The Effectiveness of Standard Care, Early Intervention, and Occupational Management in Worker s Compensation Claims SPINE Volume 28, Number 3, pp 299 304 2003, Lippincott Williams & Wilkins, Inc. Mark Lemstra, MSc, and W. P. Olszynski, MD, PhD, FRCP(C) Study Design. A retrospective and prospective cohort. Objectives. To compare the effectiveness of occupational intervention, early intervention, and standard care in the management of Worker s Compensation injury claims. Summary of Background Data. The current management of occupational back pain and work-related upper extremity disorders with either standard care or early intervention appears to be ineffective. Methods. A retrospective cohort compared injury claim incidence, duration, and costs between one company with access to standard care and another similar company with access to early intervention. A prospective cohort looked at the effect of one company changing from standard care to occupational management in comparison with the control group with early intervention. Survival analysis was used to attempt to explain differences in injury claim duration. Results. Standard care resulted in lower injury claim incidence, duration, and costs than early intervention, whereas occupational management resulted in lower injury claim incidence, duration, and costs than standard care. The covariates of physical therapist involvement, chiropractor involvement, injury severity, and relationship between Worker s Compensation and the employer were associated with delayed time to claim closure in the company with access to early intervention with the most important covariate being physical therapist involvement (hazard rate ratio 19.88, 95% confidence interval 7.95 39.77). Only the covariate of injury severity was associated with delayed time to claim closure in the company with access to occupational management (hazard rate ratio 1.67, 95% confidence interval 1.05 27.20). Conclusions. It is recommended that an occupational management approach, in comparison with standard care or early intervention, be considered for management of occupational injuries. [Key words: Worker s Compensation, incidence, disability, cost, rehabilitation, early intervention, standard care] Spine 2003;28:299 304 From the College of Medicine, University of Saskatchewan, Saskatoon, Saskatchewan, Canada. Acknowledgment date: January 3, 2002. First revision date: April 8, 2002. Acceptance date: June 20, 2002. The manuscript submitted does not contain information about medical device(s)/drug(s). No funds were received in support of 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. Address correspondence to W. P. Olszynski, MD, PhD, FRCP(C), College of Medicine, University of Saskatchewan, 103 Hospital Drive, Saskatoon, Saskatchewan S7N 0W8, Canada; E-mail: olszynski@webster.sk.ca The rising disability and costs associated with Worker s Compensation claims are not exclusive to the province of Saskatchewan, Canada. Occupational low back pain and work-related upper extremity musculoskeletal disorders have become a concern for all industrialized countries. As such, considerable time and effort have been expended on the development of effective treatment interventions to reduce the disability and costs associated with occupational injuries despite their nonspecific nature. At this time, early identification of patients destined for chronicity, with the intention of providing more intensive treatment more quickly, currently does not exist. 9 Furthermore, most of the individual risk factors identified to date appear to be unchangeable or at least unresponsive to treatment. This is to say nothing of the social, legal, political, economic, and organizational factors that can influence injury claim incidence, duration, and costs. As such, it is not surprising that systematic reviews and randomized trials have consistently emphasized minimal clinical intervention, reassurance of a good prognosis, encouragement to resume normal activity, and the provision of simple exercises as a management approach. 8 10,13,20,21 Despite these recommendations, excessive specialist referral, investigation, and treatment are the norm throughout North America. 9 Faced with the increased frequency, duration, and costs associated with injury claims, the Worker s Compensation Board of Ontario initiated an immediate access, intensive therapy protocol for injured workers. Although the preliminary results were encouraging, 14 the ensuing population-based prospective cohort determined that the new protocol did not have any advantages over standard care in terms of duration of benefits, functional status, health-related quality of life, or pain measures. The new protocol did, however, add an additional $900 Canadian of health care costs to the average claimant. The authors concluded that earlier and more intensive protocols should not be thought of as necessarily implying more effective protocols, as is often the case in medical care. In the end, the new protocol treated too many, too soon, for too long of a time in a setting too unrelated to the workplace. 19 The experience with early intervention in Saskatchewan has not differed from that in Ontario. Annual administrative publications from the Worker s Compensation Board of Saskatchewan (WCB) indicate that rapid and expanded rehabilitation services have contributed to 38% increases in medical and rehabilitation costs, 17% increases in wage replacement costs, 24% increases in overall costs, 17% increased disability time, and 18% lower return-to-work rates (Table 1). 1 5,7 During that time, there were no substantial increases in overall claims (4%), fee for service reimbursement for rehabilitative 299
