Prediction of adjacent vertebral fracture risk associated with vertebroplasty : a computer-based simulation study

Vertebrplasty involved injecting cement into a fractured vertebra to provide stabilisation. There is clinical evidence to suggest however that vertebroplasty may be assocated with a higher risk of adjacent vertebral fracture; which may be due to the change in material properties of the post-procedure vertebra modifying the transmission of mechanical stresses to adjacent vertebrae.

Development of a bovine collagen-apatitic calcium phosphate cement for potential fracture treatment through vertebroplasty

The aim of this study was to examine the potential of incorporating bovine fibres as a means of reinforcing a typically brittle apatite calcium phosphate cement for vertebroplasty. Type I collagen derived from bovine Achilles tendon was ground cryogenically to produce an average fibre length of 0.96 ± 0.55 mm and manually mixed into the powder phase of an apatite-based cement at 1, 3 or 5 wt.%. Fibre addition of up to 5 wt.% had a significant effect (P = 0.001) on the fracture toughness, which was increased by 172%. Adding =1 wt.% bovine collagen fibres did not compromise the compressive properties significantly, however, a decrease of 39-53% was demonstrated at =3 wt.% fibre loading. Adding bovine collagen to the calcium phosphate cement reduced the initial and final setting times to satisfy the clinical requirements stated for vertebroplasty. The cement viscosity increased in a linear manner (R = 0.975) with increased loading of collagen fibres, such that the injectability was found to be reduced by 83% at 5 wt.% collagen loading. This study suggests for the first time the potential application of a collagen-reinforced calcium phosphate cement as a viable option in the treatment of vertebral fractures, however, issues surrounding efficacious cement delivery need to be addressed. © 2012 Acta Materialia Inc.

Development of calcium phosphate cement for the augmentation of traumatically fractured porcine specimens using vertebroplasty

The study aim was to develop and apply an experimental technique to determine the biomechanical effect of polymethylmethacrylate (PMMA) and calcium phosphate (CaP) cement on the stiffness and strength of augmented vertebrae following traumatic fracture. Twelve burst type fractures were generated in porcine three-vertebra segments. The specimens were randomly split into two groups (n=6), imaged using microCT and tested under axial loading. The two groups of fractured specimens underwent a vertebroplasty procedure, one group was augmented with CaP cement designed and developed at Queen's University Belfast. The other group was augmented with PMMA cement (WHW Plastics, Hull, UK). The specimens were imaged and re-tested . An intact single vertebra specimen group (n=12) was also imaged and tested under axial loading. A significant decrease (p<0.01) was found between the stiffness of the fractured and intact groups, demonstrating that the fractures generated were sufficiently severe, to adversely affect mechanical behaviour. Significant increase (p<0.01) in failure load was found for the specimen group augmented with the PMMA cement compared to the pre-augmentation group, conversely, no significant increase (p<0.01) was found in the failure load of the specimens augmented with CaP cement, this is attributed to the significantly (p<0.05) lower volume of CaP cement that was successfully injected into the fracture, compared to the PMMA cement. The effect of the percentage of cement fracture fill, cement modulus on the specimen stiffness and ultimate failure load could be investigated further by using the methods developed within this study to test a more injectable CaP cement.

Biomechanics of Vertebroplasty: Effect of Cement Viscosity on Mechanical Behaviour

Vertebroplasty is a minimally invasive surgical procedure, which requires efficacious percutaneous cement delivery via a cannulated needle to restore the strength and stiffness in osteoporotic vertebral bodies. Cement viscosity is understood to influence the injectability, cohesion and cement retention within the vertebral body. Altering the liquid to powder ratio modifies the viscosity of bone cement; however, the cement viscosity-response association between cement fill and augmentation of strength and stiffness is unknown. The aim of this study was to determine the relationship between viscosity, cement fill and the potential augmentation of strength and stiffness in an open pore foam structure that was representative of osteoporotic cancellous bone using an in vitro prophylactic vertebroplasty model. The results showed a strong linear correlation between compressive strength and stiffness augmentation with percentage cement fill, the extent of which was strongly dependent on the cement viscosity. Significant forces were required to ensure maximum delivery of the high viscosity cement using a proprietary screw-driven cement delivery technology. These forces could potentially exceed the normal human physical limit. Similar trends were observed when comparing the results from this study and previously reported cadaveric and animal based in vitro models.

Ex vivo experimental model for percutaneous vertebroplasty: microCT utility

The aim of this study was to develop an ex vivo experimental animal model for percutaneous vertebroplasty, for further application in vivo to test novel bone injectable cements.

