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© 2000 The Journal of Bone and Joint Surgery, Inc. Long-Term Disability and Return to Work Among Patients Who Have a Herniated Lumbar Disc: The Effect of Disability Compensation* , BOSTON , MANCHESTER, MAINE , SEATTLE, WASHINGTON, BOSTON, MASSACHUSETTSInvestigation performed at the Massachusetts General Hospital, Boston, the Maine Medical Assessment Foundation, Manchester, and the Center for Cost and Outcomes Research and Departments of Health Services and Medicine, University of Washington, Seattle
Background: Low-back problems are one of the most frequent reasons for disability compensation claims by workers. However, the effect of Workers' Compensation status on the long-term outcome for workers with sciatica has not been studied in detail, to our knowledge. Therefore, we believe that it is important to describe the long-term outcomes for patients who have herniation of a lumbar disc and sciatica according to the Workers' Compensation status at the time of the preoperative consultation. Methods: We conducted a prospective, observational study of patients who had sciatica and were seeking care from specialist physicians in community-based practices throughout Maine. Among 440 eligible patients, 199 were receiving Workers' Compensation at the time of entry into the study (baseline) and 241 were not. Three hundred and twenty-six patients (74 percent) completed questionnaires at the time of a four-year follow-up. The outcomes that we assessed included disability compensation and work status as well as relief from symptoms, functional status, and quality of life. Results: Patients who were receiving Workers' Compensation at baseline were more likely to be young, male, and employed as laborers. They reported worse functional status; however, the clinical findings for these patients were similar to those for patients who were not receiving Workers' Compensation. Patients who had been receiving Workers' Compensation at baseline were more likely to be receiving disability benefits at the time of the four-year follow-up compared with those who had not (27 percent of 133 compared with 7 percent of 189; p < 0.001); however, they were only slightly less likely to be working at the time of the four-year follow-up (80 percent of 133 compared with 87 percent of 190; p = 0.09). Operative management did not influence these comparisons, but it decreased symptoms and improved functional status. Patients who had been receiving Workers' Compensation at baseline also had significantly less relief from symptoms and improvement in quality of life than patients who had not been receiving Workers' Compensation (all p < 0.001). In multivariate models, Workers' Compensation status at baseline was an independent predictor of whether the patient would be receiving disability benefits after four years (odds ratio, 3.5; 95 percent confidence interval, 1.7 to 7.6) but was not an independent predictor of whether the patient would be working on a job for pay at the time of the four-year follow-up (odds ratio, 0.6; 95 percent confidence interval, 0.3 to 1.2). Conclusions: Even after adjustment for the initial treatment of the sciatica and for other clinical factors, patients who had been receiving Workers' Compensation at baseline were more likely to be receiving disability benefits and were less likely to report relief from symptoms and improvement in quality of life at the time of the four-year follow-up than patients who had not been receiving Workers' Compensation at baseline. Nonetheless, most patients returned to work regardless of their initial disability status, and those who had been receiving Workers' Compensation at baseline were only slightly less likely to be working after four years. Whether or not they had been receiving Workers' Compensation at baseline, patients who had been managed with an operation reported greater relief from symptoms and improvement in functional status at the time of the four-year follow-up compared with patients who had been managed nonoperatively, even though the outcomes with regard to disability and work status in these two groups were comparable.
Low-back problems are a common cause of absence from work and are one of the most frequent reasons for disability compensation claims by working individuals8,23. The financial burden in terms of direct medical costs and lost productivity is immense; it was conservatively estimated at thirty-eight billion dollars in 199412. In working-age populations, sciatica due to a herniated lumbar disc is a common cause of low-back problems resulting in disability. To our knowledge, the effect of Workers' Compensation status on long-term outcomes, especially subsequent disability and employment status, has not been studied in detail for patients with sciatica. Limitations of previous clinical studies of this topic include retrospective assessment of outcome, which is often reported by the treating physician rather than the patient, and a focus on global outcome measures. These global measures group together various combinations of factors, such as changes in symptoms, function, and work status and whether a second procedure was performed1,11,19. Furthermore, longitudinal changes in work and compensation status, with the possibility of entering and leaving the workforce, have rarely been characterized6. Studies of the effect of workplace disability have commonly lacked details on clinical features and outcomes and have often been uncontrolled28. Nonetheless, patients receiving disability compensation are widely reported to have worse outcomes from back pain14,16,29. The purpose of this study was to assess the influence of initial Workers' Compensation status on work-related outcomes from sciatica. We previously reported high rates of disability compensation after one year of follow-up among patients who had been receiving Workers' Compensation at the time of entry into the study3. In the present report, we describe the outcomes after four years of prospective follow-up of patients with sciatica who were recruited from orthopaedic, neurosurgical, and occupational medicine practices throughout Maine.
