To begin place a patient in a supine position on a surgical bed with their legs extended. Set the preset on the probe scanner to the musculoskeletal setting. Place the probe transversely on the anterior thigh at about 60%the length from the anterior superior iliac spine to the superior border of the patella.
The quadriceps will appear deep to the subcutaneous tissue and superficial to the femur. To prevent the overestimation of the muscle thickness due to superficial edema, apply firm pressure to the ultrasound probe. If the rectus femoris is difficult to identify, ask the patient to contract their thigh muscles or extend their knee.
Next, press distance, then measure on the ultrasound machine and activate the caliper function. With the cursor, measure the anterior to posterior distance between the deep border of the vastus intermedius and the most superficial fascia of the rectus femoris. Click on acquire to capture the sonographic view.
Repeat the measurement three times, then average the values to minimize the variability. For the measurement of the rectus femoris, adjust the depth with the vertical ruler, then use the horizontal slide bar to adjust the gain until the rectus femoris muscle is centered in the ultrasound frame with clear visibility of its boundaries and the underlying femur. The rectus femoris muscle should be visible as a hypoechoic structure within the anterior thigh compartment with a central echogenic line.
Now activate the caliper function, and trace around the periphery of the rectus femoris muscle carefully. The circumference of the cross section should be displayed automatically. Click on a acquire to capture the sonographic view.
Average the values of three to minimize the variability. The measurements of a healthy subject showed well-defined muscle with uniform echotexture, and clear, continuous fascial planes consistent with non-frail status. A scan of an elderly frail individual showed less defined muscles, a heterogeneous echotexture, and interrupted fascial planes.
