Image-guided percutaneous vertebra augmentation procedures can sufficiently treat pain and offer consolidation in cases of osteoporotic, metastatic and acute stable traumatic fractures
Georgia Tsoumakidou
Julien Garnon
Afshin Gangi
Department of Interventional Radiology, University Hospital of Strasbourg, France
Email: [email protected]
Spinal vertebra compression fractures (VCF) are an important cause of severe debilitating back pain, adversely affecting quality of life, physical function, psychosocial performance and survival.1,2 Its diverse aetiologies encompass osteoporosis, neoplasms, osteonecrosis and trauma. In 2010, 5.2 million non-traumatic fractures were expected in the 12 industrialised countries studied, of which 2.8 million were at the hip or spine.3 The lifetime risk of VCF is 16% for women and 5% for men and the incidence of osteoporotic fractures is anticipated to increase 4-fold worldwide in the next 50 years.4
In addition, patients with VCF have a 23% risk of mortality compared to age matched controls without VCF. This is primarily related to compromised pulmonary function as a result of thoracic as well as lumbar fractures.5 The quality of life of osteoporotic women showed significantly worse values for the women with VCF compared to those without.6
In 1987 Galibert and Deramond performed the first percutaneous vertebroplasty for the treatment of aggressive vertebral haemangiomas.7 Since then, a new era has evolved and novel percutaneous treatments have been added in the medical armamentarium. The treatment of VCFs has largely moved from conservative (bed rest, narcotic analgesics, bisphosphonates, back-bracing) to percutaneous vertebral augmentation procedures.
Fig. 1: Multiple level vertebroplasty. The vertebroplasty needles are positioned under fluoroscopic guidance using a transpedicular and costo-vertebra approach for the lumbar and thoracic level, respectively.
Vertebral augmentation procedures
Vertebral augmentation procedures (VAP) consist of several techniques used to treat VCFs. They are mainly performed by interventional radiologists under high quality image guidance. They aim to consolidate the fracture and, when possible, achieve height restoration.
Percutaneous vertebroplasty (PVP) involves injection of radio-opaque bone cement into a partially collapsed vertebral body, in an effort to provide pain relief and stability. The exact mechanism of pain relief remains unclear. Proposed theories include more favourable biomechanics after cement strengthening, chemical toxicity and exothermic effect of cement polymerisation on nerve endings.
Percutaneous kyphoplasty (PKP) is used to restore vertebral body height. Balloons are insufflated inside the vertebra body in an attempt to correct the height loss. The balloons are then removed and bone cement is injected.
Percutaneous vertebral body stenting (PVBS) and other supplemental implant techniques include the placement of expandable scaffolds or other bone implant systems, inserted before the injection of the bone cement. The stent (self-expandable nitinol system) is inserted in order to preserve the height restoration and impede the secondary loss of vertebral body height encountered with PKP after balloon deflation. Once the stent is fully expanded cement is injected for further bone consolidation.
The primary indications for VAP are8:
Painful acute osteoporotic VCFs refractory to medical treatment
Failure of medical therapy is defined as minimal or no pain relief with the administration of physician prescribed analgesics for three weeks, or achievement of adequate pain relief with only narcotic dosages that induce excessive intolerable sedation, confusion or constipation. The 3-week delay depends on the patient status-risk of immobilisation. Intervention within days can be considered in patients at high risk for decubitus complications like deep vein thrombosis, pneumonia and decubitus ulcer.
Cases of avascular vertebra necrosis (Kummel’s disease) can also be addressed with vertebroplasty. Pain control and bone consolidation in the above cases can be achieved by simply filling the osteonecrotic cavity with bone cement.
Asymptomatic VCFs or chronic healed VCF are not indications for VAPs. Furthermore, the VAPs should not be used as prophylaxis treatment in severe osteoporotic patients.
Pathologic painful VCFs
VCFs due to extensive osteolysis, malignant infiltration (by multiple myeloma, lymphoma) are excellent indications. VAP are used in a palliative setting and aim to treat pain and achieve bone consolidation. Though kyphoplasty has also been proposed for the treatment of pathologic fractures, a simple vertebroplasty is usually sufficient and less invasive. If multiple lesions are present it is of utmost importance to define the painful levels before treatment.
