Pressure Pain Sensitivity in Subacromial Pain Syndrome Shows No Link to Structural Abnormalities

Overview

This cross-sectional study found no significant differences in pressure pain thresholds (PPT) among patients with chronic subacromial pain syndrome categorized by normal imaging, rotator cuff tear, or other structural shoulder pathologies. Both primary hyperalgesia at the painful shoulder and secondary hyperalgesia at a remote site showed no correlation with structural abnormalities.

Background

Subacromial pain syndrome (SAPS) is a common cause of shoulder pain and often leads to chronic symptoms lasting beyond three months. Chronic musculoskeletal pain can be classified as primary or secondary, with secondary pain arising from identifiable structural or inflammatory causes such as rotator cuff tears. Pressure pain threshold (PPT) testing is used to assess hyperalgesia, which may reflect nervous system sensitization. Understanding the relationship between structural pathology and pain sensitivity could clarify mechanisms underlying chronic shoulder pain and guide treatment.

Data Highlights

Key Findings

• No significant difference in primary hyperalgesia (pressure pain threshold at the painful shoulder) among patients with normal imaging, rotator cuff tears, or other structural pathologies.
• No significant difference in secondary hyperalgesia (pressure pain threshold at contralateral tibialis anterior) among the imaging groups.
• Structural shoulder abnormalities examined were not associated with differences in pressure pain sensitivity measures.
• Findings suggest that hyperalgesia in chronic subacromial pain syndrome may not be directly related to the presence or type of structural pathology.
• The study controlled for confounders including age, sex, education level, and pain duration in the analysis.

Clinical Implications

Clinicians should recognize that pressure pain sensitivity in chronic subacromial pain syndrome patients may not correlate with imaging findings of structural damage. This suggests that treatment approaches focusing solely on structural abnormalities might overlook central sensitization or nociplastic pain mechanisms. Comprehensive pain management should consider both peripheral and central contributors to chronic shoulder pain.

Conclusion

Pressure pain sensitivity, as measured by PPT, does not differ significantly among patients with chronic subacromial pain syndrome regardless of structural shoulder pathology. These results highlight the complex nature of chronic shoulder pain and the potential role of nervous system sensitization independent of tissue damage.

References

1. Parent Study NCT03752619 -- Efficacy of Implanted Peripheral Nerve Stimulation for Chronic Shoulder Pain
2. Cohen et al. 2021 -- Classification Framework for Chronic Musculoskeletal Pain