Details about the design, methods, and one-year outcomes of the study were previously published3,22. In brief, the Maine Lumbar Spine Study is a prospective observational study of patients who have sciatica. The form of management was not prescribed by the study but, rather, was determined in a routine manner by the patient and the physician. Ninety-six percent (255) of 266 patients who chose operative management had open discectomies, with findings of herniation or a free disc fragment in 91 percent (238 of 261). Bed rest, back exercises, physical therapy, spinal manipulation, and narcotic analgesics were most frequently used for patients who elected nonoperative management3.
Study Population
Determination of Workers' Compensation Status at Baseline
Group Not Receiving Workers' Compensation
Study Protocol
Baseline and Outcome Assessment Functional status measures included the back-specific modified disability scale described by Roland and Morris27,30 and the generic Medical Outcomes Study Short Form thirty-six-item questionnaire (SF-36)36. The scores on the modified scale described by Roland and Morris range from 0 to 23 points, reflecting a simple sum of items that are to be marked if present27,30. Items include activities that are limited because of pain (for example, "I am not doing any of the jobs that I usually do around the house"). Three of the eight domains of health included in the SF-3636—physical function, general mental health, and perceptions of general health—were used in our study. Each domain is scored from 0 points (poor health) to 100 points (optimum health). While higher scores according to the SF-36 reflect better function, higher scores on the scale of Roland and Morris reflect worse function. Disability compensation and work status were assessed at each follow-up interval, with the principal outcome being the responses at four years. Disability compensation was ascertained from the patient's response to the question, "Are you currently applying for or receiving any compensation for back problems or sciatica?" Work status was determined from the response to the question, "Since your last interview, have you been employed on a job for pay?" Depending on the responses to these initial questions, detailed questions were asked about the kind of disability compensation that was being received or the reason why the patient was not working. When a patient was working, information was collected on whether it was his or her usual job and whether the work was full-time. Other outcome measures emphasized health-related quality of life as reported by the patient, including symptoms, functional status, and satisfaction3,27. Low-back pain and pain in the lower limb were considered to be relieved if the patient reported that, within the previous week, the symptom occurred very rarely or not at all and was not bothersome (0 or 1 point on a scale of 0 to 6 points).
Analysis In addition to assessing disability and work outcomes at four years, we examined longitudinal changes in disability compensation and work status among 404 patients (92 percent) who had completed at least one follow-up survey over the four-year period. The Kaplan-Meier product-limit method was used to estimate the survival distributions for the time until the patient first reported that he or she was not receiving disability compensation and the time until the patient first returned to work20. Because of the study design, these times were technically interval-censored. For example, if at the six-month follow-up interval a patient first reported that he or she had returned to work, then the actual event had occurred between three months and six months from baseline. To accommodate the interval-censored structure of the data, accelerated failure time models, which are regression models for time-to-event data, were used to adjust for the effect of potential confounders20. All statistical analyses were performed with use of a commercial software package (Statistical Analysis System; SAS Institute, Cary, North Carolina) on a UNIX workstation (Sun Microsystems, Mountain View, California).
Patient Characteristics and Clinical Features at Baseline One hundred and ninety-nine patients who were receiving Workers' Compensation and 241 patients who were not receiving it at baseline were evaluated (Table I). Patients who were receiving Workers' Compensation were generally more likely to be young, male, less educated, and smokers. They were less likely to be managed operatively than were those who were not receiving Workers' Compensation (42 compared with 62 percent; p < 0.001) and were more likely to have retained an attorney because of their current back problem. As expected, they were less likely to have worked in the four weeks before the baseline evaluation. Of the patients who reported recent employment, those who were receiving Workers' Compensation were more likely to be laborers who performed physically demanding work. Patients who were not receiving Workers' Compensation were more likely to be in professional or managerial positions. Stress caused by the job and satisfaction with the job were similar for patients who were receiving Workers' Compensation and those who were not.
