Ultrasonography has advantages over other imaging modalities in terms of availability and comfort, safety, and diagnostic potential. Operating costs are low compared with both computed tomography (CT) and magnetic resonance imaging (MRI). The portable equipment is accessible at locations distant from medical centers. Importantly, ultrasonography is performed while patients lie in a comfortable position, without pain or claustrophobia.
Ultrasonography is a totally safe noninvasive imaging technique. In contrast to computed tomography (CT) and X-rays, it does not emit ionizing radiation. Unlike magnetic resonance imaging (MRI), it is safe for all patients, including those with cardiac pacemakers and metal implants, without any contraindications.
With its outstanding diagnostic benefits, notably high resolution and capability of real time assessment[1,2], orthopedic ultrasound is often referred to as the “orthopedic surgeon’s stethoscope”. Its high resolution enables detection of tendon tears, tiny calcifications, and foreign bodies. Calcification in soft tissue and destructive and reparative hypertrophic changes on bone surfaces are more readily apparent, and at an earlier stage, than with plain X-rays, CT or MRI. Ultrasonography thus enhances early detection of pathologies.
The real time capability of musculoskeletal sonography enables dynamic assessment of joint and tendon movements and stability, and detection of fracture union and reunion, structural abnormalities, infection, ligamentous injury, nerve compression and mechanical impingement between orthopedic hardware and soft tissue structures. Beyond diagnostics, real time capability is useful for guiding therapeutic interventions, such as cyst aspiration. The fact that ultrasound examinations may be easily repeated as often as necessary, makes this modality useful for monitoring treatment.
Due to its flexibility and precision in the selection of the point of examination and in the field of vision, musculoskeletal ultrasonography has spatial, as well as temporal benefits. The possibility of placing the sonographic probe at the point of maximal tenderness increases the likelihood of detecting abnormalities, and ensures clinical relevance of the examination. Sonography affords comparisons of targeted findings with those of the contralateral side, and also enables under “vision” biopsy or joint aspiration.
Of the many indications for musculoskeletal ultrasonography, the evaluation of soft tissue pathology is particularly common. In addition, ultrasonography is useful for the detection of fluid collection, and for visualization of cartilage and bone surfaces. Color or power Doppler provides important physiological information, including that relating to the vascular system. The capability of ultrasonography in delineating structures according to their echo textures results in excellent pictorial representation. This imaging principle is based on physical changes in composition, as compared to imaging with MRI, which is based on changes in chemical composition.
This article reviews the contribution of sonography to the evaluation of the musculoskeletal system.
Ultrasonography is preferable to radiography for the early detection of calcification in soft tissue in the neck region. In the investigation of suspected soft tissue tumors, such as in acute swelling of sterno-cleido mastoideus, and in cases of congenital muscular torticollis, ultrasound can often distinguish between a true tumor mass and a hematoma or muscle rupture.
The appearance of an echogenic structure with acoustic shadowing in the region of tenderness may indicate a cervical rib (Figures (Figures11 and and2).2). Fracture of the clavicle in the newborn and congenital pseudoarthrosis of the clavicle can also be diagnosed with ultrasound.
At our medical center, the shoulder is one of the bodily areas for which musculoskeletal sonography is most requested. Age-related degenerative changes and overuse syndrome with degenerative tears leads many patients to seek medical treatment for painful shoulder.
Suspicion of rotator cuff pathology is the most important indication for shoulder sonography. Musculoskeletal ultrasound enables early detection of changes in tendons, in bursae-rotator cuff and in cartilage, thus leading to adequate treatment. Tears can be seen, located, and measured[11–13] (Figures (Figures3,3, ,44 and and5).5). Their full anatomical extent can be assessed. Calcification is more visible with ultrasound than with MRI (Figure (Figure6)6) and the capability of precise location enables assessment of treatment. Sonographic palpation and comparison with the other shoulder is easily performed.
