osteolytic vertebral compression fractures, early vertebral augmentation affords excellent early pain relief, early return to function, and restores and maintains sagittal alignment.

Kyphoplasty is an effective surgical treatment for the pain and deformity that can accompany vertebral compression fractures. In certain cases, however, defects or clefts in the vertebral body result either from the original fracture or from expansion of inflatable bone tamps (IBTs). Through such a defect, cement may extrude into the epidural space, paraspinal soft tissues, or disc space. In addition, by virtue of the dynamic nature of certain fracture configurations, the height restored by inflation of the bone tamps may be lost once the tamps are removed for cement placement, despite patient positioning. In our modification of the kyphoplasty technique, we use 2 cement applications to minimize potential extravertebral cement extravasation and maintain the height restoration achieved with the IBTs. After 0.75 to 1.5 cm(3) of cement is deposited, the IBTs are reinserted into the fracture and inflated until the cement cures. Once the cement is cured, the IBTs are again deflated and removed, leaving a cement shell that seals the cracks and supports the endplates. Then, another batch of cement is mixed and is used to fill the cavities, as in the standard technique. Results for our first 21 patients show a mean correction of more than 6 degrees of kyphosis and no cement leaks into the spinal canal. We believe that this modification of the kyphoplasty technique is effective and safe for certain fractures.

Study Design: Prospective study of patients who underwent single or multilevel kyphoplasty for vertebral fractures., Objective: To quantify the radiation exposure to the surgeon and to the patient during kyphoplasty, and also to provide a procedural algorithm that effectively minimizes the radiation exposure to the surgeon during any fluoroscopic-guided procedure., Summary of Background Data: Spine surgeons who perform minimally invasive procedures often employ fluoroscopy for intraoperative navigation., Methods: Twenty-seven patients were enrolled. Two fluoroscopes (1 anterior/posterior and 1 lateral) were used for localization, navigation, and monitoring cement flow. All surgeons wore thyroid shields and lead aprons. The dose of radiation exposure was measured by dosimeter badges. One badge was attached to each patient. The surgeons wore 3 badges: under the thyroid shield (protected), under the lead apron over the left chest (protected), and outside the lead apron over the left chest (unprotected). A thermoluminescent ring dosimeter was worn on the right hand for 18 cases, and on the left hand for 9 cases., Results: The exposure time was 5.7+/-2.0 minutes/vertebra for a single level (n=10), 3.9+/-0.8 minutes/vertebra for a 2 level (n=9), 2.9+/-1.2 minutes/vertebra for a 3 level kypholasty (n=8). The exposure time of single level kyphoplasy was significantly different from that of multilevel kyphoplasy (2 level, P=0.040; 3 level, P=0.002). Surgeon exposure as measured by the protected dosimeter was less than the minimum reportable dose (<0.010 mSv). Exposure as measured by the unprotected dosimeter, which is equivalent to deep whole body exposure was 0.248+/-0.170 mSv/vertebra. The eye exposure was 0.271+/-0.200 mSv/vertebra, and the shallow exposure (hand/skin) was 0.273+/-0.200 mSv/vertebra. The hand exposure was 1.744+/-1.173 mSv/vertebra., Conclusions: Without eye or hand protection, the total radiation exposure dose to these areas would exceed the occupational exposure limit after 300 cases per year. Surgeons should wear lead lined glasses and keep their hands out of the radiation beam.

Purpose of Review: Osteoporosis is a disorder characterized by decreased bone density, disruption of trabecular architecture, and increased susceptibility to fractures. There are approximately 700,000 vertebral body compression fractures in the United States each year with approximately 70,000 of these resulting in hospitalization, with an average hospital stay per patient of eight days. Osteolytic lesions of the spine are also a growing problem, affecting as many as 70% of patients with metastatic disease or multiple myeloma. Tumor-induced osteolysis may lead to pain, dysfunction, and ultimately vertebral collapse. If left untreated, vertebral body compression fractures occur with progressive kyphosis over multiple levels, cord compromise, and intractable pain. The purpose of this review is to discuss recent advances in percutaneous minimally invasive vertebral augmentation techniques used in the treatment of compression fractures., Recent Findings: Recent data have shown that outcomes in patients with vertebral compression fractures have been encouraging. Several studies have demonstrated the positive effects of vertebral augmentation on restoration of vertebral height and sagittal alignment. There is more evidence on the relationship between vertebral augmentation and adjacent segment vertebral compression fractures. A large series demonstrated promising results in patients with metastases and multiple myeloma., Summary: More studies are needed to assess the long-term effectiveness of early vertebral augmentation in the treatment of compression fractures. Early vertebral augmentation has, however, shown excellent early pain relief in those with severe pain or progressive collapse, up to a period of two years after its implementation.

Calcium phosphate fillers have been shown to increase cement osteoconductivity, but have caused drawbacks in cement properties. Hydroxyapatite and Brushite were introduced in an acrylic two-solution cement at varying concentrations. Novel composite bone cements were developed and characterized using rheology, injectability, and mechanical tests. It was hypothesized that the ample swelling time allowed by the premixed two-solution cement would enable thorough dispersion of the additives in the solutions, resulting in no detrimental effects after polymerization. The addition of Hydroxyapatite and Brushite both caused an increase in cement viscosity; however, these cements exhibited high shear-thinning, which facilitated injection. In gel point studies, the composite cements showed no detectable change in gel point time compared to an all-acrylic control cement. Hydroxyapatite and Brushite composite cements were observed to have high mechanical strengths even at high loads of calcium phosphate fillers. These cements showed an average compressive strength of 85 MPa and flexural strength of 65 MPa. A calcium phosphate-containing cement exhibiting a combination of high viscosity, pseudoplasticity and high mechanical strength can provide the essential bioactivity factor for osseointegration without sacrificing load-bearing capability. [ABSTRACT FROM AUTHOR]

Abstract: Over 700,000 osteoporotic compression fractures occur each year in the United States, twice the number of hip fractures. These vertebral fractures, most of which occur in the elderly, represent significant personal and societal burdens. Percutaneous vertebroplasty (PVP) is a minimally invasive method that involves the percutaneous injection of polymethylmethacrylate (PMMA) into a collapsed vertebral body to stabilize the vertebra. Kyphoplasty is an advanced minimally invasive technique with a number of potential advantages over PVP, including lower risk of cement extravasation and better restoration of vertebral body height and spinal biomechanics. The filling materials used for both these techniques require good biocompatibility, good biomechanical strength and stiffness, and good radiopacity for the fluoroscopy guided procedures. New filler materials (synthetic bone substitutes, e.g., composite resin materials, calcium phosphate or calcium sulfate cements) in addition to new PMMA formulations are now available for clinical use. In this review paper, we will focus on the issues and characteristics of these filler materials as they pertain to vertebral augmentation procedures. [Copyright &y& Elsevier]