This study will compare two different types of anesthesia used for shoulder surgery. The first method, called an interscalene block, is commonly performed by anesthesiologists and is effective for pain control but may cause side effects such as breathing problems, arm weakness, or discomfort. The second method, called a shoulder field block, is a newer technique performed by orthopedic surgeons that numbs the nerves around the shoulder without affecting breathing.

Patients scheduled for shoulder surgery will be randomly assigned to receive either the interscalene block or the shoulder field block. The main goal of the study is to find out whether the shoulder field block provides pain relief that is as effective as the interscalene block, but with fewer side effects.

Pain levels, patient satisfaction, length of hospital stay, need for pain medication, and any complications will be recorded and compared between the two groups. The results may help identify a safe and effective alternative anesthesia option for patients undergoing shoulder surgery.

Regional anesthesia is widely used for shoulder surgery, most commonly with an interscalene brachial plexus block (ISB). While ISB provides effective pain relief, it is associated with side effects such as hemidiaphragmatic paralysis, breathing difficulties, Horner's syndrome, nerve injury, and rebound pain. These risks limit its use in patients with respiratory conditions, obesity, or other contraindications.

A shoulder field block (FB) is a newer approach that targets the suprascapular, axillary, and lateral pectoral nerves, which supply most of the sensation to the shoulder joint. Unlike ISB, the field block does not affect the phrenic nerve, making it a potentially safer option. Cadaveric and early clinical studies suggest that field blocks may provide effective pain relief with fewer complications, but direct comparisons with ISB in surgical patients are limited.

This randomized controlled trial will enroll 64 adult patients undergoing arthroscopic or open shoulder surgery. Patients will be randomized into two groups:

Field Block Group: Local anesthesia field block performed by an orthopedic surgeon using anatomical landmarks.

Interscalene Block Group: Standard interscalene block performed by an anesthesiologist.

The primary outcome will be postoperative pain intensity measured by a numerical rating scale (0-10) at multiple time points during the first 48 hours. Secondary outcomes include patient satisfaction, hospital length of stay, opioid consumption, complications, and unplanned medical visits due to pain.

The study hypothesis is that a shoulder field block will provide pain relief that is non-inferior to an interscalene block, while reducing side effects and improving patient satisfaction. If effective, this technique could offer a practical alternative that can be safely performed by orthopedic surgeons, expanding anesthesia options for shoulder surgery patients.

Inclusion Criteria:

• Age between 18 and 75 years
• Scheduled for arthroscopic or open shoulder surgery

Exclusion Criteria:

• Prior surgery or trauma to the shoulder
• Revision shoulder surgery
• Fibromyalgia
• Pregnancy
• Contraindications to regional anesthesia (e.g., allergy to local anesthetics, coagulopathy, local site infection)
• Preexisting neuropathy or myopathy of the surgical limb
• History of chronic opioid use
• Cognitive impairment or inability to understand pain scoring systems (e.g., dementia)

De-identified individual participant data (IPD) that underlie the results reported in the article, including data tables, will be shared. This includes pain scores (NRS), opioid consumption, complication rates, and patient satisfaction scores.

IPD and supporting documentation will be available beginning 6 months after publication and will remain available for up to 3 years following the publication date.

Qualified researchers with a methodologically sound proposal may request access to the data. Requests should be submitted to the principal investigator via institutional email. Data will be provided through a secure data-sharing platform, after approval of a data use agreement.