High-frequency Short-course Extracorporeal Shock Wave Therapy for Partial Rotator Cuff Tears: Study Protocol for a Multicenter, Randomized, Controlled Trial

1. Study Background Partial rotator cuff tears are extremely prevalent musculoskeletal disorders, affecting 20-30% of the general population and over 40% of people aged 60 and above. The condition causes persistent shoulder pain, night pain and restricted shoulder movement, interfering with daily activities and quality of life. International clinical guidelines recommend conservative treatment as the first choice for this disease to avoid surgical risks such as infection and tissue adhesion.

Extracorporeal shock wave therapy (ESWT) is a widely used non-invasive physical therapy for tendon injuries. It promotes blood circulation, tendon repair and pain relief. However, the conventional low-frequency ESWT plan (one session per week for 7 weeks) has obvious drawbacks: slow symptom relief, long treatment cycle and poor patient adherence. Early single-center research has confirmed that a daily high-frequency short-course ESWT works better for pain control, functional recovery and tendon healing, with good safety. This formal multicenter trial is designed to verify these findings and further optimize treatment protocols. 2. Study Objectives Primary goal: Compare the efficacy of two high-frequency ESWT regimens and the conventional regimen in reducing shoulder pain of patients with partial rotator cuff tears at 3 months after treatment.

Secondary goals: Evaluate the improvements of shoulder joint function and range of motion; use MRI and ultrasound to objectively assess tendon repair status; analyze patient treatment compliance and incidence of adverse reactions; develop an optimized, evidence-based ESWT standard protocol for clinical promotion. 3. Study Design \& Participants Study Design This is a prospective, multicenter, three-arm parallel-group randomized controlled trial with outcome assessor blinding. Participants will be randomly divided into three groups at a 1:1:1 ratio. All treatment groups adopt identical ESWT technical parameters: 2000 shocks per session, 10 Hz frequency, energy flux density of 0.1-0.25 mJ/mm².

Three Treatment Groups Group 1 (High-frequency short-course group): Receive ESWT once a day for 7 consecutive days (7 sessions in total within 1 week).

Group 2 (High-frequency intensive group): Complete 3 treatment cycles. Each cycle includes 7 consecutive daily ESWT sessions, with a 1-week rest between cycles (21 sessions in total within 7 weeks).

Group 3 (Conventional group/control): Receive ESWT once a week for 7 consecutive weeks (7 sessions in total within 7 weeks).

Eligibility Criteria Inclusion Criteria Aged 30 to 70 years, regardless of gender. Diagnosed with partial-thickness rotator cuff tear or small non-retracted full-thickness rotator cuff tear via MRI or high-resolution ultrasound.

Shoulder pain lasting for at least 3 months, with a pain score (VAS) of 4 points or higher (0-10 scale).

Voluntarily join the study and sign written informed consent, and agree to complete all treatments and follow-up visits.

Exclusion Criteria Severe full-thickness rotator cuff tear, tendon retraction above Grade II, or greater tuberosity bone cyst.

Severe muscle fatty infiltration of the shoulder (Goutallier grade ≥3) shown on MRI.

Poorly controlled diabetes, hypothyroidism, or heavy long-term smoking. Received local injections (corticosteroids, platelet-rich plasma etc.) on the affected shoulder within the past 4 weeks.

Combined with severe shoulder osteoarthritis, frozen shoulder, shoulder instability, rheumatoid arthritis, bleeding disorders or coagulation problems.

Pregnant or breastfeeding women; patients with cardiac pacemakers or tumors at the treatment site (contraindications for ESWT).

Unable to finish the full course of treatment or follow-up arrangements. Recruitment Scale \& Centers A maximum of 300 participants will be enrolled from 10 tertiary hospitals nationwide, including Peking University Third Hospital, Beijing Chao-Yang Hospital, West China Hospital of Sichuan University and other renowned medical institutions. The recruitment period lasts from January 2026 to December 2027. 4. Combined Care \& Follow-up Arrangements All participants will receive unified guidance on daily activity adjustment and home rehabilitation exercises. Oral pain-relieving anti-inflammatory drugs are allowed and will be recorded, while other physical therapies (ultrasound, laser, massage etc.) are prohibited during treatment.

Follow-up time points: Baseline (before treatment), 3 months, 6 months and 12 months after treatment. At each follow-up, researchers will assess pain degree, shoulder function and joint mobility. MRI and ultrasound re-examinations will be conducted at baseline, 6 months and 12 months to evaluate tendon healing. All adverse reactions during treatment and follow-up will be recorded in detail. 5. Evaluation Indicators Primary indicator: Changes of shoulder pain score (VAS) from baseline to 3 months after intervention.

Secondary indicators:

Shoulder function scores (ASES, Constant-Murley Score) and active/passive joint range of motion.

Imaging indicators: Changes of tendon signal-to-noise ratio, tear size and tendon thickness detected by MRI and ultrasound.

Treatment adherence: The proportion of participants who complete the scheduled treatment sessions.

Safety indicators: Types, quantity and severity of adverse events (local redness, swelling, skin petechiae, transient pain aggravation etc.).

Patients' overall subjective evaluation of symptom improvement. 6. Study Strengths \& Implementation Notes To avoid assessment bias, the staff responsible for evaluating curative effects and reading imaging images will not know which treatment group each participant belongs to.

All operating procedures, assessment standards and imaging measurement methods are unified across all participating hospitals to ensure data accuracy and consistency.

This study is the first multicenter trial comparing high-frequency short-course ESWT and conventional regimens for partial rotator cuff tears. It combines subjective symptom scores and objective imaging biomarkers to obtain reliable clinical evidence.

After the trial ends, the research team will form a set of optimized ESWT application specifications, which will be promoted to clinical departments such as rehabilitation and sports medicine to provide a better non-surgical treatment option for patients with partial rotator cuff tears. 7. Ethical Statement The study strictly follows the Declaration of Helsinki and clinical trial norms. The protocol has passed the ethical review of all participating hospitals. All participants have the right to withdraw from the study at any time without penalty. Personal medical information of all participants will be encrypted and kept confidential to protect privacy.

• American Shoulder and Elbow Surgeons (ASES) Score [Time frame: Baseline, 3 months, 6 months, 12 months post-treatment]
• Constant-Murley Score (CMS) [Time frame: Baseline, 3 months, 6 months, 12 months post-treatment]
• Shoulder Range of Motion (ROM) [Time frame: Baseline, 3 months, 6 months, 12 months post-treatment]
• MRI Signal-to-Noise Ratio (SNR) of Rotator Cuff Tendon [Time frame: Baseline, 6 months, 12 months post-treatment]