Balloon kyphoplasty: an evidence-based analysis.

OBJECTIVE

To review the evidence on the effectiveness and cost-effectiveness of balloon kyphoplasty for the treatment of vertebral compression fractures (VCFs).

CLINICAL NEED

Vertebral compression fractures are one of the most common types of osteoporotic fractures. They can lead to chronic pain and spinal deformity. They are caused when the vertebral body (the thick block of bone at the front of each vertebra) is too weak to support the loads of activities of daily living. Spinal deformity due to a collapsed vertebral body can substantially affect the quality of life of elderly people, who are especially at risk for osteoporotic fractures due to decreasing bone mass with age. A population-based study across 12 European centres recently found that VCFs have a negative impact on health-related quality of life. Complications associated with VCFs are pulmonary dysfunction, eating disorders, loss of independence, and mental status change due to pain and the use of medications. Osteoporotic VCFs also are associated with a higher rate of death. VCFs affect an estimated 25% of women over age 50 years and 40% of women over age 80 years. Only about 30% of these fractures are diagnosed in clinical practice. A Canadian multicentre osteoporosis study reported on the prevalence of vertebral deformity in Canada in people over 50 years of age. To define the limit of normality, they plotted a normal distribution, including mean and standard deviations (SDs) derived from a reference population without any deformity. They reported a prevalence rate of 23.5% in women and a rate of 21.5% in men, using 3 SDs from the mean as the limit of normality. When they used 4 SDs, the prevalence was 9.3% and 7.3%, respectively. They also found the prevalence of vertebral deformity increased with age. For people older than 80 years of age, the prevalence for women and men was 45% and 36%, respectively, using 3 SDs as the limit of normality. About 85% of VCFs are due to primary osteoporosis. Secondary osteoporosis and neoplasms account for the remaining 15%. A VCF is operationally defined as a reduction in vertebral body height of at least 20% from the initial measurement. It is considered mild if the reduction in height is between 20% and 25%; moderate, if it is between 25% and 40%; and severs, if it is more than 40%. The most frequently fractured locations are the third-lower part of the thorax and the superior lumbar levels. The cervical vertebrae and the upper third of the thorax are rarely involved. Traditionally, bed rest, medication, and bracing are used to treat painful VCFs. However, anti-inflammatory and narcotic medications are often poorly tolerated by the elderly and may harm the gastrointestinal tract. Bed rest and inactivity may accelerate bone loss, and bracing may restrict diaphragmatic movement. Furthermore, medical treatment does not treat the fracture in a way that ameliorates the pain and spinal deformity. Over the past decade, the injection of bone cement through the skin into a fractured vertebral body has been used to treat VCFs. The goal of cement injection is to reduce pain by stabilizing the fracture. The secondary indication of these procedures is management of painful vertebral fractures caused by benign or malignant neoplasms (e.g., hemangioma, multiple myeloma, and metastatic cancer).

THE TECHNOLOGY

Balloon kyphoplasty is a modified vertebroplasty technique. It is a minimally invasive procedure that aims to relieve pain, restore vertebral height, and correct kyphosis. During this procedure, an inflatable bone tamp is inserted into the collapsed vertebral body. Once inflated, the balloon elevates the end plates and thereby restores the height of the vertebral body. The balloon is deflated and removed, and the space is filled with bone cement. Creating a space in the vertebral body enables the application of more viscous cement and at a much lower pressure than is needed for vertebroplasty. This may result in less cement leakage and fewer complications. Balloons typically are inserted bilaterally, into each fractured vertebral body. Kyphoplasty usually is done under general anesthesia in about 1.5 hours. Patients typically are observed for only a few hours after the surgery, but some may require an overnight hospital stay. Health Canada has licensed KyphX Xpander Inflatable Bone Tamp (Kyphon Inc., Sunnyvale, CA), for kyphoplasty in patients with VCFs. KyphX is the only commercially available device for percutaneous kyphoplasty. The KyphX kit uses a series of bone filler device tubes. Each bone filler device must be loaded manually with cement. The cement is injected into the cavity by pressing an inner stylet. In the United States, the Food and Drug Administration cleared the KyphX Inflatable Bone Tamp for marketing in July 1998. CE (Conformité European) marketing was obtained in February 2000 for the reduction of fracture and/or creation of a void in cancellous bone.