The presence of fluid around the biceps tendon or subdeltoid bursa may indicate a bursitis infection or tear (Figure (Figure7).7). Lesions associated with rotator cuff disease, such as long biceps tenosynovitis and sub-acromial deltoid bursitis, can be visualized by ultrasound.
Ultrasound can detect fractures in the head and shaft of the humerus, especially the greater tuberosity (Figure (Figure8).8). Greater tuberosity fractures are characterized by sonography as cortical discontinuity, and may appear as a cortical gap or step-off (double line). They should be included in the differential diagnosis of every shoulder sonography examination, even in the absence of a clear history of trauma. Osteolytic lesions of the proximal humerus can also be detected in ultrasound (Figure (Figure99).
Since conventional radiography does not adequately diagnose symptoms of shoulder pain, a sonographic examination is recommended as part of the early diagnostic protocol[15,16]. Ultrasound is useful in detecting pathologies in the acromioclavicular joint, such as acromioclavicular joint arthritis and dislocation (Figure (Figure1010), as well as septic arthritis of the sternoclavicular and acromioclavicular joints.
The effectiveness of sonography has been demonstrated for the evaluation and diagnosis of Hill-Sachs lesions, which frequently follow anterior gleno-humeral dislocation of the shoulder. Moreover, ultrasound can be used to assess sonographic images in hemiplegic shoulders of stroke patients.
Dynamic sonography enables direct visualization of the relationships between the acromion, humeral head, and intervening soft tissues during active shoulder motion, and can provide information on the potential intrinsic and extrinsic causes of shoulder impingement syndrome. In cases of frozen shoulder, abnormal gliding and rotational movement are apparent, with the entire soft tissue moving as a single unit (deltoid, rotator cuff. and humeral head). The capability of ultrasound in detecting a full thickness tear is impressive. Drakeford et al reported sensitivity of 92% and specificity of 95%. Ultrasound can also be used to detect tears of pectoral muscle (Figure (Figure1111).
Ultrasound is useful for examining proximal muscles acting on the shoulder and elbow. Muscle compartments are divided into flexor and extensor groups. Ultrasound can detect common tendon injuries, such as “tennis” and “golfer” elbow, in which swelling, thickening, and accumulation of fluid is apparent[24,25]. Musculoskeletal ultrasound is an effective imaging technique for the diagnosis of olecranon bursitis, especially its early manifestation. Sensitive detection of small fluid collection is possible (Figure (Figure12),12), as well as differentiation between soft tissue and bone lesion, and between septic and non septic elbow. Ultrasound examination allows detection of effusions, synovial proliferation, calcification, loose bodies, rheumatoid nodules, gout tophi, and septic processes (Figure (Figure1313)[26,27], as well as distal biceps tendon lesions (Figure (Figure1414).
Ultrasound examination of the flexor and extensor tendons and ligaments of the finger may reveal such pathologies as tendinopathy, tenosynovitis, ruptures, and neoplasia (Figure (Figure1515 ). Cystic or solid swelling palpable tumors and occult ganglion can be observed[28–30]. Foreign bodies often remain undetected in penetrating wounds and lacerations, pathologies frequently treated in the emergency room. Sonography is useful in the localization and removal of soft tissue foreign bodies[31,32], and in the detection of greenstick fractures of the distal radius and ulna.
The sonographic examination of a patient with suspected traumatic Mallet finger is important for the differentiation between traumatic Mallet finger and flexion deformity due to rheumatoid arthritis or osteoarthritis.
Ultrasound can be helpful in differentiating synovial and teno-synovial pathology, and in examining pathological and morphostructural changes of the median nerve in carpal tunnel syndrome.
While, clinical examination of the knee joint is relatively easy, very small effusions and synovitic proliferations may be missed. Ultrasound can detect these, as well as fluid in the knee and in the area of the tendons (Figure (Figure16).16). Further, ultrasound is useful for assessing ligaments, and for diagnosing pathologies relating to anterior knee pain[35–37].
