Shoulder Subacromial Injection Technique

Updated: Feb 16, 2021
  • Author: Brett J Rothaermel, MD, PT; Chief Editor: Erik D Schraga, MD  more...
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Technique

Injection Into Subacromial Space

Opinions differ as to whether a single-needle or a two-needle injection technique is preferable. The single-needle technique is less painful. The two-needle technique prevents the possibility of flocculation of steroid crystals in the local anesthetic after mixing. Proponents of the two-needle technique also suggest that injection of the local anesthetic first numbs the area, making the subsequent injection more tolerable. The single-needle technique is described below.

Single-needle technique

Seat the patient upright in a comfortable position, with the arm hanging unsupported by his or her side. Palpate and mark the distal posterolateral edge of the acromion. Prepare and drape the site in a sterile manner with povidone-iodine, chlorhexidine gluconate, or isopropyl alcohol. Wear sterile gloves during the procedure.

Insert the needle inferior to the posterolateral edge of the acromion, directing it medially and slightly anteriorly; this places the needle tip beneath the acromion. Always aspirate before injecting to confirm that the needle tip is not placed intravascularly.

Next, inject the 6-7 mL corticosteroid–local anesthetic preparation. The injectate should flow freely without any significant resistance. (See the video below.) Never inject if significant resistance is encountered. Reposition the needle, and reattempt insertion until minimal resistance is encountered. If the patient has a contraindication for the use of a corticosteroid, then a diagnostic block may be performed with only local anesthetic. 

In 77-year-old woman with long history of chronic right shoulder impingement, posterior approach for subacromial injection is performed. Video courtesy of James R Verheyden, MD.

After the injection, patients with impingement syndrome experience temporary relief of symptoms and increased range of motion and strength. In the setting of a rotator cuff tear, corticosteroid injections should be used judiciously. Such injections may decrease inflammation and provide short-term pain relief, but they also weaken the involved tendon. [3] If no improvement is observed after injection, further imaging is indicated.

In a systematic review and meta-analysis by Aly et al, ultrasound (US)-guided subacromial injection was found to be as accurate as landmark-guided injection and to have superior efficacy (ie, significant reduction in pain and improvement in function). [15]

Dress the injection site with a sterile adhesive bandage. Encourage the patient to ice the area immediately after the injection and to avoid strenuous activity with the involved shoulder for the remainder of the day.

Treatment of impingement or rotator cuff syndrome generally includes physical therapy. [4]  However, a 2016 Cochrane review did not find high-quality evidence indicating that manual therapy and exercise yielded significant improvements on patient-important outcomes for patients with rotator cuff disease. [16]

Ultrasound-guided injection: lateral approach

The lateral approach is the most common approach to US-guided injection into the subacromial-subdeltoid bursa. The following is a description of the technique preferred by Molini et al. [17] Their approach is to have the patient seated on the examination table with the back turned to the physician so as to keep the needle outside of the patient’s field of view. They prefer a 5-cm (2-in.) 23-gauge needle. 

Applying sterile gel, position the probe parallel to the long axis of the supraspinatus. Apply disinfectant to the area to be punctured, and puncture the skin about 2-3 cm from the probe so as to avoid contaminating the needle with the probe. When the needle has penetrated the subcutaneous tissues, it will be visible as a hyperechoic structure with posterior comet-tail artifact when the beam is perpendicular to the long axis. (See the image below.)

Ultrasonogram shows needle penetrating bursa (righ Ultrasonogram shows needle penetrating bursa (right side of image) prior to injection of medication. Courtesy of Nicholas Goyeneche, MD, Ochsner Health System.

The long-axis scan permits real-time visualization of the needle entering the subacromial bursa. Once the needle has entered the bursa, inject a small amount of fluid, and visualize a real-time spread of hyperechoic echoes in the bursa to confirm correct positioning. With correct positioning confirmed, inject the rest of the corticosteroid, and then remove the needle.

Molini et al request that the patient avoid loading the shoulder for 2-3 days after the injection. [17] They also inform the patient of the possibility of renewed pain in the hours following the injection secondary to localized trauma.

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Complications

Complications are uncommon and often insignificant but include the following:

  • Iatrogenic infection - The risk of inducing joint infection is low when sterile technique is used
  • Injection of corticosteroids directly into a tendon or tendon insertion can sometimes result in tendon rupture
  • Corticosteroids may cause a transient rise in blood glucose levels in patients with diabetes mellitus
  • Subcutaneous corticosteroid injection may also cause skin hypopigmentation and fat atrophy
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