Although ultrasound has been around for many years, the technology is underutilized. It has been used primarily by the radiologists and obstetricians-gynecologists. However, orthopedic surgeons and sports medicine doctors are beginning to realize the utility of this imaging modality for their specialties. Ultrasound has classically been used as a diagnostic tool. This usage is beneficial to sports medicine specialists for on-field coverage at sports competitions to efficiently evaluate injuries without the need for taking the athletes back to the locker room for an x-ray or magnetic resonance imaging (MRI). Ultrasound can quickly assess for damage to soft tissue, joints, and superficial bones. Another of ultrasound’s benefits is its use as an adjunct to treatment. Ultrasound has been shown to vastly increase the accuracy of injections and can be used in surgery to accurately guide percutaneous techniques or to identify structures that previously required radiation-exposing fluoroscopy or large incisions to find by feel or eye.
Ultrasound is a technician-dependent modality. The surgeon and physician must become facile with the use of the probe and how ultrasound works. The use of the probe is similar to an arthroscope, requiring small movements of the hand to reveal the best imaging of the tissues. Rather than relying on just the patient’s position with an immobile machine, the user must use the probe position and the placement of the patient’s limb or body to optimize the use of ultrasound. Doing so saves time, money, and exposure to dangerous radiation. In a retrospective study of 1012 patients treated over a 10-month period, Sivan and colleagues1 concluded that the use of clinic-based musculoskeletal (MSK) ultrasound enables a one-stop approach, reduces repeat hospital appointments, and improves quality of care.With the increased use of ultrasound comes the need to accurately code and bill for the use of ultrasound. According to the College of Radiology, Medicare reimbursements for MSK ultrasound studies has increased by 316% from 2000-2009.2 Paradoxically, ultrasound has still been relatively underutilized when compared to the use of MSK MRI.
Diagnostic Ultrasound
Ultrasound is based off sound waves, emitted from a transducer, which are then bounced back off the underlying structures based on the density of that structure. The computer interprets the returning sound waves and produces an image reflecting the quality and strength of those returning waves. When the sound waves are bounced back strongly and quickly, like when hitting bone, we see an image that is intensely white (“hyperechoic”). When the sound waves encounter a substance that transmits those waves easily and do not return, like air or fluid, the image is dark (“hypoechoic”).
Ultrasound’s fundamental advantages start with every patient being able to have an ultrasound: no interference from metal, pacemakers, claustrophobia, or obesity. Contralateral comparisons, sono-palpation at the site of pathology, and real-time dynamic studies allow for a more comprehensive diagnostic evaluation. Doppler capabilities can further expand the usefulness of the evaluation and guide safer interventions. With the advent of high-resolution portable ultrasound machines, these studies can essentially be performed anywhere, and are typically done in a timely and cost-effective manner.
Ultrasound has many diagnostic uses for soft tissue, joint, and bone disorders. For soft tissues, ultrasound can image tears of muscles, tendons, and ligaments; show inflammation like tenosynovitis; demonstrate masses like hematomas, cysts, solid tumors, or calcific tendonitis; display nerve disorders like Morton’s neuroma; or confirm foreign bodies or infections.3-5 For joint disorders, ultrasound can show erosions on bones, loose bodies, pannus, inflammation, or effusions. For bone disorders, ultrasound can diagnose fractures and, sometimes, even stress fractures. Tomer and colleagues6 compared 51 patients with bone contusions and fractures; they determined that ultrasound was most reliable in the diagnosis of long bone diaphyseal fractures. The one disadvantage, especially when compared to MRI, is ultrasound’s inability to fully evaluate intra-articular or deep structures such as articular cartilage, the glenohumeral labrum, the biceps’ anchor, etc.
Magnetic Resonance Imaging
Ultrasound is similar to MRI as it images tissues and gives us ideas whether that tissue is normal, damaged, or diseased (Figures 1A, 1B). MRI is based on magnetics and large machines that cannot be moved. MRI yields planar images that can only be changed by changing the position of the limb or body in the MRI tube. This can create an issue with obese patients or with postoperative patients who cannot maintain the operated body part in one position for the length of the MRI scan. Ultrasound is better tolerated by patients without the need for claustrophobic large machines (Table 1). In 2004, Middleton and colleagues7 surveyed 118 patients who obtained an ultrasound and MRI of the shoulder for suspected rotator cuff pathology; ultrasound had higher satisfaction levels, and 93% of patients preferred ultrasound to MRI.