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

Objective

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

Design

This study was designed as a prospective 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 shoulder impingement syndrome and at least 6 months of shoulder pain, planned to undergo ultrasound-guided subacromial corticosteroid injection, were included in the study.

Interventions

Not applicable.

Main Outcome Measure(s)

Treatment response was defined as a ≥50% reduction in pain (visual analog scale [VAS]) at 4 weeks postinjection. The presence of CS was assessed using the Central Sensitization Inventory (CSI) and pressure pain threshold via algometry (ipsilateral deltoid, contralateral deltoid, and contralateral vastus lateralis). Negative thoughts related to pain were evaluated with the pain catastrophizing scale, and mood status was assessed using the Hospital Anxiety and Depression Scale (HADS).

Results

Forty-eight patients (responders) experienced ≥50% VAS reduction, whereas 24 (nonresponders) did not. Nonresponders had significantly higher CSI (P=.000), HADS depression (P=.001), and HADS anxiety (P=.000) scores. The pressure pain threshold values were significantly lower in nonresponders at ipsilateral deltoid (P=.030), contralateral deltoid (P=.045), and contralateral vastus lateralis (P=.036). The CSI was significantly correlated with pressure pain threshold at ipsilateral deltoid (r=-0.400, P=.001), contralateral deltoid (r=-0.354, P=.002), and contralateral vastus lateralis (r=-0.442, P=.000); pain catastrophizing scale total score (r=0.449, P=.000); HADS depression score (r=0.572, P=.000); and HADS anxiety score (r=0.618, P=.000). CSI was the most predictive factor for nonresponse area under the curve (AUC=0.755, 95% confidence interval [CI]: 0.635-0.875). Multivariate analysis identified CSI as an independent predictor (P=.022), with a predictive accuracy of 72.2%.

Conclusions

Inadequate response to subacromial corticosteroid injection in chronic shoulder impingement syndrome is strongly associated with CS, psychological distress, and altered pain perception. Integrating CS-targeted interventions into treatment strategies may improve outcomes.