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Mallinckrodt Institute of Radiology, Washington University Medical Center, 510 S Kingshighway Blvd., Box 8131, St. Louis, MO 63110.
Received August 2, 2004;
accepted after revision September 25, 2004.
Address correspondence to D. B. Brown.
Abstract
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MATERIALS AND METHODS. Forty-five patients with osteoporotic spinal compression fractures of more than 1 year's duration were treated with vertebroplasty. Changes in pain and mobility were assessed by follow-up of 1-28 months. Preprocedural MR images were reviewed using the Modic criteria and were correlated with outcomes.
RESULTS. Fifteen patients (33%) had marrow edema on MRI and 30 (67%) of the 45 patients did not. All 15 of the patients with edema had clinical benefit: six patients (40%) achieved complete relief and nine (60%) experienced symptom improvement. Ten patients (67%) had improvement in mobility, and the remaining five patients (33%) had no change. Of patients with no marrow edema (n = 30), five (17%) had complete resolution of pain, 19 (63%) were improved, and six (20%) were unchanged. None had worsening of their symptoms. Mobility was improved in 17 (57%) and unchanged in 10 (33%). Mobility was diminished in three patients (10%). In two cases, impaired mobility was due to causes other than spine disorders.
CONCLUSION. Most (87%) of the 45 patients with compression fractures older than 1 year derived clinical benefit from vertebroplasty irrespective of MRI findings. Although 100% of patients with bone marrow edema had clinical benefit, no direct correlation was seen between symptom resolution and the presence of edema on preprocedural MRI. In our experience, absence of abnormal marrow signal does not definitively predict the outcome of vertebroplasty in chronic fractures.
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Although the treatment of older fractures was initially controversial, recent trials have reported good outcomes after treating older fractures. Significant improvement in pain and mobility after treatment of fractures with a mean age of 19 weeks has been described [9]. A separate article showed positive clinical response when treating fractures that had a mean duration of 37.7 months [10]. In the latter trial, patients with chronic fractures tended to have partial rather than complete relief of pain. Definitive indicators for treatment in patients with chronic fractures remain undefined.
Fracture findings on MRI evolve over time, and chronic fractures often show signal characteristics similar to those of normal bone marrow [8]. The purpose of this article is to investigate the findings on MRI performed before vertebroplasty for the treatment of chronic fractures. We sought to determine if the presence or absence of abnormal signal suggestive of bone marrow edema on preprocedural MRI correlates with the clinical outcome of vertebroplasty in chronic symptomatic vertebral compression fractures.
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From September 1998 to July 2002, 219 patients underwent 242 sessions of vertebroplasty with 479 levels treated. The location and number of levels treated in each patient were documented, as was the duration of symptoms corresponding to a radiographically documented fracture. The primary indication for vertebroplasty was intractable, focal, intense pain believed to be related to the fracture. Patients were excluded from the procedure if there was an uncorrectable coagulopathy, an unstable fracture involving the posterior elements, an inability to provide informed consent, absence of a defined level of collapse, or neurologic symptoms or signs related to vertebral body collapse. The radiologist performing the procedure verified the referring physician's neurologic assessment.
Vertebroplasty Procedure
Percutaneous vertebroplasty was performed with a sterile technique using a
C-arm angiographic unit (Angioskop D 33; Siemens Medical Solutions). Prone
positioning was used for both thoracic and lumbar vertebroplasty. Before the
procedure, the affected level was localized fluoroscopically and palpated to
confirm that physical examination correlated with radiographic findings. The
patient's blood pressure, heart rate, and oxygen saturation were monitored
from initiation of conscious sedation to the end of the procedure. Mild to
moderate conscious sedation was achieved using a combination of fentanyl
citrate (Sub-limaze, Abbott Laboratories) and midazolam (Versed, Roche
Pharmaceuticals). After sterile preparation and draping, the area overlying
the access site and the periosteum of the lamina posterior to the pedicle were
anesthetized with 1% lidocaine hydrochloride and 0.25% bupivacaine
hydrochloride.
