Chronic shoulder pain is a condition that typically lasts longer than three months and affects daily life. Among musculoskeletal system pathologies, shoulder pain ranks third after spine and knee pathologies. Patients with chronic shoulder pain often experience significant functional loss and reduced psychosocial well-being. Chronic shoulder pain may originate from instability, rotator cuff pathologies (calcific tendinitis, tendinopathy, full-thickness or partial tears), the acromioclavicular joint, adhesive capsulitis, or the glenohumeral joint. It results in pain, decreased joint range of motion, stiffness, limitations in activities of daily living, and ultimately disability. Musculoskeletal disorders constitute a significant health problem in the aging global population.

Treatment options include patient education, lifestyle modifications, exercise, physical therapy modalities, medical treatments, intra-articular injections, periarticular injections, and suprascapular nerve block. The suprascapular nerve is a large peripheral nerve containing both motor and sensory fibers. It originates from the ventral rami of the C5 and C6 cervical nerve roots and may occasionally receive contributions from the C4 nerve root. The nerve arises from the lateral aspect of the upper trunk of the brachial plexus, passes beneath the omohyoid and trapezius muscles, and reaches the supraspinous fossa by passing under the suprascapular notch. The suprascapular nerve gives motor branches to the supraspinatus muscle and sensory branches to the acromioclavicular joint, coracoclavicular ligament, and the posterior part of the subacromial bursa. Compared with intra-articular injections, suprascapular nerve block has been shown to provide faster and greater effectiveness. This increases patient adherence to exercise, facilitates a quicker return to activities of daily living, and helps prevent further chronicity of the condition.

A 5% dextrose solution is frequently used for perineural injections and has an osmolality similar to normal saline. Although its neural mechanism is not fully understood, it is thought to inhibit vanilloid receptor activation and block the release of substance P and calcitonin gene-related peptide (CGRP). Hypertonic dextrose (>10%) may trigger local inflammation and promote tissue regeneration and symptom relief, while also increasing fibroblast proliferation and stimulating collagen synthesis and tissue healing.

The primary aim of our study is to investigate and compare the effects of 5% and 10% dextrose injections around the suprascapular nerve on pain, joint range of motion, functionality, and kinesiophobia, and to determine their relative superiority. The secondary aim is to evaluate the effects of these injection treatments on supraspinatus muscle and tendon thickness, as well as quality of life, in association with improved adherence to exercise.

Inclusion Criteria:

• Patients over 18 years old with shoulder pain for the past 6 months who have not responded to medical treatment, exercise, corticosteroid injections, or physical therapy modalities, and who are willing to participate in the study.

Exclusion Criteria:

• Patients younger than 18 or older than 75 years
• Patients with a history of surgery on the same shoulder
• Patients with neurological and/or inflammatory diseases
• Patients with serious systemic diseases such as malignancy, end-stage congestive heart failure, or uncontrolled diabetes
• Patients with insufficient cognitive function