Applied Radiology

Percutaneous vertebroplasty is a minimally invasive, fluoro-scopicallyguided procedure used in the treatment of painful verte-bral body compressionfractures. Originally developed in France, ¹ it has gainedacceptance in the United States over the past 6 years, primarily as a therapyfor painful osteoporotic compression fractures unresponsive to medicalregimens. ² Currently, the major teachers, researchers, andpracti-tioners of vertebroplasty are radiologists; however, recent interestfrom orthopedic surgeons and neurosurgeons has spurred attempts to claim it asa "surgical" procedure, necessitating an operating room and generalanesthesia. The purpose of this article is to stimulate interest invertebroplasty among radiologists by familiarizing them with all aspects ofthis new procedure, including indications, risks, tech-nical aspects, andoutcomes.

Introduction

Each year, more than 700,000 verte-bral body fractures, secondary toosteo-porosis, are diagnosed in the U.S. population, that result in 115,000hospi-tal admissions. The lifetime risk of a vertebral body compressionfracture is 16% for women and 5% for men; and the incidence of osteoporoticfractures is anticipated to increase four-fold world-wide in the next 50 years. ³ Other causes of painful compression fractures include malignantinvolvement of the spinal column (metastases, myeloma, and lymphoma),hemangioma, and vertebral osteonecrosis. In addition to pain, spinal columninstability may also be present.

Approximately 84% of vertebral body compression fractures are asso-ciatedwith pain, leaving patients bed-ridden and dependent on analgesics. Bone lossis accelerated by immobilization, thus compounding the prob-lem. In addition,these disabled indi-viduals are more susceptible to pneumonia, deep venousthrombosis, and pulmonary embolism. In most patients, the pain lasts an averageof 4 to 6 weeks. However, there is a sub-group of affected persons in whom thepain persists for months or never fully subsides. Patients with fractures havebeen shown to be more dependent in activities of daily living (ADLs), andsuffer from weight loss, decreased exercise tolerance, and depression. ⁴

Regardless of etiology, treatment for compression fractures has been largelyconservative and directed toward pain control, usually consisting of narcoticanalgesia, bedrest, and back bracing. For osteoporosis, current preventativedrug regimens, including hormonal replacement therapy, biphosphonates, andcalcitonin, often are not prescribed until the disease has been diagnosed bythe presence of a fracture.

In recent years, several reports of dramatic pain relief following thepercutaneous injection of an acrylic "cement," polymethylmethacrylate(PMMA), into osteoporotic or neo-plastic compression fractures have beenpublished. ^1,2,5-10 In the late 1980s, Galibert and colleagues 1described "percutaneous vertebroplasty" in the treatment ofcompression fractures associated with hemangiomas and metastatic disease. Theprocedure involved the percutaneous puncture of the fractured vertebral body,followed by injection of PMMA to provide bone augmentation and prevent fur-thercollapse. The "internal casting" of the trabecular fractures resultedin pain relief and vertebral stabilization, allowing patients to mobilizequickly and reducing their need for narcotics.

Patient selection criteria

Patients considered for vertebro-plasty are those experiencing moderate tosevere pain from a radiologically confirmed compression fracture that isunresponsive to best medical therapy, as determined by the referring physician. ² Associated major disability, such as inability to walk or performADLs, is almost always present. In our experi-ence, the patients who bestrespond to treatment are those with fractures <12 months in age with a mildto moderate degree of collapse. Fractures older than 12 months that showincreased uptake on a bone scan or recent further col-lapse often respond aswell. Long-standing fractures, multiple fractures, and vertebra plana,particularly when associated with kyphosis and facet hypertrophy, are lesslikely to show improvement.

On examination, point tenderness on palpation over the spinous process ofthe affected vertebrae is common. Many patients complain of pain that radiatesalong the corresponding der-matome, but any focal neurological deficits needcomplete evaluation to exclude burst fracture, significant retro-pulsedfragment, infection, or other pathology, such as a herniated disc. Thisinformation is obtained easily with computed tomography (CT) and/or magneticresonance (MR) imaging. MR has the advantage of demonstrating edema associatedwith acute or suba-cute fractures, which is particularly helpful in a patientwith multiple frac-tures of uncertain age. Bone scanning is also useful indetermining active frac-tures, but hyperacute fractures may give a falsenegative response. In addi-tion, severe facet disease may appear as vertebralbody uptake if SPECT scan-ning is not performed.

