Sonographic Evaluation of Tears of the Gastrocnemius Medial Head ( Tennis Leg )

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1 Sonographic Evaluation of Tears of the Gastrocnemius Medial Head ( Tennis Leg ) Stefano Bianchi, MD, Carlo Martinoli, MD, Ibrahim Fikry Abdelwahab, MD, Lorenzo E. Derchi, MD, Sandro Damiani, MD Rupture of the medial head of the gastrocnemius muscle, or tennis leg, is a common lesion affecting middle-aged persons. An imaging examination may be needed to rule out other diseases and assess the severity of the tear. We reviewed the sonographic images of 65 patients with clinically suspected tennis leg. Fifty-one partial and 14 complete tears were diagnosed. Twenty-five patients had follow-up examinations (15 days to 24 months; mean, 45 days). The torn muscle fibers, hematoma, and the reparative process were appreciated by ultrasonography. Ultrasonography may be a useful noninvasive, low-cost modality for diagnosis and follow-up of tennis leg. KEY WORDS: Muscle, trauma; Gastrocnemius muscle; Soft tissue, injuries; Tennis leg, Muscle strain. R ABBREVIATIONS TL, Tennis leg; CT, Computed tomography; MR, Magnetic resonance; SD, Standard deviation; MTJ, Musculotendinous junction Received April 24, 1997, from the Department of Diagnostic Imaging (S.B., S.D.), E.O. Ospedale Galliera, and Istituto di Radiologia (C.M., L.E. D.), Università di Genova, Genova, Italy; and the Department of Radiology (I.F.A.), Mount Sinai Medical Center, New York, New York. Revised manuscript accepted for publication October 7, Address correspondence and reprint requests to Stefano Bianchi, MD, C.so Paganini 1\5, 16125, Genova, Italy. upture of the distal MTJ of the medial head of the gastrocnemius muscle, also called TL, is one of the most common sportsrelated lesions affecting the middle-aged population. 1 Patients usually injure their calves during active plantar flexion of the foot and simultaneous extension of the knee, which implies simultaneous active contraction and passive stretching of the gastrocnemius muscle. 1 Clinical findings include diffuse swelling and localized, sharp pain of the calf preventing weight-bearing on the affected leg. Although the history and the clinical findings of TL are suggestive, an imaging examination is usually performed to confirm the clinical impression and evaluate the severity and size of the lesion. Standard radiography and CT are not useful in the assessment of acute muscle traumas. Because of its high contrast resolution and multiplanar capability MR imaging is the best modality in the evaluation of soft tissues. However, its high cost and limited availability limit the use of MR imaging. Ultrasonography is a low cost, noninvasive, and well tolerated imaging modality used in the assessment of soft tissue traumas by the American Institute of Ultrasound in Medicine J Ultrasound Med 17: , /98/$3.50

