Abstract

Objectives: To investigate the longitudinal patterns of recovery among workers with compensated occupational back injuries.

Methods: A longitudinal cohort study, with one-year follow-up via structured telephone interviews, among respondents off work because of “new” back injuries. Self-reported pain intensity was recorded at baseline and at four follow-up time points over the course of one year. Workers who answered the questionnaire on at least three occasions (n = 678) were classified into clusters according to their patterns of pain intensity over time using a two-step cluster analysis.

Results: Four pain recovery patterns were identified: workers with high levels of pain intensity showing no improvement over time (43%); those experiencing recovery in the first four months with no further improvement or possibly even some deterioration, in the second half year (33%); those experiencing a slow consistent recovery but still with considerable back pain at the end of the follow-up (12%); and those quickly progressing to low level of pain or resolution (12%). Trajectories of average Roland-Morris Disability scores and SF-36 Role of Physical scores for above clusters mapped consistently with the corresponding patterns in pain. However, individuals with fluctuating, recurrent pain patterns showed the shortest cumulative duration on 100% benefit and the earliest return-to-work among other clusters.

Conclusions: Four clinically sensible patterns were identified in this cohort of injured workers, suggesting inter-individual differences in back pain recovery. The results confirm that recurrent or chronic back pain is a typical condition in respondents with new back injuries. Pain intensity and disability scores are good measures of recovery of back pain at the individual level. After initial return-to-work, or cessation of benefits, administrative measures of percentage of respondents back at work, or no longer on benefits, may not accurately reflect an individual’s condition of back pain.