A 30-year-old female patient comes to the ER after falling a short flight of stairs. Physical exam shows BP of 128/75, temperature of 98.5 °F, and with a pulse of 69 bpm. While taking her history she states her last menstrual period was 15 days ago. She has no significant medical history. She has minor bruising on both of her hands as she landed on them to break her fall at the occurrence of the accident. The patient states that her right hand feels weak, specifically her thumb. Pinprick test shows weak sensation around the right palmer aspect of thumb and index finger. If x-ray scans were conducted for diagnosis, which bone would show significance in damage?
Answer and Explanation
The correct answer is the lunate bone (B).
The lunate bone dislocation in an occurrence of trauma can affect the median nerve. It presents with weakness or loss of function of the thenar eminence innervated by the median nerve. The thenar eminence is the group of muscles on the palm of the hand, at the base of the thumb. Loss of innervation of by the median nerve will lead to atrophy of the thenar eminence.
The median nerve damage presents with the little to complete loss of sensation of the cutaneous area innervated by the median nerve; the palmer aspects of the 1st to the 3rd digits. The median nerve also innervates the cutaneous aspect of the distal half of the 2nd, 3rd, and the 4½ digits on the dorsal side.
A) The ulnar nerve would be affected if the hamate bone was damaged. It would be presented as claw hand of the 4th and 5th digits. Also the dorsal and palmer sensational aspects to the 4th and 5th digits would be weakened or lost as well.
Answers C, D, E) Dislocation of the trapezium, trapezoid, and pisiform bones would not cause significant damage to the median nerve unlike the lunate bone.
What to Take Home
In a trauma that involves the hand, if the dislocation of the lunate occurs then it will lead to median nerve damage. The affected nerve will lead to loss of sensation in the first three digits of the hand, along with loss of sensation and motor function of the thenar eminence. Loss of the motor innervation of the thenar eminence may also lead to atrophy of the thenar eminence.
The subject of Anatomy, to me, seems very boring, dry, and sometimes hard because of the boring nature of the subject. Unfortunately, the question banks don’t really give enough images to fully grasp the anatomical figures in the questions. You probably heard that Anatomy subject is low-yield, but don’t count on it. The Anatomy subject should be given a good amount of attention, especially CT scans. Neuroanatomy is very high-yield and you should be familiar with the overall picture of the brain. Questions can give you a scenario of a dysfunction of a patient, and they may ask you which part of the brain contains the nucleus that is damaged that caused the dysfunction.
3D Human Anatomy Atlas 2 by Visible Body; it is a software for both PC and Mac. It’s also an app which is also available for iPhone and iPad users on the Apple App Store
and Android users on Google Play store
.. The App is incredible and it’s one of the top-rated medical app on the Apple App Store
. If you don’t have a tablet, you can still get the computer-based software; however, navigating via a tablet makes things more efficient. The software allows you to rotate the anatomical figures in 360 degrees position so you can see the anatomical figure in all angles. Also if you have an organ or tissue that is blocking the view of your target anatomical structures then you can either fade is or hide it from view. The app also allows you to take screen capture and share it with others. I used the software to draw out the figure for a previous post, Adrenal Glands – First Aid for the USMLE Step 1
. If you have the iPad with retina display, the app takes advantage of the sharp display and shows it with incredible precision. The app costs about $40 for the iPad; I’m not sure about the prices for other platforms. When I bought a MacBook Pro with a student discount, I was given a $100 Apple gift card, which I used to buy the app.
Anyways, studying anatomy just from pictures is hard, and I prefer to study smart not hard so, I invested the money in getting what I need to study better. I recommend 3D Human Anatomy Atlas 2 by Visible Body for everybody, especially for people who are visually oriented learners. This study tool worked for me, but I can’t guarantee that it’ll work for you, but try it and see.