| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Original Research |
1 All authors: Department of Radiology, Kansai Medical University, Hirakata Hospital, 2-3-1 Shinmachi, Hirakata, Osaka 573-1191, Japan.
Received March 6, 2007;
accepted after revision June 12, 2007.
Address correspondence to N. Tanigawa
(tanigano{at}hirakata.kmu.ac.jp).
Abstract
 Top Abstract IntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
SUBJECTS AND METHODS. Percutaneous vertebroplasty was performed for osteoporotic compression fractures in 76 consecutive patients. Patients were divided into two groups according to the cement filling pattern shown on radiography and CT: cleft pattern group (group C, n = 34), compact and solid cement filling pattern in vertebrae; and trabecular pattern group (group T, n = 42), sponge-like filling pattern. A visual analog scale (VAS) was used to assess pain severity, and anterior and lateral radiographs of the thoracic and lumbar vertebrae were obtained 1-3 days and 1, 4, 10, 22, and 34 months after percutaneous vertebroplasty. Differences in treatment efficacy and the occurrence rates of new compression fractures were examined and compared for both groups using the Mann-Whitney U test and chi-square test.
RESULTS. A significant difference was seen between groups with respect to the volume of cement injected per vertebra (mean volume: group C, 4.5 mL; group T, 3.7 mL; p = 0.01). VAS improvement did not differ significantly between group C (4.6) and group T (4.5). The mean follow-up period was 19.5 months, during which new compression fractures were significantly more frequent in group C (17 of 34 [50%]) than in group T (11 of 42 [26.2%]; p = 0.03).
CONCLUSION. Although cement distribution patterns do not significantly affect initial clinical response, a higher incidence of new compression fractures is seen in patients with treated vertebrae exhibiting a cleft pattern.
Keywords: CT • neuroradiology • percutaneous vertebroplasty • polymethyl methacrylate • radiography • vertebral body fracture • vertebroplasty
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Although a general consensus is lacking regarding the causes of new compression fractures after percutaneous vertebroplasty, new fractures often occur in vertebral bodies adjacent to the vertebral bodies treated by percutaneous vertebroplasty [2-4]. Furthermore, such new compression fractures occur relatively soon after percutaneous vertebroplasty [2] and fractures of adjacent vertebrae occur significantly sooner [5].
We hypothesized that different cement distribution patterns in treated vertebrae affect the frequency of new compression fractures. The purpose of this study was to prospectively investigate relationships between cement distribution patterns and the occurrence rates of new compression fractures after percutaneous vertebroplasty.
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
The indication for percutaneous vertebroplasty was back pain caused by vertebral body compression fracture with pain on percussion of the vertebral spinous process. In patients with multiple compression fractures in whom percussion pain of the spinous process was unclear, physical examination was performed using fluoroscopy. Patients with back pain attributed to myelopathy or radiculopathy resulting from stenosis of the vertebral canal or narrowing of the intervertebral foramen were excluded.
Before percutaneous vertebroplasty was performed, physical examination, neurologic examination, ECG, respiratory function tests (forced expiratory volume in 1.0 second, percent of forced expiratory volume in 1.0 second, forced vital capacity, percent of forced vital capacity), and laboratory investigations (RBC, WBC, platelet count, prothrombin time, C-reactive protein) were performed. The following diagnostic imaging studies were also obtained: anterior and lateral radiographs of the thoracic and lumbar vertebrae; MR images of the vertebrae, including the vertebrae affected by compression fracture (performed within 1 week of the procedure); and CT scans.
Analysis of Cement Filling Pattern and Patient Classification
Images were evaluated by two neuroradiologists. The neuroradiologists were
aware that the patients had undergone percutaneous vertebroplasty for
osteoporotic compression fracture. However, they were blinded to specific
information, such as the preprocedural MRI findings, amount of bone cement
used, approach route, clinical results of the procedure, and other clinical
data (including patient history), and reached a consensus for each case.
Vertebral bodies were classified in two groups according to the cement distribution pattern on anterior and lateral radiography of the thoracic or lumbar vertebrae, including treated vertebrae. Classification criteria were as follows: cleft type, vertebrae with compact and solid cement filling; and trabecular type, vertebrae with sponge-like cement filling. Furthermore, on the basis of this classification system, patients were divided into the following two groups: group C, patients with at least one vertebra exhibiting the cleft pattern; and group T, patients with vertebrae exhibiting the trabecular pattern only.
Percutaneous Vertebroplasty Procedure
Percutaneous vertebroplasty was performed under combined CT and
fluoroscopic guidance (Advantx LCA plus ACT, GE Healthcare). Thirty minutes
before the procedure, 10 mg of morphine hydrochloride (Morphine HCI Inj. 10,
Sankyo), 0.5 mg of atropine sulfate (Atropine Sulf. Inj., Tanabe), and 25 mg
of hydroxyzine hydrochloride (Atarax-P Inj., Pfizer Japan) were administered
intramuscularly. Local anesthetic, 10 mL of 1% lidocaine (Xy-locaine Inj. E,
AstraZeneca), was administered from the skin to the periosteum of the pedicle
using a 22-gauge needle (Cathelin needle, Terumo Europe) under fluoroscopic
guidance.
