Osteolytic lesions of the spine are a growing problem, affecting as many as 70% of patients with metastatic disease or multiple myeloma (1,2). Although symptomatic spinal cord involvement has been estimated to occur in 18,000 patients per year (3), approximately one third of vertebral lesions are asymptomatic and discovered incidentally (4). Tumor-induced osteolysis may lead to pain, dysfunction, and ultimately vertebral collapse; unfortunately, pathologic fractures resulting from vertebral destruction may be the first presentation of a spinal tumor.

Recent advancements in the diagnosis and treatment of many types of cancers have prolonged and improved the quality of life for cancer patients. Unfortunately, the oncologic treatment itself also contributes to the already present osteolytic bone loss. With increased survival and ongoing bone loss, osteolytic lesions are becoming much more a functional and clinical problem for these patients. If left untreated, vertebral body compression fractures occur with progressive kyphosis over multiple levels, cord compromise, and intractable pain. In this scenario, comorbid conditions and poor bone quality contribute to the difficulties of surgical intervention in this patient group. To alleviate these issues, percutaneous minimally invasive vertebral-augmentation techniques have recently evolved and show promising results for this debilitated group of patients. In tandem to the development of these less invasive surgical techniques, contemporary image-guided focused-beam radiotherapy techniques have also been developed, which minimize the collateral tissue effects of ionizing radiation. In combination, vertebral augmentation and spinal radiosurgery can control the tumor and maintain spinal stability. Combining the two approaches offers the patient rapid pain relief and restores normal spinal biomechanics while sparing the patient significant surgical morbidity.

Tumors secrete a wide variety of inflammatory mediators and cytokines, which are known to stimulate osteolytic bone resorption by modulating osteoclast formation and function. The compressive strength of trabecular bone is proportional to the square of its density (5). Osteolytic bone resorption leads to a reduction in bone density, which
decreases the ability of the vertebral body to withstand physiologic loads. This in turn leads to vertebral fracture, collapse, and eventually deformity progression.

The objective of a vertebral augmentation is to restore the strength and stiffness to the weakened vertebral body. In addition, the kyphoplasty technique attempts to reduce the existing deformity and provide structural support by enhancing the modulus of the vertebral body centrum. By preserving a trabecular mantle surrounding the cement bolus, vertebral stiffness and strength will not be significantly altered, thereby protecting the surrounding osteoporotic vertebrae from subsequent fractures. Kayanja et al. (6) biomechanically tested multilevel segments to determine whether the number and pattern of vertebral levels augmented with polymethylmethacrylate (PMMA) influenced strength and stiffness. The strength and stiffness of both the multilevel segments and individual vertebrae were dependent on BMD, and not the number of levels of prophylactic PMMA augmentation (6).

In 1984, “percutaneous vertebroplasty” was conceived in France to reduce vertebral pain as a result of a hemangioma (7). A cervical vertebra was injected with acrylic cement during open surgery to strengthen the vertebral body. An analgesic effect was noted, and indications for the technique in neoplastic disease and osteoporosis expanded to include both primary and secondary pathology.

The “kyphoplasty” technique as first performed in 1998, is a “least invasive method” of restoring the vertebral body to its native height followed by the cement augmentation (8). It involves the percutaneous introduction of inflatable bone tamps into the vertebral body under fluoroscopic guidance. Once inflated, the bone tamps restore the vertebral body toward its original height, while creating a cavity that can be filled with bone cement.

The traditional indications for vertebral augmentation are progressive collapse and intractable pain. Either a transpedicular or extrapedicular approach is used to reach the vertebral body. Contraindications to vertebral augmentation are systemic pathology, such as sepsis, prolonged bleeding times, or cardiopulmonary pathology, which would preclude the safe completion of the procedure. Other contraindications include patients with neurologic signs or symptoms, nonosteolytic infiltrative spinal metastases, vertebral height collapse of more than 60%, burst fractures, or vertebral bodies with deficient posterior cortices (9,10). Control of local disease and potential dissemination of disease are concerns and potential limitations of these vertebral augmentation techniques.

The results of both vertebroplasty and kyphoplasty reveal that they are safe and effective for pain relief when performed for the correct indications. Currently both vertebroplasty and kyphoplasty are used in the treatment of osteolytic vertebral fractures, and these methods should not be considered mutually exclusive. They are tools in the treatment spectrum of osteoporotic and osteolytic vertebral compression fractures to be used under the correct circumstances for each.

