The Evaluation of the Surgical Management of Nerve Root Compression in Patients with Low Back Pain

Transcription

1 The Evaluation of the Surgical Management of Nerve Root Compression in Patients with Low Back Pain Part 1: The Assessment of Outcome Alison H. McGregor, PhD, and Sean P. F. Hughes, MS, FRCS SPINE Volume 27, Number 13, pp , Lippincott Williams & Wilkins, Inc. Study Design. This was a prospective study investigating the outcome of decompression surgery using validated measures of outcome. Objectives. To investigate the outcome of lumbar decompressive surgery in the initial postoperative year period in terms of function, disability, general health, and psychological well-being. Summary of Background Data. The majority of studies investigating the outcome of lumbar decompression surgery have been retrospective and have not used validated measures of outcome. This limits their interpretation and usefulness. Methods. Eighty-four patients undergoing lumbar spinal stenosis surgery were recruited into this study. Patients were assessed by use of validated measures of outcome including the Oswestry Disability Index and the Short Form SF-36 General Health Questionnaire before surgery and 6 weeks, 6 months, and 1 year after surgery. Results. A significant reduction in pain (P 0.001) was observed at the 6-week postoperative stage; this did not change at the subsequent assessment stages. Only some of the SF-36 categories were sensitive to change. The subcategories that were sensitive to change were physical function (P 0.05), bodily pain (P 0.001), and social function (P 0.05). Improvements were observed in these categories at the 6-week and 6-month reviews. A gradual reduction in the Oswestry Disability Index was observed with time, with changes principally being observed between the 6-week and 6-month review and the 6-week and 1-year review stages (P 0.05). Minimal changes were observed in the psychological assessments with time. The outcome of surgery could not be predicted reliably from psychological, functional, or pain measures. Conclusions. The visual analogue pain scales, the Oswestry Disability Index, and certain categories of the SF-36 Questionnaire, namely bodily pain and physical and social function, appeared to be the most sensitive outcome measures, with significant improvements occurring at the 6-week and 6-month reviews. [Key words: nerve root compression, surgery, outcome, Oswestry disability index, SF-36 General Health Questionnaire, pain] Spine 2002;27: From the Department of Musculoskeletal Surgery, Division of Surgery, Anaesthetics and Intensive Care, Faculty of Medicine, Imperial College of Science, Technology and Medicine, Charing Cross Hospital, London, U.K. Supported by the NHS Executive London, Research & Development Programme. The views expressed in the publication are those of the authors and not necessarily those of the NHS Executive or the Department of Health. Acknowledgment date: June 19, First revision date: September 4, Second revision date: November 28, Acceptance date: February 28, Device Status/Drug Statement: The manuscript submitted does not contain information about medical device(s)/drug(s). Conflict of Interest: NHS funds were received to support this work. No benefits in any form have been or will be received from a commercial party related directly or indirectly to the subject of this manuscript. Musculoskeletal conditions are among the most common medical conditions with a substantial influence on health, quality of life and use of resources. 15 Low back pain affects from 60% to 80% of the population at some point in their lives, 28 creating an annual bill of more than 480 million to the National Health Service in the United Kingdom. Although only 0.5% of patients with low back pain require surgical intervention, inpatient treatment forms the largest single component of overall expense. 23 Lumbar spinal stenosis is a major cause of low back and lower extremity discomfort and disability, requiring surgical intervention in elderly patients. 4 It is a disabling syndrome that results from chronic compression of the spinal nerves by degenerative hypertrophic lesions of the facet joints, and ligamentum flavum and degeneration of the intervertebral disc. Conservative treatment options seldom result in sustained improvements, and thus surgical decompression is the main option for these patients. 2,20 The aim of surgery is to relieve pain and restore function by decompressing the stenotic area and restoring neural function. The outcome of this type of intervention is varied. 