A Guide to Ultrasound of the Shoulder, Part 3: Interventional and Procedural Uses

Ultrasound has classically been marketed and used as a diagnostic tool. Radiologists, emergency physicians, and sports physicians used ultrasound units to rapidly and appropriately diagnose numerous injuries and disorders, in a timely and cost effective manner. Part 1¹ and Part 2² of this series showed how to use ultrasound in the shoulder for diagnosis and how to code and get reimbursed for its use.Ultrasound can also be used to help guide procedures and interventions performed to treat patients. Currently, more physicians are beginning to recognize the utility of this modality as an aid to interventional procedures.

First-generation procedures use ultrasound to improve accuracy of joint, bursal, tendon, and muscular injections.³ Recent studies have shown a significant improvement in accuracy, outcomes, and patient satisfaction using ultrasound guidance for injections.^3-12 Within the limitation of using a needle, second-generation procedures—hydrodissection of peripherally entrapped nerves, capsular distention, mechanical disruption of neovascularization, and needle fenestration or barbotage in chronic tendinopathy—try to simulate surgical objectives while minimizing tissue burden and other complications of surgery.³ More advanced procedures include needle fenestration/release of the carpal ligament in carpal tunnel syndrome and A1 pulley needle release in the setting of trigger finger.³ Innovative third-generation procedures involve the use of surgical tools such as hook blades under ultrasound guidance to perform surgical procedures. Surgeons are now improving already established percutaneous, arthroscopic, and open surgical procedures with ultrasound assistance.³ Aside from better guidance, reducing cost and improving surgeon comfort may be additional benefits of ultrasound assisted surgery.

Image-Guided Treatment Options

Prior to image guidance, palpation of surface anatomy helped physicians determine the anatomic placement of injections, incisions, or portals. Joints and bursas that do not have any inflammation or fluid can sometimes be difficult to identify or locate by palpation alone. Palpation-guided joint injections often miss their target and cause significant pain when the therapeutic agent is injected into a muscle, tendon, ligament, fat, or other tissue. Ultrasound-guided injections have proven to be more accurate and have better patient satisfaction when compared to blind injections.^3-12

X-ray fluoroscopy has been the primary option for surgeons to assist in surgery. This is a natural modality for orthopedic surgeons; their primary use is for bone to help with fracture reduction and fixation as the bone, instrumentation, and fixation methods are usually radio-opaque. With the advancement in technology, many orthopedic surgeons are regularly using radiolucent fixation devices and working with soft tissue as opposed to bone. Fixation of tendons, ligaments, and muscles would be done using a large incision, palpation of the anatomy, then fixation or repair. Many surgeons began looking for ways to minimize the incisions. Turning to fluoroscopy, a traditional and well-used modality, was a natural progression. Guides and methods were developed to isolate insertions and drill placements. However, fluoroscopy is limited by its difficulty in changing planes and the large equipment required. Also, it is limited in its ability to image soft tissue.

Computed tomography (CT) scans and magnetic resonance imaging (MRI) are far better at imaging soft tissue but cannot be taken for use into the office or surgical suite. These modalities are also far more expensive and take up significant space.

Ultrasound Procedural Basics

Appropriate use of ultrasound still remains highly technician-dependent. Unlike other imaging modalities, ultrasound requires a higher skill level by the physician to implement the use of ultrasound and identification of pathology to treat these disease processes. However, this is no different from the use of arthroscopy or fluoroscopy to treat patients. Training is required, as well as an understanding of the ultrasound machine, anatomy, and sono-anatomy—identification of anatomy and pathology as shown by the ultrasound machine.²

In ultrasound, the long axis refers to looking at a structure along its length, as in longitudinal. The short axis refers to evaluating a structure in cross-section, transverse, or along its shortest length. “In plane” refers to performing a procedure where the needle or object being used enters the ultrasound field along the plane of the transducer, allowing visualization of the majority of the needle as it crosses tissue planes. “Out of plane” has the needle entering perpendicular to the plane of the transducer, showing the needle on the monitor as a bright, hyperechoic dot. Some studies have suggested that novice ultrasonographers should start in a long axis view and use the in plane technique when injecting, as doing so may decrease time to identify the target and improve mean imaging quality during needle advancement.¹³

Anisotropy is the property of being directionally dependent. The ultrasound beam needs to be perpendicular to the structure being imaged to give the optimal image. When the beam hits a longitudinal structure like a needle at an angle <90°, the linear structure might reflect most of the beam away from the transducer. So when using a needle to localize or inject a specific area, maintaining the probe as close to perpendicular as possible with the needle will give a better image. New technology exists to better visualize needles even at high acuity angles by using a multi-beam processing algorithm, which can significantly aid the physician without the need for specialized needles.

Despite better technology, advance planning is key to a successful procedure. Positioning the patient and ultrasound machine in a manner that is comfortable and makes the desired target accessible while being able to visualize the ultrasound monitor comes first. Identifying the target, mapping the needle trajectory using depth markings, and scanning for nerves, vessels, and other structures that may be damaged along the needle path comes next. Using the in plane ultrasound technique with color Doppler and the nerve contrast setting can ensure that the physician has placed the therapeutic agent to the proper location while avoiding any nerves, arteries, or veins. Marking the borders of the ultrasound probe and needle entry site can be helpful to return to the same area after sterile preparation is done. As in any procedure, sterile technique is paramount. Sterile technique considerations may include using sterile gloves and a probe cover with sterile gel, cleaning the area thoroughly, planning the needle entry point 3 cm to 5 cm away from the probe, and maintaining a dry and gel-free needle entry.^14-15 The probe should be sterilized between patients to avoid cross-contamination; note that certain solutions like alcohol or ethyl chloride can damage the transducer.^14-15 However, simple injections do not require such stringent standards when simple sterile technique is observed by cleaning and then never touching the cleaned area again except with the needle to avoid contamination. Also, ethyl chloride has been found to not contaminate a sterile site and can be used safely to anesthetize the skin.