Ultrasound Versus Magnetic Resonance Imaging in the Diagnosis of An Acute Hamstring Tear

A 34-year-old man presented with a left posterior thigh hematoma, swelling, and extensive bruising in the medial aspect of his left hamstrings. During a softball game a week earlier, while sprinting to the first base, he felt a sudden sharp pain in the posterior aspect of his left thigh. He subsequently experienced swelling, extensive bruising, and limitations in his functional activities of daily living, including walking and sitting, and he had a sense of weakness in the left knee. He started the rest, ice, compression, elevation (RICE) program acutely and used nonsteroidal anti-inflammatory drugs for 10 days, which led to an improvement in his symptoms, after which he started a progressive physical therapy program that included stretching, strengthening, and a gradual return to his previous activities. Upon examination, the patient had a slight antalgic gait, with a shorter step length on the affected side. Inspection revealed diffuse bruising in the medial and lateral hamstrings (Figure 1), a gap in the medial hamstrings visible with knee flexion, and decreased strength in knee flexion compared with the right side. Focal tenderness was present at the distal insertion of the left semitendinosus and semimembranosus muscles. Range of motion was full,withpainattheendofkneeflexion.Findingsofaneurologicexaminationwerenormal, other than weakness of knee flexion as a result of pain. Hamstring muscle injuries are common among sprinters, hurdlers, and long jumpers. They also occur in sports that involve sprinting, especially football and field hockey. The majority of these injuries occur in the biceps femoris muscle, mainly at the muscle-tendon junction. Hamstring injuries typically occur from eccentric overload [1,2]. Damage occurs first at the musculotendinous junction, which typically is the weakest component of the hamstring muscle [3]. Imaging studies can help fully define hamstring injuries, guide therapy, and predict prognosis. Ultrasonography (US) of this patient’s bilateral hamstrings was performed and showed tearing of the left semitendinosus and biceps femoris at the musculotendinous junction. The transverse (Figure 2) and sagittal (Figure 3) images show torn, irregular muscle edges with retraction of fibers surrounded by hypoechoic and anechoic hematoma and fluid. US increasingly is being utilized to evaluate the musculoskeletal system. US is an attractiveoptiontohelpdiagnosehamstringsinjuriesbecauseitcanbeperformedatalower cost than magnetic resonance imaging (MRI), it does not expose patients to ionizing radiation (as is the case with computed tomography), and it may be more widely available than MRI in some areas. Additional advantages of US over MRI include visualization of tendon fibers, color Doppler or power Doppler imaging, dynamic assessment, and determination of focal tenderness to sonopalpation. Early diagnosis and classification of an injury may help determine if conservative treatment or surgery is appropriate. At the time of the initial injury, US assessment has a sensitivity similar to that of MRI imaging in the depiction of hamstring injuries. MRI has been shown to be more sensitive in the follow-up evaluation of hamstrings. MRI better demonstrates the full extent of muscle strain in which the longitudinal length has a strong correlation with the time required for rehabilitation and recovery [4,5]. In other words, the size of a tear is associated with the number of days lost from competition [6]. Avulsion injury of the hamstring complex is more serious than isolated muscle strain because it necessitates prompt surgical repair. Avulsion injuries tend to occur more