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Fig. 5.62 a, b a Subacute grade II tear of the medial gastrocnemius at the tenomuscular junction. Note the hematoma in the tear between gastrocnemius and soleus.b Power Doppler analysis shows the reactive hyperemia in the bellies

Fig. 5.62 a, b a Subacute grade II tear of the medial gastrocnemius at the tenomuscular junction. Note the hematoma in the tear between gastrocnemius and soleus.b Power Doppler analysis shows the reactive hyperemia in the bellies

Result of a grade III tear of the abductor longus muscle.a The EFV US scan shows the cranial retraction of the fibres. b MR scan of the same patient (SE T1W)

Result of a grade III tear of the abductor longus muscle.a The EFV US scan shows the cranial retraction of the fibres. b MR scan of the same patient (SE T1W)

phases, the high echoes from the hematoma may limit assessment of the lesion, by underestimating its actual dimensions. 48-72 hours after the trauma, the collection becomes diffusely anechoic, allowing correct measurement of the lesion. When evaluating the healing at follow-up, US will show progressive resorption of the blood collection and hyperechoic tissue filling the lesion from the periphery to the center.

US is extremely important to define the type of muscle injury and the site and degree of the lesion, so that a correct therapeutic plan and an accurate prognostic evaluation can be made. US also has a fundamental role in follow-up, when assessing healing.

When muscle injuries are not correctly treated they can result in an unfavorable outcome with severe sequelae. US can detect fibrous scars (Fig. 4.57), sero-hemorragic cysts and myositis ossi-ficans. Scar tissue has a hypoechoic appearance and an acoustic shadow can be seen behind the areas affected by myositis ossificans, identifiable with ultrasound at earlier stages than with conventional radiology (Fig. 4.55).

Less commonly, as a result of sport-related trauma (for example a violent blow hitting the thigh or the leg), an acute compartmental syndrome consisting of compression of vascular and nervous structures by edema and hematoma can develop. US assessment of the adjacent vascularity complemented with color Doppler techniques, is fundamental for the differential diagnosis. Compart-mental syndrome is more frequently derived from prolonged strain (Delayed-Onset Muscle Soreness (DOMS)), as seen in long distance runners or after repeated violent impacts on a body region. In these cases, the volume of muscle involved is increased by edema, with a inhomogeneous increase in basal echogenicity wich can hide the regular myofibril-lar echoes.

Tendon and ligament tears

Rupture of a tendon can be the result of direct penetrating trauma or indirect trauma caused by excessive loading during physical activity. In athletes,injury of a tendon is usually related to a pre-existing degenerative condition of the tendon itself.

A typical example of this kind of injury is the rupture of the distal segment of the biceps tendon that, when the rupture is complete, can be retracted proximally to the elbow [110].

Likewise, the quadriceps and patellar tendons can be damaged by violent distraction of the extensor system of the knee, which can result in rupture at their insertion. Most tears occur at the myotendi-nous junction, while a small amount of them occur in the parenchyma. For instance, the Achilles tendon can be torn at the myotendinous junction, in the parenchyma, or at the enthesis, though the common site of rupture is 4 to 6 cm from its insertion onto the calcaneum. This is an area of relative weakness because of the poor vascularization of the region (critical area) (Fig 5.64) [111].A critical area is also present on the pre-insertional segment of supraspinatus.

When evaluating a tendon lesion plain film findings are usually poor, non-specific or limited to small bony detachments. Radiological confirmation of a tendon tear must be performed by the application of more specific and sensitive imaging techniques, such as US and MR [112]. The most common site of ten don rupture is the insertion onto the bone and, in adults, this can result in small bony avulsion whilst in children and teenagers these lesions may result in partial or complete detachment of the corresponding growing cartilage. In this last case, ultrasound must be complemented with a plain film or with a CT or MR scan if doubt persists.

Ligaments are often involved in sport traumas and must be carefully assessed because their rupture can often lead to instability of the involved joint. In acute conditions, clinical examination is difficult to perform because of the effusion, pain and muscular contraction: these patients can be easily examined with US. If the ligament is partially torn, the involved segment appears hypoe-choic and thickened (Fig. 5.65).

In complete ruptures, the ligament appears discontinuous and its stumps are separated by hematoma appearing anechoic or hypoechoic according to the time passed since the traumatic event (Fig. 4.53).

It is important to keep in mind that US can assess superficial ligaments but not deep ones; moreover, it cannot detect any other lesions occurring at the same time, such as meniscal tears, osteochondral lesions, hidden fractures or bone edema. These lesions must be assessed with a CT or a MR scan.

A particularly important example of ligament tear for the rheumatologist is that involving is the ulnar collateral ligament (UCL). Moreover, rheumatoid arthritis may cause partial or complete tears of the UCL. Clinical findings and diagnostic imaging are extremely important to reach a final diagnosis. A reported history of violent trauma with the

Subcutaneous complete rupture of a degenerative Achilles tendon. a The US scan shows a complete tear. Note the effusion between the stumps. b The MR scan confirms the diagnosis (SE T1W)

Subcutaneous complete rupture of a degenerative Achilles tendon. a The US scan shows a complete tear. Note the effusion between the stumps. b The MR scan confirms the diagnosis (SE T1W)

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