After a small skin incision, an 11-gauge Jamshidi-type bone trochar needle (MDTech) was advanced until its tip abutted the cortex posterior to the pedicle. With the use of a careful technique and rotational fluoroscopy, the needle was advanced via the transpedicular approach into the anterior third of the vertebral body. Intraosseous venography was performed using 1-3 mL of iohexol (Omnipaque 180, Nycomed) to exclude direct venous communication, to detail venous drainage, and to assess vascularity [11]. If necessary, the needle was repositioned to opacify trabeculae before filling venous structures. The location of venous filling, if identified, was watched closely during cement injection to prevent embolization.
Methylmethacrylate powder (Osteobond copolymer bone cement, Zimmer) was mixed with 5 mL of sterilized barium sulfate [12]. This mixture was then ground into fine particles together with 1.2 g of tobramycin (Nebcin, Eli Lilly) early in our experience. Later, tobramycin was replaced with a first-generation cephalosporin given IV. The liquid methylmethacrylate monomer was then added to the powder and mixed to toothpaste-like consistency. The polymethylmethacrylate (PMMA) mixture was then placed into the back of a 20-mL syringe to backload a screw-type 10-mL syringe (LeVeen, Boston Scientific). The PMMA was injected in the lateral projection using a series of 1-mL syringes or a 10-mL syringe with a metal adapter [13]. Injection continued until the PMMA reached the posterior quarter of the vertebral body or it started passing into the disk space or paravertebral tissues. If filling of the PMMA reached the contralateral pedicle, a second needle was deemed unnecessary [14]. When filling of the vertebral body was thought to be insufficient, a second transpedicular needle was placed.
Follow-Up
After the procedure, follow-up was obtained by telephone calls to patients
2 weeks, 1 month, 3 months, 6 months, 1 year, and then annually after the
final procedure. Patients were asked whether their pain was gone, improved,
the same, or worse than before vertebroplasty. We considered patients with
complete elimination or improvement in pain to have achieved a clinical
benefit from vertebroplasty. Patients also were asked whether their current
level of activity had improved, was the same, or was worse after
vertebroplasty. Forty-five patients with symptoms greater than 1 year in
duration had preprocedure MRI; these individuals constituted the study
group.
MRI
In each case, the MR images that were obtained before vertebroplasty were
retrospectively reviewed to evaluate the predictive value of those studies. A
board-certified radiologist reviewed all the MR images. Each patient's outcome
was unknown to the reviewer at the time of retrospective MR image evaluation.
Bone marrow edema was defined as decreased signal intensity on T1-weighted
images or increased signal on T2-weighted or STIR images as described by Do
[8] and Modic et al.
[15].
Statistical Analysis
Subgroup analysis was performed using the chi-square test. Patients were
divided into groups according to pain relief in those with and those without
bone marrow edema, improvement in mobility in patients with and those without
bone marrow edema, improvement in pain with fractures of 1-2 years old and
those with fractures older than 2 years, and improvement in mobility with
fractures 1-2 years old and fractures older than 2 years.
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Fifteen (33%) of the 45 patients had marrow edema on MRI (Figs. 1A, 1B, 1C, and 1D). Ten (45%) of the 22 patients who had symptoms of 1-2 years' duration had increased signal on T2-weighted images. Five (22%) of the 23 patients who had symptoms of greater than 2 years' duration had marrow edema.
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Changes in pain are outlined in Table 2. Four (27%) of the 15 patients with bone marrow edema experienced complete elimination of pain, and the other 11 (73%) had improvement of their symptoms. Clinical benefit was achieved in 100% of these patients. In patients with no bone marrow edema (n = 30), 24 (80%) derived clinical benefit from vertebroplasty. Five (17%) experienced complete elimination of pain, 19 (63%) had improvement in pain, and six (20%) had no change in pain. No patients reported worsening of pain after vertebroplasty. The difference in clinical benefit between groups was not significant (p = 0.07).