The patients who were receiving Workers' Compensation and those who were not were similar with regard to a history of back problems and other comorbid illnesses (Table II). The physical examinations of patients in both groups revealed similar findings. Of the patients for whom advanced imaging studies were available for review, those who were receiving Workers' Compensation were less likely to have moderate or severe findings. However, the percentages of patients meeting the Quebec classification criteria consistent with definitive evidence of nerve-root irritation (category 4 or 6)4,32 were similar. While objective measures of the severity in the two groups were largely similar, there were significant differences in patient-reported symptoms and functional status. Patients who were receiving Workers' Compensation reported symptoms of a longer duration (p = 0.02) and more severe low-back pain (p < 0.001). The frequency of pain in the lower limb and the extent to which it bothered the patient were comparable between the two groups, but patients who were receiving Workers' Compensation were less likely to have unilateral pain in the lower limb than those who were not receiving Workers' Compensation (p = 0.004). Finally, back-specific and generic measures of functional status were all worse for patients who were receiving Workers' Compensation (p  0.002).
Disability Compensation and Work Status at the Time of the Four-Year Follow-up Disability Compensation Four-year outcomes were known for 326 patients (74 percent): 135 (68 percent) of the 199 who initially had been receiving Workers' Compensation and 191 (79 percent) of the 241 who had not (p = 0.009). Twenty-seven percent (thirty-six) of the 133 patients who had been receiving Workers' Compensation at baseline (and who answered the pertinent question on the survey) were receiving some form of disability compensation. Seventeen percent (twenty-two) were receiving Workers' Compensation, 9 percent (twelve) were receiving Supplemental Security Insurance (SSI) or Social Security Disability Insurance (SSDI), and 2 percent (two) did not report the type of compensation (Table III). In comparison, only 7 percent (thirteen) of the 189 patients who had not been receiving Workers' Compensation at baseline (and who answered the question on the survey) were receiving disability compensation at the time of the four-year follow-up (p < 0.001). This comparison of the proportions receiving disability compensation at the time of follow-up was not affected by the initial type of management of the patient. In the operatively managed group, 29 percent (sixteen) of the fifty-six patients who had been receiving Workers' Compensation at baseline and 4 percent (five) of the 118 who had not were receiving disability compensation at the time of follow-up (p < 0.001). In the nonoperatively managed group, the corresponding values were 26 percent (twenty) of seventy-seven and 11 percent (eight) of seventy-one (p = 0.03).
At four years, the unadjusted relative odds of a patient receiving disability benefits if that patient had been receiving Workers' Compensation initially was 5.0 (95 percent confidence interval, 2.6 to 10.3) (derived from data in Table III). In multivariate models adjusting for possible confounders, this relative odds of receiving disability benefits at four years decreased to 3.5 (95 percent confidence interval, 1.7 to 7.6) (Table IV). In these models, other determinants of outcome included symptoms for more than six months, not having graduated from college, and any of a set of comorbid conditions. Each of these variables increased the odds of a patient receiving disability compensation two to sixfold. Whether the patient had retained an attorney at baseline was also examined in separate multivariate models because this variable is highly correlated with the application for Workers' Compensation (Pearson correlation coefficient, 0.45; p < 0.001) (derived from data in Table I). In models including both variables, retaining an attorney was a predictor of receiving disability benefits at four years (odds ratio, 3.9; 95 percent confidence interval, 1.8 to 8.3) independent of the effect of Workers' Compensation at baseline (odds ratios, 2.9; 95 percent confidence interval, 1.4 to 6.4).
