A seven-year-old boy breaks his tibia and requires immobilization by a hard cast
for six weeks until the break heals. A potential consequence of this therapy is atrophy
of the
A. pectoralis major. C. gastrocnemius.
B. serratus anterior. D. trapezius.
(C)
correct.
To determine the potential consequence of therapy on the boy's tibia, we need to understand which muscles are directly affected by immobilization in a hard cast. The question provides four options: pectoralis major, gastrocnemius, serratus anterior, and trapezius.
To find the correct answer, we should understand the function of each muscle and think about whether immobilization of the tibia would have an impact on them.
A. Pectoralis major is a muscle located in the chest and is responsible for movements of the shoulder joint, such as arm flexion and adduction. Immobilization of the tibia would not directly affect this muscle, so it is unlikely to be the correct answer.
B. Serratus anterior is a muscle located on the side of the chest and plays a role in stabilizing the shoulder blade. Similar to the pectoralis major, immobilization of the tibia would not directly impact this muscle, making it an unlikely answer.
C. Gastrocnemius is a muscle located in the calf and is responsible for plantarflexion of the foot. Immobilization of the tibia would prevent normal movement of the ankle joint, thus potentially leading to atrophy (muscle wasting) of the gastrocnemius. This is a possible consequence of therapy, so it could be the correct answer.
D. Trapezius is a muscle located in the upper back and neck region and is responsible for movements of the shoulder blade and head. Immobilization of the tibia would not have a direct effect on this muscle, making it an unlikely answer.
Based on our analysis, the potential consequence of therapy on the boy's tibia that is most likely to occur is atrophy of the gastrocnemius (answer choice C).