WBR0496
| Author | [[PageAuthor::William J Gibson (Reviewed by Serge Korjian and Yazan Daaboul, M.D.)]] |
|---|---|
| Exam Type | ExamType::USMLE Step 1 |
| Main Category | MainCategory::Anatomy |
| Sub Category | SubCategory::Musculoskeletal/Rheumatology, SubCategory::General Principles |
| Prompt | [[Prompt::A 17-year-old man is brought to the emergency department for right arm trauma following an injury during a lacrosse game. The patient reports 9/10 pain for which he took ibuprofen en route to the hospital. An X-ray of the right arm is shown below. Which of the following is most likely to be impaired in this patient?
|
| Answer A | AnswerA::Thumb adduction |
| Answer A Explanation | AnswerAExp::The ulnar nerve is responsible for adduction of the thumb. |
| Answer B | AnswerB::Forearm pronation |
| Answer B Explanation | AnswerBExp::The radial nerve is responsible for innervating the supinators of the forearm. |
| Answer C | AnswerC::Arm abduction beyond 15 degrees |
| Answer C Explanation | AnswerCExp::The deltoid muscle is responsible for arm abduction beyond 15 degrees. The deltoid is innervated by the axillary nerve, which is typically affected by fractures at the surgical neck of the humerus. |
| Answer D | AnswerD::Wrist extension |
| Answer D Explanation | AnswerDExp::The radial nerve is responsible for innervating the extensors of the wrist. The radial nerve is damaged by midshaft fractures of the humerus such as the one pictured above. |
| Answer E | AnswerE::Wrist flexion |
| Answer E Explanation | AnswerEExp::The median and ulnar nerves are responsible for wrist flexion. |
| Right Answer | RightAnswer::D |
| Explanation | [[Explanation::The above image demonstrates a classical mid-shaft fracture of the humerus. Patients present with This injury is associated with radial nerve damage. The radial nerve is responsible for the innervation of the extensors of the wrist. Educational Objective: The radial nerve is responsible for innervating the extensors of the wrist. The radial nerve is damaged by midshaft fractures of the humerus such as the one pictured above. |
| Approved | Approved::Yes |
| Keyword | WBRKeyword::Arm, WBRKeyword::Humerus, WBRKeyword::Fracture, WBRKeyword::Nerve, WBRKeyword::Radial Nerve, WBRKeyword::Brachial, WBRKeyword::Brachial plexus, WBRKeyword::Mid-shaft |
| Linked Question | Linked:: |
| Order in Linked Questions | LinkedOrder:: |