REVIEW STRATEGY

The aim of this literature review was to evaluate the safety and effectiveness of balloon kyphoplasty in the treatment of painful VCFs. INAHTA, Cochrane CCTR (formerly Cochrane Controlled Trials Register), and DSR were searched for health technology assessment reports. In addition, MEDLINE, EMBASE, and MEDLINE In-Process & Other Non-Indexed Citations were searched from January 1, 2000 to September 21, 2004. The search was limited to English-language articles and human studies. The positive end points selected for this assessment were as follows: Reduction in pain scoresReduction in vertebral height lossReduction in kyphotic (Cobb) angleImprovement in quality of life scoresThe search did not yield any health technology assessments on balloon kyphoplasty. The search yielded 152 citations, including those for review articles. No randomized controlled trials (RCTs) on balloon kyphoplasty were identified. All of the published studies were either prospective cohort studies or retrospective studies with no controls. Eleven studies (all case series) met the inclusion criteria. There was also a comparative study published in German that had been translated into English.

SUMMARY OF FINDINGS

The results of the 1 comparative study (level 3a evidence) that was included in this review showed that, compared with conservative medical care, balloon kyphoplasty significantly improved patient outcomes. Patients who had balloon kyphoplasty reported a significant reduction in pain that was maintained throughout follow-up (6 months), whereas pain scores did not change in the control group. Patients in the balloon kyphoplasty group did not need pain medication after 3 days. In the control group, about one-half of the patients needed more pain medication in the first 4 weeks after the procedure. After 6 weeks, 82% of the patients in the control group were still taking pain medication regularly. Adjacent fractures were more frequent in the control group than in the balloon kyphoplasty group. The case series reported on several important clinical outcomes. Pain: Four studies on osteoporosis patients and 1 study on patients with multiple myeloma/primary cancers used the Visual Analogue Scale (VAS) to measure pain before and after balloon kyphoplasty. All of these studies reported that patients had significantly less pain after the procedure. This was maintained during follow-up. Two other studies on patients with osteoporosis also used the VAS to measure pain and found a significant improvement in pain scores; however, they did not provide follow-up data. Vertebral body height: All 5 studies that assessed vertebral body height in patients with osteoporosis reported a significant improvement in vertebral body height after balloon kyphoplasty. One study had 1-year follow-up data for 26 patients. Vertebral body height was significantly better at 6 months and 1 year for both the anterior and midline measurements. Two studies reported that vertebral body height was restored significantly after balloon kyphoplasty for patients with multiple myeloma or metastatic disease. In another study, the researchers reported complete height restoration in 9% of patients, a mean 56% height restoration in 60% of patients, and no appreciable height restoration in 31% of the patients who received balloon kyphoplasty. Kyphosis correction: Four studies that assessed Cobb angle before and after balloon kyphoplasty in patients with osteoporosis found a significant reduction in degree of kyphosis after the procedure. In these studies, the differences between preoperative and postoperative Cobb angles were 3.4°, 7°, 8.8°, and 9.9°. Only 1 study investigated kyphosis correction in patients with multiple myeloma or metastatic disease. The authors reported a significant improvement (5.2°) in local kyphosis. Quality of life: Four studies used the Short Form 36 (SF-36) Health Survey Questionnaire to measure the quality of life in patients with osteoporosis after they had balloon kyphoplasty. A significant improvement in most of the domains of the SF-36 (bodily pain, social functioning, vitality, physical functioning, mental health, and role functioning) was observed in 2 studies. One study found that general health declined, although not significantly, and another found that role emotional declined. Both studies that used the Oswestry Disability Index found that patients had a better quality of life after balloon kyphoplasty. In one study, this improvement was statistically significant. In another study, researchers found that quality of life after kyphoplasty improved significantly, as measured with the Roland-Morris Disability Questionnaire. Yet another study used a quality of life questionnaire and found that 62% of the patients that had balloon kyphoplasty had returned to normal activities, whereas 2 patients had reduced mobility. (ABSTRACT TRUNCATED)