300 Spine Volume 28 Number 3 2003 Table 1. WCB Injury Claims History in Saskatchewan by Year 1996* 1997 1998 1999 2000 Total injury claims accepted 31,732 33,545 32,348 31,476 32,927 Total time loss injury claims accepted 13,018 13,430 13,081 13,108 14,433 Total medical and rehabilitation costs (million) $23.4 $26.4 $29.0 $31.4 $37.4 Total wage replacement costs (million) $86.7 $98.4 $103.4 $108.2 $104.6 Total injury costs (million) $143.4 $160.9 $172.8 $185.5 $189.8 Average time loss injury duration (days) 21.4 22.2 23.9 24.9 25.8 Overall return-to-work success rates (%) 72 72 62 59 Unavailable WCB Worker s Compensation Board. * Last year of standard care. First year of Early Intervention Program. services (1%), or wage replacement (9%). 6 Within the one specific industry under review, time-loss injury claim incidence increased by 20% whereas disability time increased by 33%. Time-loss claims that exceeded 4 weeks in duration increased in disability time by 42%, 18 which is the exact opposite to program expectations (Table 2). The purpose of the current study was to determine if an occupationally based program that focused on injury prevention, reassurance of a good prognosis, encouragement to resume normal activity, simple exercises, and early return to work would have a substantial effect on injury claim incidence, duration, and costs in comparison with standard care or the provision of rapid and expanded rehabilitation services (Early Intervention Program [EIP]). Materials and Methods Early Intervention Program. In September 1996, the WCB initiated an EIP with the intention of providing rapid and expanded rehabilitation services to injured workers to facilitate their return to the workplace. Injured workers are required to immediately participate in expanded physical therapy and work-hardening programs. If not at work at 6 weeks, broader secondary or tertiary treatment protocols are initiated that last up to 4 hours a day and include psychosocial intervention. The decision for secondary or tertiary rehabilitation is based on 28 red flags considered important by the WCB. 7 Secondary treatment protocols are, on average, 31.85 treatment days in duration and cost $3769.77 per client, whereas tertiary treatment protocols are, on average, 48.93 treatment days in duration and cost $7383.05 per client. 17 A multidisciplinary assessment ranging in cost from $900 to $1800 is required before secondary or tertiary treatment. The compensation board s approach to injury claim management is standardized even if the injured workers are not. 7 The EIP initially began in the province s two largest cities with the intention of expanding to all cities in the province. By January 1, 2000, there was only one city within the province that did not have direct access to the EIP. Study Population and Design. The largest corporation in the only city without direct access to the EIP program, as of January 1, 2000, was chosen for study. This corporation was in the meat industry and had access only to standard medical and physical therapy care, which included long waiting lists for physical therapy (company A). A control company was chosen within the same industry that was thought to be the most similar in the province with the exception that it had direct access to the EIP program (company B). The companies were thought to be comparable as they were listed within the same WCB industry code and WCB industry subcode (of six potential subcodes). Both companies were of a similar size, worked similar hours, performed similar measured work demands (constant standing, occasional lifting, and constant repetitive use of upper extremity), and had similar psychosocial factors (monotonous work, high self-perceived workloads, time pressure, and general worker dissatisfaction). As well, both companies were unionized and had a similar management structure. The only other comparable company in the province had access to early intervention and had a similar claims experience to company B (data not shown). On January 1, 2000, company A initiated an occupational management protocol that included primary prevention strategies designed to change the work, not the worker. The strategies included worker rotation schedules, reduced lifting loads, and ergonomic redesign of tasks. The protocols were simple in scope, required no cost to the company, and did not negatively influence company productivity. Secondary prevention strategies consisted of independent on-site management with a physical therapist, which included reassurance of a good prognosis, encouragement to resume normal activities, simple exercises, and recommendations to resume work as soon as safely possible on either full duties or time-limited modified or light duties. The neutral return-to-work arrangements were based on phys- Table 2. WCB Injury Claims in Meat Industry in Saskatchewan by Year 1996 1997 1998 1999 2000 Time loss injury claims per 100 workers 21.3 23.7 24.8 24.5 27.2 Average time loss duration (days) 19.8 19.1 27.6 29.5 29.6 Average time loss duration 4 weeks (days) 5.7 5.6 5.8 5.5 5.8 Average time loss duration 4 weeks (days) 40.2 40.9 54.5 65.9 69.2 WCB Worker s Compensation Board.
