Mnemonics and Metaphorical Videos for Detecting/Diagnosing Musculoskeletal Sonopathologies : American Journal of Physical Medicine & Rehabilitation

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Mnemonics and Metaphorical Videos for Detecting/Diagnosing Musculoskeletal Sonopathologies

Jačisko, Jakub MD; Ricci, Vincenzo MD; Mezian, Kamal MD, PhD; Güvener, Orhan MD; Chang, Ke-Vin MD, PhD; Kara, Murat MD; Kobesová, Alena MD, PhD; Özçakar, Levent MD

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American Journal of Physical Medicine & Rehabilitation 102(2):p 184-190, February 2023. | DOI: 10.1097/PHM.0000000000002119

Abstract

This feature is a unique combination of text (voice) and video that more clearly presents and explains procedures in musculoskeletal medicine. These videos will be available on the journal’s Website. We hope that this feature will change and enhance the learning experience.

Walter R. Frontera, MD, PhD

Editor-in-Chief

Musculoskeletal ultrasound (US) identifies a broad range of pathologies, that is, traumatic, inflammatory, and neoplastic. Similar to other imaging modalities, for example, x-ray, computed tomography, and magnetic resonance imaging; typical sonographic images of certain pathological/abnormal conditions can be rendered and “highlighted” for the daily practice/language of musculoskeletal sonographers. Of note, metaphoric “signs” promote learning and retention of the characteristic appearances (via the limbic system, affecting memory consolidation and retrieval) and allow the examiners to easily recall the specific condition.1,2 In this regard, the following text and accompanying figures/videos represent a collection of findings pertaining to commonplace pathological conditions. This article is the second part of a series—after the characteristic/metaphoric descriptions of normal musculoskeletal structures.3

CROCODILE MOUTH

Most of the supraspinatus tendon tears ensue in the distal insertion (critical) zone. Whereas short-axis view (“tire appearance”) is quite demonstrative for a detailed description of the rupture,3 long-axis view of the tendon distal to the acromion would also be guiding in the initial step. In other words, the convex “bird’s beak”3 might no more be present or, even worse, be replaced by an irregular and “scary” crocodile mouth (Fig. 1).4

F1
FIGURE 1:
Crocodile mouth. Long-axis view of the distal insertion of the supraspinatus tendon (SSP). H indicates humerus; A, acromion.

FLAT TIRE

Supraspinatus tendon tears often appear as anechoic or hypoechoic on US. During short-axis imaging, a healthy tendon is convex (looking like a “tire”)3 and cannot be compressed under sono-palpation. In case of a full-thickness tear, the appearance will turn into a flat tire whereby deltoid muscle and the subdeltoid bursa would be filling the space.5 Needless to say, if the image of a flat tire is not straightforward, compression with the probe would be noteworthy to make it apparent (Video 1, https://links.lww.com/PHM/B859).

BRIDGE

Soft tissue calcifications can be caused by a broad range of pathologies, that is, tendinopathy, myositis ossificans, rheumatic conditions, and malignancy.6 Notably, whereas dense (hard) and large calcific deposits produce a typical posterior acoustic shadowing,6,7 less dense (soft) or small calcifications may not always be accompanied by shadowing. Likewise, the phase of calcification may also impact whether the lesion will produce this artifact.6 Although calcifications vary in density, location, size, and shape, the sonographic appearance of superficial ones can resemble a “single-cistern” bridge (Fig. 2) and the river represents the acoustic shadowing artifact.

F2
FIGURE 2:
Bridge. Calcific deposition (C) in hypodermis in the long-axis view. AS indicates acoustic shadowing artifact.

HALO/EYE OF THE TIGER

Synovial (parietal and visceral) sheaths are structures that facilitate the sliding of tendons.8 In the presence of inflammation within tendon sheaths (long head of the biceps tendon, wrist extensor tendons etc.), the fluid appears as a dark halo on US examination. Of note, because the synovial sheath can sometimes be associated with the joint space (e.g., shoulder), it is necessary to differentiate primary tendon problems from other articular pathologies. Furthermore, as comparison is an important advantage (as well as a prerequisite) of US examination, bilateral halos may be reminiscent of tiger eyes (Fig. 3) (Video 2, https://links.lww.com/PHM/B860).

F3
FIGURE 3:
Tiger eyes. Bilateral effusion (*) around the long head of biceps brachii tendon (B) in short-axis views. D indicates deltoid muscle; H, humerus.

