Subacromial injection is considered one of the best treatments for patients with subacromial impingement syndrome. The subacromial bursa is located between the deltoid muscle and the supraspinatus tendon. It facilitates the gliding of the humeral head through the undersurface of the acromion. If the bursa is thickened, the patient may experience pain when he/she tries to raise the arm. In patients with subacromial impingement due to a thickened subacromial bursa, the physician can precisely inject the medication into the bursa using ultrasound guidance. Use of ultrasound guidance has been proven to yield a better effect of pain relief than the technique using guidance. A previous study found that even using ultrasound guidance to deliver medication, there were still many patients suffering from initial treatment failure or recurrence after the first successful injection. Because the pathophysiological mechanism of subacromial impingement is complexed, the proximal biceps tendon may be involved but is often ignored. Recently, the investigators published a randomized controlled trial comparing the effect of dual-target injection (proximal biceps tendon and subacromial bursa) with the standard subacromial injection in patients with subacromial impingement syndrome, and found that the dual target approach was safe and had a longer effective duration than the standard subacromial injection. In this regard, the investigators will conduct a longitudinal follow-up study to examine the long-term effectiveness of the dual-target corticosteroid injection for subacromial impingement syndrome.

Introduction:

Subacromial injection is considered one of the best treatments for patients with subacromial impingement syndrome. The subacromial bursa is located between the deltoid muscle and the supraspinatus tendon. It facilitates the gliding of the humeral head through the undersurface of the acromion. If the bursa is thickened, the patient may experience pain when he/she tries to raise the arm. In patients with subacromial impingement due to a thickened subacromial bursa, the physician can precisely inject the medication into the bursa using ultrasound guidance. Use of ultrasound guidance has been proven to yield a better effect of pain relief than the technique using guidance. A previous study found that even using ultrasound guidance to deliver medication, there were still many patients suffering from initial treatment failure or recurrence after the first successful injection. Because the pathophysiological mechanism of subacromial impingement is complexed, the proximal biceps tendon may be involved but is often ignored. Recently, the investigators published a randomized controlled trial comparing the effect of dual-target injection (proximal biceps tendon and subacromial bursa) with the standard subacromial injection in patients with subacromial impingement syndrome, and found that the dual target approach was safe and had a longer effective duration than the standard subacromial injection. In this regard, the investigators will conduct a longitudinal follow-up study to examine the long-term effectiveness of the dual-target corticosteroid injection for subacromial impingement syndrome.

Material and methods:

Participants: adult patients (>20 year old) with shoulder impingement syndrome Inclusion criteria: shoulder pain>3 weeks; no contraindication for local injection; Visual analogue scale of pain>4 The healthy volunteers are defined as no shoulder pain, and are only for the assessment of the inter-rater and intra-rater reliability of the ultrasound evaluation, without intervention

Participant number: 210 (150 with subacromial impingement, and 60 of healthy subjects) Exclusion criteria: systemic rheumatologic disease, Ankylosing spondylitis, malignancy, major trauma or recent injections on the affected shoulder

Study design:

The aims of this study is (1) set up the inter-rater and intra-rater reliability of the ultrasound evaluation in patients with subacromial impingement and healthy subjects (2) longitudinal follow up the therapeutic effect of dual-target injection to subacromial bursa and biceps tendon sheath only in patients with subacromial impingement

Detail of the intervention Single arm experiment: ultrasound guided injection into the subacromial bursa and biceps tendon sheath in patients with subacromial impingements, with 40 mg triamcinolone acetonide plus 3 mL of lidocaine

Outcome measurement:

physical examination(bicipital groove compression test, Speed's test, Yergason's test, empty can test, Neer's impingement test, Hawkins-Kennedy impingement test, painful arc test), range of motion as the baseline information. Visual analogue scale of pain, shoulder pain and disability index (SPADI), shoulder sonography (gray-scale/elastography)

Statistical analysis:

Continuous variables

1. Student's t test: fit assumption of normal distribution
2. Mann-Whitney test: does not fit the assumption of normal distribution

Categorical variables

(1) Chi-square test (2) Fisher exact test: sparse data

Multivariate analysis:

1. Linear regression
2. Logistic regression

Keywords: ultrasonography, corticosteroid, subacromial impingement syndrome, shoulder pain, longitudinal follow-up

Inclusion Criteria:

• shoulder pain>3 weeks; no contraindication for local injection; Visual analogue scale of pain>4

Exclusion Criteria:

• systemic rheumatologic disease, Ankylosing spondylitis, malignancy, major trauma or recent injections on the affected shoulder

The healthy volunteers are defined as no shoulder pain, and are only for the assessment of the inter-rater and intra-rater reliability of the ultrasound evaluation, without intervention.