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Changes in mobility are outlined in Table 3. Ten (67%) of the 15 patients with marrow edema had improved mobility after vertebroplasty. The remaining five (33%) patients reported no change, and no patients were worse. Of the patients with no marrow edema, 17 (57%) had improved mobility, 10 (33%) reported no change, and three (10%) had a decrease in mobility. One patient reported less mobility because of worsening congestive heart failure, and another reported a new knee injury unrelated to previous spinal disorders. The third patient had developed a new osteoporotic vertebral compression fracture unrelated to the previous vertebroplasty. The difference in improvement in mobility between groups was not statistically significant (p = 0.52).
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Of the 22 patients with symptoms of 1-2 years' duration, 10 (45%) had bone marrow edema and 12 (55%) did not. Overall, 91% (20/22) of patients had clinical benefit after vertebroplasty (Table 2). In the subgroup with edema, 100% (10/10) had diminished pain. Eighty-three percent (10/12) of patients with no marrow edema had improvement of their pain. Of the 23 patients with symptoms of 2 or more years' duration, five (22%) had bone marrow edema and 18 (78%) had none. Overall, 19 (83%) of the 23 patients had clinical benefit after vertebroplasty. In the subgroup with edema, five (100%) of five had clinical benefit. Twelve (67%) of 18 patients with no marrow edema had clinical benefit. The difference in clinical benefit between the groups with fractures of 1-2 years and fractures of more than 2 years was not statistically significant (p = 0.41).
Sixteen (73%) of 22 patients with symptoms of 1-2 years' duration had increased mobility after vertebroplasty (Table 3). In the group with marrow edema, seven (70%) of 10 had improved mobility. Nine (75%) of 12 of patients with no edema had improved mobility. Thirteen (57%) of 23 patients with symptoms of 2 or more years' duration had increased mobility after vertebroplasty. In the group with marrow edema, three (60%) of five had improved mobility. Ten (56%) of 18 patients with no edema had improved mobility. The difference in improvement in mobility between the groups with fractures of 1-2 years and fractures of more than 2 years was not statistically significant (p = 0.09).
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When patients are referred after the failure of a reasonable course of conservative therapy, vertebroplasty is successful at alleviating symptoms in 80-90% [20]. The duration of conservative therapy varies among studies [8]. Vertebral compression fractures lead to more than 161,000 hospital visits and 150,000 admissions each year [21]. Given the incidence of disease, some patients will present later as referring physicians continue to become aware of vertebroplasty as a therapeutic option.
Initial reports described poor results after treatment of fractures older than 6 [22] or 12 [23] months. However, two recent articles have reported more encouraging results after treatment of chronic fractures. Kaufmann et al. [9] treated 122 levels in 75 patients with a mean fracture age of 19 weeks. At the 1-month follow-up, they reported a significant improvement in pain and mobility for the entire patient group. Symptom relief after vertebroplasty was not dependent on fracture age. Brown et al. [10] reported results after treatment of fractures older than 1 year in 41 patients. Fractures in this group were older (mean, 40.4 months) and had longer follow-up (mean, 13.0 months) than those in the study by Kaufmann et al. Compared with a control group with fractures of less than 1 year, fewer patients with chronic fractures achieved complete relief of pain. However, 80% of patients with chronic fractures had improvement or complete relief of pain, a result similar to that in the patients with more acute compression deformities.