SNOWSTORM

In gout(y arthritis), the main sonographic findings suggestive for monosodium urate crystal deposition are tophi, the double contour sign, and the snowstorm. The characteristic image of the latter consists of multiple hyperechoic spots floating within the synovial fluid and surrounded by the synovium (Fig. 4). These microtophi correspond to aggregates of monosodium urate monohydrate crystals. Concerning the snowstorm appearance, the sensitivity and specificity in detecting monosodium urate deposition have been reported as 30.3% and 90.9%, respectively.9

F4
FIGURE 4:
Snowstorm. Short-axis view of the olecranon bursa. B indicates bone.

BOTTLE NECK

When a peripheral nerve becomes entrapped, the deformation results in pressure gradients, which redistributes the tissue to areas of lower pressure. In addition, compression inhibits normal intraneuronal axoplasmic transport and various substances; for example, transmitter substance vesicles and cytoskeletal elements accumulate.10 Eventually, mechanical/ischemic factors can cause nerve swelling usually just proximal to the entrapment site. In certain cases (e.g., after carpal tunnel surgery), nerve edema can also be present distal to the entrapment site and appear as an hourglass.11 In daily clinical practice, peripheral nerves are usually/easily tracked in short axis, and if an abnormality (e.g., increased nerve caliper or hypoechogenicity) is detected, the probe is rotated 90 degrees and the typical appearance of bottle neck can be observed in the long-axis view. Needless to say, the neck represents the point of nerve compression (Fig. 5).

F5
FIGURE 5:
Bottle neck. Long-axis view of the median nerve (N) and flexor tendons (T). B indicates carpal bone.

COMET TAIL

In the universe, a family of asteroids is usually identified for their brilliant tails. Likewise, in the musculoskeletal system, metallic foreign objects (screw, implant, etc.) give this reverberation artifact (long hyperechoic bands) owing to their feature of randomly reflecting the US beams. In daily clinical practice, it is also not uncommon to detect certain (otherwise unknown) foreign objects after recognizing these comet tails (Fig. 6) (Video 3, https://links.lww.com/PHM/B861).

F6
FIGURE 6:
Comet tail. Short-axis imaging of the distal forearm in a patient operated for radius fracture. S indicates screw; B, bone.

RAT TAIL, TARGET, AND BAG OF WORMS

High-resolution US is considered as the mainstay for detecting/diagnosing peripheral nerve sheath tumors. The most prevalent types of solitary (benign) tumors in adults are schwannoma and neurofibroma. The former is derived from neoplastic schwann cells and the latter originates from schwann cells as well as from other tissues of the nerve sheath. Although the definitive diagnosis is histopathological, both display some characteristic findings on US examination. For instance, a round shape strongly suggests a schwannoma, a fusiform shape is relatively typical for a neurofibroma, and an oval shape is common for both. In contrast to neurofibromas, schwannomas appear in an eccentric position with regard to the peripheral nerve trunk.12 Accordingly, the characteristic rat tail (a thin hyperechoic line entering and exiting the nerve) appearance (Fig. 7) is present in approximately half of the schwannoma patients.13 Another US feature—which is more common in neurofibromas—is the target sign.14 It is characterized by a hyperechoic fibrous center with a hypoechoic periphery (Fig. 8) that contains predominantly myxomatous material.15 A subtype of neurofibromas that frequently develops in individuals with neurofibromatosis type 1 is plexiform neurofibroma. In contrast to localized neurofibromas that arise from a single peripheral nerve, plexiform neurofibromas originate from multiple nerves and involve perineural components as well as other soft tissue components. As such, a bulging mass that comprises tortuous bundles of enlarged, disorganized nerves and connective tissues appears as bag of worms on macroscopic inspection and US alike.16 The US appearance is that of multiple hypoechoic nodules, poor margins, and several feeding vessels within hyperechoic connective tissue (Fig. 9). Notably, these tumors are at significant risk for eventual malignant transformation.

F7
FIGURE 7:
Rat tail. Radial nerve schwannoma (S) in long-axis view. H indicates humerus.
F8
FIGURE 8:
Target. Median nerve neurofibroma (N) in long- and short-axis views.
F9
FIGURE 9:
Bag of worms. Plexiform neurofibroma (PN) originating from superficial/subcutaneous nerve(s).

