463.A 45-year-old plumber presented in the clinic complaining of long-
standing pain in the elbow. Subsequent examination revealed normal flexion/
extension at both the elbow and the wrist, but weakened abduction of the
thumb and extension at the metacarpophalangeal joints of the fingers.
Those symptoms were found to be caused by entrapment of the posterior
interosseus nerve. Which of the following muscles could itself cause
entrapment of the posterior interosseus nerve?
a. Extensor carpi ulnaris
b. Extensor indices
c. Anconeus
d. Extensor digitorum
e. Supinator
464.A 67-year-old woman slipped on a scatter rug and fell with her right
arm extended in an attempt to ease the impact of the fall. She experienced
immediate severe pain in the region of the right clavicle and in the right
distal arm. Painful movement of the right arm was minimized by holding
the arm close to the body and by supporting the elbow with the left hand.
There is marked tenderness and some swelling in the region of the clavicle
about one-third of the distance from the sternum. The examining physician
can feel the projecting edges of the clavicular fragments. The radiograph
confirms the fracture and shows elevation of the proximal fragment with
depression and subluxation (underriding) of the distal fragment. Traction
by which of the following muscles causes subluxation (the distal fragment
underrides the proximal fragment)?
a. Deltoid muscle
b. Pectoralis major muscle
c. Pectoralis minor muscle
d. Sternomastoid muscle
e. Trapezius muscle
Extremities and Spine 565