The biomechanics of vertebroplasty in multiple myeloma and metastatic bladder cancer: a preliminary cadaveric investigation

Augmentation of failed human vertebrae with critical un-contained lytic defect restores their structural competence under functional loading: An experimental study

BACKGROUND

Lytic spinal lesions reduce vertebral strength and may result in their fracture. Vertebral augmentation is employed clinically to provide mechanical stability and pain relief for vertebrae with lytic lesions. However, little is known about its efficacy in strengthening fractured vertebrae containing lytic metastasis.

METHODS

Eighteen unembalmed human lumbar vertebrae, having simulated uncontained lytic defects and tested to failure in a prior study, were augmented using a transpedicular approach and re-tested to failure using a wedge fracture model. Axial and moment based strength and stiffness parameters were used to quantify the effect of augmentation on the structural response of the failed vertebrae. Effects of cement volume, bone mineral density and vertebral geometry on the change in structural response were investigated.

FINDINGS

Augmentation increased the failed lytic vertebral strength [compression: 85% (P<0.001), flexion: 80% (P<0.001), anterior-posterior shear: 95%, P<0.001)] and stiffness [(40% (P<0.05), 53% (P<0.05), 45% (P<0.05)]. Cement volume correlated with the compressive strength (r(2)=0.47, P<0.05) and anterior-posterior shear strength (r(2)=0.52, P<0.05) and stiffness (r(2)=0.45, P<0.05). Neither the geometry of the failed vertebrae nor its pre-fracture bone mineral density correlated with the volume of cement.

INTERPRETATION

Vertebral augmentation is effective in bolstering the failed lytic vertebrae compressive and axial structural competence, showing strength estimates up to 50-90% of historical values of osteoporotic vertebrae without lytic defects. This modest increase suggests that lytic vertebrae undergo a high degree of structural damage at failure, with strength only partially restored by vertebral augmentation. The positive effect of cement volume is self-limiting due to extravasation.

Application of percutaneous vertebroplasty in the treatment of multiple thoracic metastases

The present study aimed to explore the clinical implications of percutaneous vertebroplasty (PVP) in the treatment of multiple thoracic metastases. A total of 104 involved vertebrae of 28 patients with multiple thoracic metastases underwent PVP and the injection of bone cement. The pain relief rate and activity of daily life were assessed, and the morphological changes of the involved vertebral bodies and the invasiveness of the intraspinal tumor were also observed at 1 week, and 3, 6 and 12 months post-surgery, respectively. The pain relief rate increased at each time-point following PVP. The quality of life scores were also significantly higher than the pre-operative scores. After 12 months of follow-up, the post-operative heights of the anterior border, center and posterior border of the vertebral bodies were not noted to be statistically different from those prior to PVP (P>0.05). The present study concluded that PVP has a good analgesic effect on multiple thoracic metastases. PVP not only improves the quality of life of patients significantly, but also prevents further vertebral collapse and the invasiveness of intraspinal tumors, avoiding the nerve dysfunction caused by spinal cord compression.

Effect of the metastatic defect on the structural response and failure process of human vertebrae: an experimental study

BACKGROUND

Pathologic vertebral fractures are associated with intractable pain, loss of function and high morbidity in patients with metastatic spine disease. However, the failure mechanisms of vertebrae with lytic defects and the failed vertebrae's ability to retain load carrying capacity remain unclear.

METHODS

Eighteen human thoracic and lumbar vertebrae with simulated uncontained bone defects were tested under compression-bending loads to failure. Failure was defined as 50% reduction in vertebral body height. The vertebrae were allowed to recover under load and re-tested to failure using the initial criteria. Repeated measure ANOVA was used to test for changes in strength and stiffness parameters.