BLACK HOLE

Sono-tracking of a skeletal muscle in short-axis view can show sudden disappearance of the normal “starry sky” appearance (alternation of hypoechoic fascicles and hyperechoic perimysium)—being replaced by a large black hole. Similar to the absence of light in black holes of the universe, no acoustic interfaces can be identified inside an acute/subacute muscle injury due to hemorrhage instead of connective tissue and muscle fibers. Under prompt sono-palpation, compressibility/displacement of the black hole can confirm the lesion as well as the possibility of aspiration5 (Video 4, https://links.lww.com/PHM/B862).

MISTY MUSCLE

Sono-tracking of a denervated skeletal muscle in short-axis view can clearly show fibroadipose involution. In other words, unlike the “starry sky,” a coarse pattern with low visibility of the hypoechoic background (muscle fibers) and increased hyperechoic connective tissues (perimysium) can be observed, that is, a misty muscle (Fig. 10). Of note, the blurred muscle tissue would also reduce the sonographic visibility of deeper anatomical layers—owing to the presence of excessive/pathological acoustic interfaces that attenuate the ultrasonic beam.

F10
FIGURE 10:
Misty (left) vs. starry (right) sky. Short-axis view shows fibrofatty involution due to chronic denervation of tibialis anterior muscle.

CLOUDS

Myositis ossificans is a rare complication that mostly occurs after traumatic large muscle injury. US can significantly be contributory in the early diagnosis, even at stages when radiographs are negative.17 Multiple/irregular hypoechoic and hyperechoic layers accompanied by posterior acoustic shadowing (as discussed above) is the main scenario mimicking clouds or cloudy weather18 (Video 5, https://links.lww.com/PHM/B863).

PISTOL GRIP DEFORMITY

Femoroacetabular impingement syndrome is a clinical entity that refers to the disrupted relationship between the two bones due to morphological abnormalities from either side. The two basic types (i.e., cam and pincer) can be evaluated by x-ray, magnetic resonance imaging, and computed tomography,19 but US examination might be of additional values if performed dynamically.20 During long-axis imaging for a cam lesion, the shape of the proximal femur resembles a pistol grip (Video 6, https://links.lww.com/PHM/B864).

BOOMERANG AND SPEECH BUBBLE

The bursa between semimembranosus and medial head of the gastrocnemius tendons is the place of origin for popliteal/Baker’s cyst. While its normal or mildly swollen shape resembles a boomerang, the appearance looks more like a speech bubble in case of further fluid collection (Fig. 11). The latter ensues mainly because of the dilatation of the superficial arm of the bursa. Of note, although the accumulation often contains homogeneous/anechoic fluid, different sonographic findings—ranging from fibrous septa to hypertrophic/floating synovial villi floating inside the cavity—might not be uncommon. Accordingly, in addition to the shape of a Baker’s cyst, the appearance of its content would also be important before an onward intervention (Video 7, https://links.lww.com/PHM/B865).

F11
FIGURE 11:
Boomerang. Short-axis imaging over the distal semimembranosus tendon (T) and the proximal gastrocnemius muscle (M). B indicates Baker’s cyst.

VOLCANO (ERUPTION)

In several joints of the musculoskeletal system, the presence of an intra-articular triangular fibrocartilage can be related to a peculiar pathological finding that looks like a volcano (eruption). For instance, longitudinal scan over the acromioclavicular joint or the medial aspect of the knee joint shows—in some patients—the bulging of the aforementioned intra-articular fibrocartilage also bulging the overlying capsular tissue. In this sense, the joint line can be considered as the mouth of the volcano and the ejected/extruded meniscocapsular tissue as the boiling magma. Needless to say, clear recognition of these pathologies might easily navigate the clinician for prompt interventional planning to “cool down” the natural phenomenon (Figs. 12 and 13) (Video 8, https://links.lww.com/PHM/B866).

F12
FIGURE 12:
Volcano (eruption). Long-axis view shows the meniscal (M) and capsular (C) bulging. *Femoral and tibial osteophytes.
F13
FIGURE 13:
Volcano (eruption). Long-axis view over the sternoclavicular joint shows normal and extruded (E) sides. *Fibrocartilage.

SHARK HEAD AND LIPS

Tennis leg refers to strain lesions of the myotendinous junction of the medial head of the gastrocnemius muscle. Intramuscular tear, deteriorated pennation pattern, fluid in the fascial planes, and hematoma can be visualized under US examination.5,21 Especially, the presence of fluid between the medial head of the gastrocnemius and soleus muscles/aponeuroses might appear as a shark head with open mouth during long-axis view. On the other hand, in short-axis imaging, the same vista might sometimes look like lips (Fig. 14) (Video 9, https://links.lww.com/PHM/B867).

