Predictors of response to physical therapy intervention for plantar heel pain.

BACKGROUND Age, weight, and duration of symptoms have been associated with a poor response to treatment for plantar heel pain (PHP), but no studies were identified that examined predictors of response to physical therapy intervention. The purpose of this investigation was to examine the influence of age, body mass index (BMI), and symptom duration on treatment response to physical therapy intervention. METHODS Sixty participants received 6 visits over 4 weeks of physical therapy intervention that included manual therapy and exercise or electrophysiological agents and exercise. Outcomes were assessed using the Foot and Ankle Ability Measure (FAAM), Numeric Pain Rating Scale (NPRS), and Global Rating of Change Scale (GRC). Logistic regression (P < .05) was used to analyze age, BMI, and symptom duration as potential predictors of a successful response based on the minimal clinically important difference of the outcome measures. Sensitivity analysis was used to assess the influence of success based on minimal clinically important changes in the FAAM, NPRS, and GRC or only the FAAM and NPRS. Receiver operating curves were used to determine the cut point for the significant predictor. RESULTS At the 6-month follow-up to physical therapy intervention, NPRS was improved by 3 points (95% CI, 2.4-3.6) and FAAM improved by 22.5 points (95% CI, 16.8-28.2). Individuals with symptoms less than 7.2 months were 4.2 (95% CI, 1.3-13.8; P = .016) and 8.5 (95% CI, 2.5-28.9; P = .001) times more likely to respond to treatment based on the NPRS/FAAM/GRC and NPRS/FAAM success criteria, respectively. Age and BMI were not significant predictors (P ≥ .455 and P ≥ .450, respectively). CONCLUSION Age and BMI were not associated with outcomes and obese individuals did achieve a successful outcome with the physical therapy intervention used in the clinical trial. Individuals with PHP symptoms longer than 7 months require additional consideration and further investigation of effective strategies to improve treatment response. LEVEL OF EVIDENCE Prognosis, level 2b comparative study.