The prognostic value of functional capacity evaluation in patients with chronic low back pain: part 2: sustained recovery.

STUDY DESIGN

Historical cohort study.

OBJECTIVES

We investigated the ability of the Isernhagen Work Systems' Functional Capacity Evaluation to predict sustained recovery.

SUMMARY OF BACKGROUND DATA

Functional Capacity Evaluation is commonly used to determine readiness or ability for safe return to work following musculoskeletal injury, implying a low risk of future recurrence or "reinjury." However, this theoretical construct has not yet been tested.

METHODS

Workers' compensation claimants who underwent Functional Capacity Evaluation following low back injury and subsequently demonstrated recovery in the form of suspension of total temporary disability benefits or claim closure were studied. The number of failed tasks and performance on the floor-to-waist lift task in the protocol were used as indicators of Functional Capacity Evaluation performance. Indicators of sustained recovery included whether or not total temporary disability benefits restarted, the claim was reopened, or a new back claim was filed. Logistic regression was used to determine the prognostic effect of Functional Capacity Evaluation alone and after controlling for suspected confounding variables.

RESULTS

Overall, 46 of 226 patients (20%) experienced a recurrent back-related event within the year following Functional Capacity Evaluation. Opposite to the initial hypothesis, a lower number of failed Functional Capacity Evaluation tasks was consistently associated with higher risk of recurrence after controlling for potential confounding variables. Performance on the floor-to-waist lift task was not related to future recurrence.

CONCLUSIONS

Contrary to Functional Capacity Evaluation theory, better Functional Capacity Evaluation performance as indicated by a lower number of failed tasks was associated with higher risk of recurrence. The validity of Functional Capacity Evaluation's purported ability to identify claimants who are "safe" to return to work is suspect.