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General Medical Conditions

Point-of-Care Ultrasound, the New Musculoskeletal Physical Examination

Jackson, Sarah S. MD, RMSK, CSCS1,2,3; Le, Hung M. MD1; Kerkhof, Deanna L. MPH4; Corrado, Gianmichel D. MD1,2,3,4

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Current Sports Medicine Reports: February 2021 - Volume 20 - Issue 2 - p 109-112
doi: 10.1249/JSR.0000000000000810
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Abstract

Introduction

Point-of-care ultrasound (POCUS) is emerging into an indispensable diagnostic tool for physicians. The availability of handheld ultrasound (US) offers physicians an opportunity to better define anatomy and pathophysiology, thus enhancing the diagnostic capabilities of a standard physical examination (PE) (1).

The first US instrument was introduced in the early 1950s. The cost and inconvenience of the device made it impractical for frontline providers to use as a diagnostic or procedural aid at the bedside. It was not until the mid-1990s, after the advancement of real-time imaging, that the technology became available to clinics and hospitals. In recent years, reductions in the cost and size of the device have made US a more realistic option for bedside imaging.

A modality once used solely in radiology now spans across medical specialties. POCUS has been used to diagnose numerous adult and pediatric gastrointestinal, obstetric, vascular, cardiac, pulmonary, and musculoskeletal pathologic conditions that present to frontline providers.

The medical community increasingly embraces the potential for POCUS across medical specialties but reports have been limited to use by sports medicine physicians, emergency medicine, military medicine, and remote care. The current review highlights and expands on the utility of musculoskeletal (MSK) POCUS and its potential to compliment the PE. In 2012, Yim and Corrado (2) published an extensive review article describing POCUS as it related to the sports medicine physician. Buerger and Clark (3) assessed broad trends in POCUS in a 35-article review, finding POCUS utility in emergency medicine, military medicine, and remote care. The current review expands the scope of previous reviews by focusing attention on MSK POCUS applications with the potential to augment the PE.

This information will enable health care providers to facilitate its appropriate adoption into use in broader clinical practice settings.

Methods

A PubMed search was performed, with attention to conditions identifiable during a PE. PubMed was searched using combinations of the following search terms: musculoskeletal, point-of-care systems, ultrasonography, tendon, ligament, joint, effusion, fracture, dislocation, and joint injection, which produced a total of 123 articles. The results were further limited to human subject clinical trials, meta-analyses, randomized controlled trials, case reports, comparative studies, controlled clinical trials, and multicenter studies. The studies matching these inclusionary criteria were then screened with the following exclusionary criteria: not written in or translated into English, involved animal studies, did not use US in diagnostic intervention, or were duplicated studies. The references acquired from the initial search were categorized depending on how US studies were obtained, whether by trained technicians or directly by clinicians. The references of relevant articles were reviewed for additional resources. Of the 123 articles and selected references, 40 articles were related to POC and MSK US and are reviewed below.

Results

Medical history and PE are often effective in detecting common MSK conditions including joint dislocations, injuries to muscles, tendons, and ligaments, bony fractures, and joint effusions. Patients may present with nonspecific symptoms of pain, swelling, bruising, limb/joint deformity or malalignment, or range of motion restrictions. Many of these symptoms are present with all of the aforementioned conditions limiting their predictive value. POCUS is gaining popularity as a diagnostic and therapeutic aid in the field of musculoskeletal medicine given its ease, affordability, and safety. POCUS findings can augment the PE and often expedite diagnosis and treatment. Recent literature suggests POCUS is a reliable tool particularly for joint dislocations, muscle, tendon, and ligaments injuries, bony fractures, joint effusions, and joint pain (Table).

Table - Musculoskeletal US examination findings.
Organ System Diagnosis/Injury US Findings
Musculoskeletal Shoulder dislocation Posterior view: humeral head displacement in relation to the glenoid fossa
Lateral view: increased distance between acromion process and humeral head
Anterior view: increased distance between coracoid process and humeral head
Lateral view: useful for proximal humeral fracture prior to use of external rotation during reduction
Tendon injury (rupture/laceration) Disruption of normal fibrillous appearance of tendon
Hypoechoic hematoma with hyperechoic debride between tendon ends
Dynamic passive flexion/extension of a joint showing movement of the ruptured tendon ends — especially in the acute setting
Long bone fracture Step off sign of hyperechoic cortical surface
Hematoma and soft tissue edema surround fracture site
Elevated fat pad
Ligament injury Hypoechoic fluid representing edema in the acute setting
Fibrillar disruption
Joint effusions (hip) Asymmetric increase in hypoechoic fluid within joint capsule
Joint pain Tophi
Double contouring
Erosions
Hyperechoic/hypertrophic synovial tissue
Hypoechoic fluid within joint capsule

