A 63-year-old man comes to the office due to right shoulder pain and weakness for the past 3 days. The patient was moving boxes at his home when he tripped, fell, and landed on his right shoulder. He has had partial relief of his pain from over-the-counter analgesics and stretching exercises, but the weakness has persisted. Vital signs are normal. The right shoulder has no visible deformity or bony tenderness. There is full passive motion of the right shoulder, but active motion is limited. There is significant weakness with resisted abduction of the right shoulder compared to the left side. After passive abduction of the right arm above the head, the patient is asked to slowly lower his arm; as he is lowering it below horizontal, the arm suddenly drops rapidly, in association with moderate, sharp pain. Sensation is intact. Which of the following is the most likely diagnosis in this patient?

Question

A 63-year-old man comes to the office due to right shoulder pain and weakness for the past 3 days.  The patient was moving boxes at his home when he tripped, fell, and landed on his right shoulder.  He has had partial relief of his pain from over-the-counter analgesics and stretching exercises, but the weakness has persisted.  Vital signs are normal.  The right shoulder has no visible deformity or bony tenderness.  There is full passive motion of the right shoulder, but active motion is limited.  There is significant weakness with resisted abduction of the right shoulder compared to the left side.  After passive abduction of the right arm above the head, the patient is asked to slowly lower his arm; as he is lowering it below horizontal, the arm suddenly drops rapidly, in association with moderate, sharp pain.  Sensation is intact.  Which of the following is the most likely diagnosis in this patient?

Quizplus · Accepted Answer

11ec25c8_d975_9044_bc81_2dbbbf4328e4_MD0003_00 This patient with impaired abduction at the shoulder following a fall has a rotator cuff tear. The rotator cuff is formed by the tendons of the supraspinatus, infraspinatus, teres minor, and subscapularis muscles. The supraspinatus is most commonly injured due to degeneration of the tendon with age and repeated ischemia induced by impingement between the humerus and the acromion during abduction. supraspinatus humerus and the acromion A complete supraspinatus tear causes weakness of abduction, which can be appreciated in the drop arm test. In this test, the patient's arm is abducted above the head and the patient is asked to lower the arm slowly. With a complete tear, the patient will be unable to lower the arm smoothly and it will drop rapidly around mid-descent. Although the supraspinatus is the primary muscle responsible for initiating the first 15 degrees of abduction, the loss of smooth adduction in the drop arm test typically occurs when the humerus is near the horizontal plane. MRI can confirm the diagnosis, and treatment usually requires surgery. (Choice A) Rupture of the tendon of the long head of the biceps occurs in forceful flexion of the arm. It produces sudden pain with an audible pop and a visible bulge ("Popeye sign") where the biceps muscle retracts into the medial arm. visible bulge (Choice B) Fracture of the surgical neck of the humerus may cause axillary nerve injury with paralysis of the deltoid and teres minor muscles and sensory loss over the lateral upper arm. However, patients typically have bony tenderness, swelling, ecchymosis, or crepitus over the fracture. In addition, the drop arm test is more reflective of supraspinatus function. Although the deltoid is responsible for shoulder abduction between 15-90 degrees, deltoid weakness is best appreciated at extreme extension rather than abduction. (Choice C) Injury to the long thoracic nerve causes weakness of the serratus anterior with impairment at extreme abduction (>90 degrees) due to inability to rotate the scapula upward. It is usually caused by penetrating trauma or medical/surgical procedures (eg, chest tube insertion). (Choice D) The lower (inferior) trunk of the brachial plexus originates from the C8 and T1 cervical roots and can be injured in sudden upward traction on the arm (Klumpke palsy). Muscles supplied by the ulnar nerve (eg, intrinsic muscles of the hand) are commonly affected, which results in weakness and atrophy of the hypothenar and interosseous muscles and "claw hand" deformity. Educational objective: Rotator cuff tears cause pain and weakness at the shoulder. With the arm abducted over the head, the patient may be unable to lower the arm smoothly (drop arm test). An MRI scan can confirm the diagnosis.

A 63-Year-Old Man Comes to the Office Due to Right