Impact of hemodynamics in individual shoulder structures on pain intensity in patients with rotator cuff tear

Rotator cuff tears (RCTs) commonly cause shoulder pain and functional impairment in middle-aged and elderly individuals. Despite their varying clinical presentations, the mechanisms underlying pain development and exacerbation in RCT remain poorly understood. The relationship between increased blood flow around the shoulder joint and pain has recently attracted increasing attention. Dynamic magnetic resonance imaging (MRI) has been established as an imaging study for assessing local hemodynamics in various fields, and we utilized this technique to evaluate hemodynamic changes in the shoulder structures. This study aimed to assess hemodynamic changes in shoulder structures using dynamic MRI in patients with painful RCT and to examine their correlation with motion and nocturnal pain.

We conducted a cross-sectional study of 54 patients with symptomatic full-thickness RCT. Patients underwent dynamic MRI for 3 min, and time-intensity-curve was analyzed to evaluate hemodynamics in the torn tendon stump (Stump), surrounding subacromial bursa (Bursa), rotator interval, axillary pouch (AP), and deltoid muscle. The peak enhancement ratio (PER) and enhanced slope (ESL), which reflect the blood flow volume and velocity, were obtained from the time-intensity-curve. Pain intensity was measured using a 100 mm visual analog scale (VAS) during shoulder motion in daily activities (motion pain) and bedtime at night (nocturnal pain). Chronic pain-related questionnaires were used to assess psychological problems.

Dynamic MRI revealed significantly higher PER and ESL in the Bursa, rotator interval, and AP than in the deltoid muscle. The Stump demonstrated significantly lower PER and ESL than the other structures. The motion pain VAS was positively correlated with PER and ESL in the Bursa and AP, whereas nocturnal pain VAS showed positive correlations with the Bursa and negative correlations with the Stump. There were no significant associations between VAS pain scores and demographic or chronic pain-related questionnaire data.

Abundant hemodynamic activity within the Bursa and AP resulted in severe motion pain that reflected focal bursitis, probably due to subacromial impingement and secondary glenohumeral synovitis. Conversely, opposing hemodynamics, ie reduced vascular perfusion in the Stump and increased vascular perfusion in the Bursa were linked to higher nocturnal pain, suggesting ischemia at the torn tendon and synovitis of the surrounding bursa. These findings highlight the role of local hemodynamics in the pathophysiology of RCT-related pain and provide insights that may help explore new treatment approaches targeting hemodynamic alterations.