Worker s Compensation Claims Lemstra et al 301 ical and functional information from the physical therapist and medical information from the family physician. Company management, union leadership, and the workers themselves fully supported the independent occupational management approach and were, at all times, encouraged to participate in its development. A retrospective cohort of time-loss injury claims was formed to compare standard care in company A to early intervention in company B in the year 1999. The retrospective cohort entry date was the day of the claim, and the exit date was the date of claim closure or March 31, 2000. A prospective cohort of timeloss injury claims was then formed to compare occupational intervention in company A in 2000 to standard care in company A in the year 1999 and then occupational intervention in company A in 2000 to early intervention in company B in 2000. The prospective cohort entry date was the day of the claim, and the exit date was the date on which the claim was closed or March 31, 2001. Outcome Measures. The outcome measures were the number of work-related total time-loss injury claims, time-loss back sprain/strain injury claims, time-loss upper extremity musculoskeletal claims, the disability duration of all of the above, and the medical, wage replacement, and total costs of the above. Twelve-month cumulative incidence rates were calculated with the total number of hours worked at the particular place of employment as the denominator. Rate ratios were used to determine the effect of occupational intervention in company A from 1999 to 2000, and relative values of the rate ratios (RRs) were used to determine the effect of the intervention in comparison with the control group (company B). 15 The primary interest of the study was to determine the effect of occupational intervention on work-related back and upper extremity musculoskeletal injuries in comparison with standard care and early intervention. Upper extremity musculoskeletal injuries were defined as any strain/sprain from the wrist joint to the shoulder joint. Back injuries were defined as any strain/sprain of the lower (L5) to mid back (T6). The secondary interest of the study was to investigate the association between overall claim closure and recovery from all time-loss injury claims between company A and company B in the year 2000. Cox proportional-hazard models were constructed to determine the association between time to claim closure and the covariates of age (above or below the age of 40 years), gender, duration of employment (less than or more than 3 months with company), wage (above or below mean of $67 a day), previous WCB time-loss claim, injury location and severity, hospital visit, health care provider (medical physician, chiropractor, or physical therapist), and relationship between the employer and the injured worker s physician, the injured worker s WCB client service representative, and the injured worker himself all measured by interview with the employer. To accommodate for sample size, a hierarchical well-formulated modeling approach was used instead of a computer-generated stepwise algorithm. 16 The unadjusted effect of each covariate was determined and then entered one step at a time based on changes in the 2 log likelihood and the Wald test. 11 The final model includes factors with beta values for which the P values were 0.05. The ph assumption was assessed by the log-log Cox adjusted survival estimate stratified by company against the log of time. 11 The results are presented as hazard RRs with 95% confidence intervals (CIs). All analyses were performed with an SPSS 10.0 software package. 22 Results Standard Care (Company A, 1999) and Early Intervention (Company B, 1999) Company A and company B were of similar size (company A, 185 employees; company B, 232 employees) and worked similar total hours (company A: 305,320 hours; company B: 450,945 hours) in 1999. The only known difference was direct accessibility to rapid and expanded rehabilitation services available to company B. As such, company A had an incidence rate of 2.3 upper extremity and 2.6 back time-loss claims per 100,000 hours worked. In comparison, company B had an incidence rate of 7.3 upper extremity and 4.0 back time-loss claims per 100,000 hours worked. Company A had 138.5 upper extremity and 60.9 back time-loss days for every 100,000 hours worked. In contrast, company B had 731.6 upper extremity and 141.0 back time-loss days for every 100,000 hours worked. As a result, company A had a compensation cost of $15,777 for upper extremity time-loss claims and $8713 for back time-loss claims per 100,000 hours worked. In comparison, company B had a compensation cost of $80,816 for upper extremity timeloss claims and $12,296 for back time-loss claims per 100,000 hours worked (Table 3). Standard Care (Company A, 1999) and Occupational Intervention (Company A, 2000) In the year 2000, company A expanded its operation in both