1,2,3,4,12,16,17,19,20,21,33,37,38 This can be attributed in part to inadequate study designs, small study populations, poor outcome measures, and a tendency for the studies to be prospective. In addition, many studies have not used validated outcome measures and have not considered patient-oriented views of outcome. Turner et al 38 conducted a meta-analysis of the published literature and reported a success rate ranging between 26% and 100%, a range similar to that reported by Airaksinen et al 1 in The primary aim of the proposed study was to prospectively evaluate the outcome of decompression surgery in patients with lateral and central canal stenosis as a result of degenerative changes in terms of objective and subjective patient-oriented measures of outcome. Methods Study Population. All patients coming to the Spinal Clinics at the Charing Cross Hospital with signs, symptoms, and radiographic and magnetic resonance imaging findings of nerve root compression (of either central or lateral canal origin) as a result of degenerative changes were eligible for inclusion in this study. Written informed consent was obtained from all patients. A total of 84 patients (41 women, 43 men; mean age, years) out of a potential 135 were recruited into this study between September 1997 and September 1999 on their attendance at the preadmission clinic held 6 weeks before admission to the hospital for surgery, and all baseline measures were obtained at this time point. Of the 51 patients who did not take place in the study, 35 declined participation, and the remainder 1465

2 1466 Spine Volume 27 Number were excluded on account of their age (more than 80 years), language problems, confused state of mind, and coexisting pathologic conditions. Twenty-four of the 84 patients had had previous surgery, 15 had had previous decompression surgery, and the remaining 9 had had a discectomy. Of the patients recruited, 77 underwent surgery, and the remaining 7 patients opted not to go through with surgery but chose a conservative management approach. Seventy-two patients (86% of the original population) were reassessed at 6 weeks, 68 (81%) were reviewed at 6 months, and 65 patients (77%) completed their 1-year review. When possible, reviews were performed during the patient s postoperative follow-up appointments at the clinic; if patients were unable to attend, questionnaires were mailed to them for completion. Review assessments were performed by an independent observer, and the questionnaires were completed by the patient. Dropout from the study was primarily a result of patients either moving out of the area or returning to full-time employment and having insufficient time to complete the study. Surgical Procedure. All the patients underwent posterior decompression surgery; 83% underwent bilateral decompression, and the remainder underwent a unilateral decompression. Five patients also underwent a fusion with instrumentation. Seventy-seven percent of patients had two or more levels decompressed, and the remainder had only one level decompressed. Clinical Assessment of Patients. All patients were asked to complete a form detailing anamnestic information. They were asked to identify their pain sites on a pain drawing 29 and to rate their current resting pain levels and their worst and usual pain levels over the past week on a 10-cm visual analogue scale. Back and leg pain were considered separately (although not broken down into unilateral or bilateral pain), and the mean value of current, worse, and usual pain was used at each analysis stage. In addition, patients completed the Short Form SF-36 Health Survey Questionnaire (SF-36), a validated general health questionnaire 5,13 that documents functional status, well-being, and patients overall evaluation of their health as a percentage score, with 100% representing the best possible function and 0% the worst possible function, and the Oswestry Disability Index (ODI), 11 a disease-specific questionnaire designed for use in patients with low back pain that evaluates the patient s overall level of functional disability in terms of a percentage score, with higher values representing higher levels of disability. Psychologic Evaluation of Patients. A variety of psychological questionnaires were included in the protocol for completion at each assessment phase. They included the Positive Affect Negative Affect Scale, 39 which provided a measure of positive and negative mood states; the Cantril Life Satisfaction Ladder, 6 the Helplessness subscale of the Rheumatology Attitudes Index, 8 the six-item short form state scale of the Spielberger State-Trait Anxiety Inventory, 27 the Symptom Check List Depression and Somatic Subscales SCL-90R, 31 which provide measures of depressive and somatic symptoms, and visual analogue scales of fatigue. Statistical Analysis. All statistical analysis was performed on the statistical package STATA (Stata Corp., TX, USA) on a Figure 1. Changes in average back and leg pain with time (all values %, mean and standard deviation). personal computer. A two-way analysis of variance (ANOVA) was used to assess changes in the key outcome variables at each stage of the study. The normality of the data was assessed using normality plots and the Franco Shapiro test, and the Bartlett s test was used to test for equal variances. A series of covariates were considered in the ANOVA in terms of their influence on outcome, including