Showing papers in "Spine in 2006"

What is intervertebral disc degeneration, and what causes it?

Abstract: and Introduction Abstract Study Design: Review and reinterpretation of existing literature. Objective: To suggest how intervertebral disc degeneration might be distinguished from the physiologic processes of growth, aging, healing, and adaptive remodeling. Summary of Background Data: The research literature concerning disc degeneration is particularly diverse, and there are no accepted definitions to guide biomedical research, or medicolegal practice. Definitions: The process of disc degeneration is an aberrant, cell-mediated response to progressive structural failure. A degenerate disc is one with structural failure combined with accelerated or advanced signs of aging. Early degenerative changes should refer to accelerated age-related changes in a structurally intact disc. Degenerative disc disease should be applied to a degenerate disc that is also painful. Justification: Structural defects such as endplate fracture, radial fissures, and herniation are easily detected, unambiguous markers of impaired disc function. They are not inevitable with age and are more closely related to pain than any other feature of aging discs. Structural failure is irreversible because adult discs have limited healing potential. It also progresses by physical and biologic mechanisms, and, therefore, is a suitable marker for a degenerative process. Biologic progression occurs because structural failure uncouples the local mechanical environment of disc cells from the overall loading of the disc, so that disc cell responses can be inappropriate or aberrant. Animal models confirm that cell-mediated changes always follow structural failure caused by trauma. This definition of disc degeneration simplifies the issue of causality: excessive mechanical loading disrupts a disc's structure and precipitates a cascade of cell-mediated responses, leading to further disruption. Underlying causes of disc degeneration include genetic inheritance, age, inadequate metabolite transport, and loading history, all of which can weaken discs to such an extent that structural failure occurs during the activities of daily living. The other closely related definitions help to distinguish between degenerate and injured discs, and between discs that are and are not painful.

Back Pain Prevalence and Visit Rates : Estimates From U.S. National Surveys, 2002

Abstract: Study design Review and analysis of data from two U.S. national surveys in 2002. Objectives To examine the prevalence of back pain and physician visits for back pain in the United States. Summary of background data National data on the prevalence of back pain become available only intermittently. Methods We summarized published data from the 2002 National Health Interview Survey (NHIS) on the prevalence of back pain and compared it with earlier surveys. We also analyzed the 2002 National Ambulatory Medical Care Survey (NAMCS) to determine physician visit rates for back pain. Results In the 2002 NHIS, there were 31,044 adult respondents. Low back pain lasting at least a whole day in the past 3 months was reported by 26.4% of respondents, and neck pain was reported by 13.8%. Among racial groups, American Indians and Alaska Natives had the highest prevalence of low back pain, and Asian Americans had the lowest. Prevalence generally declined with greater levels of education and increasing income. Prevalence estimates were consistent with those from previous surveys, although methodologic differences limited comparisons. NAMCS data suggested that the proportion of all physician visits attributable to low back pain (2.3% in 2002) has changed little since the early 1990s. Conclusions About one fourth of U.S. adults report low back pain in the past 3 months; the proportion of physician visits attributed to back pain has changed little in the past decade.

United States Trends and Regional Variations in Lumbar Spine Surgery: 1992–2003

Abstract: Study Design Repeated cross-sectional analysis using national Medicare data from the Dartmouth Atlas Project.

Adverse effects associated with high-dose recombinant human bone morphogenetic protein-2 use in anterior cervical spine fusion

Abstract: Study design A retrospective review of patients who underwent an anterior cervical fusion using recombinant human bone morphogenetic protein (rhBMP)-2 with an absorbable collagen sponge (INFUSE; Medtronic Sofamor Danek, Minneapolis, MN). Objective To ascertain the complication rate after the use of high-dose INFUSE in anterior cervical fusions. Summary of background data The rhBMP-2 has been primarily investigated in lumbar spine fusions, where it has significantly enhanced the fusion rate and decreased the length of surgery, blood loss, and hospital stay. Methods We present 151 patients who underwent either an anterior cervical discectomy and fusion (n = 138) or anterior cervical vertebrectomy and fusion (n = 13) augmented with high-dose INFUSE between July 2003 and March 2004. The rhBMP-2 (up to 2.1 mg/level) was used in the anterior cervical discectomy and fusions. Results A total of 35 (23.2%) patients had complications after the use of high-dose INFUSE in the cervical spine. There were 15 patients diagnosed with a hematoma, including 11 on postoperative day 4 or 5, of whom 8 were surgically evacuated. Thirteen individuals had either a prolonged hospital stay (> 48 hours) or hospital readmission because of swallowing/breathing difficulties or dramatic swelling without hematoma. Conclusions A significant rate of complications resulted after the use of a high dose of INFUSE in anterior cervical fusions. We hypothesize that in the cervical area, the putative inflammatory effect that contributes to the effectiveness of INFUSE in inducing fusion may spread to adjacent critical structures and lead to increased postoperative morbidity. A thorough investigation is warranted to determine the optimal dose of rhBMP-2 that will promote cervical fusion and minimize complications.

Vertebroplasty and kyphoplasty: a systematic review of 69 clinical studies.

Abstract: STUDY DESIGN: Systematic literature review. OBJECTIVE: To evaluate the safety and efficacy of vertebroplasty and kyphoplasty using the data presented in published clinical studies, with respect to patient pain relief, restoration of mobility and vertebral body height, complication rate, and incidence of new adjacent vertebral fractures. SUMMARY OF BACKGROUND DATA: Vertebroplasty and kyphoplasty have been gaining popularity for treating vertebral fractures. Current reviews provide an overview of the procedures but are not comprehensive and tend to rely heavily on personal experience. This article aimed to compile all available data and evaluate the clinical outcome of the 2 procedures. METHODS: This is a systematic review of all the available data presented in peer-reviewed published clinical trials. The methodological quality of included studies was evaluated, and data were collected targeting specific standard measurements. Where possible, a quantitative aggregation of the data was performed. RESULTS: A large proportion of subjects had some pain relief, including 87% with vertebroplasty and 92% with kyphoplasty. Vertebral height restoration was possible using kyphoplasty (average 6.6 degrees ) and for a subset of patients using vertebroplasty (average 6.6 degrees ). Cement leaks occurred for 41% and 9% of treated vertebrae for vertebroplasty and kyphoplasty, respectively. New fractures of adjacent vertebrae occurred for both procedures at rates that are higher than the general osteoporotic population but approximately equivalent to the general osteoporotic population that had a previous vertebral fracture. CONCLUSIONS: The problem with stating definitely that vertebroplasty and kyphoplasty are safe and effective procedures is the lack of comparative, blinded, randomized clinical trials. Standardized evaluative methods should be adopted.

