Immediate response to injection is associated with conservative care outcomes at 12 weeks in subacromial shoulder pain.

Background: Subacromial injection is known to influence pain of subacromial origin, yet its association with conservative care outcomes is unknown. This study investigated whether immediate response to subacromial injection of corticosteroid and local anaesthetic is associated with conservative care outcomes at 12 weeks post injection and/or progression to surgery.
Design: prospective prognostic cohort study.
Methods: Sixty-four participants with subacromial related shoulder pain attending initial orthopaedic outpatient appointment at an Australian public hospital, received subacromial injection of corticosteroid and local anaesthetic followed by up to 12 weeks of physiotherapy. Immediate response to injection was measured by change in shoulder range of motion (ROM) and pain immediately (within 20 min) before and after injection. The Shoulder Pain and Disability Index (SPADI) was measured at baseline, 6 and 12-weeks.
Results: Backward stepwise linear regression revealed immediate post-injection improvement in pain-free ROM (p = 0.001) and higher baseline symptoms (p = 0.016) were significantly associated with better 12-week SPADI outcomes. Longer symptom duration (p = 0.029) and higher age (p = 0.013) were significantly associated with poorer outcomes. Only 11 individuals progressed to surgery. The resultant model could explain 35% of the variation in change in SPADI at 12 weeks.
Conclusion: Improvement in pain-free shoulder ROM immediately post injection is significantly associated with better 12-week conservative care outcomes. This information, derived from within consultation injection responses, could help inform decisions about potential treatment options. Further research with higher numbers and longer-term patient-reported outcomes could further clarify these findings.
Registration: Australia and New Zealand Clinical Trials Registry 21 May 2012: 12612000532808.
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