The use of ultrasound to evaluate musculoskeletal structures was first reported in 1958. Since then, its use has grown exponentially, particularly in the office setting. Ultrasound enables physicians to reliably visualize soft-tissue structures including muscle bellies, tendons, ligaments, arteries, and nerves, as well as identify any pathologic changes within these structures.

The use of ultrasound has several advantages, including the relatively lower cost compared to other imaging methods and the absence of ionizing radiation. It is a repeatable, noninvasive imaging modality that is capable of providing real-time dynamic tissue assessment. In addition, ultrasound can be used to quickly compare the affected and contralateral sides when necessary.

Ultrasound has also been used as an imaging guide for intra-articular or soft-tissue injections to help improve accuracy. Using ultrasound guidance, a physician can directly visualize an injection needle’s path and the immediate structures around it, thereby minimizing risk of injury to adjacent nerves or blood vessels.

This review discusses the clinical accuracy of ultrasound-guided injections and techniques in current literature in the following five areas of the shoulder and elbow:

• the acromioclavicular (AC) joint
• the long head of the biceps tendon
• the glenohumeral joint
• the ulnar collateral ligament (UCL)
• the lateral epicondyle (tennis elbow)

Administering injections
Corticosteroid injections can be administered using either palpation of bony landmarks or imaging as a guide. Differences in injection technique may contribute to the variability in reported clinical outcomes; current studies quote variable accuracy rates of blind (landmark-guided) and imaging-guided injections.

Injection accuracy depends on many variables, including the site of injection, the approach taken to deliver the injection, and the physician’s technical skill. When considering glenohumeral injections for example, one clinical study reported accurate injection location in 10 of 24 attempts (42 percent), while a separate study reported successful injection in only 2 of 20 attempts (10 percent).

The approach (anterior or posterior) can affect the accuracy of glenohumeral injections in particular. A cadaveric study assessing the difference in these two approaches reported 80 percent accuracy anteriorly and 50 percent accuracy posteriorly.

Image guidance during injection has shown favorable accuracy rates compared to blind injection. Cadaveric studies in which the exact injection site was confirmed by dissection found that the landmark-based method was accurate 40 percent to 66 percent of the time, while fluoroscopic guidance yielded accuracy rates of 100 percent. Other cadaveric studies have reported similarly high accuracies (95 percent to 100 percent) when imaging guidance was used.

Outcome comparisons
Few randomized controlled trials compare image-guided and landmark-guided injections, and most of these studies pertain only to shoulder joint injections. Based on outcomes in two moderate-sized shoulder injection studies, researchers concluded that patients who had undergone ultrasound-guided injections demonstrated greater improvement in both pain and shoulder function at 6 weeks than those who received landmark-guided injections.

Another shoulder injection study found that the group receiving an ultrasound-guided subacromial injection showed significantly greater improvement than the group with a blind injection. Patients in the ultrasound group demonstrated a mean visual analog scale (VAS) score improvement of 34.9, compared to just 7.1 for the blind group (P < 0.001). Likewise, the change in mean shoulder function assessment score was also greater for the ultrasound group (15 v 5.6, P = 0.012). Based on these findings the researchers concluded that image-guided corticosteroid injections should be the method of choice, especially in patients who previously received a blind injection that failed.

Similar results were demonstrated in a separate study of 60 patients randomly assigned to receive either landmark-guided (n = 30) or ultrasound-guided (n = 30) triamcinolone injections for shoulder pain. The ultrasound group showed a vast improvement in VAS pain and Constant scores at 6 weeks compared with the landmark-guided group. The mean VAS pain score decrease was 4.0 ± 1.7 for the ultrasound group compared to 2.2 ± 0.9 for the landmark-guided group (P < 0.05); the mean Constant score change was 32.2 for the ultrasound group compared to 12.2 for the landmark-guided group (P < 0.05).

Despite the improved accuracy in using ultrasound to guide injections, it has been suggested that no significant long-term outcome difference exists between the two techniques. In a systematic review of 17 articles (272 shoulders), image-guidance provided superior accuracy and short-term improvements, but did not change the long-term efficacy of shoulder injections. These researchers concluded that, although steroid injections are useful in clinical settings for pain management, ultrasound guidance may not be needed. The varying results achieved to date may be the consequence of differently designed studies, indicating a need for further studies.