Dynamic sonographic examination, with stress tests (Figure (Figure17),17), can demonstrate instability and meniscal pathology (Figure (Figure1818). Synovial cysts, medial collateral ligaments, lateral collateral ligaments and tears of tendon can be assessed. Ultrasound is also used in diagnosis of patellar and quadriceps tears (Figure (Figure1919 ).
In medial collateral ligament (MCL) injury, the combination of sonographic findings with those from a real time sonography valgus stress test can support the clinical diagnosis of an MCL stretch or tear, and pinpoint the exact location of the isolated MCL injury, thus facilitating proper treatment.
Ultrasound can suggest an early diagnosis of osteoarthritis (Figure (Figure21)21) by demonstrating joint effusion, synovial thickening, bony changes, patello femoral changes, articular cartilage changes, peripheral tears and lesions of the tendon, and meniscal pathologies, such as meniscal cysts, and Baker cyst. Pathologies can be detected by ultrasound at a stage in which plain radiographs still appear normal. Muscle and ligament pathology (Figures (Figures22,22, ,2323 and and24),24), and tumors of the tibial tuberosity can be diagnosed, as well as fractures of the patella (Figure (Figure2525).
Ultrasound can provide a dynamic assessment of muscle tear, or of an intermittent muscle hernia or tendon subluxation. As with other soft tissue lesions, ultrasonography is useful for the evaluation of underlying pathologies in patients presenting with achillodynia and ankle pain. The Achilles tendon is the tendon most commonly evaluated in the leg and may be associated with a wide range of pathologies, including tendonosis, tears, calcification, and inflammations (Figure (Figure2626)[45,46]. Haglund deformity may be related to Achilles tendon pathology. The dynamic nature of the ultrasound examination enables tendon movement and visualization from the origin to the insertion of a tendon, as is needed in the evaluation of the Achilles tendon. Diseases of the Achilles tendon include a broad spectrum of pathologies ranging from paratendonitis to complete tendon ruptures. Tendonitis appears as fusiform swelling with hypoechogenicity and, tears and gaps can be measured. Ultrasound examination can detect shrapnel lesions, and contribute to the planning of surgical correction of ruptures in the Achilles tendon.
Ultrasound is also useful for diagnosing such pathologies of the ankle as tendon and ligament ruptures, and inflammation of the tendon sheath (Figure (Figure2727)[48–51]. Ankle sprain can demonstrate partial or complete tears. The most common torn ankle ligament is the anterior talofibular. Ligaments may appear hypoechoic with fluid, or discontinuous. Similarly, ultrasound allows the appearance of the calcaneo fibular and deltoid ligaments to be seen.
The sonographic appearance of rough fragmentation with saw-teeth appearance is a specific sign which has demonstrated effectiveness in the evaluation of Sever’s disease.
Sonography can be effective in evaluating cases of tibial stress fractures. Routine ultrasound examination includes the anterior tibial, posterior tibial, peroneal and Achilles tendon and the tibiotalar joint is evaluated for effusion or loose bodies.
Tendinitis is visualized in ultrasound as hypoechogenicity of the tendon with increased interfibrillar distance. Retro-calcaneal bursitis and cellulitis can be seen (Figures (Figures2828 and and29).29). Partial tears indicate intrasubstance defects extending toward one surface of the tendon. Tendon discontinuity may indicate the proximal and distal stumps of the tendon. Insertion tendinopathy is seen as a hypoechoic enlargement of the tendon with fluid in the area inserted in the bone. Ultrasound is helpful in evaluating any syndesmosis, as is needed in post traumatic anterior ankle pain and in detecting foreign bodies in the ankle (Figure (Figure3030).
Ultrasound is useful in the assessment of foot lesions such as plantar fasciitis, plantar fascial tears, fibromatosis, morton neuroma, Jones fractures, and fractures of sesamoids and the 5th metatarsal bone.