There are other selective indica-tions for vertebroplasty, such asnon-traumatic unstable fractures involving the anterior column only, whereante-rior wedging of the vertebral body occurs in the upright position. ⁸ Another indication is for reinforce-ment of an affected vertebraprior to a posterior surgical stabilization proce-dure. Occasionally,prophylactic reinforcement of adjacent osteoporotic vertebral bodies before anintradiscal fusion procedure is requested.

Treatable pathologies include osteo-porosis (both steroid-induced andage-related), myeloma, metastatic disease, and hemangioma of the vertebralbody. Relative contraindications include spinal canal compromise >20% byretropulsed fragments, >90% vertebral body col-lapse, back pain for >1year, and tumor extension into the epidural space. Absolute contraindicationsfor ver-tebroplasty include: patients clearly improving on medical therapy;osteo-myelitis; uncorrected coagulopathy; or as prophylaxis in osteopenicpatients with no evidence of fracture and no planned surgical procedure.

Technical aspects

Vertebroplasty is performed in a standard angiography suite under ster-ileconditions, ² although in some instances the needle is placed underCT guidance. ⁹ Using a biplane fluo-roscopy unit, if one isavailable, will decrease the procedure time. Poor quality C-arms are to beavoided as the image quality is usually too poor for adequate visualization ofthe required landmarks and cement flow.

The patient is placed in the prone position on the angiography table andattached to the appropriate physio-logic monitoring devices. Continuousmonitoring and dedicated nursing support during the procedure are absolutelynecessary. Conscious seda-tion using fentanyl and midazolam is sufficient formost patients, although those in severe pain may require gen-eral anesthesia.

The pedicle to be punctured is iso-lated under anterioposterior (AP) andlateral fluoroscopy, and the skin is marked. After sterile preparation of thepuncture site, the skin, soft tissues, and periosteum of the targeted pedicleare anesthetized using 7 to 10 mL of 0.25% bupivicaine. ² A small,horizon-tal skin incision is made, and a stan-dard 11G bone biopsy needle isadvanced under fluoroscopic guidance into the vertebral body via thetranspediculate approach (figure 1). A 13G needle may be used for small or thinpedicles. Frequent visual checks under AP and lateral fluoroscopy ensure thatthe needle path remains within the pedicle and not outside of it. The tip ispositioned in the anterior one-third of the vertebral body on the lateralprojection. On the AP view, the needle should take a lateral to medial course,with the tip ultimately posi-tioned in the mid-hemivertebra to mid-line. Thecloser to the midline, the more likely the cement will be distrib-utedthroughout the entire vertebra, making a contralateral puncture unnec-essary.This midline position can be achieved by initially targeting the pedi-cle inthe more oblique "scotty-dog" position (figure 2), but the pedicularcortex may be less obvious.

Once in position, needle tip location outside of major venous structures isconfirmed by injection of 3 to 5 mL of diluted contrast material. This"verte-brogram" outlines the trabecular space, the basivertebralplexus, and the sur-rounding internal and external epidural venous plexus. Ifthe needle tip is directly within a major vertebral vein, then it may beadvanced more anteriorly or plugged with gelfoam or a thick cement slurry.Although the consistency of cement is different from that of contrast, animage from the verte-brogram can be a useful reference when paravertebral orepidural venous filling is suspected (figure 3).

