Ultrasound For Soft Tissue And Musculoskeletal Applications
Ultrasound For Soft Tissue And Musculoskeletal Applications
Point-of-care ultrasound can be used for a wide variety of soft tissue and musculoskeletal applications in the ED, including the diagnosis of soft tissue infections and masses, tendon injuries, joint effusions, and fractures, as well as the localization of foreign bodies. Ultrasound offers the emergency clinician rapid bedside evaluation of and procedural guidance for a wide array of these commonly encountered conditions.
Cellulitis And Abscesses
An increasing body of literature has demonstrated the utility of BUS in the management of soft tissue infections in the ED by aiding in the differentiation between cellulitis and abscess, as well as localizing and guiding drainage of fluid collections.79-81 (See Figures 10 and 11.) Ultrasound has been shown to be superior to the physical examination and to alter the management of patients with soft-tissue infections.
How often have you wondered if a skin infection actually has a drainable fluid collection? A prospective study by Squire et al evaluated 107 patients with suspected cellulitis or abscess and compared the accuracy of physical examination with that of ultrasound in detecting subcutaneous abscesses.79 Prior to obtaining the ultrasound, the treating clinician reported a “yes” or “no” assessment on the presence of an abscess. Ultrasonography was performed by physicians and residents who had attended a 30-minute training session on this application. The gold standard was purulent drainage on incision or resolution of symptoms on antibiotics alone at follow-up on day 7. The authors found ultrasound to be more accurate when compared with the clinical examination in terms of sensitivity (98% vs 86%), specificity (88% vs 70%), positive predictive value (93% vs 81%), and negative predictive value (97% vs 77%).
The findings on bedside soft tissue ultrasound can dramatically alter how the patient is managed. Tayal et al enrolled 126 patients with soft tissue infections and asked the clinicians about their treatment plan.80 Ultrasonography was then performed by 1 of the study physicians who had significant experience in the use of emergency ultrasound. Overall, the ultrasound findings resulted in a change in management in 71 of the 126 patients (56%). The changes included new plans for drainage (all of which returned purulent material), sparing a planned drainage, and further testing or consultation. Interestingly, although not the purpose of the study, 4 other diagnoses were made using BUS, including enlarged lymph nodes, DVT, and superficial phlebitis.
In addition to its value in assessing cutaneous infections, ultrasound has been found useful in the diagnosis and management of suspected peritonsillar abscesses (PTA).82-84 In this situation, a high-frequency intracavitary probe is used to visualize the posterior pharyngeal space. In a descriptive study, Lyon and Blaivas retrospectively reviewed 43 cases of patients with clinically suspected PTA who underwent BUS in their ED.84 Thirty-five (81%) were diagnosed with PTA and 8 (19%) with tonsillar cellulitis. All patients diagnosed with PTA underwent ultrasound-guided drainage in the ED with no complications or need for return visits, although no formal follow-up was carried out.
Foreign Bodies, Joint Effusions, And Fractures
Bedside ultrasound is also useful for other common soft tissue and musculoskeletal diagnosis in the ED. Ultrasound can be used to screen for superficial foreign bodies, although it has significant limitations. A variety of studies have sought to determine the accuracy of ultrasound for foreign body localization, often in cadaveric or simulated models, with varied results.85-91 One study demonstrated a sensitivity of 93% for detecting radiolucent wooden objects and of 73% for detecting radiolucent plastic objects in human cadaver legs.88 In another study, minimally trained emergency physicians used ultrasound to detect small foreign bodies (less than 5 mm).89 Ultrasound was found to have an overall sensitivity of 53% and a specificity of 47%, with a positive predictive value of 80%. It is likely that the sensitivity and specificity achieved in localizing a foreign body depends on numerous factors, including the experience of the sonographer, the frequency and quality of the transducer, the type of tissue model used, as well as the composition, size, and depth of the foreign body.
Ultrasound can be used to both diagnose joint effusions and to assist in arthrocentesis. In a randomized trial comparing ultrasound-guided versus landmarkbased knee arthrocentesis, the findings on ultrasound did not change the success rate of the procedure but did lead to more fluid aspirated and to greater provider confidence.92 Case series have been reported that describe the diagnosis and drainage of ankle effusions and of both adult and pediatric hip effusions by emergency physicians using ultrasound in the ED.93-95
Although the current standard of care for the evaluation of bony fractures is radiography (as well as CT and MRI), ultrasound may potentially be useful in a number of scenarios. In certain environments where plain x-rays are not available (such as military battlefields, in space, or remote or international locations), ultrasound may potentially be utilized for diagnosing fractures with acceptable accuracy. In a study of 58 patients with suspected long-bone fractures, ultrasound had a sensitivity of 92% and specificity of 83% compared with x-ray and was more sensitive than physical examination for the diagnosis of fractures.96 In another study designed to evaluate extremity injury in austere settings, nonphysician personnel, using ultrasound, correctly diagnosed extremity injuries in 94% of patients.97
Ultrasound may be superior to plain x-ray for select fractures that are traditionally difficult to evaluate by radiography. In a study of 88 patients with chest trauma, ultrasound was found to be superior to clinical acumen and radiography for detecting rib and sternal fractures.98 In certain clinical situations, ultrasound may be useful in expediting and assisting management, such as during bedside reduction requiring sedation. In 1 study of 68 pediatric patients with suspected forearm fractures, ultrasound had a sensitivity of 97% and a specificity of 100% for detecting fractures when compared with plain films.99 Ultrasound-guided reduction of those fractures had an initial success rate of 92%, with only 2 of 26 patients requiring re-reduction based on x-ray findings.
Bedside ultrasound has been shown to be of value in a wide range of soft tissue and musculoskeletal applications. Ongoing research and increasing utilization at the bedside will provide greater understanding of the benefits and limitations of each of the various applications.
James Q. Hwang; Heidi Harbison Kimberly; Andrew S. Liteplo; Dana Sajed
March 2, 2011