Typical PE findings of shoulder dislocations can include visible deformity of the affected shoulder or positioning of the arm specific to the direction of dislocation. Other PE findings can include decreased range of motion and neurovascular dysfunction (4). POCUS may reduce the number of radiographs needed for the diagnosis and management of shoulder dislocations by eliminating multiple films between reduction attempts. However, most studies agree that eliminating prereduction and postreduction films may increase risk of occult fractures (5–7). The use of US during the reduction of a dislocation may eliminate the need for readministration of sedation and may reduce emergency department (ED) admission times (5–8). Two case reports also described the successful use of US in diagnosing posterior dislocations, which can have subtle radiographic findings, and in guiding intraarticular lidocaine injection to facilitate reduction (9,10). Additionally, a recent pilot study showed novice ultrasonographers (i.e., nonmedical trainees) with brief training could diagnose an anterior shoulder dislocation with a single posterior view of the shoulder (11). Overall, POCUS has been shown to be a useful addition to the PE and can sometimes diagnose what could have been a missed posterior dislocation (7,9–11).

POCUS also has been shown to be useful in expediting care in tendon injuries, such as Achilles, patellar or quadriceps ruptures, and acute lacerations of tendons. Achilles, patellar, and quadriceps are relatively superficial tendons. They can be examined using US to assess for disruption of the normal fibrillar pattern, as well as to assess the tendon under dynamic testing (12). PE can be limited for tendon ruptures and partial tears due to pain, soft tissue swelling, or in the case of partial tear, preservation of active range of motion (13,14). Studies also have shown that US is more accurate in evaluating the patellar tendon than MRI (15,16). Case reports suggest that both static and dynamic US can be readily used in cases of acute tendon rupture, particularly in the setting of limited PE (14). An ED study showed POCUS had greater sensitivity and specificity than PE findings in diagnosing tendon lacerations, reporting values of 95% and 97% for POCUS and 76% and 85% for PE, respectively (17). This study also showed that US was faster than traditional wound exploration or MRI (17).

PE findings for ankle sprains and ligamentous injuries also can be augmented by POCUS. In radiograph-negative lateral ankle injuries, significant damage to the lateral ankle ligaments can exist. However, especially in the acute setting, the PE can be limited due to pain and swelling. US has been found to be sensitive in diagnosing lateral ligamentous injuries and can differentiate partial and complete tears (18,19). When attempts were made to identify ligamentous injury using POCUS in an ED setting, POCUS had limited accuracy. Sensitivity was poor, but specificity was 86% (20). The authors concluded that POCUS could be used to “rule in” lateral ligament ankle injuries in children (20). POCUS performed better for recurrent sprains and chronic ankle instability, with POCUS precision being comparable to MRI for both ED physicians and MSK radiology fellows (21). Given the current data, POCUS may be helpful in aiding the initial PE, but still has limitations in predictive value.

The use of POCUS for the diagnosis of pediatric fractures is appealing as it limits radiation exposure and painful positioning. Diagnosing a pediatric fracture can cause distress and typically yields nonspecific findings including deformity, edema, ecchymosis, and decreased range of motion. Research has described the accuracy and ease of using US to diagnose long bone fractures; however, US accuracy is limited for bones with irregular shapes or ends (12). For example, research has demonstrated US is a sensitive tool for detecting distal forearm and elbow fractures, injuries often diagnosed with radiographs (22). US is particularly useful when radiograph accessibility or time is limited (22). POCUS also is useful in the setting of occult fractures to look for signs, such as elevated fat pad or associated hematoma (12,23). A negative US can eliminate the need for radiographs (24,25). Additionally, POCUS can be used during fracture reduction, realignment, and hematoma blocks (12,26–28).

The potential of US in diagnosing other osseous abnormalities, such as stress fractures, is promising. Case reports have described its utility in diagnosing lower extremity stress fractures in locations, such as the tibia and metatarsals (29,30). US findings, such as an increase in power/color Doppler signal, cortical thickening, periosteal elevation, surrounding hypoechoic hematoma, and callous formation, may be seen (30,31). Although X-rays are typically the initial diagnostic modality to assess for stress fractures, it has poor sensitivity (32). US may be an alternative option, but more studies are needed to demonstrate its efficacy in diagnosing stress fractures.

