total hip replacement surgery, the head and neck of the femur are replaced with artificial components. In this way, the location of the joint replacement can alter the musculoskeletal geometry and thus the ability of the muscles to generate moment on the hip. Assume that the insertion (terminal location) of the gluteus medius muscle has been moved 10 mm medially as a result of hip replacement surgery, as shown in Fig. Prob.-15a and whose locations are summarized in the table below. Fig. Prob15a: Total Hip Replacement Surgery Model a) Determine the effect of surgery on the moment arm r of the indicated muscle above the hip in the frontal plane, that is, compare rpre v/s rpost. b) During single-limb walking, the ground reaction force is W=800 N and acts at a distance medial to the hip center of d=100 mm. Assuming that the person has a height of H=1.8 m and a mass of M=80 kg, calculate the abductor muscle strength to balance the trunk in the frontal plane before and after surgery; explain the implications this could have on the abductors. Obs: you should consider the force of gravity but neglect the inertial forces due to accelerations.
In total hip replacement surgery, the head and neck of the femur are replaced with artificial components. In this way, the location of the joint replacement can alter the musculoskeletal geometry and thus the ability of the muscles to generate moment on the hip. Assume that the insertion (terminal location) of the gluteus medius muscle has been moved 10 mm medially as a result of hip replacement surgery, as shown in Fig. Prob.-15a and whose locations are summarized in the table below.
Fig. Prob15a: Total Hip Replacement Surgery Model
a) Determine the effect of surgery on the moment arm r of the indicated muscle above the hip in the frontal plane, that is, compare rpre v/s rpost.
b) During single-limb walking, the ground reaction force is W=800 N and acts at a distance medial to the hip center of d=100 mm. Assuming that the person has a height of H=1.8 m and a mass of M=80 kg, calculate the abductor muscle strength to balance the trunk in the frontal plane before and after surgery; explain the implications this could have on the abductors. Obs: you should consider the force of gravity but neglect the inertial forces due to accelerations.
Fig. 15b: person walking, all his weight falls on a single limb
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