Comparison of the Efficacy of Two Different Suprascapular Nerve Block Techniques in Patients With Chronic Shoulder Pain

Chronic shoulder pain (>3 months) is one of the most common musculoskeletal problems leading to psychosocial problems. Its causes include subacromial impingement, tendinosis, calcific tendinitis, complete or partial tendon tears, adhesive capsulitis, subacromial bursitis, glenohumeral osteoarthritis, glenohumeral instability, and acromioclavicular joint pathologies. For the treatment of chronic shoulder pain, conservative or surgical methods can be applied. Suprascapular nerve block (SSNB) is an effective and safe treatment option for pain relief and increases in functional activity in these patients.

The suprascapular nerve (SSN) is a peripheral nerve has both motor and sensory fibers, originates from the ventral rami of C5-C6 nerve roots. SSN passes across the posterior triangle of the neck and through the suprascapular notch enters to the supraspinous fossa. Then it comes to the infraspinous fossa via the spinoglenoid notch. The SSN has 3 sensory branches: a medial subacromial branch passes to the suprascapular notch, a lateral subacromial branch and a posterior glenohumeral branch pass the spinoglenoid notch. These branches supplies 70% of the sensory input to the shoulder.

In the literature, SSNB through suprascapular notch has positive effect on shoulder functions, pain and range of motion (ROM) in patients in the treatment of chronic shoulder pain. There is no study examining the efficacy of SSNB through spinoglenoid notch in the treatment of chronic shoulder pain.Therefore, the investigators planned this randomized trial to compare of the efficiency and safety of two different SSNB techniques (approach through suprascapular notch versus spinoglenoid notch) in treatment of patients with chronic shoulder pain.

Material and methods:

Participants: adult patients (>18 year old) with chronic shoulder pain Inclusion criteria: age ≥ 18 years old, shoulder pain that last more than 3 month, patients with a vas value of ≥ 4 despite treatment (drugs used for analgesia, local injections and physiotherapy methods), shoulder pain defined as non-specific shoulder pain, subacromial impingement syndrome, rotator cuff tendinopathy, adhesive capsulitis, non-traumatic instability, superior labrum anterior and posterior (SLAP) lesion, acromioclavicular pathology, shoulder osteoarthritis.

Exclusion criteria: A history of uncontrolled chronic diseases, e.g., malignant neoplasms, blood dyscrasia, previous surgery history at the affected shoulder, shoulder injection in the last 3 months before treatment, cervical radiculopathy or myelopathy, a previous fracture close to the shoulder region, septic arthritis or local infection in the affected shoulder, anaphylaxis against local anesthetics and/or corticosteroids, cardiac pacemaker, pregnancy.

Study Design: prospective, double blind, non-inferiority, randomized controlled trial Randomization method: 1:1 by computer randomization program

Detail of the intervention:

Experimental: SSNB through the spinoglenoid notch US guided 1ml methylprednisolone acetate (1ml / 40mg) and 5ml 0.5% bupivacaine Intervention: Medication: corticosteroids and local anesthetics Active comparator: SSNB through the suprascapular notch US guided 1ml methylprednisolone acetate (1ml / 40mg) and 5ml 0.5% bupivacaine Intervention: Medication: corticosteroids and local anesthetics

Outcome measurement:

Visual analogue scale of pain, active range of motion, shoulder pain and disability index (SPADI), Pain Pressure Threshold (PPT), Patient satisfaction

Statistical analyses:

Sample size calculation:

The sample size was calculated using http://statulator.com/SampleSize/ss2M.html considering a previous study. The non-inferiority margin for SPADI was taken as 9 points. Standard deviation 15.3 (assuming normal distribution) with a power of 80, an error of 0.05 type 1; 36 patients should be enrolled per groups. Including a rate of 10% drop-out 40 patients were planned to enroll in each groups.

Continuous variables

1. Student's t test: fit assumption of normal distribution
2. Mann-Whitney test: does not fit the assumption of normal distribution Categorical variables
3. Chi-square test 2. Fisher exact test: sparse data

The outcome differences within the experimental and active comparator groups of different time of evaluation will be analysed by using repeated-measures analysis of variance (ANOVA) with post hoc test with Bonferroni method.