Recent literature also has described the ease and accessibility of POCUS to aid in the PE of the child with a painful hip. Taking a complete history for a child can be difficult, because he or she may be afraid and/or unable to describe his or her pain. Typical PE findings of a child with hip pathology include limp or refusal to bear weight, limited range of motion, and laying with the affected leg in abduction and external rotation (4). Research suggests that POCUS is an accurate tool to detect joint effusions (33–37). Detection can prompt a decision to aspirate a joint, which can be performed under US guidance. US guidance has been shown to enhance the feasibility of arthrocentesis of a hip effusion by emergency physicians, decrease need for procedural sedation, and decrease exposure to radiation as this was once performed under fluoroscopic guidance (38). Additionally, Adhikari and Blaivas (33) demonstrated POCUS of a swollen and painful joint can greatly alter patient treatment. POCUS prevented more than 50% of futile joint aspirations and detected joint effusion in approximately 50% of patients in whom aspiration was not planned by the treating provider. US of the hip also has been shown to be more sensitive than radiographs in the diagnosis of hip effusion. As a result, POCUS is the modality of choice for the initial evaluation of hip joint effusions (39,40). Similarly, POCUS can be used to accurately assess for knee and elbow effusions (41,42). POCUS of the hip cannot only be used to aid the PE in making a timely diagnosis, but also can be used to guide management of these patients (40).

Similar to the pediatric patient who presents with a limp, the adult patient presenting with joint pain also can be a diagnostic dilemma for which the PE is limited. The use of POCUS can aid the PE in making the diagnosis, guiding care management, and performing image guided arthrocentesis or joint injection used for both diagnostic and therapeutic purposes. Adhikari and Blaivas (33) showed POCUS can help differentiate joint effusions from soft tissue abnormalities and direct appropriate therapy in a cohort of 54 patients presenting to the ED. US has been used to differentiate between types of arthropathy, such as osteoarthritis, rheumatoid arthritis, gouty arthritis, or calcium pyrophosphate deposition. Findings, such as tophi, double contour, or erosions, help clinicians with this differentiation (43). Additional studies have demonstrated that US is comparable or better than synovial fluid analysis in the diagnosis of calcium pyrophosphate deposition (43,44).

Within this review, we have mostly focused on how POCUS can augment the PE, but POCUS also can be used to guide everyday procedures performed by frontline providers. Interventional applications of US ultimately help to guide treatment plans and improve the safety and efficacy of treatments administered to patients. MSK US-guided procedures include hematoma block in the setting of a fracture reduction/realignment, joint injection of anesthetic prior to reduction of shoulder dislocation, arthrocentesis of a hip effusion in a child, and corticosteroid injections in the setting of acute pain flare in arthritis (9,10,12,26–28). US guidance has been shown to decrease pain and improve accuracy of joint injections (45–49). The diagnostic and therapeutic utility of POCUS can certainly augment medical history and PE. The future utility of this technology in the hands of frontline providers is still unknown but appears promising.

Discussion

The availability of handheld US offers physicians an opportunity to better define anatomy and pathophysiology, thus enhancing the diagnostic capabilities of a standard PE. This article has highlighted the ability of MSK POCUS to be used in a range of pathologies including osseous abnormalities, tendon and ligament injuries, joint effusions, and joint dislocations.

US is now being incorporated in medical school, residency, fellowship, and postgraduate training, and is quickly becoming an important tool across medical settings. Skill and confidence with POCUS can be quickly acquired following a 1-d course (50,51). Physicians across the spectrum of medicine can incorporate US into their clinical practice, improving diagnostic sensitivity and specificity, reducing radiation exposure, lowering costs, and decreasing time to diagnosis without an increase in adverse events or missed diagnoses.

POCUS does not come without its limitations. The utility of US is user dependent and may come with a steep learning curve in differentiating normal from abnormal. In 2013, Arend (52) described the top 10 pitfalls when performing MSK sonography. The following are some examples. Strategies, such as contralateral comparison, can be used to detect subtle differences that may hint at underlying pathology, but reliance on investigating for asymmetry may lead to false positives as subclinical pathology is not uncommon. In addition, normal MSK anatomy may mimic pathology. For example, the subscapularis has a multipennate appearance in short axis but may be misinterpreted as being abnormal by inexperienced scanners. Lastly, anisotropy, in which echogenicity of various soft tissue structures varies depending on probe positioning, can lead to inaccurate interpretation. For example, the echogenicity of a tendon will vary depending on the angulation of the transducer. If the transducer is not directly perpendicular or parallel to the tendon fibers, it will appear hypoechoic and be perceived as abnormal.

Future research should closely examine the cost and accessibility of US across medical settings and specialties to quantify the cost implications of POCUS and describe existing roadblocks in POCUS access for physicians eager to implement POCUS into their practice. Understanding the barriers to its broad use is the first step in expanding POCUS. We have already begun the systematic reviews of POCUS in additional organ systems to explore ways to enhance other aspects of the PE and are excited to share these findings in the near future.

The authors declare no conflict of interest and do not have any financial disclosures.

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