age, sex, duration of symptoms, preoperative wait, whether or not the patient was a smoker, and whether this was primary or secondary spinal surgery. However, these covariates were noted to have no influence on the outcome and were consequently dropped from the ANOVA. Orthogonal contrasts were used to assess where any differences detected lay. Further statistical analysis was performed to identify which outcome variables were associated with a successful outcome at 1 year. Initially the correlations between the outcome variable and all the potential predictor variables were assessed. The variables identified as being significantly correlated with the outcome at 1 year and the initial presenting value of that outcome, as well as whether or not this was the patient s initial or second operation, were placed in a backwards stepwise regression procedure. The residuals of the resulting regression equation were then checked for normality by use of residual plots and the Franco Shapiro Test. Results Pain The ANOVA revealed a significant reduction in average (i.e., average of worst, typical, and usual pain) back and leg pain (P 0.001). As can be seen in Figure 1, significant improvement was observed only when all review stages were compared with the preoperative values of back and leg pain, suggesting that little improvement in pain is observed after the 6-week postoperative stage. Thus, pain at 6 weeks appeared to be reflective of pain at 1 year. SF-36 General Health Questionnaire Table 1 summarizes the changes recorded in the SF-36 at each assessment stage. For each category, a higher score represents a better health status, 100% being indicative of normal function. The ANOVA revealed that only some of the SF-36 categories were sensitive to change. The subcategories that were sensitive to change were physical function (P 0.05), bodily pain (P 0.001),

3 Surgical Management of Nerve Root Compression McGregor and Hughes 1467 Table 1. Changes in the Short Form 36 at Each Assessment Interval Category Initial 6 Weeks Postop 6 Months Postop 1 Year Postop Physical function Role physical Bodily pain General health Vitality Social function Role emotional Mental function All values %, mean and standard deviation Figure 2. Changes in Oswestry Disability Index with time (all values %, mean and standard deviation). and social function (P 0.05). Orthogonal contrasts revealed that with respect to physical function, significant improvements were observed only between the initial and 6-month assessment periods (P 0.05). Bodily pain, however, improved significantly at all review stages when compared with the initial score (P 0.001). Significant improvements were also observed between the 6-week and 6-month reviews and the 6-week and 1 year reviews (P 0.05). Significant improvements in social function were observed at 6 months and 1 year in comparison with the initial and 6-week postoperative stages (P 0.05). Oswestry Disability Index A gradual reduction in the ODI was observed with time (higher percentage scores represent greater levels of disability, with 100% representing full function) (Figure 2). ANOVA revealed that this was a significant improvement (P 0.01), with changes principally being observed between the 6-week and 6-month reviews and the 6-week and 1-year reviews (P 0.05). Psychologic Variables As can be seen in Table 2, changes in most of the recorded psychological categories were small (higher scores signify higher levels of life satisfaction, fatigue, depression and somatization, mood, and well-being). Helplessness was the only score in which a statistically significant change was noted (P 0.001), with all review stages demonstrating significant improvement with respect to the initial presenting levels (P 0.01). No differences were observed between the three review stages. Factors Associated with Successful Outcome at 1 Year The outcome of pain measures (average back and leg pain, and SF-36 bodily pain), i.e., the change in these measures between initial presentation and final review, were all associated with the patient s physical function at the time of initial presentation (P 0.01). SF-36 bodily pain was also negatively associated with previous surgery, fatigue, and the somatic subscale and positively associated with ODI. Factors such as depression and mood did not appear to influence outcome in pain. Measures of outcome in function such as the ODI and SF-36 physical function and role physical categories were all associated (P 0.05) with the somatic subscale and presenting SF-36 physical function. However, there appeared to be little consistency between each of the outcome measures. Previous surgery was associated with many outcome measures, includ- Table 2. Changes in Psychologic Outcome Criteria With Time Assessment Scale Initial 6 Weeks Postop 6 Months Postop 1 Year Postop PANAS positive affect PANAS negative affect Anxiety score Helplessness Depression subscale Somatic subscale Life satisfaction Fatigue All values are means and standard deviations.