Identifying subgroups of patients with acute/subacute "nonspecific" low back pain: results of a randomized clinical trial.

Abstract: Study design Randomized clinical trial Objective Compare outcomes of patients with low back pain receiving treatments matched or unmatched to their subgrouping based on initial clinical presentation Summary of background data Patients with "nonspecific" low back pain are often viewed as a homogeneous group, equally likely to respond to any particular intervention Others have proposed methods for subgrouping patients as a means for determining the treatment most likely to benefit patients with particular characteristics Methods Patients with low back pain of less than 90 days' duration referred to physical therapy were examined before treatment and classified into one of three subgroups based on the type of treatment believed most likely to benefit the patient (manipulation, stabilization exercise, or specific exercise) Patients were randomly assigned to receive manipulation, stabilization exercises, or specific exercise treatment during a 4-week treatment period Disability was assessed in the short-term (4 weeks) and long-term (1 year) using the Oswestry Comparisons were made between patients receiving treatment matched to their subgroup, versus those receiving unmatched treatment Results A total of 123 patients participated (mean age, 377 +/- 107 years; 45% female) Patients receiving matched treatments experienced greater short- and long-term reductions in disability than those receiving unmatched treatments After 4 weeks, the difference favoring the matched treatment group was 66 Oswestry points (95% CI, 070-125), and at long-term follow-up the difference was 83 points (95% CI, 25-141) Compliers-only analysis of long-term outcomes yielded a similar result Conclusions Nonspecific low back pain should not be viewed as a homogenous condition Outcomes can be improved when subgrouping is used to guide treatment decision-making

Decision Making Regarding Smith-Petersen vs. Pedicle Subtraction Osteotomy vs. Vertebral Column Resection for Spinal Deformity

Abstract: Study design Author experience and literature review. Objectives To investigate and discuss decision-making on when to perform a Smith-Petersen osteotomy as opposed to a pedicle subtraction procedure and/or a vertebral column resection. Summary of background data Articles have been published regarding Smith-Petersen osteotomies, pedicle subtraction procedures, and vertebral column resections. Expectations and complications have been reviewed. However, decision-making regarding which of the 3 procedures is most useful for a particular spinal deformity case is not clearly investigated. Methods Discussed in this manuscript is the author's experience and the literature regarding the operative options for a fixed coronal or sagittal deformity. Results There are roles for Smith-Petersen osteotomy, pedicle subtraction, and vertebral column resection. Each has specific applications and potential complications. Conclusion As the magnitude of resection increases, the ability to correct deformity improves, but also the risk of complication increases. Therein, an understanding of potential applications and complications is helpful.

The course of low back pain from adolescence to adulthood: eight-year follow-up of 9600 twins.

Abstract: Study design Prospective study with 8-year follow-up. Objective To describe the evolution of low back pain from adolescence into adulthood. Summary of background data High prevalence rates of low back pain among children and adolescents have been demonstrated in several studies, and it has been theorized that low back pain in childhood may have important consequences for future low back pain. It is important to understand the nature of such a link if effective preventive programs are to be established. Methods Almost 10,000 Danish twins born between 1972 and 1982 were surveyed by means of postal questionnaires in 1994 and again in 2002. The questionnaires dealt with various aspects of general health, including the prevalence of low back pain, classified according to number of days affected (0, 1-7, 8-30, >30). Results Low back pain in adolescence was found to be a significant risk factor for low back pain in adulthood with odds ratios as high as four. We also demonstrated a dose-response association: the more days with low back pain at baseline, the higher the risk of future low back pain. Twenty-six percent of those with low back pain for more than 30 days during the baseline year also had more than 30 days with low back pain during the follow-up year. This was true for only 9% of the rest of the sample. Conclusions Our study clearly demonstrates correlations between low back pain in childhood/adolescence and low back pain in adulthood. This should lead to a change in focus from the adult to the young population in relation to research, prevention, and treatment.

Increased swelling complications associated with off-label usage of rhBMP-2 in the anterior cervical spine.

Abstract: Study Design/Setting. Independent, retrospective clinical record review with a concurrent control. Objective. To identify whether rhBMP-2 is associated with an increased incidence of clinically relevant postoperative prevertebral swelling problems in patients undergoing anterior cervical fusions. of Background Data. Bone Morphogenetic Protein-2 (rhBMP-2) is FDA approved as a bone graft substitute in anterior lumbar interbody fusions. rhBMP-2 has also been used "off-label" in anterior cervical fusions. We suspected that rhBMP-2 might increase the incidence of adverse swelling events. Methods. A total of 234 consecutive patients (ages 12-82 years) undergoing anterior cervical fusion with and without rhBMP-2 over a 2-year period at one institution comprised the study population. The incidence of clinically relevant prevertebral swelling was calculated. The populations were compared and statistical significance was determined. Results. A total of 234 patients met the study criteria, 69 of whom underwent anterior cervical spine fusions using rhBMP-2; 27.5% of those patients in the rhBMP-2 group had a clinically significant swelling event versus only 3.6% of patients in the non-rhBMP-2 group. This difference was statistically significant (P < 0.0001) and remained so after controlling for other significant predictors of swelling. Conclusions. Off-label use of rhBMP-2 in the anterior cervical spine is associated with an increased rate of clinically relevant swelling events.

Chordoma of the mobile spine: fifty years of experience.