Development of a sheep vertebroplasty model for bioceramic materials assessment

Development of a sheep vertebroplasty model for bioceramic materials assessment Sheep has been widely used as an animal orthopaedic model. Although several studies report anatomic and biomechanical similarities as well as distinctions of ovine lumbar vertebrae when compared to human’s, only a few studies describe its actual use as a vertebroplasty model. Due to distinct anatomic features, sheep lumbar vertebrae pose a challenge when developing a minimally invasive procedure for vertebroplasty material testing, under conditions meant to be the most similar to clinical procedure. The present work describes the development of an appropriate surgical percutaneous vertebroplasty model in the lumbar spine of sheep, applicable in vivo, that minimizes the risk of post-surgical complications. This model was mechanically evaluated ex-vivo regarding its safety, and used to evaluate the injectability and radiopacity of two new bioceramic materials when compared to a commercial bioceramic bone substitute (Cerament™ SpineSupport). Microtomography techniques helped in the development of the model and results assessment. Under fluoroscopic guidance, a defect was created through a bilateral modified parapedicular access in the cranial hemivertebrae of 30 sheep lumbar vertebrae (L4, L5 and L6). The manually drilled defect had an average volume of 1209 ±226 mm3 and allowed the novel materials injection through a standardized injection cannula placed in one of the entrance points. Adequate defect filling was observed with all tested materials. No mechanical failure was observed under loads higher than the physiological.

Ex Vivo Model for Percutaneous Vertebroplasty

The testing of novel biomaterials for percutaneous vertebroplasty depends on suitable animal models. The aim of this study was to develop ex vivo a reproducible and feasible model of percutaneous vertebroplasty, for ulterior application in vivo. A large animal model was used (Merino sheep), due to its translational properties. Vertebroplasty was performed under tactile and fluoroscopic control, through a bilateral modified parapedicular access in lumbar vertebrae (n=12). Care was taken in order to avoid disruption of the vertebral foramen. The average defect volume was 1234±240 mm3. This mean volume ensures practical defects to test novel injectable biomaterials. 6 vertebrae were injected with a commercial cement (Cerament®, Bone Support, Sweden). Adequate defect filling was observed in all vertebrae. All vertebrae were assessed by microCT, prior to and post defect creation and after biomaterial injection. All vertebrae were mechanical tested. No mechanical failure was observed under loads higher than the physiological. Ultimately, this model is considered suitable for pre-clinical in vivo studies, mimicking clinical application.

A review of vertebroplasty for osteoporotic and malignant vertebral compression fractures

Vertebral compression fractures are a common clinical problem and the incidence of them will increase with the ageing population. Traditionally management has been conservative; however, there has been a growing trend towards vertebroplasty as an alternative therapy in patients with persisting severe pain. NICE produced guidance in 2003 recommending the procedure after 4 weeks of conservative management. Recent high-quality studies have been contradictory and there is currently a debate surrounding the role of the procedure with no agreement in the literature. We examine the evidence in both osteoporotic and malignant vertebral compression fractures; we also describe the benefits and side effects, alternative treatment options and the cost of the procedure. Finally, we recommend when vertebroplasty is most appropriately used based on the best available evidence.

Efficacy and safety of vertebroplasty for treatment of painful osteoporotic vertebral fractures: a randomised controlled trial [ACTRN012605000079640]

Background: Vertebroplasty is a promising but as yet unproven treatment for painful osteoporotic vertebral fractures. It involves radiographic-guided injection of various types of bone cement directly into the vertebral fracture site. Uncontrolled studies and two controlled quasi-experimental before-after studies comparing volunteers who were offered treatment to those who refused it, have suggested an early benefit including rapid pain relief and improved function. Conversely, several uncontrolled studies and one of the controlled before-after studies have also suggested that vertebroplasty may increase the risk of subsequent vertebral fractures, particularly in vertebrae adjacent to treated levels or if cement leakage into the adjacent disc has occurred. As yet, there are no completed randomised controlled trials of vertebroplasty for osteoporotic vertebral fractures. The aims of this participant and outcome assessor-blinded randomised placebo-controlled trial are to i) determine the short-term efficacy and safety (3 months) of vertebroplasty for alleviating pain and improving function for painful osteoporotic vertebral fractures; and ii) determine its medium to longer-term efficacy and safety, particularly the risk of further fracture over 2 years.