Work Status Most of the patients were employed at the time of the four-year follow-up, regardless of the Workers' Compensation status at baseline. However, a slightly, but insignificantly, smaller percentage of patients were working in the group that initially had been receiving Workers' Compensation than in the group that initially had not been receiving Workers' Compensation (80 percent [106 of 133] compared with 87 percent [166 of 190]; p = 0.09) (Table III). Of the patients who reported that they were working at the time of follow-up, those who had been receiving Workers' Compensation at baseline were less likely to have returned to their usual job than those who had not been receiving Workers' Compensation at baseline (67 percent [sixty of eighty-nine] compared with 98 percent [139 of 142]; p < 0.001), but they were as likely to be working full-time (70 percent [sixty-two of eighty-nine] compared with 75 percent [105 of 140]; p = 0.45). As with disability compensation outcomes, the comparison of the proportion of patients who were working at four years according to Workers' Compensation status at baseline was not affected by the type of initial management that the patient had received. In the operatively managed group, 82 percent (forty-five) of the fifty-five patients who had received Workers' Compensation and 88 percent (105) of the 120 who had not were employed at the time of follow-up (p = 0.36). In the nonoperatively managed group, the corresponding values were 78 percent (sixty-one) of seventy-eight and 87 percent (sixty-one) of seventy (p = 0.20). Multivariate analyses that examined initial Workers' Compensation status and other baseline variables revealed that the likelihood of a patient working at the time of the four-year follow-up was independently related to younger age, better perceptions of general health, and less severe low-back pain. In the final model with these independent covariates, receiving Workers' Compensation at baseline was not significantly associated w ith working at four years (odds ratio, 0.6; 95 percent confidence interval, 0.3 to 1.2; p = 0.13) (Table IV).
Longitudinal Changes in Disability Compensation and Work Status Rates of disability compensation over time were not associated with the type of treatment (operative or nonoperative) for patients who initially had been receiving Workers' Compensation (p = 0.70) (Fig. 1-A). Even after adjusting for baseline predictors, including the level of education, the duration of the current episode, and comorbid conditions, the type of treatment was unrelated to the rate of disability compensation over time (p = 0.87). Of the 228 patients who had not been receiving Workers' Compensation at baseline, thirty-six (16 percent) reported that they had received disability compensation at some time during the study period. There were no differences with regard to this variable according to the initial type of treatment (p = 0.57).
Work Status Kaplan-Meier analysis20 demonstrated that, of 174 patients who initially had been receiving Workers' Compensation, 69 percent reported that they were working by one year; 74 percent, by two years; and 78 percent, by three years. Over the four-year follow-up period, 143 (82 percent) of the patients who initially had been receiving Workers' Compensation reported working at a job for pay at least once. Of these patients, eighty-five (59 percent) reported no subsequent periods during which they were not working. Of 351 patients who reported their work status on at least two occasions after the three-month follow-up interval, eighty-eight (59 percent) who initially had been receiving Workers' Compensation and 164 (81 percent) who had not been receiving Workers' Compensation at baseline reported stable long-term employment (p < 0.001). Work status over time was not influenced by the type of treatment for the patients who initially had been receiving Workers' Compensation (p = 0.74) (Fig. 1-B). There was no significant difference in work status over time between patients who had been managed operatively and patients who had been managed nonoperatively, even after adjustment for baseline predictors that included age, severity of low-back pain, and general health status based on the SF-36 (p = 0.91). Of the patients who had not been receiving Workers' Compensation at baseline, 185 (81 percent) were working. Of these patients, forty-one (22 percent) reported that they had been unemployed at least once during the previous four years, and this variable did not differ according to the initial form of management (p = 0.28).
Other Outcomes at the Time of the Four-Year Follow-up Patients who had been receiving Workers' Compensation at baseline had significantly less relief from symptoms and significantly less improvement in quality of life than those who had not been receiving Workers' Compensation at baseline (Table V). After adjustment for independent predictors of outcome in multivariate models, it was demonstrated that patients who had been receiving Workers' Compensation at baseline were less likely to report relief from low-back pain or pain in the lower limb and were less satisfied with their current state (odds ratio, 0.4 to 0.5; all p 0.05). Even the eighty-seven patients who initially had been receiving Workers' Compensation but had then stopped receiving compensation and had returned to work by the time of the four-year follow-up had worse outcomes than the 159 patients who had not been receiving disability compensation at baseline or at the time of the four-year follow-up. For example, in an analysis of the patients who were not receiving disability compensation and were working at the time of the four-year follow-up, it was found that pain in the lower limb was relieved in 60 percent (fifty-two) of the eighty-seven patients who initially had been receiving Workers' Compensation compared with 79 percent (125) of the 159 patients who had not been receiving Workers' Compensation at baseline (p = 0.01 with use of the Cochran-Mantel-Haenszel test to control for the type of treatment).