employees (285) and hours worked (464,520) to make it even more similar to company B (232 employees and 459,879 hours worked). On January 1, 2000, company A also started an occupational-based injury claims prevention and management protocol. In response, the incidence of upper extremity time-loss claims reduced to 0.6 and back time-loss claims reduced to 0.6 per 100,000 hours worked. By calculating the RR, we find that the rate of injury occurrence has been reduced by 72% for upper extremity time-loss claims (RR 0.28; 95% CI 0.07 1.09) and back time-loss claims have been reduced by 75% (RR 0.25; 95% CI 0.07 0.93). The company did not have a change in medical-aid-only claims (no time loss) in which a payment was made (data not shown). As well, company A now had 12.3 upper extremity time-loss days and 1.1 back time-loss days per 100,000 hours worked. By calculating the RR, we find that the rate of days lost has been reduced by 91% for upper extremity time-loss days (RR 0.09; 95% CI 0.07 0.12) and 98% for back time-loss days (RR 0.02; 95% CI 0.01 0.04). Upper extremity time-loss costs reduced from $15,777 to $597, and back time-loss costs reduced from $8713 to $287 per 100,000 hours worked (Table 3). Occupational Intervention (Company A, 2000) and Early Intervention (Company B, 2000) In comparison with company A, company B did not share the same claims experience from 1999 to 2000. By reviewing the RRs, we find that the rate of injury occur-
302 Spine Volume 28 Number 3 2003 Table 3. Incidence, Disability, and Cost Differences Between Two Companies in the Meat Industry Total WRUEM Back Company A 2000 (occupational intervention) Time loss injury claims/100,000 hours worked 3.2 0.6 0.6 Total days lost/100,000 hours worked 66.1 12.3 1.1 Wage replacement/100,000 hours worked $3544 $407 $53 Medical/rehabilitation compensation/100,000 hours worked $2484 $190 $234 Total compensation/100,000 hours worked $6028 $597 $287 1999 (standard care) Time loss injury claims/100,000 hours worked 7.9 2.3 2.6 Total days lost/100,000 hours worked 220.4 138.5 60.9 Wage replacement/100,000 hours worked $12,287 $7480 $3928 Medical/rehabilitation compensation/100,000 hours worked $13,591 $8297 $4785 Total compensation/100,000 hours worked $25,878 $15,777 $8713 Company B 2000 (early intervention) Time loss injury claims/100,000 hours worked 21.8 8.9 5.4 Total days lost/100,000 hours worked 1129.2 662.6 280.1 Wage replacement/100,000 hours worked $71,051 $43,189 $16,646 Medical/rehabilitation compensation/100,000 hours worked $49,408 $29,947 $13,091 Total compensation/100,000 hours worked $120,459 $73,136 $29,737 1999 (early intervention) Time loss injury claims/100,000 hours worked 22.4 7.3 4.0 Total days lost/100,000 hours worked 1224.8 731.6 141.0 Wage replacement/100,000 hours worked $76,309 $46,780 $7981 Medical/rehabilitation compensation/100,000 hours worked $57,593 $34,036 $4315 Total compensation/100,000 hours worked $133,902 $80,816 $12,296 WRUEM work-related upper extremity musculoskeletal disorder. rence for company B in the year 2000 (in comparison with 1999) for upper extremity time-loss claims increased by 22% (RR 1.22; 95% CI 0.74 2.00), and back time-loss claims increased by 36% (RR 1.36; 95% CI 0.74 2.50). By reviewing the RRs for days lost in company B in 2000, we find that upper extremity time-loss days reduced by 9% (RR 0.91; 95% CI 0.86 0.95), and back time-loss days increased by 99% (RR 1.99; CI 1.81 2.18). Corresponding upper extremity time-loss costs reduced from $80,816 to $73,136, and back time-loss costs increased from $12,296 to $29,737 per 100,000 hours worked (Table 2). To determine the significance of the change from 1999 to 2000 in the intervention group (company A) in comparison with the control group (company B), the relative (or proportional) values of the RRs were compared. The z statistic for total time-loss injury claim incidence between the two companies is 2.58 (P 0.01), and the z statistic for upper extremity and back time-loss claims combined is 3.02 (P 0.004), suggesting that the occupational intervention had a statistically significant effect in lowering both the incidence rate of total timeloss injury claims and upper extremity/back time-loss injury claims in comparison with the control group. Closure of Claims (Company A, 2000, and Company B, 2000) Changes in incidence, disability duration, and costs were observed after controlling for injury location, severity, and hours worked between the two companies. Because of the uncertainty about the reasons for the differences observed, a Cox proportional-hazard model for total time-loss injury claims was constructed. One case was censored in company A (serious injury), and 16 cases were censored in company B (3 back, 11 upper extremity, 2 serious injury) because of nonfinalized claims. For the company with access to early intervention (company B), variables with a significant influence on delayed time to claim closure included physical therapist