Vertebroplasty: Osteoporotic Compression Fractures - Current Concepts and Outlook

Osteoporotic Compression Fractures

Vertebral compression fracture due to osteoporosis is a common problem, with an estimated annual incidence of 500,000 new patients in the U.S.¹⁹ Medical advances aimed at slowing or arresting bone loss from aging have only partially solves this problem, and the population effected is expected to grow steadily as life expectancy increases. Traditional conservative treatment for these fractures consists of non-steroidal anti-inflammatory agents and brief use of narcotic analgesics, a short period of immobilization, followed by gradual mobilization, activity modification, and possibly a spinal orthosis and physical therapy. This regimen is often successful but has shortcomings: bed rest is fraught with complications in an elderly population, including pulmonary compromise and decubitus ulcer formation. Furthermore, pain relief is neither immediate nor a guaranteed outcome. Consequently, percutaneous vertebroplasty has been used to treat osteoporotic compression fractures, with a growing clinical experience suggesting considerable pain relief, lasting for the duration of the limited follow-up of most of these studies.^{5, 7, 11, 19, 20} The initial indication for vertebroplasty in this condition was pain of 4-5 weeks duration persisting despite conservative therapy. Recently, vertebroplasty has been used more acutely after fracture in older patients who have medical co-morbidities that portend complications due to immobilization.

Percutaneous vertebroplasty was performed for painful osteoporotic compression fractures in 16 patients in a prospective study by Cortet et al.¹¹ They noted significant changes in pain and function scores, with these improvements persisting at 6 month follow-up. A large French series with 80 patients reported pain relief in over 90% of patients, with immediate onset and prolonged effect. Follow-up is reported as 1 month to 10 years, but detailed analysis is not provided.⁷ Jensen et al. published the earliest clinical experience with vertebroplasty in the U.S., treating 29 patients for 49 osteoporotic fractures. They reported pain relief in 26 patients (90%) within 24 hours, though long-term follow-up was unavailable.²⁰

Barr et al.⁵ had similar results but longer follow-up and more precise pain and function grading, with 24 of 38 patients (63%) reported marked improvement in pain and function, moderate relief in 12 of 38 (32%), and no relief in 2 of 38 (5%). Average follow-up was 18 months, and no recurrent collapse of the treated vertebra was noted. Of note, several patients developed new back pain in the same region as the treated vertebra; in one patient, an adjacent vertebra had sustained a compression fracture, which was then treated successfully. This finding underscores the need for long-term follow-up to define the natural history after treatment, specifically concerning changes at adjacent levels.^{7, 20}

Our Research

Using Osteoporotic elderly human cadaveric spines, we have been studying different injectable compounds, including special preparations of PMMA cements with increased radio-opacity and a degradable biological cement (Biocement D, EBI, Parsippany, NJ). By injecting known volumes of these materials into vertebrae, we note the ease of injection and measure injection pressures. We are also developing a quantitative system to describe the distribution of filling by cutting open vertebrae in the axial plane, dividing the cut surfaces into multiple sectors, and noting which sectors are filled with cement (Figure 2). This should allow for subsequent correlation between the pattern of filling in injected vertebrae as assessed by pre-testing CT scanning and biomechanical performance in compressive testing of these same vertebrae.

Figure 2: PMMA (black outline) within a vertebral body cut open in the axial plane with reference frame (white grid) superimposed.

Summary

Vertebroplasty has three main clinical uses: for painful or collapsing vertebrae due to hemangioma, spinal metastases, or Osteoporotic bone loss. Pain relief is prompt (within 1-2 days) and durable, as assessed by current, limited clinical follow-up. The most significant potential complication, thermal or mechanical damage to neural tissue in the canal or foramina, can be avoided by careful patient selection and proper technique.

Controversies abound regarding the technical details, basic science and clinical practice of vertebroplasty. Optimizing intra-procedure imaging and developing safer delivery systems are technical considerations remaining to be solved. Basic science investigation will address the importance of the pattern of cement distribution and will identify the best materials, whether PMMA or biodegradable preparations. An animal model may ultimately help solve the mechanism of action. Clinical questions concern the timing of treating osteoporotic fractures, and the long-term effects of treatment, especially at adjacent levels. Well-designed, randomized, prospective trials with careful follow-up will allow us to address these questions methodically. As with any evolving technique, we expect more investigation in all of these areas to shape our understanding of vertebroplasty and to guide its use as an effective clinical tool.