Subacromial impingement syndrome and pain: protocol for a randomised controlled trial of exercise and corticosteroid injection (the SUPPORT trial). BACKGROUND
 Subacromial impingement syndrome is the most frequent cause of shoulder problems which themselves affect 1 in 3 adults.  Management commonly includes exercise and corticosteroid injection.  However, the few existing trials of exercise or corticosteroid injection for subacromial impingement syndrome are mostly small, of poor quality, and focus only on short-term results.  Exercise packages tend to be standardised rather than individualised and progressed.  There has been much recent interest in improving outcome from corticosteroid injections by using musculoskeletal ultrasound to guide injections.  However, there are no high-quality trials comparing ultrasound-guided and blind corticosteroid injection in subacromial impingement syndrome.  This trial will investigate how to optimise the outcome of subacromial impingement syndrome from exercise (standardised advice and information leaflet versus physiotherapist-led exercise) and from subacromial corticosteroid injection (blind versus ultrasound-guided), and provide long-term follow-up data on clinical and cost-effectiveness.


 The study design is a 2x2 factorial randomised controlled trial.  252 adults with subacromial impingement syndrome will be recruited from two musculoskeletal Clinical Assessment and Treatment Services at the primary-secondary care interface in Staffordshire, UK.  Participants will be randomised on a 1:1:1:1 basis to one of four treatment groups: (1) ultrasound-guided subacromial corticosteroid injection and a physiotherapist-led exercise programme, (2) ultrasound-guided subacromial corticosteroid injection and an advice and exercise leaflet, (3) blind subacromial corticosteroid injection and a physiotherapist-led exercise programme, or (4) blind subacromial corticosteroid injection and an advice and exercise leaflet.  The primary intention-to-treat analysis will be the mean differences in Shoulder Pain and Disability Index (SPADI) scores at 6 weeks for the comparison between injection interventions and at 6 months for the comparison between exercise interventions.  Although independence of treatment effects is assumed, the magnitude of any interaction effect will be examined (but is not intended for the main analyses).  Secondary outcomes will include comparison of long-term outcomes (12 months) and cost-effectiveness.  A secondary per protocol analysis will also be performed.


 DISCUSSION
 This protocol paper presents detail of the rationale, design, methods and operational aspects of the SUPPORT trial.


 Current controlled trials ISRCTN42399123.
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