Clinical and Economic Evaluation of Point-of-care Ultrasound-guided Infiltration for Subacromial and Carpal Tunnel Syndromes in Primary Care: a Cluster-randomized Study Protocol.

Upper extremity pathologies, particularly subacromial impingement syndrome (SAS) and carpal tunnel syndrome (CTS), represent a significant clinical and socioeconomic burden for primary care systems, primarily due to functional disability and prolonged sick leave.

Although corticosteroid injections are frequently used, traditional blind injections guided by anatomical landmarks often lack anatomical precision. Point-of-care ultrasound-guided injections offer greater accuracy and better short-term clinical outcomes; however, their cost-effectiveness in routine clinical practice has not yet been adequately assessed.

This pragmatic, prospective, multicenter, cluster-randomized clinical trial includes 23 participating primary care centers (clusters) in Lleida, Spain, with a 6-month longitudinal follow-up. This study constitutes the quantitative phase of the mixed-methods Q-EPICAP project.

A total of 225 adult patients diagnosed with SAS or CTS and presenting with baseline pain (VAS ≥ 3) were divided into three parallel groups:

1. Group I: Anatomical landmark-guided infiltration.
2. Group UI: Ultrasound-guided infiltration performed by family physicians.
3. Group P: Standard oral pharmacological treatment.

Data collection was performed at baseline and at 15, 30, 90, and 180 days post-intervention. The primary outcome measure was pain intensity (VAS). Secondary outcomes included upper limb function (ASES and Boston questionnaires), health-related quality of life (EQ-5D-5L), and a comprehensive economic evaluation (cost-effectiveness and cost-utility indices) that integrates the perspectives of healthcare systems and society.

• Standard Oral Treatment (Drug): Prescription of systemic oral pharmacological treatment according to standard clinical practice and guidelines, which may include individual or combined use of the following therapies, or no pharmacological prescription if deemed appropriate by the clinician: 1. Non-steroidal anti-inflammatory drugs (NSAIDs): Ibuprofen (400 mg or 600 mg), Naproxen (500 mg or 550 mg), or Dexketoprofen (25 mg). 2. Non-opioid analgesics: Paracetamol (500 mg, 650 mg, or 1 g) or Metamizole (575 mg). 3. Step 2 weak opioids: Tramadol (50 mg, 100 mg, or 200 mg). 4. Co-analgesics for neuropathic pain components: Gabapentin (300 mg, 400 mg, or 600 mg).
• Conventional Infiltration (Drug): Local infiltration consisting of a combination of a corticosteroid and a local anesthetic, administered in a 1:1 volume ratio (1 ml + 1 ml, total volume 2 ml): 1. Corticosteroid: Betamethasone (administered as 1 ml of solution). 2. Local anesthetic: Mepivacaine (administered as 1 ml of solution). In the Conventional Infiltration group, the solution is injected using the standard anatomical landmark technique (blind technique).
• Ultrasound-Guided Infiltration (Drug): Local infiltration consisting of a combination of a corticosteroid and a local anesthetic, administered in a 1:1 volume ratio (1 ml + 1 ml, total volume 2 ml): 1. Corticosteroid: Betamethasone (administered as 1 ml of solution). 2. Local anesthetic: Mepivacaine (administered as 1 ml of solution). In the Ultrasound-Guided Infiltration group, 1 ml of betamethasone + 1 ml of mepivacaine are administered under real-time ultrasound guidance to ensure precise deposition in the target anatomical structure (subacromial space or carpal tunnel).

Primary outcomes

• Change from Baseline in Pain Intensity using the Visual Analog Scale (VAS) [Baseline (Day 0), 3 months, 6 months, and 9 months post-intervention.]: Pain intensity will be assessed using the Visual Analog Scale (VAS), where patients rate their pain on a line from 0 (no pain) to 10 (worst possible pain). The primary endpoint is the change in the score from baseline to 3, 6, and 9 months. Higher scores indicate greater pain intensity.

Secondary outcomes

• Change from Baseline in Shoulder Function using the American Shoulder and Elbow Surgeons (ASES) Score [Baseline (Day 0), 3, 6, and 9 months post-intervention.]: The ASES score evaluates shoulder pain and activities of daily living. It consists of a patient-reported section (10 items) and a clinical assessment. The total score ranges from 0 to 100, where 100 indicates better shoulder function and less pain. We will assess the change in this score relative to baseline.
• Change from Baseline in Carpal Tunnel Symptoms and Function using the Boston Carpal Tunnel Questionnaire (BCTQ) [Baseline (Day 0), 3, 6, and 9 months post-intervention.]: The BCTQ consists of two scales: the Symptom Severity Scale (11 items) and the Functional Status Scale (8 items). Each item is scored from 1 (mildest) to 5 (most severe). The final score is the average of the responses. Higher scores indicate more severe symptoms and greater functional impairment.
• Change from Baseline in Health-Related Quality of Life (EQ-5D-5L) [Baseline (Day 0), 3, 6, and 9 months post-intervention.]: The EQ-5D-5L questionnaire assesses 5 dimensions of health (mobility, self-care, usual activities, pain/discomfort, and anxiety/depression) across 5 levels of severity. It also includes a Visual Analog Scale (EQ-VAS) from 0 (worst imaginable health) to 100 (best imaginable health). Higher index values and VAS scores represent better health status.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Patients aged 18 years or older presenting in primary care. Clinical diagnosis of subacromial impingement syndrome (shoulder pain from tendon compression) or carpal tunnel syndrome (wrist nerve compression). Moderate to severe pain intensity, defined as a score of greater than or equal to 3 on the Visual Analog Scale (VAS >= 3) at baseline. Patient must understand the study procedures and provide written informed consent.

Exclusion Criteria:

* Previous corticosteroid infiltration in the target joint/structure within the last 6 months. History of major trauma, active infection, or previous surgery in the affected shoulder or wrist. Underlying systemic inflammatory diseases (for example, rheumatoid arthritis, polymyalgia rheumatica). Known hypersensitivity or contraindications to corticosteroids (Betamethasone) or local anesthetics (Mepivacaine). Pregnancy or breastfeeding. Red flags suggesting tumor, fracture, or severe neurological deficit.

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• Marta Ortega Bravo, MD, PhD, Principal investigator, Institut Català de la Salut. Instituto Universitario de Investigación en Atención Primaria (IDIAP Jordi Gol)