Abstract: Study design A consecutive series of 52 chordomas of the mobile spine observed over a 50-year period includes a retrospective review of 15 cases treated prior to 1991 and a prospective group of 37 cases treated from 1991 to 2002. Objectives This series reviews epidemiologic issues as well as clinical patterns of spinal chordomas. We attempt to correlate tumor extent, treatment, and outcomes over time. Summary of background data Chordoma is the most frequent primary tumor of the mobile spine. Due to slow growth, both initial symptoms and recurrences after treatment arise later, making it difficult to evaluate the effectiveness of treatment protocols. Methods A prospective series of 37 cases is compared with a retrospective group of 15 patients observed between 1954 and 1991. In the prospective study, all patients had imaging studies, and oncologic and surgical staging. When en bloc resection was not feasible, intralesional extracapsular excision was combined with radiation therapy. The prospective patients were clinically evaluated and imaged. Patients in the retrospective group were evaluated by chart and available images; of these, only one en bloc resection (intralesional margin) was performed. Survivors were all evaluated clinically and had radiographic studies. Results Forty-eight patients were available for long-term follow-up. Four died due to post-operative complications, and six due to disease less than 2 years after treatment. Forty-two patients were followed over 2 years; 26 patients had over 5 years follow-up. All patients having radiation alone, intralesional excision, or a combination had recurrences in less than 2 years, and died in some cases after a long survival with symptomatic disease. Intralesional extracapsular excision with radiation had a high rate of recurrence (12 of 16 at average 30 months), but 3 patients are continuously disease-free (CDF) at mean 52 months and 5 are alive with disease at average 69 months (ranging 24 to 146). Twelve of 18 patients having en bloc resection are CDF at average 8 years (48 to 155 months). The remaining 6 recurred and of these 1 died. All of these (6) had been previously treated and/or had en bloc resections with contaminated margins. Conclusions The only treatment protocol associated with CDF at follow-up longer than 5 years is margin-free en bloc resection.

Gravity line analysis in adult volunteers: age-related correlation with spinal parameters, pelvic parameters, and foot position.

Abstract: Study design Prospective radiographic and forceplate analysis in adult volunteers. Objective Assess gravity line (GL) location and foot position regarding anatomic spinal structures to evaluate key correlations and age-related changes in balance. Summary of background data Global spinal balance is commonly assessed by the C7 plumbline. This radiographic parameter does not offer information on foot position or forces transmitted, and poor correlation with the true GL has been demonstrated. Methods A total of 75 asymptomatic adult volunteers were equally distributed into three age groups. Full length, free-standing spine radiographs were obtained with simultaneous acquisition of GL and feet location (forceplate). GL and heels were projected on each radiograph to compute their distance from anatomic entities and to investigate correlations with radiologic parameters and age-related changes. Results In this study group, advancing age led to a significant increase in thoracic kyphosis. The plumbline from C7 shifted anteriorly with age. In the sagittal plane, the GL was anterior to the vertebral column for all groups. With age, the GL location regarding the heels remained constant, while the pelvis moved posteriorly toward the heels and underwent a small retroversion (increasing pelvic tilt). The acetabulum was the most reliable radiographic marker of the GL location. Conclusions This quantitative study in volunteers reveals clear age-related changes in the spino-pelvic association and offers quantitative support to the "cone of economy" concept proposed by Dubousset. The pelvis can be seen as a regulator to help maintain a rather fixed GL-heel association with age-related changes in the spinal column. Further study in patients suffering from deformity can confirm the importance of radiographic-gravity line correlations and enhance our understanding of optimal balance.

Epidemiology of traumatic spinal cord injury in Canada.

Abstract: STUDY DESIGN: Retrospective review. OBJECTIVE: To describe the incidence, clinical features, and treatment of traumatic spinal cord injury (SCI) treated at a Canadian tertiary care center. SUMMARY OF BACKGROUND DATA: Understanding the current epidemiology of acute traumatic SCI is essential for public resource allocation and primary prevention. Recent reports suggest that the mean age of patients with SCI may be increasing. METHODS: We retrospectively reviewed hospital records on all patients with traumatic SCI between January 1997 and June 2001 (n = 151). Variables assessed included age, gender, length of hospitalization, type and mechanism of injury, associated spinal fractures, neurologic deficit, and treatment. RESULTS: Annual age-adjusted incidence rates were 42.4 per million for adults aged 15-64 years, and 51.4 per million for those 65 years and older. Motor vehicle accidents accounted for 35% of SCI. Falls were responsible for 63% of SCI among patients older than 65 years and for 31% of injuries overall. Cervical SCI was most common, particularly in the elderly, and was associated with fracture in only 56% of cases. Thoracic and lumbar SCI were associated with spinal fractures in 100% and 85% of cases, respectively. In-hospital mortality was 8%. Mortality was significantly higher among the elderly. Treatment of thoracic and lumbar fractures associated with SCI was predominantly surgical, whereas cervical fractures were equally likely to be treated with external immobilization alone or with surgery. CONCLUSION: A large proportion of injuries was seen among older adults, predominantly as a result of falls. Prevention programs should expand their focus to include home safety and avoidance of falls in the elderly. Language: en

Complications in spinal fusion for adolescent idiopathic scoliosis in the new millennium. A report of the Scoliosis Research Society Morbidity and Mortality Committee.

Abstract: STUDY DESIGN The Morbidity and Mortality database of the Scoliosis Research Society (SRS) was queried as to the incidence and type of complications as reported by its members for the treatment of adolescent idiopathic scoliosis (AIS) with spinal fusion and instrumentation procedures regarding surgical approach (anterior, posterior, or combined anterior-posterior) during a recent 3-year period. OBJECTIVE To evaluate the incidence of surgeon-reported complications in a large series of spinal fusions with instrumentation for a single spinal deformity diagnosis and age group regarding surgical approach. SUMMARY OF BACKGROUND DATA The SRS has been collecting morbidity and mortality data from its members since its formation in 1965 with the intent of using these data to assess the complications and adverse outcomes (death and/or spinal cord injury) of surgical treatment for spinal deformity. Surgical approaches to the management of treatment of AIS have a measurable impact on efficacy of correction, levels fused, and operative morbidity. However, there is a lack of consensus on the choice of surgical approach for the treatment of spinal deformity. METHODS Of the 58,197 surgical cases submitted by members of the SRS in the years 2001, 2002, and 2003, 10.9% were identified as having had anterior, posterior, or combined spinal fusion with instrumentation for the diagnosis of AIS, and comprised the study cohort. All reported complications were tabulated and totaled for each of the 3 types of procedures, and statistical analysis was conducted. RESULTS Complications were reported in 5.7% of the 6334 patients in this series. Of the 1164 patients who underwent anterior fusion and instrumentation, 5.2% had complications, of the 4369 who underwent posterior instrumentation and fusion, 5.1% had complications, and of the 801 who underwent combined instrumentation and fusion, 10.2% had complications. There were 2 patients (0.03%) who died of their complications. There was no statistical difference in overall complication rates between anterior and posterior procedures. However, the difference in complication rates between anterior or posterior procedures compared to combined procedures was highly significant (P < 0.0001). The differences in neurologic complication rates between combined and anterior procedures, as well as combined and posterior procedures were also highly statistically significant (P < 0.0001), but not between anterior and posterior procedures. CONCLUSIONS This study shows that complication rates are similar for anterior versus posterior approaches to AIS deformity correction. Combined anterior and posterior instrumentation and fusion has double the complication rate of either anterior or posterior instrumentation and fusion alone. Combined anterior and posterior instrumentation and fusion also has a significantly higher rate of neurologic complications than anterior or posterior instrumentation and fusion alone.