After the orientation of the puncture needle was confirmed on CT and the puncture needle was aligned with the Cathelin needle, a 13-gauge bone biopsy needle (Osteo-Site Bone Biopsy Needle Murphy M2, Cook) was advanced into the pedicle of the vertebral arch. CT was repeated, and after the orientation of the biopsy needle was confirmed, the visualization technique was changed to lateral fluoroscopy and the bone biopsy needle was advanced to the anterior third of the vertebral body close to midline.
Intraosseous venography was performed with 1-5 mL of iopamidol (Iopamiron 300, Schering Japan) or 10-20 mL of carbon dioxide to confirm that the needle was not positioned in a direct venous anastomosis to the central or epidural veins. Subsequently, 20 g of PMMA powder (Osteobond copolymer bone cement, Zimmer) was mixed with 5 g of barium sulfate powder that had been sterilized with dry heat to increase opacity. PMMA was produced by adding 10 mL of liquid methylmethacrylate monomer to the powder, and then the mixture was blended to a toothpaste-like consistency.
PMMA was injected with lateral fluoroscopic guidance using 1-mL syringes. The PMMA injection was terminated when adequate filling of the vertebral body was achieved or if leakage occurred. If leakage occurred, the needle was repositioned, and additional PMMA was injected to fill the remaining part of the vertebral body. The needle was then removed, and all patients were observed in the supine position for 2 hours after the procedure.
Outcome Evaluation and Postprocedural Management
Pain level was evaluated with a visual analog scale (VAS) of 0-10, with 0
representing no pain and 10 indicating the worst pain. The severity of
preprocedural pain was assessed by either the attending physician or the
physician who was scheduled to perform percutaneous vertebroplasty on either
the day before or the day of percutaneous vertebroplasty. The severity of the
postprocedural pain was assessed by either the attending physician or the
physician who performed percutaneous vertebroplasty between 1 and 3 days after
the procedure.
At our institution, patients are admitted for percutaneous vertebroplasty, and once the procedure is completed, they are returned to their ward and instructed to rest in the supine position for 2 hours. Although patients were allowed to move after that 2-hour period, most patients slept due to the effects of premedication. Thus, the severity of pain after percutaneous vertebroplasty was not assessed on the day of the procedure.
Follow-Up Protocol
At our institution, percutaneous vertebroplasty was performed on an
inpatient basis. During postprocedural days 1-3, pain severity was assessed,
and frontal and lateral radiography of the thoracic and lumbar vertebrae was
performed. In addition, at 1, 4, 10, 22, and 34 months after discharge from
the hospital, patients were asked to undergo follow-up at our outpatient
clinic, where medical history was recorded, physical examinations were
performed, and additional frontal and lateral radiographs of the thoracic and
lumbar vertebrae were obtained. Patients were also instructed to return to our
institution if they experienced pain, and in such cases, physical examination
and radiography were performed; MRI was also performed as necessary.
A new compression fracture was defined as follows: a vertebral body exhibiting reduced height on radiography; or if the height difference was unclear, a vertebral body exhibiting a bone marrow edema pattern on MRI in patients with localized spontaneous pain or pain on percussion of the spinous process. Two radiologists reviewed the imaging findings and arrived at a final diagnosis by discussion if their opinions did not agree.
Statistical Analysis
The degree of VAS improvement in each patient was calculated by subtracting
the postprocedural VAS from the preprocedural VAS. Intergroup differences in
the degree of VAS improvement were statistically assessed. Among groups C and
T, patient age, the volume of cement injected per vertebra, number of treated
vertebrae, degree of VAS improvement, and length of time from percutaneous
vertebroplasty to the diagnosis of a new compression fracture were compared
and analyzed using Wilcoxon's rank sum test. Fisher's exact test was used to
analyze patient sex differences, and the chi-square test was used to compare
the occurrence rate of new compression fractures. The statistical analyses
were conducted using StatView (version 5.0, SAS Institute) for Windows
(Microsoft), and p values of < 0.05 were considered statistically
significant.
By using pre- and postprocedural standing lateral radiographs, the anterior, middle, and posterior vertebral heights were measured on the basis of the techniques used by McKiernan et al. [6]. The degree of height restoration in each vertebra was calculated by subtracting the preprocedural vertebral height from the postprocedural vertebral height. Intertype differences in the degree of height restoration were statistically assessed.
|
|
|
|
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
|
|
Fisher's exact test showed a significant difference in the distribution of patients between groups C and T on the basis of patient sex (p = 0.04). Wilcoxon's rank sum test indicated no significant differences between groups with respect to patient age, the number of treated vertebrae, or the preprocedural VAS. However, a significant difference was seen between the groups with respect to the volume of cement injected per vertebra (p = 0.01, Table 3). VAS improvement, defined as the pre- to postprocedural difference (preprocedural VAS - postprocedural VAS), was 4.6 ± 2.5 (mean pain score ± SD) in group C and 4.5 ± 2.9 in group T. No significant difference between the groups was identified (Table 4).