HIP PATHOLOGY IN CHILDREN
Only rarely can a small effusion of the hip joint be detected by clinical examination. Thus, ultrasound, with its effectiveness in detecting effusion and synovitis, is generally used in the early assessment of hip pathology. Detection of an effusion allows direct aspiration to decrease the pressure and to evaluate the fluid for possible septic arthritis. Prompt aspiration in suspected cases of septic arthritis obviates the need for lengthy workups, and guides further treatment. Further, ultrasound can be used to visualize fragmentation of the femoral head in “Perthes disease”, and to detect a slipped capital femoral epiphysis.
DEVELOPMENTAL DYSPLASIA OF THE HIP (DDH)
Clinical assessment of the newborn hip is routinely performed in the first days of life. Static and dynamic scanning by ultrasound enhances the rate of early detection of hip abnormalities. Ultrasound follow-up is part of the routine management of hip dysplasia.
BONE AND MUSCLES PATHOLOGY
Assessment of the echogenic surface of bone and the acoustic shadow behind it can reveal abnormalities. Although sonography is not generally the examination of choice for the diagnosis of bone pathology, it should not be ignored, since significant pathologies, including fractures, bone erosions and lytic lesions, are occasionally detected.
Ultrasound can be used to detect subperiosteal collections of fluid in early osteomyelitis, as well as fractures, osteophyte, and bone tumors with bone damage. It provides excellent anatomical detail of the cortical surface of superficial bone. In cases of exostosis, it may be used to measure the thickness of the cartilage cap. The use of ultrasound for the diagnosis of fractures is gaining more and more interest. When ultrasound evaluation is targeted and combined with an orthopedic examination of the pathological area, precise demonstration of cortical disruption, soft tissue damage, and hematoma are possible. Knowledge of bone anatomy is essential for complete ultrasound evaluation of the musculoskeletal system.
Muscle pathologies such as rupture, calcification, myositis ossificans, hemorrhage can be also assessed by ultrasound.
MUSCULOSKELETAL ULTRASOUND IN RHEUMATOLOGY
During recent years, musculoskeletal ultrasound has become recognized as an effective imaging technique for the diagnosis and follow-up of patients with rheumatic diseases[62–67]. While most commonly used in the assessment of soft tissue disease or detection of fluid collection, ultrasound can also be used to visualize other structures, such as cartilage and bone surfaces[62,68,69].
Ultrasound is an invaluable diagnostic technique in orthopedic practice. Technological developments in resolution quality have increased the diagnostic possibilities while improvements in picture quality have increased clinical applications.
Muscoskeletal sonography is safer and more informative than X-rays for evaluating soft tissues pathology. Compared with MRI, it is accessible to all patients, without contraindications, and provides real time dynamic assessment.
Musculoskeletal ultrasonography is indicated for evaluation of soft tissue damage, particularly in sports injuries. The most practical uses are the evaluation of tendon structures, dynamic examination in motion, and the assessment of articular structures and diseases. Bursal disease with synovitis can be easily detected. Ultrasound should be performed when investigating rotator cuff tears, inflammation, calcific tendinitis and impingement syndrome, frozen shoulder, tennis or golfer elbow, biceps muscle, and distal biceps tendon insertion. Other indications include carpal tunnel syndrome, cysts of the wrists, pathology of tendon of the hands, retained foreign bodies, joint effusion, diseases of the knee, meniscal cysts, Baker cyst, ligament and osteoarthritis changes, Osgood Schlatter, and patella bipartite. In the ankle, ultrasound can detect tibio talar effusion, pathology of tibialis anterior, posterior, peroneal tendons, Achilles tendon, plantar fasciitis, and Morton neuroma.
Musculoskeletal sonography should be performed by an experienced operator with extensive knowledge of anatomy. Investment in training is justified in light of the contribution of this technology to diagnostic and therapeutic orthopedics and its accessibility to patients due to safety, non- ionizing radiation, low operating costs, lack of contraindications, and availability in locations distant from medical centers.