Minimal clinically important difference of the functional independence measure in older adults with hip fracture

To investigate the responsiveness and minimal clinically important difference (MCID) of the Functional Independence Measure (FIM) from a clinician's perspective in hip-fractured elderly undergoing inpatient rehabilitation.

Data of 701 hip-fractured elderly admitted to our rehabilitation institute were retrospectively collected. Ten a priori hypotheses were formulated.

The effect size of the FIM scores after treatment were large (total = 1.38, motor = 1.78). Moderate correlations were found between the change total score of FIM and Barthel Index (BI, r_s = 0.51), Functional Ambulation Categories (FAC, r_s = 0.52) and a checklist regarding participants' independence in transfers (r_s = 0.59). The area under the receiving operating characteristics were 0.82, 0.81, and 0.85 when BI, FAC and checklist were used as anchors, respectively. Based on these findings, the FIM showed high responsiveness (9/10 hypotheses met). Triangulation of findings showed that MCIDs of 22 and 21 points were the most appropriate for the FIM total and motor score, respectively.

The FIM scale is appropriate for assessing independence and functional recovery in hip-fractured elderly. Improvements of 22 and 21 points at the total and motor FIM were identified as indicators of minimal clinical change in those admitted to a rehabilitation facility with an FIM total score between 40 and 80.