Pseudarthrosis in long adult spinal deformity instrumentation and fusion to the sacrum: prevalence and risk factor analysis of 144 cases.

Abstract: Study Design. Retrospective study. Objective. To analyze the incidence of and risk factors for pseudarthrosis in long adult spinal instrumentation and fusion to S1. of Background Data. Few studies on pseudarthrosis in long adult spinal instrumentation and fusion to S1 exist. Methods. A clinical and radiographic assessment of 144 adult patients with spinal deformity (average age 52.0 years; range 21.1-77.6) who underwent long (5-17 vertebrae, average 11.9) spinal instrumentation and fusion to the sacrum at a single institution between 1985 and 2002, with a minimum 2-year follow-up (average 3.9; range 2-14) was performed. Results. Of 144 patients, 34 (24%) had pseudarthroses. There were 17 patients who had pseudarthroses at T10-L2 and 15 at L5-S1. A total of 24 patients (71%) presented with multiple levels involved (2-6). Pseudarthrosis was most commonly detected within 4 years postoperatively (31 patients; 94%). Factors that statistically increased the risk of pseudarthrosis were: thoracolumbar kyphosis (T10-L2 ≥20° vs. <20°, P < 0.0001); osteoarthritis of the hip joint (P = 0.002); thoracoabdominal approach (vs. paramedian approach, P = 0.009); positive sagittal balance ≥5 cm at 8 weeks postoperatively (vs. ≤5cm, P= 0.012); age at surgery older than 55 years (vs. 55 years or younger, P = 0.019); and incomplete sacropelvic fixation (vs. complete sacropelvic fixation, P = 0.020). Fusion from upper thoracic spine (T2-T5) did not statistically increase the pseudarthrosis rate compared to lower thoracic spine (T9-T12) (P = 0.20). Patients with pseudarthrosis had significantly lower Scoliosis Research Society 24 outcome scores (average score 71/120) than those without (average score 90/120; P < 0.0001) at ultimate follow-up. Conclusion. The overall prevalence of pseudarthrosis following long adult spinal deformity instrumentation and fusion to S1 was 24%. Thoracolumbar kyphosis, osteoarthritis of the hip joint, thoracoabdominal approach (vs. paramedian approach), positive sagittal balance ≥5 cm at 8 weeks postoperatively, older age at surgery (older than 55 years), and incomplete sacropelvic fixation significantly increased the risks of pseudarthrosis to an extent that was statistically significant. Scoliosis Research Society 24 outcomes scores at ultimate follow-up were adversely affected when pseudarthrosis developed.

The Oswestry Disability Index, the Roland-Morris Disability Questionnaire, and the Quebec Back Pain Disability Scale: translation and validation studies of the Iranian versions.

Abstract: STUDY DESIGN. Cross-cultural translation and psychometric testing were performed. OBJECTIVES. To cross-culturally translate the Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RDQ), and Quebec Back Pain Disability Scale (QDS) into Persian, and then investigate the psychometric properties of the Persian versions produced. SUMMARY OF BACKGROUND DATA. To the authors' knowledge, there is no validated instrument to measure functional status in Persian-speaking patients with low back pain (LBP) in Iran. To our knowledge, the widely used back-specific measures, the ODI, RDQ, and QDS, have not been translated and validated for Persian-speaking patients with LBP. METHODS. The translation and cross-cultural adaptation of the original questionnaires were performed in accordance with published guidelines. A total of 100 patients with chronic LBP were asked to complete a questionnaire booklet (the Persian versions of the ODI, RDQ, QDS, Short Form Health Survey (SF-36), and visual analog scale measure of pain). There were 31 randomly select patients with chronic LBP asked to complete the second questionnaire booklet 24 hours later. RESULTS. The Cronbach-I± for the ODI, RDQ, and QDS was 0.75, 0.83, and 0.92, respectively. The ODI, RDQ, and QDS showed excellent test-retest reliability (intraclass correlation coefficient = 0.91, 0.86, and 0.86, respectively) (P < 0.01). The correlation among the ODI, RDQ, QDS and physical functioning scales of the SF-36 was -0.66, -0.62, and -0.69, respectively (P < 0.001). The correlation among the ODI, RDQ, and QDS and visual analog scale was 0.54, 0.36, and 0.46, respectively (P < 0.001). CONCLUSIONS. The Persian versions of the ODI, RDQ, and QDS are reliable and valid instruments to measure functional status in Persian-speaking patients with LBP.They are simple and fast scales, and the use of them can be recommended in a clinical setting and future outcome studies in Iran. ©2006, Lippincott Williams & Wilkins, Inc.

Instrumentation-related complications of multilevel fusions for adult spinal deformity patients over age 65 : Surgical considerations and treatment options in patients with poor bone quality

Abstract: Study design Retrospective follow-up of patients over the age of 65 with a minimum of five-level fusions. Objective To determine the effect on outcomes of long constructs in patients with poor bone stock, and to review surgical techniques used in patients with poor bone stock. Summary of background data Scoliotic deformities in patients with poor bone stock require alterations in both the surgical technique and preoperative planning. To our knowledge, complications of long constructs in poor bone stock have not been specifically reported. Method Patients over the age of 65 that underwent a minimum of five-level fusion over a 5-year period were reviewed. We reviewed both operative reports and clinic notes and recorded both early and late complications. Results Early complications included pedicle fractures and compression fractures with an overall rate of 13%. Late complications included pseudarthroses with instrumentation failure, adjacent level disc degeneration with herniation, compression fractures, and progressive kyphosis. Progressive junctional kyphosis occurred in 26% of patients. Conclusions Spinal stabilization surgery in patients with poor bone stock is associated with high complication rates. Complications such as progressive kyphosis adjacent to the fusion are difficult to address with instrumentation alone.

The reliability and construct validity of the Neck Disability Index and patient specific functional scale in patients with cervical radiculopathy.

