Vertebral compression fractures are a common cause of back pain, especially in the elderly. Because osteoporotic bone is less able to withstand stress, a vertebral fracture may be the first indication of osteoporosis. Patients usually have a history of antecedent trauma, although the event is often minor enough to have been forgotten. Metastases and myeloma also predispose to pathologic fracture, and there may be symptoms of pain from bony destruction even before the fracture has occurred.

Management of vertebral fractures tends to be predominantly conservative, combining bed rest, adequate analgesia, and physiotherapy. Prolonged confinement to bed, however, has its own associated problems, including bone demineralization, muscle atrophy and contractures, poor bowel motility, and pressure sores. Persistent pain despite adequate therapy also limits day-to-day activities and reduces patients' general quality of life.

Surgical treatment is seldom an option. Not only is access to the spine's anterior region limited, but inherent risks from surgery and anesthesia make the procedure unsuitable for many elderly patients. After the acute period of fracture, significant collapse of the vertebral body may result in a kyphotic deformity. Altered mechanics resulting from the deformity can cause paraspinal muscle spasm and degenerative changes in the posterior elements and facet joints. All these factors contribute to chronic pain.

Percutaneous vertebroplasty was initially developed for treating large hemangiomas and metastases in the vertebral body. The first reported case was performed in France.1 Subsequent investigations took place primarily in France and other European countries.2,3 Larger series began to be published in the mid-1990s.4,5 The first reported series from the Asia-Pacific region appeared this year.6

Vertebroplasty has now found a wider application in the treatment of osteoporotic fractures. Although the prospect of placing a large-bore needle close to the spinal cord and nerve roots may be initially daunting, it is a technically straightforward procedure. Intervention is best performed with good-quality C-arm or biplane fluoroscopic equipment, which is generally found in angiography suites. A needle, bone cement, an orthopedic mallet, and an opacifying agent will also be needed. Good understanding of skeletal imaging, proper training, and a meticulous technique are prerequisites for success.

Orthopedic surgeons, geriatricians, rheumatologists, and rehabilitation medicine physicians are the usual sources of referral from within the hospital. Factors assessed in the history include onset and duration of back pain, relation to any fall or minor trauma, current analgesic requirements, and progression of pain despite rest and rehabilitation. A clinical examination is performed to identify exact sites and levels of back pain, with neurological evaluation of the lower limbs. A quick assessment of the skin covering the back is also done, as poor skin condition may predispose the patient to infection.

Conventional radiographs can show the fracture with loss of height and/or endplate buckling. Multiple compression fractures may be present, however (Figure 1). MRI helps by demonstrating increased signal intensity, due to bone marrow edema, in acute fractures on T2 fat-saturated or short-tau inversion recovery (STIR) sequences (Figure 2). Old fractures remain low in signal on these sequences. MRI allows exclusion of significant degenerative disc disease or nerve root impingement and identifies compromise of the spinal canal, size of the pedicles, paraspinal mass, or other evidence of malignant disease.

Hematological testing for full blood count, urea/electrolytes, and coagulation are performed for all cases, as is common with any invasive radiological procedure. Group and cross-matching of blood is also done, and informed consent obtained. Absolute contraindications include evidence of active infection and coagulopathy. Vertebral body retropulsion or fracture to the posterior cortex are relative contraindications. Severe vertebral body collapse (vertebra plana) is not a contraindication.7 The patient must be able to lie prone without respiratory compromise for the duration of the procedure. Ready access to CT scanning and orthopedic consultation and management should be available, in case extravasation of cement requires emergency decompressive surgery.

TECHNICAL TIPS

Our vertebroplasty technique is essentially similar to that described by Jensen et al8 and Deramond et al.9 The patient is placed in the prone position, and blood pressure, heart rate, and oxygen saturation are monitored continuously. Sedation is achieved with intravenous fentanyl and occasionally with midazolam as well. The planned route of needle insertion is selected with biplanar C-arm fluoroscopy, which should demonstrate the pedicle clearly. A 22-gauge spinal needle is used to administer 1% lignocaine for local anesthesia to the skin and subcutaneous tissues down to the periosteum. The position and planned direction of vertebroplasty insertion can be checked with the spinal needle.

An 11-gauge vertebroplasty needle is inserted along the same path, initially by hand through the soft tissues and then through the pedicle by tapping with a small sterile orthopedic mallet. Gentle tapping allows accurate control of the needle path and direction, as compared with pushing in by hand. Care should be taken not to cross the medial cortex of the pedicle and encroach into the spinal canal. When the needle tip is within the body of the vertebra, as shown on lateral fluoroscopy, the needle is angled medially to place the tip in the midline in the anterior third of the vertebral body (Figure 3).

