Bilateral quadriceps muscles and suprapatellar recesses injuries: ultrasound evaluation [Sep 2016]

A 49-year-old male patient presented to the emergency department after a heavy object fell on his thighs, causing contusion of both of his quadriceps muscles. Clinical observation revealed linear retraction of the skin on the right suprapatellar area. X-Rays of the femoral bones and knee joints bilaterally didn’t show any fracture. Ultrasound examination revealed contusion of the left vastus medialis muscle and a small amount of fluid in the ipsilateral suprapatellar pouch. (Fig.1,2) The right quadriceps muscle appeared injured at its distal part. There was hyperechogenicity of the right rectus femoris muscle and its fascicular pattern was ill- defined, as a result of the extended contusion of the muscle’s belly. There was also contusion of the right vastus lateralis and intermedius muscles and rupture of intermedius belly peripherally. The subcutaneous tissue appeared hyperechoic and thickened due to edema. (Fig.3) Fluid with a three layer stratification pattern was noted within the right suprapatellar recess. The three layers included an anterior echogenic layer, an anechoic layer in the middle and a hypoechoic layer posteriorly. Fluid also appeared within the lateral and medial bursae of the right knee. (Fig.4, 5) An MRI a few days later confirmed the US findings. (Fig.6)

Direct external muscle trauma may occur in the form of a contusion, haematoma and partial or complete rupture.[1] Contusions affect the actual site of external trauma whereas strains caused by indirect trauma and eccentric contraction typically affect the myotendinous junction.[1,2,3,4] Contusions are graded as mild, moderate or severe depending on the extent of muscle fibers involved and limitation of joint function.[2,5] Undiagnosed or poorly treated muscle lesions can result in long-term complications like cicatricial fibrosis, calcification, fluid collection, serohematic pseudocysts and muscle hernias.[2,4,5] Although clinical examination usually suggests the diagnosis, imaging is imperative in some cases for establishing the final diagnosis.[2] Ultrasonography is the primary imaging modality for the diagnostic work-up of muscle injuries given its advantages, whereas MRI is reserved for some limited cases due to its cost and limited availability. In mild contusion, immediately after injury muscle tissue appears ill-defined hyperechoic due to hemorrhagic infiltration, while perifascial fluid can be seen.[1,2,4,6] In moderate cases, muscle fibers may be ruptured and a haematoma may appear, causing enlargement of the muscle belly. The haematoma may be formed immediately or some days after the contusion and appears anechoic in the acute phase but gradually becomes hyperechoic due to the organization of fibrous tissue. [2,6,7] In severe cases there is complete muscle rupture, resulting in retraction of the belly. The muscle ends can be then seen floating within the haematoma, as in our case. During the healing process, poorly delimited hyperechoic areas are occasionally found and represent scars causing local retraction of muscle fibers.[1,2,6] Dynamic US of the muscle during contraction can be used to better appreciate muscular retraction and make the defect more prominent. Color Doppler technique may identify hyperemia peripherally to the traumatic lesion.[2,4] When it comes to the vastus muscles, the vastus lateralis and intermedialis are usually affected by injuries resulting in partial or complete rupture, because of their exposed location (and their proximity to the femur).[2,4] US demonstrates a discontinuity of the normal striated echogenicity pattern and internal haematomas.[2] MRI can be used in cases of limited visualization of muscle injuries with US, for example in deep injuries. MRI is also considered superior to US for monitoring the muscle healing process.[5,6]