Early Predictors of Lumbar Spine Surgery After Occupational Back Injury

Results From a Prospective Study of Workers in Washington State

Benjamin J. Keeney, PhD; Deborah Fulton-Kehoe, PhD, MPH; Judith A. Turner, PhD; Thomas M. Wickizer, PhD; Kwun Chuen Gary Chan, PhD; Gary M. Franklin, MD, MPH

Disclosures

Spine. 2013;38(11):953-964. 

In This Article

Abstract and Introduction

Abstract

Study Design. Prospective population-based cohort study.

Objective. To identify early predictors of lumbar spine surgery within 3 years after occupational back injury.

Summary of Background Data. Back injuries are the most prevalent occupational injury in the United States. Few prospective studies have examined early predictors of spine surgery after work-related back injury.

Methods. Using Disability Risk Identification Study Cohort (D-RISC) data, we examined the early predictors of lumbar spine surgery within 3 years among Washington State workers, with new workers compensation temporary total disability claims for back injuries. Baseline measures included worker-reported measures obtained approximately 3 weeks after claim submission. We used medical bill data to determine whether participants underwent surgery, covered by the claim, within 3 years. Baseline predictors (P < 0.10) of surgery in bivariate analyses were included in a multivariate logistic regression model predicting lumbar spine surgery. The area under the receiver operating characteristic curve of the model was used to determine the model's ability to identify correctly workers who underwent surgery.

Results. In the D-RISC sample of 1885 workers, 174 (9.2%) had a lumbar spine surgery within 3 years. Baseline variables associated with surgery (P < 0.05) in the multivariate model included higher Roland-Morris Disability Questionnaire scores, greater injury severity, and surgeon as first provider seen for the injury. Reduced odds of surgery were observed for those younger than 35 years, females, Hispanics, and those whose first provider was a chiropractor. Approximately 42.7% of workers who first saw a surgeon had surgery, in contrast to only 1.5% of those who saw a chiropractor. The area under the receiver operating characteristic curve of the multivariate model was 0.93 (95% confidence interval, 0.92–0.95), indicating excellent ability to discriminate between workers who would versus would not have surgery.

Conclusion. Baseline variables in multiple domains predicted lumbar spine surgery. There was a very strong association between surgery and first provider seen for the injury even after adjustment for other important variables.

Introduction

Back pain is the most costly and prevalent occupational health condition among the US working population.[1,2] Costs relating to occupational back pain increased more than 65% from 1996 to 2002 after adjustment for medical and general inflation.[3] Spine surgical procedures after occupational back injury represent approximately 21% of these costs[4] and face increasing scrutiny regarding effectiveness and efficacy.[5,6] There is little evidence that spine surgery is associated with improved population outcomes,[5] yet surgery rates have increased dramatically since the 1990s.[7–10] Reducing unnecessary spine surgery is important for improving patient safety and outcomes and reducing surgery complications and health care costs.[11,12] Although previous studies have investigated predictors of outcomes after lumbar spine surgery,[13–17] little research has focused on identifying early (after injury) factors associated with receipt of surgery.[18,19] Knowledge of early predictors of lumbar spine surgery after occupational back injury may help identify workers likely to undergo surgery, which, in turn, has potential to improve patient outcomes by targeting evidence-based care to such workers. Furthermore, such information is essential for comparative effectiveness studies so that factors associated with receipt of surgery can be assessed and included in adjustment techniques to increase comparability of treatment groups.

We used data from the Washington State Workers' Compensation Disability Risk Identification Study Cohort (D-RISC), a sample of workers with temporary total disability for a back injury, to assess rates of lumbar spine surgery in the first 3 years of the claim. We aimed to identify early predictors of such surgery, develop a multivariate predictive model of surgery, and evaluate the model's ability to predict surgery.

We used previous occupational injury, back injury, chronic back pain–related disability, and lumbar spine surgery literature to identify potential early predictors available in the D-RISC baseline data, which include measures in 7 domains (sociodemographic, employment-related, pain and function, clinical status, health care, health behavior, and psychological).[20–23] We hypothesized that the following baseline variables would be associated with subsequent lumbar spine surgery: older age,[9,10] higher pain ratings,[17,20,24,25] prescription of opioid medication within 6 weeks from the first medical visit for the injury,[18,26] worker perception that the job is "hectic,"[20] no employer offer of job accommodation after the injury,[20] worse psychological factors,[16,17,22,23] worse injury severity,[5,6,18,20] rural residence,[9,27] and a history of back injuries.[28] We also hypothesized that Hispanic,[10,17,29,30] non-white,[9,10,17,30] and female workers,[9,10,30] and workers with shorter current job duration[31] would have reduced odds of surgery, and that rates of surgery would vary by first provider seen for the injury.[32]

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