FINDINGS

Vertebral failure occurred via buckling and fracture of the cortex around the defect, followed by collapse of the defect region. Compared to the intact vertebrae, the failed vertebrae exhibited a significant loss in compressive strength (59%, p<0.001), stiffness (53%, p<0.05) and flexion (70%, p<0.01) strength. Significant reduction in anterior-posterior shear (strength (63%, p<0.01) and stiffness (67%, p<0.01)) and lateral bending strength (134%, p<0.05) were similarly recorded. In the intact vertebrae, apart from flexion strength (r(2)=0.63), both compressive and anterior-posterior shear strengths were weakly correlated with their stiffness parameters (r(2)=0.24 and r(2)=0.31). By contrast, in the failed vertebrae, these parameters were strongly correlated, (r(2)=0.91, r(2)=0.86, and r(2)=0.92, p<0.001 respectively).

INTERPRETATION

Failure of the vertebral cortex at the defect site dominated the initiation and progression of vertebral failure with the vertebrae failing via a consolidation process of the vertebral bone. Once failed, the vertebrae showed remarkable loss of load carrying capacity.

Vertebral compression fracture risk after stereotactic body radiotherapy for spinal metastases

Object

The aim of this study was to identify potential risk factors for and determine the rate of vertebral compression fracture (VCF) after intensity-modulated, near-simultaneous, CT image–guided stereotactic body radiotherapy (SBRT) for spinal metastases.

Methods

The study group consisted of 123 vertebral bodies (VBs) in 93 patients enrolled in prospective protocols for metastatic disease. Data from these patients were retrospectively analyzed. Stereotactic body radiotherapy consisted of 1, 3, or 5 fractions for overall median doses of 18, 27, and 30 Gy, respectively. Magnetic resonance imaging studies, obtained at baseline and at each follow-up, were evaluated for VCFs, tumor involvement, and radiographic progression. Self-reported average pain levels were scored based on the 11-point (0–10) Brief Pain Inventory both at baseline and at follow-up. Obesity was defined as a body mass index ≥ 30.

Results

The median imaging follow-up was 14.9 months (range 1–71 months). Twenty-five new or progressing fractures (20%) were identified, and the median time to progression was 3 months after SBRT. The most common histologies included renal cancer (36 VBs, 10 fractures, 10 tumor progressions), breast cancer (20 VBs, 0 fractures, 5 tumor progressions), thyroid cancer (14 VBs, 1 fracture, 2 tumor progressions), non–small cell lung cancer (13 VBs, 3 fractures, 3 tumor progressions), and sarcoma (9 VBs, 2 fractures, 2 tumor progressions). Fifteen VBs were treated with kyphoplasty or vertebroplasty after SBRT, with 5 procedures done for preexisting VCFs. Tumor progression was noted in 32 locations (26%) with 5 months' median time to progression. At the time of noted fracture progression there was a trend toward higher average pain scores but no significant change in the median value. Univariate logistic regression showed that an age > 55 years (HR 6.05, 95% CI 2.1–17.47), a preexisting fracture (HR 5.05, 95% CI 1.94–13.16), baseline pain and narcotic use before SBRT (pain: HR 1.31, 95% CI 1.06–1.62; narcotic: HR 2.98, 95% CI 1.17–7.56) and after SBRT (pain: HR 1.34, 95% CI 1.06–1.70; narcotic: HR 3.63, 95% CI 1.41–9.29) were statistically significant predictors of fracture progression. On multivariate analysis an age > 55 years (HR 10.66, 95% CI 2.81–40.36), a preexisting fracture (HR 9.17, 95% CI 2.31–36.43), and baseline pain (HR 1.41, 95% CI 1.05–1.9) were found to be significant risks, whereas obesity (HR 0.02, 95% CI 0–0.2) was protective.

Conclusions

Stereotactic body radiotherapy is associated with a significant risk (20%) of VCF. Risk factors for VCF include an age > 55 years, a preexisting fracture, and baseline pain. These risk factors may aid in the selection of which spinal SBRT patients should be considered for prophylactic vertebral stabilization or augmentation procedures. Clinical trial registration no.: NCT00508443.

