Value of Bone Scan Imaging in Predicting Pain Relief from Percutaneous Vertebroplasty in Osteoporotic Vertebral Fractures

Vertebral compression fractures represent a common cause of severe back pain among the elderly population. Sixteen percent of postmenopausal women suffer one or more vertebral compression fractures during their lifetime (1). In a significant percentage of cases, the pain related to the compression fracture persists despite bedrest and medical therapy. Percutaneous vertebroplasty, the injection of polymethylmethacrylate (PMMA) into vertebral compression fractures, has become an accepted method of treatment for painful osteoporotic compression fractures (2–9).

It has been reported that with proper patient selection, long-lasting relief of pain related to vertebral compression fractures can be achieved with percutaneous vertebroplasty (3). The ideal candidate for vertebroplasty presents within 4 months of the time of fracture and has midline, non-radiating back pain that increases with weight bearing and can be exacerbated by manual palpation of the spinous process of the involved vertebra. As experience with vertebroplasty increases, patients present, who, for various reasons, do not satisfy all above-cited criteria. Many have multiple fractures and lack sufficient imaging studies to document the age of some or all of their fractures. Other patients have several adjacent fractures that present difficulty in determining, by physical examination, which of the fractures is symptomatic. Still other patients have typical subjective pain patterns for vertebral compression fractures but experience no pain on palpation over the involved vertebra.

To our knowledge, there have been no previous studies reporting the use of adjunctive imaging strategies beyond plain film imaging to properly select patients who will experience pain relief with vertebroplasty. We report our experience using bone scan imaging to guide patient selection for vertebroplasty.

Methods

We performed a retrospective chart review of patients treated with percutaneous vertebroplasty for painful vertebral compression fractures at our institution between May 1995 and October 1999. This chart review was performed to identify patients who had undergone bone scan imaging as part of their preprocedural workup.

Results

Mobility

Semiquantitative assessment of mobility was available in 14 (50%) of 28 cases. In all (100%) 14 cases, at least one level of improved mobility was noted (range of improvement, 1–4 points; mean improvement, 1.7 points). Illustrative cases are shown in Figures 1 and 2.

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fig 1.

Images from the case of a 79-year-old man who presented with a history of back pain of several months' duration. Although the patient complained of mid and low back pain, he did not experience localizing pain during physical examination.

A, Lateral view plain film radiograph of the thoracic spine shows wedge compression fracture at T11 (arrow).

B, Lateral view plain film radiograph of the lumbar spine shows wedge compression fractures at L4 (arrow) and endplate compression fractures of L1, L2, and L3.

C, Posterior planar Tc^99m-MDP bone scan image shows markedly increased activity at L4 (large arrow) and minimal increased activity over the pedicles or facets of T11 (small arrows). Based on increased activity over L4 and relative lack of increased activity at other fracture sites, we proceeded with a single-level vertebroplasty at L4.

D, Lateral view plain film radiograph of the lumbar spine after vertebroplasty shows barium-opacified methylmethacrylate within the L4 vertebral body (arrow). The patient experienced complete pain relief after treatment. Before treatment, the patient's mobility was limited to walking with assistance. After treatment, he was able to walk without assistance.

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fig 2.

Images from the case of a 77-year-old man who presented with back pain of 3 months' duration.

A, Lateral view plain film radiograph obtained over the lumbar spine shows fractures at L1–L5. No previous images were available to date the onset of fracture at any level. However, because the patient experienced focal tenderness over the spinous processes of L2 and L3 without tenderness over the other fracture levels, we elected to proceed with vertebroplasty at L2 and L3, without performing preprocedural bone scan imaging.

B, Postprocedural lateral view plain film radiograph obtained over the lumbar spine shows barium-opacified methylmethacrylate within the L2 and L3 vertebral bodies. Cement injection at L3 traversed the entire marrow cavity. Cement selectively traversed the superior endplate region at L2, which is commonly seen as the cement naturally extends into fracture lines. Subjectively, the patient improved “about 50 percent,” but he requested further treatment, if possible. Bone scan imaging was performed because of uncertainty regarding further therapy.

C, Posterior planar Tc^99m-MDP² bone scan shows increased activity in the region of the L2 fracture (arrow). Based on the bone scan image, which suggested ongoing bone turnover in L2, we selectively targeted the inferior aspect of L2 for the second vertebroplasty treatment.

D, Postprocedural lateral view plain film radiograph shows barium-opacified methylmethacrylate within the inferior aspect of L2 (curved arrows). The patient noted complete pain relief after the second vertebroplasty at L2, stating that he felt “the best he has felt in years.”