4 1468 Spine Volume 27 Number ing bodily pain, fatigue, vitality, and negative mood. Although some of the psychological factors were correlated with each other, this varied considerably between factors, and no consistent pattern was observed. Interestingly, the final anxiety rating was associated only with the patient s ability to work at initial presentation. The regression models generated accounted for only a small percentage (11 50%) of the variability in the data, thus limiting the clinical usefulness of the data. The stronger regression models were generated for predicting psychological welfare, with factors such as helplessness being strongly correlated with SF-36 function and with measures of fatigue and anxiety. Discussion Degenerative lumbar spinal stenosis is a major cause of low back and lower extremity discomfort and disability, requiring surgical intervention. 4 The reported success rates for decompressive surgery for spinal stenosis vary. Many studies report that the procedure is successful in 85% of patients. 12,33,34 A success rate of 70% was reported in one review, 14 whereas a review of papers published between 1966 and 1991 suggested an overall success rate of 64%. 38 A more recent study that used standardized patient-centered measures of outcome reported 67% good to excellent results after 6.8 years of follow-up, 16 and a study with a 4.2-year follow-up suggested a slightly lower success rate of 57%. 20 A recent retrospective study reviewed patients 10 years after surgery and noted that 57% of patients reported a good or excellent result, with only 22% reporting a poor result. 17 A further retrospective study by Cornefjord et al 7 reported a satisfactory outcome in 65% of patients. However, in the majority of these studies the criteria for success were not standardized, and the studies were of a retrospective nature. 30 This study investigated the outcome of spinal surgery using several standard validated outcome measures, including the ODI, the SF-36 General Health Questionnaire, and psychological measures that included measures of mood, depression, anxiety, and helplessness. The ODI and the SF-36 have become standard instruments for assessing outcome in patients with low back pain. In contrast to the study by Tenhula et al, 37 only small improvements in the ODI were noted at the reviews. In the early 6-week postoperative phase, it was not possible to detect any improvements or deterioration in this study population, suggesting that the ODI may not be sensitive enough for detecting a change in function in this subpopulation of patients with low back pain. However, in contrast to some outcome studies of spinal stenosis, baseline measures of the ODI suggested higher levels of disability in this study population. 15 The Maine Lumbar Spine Study 3 used the Roland Scale to assess function and noted significant improvement in function at 1 year, in line with the study of Tenhula et al. 37 However, function was not assessed at 6 weeks and 6 months. Subsequent 5-year follow-up of the patients recruited in the Maine study suggested that improvement reached a plateau after 1 year. 4 Several subcategories of the SF-36 were unable to detect improvements after surgery. Those that appeared to be sensitive to improvements were the physical function, bodily pain, and social function categories. This is in agreement with the findings of Atlas et al, 3,4 Patrick et al, 30 Deyo et al, 9 Taylor et al, 36 and Dionne et al, 10 who noted that pain and physical dimensions and outcome measures based on these characteristics were the most responsive categories to change in symptoms. Visual analogue scales of back and leg pain did appear to be sensitive to change as a result of surgery, with the greatest reduction in pain occurring at 6 weeks. The results suggest that if no improvement in pain has occurred at 6 weeks, then no improvement will be seen at 6 months or 1 year. It is also of interest that the prime aim of decompression surgery is the relief of leg pain; however, this study s findings suggest that there is also a significant improvement in back pain. The regression analysis suggested that changes in pain were associated with significant improvements in function. Previous studies have noted poor correlations between pain and objective measures of function. 