Strategy for bone metastases treatment in patients with impending cord compression or vertebral fractures: a pilot study

Impending spinal cord compression and vertebral fractures are considered contraindications for radionuclide bone pain palliation therapy. However, most of the patients with widespread bone metastases already have weakened vertebral segments that may be broken. Therefore, local field external-beam radiotherapy or percutaneous vertebroplasty (VP) should be considered to improve the patient's quality of life and to institute subsequent appropriate treatment, including radionuclide therapy for bone pain palliation. The objective of this study was to develop a strategy for an effective treatment of bone metastases in patients with widespread bone metastases and intolerable pain, associated with impending cord compression or vertebral fractures. Eleven patients (5 females and 6 males, aged 32-62 years; mean age 53.8 ± 2.7 years) with multiple skeletal metastases from carcinomas of prostate (n = 3), breast (n = 3) and lung (n = 5) were studied. Their mean pain score measured on a visual analogue scale of 10 was found to be 8.64 ± 0.15 (range 8-9) and the mean number of levels with impending cord compression or vertebral fracture was 2.64 ± 0.34 (range 1-4). All patients underwent vertebroplasty and after 3-7 days received Sm-153 ethylene diamine tetra methylene phosphonic acid (EDTMP) therapy. Sm-153 EDTMP was administered according to the recommended standard bone palliation dose of 37 MBq/kg body weight. Whole body (WB) bone scan, computed tomography and magnetic resonance imaging (MRI) were performed before and after treatment in all patients. Pain relief due to stabilization of vertebrae after VP occurred within the first 12 hours (mean 4.8 ± 1.2 hours; range 0.5-12 hours), and the mean pain score was reduced to 4.36 ± 0.39 (range 2-6). Subsequent to Sm-153 EDTMP treatment, further pain relief occurred after 3.91 ± 0.39 days (range 2-6 days) and the pain score decreased to 0.55 ± 0.21 (range 0-2). The responses to treatment were found to be statistically significant (P < 0.0001). Based on the results on this limited patient population, we conclude that spinal stabilization using VP in patients with widespread bone metastases and impending cord compression is an effective way to decrease disability with pain and to facilitate subsequent systemic palliation of painful skeletal metastases by Sm-153 EDTMP therapy.

Vertebroplasty in multiple myeloma with osteolysis or fracture of the posterior vertebral wall. Usefulness of a delayed cement injection

AIM

The goal of this study was to specifically address the incidence of dorsal leakage when performing vertebroplasty in patients with posterior wall osteolysis or fracture, by using a delayed injection of cement with the aim of increasing its viscosity.

MATERIALS AND METHODS

We prospectively reviewed the records of 24 patients (13 women, 11 men; age range 42-67 years; mean age 54.7) with diagnosis of multiple myeloma (MM) who underwent 34 vertebroplasties between January 2007 and January 2010 for painful osteolytic localization of MM with dorsal cortical osteolysis or fracture. All vertebroplasties were performed with an 8 min delay, which was half of the allotted injecting time given for the chosen cement. In 11 cases there were fractures involving the posterior wall, in 1 case with dorsal fragment dislocation, and in 33 cases there was dorsal cortical osteolysis. All of the patients showed no response to standard treatments such as radiotherapy, chemotherapy, and analgesic treatments.

RESULTS

Technical success was achieved in all cases. In 20 patients, we treated only one high-risk vertebral lesion, in six patients we treated two segments, and in one patient we treated three segments. All patients experienced improvement in symptoms after the procedure as demonstrated by improved visual analogue scores (VAS) and performance status (PS) and decreased doses of analgesic. There was a dorsal leakage in 2/34 (5.8%) treated vertebral bodies in which an epidural space tumor extension was also diagnosed, without increasing neurological symptoms after the intervention.

CONCLUSION

From these results vertebroplasty with delayed injection of cement is safe and effective in the treatment of vertebral localization of myeloma with osteolysis or fracture of the posterior vertebral wall.

