Evaluation of Inadequate Response to Ultrasound-Guided Subacromial Corticosteroid Injection in Shoulder Impingement Syndrome: Treatment Failure or Central Sensitization?: Central Sensitization in Injection Response.

Abstract

Objective: To evaluate whether central sensitization (CS), pain catastrophizing, and psychological factors are associated with inadequate response to ultrasound-guided subacromial corticosteroid injection (SCI) in patients with chronic shoulder impingement syndrome (SIS).

Design: This study was designed as a prolective observational study, combining analytical cross-sectional and prospective elements to evaluate associations and treatment responses.

Setting: Secondary care outpatient clinic.

Participants: A total of 72 patients aged 18-75 years with SIS and at least 6 months of shoulder pain, planned to undergo ultrasound-guided SCI, were included in the study.

Interventions: Not applicable.

Main outcome measure(s): Treatment response was defined as a ≥50% reduction in pain (VAS) at 4 weeks post-injection. The presence of central sensitization was assessed using the Central Sensitization Inventory (CSI) and Pressure Pain Threshold (PPT) via algometry (ipsilateral deltoid, contralateral deltoid, and contralateral vastus lateralis). Negative thoughts related to pain were evaluated with the Pain Catastrophizing Scale (PCS), and mood status was assessed using the Hospital Anxiety and Depression Scale (HADS).

Results: 48 patients (responders) experienced ≥50% VAS reduction, while 24 (non-responders) did not. Non-responders had significantly higher CSI (p=0.000), HADS-depression (p=0.001), and HADS-anxiety (p=0.000) scores. PPT values were significantly lower in non-responders at ipsilateral deltoid (p=0.030), contralateral deltoid (p=0.045), and contralateral vastus lateralis (p=0.036). CSI was significantly correlated with PPT at ipsilateral deltoid (r=-0.400, p=0.001), contralateral deltoid (r=-0.354, p=0.002), and contralateral vastus lateralis (r=-0.442, p=0.000); PCS total score (r=0.449, p=0.000); HADS-depression score (r=0.572, p=0.000); and HADS-anxiety score (r=0.618, p=0.000). CSI was the most predictive factor for non-response (AUC=0.755, 95% CI: 0.635-0.875). Multivariate analysis identified CSI as an independent predictor (p=0.022), with a predictive accuracy of 72.2%.

Conclusions: Inadequate response to SCI in chronic SIS is strongly associated with CS, psychological distress, and altered pain perception. Integrating CS-targeted interventions into treatment strategies may improve outcomes.