Core biopsy can be taken at this point if required, with the biopsy needle inserted coaxially though the vertebroplasty needle (Figure 4). We do not routinely perform venography through the vertebroplasty needle because the flow of the liquid contrast may not accurately reflect the flow of the more viscous cement. Also, residual contrast may hinder visualization of cement.10

The most commonly used cement material in vertebroplasty is polymethylmethacrylate. Activation involves mixing the liquid monomer and powder to form bone cement, which hardens in about eight to 10 minutes. Although most common cement formulations contain 10% weight/volume of barium sulphate, their radio-opacity is inadequate to allow accurate visualization of cement during administration. A sterile inert agent, either tantalum or barium sulphate, is added for increased opacification. The cement is mixed until a semisolid state is achieved. The mixture should be liquid enough to allow injection through the needle, but viscous enough to prevent intravasation into the vertebral venous plexus.

The most critical stage of the procedure occurs during injection of cement into the vertebral body (Figure 5). Continuous magnified fluoroscopic screening in the lateral position is imperative to ensure that no extravasation into the spinal canal, disc spaces, and paraspinal soft tissues occurs. Rapid disappearance of cement from the injection site may indicate that venous intravasation with embolization is taking place. The most common route is from the basivertebral vein into the lumbar veins and venous plexus, before entering the inferior vena cava.

Between 3 and 8 mL of cement can be injected, depending on the degree of collapse. Feeling some of the same batch of cement that was not injected can help assess solidification of the cement. The patient is kept in the prone position for another 15 to 20 minutes to allow the cement to harden completely. Final cement distribution should be viewed in both the anteroposterior and lateral planes and checked for adequate and symmetrical filling of the vertebral body (Figure 6). The cement should ideally also be in contact with both the superior and inferior endplates to provide support for weight bearing, particularly in the anterior third of the vertebral body. If the contralateral side is not filled optimally, the other pedicle should be punctured and the procedure repeated.

Patients who have undergone vertebroplasty should remain in the supine position for the next two to three hours. They will be allowed to sit up and move around gradually, depending on the degree of pain. Any neurological changes should be documented, and a CT scan performed if either cement leak or embolization is suspected. An overnight hospital stay may be required if the pain is not controlled or complications arise. Oral analgesia can be prescribed for local pain or soreness at the puncture site. Patients and/or their caregivers should receive instruction about physiotherapy and back exercises. Any underlying osteoporosis should be treated with appropriate biphosphonates.

INITIAL RESULTS

Most reports in the literature are descriptive studies. Case-controlled trials are understandably problematic. Pain relief from vertebroplasty can be rapid and significant, making it difficult to withhold the procedure in someone for whom it is indicated. Performing a control procedure would also entail some degree of risk with no expected benefit.

Continued follow-up of vertebroplasty patients will provide further

evidence for the procedure's utility. Studies quote figures between 73% and 97% for symptomatic relief, with good reduction or complete alleviation of pain. Rapid onset of pain relief, occurring within 24 to 48 hours after the procedure, has also been shown. To assess the change in degree of pain perceived, most studies use the visual analogue scale, using a pain score from one to 10 to indicate the degree of pain. Alternative outcome measures include change in analgesic use, change in degree of mobility, complications, and adverse events.

The overall complication rate appears to be fairly low. Mortality has been reported in only one case, and it was attributed to suspected pulmonary embolism.4 Another study reported cement pulmonary embolism.11 It is likely, however, that the complication rate has been underreported. Most complications from cement leakage have been asymptomatic. The risk of adverse effects can be reduced if adequate imaging detail on fluoroscopy is available to detect extravasation. Familiarity with the properties and behavior of the cement material will also reduce the likelihood of mishaps.

Compression fractures from osteoporosis and metastatic vertebral disease are common clinical conditions. As knowledge of and experience with vertebroplasty grow in the Asia-Pacific region, it is hoped that this procedure will relieve pain and improve quality of life for patients and those who care for them.

DR. TSOU is a registrar in the department of diagnostic radiology at Tan Tock Seng Hospital in Singapore, DR. GOH is a consultant in the department of radiology at Mount Elizabeth Hospital in Singapore, and PROF. PEH is senior consultant radiologist at Singapore General Hospital.

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