Percutaneous vertebral augmentation in metastatic disease: state of the art

Improvements in diagnosis and treatment have prolonged cancer survival, with a consequent increase in the incidence of spinal metastases and vertebral compression fractures with associated axial pain, progressive radiculomyelopathy, and mechanical instability. Pain relief in malignant vertebral compression fractures is key to achieving a better quality of life in patients under palliative care. The gold standard for pain relief is nonsteroidal anti-inflammatory drugs and opioids. Nonresponsive cases are then treated with radiotherapy, which may require 2-4 weeks to take effect and in most cases does not provide complete pain relief. Percutaneous vertebroplasty and percutaneous kyphoplasty can in particular give relief in patients with vertebral body compression fractures that do not cause neurological deficits but severely compromise quality of life because of intractable pain.

Percutaneous vertebroplasty to treat painful myelomatous vertebral deposits-long-term efficacy outcomes

Developed for benign conditions including osteoporotic fractures and haemangiomas, vertebroplasty has since been employed in neoplastic lesions, including myeloma. Advances in myeloma treatments, yielding improved survival times, have led to an increasing need for effective therapies that improve quality of life. The first randomised trials of vertebroplasty to treat painful osteoporotic crush fractures have cast doubt of its benefit over a placebo procedure, with a proposed rationale that fracture healing over time may account for the non-superiority of the results. However, these findings cannot be extrapolated to myeloma where the pathology is one of progressive bony destruction coupled with failure of new bone formation. In this paper, we present the outcome data for myeloma patients treated at our tertiary referral centre over a 5-year period, focusing on both subjective and objective measures of efficacy and safety. Records were reviewed to extract pain score, function and analgesia pre/post-procedure. Where possible, patients were then contacted directly and asked to assess their benefit by grading change in pain score, analgesia use and mobility. Performance status was assessed using the Eastern Cooperative Oncology Group scale. Of the 26 patients treated for painful thoraco-lumbar lesions, 77% reported improved pain score (P < 0.003). Analgesia reduction, better mobility and improved performance status were also seen. Our data support the consideration of vertebroplasty as a first-line treatment for painful myelomatous vertebral disease. Prospective randomised studies are now required to further define its role.

Bone cement deposition patterns with plasma-mediated radio-frequency ablation and cement augmentation for advanced metastatic spine lesions

BACKGROUND AND PURPOSE

Combining percutaneous plasma-mediated radio-frequency (pmRF) ablation with vertebral body augmentation offers an alternative treatment to surgical intervention options for advanced metastatic spinal lesions and is particularly useful for cases with cortical destruction and/or epidural extension. This study evaluates bone cement deposition patterns and extravasation in treated vertebral bodies in relation to the metastatic lesion after using this combined approach.

MATERIALS AND METHODS

Retrospective assessments of CT images performed before/after the procedures were evaluated in 37 patients (44 levels) with advanced metastatic lesions. A void was created in the anterior portion of the tumor-infiltrated vertebral body by using a bipolar plasma-mediated radio-frequency-based wand, followed by deposition of bone cement. Pain measured by visual analog scale score was recorded preprocedure and 2-4 weeks afterward.

RESULTS

In 19 (43%) levels, 90%-100% of the cement was deposited in the anterior two thirds of the vertebral body. In 34 levels (77%), 75% or more of the cement was deposited in the anterior two thirds of the vertebral body. In 13/15 (86%) levels with posterior lesions, cement was deposited anterior to the lesion. No extravasation was observed in 13 levels (29.5%). Two clinically insignificant incidences of epidural extravasation were noted. Pain relief after the procedure was reported by 25/28 (89.5%) patients with available data.

CONCLUSIONS

pmRF ablation may allow greater cement-deposition control, increasing the likelihood of successfully stabilizing the anterior two thirds of the vertebral body. This combined technique appeared particularly useful in cases with posteriorly located lesions. The incidence of cement extravasation was relatively high but clinically insignificant.