Abstract: Study design Cohort study of patients with cervical radiculopathy undergoing physical therapy. Objectives Examine the test-retest reliability, construct validity, and minimum levels of detectable and clinically important change for the Neck Disability Index (NDI) and Patient Specific Functional Scale (PSFS) in cohort of patients with cervical radiculopathy. Summary of background data To date, no studies have investigated the psychometric properties of the NDI or PSFS in a cohort of patients with cervical radiculopathy. Methods Thirty-eight patients with cervical radiculopathy undergoing physical therapy completed the NDI and PSFS, and Numerical Pain Rating Scale (NPRS) at the baseline examination and at a follow-up. In addition, at follow-up, patients completed a 15-point global rating of change (GROC), which was used to dichotomize patients as improved or stable. Changes in the NDI and PSFS were then used to assess test-retest reliability, construct validity, and minimal levels of detectable and clinically important change. Results Test-retest reliability was moderate for the NDI (intraclass correlation coefficient [ICC] = 0.68; 95% confidence interval [CI], 0.30-0.90) and high for the PSFS (ICC = 0.82; 95% CI, 0.54-0.93). The PSFS was more responsive to change than the NDI. The minimal detectable change for the NDI was 10.2 and for the PSFS 2.1. The minimally clinically important change for the NDI was 7.0 and PSFS 2.0. Conclusions Our results suggest that the PSFS exhibits superior reliability, construct validity, and responsiveness in this cohort of patients with cervical radiculopathy compared with the NDI. Further research is needed to examine the ability of these measures to accurately reflect changes in individuals, as well as large samples of patients.

Balloon kyphoplasty and vertebroplasty for vertebral compression fractures: a comparative systematic review of efficacy and safety.

Abstract: Study design Systematic review and meta-regression. Objectives To compare the efficacy and safety of balloon kyphoplasty and vertebroplasty for the treatment of vertebral compression fractures, and to examine the prognostic factors that predict outcome. Summary of background data A previous systematic review of vertebroplasty by Levine et al in 2000 identified seven case series studies and no controlled studies. Methods A number of electronic databases were searched through March 1, 2004. Citation searches of included studies were undertaken and contact was made with experts in the field. No language restrictions were applied. All controlled and uncontrolled studies were included with the exception of case reports. Prognostic factors responsible for pain relief and cement leakage were examined using meta-regression. Results The following studies were included: balloon kyphoplasty (three nonrandomized comparative studies against conventional medical therapy and 13 case series), vertebroplasty (one nonrandomized comparative study against conventional medical care and 57 cases series), balloon kyphoplasty versus vertebroplasty (one nonrandomized comparative study). The majority of studies were undertaken in older women with osteoporotic vertebral compression fractures with long-term pain that was refractory to medical treatment. At this time, there is no good quality direct comparative evidence of balloon kyphoplasty versus vertebroplasty. From indirect comparison of case series evidence, the procedures appear to provide similar gains in pain relief while for balloon kyphoplasty there is better documentation of gains in patient functionality and quality of life. The level of cement leakage and number of reported adverse events (pulmonary emboli and neurologic injury) in balloon kyphoplasty was significantly lower than for vertebroplasty. These findings were confirmed by meta-regression analysis. Conclusions There is Level III evidence to support balloon kyphoplasty and vertebroplasty as effective therapies in the management of patients with symptomatic osteoporotic vertebral compression fractures refractory to conventional medical therapy. Although there was a good ratio of benefit to harm for both procedures, balloon kyphoplasty appears to offer the better adverse event profile. These conclusions need to be updated on the basis of the findings of ongoing randomized controlled trials.

Differences in sitting postures are associated with nonspecific chronic low back pain disorders when patients are subclassified.

Abstract: Study Design. A comparative study. Objectives. To investigate sitting postures of asymptomatic individuals and nonspecific chronic low back pain (NS-CLBP) patients (pooled and subclassified) and evaluate the importance of subclassification. Summary of Background. Currently, little evidence exists to support the hypothesis that CLBP patients sit differently from pain-free controls. Although classifying NS-CLBP patients into homogeneous subgroups has been previously emphasized, no attempts have been made to consider such groupings when examining seated posture. Methods. Three angles (sacral tilt, lower lumbar, and upper lumbar) were measured during “usual” and “slumped” sitting in 33 NS-CLBP patients and 34 asymptomatic subjects using an electromagnetic measurement device. Before testing, NS-CLBP patients were subclassified by two blinded clinicians. Twenty patients were classified with a flexion motor control impairment and 13 with an active extension motor control impairment. Results. No differences were found between control and NS-CLBP (pooled) patients during usual sitting. In contrast, analyses based on subclassification revealed that patients classified with an active extension pattern sat more lordotic at the symptomatic lower lumbar spine, whereas patients with a flexion pattern sat more kyphotic, when compared with healthy controls (F 19.7; df1 2, df2 63, P 0.001). Further, NS-CLBP patients had less ability to change their posture when asked to slump from usual sitting (t 4.2, df 65; P 0.001). Conclusions. Differences in usual sitting posture were only revealed when NS-CLBP patients were subclassified. This highlights the importance of subclassifying NS-CLBP patients.

Long-term results of expansive open-door laminoplasty for cervical myelopathy - Average 14-year follow-up study

Abstract: Study design Retrospective case series on long-term follow-up results of original expansive open-door laminoplasty for cervical myelopathy due to cervical spondylosis (CSM) and ossification of posterior longitudinal ligament (OPLL). Objectives To elucidate efficacy and problems of original open-door laminoplasty to improve future surgical outcomes. Summary of background data Little information is available on long-term outcomes of original open-door laminoplasty without grafts, implants, or instruments. Method The study group included 80 patients who underwent original open-door laminoplasty and were followed for minimum 10 years. Clinical results, including Japanese Orthopedic Association scores, recovery rates, occurrences of complications, and long-term deterioration were investigated. Cervical alignments, type of OPLL, cervical range of motion, anteroposterior diameter of spinal canal, and progression of OPLL were assessed on plain radiographs. Spinal cord decompression was verified on magnetic resonance imaging. Results Average Japanese Orthopedic Association score and recovery rate improved significantly until 3 years after surgery and remained at an acceptable level in both cervical spondylosis and OPLL patients with slight deterioration after 5 years. Segmental motor palsy developed in 8 patients. Late deterioration, mainly lower extremity motor score decline, developed in 8 CSM and 16 OPLL patients. Overall cervical range of motion decreased by 36%. Patients with cervical lordosis decreased gradually in both patient groups. Such changes in alignments did not affect surgical results in CSM patients, while OPLL patients with preoperative kyphosis had lower recovery rates than those with straight and lordotic alignments. OPLL progression that was detected in 66% of patients did not affect clinical results. Although infrequent, magnetic resonance imaging revealed atrophy of spinal cord, spinal cord compression at adjacent segments due to degenerative changes and OPLL progression. Conclusions Long-term results of open-door laminoplasty without bone graft, graft substitutes, or instruments were satisfactory. However, segmental motor paralysis, kyphosis, established before and after surgery, OPLL progression, and late deterioration due to age-related degeneration remain challenging problems.