F14
FIGURE 14:
Lips. Tennis leg in short-axis view. * Organizing (black and white arrowheads) hematoma (asterisks). The annotations for the videos have been embedded for the reader’s convenience.

ATOMIC MUSHROOM

In patients with clinical suspicion of Morton’s neuroma, (short-axis view) dynamic assessment can be performed over the metatarsal heads using the Mulder maneuver. A hypoechoic mass protruding outward or a typical artifact when it is located inward can be quite pathognomonic.5 The outward “jumping” neuroma can appear as the activation of an atomic bomb, that is, exploding and generating an atomic mushroom (Video 10, https://links.lww.com/PHM/B868).

REFERENCES

1. Schattner A: More on emotions in medical education and practice. Acad Med 2017;92:726–7
2. Roozendaal B, McEwen BS, Chattarji S: Stress, memory and the amygdala. Nat Rev Neurosci 2009;10:423–33
3. Jačisko J, Mezian K, Güvener O, et al.: Mnemonics and metaphorical videos for teaching/learning musculoskeletal sonoanatomy. Am J Phys Med Rehabil 2022;101:e189–93
4. Tekin L, Kara M, Özçakar L: When the parrot’s beak becomes the crocodile’s mouth: a story on shoulder ultrasound. Rheumatol Int 2013;33:2447–8
5. Özçakar L: Sonographic Atlas for Common Musculoskeletal Pathologies. Milan, Italy, Ediermes srl, 2017. Available at: https://books.google.cz/books?id=LJmvswEACAAJ. Accessed October 22, 2022
6. Wu WT, Chang KV, Hsu YC, et al.: Artifacts in musculoskeletal ultrasonography: from physics to clinics. Diagnostics 2020;10:645
7. Ricci V, Soylu AR, Özçakar L: Artifacts and artistic facts: a visual simulation for ultrasound training. Am J Phys Med Rehabil 2019;98:521–5
8. Cohen MJ, Kaplan L: Histology and ultrastructure of the human flexor tendon sheath. J Hand Surg Am 1987;12:25–9
9. Ogdie A, Taylor WJ, Neogi T, et al.: Performance of ultrasound in the diagnosis of gout in a multicenter study: comparison with monosodium urate monohydrate crystal analysis as the gold standard. Arthritis Rheumatol 2017;69:429–38
10. Mackinnon SE: Pathophysiology of nerve compression. Hand Clin 2002;18:231–41
11. Nakamichi KI, Tachibana S: Enlarged median nerve in idiopathic carpal tunnel syndrome. Muscle Nerve 2000;23:1713–8
12. Ryu JA, Lee SH, Cha EY, et al.: Sonographic differentiation between schwannomas and neurofibromas in the musculoskeletal system. J Ultrasound Med 2015;34:2253–60
13. Yang F, Chen XX, Wu HL, et al.: Sonographic features and diagnosis of peripheral schwannomas. J Clin Ultrasound 2017;45:127–33
14. Lin J, Jacobson JA, Hayes CW: Sonographic target sign in neurofibromas. J Ultrasound Med 1999;18:513–7
15. Stull MA, Moser RP Jr., Kransdorf MJ, et al.: Magnetic resonance appearance of peripheral nerve sheath tumors. Skeletal Radiol 1991;20:9–14
16. Woertler K: Tumors and tumor-like lesions of peripheral nerves. Semin Musculoskelet Radiol 2010;14:547–58
17. Bagnulo A, Gringmuth R: Treatment of myositis ossificans with acetic acid phonophoresis: a case series. J Can Chiropr Assoc 2014;58:353–60
18. Abate M, Salini V, Rimondi E, et al.: Post traumatic myositis ossificans: sonographic findings. J Clin Ultrasound 2011;39:135–40
19. Pun S, Kumar D, Lane NE: Femoroacetabular impingement. Arthritis Rheumatol 2015;67:17–27
20. Mezian K, Ricci V, Güvener O, et al.: EURO-MUSCULUS/USPRM dynamic ultrasound protocols for (adult) hip. Am J Phys Med Rehabil 2022;101:e162–8
21. Shah JR, Shah BR, Shah AB: Pictorial essay: ultrasonography in ‘tennis leg’. Indian J Radiol Imaging 2010;20:269–73
Keywords:

Ultrasonography; Muscle; Nerve; Funny; Multimedia

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