Once appropriate needle positioning is obtained, the PMMA is prepared forinjection. The polymer powder is mixed with an antibiotic powder (usuallytobramycin) and sterile, pure bar-ium sulfate (for opacification). The liq-uidmonomer is added until a material with a thin "cake-glaze"consistency is created. This material is then injected into the vertebra underfluoroscopic visualization. ² Frequent checks in both planes ensurethat the material remains within the vertebral body without migrating into thesurrounding venous plexus. If cement leaches across an endplate fracture, asmall amount of material is allowed to layer on the disc side; however, largeamounts of PMMA in the disc space may act as a wedge, resulting in fracture ofthe adja-cent body. If the injection becomes dif-ficult or cementpreferentially flows to a vein, the needle should be reposi-tioned posteriorly.Persistent venous filling is an indication to cease injec-tion, lest thematerial migrate to the inferior vena cava or azygous system with resultantpulmonary embolization. Injection is terminated when adequate filling of thevertebral body is obtained, or when the cement border reaches the posteriorquarter of the vertebral body. The contralateral hemisphere is treated in asimilar manner, if necessary (figure 4).

After the procedure, all patients are observed in the supine position for 1hour, followed by sitting or standing as tolerated. New chest or back pain, orneurological dysfunction is evaluated immediately so appropriate treatment canbe instituted. Ambulatory patients are discharged to the care of an adult. Painmedication may be taken as needed, but patients are encouraged to limit druguse so efficacy of the treatment can be determined. Patient follow-up, bydirect contact or telephone, is made within 48 hours.

Complications

The minor or transient complication rate in osteoporotic fractures is 1% to3%, and as high as 10% in metastatic lesions. ⁷ Fortunately, thepermanent complication rate for all lesions is <1%. Potential complicationsinclude migra-tion of cement into the epidural venous plexus or leakage througha fracture into the canal resulting in spinal cord or nerve-root compression;cement embolization to the lungs; fracture of the pos-terior elements orpedicles; rib fracture; hemorrhage; and infection. Ability to recognize andcare for these complica-tions, including emergency surgical support, isessential.

Complications can be avoided by appropriate patient selection, use ofout-standing fluoroscopic equipment and strict aseptic technique, properopacifi-cation of cement, fluoroscopically con-trolled injection, and awarenessof areas that may be difficult to see. If visualiza-tion of the material isinadequate, the procedure should be terminated.

Results

Review of the literature shows sev-eral small or moderate-sized series oftreated patients with good clinical out-comes, although no large seriesevalu-ating the durability of vertebroplasty has been published to date.Deramond and colleagues ⁷ reported 80 patients with rapid andcomplete pain relief in >90% of osteoporotic cases. Follow-up ranged from 1month to 10 years, with evidence of prolonged analgesic effect. We notedsimilar results, with acute pain relief in 90% of 29 treated patients, asevidenced by their verbal expression of perceived pain and anal-gesic use. 2Statistically significant differences in analgesic use and patient mobilitypre- and post-treatment has also been found in 84 patients with 159osteoporotic fractures followed for up to 3 years (ME Jensen, unpublisheddata, 1997).

The percentage of responders among patients treated for metastatic diseasemay be less than other patient groups. In Deramond and coworkers' ⁷ series of 101 patients with metastatic disease, 80% demonstratedan imme-diate significant analgesic effect and improvement in patient qualityof life. Weill and colleagues ¹⁰ treated 37 patients with 52metastatic lesions and found 73% with clear improvement, defined as a 50%decrease in narcotic dose or change to a non-narcotic med-ication, and abilityto walk. Durability of results was also positive; 73% of patients hadpersistent pain relief at 6 months and 65% at 1 year. Recurrent pain wasassociated with new metastases. One complicating factor in treatment analysiswas the concomitant use of radiation and chemotherapy in some patients, makingit difficult to ascertain the effect of each therapy upon the overall painsyndrome.

Conclusion

Percutaneous vertebroplasty is a promising new therapy in the treatment ofpainful compression fractures refractory to conservative treatment. Thisprocedure significantly reduces pain and restores mobility in the majority ofappropriate candidates, allowing patients to return to their previous qual-ityof life quickly. Radiologists are best suited to perform this procedure giventheir training in fluoroscopically guided percutaneous techniques and theirhigh-quality imaging equipment. We strongly urge that every radiology grouphave at least one physician trained to perform vertebroplasty, as demand forthis procedure is certain to grow in the next several years. AR

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