If necessary, VAP can be combined with percutaneous tumour ablation. Should there be any canal extension and neurologic impairment, the VAPs are contraindicated and the patient should be addressed for neurosurgical and/or radiotherapy evaluation.
Painful vertebrae due to benign bone tumours
Painful vertebrae due to benign tumours, like aggressive haemangioma, giant cell tumour and aneurysmal bone cysts, can be addressed with VAPs. If the haemangioma presents with an extra-osseous extension, some kind of decompression procedure (that is, sclerotherapy or arterial embolisation) is needed before cement consolidation.
Acute stable traumatic VCF (A1 and A3 Magerl Classification)
This is another indication for VAPs. For fractures less than 10–14 days old, in relatively young patients and with local kyphotic angle >15°, kyphoplasty or stentoplasty should be preferred over vertebroplasty. In such cases correction of the spinal column deformity is desired and both kyphoplasty and stentoplasty have proved to achieve better vertebra height restoration. In the rest of the cases (fractures in old patients with local kyphotic angle <15°), a simple vertebroplasty is a better choice, as it may be equally effective in providing pain relief and is less invasive.
Lastly, all VAPs can be used in combination with posterior surgical stabilisation when vertebral body or pedicle reinforcement is needed.
Fig. 2: (a) Patient with acute painful vertebra compression fractures on the L1 and L2 level.
(b) Two-level vertebroplasty was performed under sedation using a unilateral transpedicular approach.
(c, d, e) Cement distribution was satisfactory on immediate post-intervention control with no evidence of cement leakage.
Preoperative clinical and imaging work-up
The radiologist arranges a pre-procedural consultation with the patient in order to evaluate the origin degree of pain and discuss the intended benefits, complications and success rate of the procedure.
Preoperative MRI (with Sagittal T1W and STIR sequences) is a must in all patients, as it provides information regarding the age and healing status of the fracture, can help differentiate benign from malignant infiltration and infection, and exclude other causes of back pain (that is, facet arthropathy, spinal canal stenosis, disc herniation).
Furthermore, MRI can detect some occult vertebral fractures that are not seen on X-rays. Bone scintigraphy can be used instead, in patients contraindicated for MRI (presence of metallic implants, pacemaker, claustrophobia).
Should there be any doubt regarding the integrity of the posterior vertebral wall and the stability of the fracture (for example, in patients with ankylosing spondylitis), a limited CT scan through the concerned level(s) is performed.
Technical considerations
If less than three VCFs are to be treated, the procedure can be performed under local anaesthesia and conscious sedation. General anaesthesia is used for longer, multi-level procedures.
Vertebroplasty needles are hollow, straight needles of 10–14G calibre that are tapped into position using a sterile surgical hammer. The needle trajectory inside the vertebral body is different according to the spinal level. For the thoracic and lumbar level the intercostovertebral and transpedicular approach are the most safe. For simple vertebroplasty the unilateral approach is usually sufficient. On the contrary, for bilateral fractures treated with kyphoplasty or stentoplasty a bilateral approach is used, to restore both sides of the collapsed endplate.
Single or biplane fluoroscopy is sufficient for needle placement in almost all cases of middle/lower thoracic and lumbar VAP. For sacral fractures, upper thoracic and cervical fractures combined CT and C-arm fluoroscopy is needed.
Fig. 3: (a) 30 year old male patient with acute traumatic L1 compression fracture. (b) Two stents were positioned in order to achieve height restoration. (c) The stents were subsequently filled with cement. Note the height restoration between the pre- and post-stentoplasty images (>4mm).
Cement injection
Specially designed bone cements exist and can be safely used for the VAPs. The most commonly used bone cement is based on the polymerisation of methyl-methacrylate monomers to poly-methyl-methacrylate (PMMA) polymers. A dough of bone cement is carefully injected either directly into the fractured vertebra body or into the cavity created by the inflation of the inflatable balloon tamp.