Minimum 5-year analysis of L5-S1 fusion using sacropelvic fixation (bilateral S1 and iliac screws) for spinal deformity.

Abstract: STUDY DESIGN Clinical radiographic and outcomes investigation. OBJECTIVE To investigate clinical and radiographic outcomes for lumbosacral fusion (in patients with spinal deformity) using a combination of bilateral sacral and iliac screws with a minimum 5-year follow-up. SUMMARY OF BACKGROUND DATA To our knowledge, long-term results (>5 years of follow-up) of bilateral S1 screw/bilateral iliac screw fixation have never been published or presented. MATERIALS AND METHODS A total of 67 patients (from an initial consecutive cohort of 81) undergoing lumbosacral fusion with bilateral sacral and iliac screws with a minimum follow-up of 5 years (range 5-10 + 5, average 6 + 3) were analyzed for radiographic outcome and clinical course by an outcome questionnaire (administered at ultimate follow-up) analysis. Patients were divided into 2 groups: group 1, 34 patients with mostly high-grade spondylolisthesis; and group 2, 33 with adult scoliosis fused mostly from the thoracic spine to the sacrum. A true anteroposterior pelvis film was obtained in all patients to assess for sacroiliac joint arthritis, as were standard spine radiographs. Patients were administered Oswestry and directed buttock pain questionnaires at latest follow-up. RESULTS There were no cases of sacral screw failure (i.e., screw loosening, partial screw pullout, or fracture of the sacral screw). There were 5 cases of nonunion at L5-S1. Of the 5 cases, 3 did not have anterior column support at L5-S1. Four of the 5 cases were revised, and, subsequently, 3 achieved union. Iliac screws were removed electively on 1 or both sides in 23 of the patients after 2 years postoperatively because of prominence. There were 7 cases of iliac screw breakage. Iliac screw halos were observed in 29 patients. No sacroiliac osteoarthritis was observed on the true anteroposterior pelvis films. At ultimate follow-up, average visual analog painscale (0-10) score to assess buttock pain was 2.4, and average Oswestry score was 20.1. CONCLUSIONS For high-grade spondylolisthesis and long adult deformity fusions to the sacrum, a montage of bilateral S1 screws and iliac screws were effective in protecting the sacral screws from failure. Pseudarthrosis at L5-S1 was manifested by rod breakage at that level. We saw no evidence of a long-term effect of the iliac screws predisposing the sacroiliac joints to degeneration at follow-up ranging from 5 to 10 years.

Rapid Atrophy of the Lumbar Multifidus Follows Experimental Disc or Nerve Root Injury

Abstract: Study Design Experimental study of muscle changes after lumbar spinal injury Objectives To investigate effects of intervertebral disc and nerve root lesions on cross-sectional area, histology and chemistry of porcine lumbar multifidus Summary of Background Data The multifidus cross-sectional area is reduced in acute and chronic low back pain Although chronic changes are widespread, acute changes at 1 segment are identified within days of injury It is uncertain whether changes precede or follow injury, or what is the mechanism Methods The multifidus cross-sectional area was measured in 21 pigs from L1 to S1 with ultrasound before and 3 or 6 days after lesions: incision into L3 - L4 disc, medial branch transection of the L3 dorsal ramus, and a sham procedure Samples from L3 to L5 were studied histologically and chemically Results The multifidus cross-sectional area was reduced at L4 ipsilateral to disc lesion but at L4 - L6 after nerve lesion There was no change after sham or on the opposite side Water and lactate were reduced bilaterally after disc lesion and ipsilateral to nerve lesion Histology revealed enlargement of adipocytes and clustering of myofibers at multiple levels after disc and nerve lesions Conclusions These data resolve the controversy that the multifidus cross-sectional area reduces rapidly after lumbar injury Changes after disc lesion affect 1 level with a different distribution to denervation Such changes may be due to disuse following reflex inhibitory mechanisms

Transforaminal posterolateral endoscopic discectomy with or without the combination of a low-dose chymopapain: a prospective randomized study in 280 consecutive cases.

Abstract: STUDY DESIGN: A prospective randomized study involving 280 consecutive cases of lumbar disc herniation managed either by an endoscopic discectomy alone or an endoscopic discectomy combined with an intradiscal injection of a low dose (1000 U) of chymopapain. OBJECTIVE: To compare outcome, complications, and reherniations of both techniques. SUMMARY OF BACKGROUND DATA: Despite a low complication rate, posterolateral endoscopic nucleotomy has made a lengthy evolution because of an assumed limited indication. Chemonucleolysis, however, proven to be safe and effective, has not continued to be accepted by the majority in the spinal community as microdiscectomy is considered to be more reliable. METHOD: A total of 280 consecutive patients with a primary herniated, including sequestrated, lumbar disc with predominant leg pain, was randomized. A clinical follow-up was performed at 3 months, and at 1 and 2 years after the index operation with an extensive questionnaire, including the visual analog scale for pain and the MacNab criteria. The cohort integrity at 3 months was 100%, at 1 year 96%, and at 2 years 92%. RESULTS: At the 3-month evaluation, only minor complications were registered. At 1-year postoperatively, group 1 (endoscopy alone) had a recurrence rate of 6.9% compared to group 2 (the combination therapy), with a recurrence rate of 1.6%, which was a statistically significant difference in favor of the combination therapy (P = 0045). At the 2-year follow-up, group 1 reported that 85.4% had an excellent or good result, 6.9% a fair result, and 7.7% were not satisfied. At the 2-year follow-up, group 2 reported that 93.3% had an excellent or good result, 2.5% a fair result, and 4.2% were not satisfied. This outcome was statistically significant in favor of the group including chymopapain. There were no infections or patients with any form of permanent iatrogenic nerve damage, and no patients had a major complication. CONCLUSIONS: A high percentage of patient satisfaction could be obtained with a posterior lateral endoscopic discectomy for lumbar disc herniation, and a statistically significant improvement of the results was obtained when an intradiscal injection of 1000 U of chymopapain was added. There was a low recurrence rate with no major complications. The method can be applied in any type of lumbar disc herniation, including the L5-S1 level.