Imaging studies are used to guide performance of vertebroplasty whether patients have acute or chronic fractures. Conventional radiography is helpful but not definitive, because many patients will present with multiple compression deformities. Therefore, determining appropriate level(s) to treat on the basis of conventional radiography alone can be problematic [20]. Positive results on scintigraphy are a strong predictor of clinical outcome after vertebroplasty to treat acute fractures. Maynard et al. [22] reported pain relief in 26 of 28 patients evaluated with scintigraphy before treatment. The usefulness of scintigraphy to treat chronic fractures is unknown. Up to 59% of untreated vertebral fractures are scintigraphically negative at 12 months [24]. Whether patients with positive scintigraphic findings 12 months or more after fracture would obtain greater benefit from vertebroplasty than patients with negative results on scintigraphy may be an area for future investigation.
One of the strengths of MRI is its high sensitivity for bone marrow edema and the greater anatomic detail it reveals compared with conventional radiography or scintigraphy. Therefore, MRI has become an important tool in the evaluation of patients before vertebroplasty because of the combination of its sensitivity in detecting bone marrow edema and its multiplanar capabilities. Modic et al. [15] reviewed MR images from 474 consecutive patients and were able to directly compare imaging findings with histopathologic sections in a select number of cases. They also followed up patients over a 2- to 3-year period to evaluate the natural history of marrow edema that helped to classify age on the basis of signal intensity characteristics. They found that acute end-plate changes show increased signal characteristics on T2-weighted images and low signal on T1-weighted images (type 1). Long-term follow-up imaging revealed that signal intensity changes as vascularized fibrous tissue becomes replaced with fibrofatty tissues. After these changes occur, they manifest as isointense signal on T2-weighted images and increased signal on T1-weighted images (type 2). We used this scheme to help determine which of our studies were positive. Although all our patients in this series had symptoms for more than 1 year, it is possible that the fractures were continuing to evolve to maintain marrow edema on MRI.
As in the Modic paper [15], Do [8] reiterates that acute fractures are bright on T2-weighted images and dark on T1-weighted images, whereas chronic fractures are often isointense to fatty marrow on both sequences. These findings correlate with those in patients in this study who had negative findings on MRI before vertebroplasty. However, careful physical examination under fluoroscopy revealed focal tenderness at the levels of vertebral body compression for all the patients treated. We initially treat the levels that most accurately reproduce the patient's pain on physical examination. If a patient's pain is generalized or not reproduced at any specific level, vertebroplasty is not likely to improve symptoms. We believe that the information obtained from MRI before vertebroplasty is crucial, including evaluation of canal compromise, vertebral body shape, determination of the residual height of the affected vertebral body, and identification of other vertebrae that are in the early stages of fracture or collapse [25, 26]. This information is valuable even if bone marrow edema is absent and is the reason MRI (along with conventional radiography) remains the principal cross-sectional imaging technique that we use in preprocedure evaluation. The findings of this study suggest that if a patient has a chronic fracture with focal tenderness and marrow edema on MRI, clinical benefit should be achieved. However, in the setting of vertebral body compression on MRI that correlates with findings under fluoroscopically guided physical examination, we do not hesitate to offer vertebroplasty despite lack of edema on MRI or advanced fracture age.
One of the weaknesses of our study is its retrospective construct, although data were collected prospectively. A separate weakness is the absence of a formal validated questionnaire, which might have provided more quantitative information. By design of the questionnaire we used, fracture age was determined by patient verbal history. Although many patients could precisely recall the day the fracture occurred, initial and follow-up imaging documentation often was not performed or available. The patient groups were somewhat small, and it is possible that with a larger treatment population, a significant difference in treatment outcomes would have been seen between patients with and those without edema.
The findings of this study suggest that MRI of chronic vertebral compression fractures does not directly correlate with clinical success and that treatment with vertebroplasty is efficacious in symptomatic patients. However, all patients with evidence of edema on MRI had elimination or improvement of pain in our study. Patients without abnormal characteristics on MRI can be successfully treated with vertebroplasty if fluoroscopic examination correlates with the compressed level on imaging. Eighty percent of all patients with fractures older than 1 year had clinical benefit from vertebroplasty. The complete obliteration of pain in this patient group may be less than in individuals with more acute fractures.
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