2 158 TEARS OF GASTROCNEMIUS MUSCLE HEAD J Ultrasound Med 17: , 1998 We retrospectively reviewed the sonographic images of 65 patients with clinically suspected TL to determine the sonographic features of TL. MATERIALS AND METHODS We reviewed the sonograms that were compatible with TL that were obtained during the last 3 years. Sixty-five patients (age range, 35 to 75 years; mean, 47 years ± SD) were examined; 47 were men and 18 were women. Patients had an acute, posttraumatic calf pain, subsequent to a sports activity (51 cases) or trivial injury (14 cases). Most patients reported a history of sudden, intense medial calf pain followed by local edema and impaired function. Ultrasonography was performed a variable time after injury (2 hours to 7 days; mean, 4 days). Normal sonographic anatomy of the region was studied in 10 normal volunteers and in the contralateral asymptomatic leg of the patients. Sonographic examinations were performed with and MHz broad band electronic linear array probes. The patients were examined prone with the knees in slight flexion and the legs resting on a pillow, placed under the anterior aspect of both legs, which reduced the stretching of the triceps surae muscle and decreased patient discomfort during the examination. Longitudinal and transverse sonograms of both calves were obtained. No stand-off pad was used. Dynamic examinations included application of various degrees of pressure with the probe and scanning during cautious active and passive dorsiflexion of the foot. Ultrasonography of normal volunteers showed the muscle fibers of the medial head and fibroadipose septa as regularly organized parallel hypoechoic and hyperechoic lines ending in the muscle aponeurosis. A partial tear was diagnosed in the presence of a localized disruption of the regular arrangement of a portion of the MTJ, whereas a complete tear was defined by the involvement of the entire medial head of the gastrocnemius muscle. In three patients, examined in the first months of the study, evacuation of the hematoma was performed with an 18 gauge needle under sonographic guidance. Patients were treated with rest, ice, and nonsteroidal antiinflammatory drugs. No patient was treated surgically. In 25 unselected patients follow-up examinations were obtained (15 days to 24 months; mean, 45 days). RESULTS The anatomic and sonographic appearance of the normal medial head MTJ are depicted in Figure 1. Fifty-one partial and 14 complete tears were diagnosed by ultrasonography. Twenty-four patients with partial tears had small lesions (less than 2 cm) whereas 41 had larger partial lesions or complete tears. In patients with small tears, examined within few hours of the trauma, the absence of a definite hypoechoic or anechoic blood collection made detection of the tear difficult. Careful evaluation of the distal portion of the medial head, however, revealed that muscle fibers and septa did not reach the aponeurosis (Fig. 2A). The majority of these injuries affected the most anteromedial portion of the medial head and could be missed if this region is not evaluated carefully. Dynamic studies or pressure applied with the probe were unhelpful in the detection of small ruptures. In larger partial lesions or in complete tears ultrasonography showed an evident hematoma appearing as a fusiform heterogeneous area between the disrupted medial head and the aponeurosis of the soleus, due to presumed muscle fiber rupture and hemorrhage (Fig. 2B). The distal portion of the injured medial head assumed a heterogeneous echogenic appearance due to hemorrhage and rupture of muscle fibers. After a few days a definite anechoic hematoma was clearly evident and readily manifested on sonography. Usually the blood collection extended cranially, in the loose connective tissue between the two aponeuroses (Fig. 2C). Dynamic examination performed during dorsal and plantar flexion of the foot did not provide additional information from standard examination. Various degree of pressure with the probe showed partial collapse of the fluid. Needle puncture and drainage, performed in three patients, revealed serosanguineous fluid consistent with a hematoma. However, all patients had a recurrence of fluid collection as shown by ultrasonography performed after 1 week. Follow-up examinations showed the reparative process as a hypoechoic area starting from the periphery of the hematoma and gradually proceeding toward the center while the amount of central fluid decreased in size (Fig. 3A). Because of the organization of the peripheral portion, graded compression through the probe demonstrated partial collapse of only the central anechoic fluid portion (Fig. 3B). In nine patients, examined 1 year or more after the trauma and clinically asymptomatic, sonography showed a hyperechoic area interposed between the medial head and the soleus muscle, probably corresponding to fibrous tissue (Fig. 3C). DISCUSSION The muscle-tendon unit is composed by the muscle belly, the MTJ, the tendon, and the tendon-bone junction. Laboratory studies demonstrated that the MTJ

3 J Ultrasound Med 17: , 1998 BIANCHI ET AL 159 is the structure injured most frequently on extreme overload. 2 The rectus femoris and the medial head of gastrocnemius muscles are the muscles injured most frequently during amateur sports practice. In TL the muscle fibers of the medial head of the gastrocnemius muscle become detached from the distal aponeurosis. Although the exact frequency of partial and total tear is not known, most patients seem to develop partial tears. The condition is frequent in the middle aged, poorly conditioned, physically active patient. 3,4 A powerful contraction of the gastrocnemius muscle with concomitant overstretching of the muscle due to extension of the knee leads to excessive tensile force and disruption of the MTJ. Physical examination typically discloses a painful swollen calf with exquisite local tenderness on the medial side. A The Achilles tendon is unaffected. Although clinical findings are believed to be quite characteristic of TL, previous reports have documented misdiagnosis of this lesion as thrombophlebitis or ruptured Baker cyst. 5 In fact, local edema and excruciating pain can limit physical examination. An imaging modality can confirm the clinical suspicion, exclude other diseases that can mimic TL, and allow assessment of the size of the lesion, which can influence the choice and duration of the treatment. Small tears generally are treated with rest and ice, whereas larger lesions usually require pharmacologic therapy and prolonged immobilization. Ultrasonography has proved to be successful in the evaluation of muscle trauma, including partial and complete muscle ruptures and herniation through the fascia. 6 Figure 1 Anatomy (A) and sonography (B) of the MTJ of the normal medial head of the gastrocnemius muscle. A, The gastrocnemius muscle originates from the supracondylar region of the femur by two distinct portions, the lateral head and the medial head (MH). Both heads insert distally in a broad aponeurosis, which overlies the aponeurosis of the soleus muscle (S). The two distinct aponeuroses (AP), separated proximally by a thin layer of loose connective tissue, subsequently merge to form the proximal portion of the Achilles tendon (AT). B, Longitudinal sonogram of the medial head (MH) of the gastrocnemius muscle shows the aponeurosis (arrow) of the soleus and gastrocnemius as two distinct hyperechoic structures separated by a hypoechoic line representing the interposed connective tissue. Muscle fibers and fibroadipose septa (arrowheads) of the MH appear as regularly organized hypoechoic and hyperechoic parallel lines ending in the aponeurosis. B

