Feasibility cluster randomised controlled trial evaluating a theory-driven group-based complex intervention versus usual physiotherapy to support self-management of osteoarthritis and low back pain (SOLAS)

Background: The self-management of osteoarthritis (OA) and low back pain (LBP) through activity and skills (SOLAS) theory-driven group-based complex intervention was developed primarily for the evaluation of its acceptability to patients and physiotherapists and the feasibility of trial procedures, to inform the potential for a definitive trial.

Methods: This assessor-blinded multicentre two-arm parallel cluster randomised controlled feasibility trial compared the SOLAS intervention to usual individual physiotherapy (UP; pragmatic control group). Patients with OA of the hip, knee, lumbar spine and/or chronic LBP were recruited in primary care physiotherapy clinics (i.e. clusters) in Dublin, Ireland, between September 2014 and November 2015. The primary feasibility objectives were evaluated using quantitative methods and individual telephone interviews with purposive samples of participants and physiotherapists. A range of secondary outcomes were collected at baseline, 6 weeks (behaviour change only), 2 months and 6 months to explore the preliminary effects of the intervention. Analysis was by intention-to-treat according to participants' cluster allocation and involved descriptive analysis of the quantitative data and inductive thematic analysis of the qualitative interviews. A linear mixed model was used to contrast change over time in participant secondary outcomes between treatment arms, while adjusting for study waves and clusters.

Results: Fourteen clusters were recruited (7 per trial arm), each cluster participated in two waves of recruitment, with the average cluster size below the target of six participants (intervention: mean (SD) = 4.92 (1.31), range 2-7; UP: mean (SD) = 5.08 (2.43), range 1-9). One hundred twenty participants (83.3% of n = 144 expected) were recruited (intervention n = 59; UP n = 61), with follow-up data obtained from 80.8% (n = 97) at 6 weeks, 84.2% (n = 101) at 2 months and 71.7% (n = 86) at 6 months. Most participants received treatment as allocated (intervention n = 49; UP n = 54). The qualitative interviews (12 participants; 10 physiotherapists (PTs) found the intervention and trial procedures acceptable and appropriate, with minimal feasible adaptations required. Linear mixed methods showed improvements in most secondary outcomes at 2 and 6 months with small between-group effects.

Conclusions: While the SOLAS intervention and trial procedures were acceptable to participants and PTs, the recruitment of enough participants is the biggest obstacle to a definitive trial.

Trial registration: ISRCTN ISRCTN49875385 . Registered on 26 March 2014.

Keywords: Behaviour change intervention; Complex group intervention; Feasibility cluster randomised controlled trial; Intervention mapping; Low back pain; Osteoarthritis; Physiotherapists; Primary care; Qualitative methods; Self-management.