The purpose of this prospective, observational study is to evaluate the clinical and functional outcomes of ultrasound-guided Pericapsular Nerve Group (PENG) block in patients suffering from chronic shoulder pain. Chronic shoulder pain is a highly prevalent musculoskeletal problem that significantly restricts daily activities and diminishes the patient's quality of life. While conservative treatments and various interventional injections are widely used, long-term efficacy can be limited, and systemic side effects may occur. The shoulder PENG block is a novel regional analgesia technique that specifically targets the articular (sensory) branches of the nerves innervating the shoulder joint capsule without affecting the motor branches. In this single-center study, a total of 45 eligible adult patients with chronic shoulder pain who did not respond to conservative medical treatments will receive an ultrasound-guided PENG block as part of their routine clinical care. The procedure will be performed under sterile conditions using a combination of local anesthetic (lidocaine) and dexamethasone. Patient pain levels will be assessed using the Numerical Rating Scale (NRS), shoulder disability and functional status will be measured using the Shoulder Pain and Disability Index (SPADI), and overall patient satisfaction will be evaluated using the Global Perceived Effect (GPE) score. All parameters will be documented at baseline (before the procedure) and at follow-up visits on the 1st week, 4th week (1 month), and 3rd month post-procedure. The investigators aim to determine the efficacy, duration of effect, and safety profile of this intervention.

Study Design and Setting:

This is a prospective, observational, and single-center clinical study designed to evaluate the clinical and functional outcomes of ultrasound-guided Pericapsular Nerve Group (PENG) block in patients with chronic shoulder pain. The study will be conducted in accordance with the Declaration of Helsinki, and approval from the local clinical research ethics committee will be obtained prior to patient enrollment.

Patient Selection:

Adult patients (aged over 18 years) presenting with chronic shoulder pain lasting longer than 3 months, who have an initial Numerical Rating Scale (NRS) score greater than 4 and have not responded to conservative or medical treatments, will be screened for eligibility. Written informed consent will be obtained from all participating individuals. Patients with coagulation disorders, psychomotor disorders, active infections at the injection site, a history of shoulder surgery within the past 6 months, or known allergies to local anesthetics or corticosteroids will be excluded.

Intervention Protocol:

The ultrasound-guided shoulder PENG block is performed as a routine treatment modality in our clinic for patients non-responsive to conservative therapies. The procedure is conducted under sterile conditions with the patient in the supine position. The affected shoulder is placed in abduction and external rotation. An ultrasound transducer is positioned parallel to the clavicle to visualize the anatomical structures. A block needle is advanced under the subscapularis muscle under direct ultrasound guidance. Following the confirmation of correct needle positioning, a mixture of 5 mL of 2% lidocaine and 8 mg of dexamethasone is injected into the periarticular nerve endpoints. Outcome Measurements and Data Collection:

Demographic and clinical data will be collected by an expert algologist using the hospital information management system and recorded into dedicated study forms. Clinical parameters will be evaluated at four distinct time points: baseline (pre-procedure), 1st week, 4th week (1 month), and 3rd month post-procedure. Pain severity will be measured using the Numerical Rating Scale (NRS). Shoulder joint function and disability levels will be assessed using the Shoulder Pain and Disability Index (SPADI). Overall patient satisfaction and perceived improvement will be tracked via the Global Perceived Effect (GPE) scale.

Friedman test, depending on the distribution properties. Bonferroni correction will be applied for post-hoc pairwise comparisons, and a p-value less than 0.05 will be considered statistically significant.

Inclusion Criteria:

• Age 18 years or older.
• Patients presenting with chronic shoulder pain lasting longer than 3 months.
• Initial pain intensity score greater than 4 on the Numerical Rating Scale (NRS > 4).
• Patients who have not responded to conservative or medical treatments.
• Voluntary acceptance of the ultrasound-guided shoulder PENG block treatment and compliance with the scheduled follow-up protocol.

Exclusion Criteria:

• Patients currently using anticoagulants or diagnosed with coagulation disorders (bleeding diathesis).
• Patients with psychomotor or cognitive disorders that prevent cooperative evaluation.
• Presence of active bacterial infection, open wounds, or infectious discharge at the planned needle injection site.
• History of shoulder surgery at the intervention site within the last 6 months.
• Known allergy or hypersensitivity to local anesthetics (lidocaine) or corticosteroids (dexamethasone).
• Pregnant or breastfeeding patients.
• Patients who reject the procedure or fail to comply with the scheduled follow-up visits.