|
|
Significant differences were seen between the preprocedural and postprocedural vertebral body heights of the anterior, middle, and posterior areas of both types; however, a statistically significant difference was evident between type C and type T with respect to the degree of height restoration in the middle (p < 0.01) and posterior (p < 0.01) areas (Table 5).
|
The mean follow-up period was 16.7 months (range, 1-34 months). During the follow-up period, a new fracture was identified in 17 of the 34 patients (50%) with a cleft pattern. Conversely, a new fracture was identified in 11 of 42 patients (26.2%) with a trabecular pattern. A significant difference in the incidence of new fracture was thus seen between the groups (p = 0.03). Moreover, an adjacent fracture was found in 15 of the 34 patients (44.1%) with a cleft pattern and seven of the 42 patients (16.7%) with a trabecular pattern, again representing a significant difference in incidence of new adjacent fracture between groups (p = 0.009).
The mean length of time (± SD) from percutaneous vertebroplasty to new compression fracture was 3.5 ± 3.7 months (range, 1-10 months) for group T and 1.7 ± 1.3 months (range, 1 week-4 months) for group C, representing no significant intergroup differences (p = 0.18).
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
Between groups C and T, no significant intergroup differences in the degree of early improvement were seen according to VAS. Patient age at fracture onset is one factor affecting the degree of early improvement in VAS. In other words, among patients without cleft patterns, the degree of early improvement in VAS is more favorable for patients with bone marrow edema than for those without bone marrow edema [7, 8]. In the present study, patient age at fracture onset was low for group T, and these patients were more responsive to percutaneous vertebroplasty. Group C patients had cleft patterns, and patients with cleft patterns have been shown to respond well to percutaneous vertebroplasty [9]. In other words, because both groups of patients responded well to percutaneous vertebroplasty, no significant intergroup differences were seen. As we mentioned, a difference in the volume of cement injected was seen between types T and C, with a greater volume of cement injected for type C vertebrae. Hodler et al. [10] and Kaufmann et al. [11] investigated relationships between cement volume and clinical outcome and reported no correlation, agreeing with the results of our study.
A significant difference in incidence of new compression fractures was seen between the two patient groups after percutaneous vertebroplasty, with a higher incidence of new compression fractures in group C. One reason for this higher incidence was that the volume of cement injected per vertebra was greater for type C than for type T. The amount of PMMA is thought to be related to restored height of treated vertebra. We hypothesized that the restored height of a treated vertebra showing a cleft pattern is greater than that with a trabecular pattern. The increased height of the collapsed vertebral body could increase soft-tissue tension around the vertebral body, leading to an increased load on other vertebrae, particularly those adjacent to the vertebra with the original fracture.
Another reason for the higher incidence of compression fractures in group C is that the duration of fracture was higher for group C than for group T. Because vertebral body alignment and the structures around the fractured vertebral bodies, including muscles, had become used to the vertebral fracture, the degree of restoration in vertebral height was greater due to percutaneous vertebroplasty. In other words, rapid alignment restoration may trigger new compression fractures.
Many fractures occurred adjacent to the treated vertebrae for group C. Compression fractures accompanying cleft patterns are known to occur frequently in the thoracolumbar junction [12, 13]. Hence, it is reasonable to assume that new compression fractures frequently occur in the thoracolumbar junction as part of the natural course of osteoporosis, and we cannot conclude that compression fractures are likely to occur adjacent to percutaneous vertebroplasty-treated vertebrae for type C.
In the present study, there were no statistically significant differences in the length of time from percutaneous vertebroplasty to a new compression fracture between groups C and T. Trout et al. [14] reported no marked difference in the length of time from percutaneous vertebroplasty to a new compression fracture between patients with and those without cleft patterns, which agrees with the results of our study.
This study has several limitations. First, we treated an average of two vertebrae per patient, and patients were classified on the basis of the presence of an intraosseous cleft per patient. Ideally, a new fracture would be assessed in patients with single-level vertebroplasty only. If the methods used in this study were used to assess new compression fractures in patients with a single treated vertebra, a closer relationship between the cement distribution pattern and new compression fracture after vertebroplasty might be found. Second, we did not take into account the effects of cement leakage on new compression fractures. Cement leakage into the intervertebral disk is known to be one factor that contributes to new compression fractures, and the incidence of cement leakage, particularly leakage to the intervertebral disk, must be considered.
In conclusion, our results indicate that although the cement distribution pattern after percutaneous vertebroplasty does not significantly affect initial clinical response, a higher incidence of new compression fractures, particularly fractures of adjacent vertebrae, is seen in patients with percutaneous vertebroplasty-treated vertebrae exhibiting a cleft pattern.
|
TopAbstractIntroductionSubjects and MethodsResultsDiscussionReferences |
|---|
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