Discussion

As percutaneous vertebroplasty disseminates to reach a progressively wider array of patients, case selection becomes increasingly difficult. Unlike during the early development of vertebroplasty, when patients would present with single, acute fractures and excellent film documentation, our current practice includes many patients with subacute or chronic pain in the setting of multiple fractures of uncertain age. In some cases, the results of physical examination may be compelling, indicating the painful vertebra or vertebrae. In most cases, however, physical examination is unrevealing and adjunctive tests may be required.

This study shows that increased activity revealed by bone scan imaging in a vertebral compression fracture is highly predictive of positive outcome after vertebroplasty. Among a series of 28 cases, pain relief was achieved in more than 90% of the treatment sessions. This cohort represents a particularly challenging series of patients in that many of them presented with multiple fractures of uncertain age and did not have localizing pain revealed by physical examination to guide vertebroplasty therapy. Our results suggest that bone scan imaging may be of value in guiding therapy in patients presenting with vertebral compression fractures, especially when multiple fractures are present or the pain is not localizing in nature.

Previous reports have shown high rates of pain relief after percutaneous vertebroplasty. Cotten et al (10) reported a series of 37 patients with painful vertebral lesions, either metastases or myeloma, in which greater than 90% of the patients experienced improvement in pain after undergoing vertebroplasty. Localizing the level of pain might be easier to achieve in treating patients with vertebral lesions, such as metastases or myeloma, than in treating those with multiple osteoporotic fractures of uncertain age, as in our series. Previous reports have indicated a 90% rate of improvement after vertebroplasty in a series of 29 patients with osteoporotic compression fractures (3). Unlike the current series, that group of patients typically experienced localized pain on palpation over one or more fractures, rendering treatment decisions relatively straightforward without adjunctive imaging techniques. We consider it notable that we were able to achieve a similar rate of improvement in this difficult patient population.

Other techniques, including CT and MR imaging, might also be useful in triaging patients before performing vertebroplasty therapy. Signal changes within the marrow of the vertebral body on MR images may suggest edematous changes in a healing fracture. Correlation of bone marrow edema using sequences that are particularly sensitive to the presence of edema, such as fat-suppressed T2-weighted imaging or fat-suppressed inversion recovery imaging, may also be useful in guiding vertebroplasty therapy. MR imaging offers the advantage over bone scan imaging of accurately assessing the degree of bony retropulsion or other findings that some practitioners may find useful. We have favored the use of bone scan imaging over MR imaging to distinguish painful fractures from healed fractures for two reasons. First, the bone scan image provides a functional assessment of bone turnover, which would be increased in a healing fracture. Second, because we frequently evaluate patients who travel long distances to be seen and treated by us and because it is difficult to obtain MR images on short notice, we have turned to bone scan imaging, which can be performed on short notice before performing vertebroplasty. It may prove helpful in future studies to compare the usefulness of MR imaging with that of bone scan imaging in patient selection for vertebroplasty.

Although this study suggests a striking benefit of bone scan imaging to guide therapy in vertebroplasty, it suffers several limitations. First, it was retrospective in nature. Quantification of pain and mobility was unavailable in many cases. In all likelihood, complete follow-up among our series would have shown even more compelling usefulness of bone scan imaging than we have shown here. Also, it would have been useful to know which patients had no localizing pain revealed by physical examination to delineate the usefulness of bone scan imaging further in difficult cases.

Another limitation of this study is that of workup bias (11). In other words, patients were treated with vertebroplasty after a positive bone scan image was obtained; patients with negative bone scan images were excluded from this series. Thus, although the value of increased activity revealed by bone scan imaging has been shown, the relevance of normal activity revealed by bone scan imaging of a vertebral compression fracture is less certain based on our data alone. It is entirely possible that patients without increased activity would also experience excellent pain relief after undergoing vertebroplasty; however, many of our patients presented with multiple fractures and gained complete pain relief after treating only those fractures with increased activity.

Bone scan imaging may reveal increased activity for up to 2 years after fracture, yet we have noted in other studies that patients with fractures of longer than 6 months' duration typically do not benefit from vertebroplasty (12). This disparity in duration of increased activity revealed by bone scan imaging as compared with the duration of the treatment window in vertebroplasty may explain the two cases that showed no improvement. Last, the placebo affect may account for many instances of pain relief.

This study points to the need for prospective evaluations of not only the method for patient selection before vertebroplasty but also the methods of evaluating the clinical response after vertebroplasty. The former need might be met with a direct comparison of bone scan imaging versus MR imaging in predicting patient improvement. The latter need might be met with the use of standardized methods such as the visual analog scale, McGill-Melzack scoring system, or Nottingham Health Profile (2).

Conclusion

Increased activity revealed by bone scan imaging is highly predictive of positive clinical response to percutaneous vertebroplasty. Bone scan imaging may be indicated when considering vertebroplasty therapy for patients suffering from multiple vertebral compression fractures of uncertain age or in patients with non-localizing pain patterns.