Design: A double-blind randomised controlled trial of 200 participants with one or two recent painful osteoporotic vertebral fractures. Participants will be stratified by duration of symptoms (< and ≥ 6 weeks), gender and treating radiologist and randomly allocated to either the treatment or placebo. Outcomes will be assessed at baseline, 1 week, 1, 3, 6, 12 and 24 months. Outcome measures include overall, night and rest pain on 10 cm visual analogue scales, quality of life measured by the Assessment of Quality of Life, Osteoporosis Quality of Life and EQ-5D questionnaires; participant perceived recovery on a 7-point ordinal scale ranging from 'a great deal worse' to 'a great deal better'; disability measured by the Roland-Morris Disability Questionnaire; timed 'Up and Go' test; and adverse effects. The presence of new fractures will be assessed by radiographs of the thoracic and lumbar spine performed at 12 and 24 months.

Discussion: The results of this trial will be of major international importance and findings will be immediately translatable into clinical practice.

Trial registration: Australian Clinical Trial Register # [ACTRN012605000079640]

A randomized trial of vertebroplasty for painful osteoporotic vertebral fractures

Background Vertebroplasty has become a common treatment for painful osteoporotic vertebral fractures, but there is limited evidence to support its use.

Methods We performed a multicenter, randomized, double-blind, placebo-controlled trial in which participants with one or two painful osteoporotic vertebral fractures that were of less than 12 months' duration and unhealed, as confirmed by magnetic resonance imaging, were randomly assigned to undergo vertebroplasty or a sham procedure. Participants were stratified according to treatment center, sex, and duration of symptoms (<6 weeks or 6 weeks). Outcomes were assessed at 1 week and at 1, 3, and 6 months. The primary outcome was overall pain (on a scale of 0 to 10, with 10 being the maximum imaginable pain) at 3 months.

Results A total of 78 participants were enrolled, and 71 (35 of 38 in the vertebroplasty group and 36 of 40 in the placebo group) completed the 6-month follow-up (91%). Vertebroplasty did not result in a significant advantage in any measured outcome at any time point. There were significant reductions in overall pain in both study groups at each follow-up assessment. At 3 months, the mean (±SD) reductions in the score for pain in the vertebroplasty and control groups were 2.6±2.9 and 1.9±3.3, respectively (adjusted between-group difference, 0.6; 95% confidence interval, –0.7 to 1.8). Similar improvements were seen in both groups with respect to pain at night and at rest, physical functioning, quality of life, and perceived improvement. Seven incident vertebral fractures (three in the vertebroplasty group and four in the placebo group) occurred during the 6-month follow-up period.

Conclusions We found no beneficial effect of vertebroplasty as compared with a sham procedure in patients with painful osteoporotic vertebral fractures, at 1 week or at 1, 3, or 6 months after treatment. (Australian New Zealand Clinical Trials Registry number, ACTRN012605000079640.)

Efficacy and safety of vertebroplasty for treatment of painful osteoporotic vertebral fractures : a randomised double-blind placebo-controlled trial

Background: Vertebroplasty has become a common treatment for painful osteoporotic vertebral fractures despite limited evidence to support its use. The primary aim of this study was to determine its short-term efficacy and safety in this patient population.

Methods: In a multicentre randomized placebo-controlled trial, participants with one or two painful osteoporotic vertebral fractures < 12 months duration confirmed active by MRI were randomly assigned, stratified by center, gender and duration of symptoms (< or ≥ 6 weeks), to receive vertebroplasty or sham treatment. Primary outcome was overall pain (0–10 scale) at 3 months. Participants, investigators (other than the interventional radiologist) and outcome assessors were blinded to treatment assignment.

Results: 78 participants were enrolled and 73 (36/38 active, 37/40 placebo, 94%) completed 3-month follow up. Vertebroplasty did not show any statistically significant advantage in any measured outcome with 95% confidence intervals indicating no plausible practically important benefits of vertebroplasty over placebo. At 1 week, 1 and 3 months, there were significant improvements in overall pain in both treatment groups (mean improvement (SD): 1.5 (2.5), 2.1 (2.8), 2.3 (2.6), and 1.7 (3.3), 2.5 (2.9), 1.9 (3.4) in the active and placebo groups respectively). Similar improvements in both groups were observed for night and rest pain, function, quality of life and perceived improvement. Eight incident clinical vertebral fractures (3 active, 5 placebo) occurred during 3-month follow up.

Conclusion: We found no evidence of a beneficial effect of vertebroplasty over sham treatment for painful osteoporotic vertebral fractures, 1 week, 1 and 3 months following treatment. [Australian Clinical Trial Register number, ACTRN012605000079640]