25,32,35 There were several limitations in the design of the current study. The principal limitation was the lack of a control group for comparative purposes. At present, little is known about the natural history of spinal stenosis; thus, it is difficult to determine the true long-term effect of such surgery. Future studies aim to address this. In addition, instruments such as the ODI, the Roland Disability Score, and the Quebec Back Pain Disability Scale have been criticized as instruments that assess patient perception and are consequently not necessarily indicative of actual ability. Such self-assessments may be influenced by psychological distress, 26 correlating with emotional and cognitive function rather than with true functional capacities. 24 However, the regression analysis suggested that this was not the case in this study. The ODI has been criticized with respect to its sensitivity. 36 This was not examined in this study. Further limitations were incurred by the patient dropouts at each review stage, the comparatively small study population, and the short follow-up period. Previous studies have suggested that outcome is related to many preoperative factors. These include preoperative constriction of the spinal cord, insignificant low back pain, preoperative duration of less than 4 years, age, a high level of physical activity, and the absence of other conditions affecting walking ability. 18,19 Katz et al 22 suggested that potential predictors of outcome also include sociodemographic factors and physical examination results, along with radiographic, psychological, social, and clinical history. This current study, however, did not account for all these factors. Correlation analysis of the different 1-year outcome measures (i.e., ODI and SF-36) with the preoperative symptoms in this study re-

5 Surgical Management of Nerve Root Compression McGregor and Hughes 1469 vealed that a variety of factors were associated with outcome; however, these varied between the various outcome measures, and no one factor was consistent between all measures. Although previous surgery was found to be an important variable for predicting some aspects of outcome, direct comparisons of outcome in initial surgery patients with outcome in previous surgery patients revealed no statistical differences. This prospective study demonstrated, by use of validated patient-oriented outcome measures, that improvements from spinal decompression are relatively low, particularly with respect to function and psychological well-being. The findings of this study would therefore justify a randomized controlled trial to compare the natural history of spinal stenosis with surgical intervention. Conclusion This prospective study investigating the outcome of decompression surgery for lateral root canal stenosis has provided a series of validated markers of outcome during the first postoperative year. Of the markers assessed, visual analogue pain scales, the ODI, and certain categories of the SF-36 appeared to be the most sensitive to change. The data suggest that prediction of surgical outcome from self-rated measures of function, pain, and psychological well-being could not account for the large variability in outcome observed. Key Points A prospective study of the outcome of lumbar spine decompression surgery used validated outcome measures. Visual analogue pain scales, the Oswestry Disability Index, and the SF-36 General Health Questionnaire appeared to be the most sensitive measures of outcome. Most improvements had occurred by the 6-week and 6-month reviews. Outcome could not be reliably predicted from presurgical measures of function, disability, pain, and psychological well-being. Acknowledgments The authors thank the Orthopaedic Outpatients Department at Charing Cross Hospital for their cooperation with this study and all the patients for their longstanding patience and interest in the study, and Dr. Helena Aarons for her help in setting up the psychologic questionnaires. References 1. Airasksinen O, Herno A, Saari T. Surgical treatment of lumbar spinal stenosis: patients postoperative disability and working capacity. Eur Spine J 1994; 3: Amundsen T, Weber H, Nordal HJ, et al. Lumbar spinal stenosis: Conservative or surgical management? Spine 2000;25: Atlas SJ, Deyo RA, Keller RB, et al. The Maine lumbar spine study, Part II: 1-year outcomes of surgical and non surgical management of sciatica. Spine 1996;21: Atlas SJ, Keller RB, Robson D, et al. Surgical and nonsurgical management of lumbar spinal stenosis. Spine 2000;25: Brazier JE, Harper R, Jones NMB, et al. Validating the SF-36 health survey questionnaire: A new outcome measure for primary care. Br Med J 1992; 305: Cantril H. The Pattern of Human Concerns. New Brunswick, NJ: Rutgers University Press, Cornefjord M, Byrod G, Brisby H, et al. A long-term (4- to 12-year) follow-up