The injection is done under continuous lateral fluoroscopy to detect any epidural leakage early and intermittent AP screening to rule out lateral leaks and to check the cement distribution. The injection is stopped when the anterior two-thirds of the vertebral body are filled and the cement is homogenously distributed in between the lateral borders of the vertebral body and the endplates.
The volume of the cement injected depends on the size of the vertebrae and its consistency. In patients with osteoporosis or haemangioma, 2.5–8ml of cement provides optimal filling of the vertebra and achieves both consolidation and pain relief. In tumoral disease where the aim of PVP is to relief excruciating pain, smaller volumes are usually sufficient.
Complications
Published data has placed the symptomatic complication rates of PVP in osteoporotic fractures at 2.2–3.9%9 and in malignant at <11.5%.10 The main complications include cement leakage, infection (<1%), fracture of ribs, posterior elements or pedicle (<1%). Cement leakage is often asymptomatic, but if present in the neural foramina or epidural space it can lead to radiculopathy and paraplegia, as a result of nerve root and cord compression, respectively. Cord compression is a serious complication and requires urgent neurosurgical decompression to prevent neurological sequelae. Cement leakage into the perivertebral venous plexus can embolise distally into the lungs.
The risk of collapse of the adjacent vertebral bodies still remains a controversial topic, despite the numerous conducted clinical and biomechanical in vitro studies. The VERTOS II open-labelled randomised controlled clinical trial showed that there is no increase in the incidence of new VCF post-PVP nor increase in the risk of an adjacent vertebral body fracture11 compared to conservative treatment. Taking existing evidence into account, we believe that the benefits provided by PVP outweigh the possible risk of adjacent VCF post-PVP, and this should be made clear to the patient when taking consent.
Outcome
For osteoporotic fractures, the efficacy of PVP has been shown in several studies. The VERTOS II trial compared PVP with conservative therapy for acute VCF (less than six weeks of symptoms) and found improvement in pain for the PVP group (significant difference in the Visual Analogue Scale (VAS) between baseline and one month being –5·2 (95% CI –5·88 to –4·72) after PVP and –2·7 (–3·22 to –1·98) after conservative treatment).11 This effect is sustained up to a year.
There is also improvement in pain related disability and reduced need for analgesia. A few years before the VERTOS II trial, two published double blind randomised control trials (PVP versus sham procedure).12,13 had concluded that PVP was not superior to placebo and naturally led to intense debate.
A detailed evaluation of the controversy that ensued is out of the scope of this article but of primary concern were the inclusion of patients with chronic fractures (up to one year of pain) and the lack of constant preprocedural MRI. We believe that PVP provides good pain relief in the majority of cases in carefully chosen patients. At the time of publication, the VERTOS IV trial is still ongoing. It aims to recruit 180 patients with acute local back pain (less than six weeks) with MRI evidence of fracture, to compare pain relief after PVP against a sham intervention.
PVP for malignant spinal disease has also been shown to improve pain and disability. In their prospective study of PVP in myeloma and metastatic spinal disease, Chew et al. reported a decrease in VAS of 2.8 points.14
Results are also very satisfactory for the kyphoplasty and stentoplasty procedures. There is clear evidence that cement extravasation is less frequent for kyphoplasty than for PVP,15 probably due to lower cement injection pressure following balloon cavity creation. Most studies also favour kyphoplasty and stentoplasty for height restoration and kyphotic angle correction.
Conclusion
A new era has evolved in the treatment of vertebra compression fractures. The image-guided percutaneous VAPs can sufficiently treat pain and offer bone consolidation in cases of osteoporotic, metastatic and stable acute traumatic VCFs. The presence of pain, the age and aetiology of the fracture play a definite role to patient recruitment and the choice of the technique to be used.
A simple vertebroplasty is performed in routine cases of osteoporotic VCFs in elderly patients; it provides rapid pain relief, early ambulation and rehabilitation. Kyphoplasty and stentoplasty mainly have a role in selected cases whereby restoration of height is of utmost importance; that is, acute kyphotic fractures in relatively young patients. A multidisciplinary team approach is the key to the success, ensuring good patient selection, postprocedural care and follow-up, while minimising complications.
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