While operative treatment was not associated with disability outcomes, patients who had been managed operatively, regardless of the initial Workers' Compensation status, fared much better, in terms of symptoms, functional status, and satisfaction, than those who had been managed nonoperatively (Table V). For example, pain in the lower limb was at least partially alleviated in 46 percent (twenty-six) of fifty-six operatively managed patients compared with 37 percent (twenty-nine) of seventy-nine nonoperatively managed patients who initially had been receiving Workers' Compensation. The corresponding values for the patients who had not been receiving Workers' Compensation were 78 percent (ninety-four) of 120 and 59 percent (forty-two) of seventy-one. Operative treatment remained a strong independent predictor of symptom, functional status, and satisfaction outcomes in multivariate models, increasing the likelihood of improvement three to fourfold (all p < 0.001).
We assessed the effect of disability compensation status at baseline on long-term outcomes for patients with sciatica. While most patients who had been receiving Workers' Compensation at baseline eventually returned to work and stopped receiving disability compensation, their overall outcomes were significantly worse than those of the patients who had not been receiving Workers' Compensation at baseline. These differences could not be explained by baseline features or the type of treatment. There were important differences in characteristics between the patients who were receiving Workers' Compensation at baseline and those who were not. Patients who were receiving Workers' Compensation were more likely to be young, male, smokers, less educated, and involved in physically demanding jobs. Similar features have been observed among patients with other musculoskeletal disorders who were receiving Workers' Compensation16,21,29. While those who were receiving Workers' Compensation were more likely to perform physical labor, we found no difference in reported stress caused by the job or satisfaction with the job. Objective findings from physical examination were similar whether or not patients were receiving Workers' Compensation. However, of the patients for whom imaging studies were available for independent review, those receiving Workers' Compensation were less likely to have moderate or severe findings. Additionally, patients who were receiving Workers' Compensation had symptoms that were less likely to be unilateral and more likely to be present for more than six months. Finally, while the severity of symptoms related to the sciatica was comparable between the two groups at the start of the study, patients who were receiving Workers' Compensation reported greater functional limitations. More detailed information on clinical and nonclinical factors10 might help to explain this discrepancy between the objective findings and the reported limitations in functional status. A patient's perception of pain and its functional effect may be influenced by his or her Workers' Compensation status15. In the present report, longitudinal assessment of disability compensation and work status revealed that most patients who received Workers' Compensation eventually returned to work and no longer received any form of disability compensation. However, some patients reported that they continued to receive disability payments (approximately 50 percent at one year and 30 percent at three years) and were not working (approximately 30 percent at one year and 20 percent at three years) for long periods. Although some patients who initially returned to work were not able to maintain long-term employment, most (66 percent) remained working and were not receiving disability compensation at the time of the four-year follow-up. The four-year outcomes for the patients who had been receiving Workers' Compensation at the baseline evaluation were worse than those for patients who had not been receiving Workers' Compensation at baseline. These outcomes included relief from symptoms, change in functional status, and satisfaction, which were all inferior for patients who initially had been receiving Workers' Compensation. Patients who had been receiving Workers' Compensation were more likely to be receiving some form of disability benefits after four years (27 percent compared with 7 percent for the patients who had not been receiving Workers' Compensation; p < 0.001), although they were only slightly less likely to be working (80 percent compared with 87 percent; p = 0.09). These results persisted after adjusting for other potential predictors of long-term disability and work status. While operative treatment was associated with significantly better relief from symptoms, functional status, and satisfaction, it had no significant effect on disability or work outcomes at the time of the four-year follow-up. We previously reported that operative treatment provided slight advantages in terms of disability and work outcomes at the time of a six-month follow-up5. However, these differences were small and were no longer significant by the time of a one-year follow-up3, and they remained insignificant through four years. In contrast, the greater relief from symptoms, improvement in functional status, and satisfaction that were associated with operative treatment were still significant at the time of the one-year follow-up and persisted through four years. Despite the common belief that receiving disability benefits negatively influences outcomes, the evidence bearing on this issue has been contradictory9,13,14,16,24,26,29,31. A variety of methodological issues may account for these conflicting results. First, different measures of outcome reported by patients or physicians (both blinded and