study of surgical treatment of lumbar spinal stenosis. Eur Spine J 2000;9: DeVellisRF, Callahan LF. A brief measure of helplessness in rheumatic disease: The helplessness subscale of the rheumatology index. J Rheumatol 1993;20: Deyo RA, Battie M, Beurskens AJ, et al. Outcome measures for low back pain research: A proposal for standardized use. Spine 1998;23: Dionne CE, Von Korff M, Koepsell TD, et al. A comparison of pain, functional limitations, and work status indices as outcome measures in back pain research. Spine 1999;24: Fairbank JCT, Couper J, Davies JB, et al. The Oswestry low back pain disability questionnaire. Physiotherapy 1980;66: Ganz JC. Lumbar spinal stenosis: Postoperative results in terms of preoperative posture related pain. J Neurosurg 1990;72: Garrett A, Ruta D, Abdulla M, et al. The SF-36 health survey questionnaire: an outcome measure suitable for routine use in the NHS? Br Med J 1993; 306: Grabias S. Current concepts review: The treatment of spinal stenosis. J Bone Joint Surg 1980;62A: Heinegard D, Johnell O, Lidgren L, et al. The Bone Joint Decade Acta Orthop Scand 1998;69: Herno A, Airaksinen O, Saari T. Long-term results of surgical treatment of lumbar spinal stenosis. Spine 1993;11: Iguchi T, Kurihara A, Nakayma J, et al. Minimum 10 year outcome of decompressive laminectomy for degenerative lumbar spinal stenosis. Spine 2000;25: Jenis LG, An HS. Spine update: Lumbar foraminal stenosis. Spine 20000;25: Jönsson B, Annertz M, Sjöberg C, et al. A prospective and consecutive study of surgically treated lumbar spinal stenosis: Part II. Five-year follow-up by an independent observer. Spine 1997;22: Katz JN, Lipson SJ, Larson MG, et al. The outcome of decompressive laminectomy for degenerative lumbar spinal stenosis. J Bone Joint Surg 1991; 73A: Katz JN, Lipson SJ, Chang LC, et al. Seven to 10 year outcome of decompressive surgery for degenerative lumbar spinal stenosis. Spine 1996;21: Katz JN, Stucki G, Lipson SJ, et al. Predictors of surgical outcome in degenerative lumbar spinal stenosis. Spine 1999;24: Klaber Moffett J, Richardson G, Sheldon TA, et al. Back Pain: Its Management and Cost to Society. York, UK: Centre for Health Economics, University of York, Kopec JA, Esdaile JM. Functional disability scales for back pain. Spine 1995; 20: McGregor AH, McCarthy ID, Doré C, et al. Are subjective clinical findings and objective clinical tests related to the motion characteristics of low back pain subjects? J Orthop Sports Phys Ther 1998;28: Millard RW, Jones RH. Construct validity of practical questionnaires for assessing disability of low back pain. Spine 1991;16: Marteau TM, Bekker H. The development of a six-item short form of the state scale of the Speilberger State-Trait Anxiety Inventory (STAI). Br J Clin Psychol 1992;31: National Back Pain Association. Annual Report and Teddington, Middlesex, UK. 29. Ohnmeiss DD. Repeatability of pain drawings in a low back pain population. Spine 2000;25: Patrick DL, Deyo RA, Atlas SJ, et al. Assessing health-related quality of life in patients with sciatica. Spine 1995;20: Peveler RC, Fairburn CG. Measurement of neurotic symptoms by self-report questionnaire: Validity of SCL-90R. Psychol Med 1990;20: Poitras S, Loisel P, Prince F, et al. Disability measurement in persons with back pain: A validity study of spinal range of motion and velocity. Arch Phys Med Rehabil 2000;81: Sanderson PL, Wood PLR. Surgery for lumbar spinal stenosis in old people. J Bone Joint Surg 1993;75B:393 7.

6 1470 Spine Volume 27 Number Spengler DM. Degenerative stenosis of the lumbar spine. J Bone Joint Surg 1987;69A: Sullivan MS, Shoaf LD, Riddle DL. The relationship of lumbar flexion to disability in patients with low back pain. Phys Ther 2000;80: Taylor SJ, Taylor AE, Foy MA, et al. Responsiveness of common outcome measures for patients with low back pain. Spine 1999;24: Tenhula J, Lenke LG, Bridwell KH, et al. Prospective functional evaluation of the surgical treatment of neurogenic claudication in patients with lumbar spinal stenosis. J Spinal Disord 2000;13: Turner JA, Erek M, Herron L, et al. Surgery for lumbar spinal stenosis: attempted meta-analysis of the literature. Spine 1992;17: Watson D, Clark LA, Tellegen A. Development and validation of brief measures of positive and negative affect: The PANAS scales. J Pers Soc Psychol 1988;54: Address reprint requests to Alison McGregor, PhD Department of Musculoskeletal Surgery Division of Surgery, Anaesthetics & Intensive Care Faculty of Medicine Imperial College of Science, Technology & Medicine Charing Cross Hospital London W6 8RF a.mcgregor@ic.ac.uk