involvement (hazard RR 19.88; 95% CI 7.95 39.77), neutral or adversarial relationship between the employer and the WCB representative (hazard RR for neutral relationship 4.38; 95% CI 1.55 12.41 and hazard RR for adversarial relationship 3.74; 95% CI 1.99 7.05), injury severity (serious injury hazard RR 2.99; 95% CI 1.20 7.49 and upper extremity/back injury hazard RR 3.42; 95% CI 1.27 9.20), and chiropractor involvement (hazard RR 2.88; 95% CI 1.45 5.73). In comparison, the only variable with an unadjusted or adjusted significant influence on delayed time to claim closure in the company with access to occupational management (company A) was injury severity (serious injury hazard RR 1.67; 95% CI 1.05 27.20) (Table 4; Figure 1). Discussion After the introduction of the EIP in the province of Saskatchewan, corresponding increases were observed in injury claim incidence, duration, and costs on a population-based level, an industry level, and at the individual company level. The explanations are not clear, but it is presumed that aggressive referral to expanded physical therapy might have resulted in the treatment of many workers that would have recovered more quickly with-
Worker s Compensation Claims Lemstra et al 303 Table 4. Factors Associated With Time to Injury Claim Closure Factor Company A (occupational intervention) * Company B (early intervention) * Physical therapist involvement No 1.00 Yes 19.88 (7.95 39.77) Chiropractor involvement No 1.00 Yes 2.88 (1.45 5.73) Relationship between employer and WCB representative Positive 1.00 Neutral 4.38 (1.55 12.41) Negative 3.74 (1.99 7.05) Injury severity Minor injury (cut, bruise, other) 1.00 1.00 Back or upper extremity strain or sprain 1.50 (0.829 24.29) 3.42 (1.27 9.20) Serious injury (fracture, break, dislocation, head injury) 1.67 (1.05 27.20) 2.99 (1.20 7.49) CI confidence interval; WCB Worker s Compensation Board. * Values are hazard rate ratio (95% CI). Hazard rate ratios have been adjusted for all other significant factors in the model. Reference category. out the enhanced intervention. As such, many workers had delayed return-to-work plans to complete their 6- to 10-week work hardening and conditioning programs before reintroduction into the work environment. As well, the biologic plausibility and credibility associated with enhanced treatment most likely delayed the urgency on behalf of WCB to seek immediate reintroduction into the workplace either on light duties or modified duties. 19 In the current study, the company with access to early intervention had substantial differences in injury claims experience in comparison with the company with access to occupational intervention despite stratifying for injury location and severity. The incidence rate of work-related upper extremity injuries between the two companies in the year 2000 was 8.9 to 0.6, the difference in claims duration was 662.6 to 12.3 days, and the difference in Figure 1. Survival curve (adjusted) estimates of the time to claim closure between company A (occupational intervention) and company B (early intervention). total costs was $73,136 to $597 per 100,000 hours worked. The incidence rate of work-related back injuries between the two companies in the year 2000 was 5.4 to 0.6, the difference in claims duration was 280.1 to 1.1 days, and the difference in total costs was $29,737 to $287 per 100,000 hours worked. The results of the Cox proportional-hazard model suggest that rapid and enhanced physical therapist involvement negatively influenced the rate of return to work by a factor of 20. This association maintained its influence throughout all steps of the survival model while controlling for all other covariates, including injury severity. In other words, rapid and enhanced physical therapist involvement is more likely a predictor of delayed claim closure than a result of it. It would be naive, however, to suggest that all of the observed differences between the two companies are the result of the EIP despite stratifying for injury location and severity and controlling for numerous other measured variables in the survival analysis. The existence of these unmeasured differences confirms, rather than refutes, the necessity to view work-related injury claims within a larger population-based social, legal, political, economic, and organizational domain. Recently, primary and secondary prevention strategies have begun to turn away from individual risk factors and focus attention on changing the work and not the worker. A population-based randomized trial on back pain management in Sherbrooke, Quebec, Canada, demonstrated that standard care resulted in median duration time off work for 121 days, a multidisciplinary rehabilitation program resulted in a median duration time off work for 131 days, and an occupational management approach, including ergonomic redesign and time limited light duties, resulted in a median time off work for only 67 days. 12 Although a randomized clinical trial is normally the research design of choice, it was not possible in our cur-
