Comparison of Ultrasound-Guided Subacromial Vs. Systemic Steroid Injections for Frozen Shoulder: a Multicenter Pilot Study

The goal of this multicenter pilot study is to validate the effectiveness of extending the injection interval between betamethasone doses from one to two weeks for treating frozen shoulder (adhesive capsulitis) in adults aged 18 to 75. This study also aims to screen potential study centers and gather data to refine the sample size calculation for a larger, future trial. The main questions it aims to answer are:

* Does extending the interval between injections maintain effectiveness in improving shoulder function and reducing pain for frozen shoulder?
* Which centers in this pilot study are qualified for a larger, future trial?
* What is the appropriate sample size for conducting a multicenter RCT study with the same research design at the selected centers?

Participants will:

* Receive 3 injections over 4 weeks and will be followed up for another 8 weeks
* Complete shoulder function assessments
* Perform home rehabilitation exercises


Eligibility Criteria:
Inclusion Criteria:

1. History of ≤9 months, clinically diagnosed with primary frozen shoulder (including frozen shoulder associated with diabetes).
2. Aged between 18 and 75 years old
3. Pain NRS score ≥4
4. Measured passive range of motion of the affected shoulder in at least two of the three directions (forward flexion, external rotation with arm at the side, and internal rotation with arm at the side) is reduced by 25% or more compared to the contralateral normal shoulder.
5. Exclusion of osteoarthritis, dislocation, and other shoulder abnormalities through X-ray and MRI of the affected shoulder.

Exclusion Criteria:

1. Secondary frozen shoulder caused by thyroid disease, cardiovascular disease, cancer, stroke, radiotherapy, neurosurgery, or breast surgery (excluding diabetes); secondary frozen shoulder caused by major shoulder trauma requiring medical care (e.g., fractures, dislocations, rotator cuff tears).
2. Full-thickness rotator cuff tear in the affected shoulder confirmed by MRI (excluding rotator cuff tendinopathy and partial-thickness rotator cuff tear in patients with frozen shoulder without a history of major shoulder trauma).
3. Patients unable to undergo MRI due to financial reasons, claustrophobia, pacemaker, or other metallic implants in the body.
4. Local infection in the affected shoulder or other contraindications to shoulder injections.
5. Patients with contraindications to steroid therapy (e.g., poorly controlled blood sugar in diabetes).
6. Patients with frozen shoulder who have already undergone shoulder injections, manipulation under anesthesia, arthroscopic capsular release, or open surgery for capsular release.
7. Received any form of steroid treatment within the past 3 months.
8. History of glucocorticoid use for more than 3 months.
9. Bilateral frozen shoulder or a history of frozen shoulder in the contralateral shoulder.
10. Pregnant or breastfeeding women.
11. Patients lacking the cognitive ability to comply with the study protocol.
12. Patients not residing in the area where the study is being conducted.
13. Patients with compensation claims or legal disputes related to workplace injury or car accidents.