unblinded) have been used in different studies. Second, not all investigators have controlled for differences in clinical features other than disability status. Third, studies often involve small numbers of patients and include a variety of different back disorders. Many of these problems were overcome in our study with the prospective collection of detailed baseline and follow-up information on a large number of patients who had the same low-back disorder. Detailed baseline assessment included sociodemographic data; findings of physical examination; patient-reported symptoms, functional status, and disability; and work status. A range of outcome variables was assessed, including work and disability status as well as resolution of symptoms, functional status, and satisfaction. There were important differences between patients who initially had been receiving Workers' Compensation and those who had not. However, there was sufficient overlap in baseline features and a large enough sample size to permit statistical adjustment of differences in outcomes according to baseline characteristics. Several important limitations of the study should be noted. While Workers' Compensation status was verified at the initial evaluation, the work status at baseline and the long-term disability and work outcomes were determined by unconfirmed reports from the patients. Second, more patients who initially had been receiving Workers' Compensation were lost to follow-up than those who had not, especially by the time of the four-year survey. The effect of this factor is not clear, although patients who did not complete all of the follow-up surveys may have had worse outcomes than those who did3. Finally, the nature of Workers' Compensation law varies, and this may affect the ability to generalize our findings in Maine to other states and regions. Disability due to low-back pain and sciatica is a major problem in terms of physical limitation and financial hardship for individuals and lost productivity and high costs of care for industry and society as a whole12,18. Patients with disabling back pain who enter the Workers' Compensation system face an adversarial process that can, in the end, reward disability7. Because the diagnosis is not infallible and critically depends on patients' reports of symptoms, perceptions of pain and their functional effect can be skewed by the Workers' Compensation process. The injured worker needs the physician to validate his or her symptoms to get financial support15. The important role of the patient's symptoms and their potential to lead the physician to the wrong diagnosis and to potentially ineffective treatments have led physicians to develop objective findings, such as the signs described by Waddell et al.35, that can identify patients with inappropriate pain responses. Physicians may avoid operating on patients who are thought to view an operation as a way to validate their claim of a back injury. Thus, reluctance to offer certain forms of treatment to patients who are seeking Workers' Compensation is understandable34. Indeed, our patients who initially had been receiving Workers' Compensation were less likely to be managed operatively even though the objective evidence of sciatica was similar to that for patients who had not been receiving Workers' Compensation2. Nevertheless, a physician's reluctance to operate on a patient with sciatica who is receiving Workers' Compensation must be tempered by the fact that the patient may benefit from an operation. Our findings that the type of treatment did not influence long-term disability or work status do not imply that all patients who are receiving disability compensation should be managed nonoperatively. The better symptom and functional status outcomes for the operatively managed patients who initially had been receiving Workers' Compensation may justify operative management as long as patients and surgeons recognize that the goal of the management is to reduce symptoms and improve function but not necessarily to hasten the return to work. Our observations highlight the challenges in caring for patients who have disabling back pain and sciatica. Physicians evaluating the need for an elective operation in patients with sciatica who are receiving Workers' Compensation need better methods to identify those who will benefit. Patients need to understand the likely effects of alternative forms of treatment on the symptoms, functional status, and disability status. Given the time constraints of office visits, providing patients with more detailed information about treatment outcomes may improve decisions for individual patients and result in better outcomes33. Employers, insurers, and policymakers also need to understand that, while certain forms of treatment may not markedly reduce disability benefit claims, reductions in symptoms, improvement in functional status, and enhanced patient satisfaction remain important, valid outcomes. Changes in the Workers' Compensation system, such as creation of a less adversarial atmosphere for compensation claims7, more accommodating workplaces17, and efforts to better prepare individuals to return to physically demanding work25, may encourage patients with resolving symptoms to return to work and to stop collecting disability compensation sooner. Finally, research that assesses both medical and work-based interventions is needed to better define their relative roles in efficient treatment strategies.
*No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Funds were received in total or partial support of the research or clinical study presented in this article. The funding source was the Agency for Health Care Policy and Research (Grants HS-06344, HS-08194, and HS-09804).
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