Possible pathogenesis of painful intervertebral disc degeneration.

Abstract: Study design We collected the specimens of lumbar intervertebral disc (i.e., the symptomatic degenerative disc) from patients with discogenic low back pain to study the histopathologic features and growth factor expressions. Objectives To study the pathogenesis of disc degeneration, meanwhile discriminating between common disc degeneration (aging disc) (i.e., black asymptomatic disc, not clinically relevant) and painful disc degeneration (i.e., symptomatic disc, clinically relevant). Summary of background data The pathogenesis of intervertebral disc degeneration is poorly understood, mainly because of the difficulty to establish the experimental model with good reproducibility. Recently, the popularity of spinal fusion leads to more opportunities to obtain disc specimens, which could be applied to explore the pathogenesis of disc degeneration with modern biologic techniques. Methods There were 21 specimens of lumbar intervertebral discs from 15 patients with discogenic low back pain during posterior lumbar interbody fusion, 16 aging discs from patients without low back pain, and 10 normal discs as control collected for the study of their histopathologic features, as well as the expressions of basic fibroblast growth factor (bFGF) and its receptor (Flg), transforming growth factor-beta1 (TGF-beta1) and its receptor (TGF-betaRI) by immunohistochemistry. The distribution of macrophages and mast cells was also noted. Proliferating cell nuclear antigen was assessed to evaluate proliferating activities of disc cells. Results The distinct histologic characteristic of the disc from the patient with discogenic low back pain was the ingrowth of vascularized granulation tissue along torn fissures, extending from the external layer of the anulus fibrosus into the nucleus pulposus. The immunohistochemical staining showed that there were strong expressions of bFGF and TGF-beta1 and their receptors, as well as a strong expression of proliferating cell nuclear antigen in the zones of granulation tissue in the painful discs. However, there were only weak expressions in the nongranulation tissue zones in the painful discs and aging discs, and no expression in the control discs. In addition, abundant macrophages and mast cells were found in the granulation tissue zones of painful discs but absent in the nongranulation tissue zones of painful discs or aging discs and the normal control discs. Conclusions The findings indicated that degeneration of the painful disc might originate from the injury and subsequent repair of anulus fibrosus. Growth factors, such as bFGF and TGF-beta1, macrophages and mast cells might play a key role in the repair of the injured anulus fibrosus and subsequent disc degeneration.

Minimal clinically important change for pain intensity, functional status, and general health status in patients with nonspecific low back pain.

Abstract: Study Design. Cohort study. Objectives. To estimate the Minimal Clinically Important Change (MCIC) of the pain intensity numerical rating scale (PI-NRS), the Quebec Back Pain Disability Scale (QBPDS), and the Euroqol (EQ) in patients with low back pain. Summary of Background Data. MCIC can provide valuable information for researchers, healthcare providers, and policymakers. Methods. Data from a randomized controlled trial with 442 patients with low back pain were used. The MCIC was estimated over a 12-week period, and three different methods were used: 1) mean change scores, 2) minimal detectable change, and 3) optimal cutoff point in receiver operant curves. The global perceived effect scale (GPE) was used as an external criterion. The effect of initial scores on the MCIC was also assessed. Results. The MCIC of the PI-NRS ranged from 3.5 to 4.7 points in (sub)acute patients and 2.5 to 4.5 points in chronic patients with low back pain. The MCIC of the QBPDS was estimated between 17.5 to 32.9 points and 8.5 to 24.6 points for (sub)acute and chronic patients with low back pain. The MCIC for the EQ ranged from 0.07 to 0.58 in (sub)acute patients and 0.09 to 0.28 in patients with chronic low back pain. Conclusion. Reporting the percentage of patients who have made a MCIC adds to the interpretability of study results. We present a range of MCIC values and advocate the choice of a single MCIC value according to the specific context. ©2006, Lippincott Williams & Wilkins, Inc.

An MRI investigation into the function of the transversus abdominis muscle during "drawing-in" of the abdominal wall.

Abstract: Study Design. An operator blinded dual modality trial of measurement of the abdominal muscles during "drawing-in" of the abdominal wall. Objectives. 1) To investigate, using magnetic resonance imaging (MRI), the function of the transversus abdominis muscle bilaterally during a drawing-in of the abdominal wall. 2) To validate the use of real-time ultrasound imaging as a measure of the deep abdominal muscle during a drawing-in of the abdominal wall. Summary of Background Data. Previous research has implicated the deep abdominal muscle, transversus abdominis, in the support and protection of the spine and provided evidence that training this muscle is important in the rehabilitation of low back pain. One of the most important actions of the transversus abdominis is to "draw-in" the abdominal wall, and this action has been shown to stiffen the sacroiliac joints. It is hypothesized that in response to a draw in, the transversus abdominis muscle forms a deep musculofascial "corset" and that MRI could be used to view this corset and verify its mechanism of action on the lumbopelvic region. Methods. Thirteen healthy asymptomatic male elite cricket players aged 21.3 ± 2.1 years were imaged using MRI and ultrasound imaging as they drew in their abdominal walls. Measurements of the thickness of the transversus abdominis and internal oblique muscles and the slide of the anterior abdominal fascia were measured using both MRI and ultrasound. Measurement of the whole abdominal cross-sectional area (CSA) was conducted using MRI. Results. Results of the MRI demonstrated that, as a result of draw-in, there was a significant increase in thickness of the transversus abdominis (P

Clinical outcomes and fusion success at 2 years of single-level instrumented posterolateral fusions with recombinant human bone morphogenetic protein-2/compression resistant matrix versus iliac crest bone graft.