In our ongoing study of kyphoplasty for the treatment of compression fractures resulting from spinal metastases, we showed favorable preliminary results (11). We evaluated
the safety and efficacy of kyphoplasty in the first 21 patients over a 3-year period for the treatment of spinal metastases. The mean age of the patients was 60.8 years (range, 40 to 88 years). The indication for the kyphoplasty procedure was painful osteolytic vertebral body compression fracture. Symptomatic levels were identified with plain radiographs and magnetic resonance imaging. The primary sources of the metastases included breast cancer (nine patients), lymphoma (four patients), lung cancer (three patients), and unknown primary location (five patients).

Postoperative evaluation showed that the procedure was well tolerated, with improvement in pain that resulted in early mobilization in all 21 patients. Preoperative and postoperative SF-36 data were available for 14 of the 21 patients, with a mean follow-up of 50 weeks (range, 3 to 206 weeks). Significant improvement (preoperative vs. postoperative scores, respectively) was noted in the following areas: physical function, 20.9 to 33.5 (p = 0.036); vitality, 31.2 to 42.9 (p = 0.012); and social function, 37.5 to 66.1 (p = 0.011). No significant changes occurred in mental health (60.0 to 62.0), roleemotional (55.5 to 51.3), general health (52.1 to 46.0), bodily pain (31.6 to 39.0), and pain, as measured by the visual analogue scale (6.5 to 3.9). All 21 patients tolerated the procedure well, and no substantial systemic complications occurred. The fact that we found statistically significant improvement in only three of the SF-36 subscores may be due to the relatively small number of patients currently available. A trend was noted toward decreased pain after kyphoplasty. It is important to note that our primary indication for the treatment of these patients was palliation and to avoid open conventional surgical procedures that could have had a negative impact on the general quality of life of these patients with multiple medical comorbidities and limited life expectancies. The fact that we were able to show a decrease in visual-analogue scale pain scores from 6.5 to 3.9, although not statistically significant, suggests that a trend toward pain control existed.

Dudeney et al. (12) reported satisfactory results after kyphoplasty as treatment for osteolytic vertebral compression fractures secondary to multiple myeloma. In an ongoing evaluation of this patient group, we treated and evaluated 80 patients with multiple myeloma and associated vertebral body compression fractures (13). The mean age of our patients at the time of the procedure was 60.6 years (range, 35 to 85 years). Preoperative and postoperative SF-36 scores were available for 61 of 80 patients, with a mean follow-up of 15.6 months (range, 2 to 59 months). No major complications related to the technique have been observed. Significant (p < 0.05) improvement in SF-36 scores (preoperative vs. postoperative, respectively) were observed for the following areas: bodily pain, 23.0 to 44.4 (p < 0.001); physical function, 25.5 to 36.6 (p = 0.034); vitality, 30.3 to 38.1 (p = 0.039); and social functioning, 35.4 to 67.5 (p < 0.001). Mental health scores showed an improvement of 60.3 to 66.2 (p < 0.001), whereas role-emotion and general health were essentially unchanged (p = 0.086 and p = 0.054, respectively).

Fourney et al. (14), Weill et al. (15), and Cotton et al. (16) also reported their results with vertebral augmentation in metastases and myeloma. Fourney et al. reported on a group of 56 patients (21 myeloma, 35 other metastases) with a mean follow-up of 4.5 months. In this group were 65 vertebroplasties and 32 kyphoplasties. They reported 84% marked or complete pain relief, and only 9% of the patients experienced no relief of their pain. Weill et al. reported a retrospective series of 37 patients who underwent 52 vertebroplasty procedures for spinal metastases. Twenty-four of 33 treatment sessions (73%) performed for pain relief resulted in clear improvement (15). Cotton et al. (16) also reported prospectively acquired data obtained in 37 patients who underwent 40 vertebroplasty procedures for osteolytic metastases (29 patients) and myeloma (eight patients). Partial or complete pain relief was observed after 36 (97%) of 37 procedures.

These outlined results suggest that vertebral augmentation is efficacious in the treatment of vertebral body compression fractures secondary to metastases and multiple myeloma.