Predictors of Sustained Response to Functional Restoration in a Military Population

Introduction: The purpose of this study was to determine if improvement in pain impact and functional performance following a functional restoration (FR) program was sustained up to 6months posttreatment and to identify predictors of sustained improvement. Materials and Methods: Secondary analysis of data collected during randomized clinical trial. Study population included 108US active duty service members who completed an FR program, as well as 3- and/or 6-month follow-up assessments. Primary outcome measure was the NIH Research Task Force (pain) impact score (PIS). Secondary outcome was a composite functional performance measure of treadmill, lifting, and carrying tolerances. Variables analyzed to determine their predictive value included demographics; treatment hours; measures of pain intensity, function, mood, sleep, social satisfaction, pain catastrophizing, kinesiophobia, self-efficacy, pain acceptance, patient activation, functional performance, and neuropathic pain. Results: Mean PIS and functional performance improved significantly immediately following FR, but after 6months, only improvement in functional performance sustained. Responder analysis showed that 6months after FR, 42% of participants reported improvement that exceeded the minimal clinically important difference in PIS or functional performance. Predictors of sustained PIS improvement included younger age, absence of neuropathic pain features, less self-rated disability, better baseline functional performance, and worse baseline PIS. Predictors of sustained functional performance improvement included more treatment hours, lower baseline pain catastrophizing, and lower baseline functional performance. Conclusions: This study supports the investment of treatment time in FR to yield sustained clinically meaningful improvement, as observed in over 40% of this study's military participants. Pretreatment predictors of sustained response included lower pain catastrophizing and absence of neuropathic pain. Further research is needed to determine if treatments that improve pain catastrophizing and neuropathic pain will result in sustained improvement in pain impact and functional performance following FR program participation.