4 160 TEARS OF GASTROCNEMIUS MUSCLE HEAD J Ultrasound Med 17: , 1998 Sonographic examination of TL was easy to perform, was painless, and could be completed in 10 to 15 min. The ultrasonographic appearance of TL was quite characteristic. In our cases, although no confirmation with other imaging or surgery was obtained, sonography showed the extent of disruption of the medial head as well as the extension of the uninvolved muscle, which retained the normal organized pattern composed of hyperechoic and hypoechoic structures. Based on the completeness of disruption of the normal appearance, we were able to differentiate between partial and complete lesions. Axial sonograms, in which the entire medial head usually is depicted in the same sonogram, were most useful in differentiating partial from complete lesions. The amount of the proximal retraction of muscle fibers was more evident in the sagittal sonograms. Although in our retrospective study we have not correlated the size of the tear with the duration of symptoms, it can be postulated that this aspect could A have clinical applications. In three patients we performed a needle aspiration of the hematoma under sonographic guidance. Although the blood collection was evacuated almost entirely, as shown by simultaneous sonographic scanning, the follow-up at 1 week showed recurrence of nearly the same amount of fluid. After that we did not perform other needle aspirations and limited ultrasonography to follow-up of the healing process. Clinically, TL must be differentiated from a ruptured Baker cyst, deep venous thrombosis, and, occasionally, Achilles tendon rupture. These conditions can be diagnosed accurately with ultrasonography. In a ruptured Baker cyst, sonography shows fluid extending into the soft tissues distal to the cyst. Misdiagnosis of TL as thrombophlebitis could result in unnecessary anticoagulation and hemorrhagic complications. In popliteal vein thrombosis, hypoechoic material can be seen filling the affected vein, which does not collapse with probe pressure. Color Doppler Figure 2 Acute TL. A, Longitudinal sonogram of a small tear in a case of TL obtained a few hours after the injury. A poorly defined, hypoechoic area (curved arrow) at the distal end of the medial head represents a small myotendinous tear. The disrupted fibroadipose septa (arrowheads) do not reach the aponeurosis (arrow). B, Longitudinal sonogram of a complete tear in a patient with TL obtained after a few hours after the injury shows a poorly defined, irregular hyperechoic fresh blood collection (curved arrows) separating the medial head and the soleus muscle. C, Longitudinal sonogram of a complete tear in a patient with TL obtained a few days after the injury shows a well-defined anechoic blood collection (curved arrow) interposed between the medial head and the soleus muscle. B C

5 J Ultrasound Med 17: , 1998 BIANCHI ET AL 161 examination can assess the disease entity more precisely. Achilles tendon rupture is easily diagnosed by ultrasonography, which shows the cleft in the tendon fibers and the associated hematoma. Plain radiographs and CT scans are unhelpful in diagnosing TL. A previous report described the MR imaging appearance of TL. 7 However, the limited availability MR imaging equipment, the high cost, and the longer duration of the examination restrict its application and limit the frequency of follow-up examinations. Our retrospective study has some limitations. No confirmation of sonographic findings was obtained by surgery or other imaging modalities. No surgical therapy was performed because our patient population was mainly composed of amateur sportsmen not engaged in high level or professional activities and because medical therapy and rest were successful in all patients. MR imaging was not performed because of low availability and high cost. A In summary in our study ultrasonography proved to be an easy to perform, fast, and safe imaging modality to evaluate patients with clinically suspected TL. Size of the tears could be appreciated. In smaller lesions the main sonographic diagnostic feature was the local disrupted arrangement of the muscle fibers and fibroadipose septa. In larger tears usually the presence of a fluid collection separating the injured medial head of the gastrocnemius muscle from the soleus makes the diagnosis straightforward. Healing of TL could be easily evaluated by ultrasonography. The low cost of sonography allowed serial follow-up examinations and optimal monitoring of reparative processes. Other conditions that can mimic TL, such as a ruptured Baker cyst, thrombophlebitis of the popliteal vein, and Achilles tendon ruptures, have characteristic sonographic features and can easily be differentiated from TL. Figure 3 Reparative process and healed TL. A, Longitudinal sonogram of a complete tear in a patient with TL obtained 3 months after the injury shows the reparative process (curved arrow) as a hypoechoic area starting from the periphery of the hematoma (arrowheads). B, In the same patient, graded compression through the probe demonstrated partial collapse of the central anechoic fluid portion (arrowheads). C, Longitudinal sonogram of a complete tear in a patient with TL obtained 12 months after the injury shows complete healing of the tear as a hyperechoic area (curved arrow) corresponding to fibrous tissue interposed between the medial head and the soleus muscle. B C

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