304 Spine Volume 28 Number 3 2003 rent study to randomize the two companies. Instead, the authors are currently reviewing the effects of reversing the occupational intervention in company A and implementing early intervention. It is thought that any remaining threats to internal validity in the current study are low because the information gathered at the individual company level is consistent with the information gathered at the industry level and the population-based level. As well, our findings are consistent with previous research reviewing the effects of early intervention. The failure of rapid and expanded rehabilitative care in the province of Saskatchewan as a means of secondary prevention should not meet with total discouragement. Population-based research could identify the important prognostic factors required to determine who would benefit from rapid and enhanced care. In the interim, however, primary injury prevention protocols and, if required, secondary prevention protocols emphasizing minimal clinical intervention, reassurance of a good prognosis, encouragement to resume normal activities, simple exercises, and strategies to reintegrate the worker back into the workforce as soon as is safely possible is recommended. Key Points This article compares the effectiveness of occupational intervention, early intervention, and standard care in the management of Worker s Compensation injury claims. Occupational management resulted in lower injury claim incidence, duration, and costs than standard care. Standard care resulted in lower injury claim incidence, duration, and costs than early intervention. The results of the Cox proportional-hazard model suggest that rapid and enhanced physical therapist involvement negatively influenced the rate of return to work by a factor of 20. References 1. Annual report 1996. Regina, Saskatchewan: Saskatchewan Worker s Compensation Board, 1996:1 48. 2. Annual report 1997. Regina, Saskatchewan: Saskatchewan Worker s Compensation Board, 1997:1 51. 3. Annual report 1998. Regina, Saskatchewan: Saskatchewan Worker s Compensation Board, 1998:1 56. 4. Annual report 1999. Regina, Saskatchewan: Saskatchewan Worker s Compensation Board, 1999:1 63. 5. Annual report 2000. Regina, Saskatchewan: Saskatchewan Worker s Compensation Board, 2000:1 60. 6. Annual report 2000. Regina, Saskatchewan: Saskatchewan Bureau of Statistics, 2000. 7. Dorsey, JE. Review 2000 recurring and current administrative issues. Saskatchewan Worker s Compensation Board, 2000:1 133. 8. Faas A, Chavennes AW, van Eijk JT, et al. A randomized, placebo-controlled trial of exercise therapy in patients with acute low back pain. Spine 1993; 18:1388 95. 9. Frank JW, Brooker AS, DeMaio SE, et al. Disability resulting from occupational low back pain: II. What do we know about secondary prevention? A review of the scientific evidence on prevention after disability begins. Spine 1996;21:2918 29. 10. Indahl A, Velund L, Reikeraas O. Good prognosis for low back pain when left untampered: a randomized clinical trial. Spine 1995;20:473 7. 11. Kleinbaum DG. Survival Analysis: A Self-Learning Approach. New York: Springer-Verlag, 1997. 12. Loisel P, Abenhaim L, Durand P, et al. A population-based randomized clinical trial on back pain management. Spine 1997;22:2911 8. 13. Malmivaara A, Hakkinen U, Aro T, et al. The treatment of acute low back pain: bed rest, exercises or ordinary activity? N Engl J Med 1995;332:351 5. 14. Mitchell RI, Carmen GM. Results of a multicenter trial using an intensive active exercise program for the treatment of acute soft tissue and back injuries. Spine 1990;15:514 21. 15. Robson LS, Shannon HS, Goldenhar LM, et al. Guide to evaluating the effectiveness of strategies for preventing work injuries. Public Health Service, Center for Disease Control and Prevention, National Institute for Occupational Safety and Health 2001;1:1 122. 16. Rothman KJ, Greenland S. Modern Epidemiology. 2nd ed. Philadelphia, PA: Lippincott Williams & Wilkins, 1998. 17. Saskatchewan Worker s Compensation Board. Public communication. Saskatchewan Worker s Compensation Board, 1998. 18. Saskatchewan Worker s Compensation Board. 2002 premium rates and funding strategy. Saskatchewan Worker s Compensation Board, 2001. 19. Sinclair SJ, Hogg-Johnson S, Mondloch MV, et al. The effectiveness of an early active intervention program for workers with soft tissue injuries: the early claimant cohort study. Spine 1997;22:2919 31. 20. Spitzer WO, Leblanc FE, Dupuis M, et al. Scientific approach to the assessment and management of activity-related spinal disorders: a monograph for clinicians. Report of the Quebec Task Force on Spinal Disorders. Spine 1987;12(suppl 7):S4 55. 21. van Tulder MW, Malmivaara A, Esmail R, et al. Exercise therapy for low back pain (Cochrane Review). In: The Cochrane Library, Issue 4, 2001. 22. Version 10.0 SPSS. Chicago: 2000 (software).