This is not a standard sleeve length. In fact, I found only one reference in textiles and/or clothing that used the phrase. Since this is a precise measurement, I would do a direct translation.

I would also like to point out that there is a 7/8 sleeve, which reaches just above the wrist, and I'm wondering if this is an error in that what they meant to say was a seven-eighths sleeve.

References:
• Similarly, one may not superficially alter one's clothing in order to create a new type of clothing.
i. For example, one may not cut a strip off of one's cloak to create the new item type "Nine-tenths-length Cloak."
http://elothtes.pbwiki.com/Law 63

# Manche longue : manche descendant jusqu'au poignet ;
# Manche 3/4 : manche s'arrêtant en dessous du coude ;
# Manche 7/8 : manche s'arrêtant un peu au dessus du poignet ;
http://fr.wikipedia.org/wiki/Manche_(vêtement)

coat length
finger-tip
five-eighths
full-length
hip-length
seven-eighths
three-quarter
waist-length
wrist-length

SLEEVES…
saddle shoulder sleeve
set-in sleeve
shoulder-puff sleeve
sleevelet
three-quarter sleeve
trunk sleeve
undersleeve
virago sleeve
winged sleeve
http://circe.slis.kent.edu/mzeng/bin/structureterm.html


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Note added at 3 hrs (2008-09-30 16:36:38 GMT)
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In looking back over the question, I realized that you had included the 7/8 length in your question. So 9/10 is not an error. I finally found the 9/10 sleeve by switching to numbers.

9/10 length sleeve style, not full length sleeve.
http://www.fanplusfriend.com/servlet/the-337/Elegant-Goth-Go...

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Note added at 22 hrs (2008-10-01 11:54:52 GMT) Post-grading
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You're welcome, Robintech, and thank you! :-)