Question 136

Question:

A 30-year-old man sustains significant shoulder trauma during a motor vehicle accident. Other than ligamentous damage, x-ray shows only an avulsion fracture of the tip of the coracoid process. Which shoulder movement would be expected to be most impaired?

Correct Answer: D.  Flexion

The coracobrachialis and the short head of the biceps brachii originate at the coracoid process. An avulsion fracture (where a small piece of bone is broken off while still attached to tendon or ligament – in this case tendon) of the coracoid process would prevent these muscles from exertion their main action at the shoulder joint, which is flexion (D). Other muscles responsible for shoulder flexion include the anterior deltoid and the pectoralis major. Supraspinatus and deltoid are responsible for shoulder abduction (A). Shoulder extension (B) is mostly due to the latissimus dorsi and the posterior deltoid. External rotation (C) is mostly due to teres minor, infraspinatus, and posterior deltoid. Inversion (E) is not an action that occurs at the shoulder (it occurs in the ankle).
Memorizing all of these actions is unnecessary – knowing the location of the coracoid process (palpable on exam near the deltopectoral triangle) is sufficient in this case. The question stem is asking for the effect on the shoulder, so (A), (B), and (C) would not be possible given the anterior location of the coracoid process in relation to the humerus.
Shoulder motion can be confusing:
Shoulder flexion is the motion where the arm is raised up (toward superior direction, as in lifting a child).
Adduction is always a motion towards the body, shoulder adduction occurs when you slapping someone across the face.
Abduction is moving away from the body. shoulder abduction is opposite of above – you went to backslap that person with the same hand…