Subacromial Corticosteroid Injections and tDCS in Rotator Cuff Tendinopathy

Characterization and Temporal Evaluation of the Effects of Subacromial Corticosteroid Injections and Trans-cranial Direct Current Stimulation in Rotator Cuff Tendinopathy

This study evaluates the effects of corticosteroid injections over time, as well as the additional effect provided by subsequent transcranial direct current stimulation (tDCS) of the motor cortex on patients with rotator cuff tendinopathy of the shoulder. All patients will receive a subacromial corticosteroid injection. Two weeks later, a third will receive a treatment of tDCS, a third will receive a placebo a-tDCS treatment, and the last third will not receive any additional treatment.

Corticosteroid injections (CSI) are often used by physicians in the treatment of rotator cuff tendinopathy, a painful chronic degeneration of the tendons in the shoulder. However, the effect of CSI in comparison with placebo is disputed in the scientific literature, with most studies only showing mild short-term effect (less than six weeks) on pain compared to placebo injections.

Transcranial direct current stimulation (tDCS) is a non-invasive technique allowing to stimulate areas of the brain in order to change the excitability of the neurons. When the negative electrode is applied on the motor cortex of the brain, it increases the excitability of the neurons in that area, which in turns inhibits the activity of the thalamus, an area of the brain linked with the perception of pain. Some studies have shown that tDCS can improve chronic pain of different origins, such as lower back pain, fibromyalgia, stroke, osteoarthritis, and post-operative pain.

We tested whether applying tDCS following a CSI would have more effect on patient's pain, function, and activity, than CSI alone.

Inclusion Criteria:

• Shoulder pain for at least 9 months
• Trial of conservative treatment prior to inclusion
• Positive painful arc sign
• At least one positive impingement test (Neer or Hawkin's impingement sign)
• Written and oral comprehension of French and/or English

Exclusion Criteria specific to rotator cuff tendinopathy and CSI:

• Traumatic origin
• Diagnosis of a systemic inflammatory joint disease
• Complete rotator cuff tear on physical examination or MRI
• Diagnosis of acromio-clavicular syndrome
• Presence of cervical nerve root pain or symptoms
• Other confounding pathologies seen clinically or radiographically
• History of previous fracture or surgery at the shoulder
• Contraindication to CSI
• CSI received in the last three months
• Planned or ongoing pregnancy
• Receiving worker's compensation or being involved in litigation relating to the shoulder pathology.
• Inability to follow protocol instructions

Exclusion Criteria specific to tDCS and transcranial magnetic stimulation:

• History of epilepsy or convulsions
• Brain metallic implants or fragments
• Brain lesions or tumors
• Use of a pacemaker or ICD
• Use of an intravenous medication pump
• Severe cardiac disease, or recent cardiac event
• Consumption of medications known to lower the seizure threshold
• Alcoholism
• Severe sleep deprivation
• Eczema or skin lesions at the area of electrode application