183. Role of psychosocial factors on the effect of physical activity on physical function in patients after lumbar spine surgery

Abstract

<h3>BACKGROUND CONTEXT</h3> Engaging in physical activity early after lumbar spine surgery has promising effects on long-term postoperative recovery, including improved physical function. However, whether this effect is mediated through improvement in psychosocial factors is yet to be established. <h3>PURPOSE</h3> The purpose of this study was to investigate the longitudinal postoperative relationship between physical activity, psychosocial factors, and physical function in patients undergoing lumbar spine surgery. <h3>STUDY DESIGN/SETTING</h3> Secondary analysis from randomized controlled trial. <h3>PATIENT SAMPLE</h3> This study included 248 participants (mean ± SD; age=62.2±11.9 years; BMI=32.4±6.6 kg/m² and 51% females) who underwent surgery for a degenerative lumbar spine condition. <h3>OUTCOME MEASURES</h3> Physical activity, defined as steps per day, was measured using a triaxial accelerometer (Actigraph GT3X) worn for >10 hours for >1 day(s) at 6 weeks (6wk), 6 months (6M), 12 months (12M) and 24 months (24M) following spine surgery. Physical function, measured with Patient-Reported Outcomes Measurement Information System, and psychosocial factors pain self-efficacy [Pain Self-Efficacy Questionnare], depression [Patient Health Questionnaire-9] and fear of movement [Tampa Scale for Kinesiophobia]) were assessed at preoperative visit and 6wk, 6M, 12M and 24M after surgery. <h3>METHODS</h3> Structural equation modeling (SEM) was used to analyze data and compute standardized coefficients to determine the effects of physical activity, function and psychosocial factors. Multiple imputation accounted for missing data and pooled coefficients and p-values were calculated using Rubin's approach. The mediation effect of each psychosocial factor on the effect of physical activity on physical function were computed by dividing the direct effects with the indirect effects. All SEM models controlled for age, employment, comorbidities, prior spine surgery, and preoperative pain self-efficacy, depression, fear of movement, physical function, and back and leg pain. Each SEM models was tested for model fit by assessing the established fit indexes. <h3>RESULTS</h3> The overall standardized direct effect of physical activity (ie, steps per day) on physical function ranged from 0.08 to 0.19 (p<0.05), while the overall effect of physical function on physical activity ranged from non-existent to 0.14 (p<0.01 to 0.3). The effect of physical activity on physical function remained consistent after accounting for psychosocial factors in each of the mediation models. Pain self-efficacy did not mediate but depression and fear of movement at 6M mediated 3.4% and 5.4% of the effect of physical actvity at 6Wk on physical function at 12M, respectively. <h3>CONCLUSIONS</h3> The findings of this study support the use of early postoperative strategies to address physical activity in order to improve long-term physical function. Pain self-efficacy did not have a mediating effect while depression and fear of movement had a very small mediating effect; therefore, additional work is needed to investigate other potential mediating factors such as pain catastrophizing, resilience and exercise self-efficacy. <h3>FDA DEVICE/DRUG STATUS</h3> This abstract does not discuss or include any applicable devices or drugs.