A former classmate of mine at Washington University, David Bergeson, did his doctoral dissertation on "The positional behavior and prehensile tail use of Alouatta palliata, Ateles geoffroyi, and Cebus capucinus (1996)". He also had a chapter in the 1998 edited volume "Primate Locomotion:Recent Advances" (Strasser, E., Fleagle, J., Rosenberger, A.L., McHenry, H., Eds.), Springer, entitled: "Patterns of Suspensory Feeding in Alouatta palliata, Ateles geoffroyi, and Cebus capucinus" (pp 45-60). You can access the abstract and chapter preview, as well as David's list of references at: http://link.springer.com/chapter/10.1007/978-1-4899-0092-0_3 .
In particular, his reference list includes the following source that sounds like it would be of use to you:
Lemelin P (1995) Comparative and functional myology of the prehensile tail in New World monkeys. J. Morph. 224:1–18.
German-US primatologist Friderun Ankel (author of Primate Anatomy by Academic Press) has worked on the anatomy of the platyrrhine tail in the 60s. Unfortunately (for non.Germans), all or most of her work is in German. If you have someone to help you with translation, I could try to get PDF files from our university library. Best, Eckhard
You may find anything interesting in the pertinent volume of "Primates: Comparative Anatomy and Taxonomy", by Osman Hill. They are amazing volumes of the complete understanding of primates, including cell and tissues, muscles, organs, systems, endocrinilogy, taxonomy and even ecology. A complete compendium..
I have Hill's book and, surprisingly, the description of this anatomical aspect is very superficial. Fortunately, the references suggested by the other colleagues have already fulfilled my needs.