Ultrasound-guided techniques
There are two approaches to ultrasound injections: in-plane (IP) and out-of-plane (OOP). With the IP approach, the needle is lined up with and parallel to the ultrasound transducer, enabling the physician to see the length of the needle as it approaches the target site. With the OOP approach, the needle is placed perpendicular to the transducer and a transverse section of the needle is visualized at the target site.

AC joint—The patient is sitting with the affected arm in a neutral position. Due to the superficiality of the structures, a linear probe with high frequency is recommended. The AC joint is visualized by placing the probe superiorly over the joint in line with the anterior edge of the acromion and parallel to the clavicle. The center of the probe is lined up with the center of the joint, and the needle is introduced into the joint OOP after the injection site has been sterilized (Fig. 1, 2).

Long head of biceps tendon—The patient can be seated with back support. The linear ultrasound probe is placed over the bicipital groove with the affected arm in external rotation. The injection site is sterilized and the needle is inserted into the tendon sheath with an OOP approach (Fig. 3, 4). Care is taken to avoid the anterior humeral circumflex artery. Although steroid injection may relieve pain, it can also further weaken an already injured tendon and should be used cautiously.

Glenohumeral joint—The patient is seated with the affected arm in internal rotation. The linear probe is placed transversely over the joint parallel to the scapular spine. The injection site is sterilized and the needle is inserted from medial to lateral IP with the ultrasound probe. The needle is directed through the rotator cuff and between the free edge of the labrum and articular cartilage of the humeral head (Fig. 5, 6).

UCL—The patient is positioned supine with the shoulder in external rotation. The linear ultrasound probe is placed over the ligament between the medial epicondyle and the sublime tubercle. The needle is inserted IP with the probe after sterilization of the injection site (Fig. 7, 8), and platelet-rich plasma may be injected. Steroid injections are not recommended for UCL injuries due to potential weakening of the ligament.

Lateral epicondyle—The patient is seated with the elbow flexed. The linear probe is placed over the common extensor origin in line with the lateral epicondyle and the radiocapitellar joint. The needle is inserted IP with the probe after sterilization of the injection site (Fig. 9, 10).

Conclusion
Musculoskeletal ultrasound is a multipurpose imaging method that can be used by sports medicine physicians in the office setting. It is a safe, noninvasive, and low-cost alternative to other imaging modalities. Ultrasound has no radiation exposure and provides dynamic assessment of needle placement during injections. By visualizing nearby neurovascular structures, ultrasound-guided injections allow safe and precise delivery into the involved soft-tissue structure.

Limited data exist comparing the clinical efficacy of ultrasound-guided to palpation-guided injections, and the majority of those studies only address the shoulder joint. However, from those studies it was found that patients who received an ultrasound-guided injection demonstrated statistically significant greater improvement in pain and shoulder function at 6 weeks compared to those who received a blind injection. Although these early clinical outcomes appear promising, it is unclear whether image guidance will have an impact on long-term results.

Image-guided injections have the potential to minimize complications while simultaneously improving injection accuracy. Future well-designed, prospective, randomized outcome studies and evidence-based clinical research will help delineate the advantages of ultrasound-guided injections and diagnostic imaging in the management of various orthopaedic sports medicine problems.

For information on new codes for joint injections using ultrasound guidance, see “New Orthopaedic CPT Codes for 2015.”

One or more of the authors report potential conflicts of interest. Disclosure information is available at www.aaos.org/disclosure

Yashika Patel, MD; Anthony J. Scillia, MD, Anthony Festa, MD; and Vincent K. McInerney, MD, are in private practice at the New Jersey Orthopaedic Institute; Stuart Hirsch, MD, is a member of the AAOS Now editorial board and in private practice at BioSport Orthopaedics, Bridgewater, N.J.

Bottom Line

• Ultrasound can be used to guide appropriate placement of injections for a variety of conditions in the upper extremity.
• Ultrasound has no radiation exposure and is a safe, noninvasive, and low-cost alternative to other imaging modalities.
• Although some outcome studies have been performed, a well-designed, prospective, randomized outcome study and evidence-based clinical research are needed to delineate the advantages of ultrasound-guided injections.

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