Abstract: Study design This is a prospective, randomized study comparing iliac crest bone graft to bone morphogenetic protein (BMP)/compression resistant matrix in instrumented posterolateral fusions for single-level lumbar degenerative disease. A higher recombinant human bone morphogenetic protein (rhBMP)-2 dose and a carrier specific for posterior spine applications were used. Objectives As part of a Food and Drug Administration IDE study, clinical outcomes and fusion rates of single-level instrumented posterolateral fusions using iliac crest bone graft or BMP/compression resistant matrix were evaluated. Summary of background data Although iliac crest graft is the gold standard for lumbar fusion, alternatives to obviate the morbidity of graft harvest have become available. Randomized clinical trials have demonstrated equivalent fusion rates and clinical outcomes with rhBMP-2 and a collagen sponge versus autograft in anterior lumbar fusions. A human pilot study using rhBMP-2 with biphasic calcium phosphate demonstrated similar results for posterolateral fusions. Methods Demographic and perioperative data, Short Form 36, Oswestry Low Back Pain Disability Index, and leg and back pain scores were determined before surgery, and 1.5, 3, 6, 12, and 24 months after surgery. Independent neuroradiologists' evaluation of fine-cut computerized tomography scans with reconstructions were obtained at 6, 12, and 24 months. Results There were 98 subjects, 45 in the iliac crest bone graft group and 53 in the BMP/compression resistant matrix group. There were no significant differences for age, weight, sex, smoking, or previous surgery between the groups. The average operative time (2.9 hours) and blood loss (465 cc) in the iliac crest bone graft group was greater than in the BMP/compression resistant matrix group (2.4 hours and 273 cc). There were no significant differences in any outcome measure at all time intervals. The fusion rate was lower in the iliac crest bone graft group (73%) than in the BMP/compression resistant matrix group (88%) at P = 0.051. Conclusion There was significant improvement of Short Form 36 (physical component score and pain), Oswestry Low Back Pain Disability Index, and leg and back pain scores in both groups over all time intervals. Surgical time and blood loss were significantly less in the BMP/compression resistant matrix group. The fusion rate in the BMP/compression resistant matrix group was significantly higher than the iliac crest bone graft group.

Treatment of traumatic thoracolumbar spine fractures: a multicenter prospective randomized study of operative versus nonsurgical treatment.

Abstract: Study Design. Multicenter prospective randomized trial. Objective. To test the hypotheses that thoracolumbar AO Type A spine fractures without neurologic deficit, managed with short-segment posterior stabilization will show an improved radiographic outcome and at least the same functional outcome as compared with nonsurgically treated thoracolumbar fractures. Summary of Background Data. There are various opinions regarding the ideal management of thoracolumbar Type A spine fractures without neurologic deficit. Both operative and nonsurgical approaches are advocated. Methods. Patients were randomized for operative or nonsurgical treatment. Data sampling involved demographics, fracture classifications, radiographic evaluation, and functional outcome. Results. Sixteen patients received nonsurgical therapy, and 18 received surgical treatment. Follow-up was completed for 32 (94%) of the patients after a mean of 4.3 years. At the end of follow-up, both local and regional kyphotic deformity was significantly less in the operatively treated group. All functional outcome scores (VAS Pain, VAS Spine Score, and RMDQ-24) showed significantly better results in the operative group. The percentage of patients returning to their original jobs was found to be significantly higher in the operative treated group. Conclusions. Patients with a Type A3 thoracolumbar spine fracture without neurologic deficit should be treated by short-segment posterior stabilization.

Effect of different upright sitting postures on spinal-pelvic curvature and trunk muscle activation in a pain-free population.

Abstract: Study design: A normative within-subjects single-group study. Objective: To compare spinal-pelvic curvature and trunk muscle activation in 2 upright sitting postures ("thoracic" and "lumbo-pelvic") and slump sitting in a pain-free population. Summary of background data: Clinical observations suggest that both upright and slump sitting postures can exacerbate low back pain. Little research has investigated the effects of different upright sitting postures on trunk muscle activation. Methods: Spinal-pelvic curvature and surface electromyography of 6 trunk muscles were measured bilaterally in 2 upright (thoracic and lumbo-pelvic) sitting postures and slump sitting in 22 subjects. Results: Thoracic, compared to lumbo-pelvic, upright sitting showed significantly greater thoracic extension (P < 0.001), with significantly less lumbar extension (P < 0.001) and anterior pelvic tilt (P = 0.03). Furthermore, there was significantly less superficial lumbar multifidus (P < 0.001) and internal oblique (P = 0.03) activity, with significantly higher thoracic erector spinae (P < 0.001) and external oblique (P = 0.04) activity in thoracic upright sitting. There was no significant difference in superficial lumbar multifidus activity between thoracic upright and slump sitting. Conclusions: Different upright sitting postures resulted in altered trunk muscle activation. Thoracic when compared to lumbo-pelvic upright sitting involved less coactivation of the local spinal muscles, with greater coactivation of the global muscles. These results highlight the importance of postural training specificity when the aim is to activate the lumbo-pelvic stabilizing muscles in subjects with back pain.

A randomized controlled trial investigating the efficiency of musculoskeletal physiotherapy on chronic low back disorder

Abstract: Study design Randomized, single blind, controlled trial. Objective To determine the efficacy of 2 components of musculoskeletal physiotherapy on chronic low back disorder. Summary of background data Musculoskeletal physiotherapy encompasses many treatment methods, however, manual therapy and exercises to rehabilitate spinal stabilization are the most frequently used. Despite their popularity, scant evidence supports their use on subjects with chronic low back disorder. Methods A total of 346 subjects were randomized to manual therapy, a 10-week spinal stabilization rehabilitation program, or a minimal intervention control group. Data were collected at baseline, and 3, 6, 12, and 24 months after intervention. Outcome measures recorded intensity of low back pain, disability, handicap, medication, and quality of life. There were 4 main variables combined in a primary component analysis to form a single outcome measure (i.e., a measure of dysfunction). Results The results indicated statistically significant improvements in favor of the spinal stabilization group at the 6-month stage in pain (65.9% reduction in symptoms) and dysfunction (combined mean reduction of 134, standard error 23.84), and at the 1-year stage in medication (34.3% reduction in medication), dysfunction (combined mean reduction of 134, standard error 18.2), and disability (mean difference in change 15.71 Oswestry Disability Index, 95% confidence interval 19.3-10.01). Conclusions As a component of musculoskeletal physiotherapy, the spinal stabilization program is more effective than manually applied therapy or an education booklet in treating chronic low back disorder over time. Both manual therapy and the spinal stabilization program are significantly effective in pain reduction in comparison to an active control. To our knowledge and up until now, this result has not been shown in patients with chronic low back disorder.