For a long time I've been aware of a deformity in both of my 5th fingers which creates some unique problems (see below for pictures). One specific problem it creates is that it's difficult for me to press a white key in-between black keys with my 5th finger while my thumb is also on a black key (due to the curvature in my 5th fingers, they simply can't fit between the black keys sometimes without also pressing the nearest black key to the outside of my 5th finger).

A few pictures of my hand in different positions (I'm using an electronic keyboard, the distance between the keys is slightly less than that of a normal acoustic piano): http://i818.photobucket.com/albums/zz108/mrferguson12/Mobile%20Uploads/010813110616.jpg
http://s818.beta.photobucket.com/user/mrferguson12/media/Mobile%20Uploads/010813111038.jpg.html
http://i818.photobucket.com/albums/zz108/mrferguson12/Mobile%20Uploads/010813110949.jpg
Often times when I practice, my other fingers seem be working just fine and comfortably, but then it feels like my 5th fingers just "don't fit". I've also noticed myself using ulnar deviation, instead of a more 5th finger-oriented "natural" position which is made uncomfortable by the deformity. Does anyone else have a similar challenge with finger abnormalities? Please share

I'm not convinced you've got a finger 'deformity'. I also play with my little (i.e. 5th) fingers bent (flexed) at the distal interphalangeal joints (DIPJ) like in your photos, and very rarely, I might catch my nail in the gaps between keys when the composers (who shall remain nameless, to protect the guilty ) are rather inconsiderate of normal human anatomy (I consider myself normal, obviously) and delight in getting pianists' fingers in twists. If their music weren't so interesting, I'd just give it up as bad job, but sometimes, a man's just gotta do what a man's gotta do, and get on with it, and find solutions by trying different fingerings, redistributing notes etc.

In any case, I consider my little fingers to be more 'normal' than Horowitz's, whose 5th fingers remain curled up like snakes, only to uncurl and strike out when required, also like, er, rattlers.....

Since you say "for a long time" rather than "since birth," I too wonder whether this is really a deformity. However, if you are not able to move the 5th fingers as you want, it could very well be a dystonia induced by harmful movements such as excessive stretching or curling.

I had a different 5th finger problem, involuntary extension aggravated by years of playing the flute with flattened, outstretched 5th fingers (not good for you). I thought I had abnormal fingers that wouldn't move like other people's.

After retraining in ergonomic technique, my 5th fingers work just fine. It took some time to get to that point, but it was quite a revelation.

It sounds as if the 5th finger problem could be leading you into other technical problems also. I think it would be good to consult a teacher who is knowledgeable about dealing with playing-related injuries (Taubman is best IMO).

I don't see anything wrong with your finger?

Man that's freaky.....you should join the Circus or cut that thing off or something

I don't see anything unusual, either.

From your photographs it would seem your hands which are on the small side. As a 5'10" man I can easilly play an octive with either 3rd: 4th: or 5th fingers, but I can not play a nineth.
I guess we all made differently.

Wow! That's quite strange, sounds like small hand but good stretch? I can reach most 10ths but I wouldn't call octave with 3rd finger "easy".

It appears that you are playing an electronic keyboard with "organ style" keys. Does your little finger get hung in, or between, the edge of the white keys? If so, "box style" keys might help.

Lord deliver me...I would rather have a broken leg or a heart attack than have anything wrong with my hand(s)... I can always work with a broken leg...

The finger seems fine, but is there any way you can post a video of you playing? That would really help to see if there is an issue - maybe something that demonstrates the kinds of issues you are having. Everyone's hands are slightly different and so certain fingerings work better than others to play a C# diminished chord for example.

Also, do you experience any pain or fatigue while playing?