The "Distortions of the Hand" section of many books (including FA) confuse many students, not only because of the inconsistencies in naming, but also because there's more than one way to get each hand distortion!
I'll try to explain the differences between the two, but it might be a bit wordy, so bear with me. Firstly, both the Pope's Blessing and the Claw Hand can each be caused by
two different etiologies. The problem with seeing a static picture, as opposed to witnessing it in a real patient is that you cannot differentiate between either etiology at first glance. So here's what you first do, find out if it's extension or flexion that's causing the distortion of the hand.
For Pope's Blessing:
1. Patient gets PB upon trying to straighten their fingers (i.e.
extension of the fingers).
-This is due to a
Distal Ulnar Nerve Lesion, which makes it impossible for the patient to
extend their 4th and 5th digits.
2. Patient gets PB upon trying to make a fist (i.e.
flexion of the fingers).
-This is due to a
Median Nerve Lesion, which makes it impossible for the patient to
flex their 2nd and 3rd digits.
That's why it's so difficult (and oftentimes confusing) to memorize these disorders, as there's two different ways of getting the same hand distortion.
Okay, now let's do Claw Hand. You notice that I didn't call it, "Median Claw?" It's because that name is inconsistent, depending on etiology. You'll soon see why.
For Claw Hand:
1. Patient gets CH upon trying to straighten their fingers (i.e.
extension of the fingers).
-In other words, the patient finds that they can't
extend their 2nd and 3rd digits.
-This is due to a
Distal Median Nerve Lesion.
2. Patient gets CH upon trying to make a fist (i.e.
flexion of the fingers).
-In other words, the patient finds that they can't
flex their 4th and 5th digits.
-This is due to a
Proximal Ulnar Nerve Lesion.
So now you see that there's two different ways to get the "Pope's Blessing/Hand of Benediction," and two different ways to get the "Claw Hand." I hope this helped!
If you're more of a visual learner, try this guy's guide:
http://stepjourney.wordpress.com/2010/04/06/the-infamous-popes-blessing/
