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Walter R. Frontera, MD, PhD
A 34-yr-old man had strained his right calf 2 wks ago. Despite the analgesic treatment, he still experienced local/moderate pain (6/10 points on the visual analog scale) during level walking. Accordingly, he was referred for ultrasound (US) scanning. Physical examination revealed tenderness and ecchymosis over the middle third of the right calf. The US imaging revealed partial detachment of the medial gastrocnemius muscle fibers from the deep aponeurosis. A fusiform and anechoic compartment was seen separating the medial gastrocnemius and underlying soleus muscles. Strain US elastography was applied to further image the lesion. During rhythmic compressions, the color of the lesion (mostly being red) was significantly different from that of the surrounding area (being either blue or green; Fig. 1A, Video 1). As the target had much more elasticity than the adjacent muscles, we speculated that its main component was fluid. The US-guided aspiration yielded 3 ml of serosanguineous fluid (Fig. 1B). The patients reported complete symptom relief on the follow-up.
Tennis leg is a general term used to describe mid-calf strain, whereby the medial gastrocnemius muscle is the most frequently injured site. The US imaging is useful in grading its severity based on Peetrons classification as follows: grade 1, normal US findings; grade I, minimal change in muscle (<5%) echotexture; grade II, partial rupture of the affected muscle; grade III, complete muscle rupture with formation of a retraction stump and an intramuscular hematoma.1 In our case, separation of the muscle fibers from their attached aponeurosis could be classified as grade II injury. Herein, it is noteworthy that accumulation of blood/fluid between the muscles is commonplace where early drainage promotes symptom relief and healing of myofascial tears.1 Herewith, it is sometimes difficult to determine whether the intermuscular anechoic area can be aspirated or not—in other words, whether an intervention is to be performed or not. In this sense, dynamic assessment under B mode US imaging would be contributory but can still be less helpful if the muscle is located too deep to be compressed promptly.
The US elastography is an emerging imaging tool to evaluate tissue compressibility, and it has two types, that is, strain and shear wear elastography.2 The former type quantifies elasticity based on the percentage of tissue displacement along the axial direction under manual compression from the transducer.3 The latter estimates elasticity from the velocity of shear waves traveling along the horizontal axis after the target receives fixed acoustic impulses from the transducer.3 Strain imaging has often been criticized for lower reproducibility than shear wave imaging because of vulnerability to variations of the man-made axial stress.2 However, in our case, the aforementioned point actually turned out to be an advantage. Similar to “sonopalpation,” which is commonly used in examination, strain imaging allowed us to become quickly aware of the regional compressibility. The color diagram further demonstrated the most likely area to encapsulate fluid and reasonably for subsequent aspiration. Furthermore, elastography can be used to follow up muscle tears or hematomas and to examine whether scars or muscle fibrosis develop thereafter. In short, this report highlights the novel application of strain US elastography in the management of a sport injury.
1. Chang KV, Wu WT, Ozcakar L: Ultrasound imaging and rehabilitation of muscle disorders: part 1. Traumatic injuries. Am J Phys Med Rehabil
2. Lin CP, Chen IJ, Chang KV, et al.: Utility of ultrasound elastography in evaluation of carpal tunnel syndrome: a systematic review and meta-analysis. Ultrasound Med Biol
3. Chang KV, Wu WT, Chen IJ, et al.: Strain ratio of ultrasound elastography for the evaluation of tendon elasticity. Korean J Radiol