I saw a funny thing on the subway this morning. A woman was wiggling her fingers and talking out loud. Now, in New York City, that really isn't so unusual but what she was saying caught my attention. She was memorizing the anatomy of just the tendons that pull the fingers back. It caught my attention so I'm checking your website for a little more about this myself. What should I look for?
You may want to start with our publication A Patient's Guide to Hand Anatomy. You may find other Patient Guide topics of interest in the section on hand. We also recently reported on a review article just on the extensor tendons of the hand from The University of Illinois at Chicago Department of Orthopaedic Surgery. The extensor tendons are the ones that lift the fingers off the table when the hand is resting palm down (or pull the fingers back as your subway companion described it).
Although the review of hand extensors is for hand surgeons, the information would benefit anyone studying hand anatomy. Injuries of the hand are very common. Surgeons know how complex and delicate the anatomic structures of the hand are. They understand the need for very careful surgical technique when repairing, reconstructing, transferring, or grafting a tendon.
In the article just mentioned, there is a review the anatomy of each extensor tendon and discuss the complexities of surgery for tendon transfers. Included in the discussion are the following tendons: extensor digitorum communis, extensor indicis proprius, extensor digiti minimi, extensor proprius indicis, extensor digitorum brevis manus, extensor pollicus brevis, extensor pollicis longus, and extensor medii proprius.
Tendon transfer refers to taking one tendon and moving it to function in place of another. This is done most often when a tendon has been injured, the nerve to the tendon has been damaged, or there is a defect of the tendon from rheumatoid arthritis. But tendon transfers (or using tendon as a graft) are not as simple as they sound.
For example, sometimes a tendon originates (or begins) in a slightly different place than expected. Most tendons start from an attachment directly to the bone. But in some cases, the insertion point could be a ligament instead of the bone. Or the origination could be from the soft tissue over the bone.
If even a single tendon slip is taken from the wrong tendon, it can affect the movement and strength of the finger and/or hand. Likewise, if the surgeon chooses a weaker tendon for a transfer to a stronger tendon that has been injured, the result can be a significant loss of hand function. In yet another example, the authors point how the extensor indicis proprius (EIP) has many connections to the extensor digitorum communis (EDC). The connection between these two tendons must be carefully cut to avoid losing the benefit of the EIP as a tendon transfer.
There are also thin bands of tissue that connect the extensor digitorum communis (EDC) tendons. These are called the juncturae tendinum. The full function of the juncturae tendinum is not completely understood but it is clear that the anatomy can be quite different from one person to another. The authors provide a detailed description of this anatomic structure and description of what is known so far about how it works. Even rare anomalies (differences or variations) of the juncturae tendinum anatomy are important for the hand surgeon to be aware of.
So you can see even in just this brief review that there are many extensor tendons. They are an important part of the complex and delicate structure we call the hand. Without the fingers (and the movement they provide), performing even the simplest of daily activities can be difficult, if not impossible. And this is just one feature of the amazing hand!
Kevin Chen, et al. Extensors of the Hand. In Current Orthopaedic Practice. March/April 2013. Vol. 24. No. 2. Pp. 189-196.
*Disclaimer:* The information contained herein is compiled from a variety of sources. It may not be complete or timely. It does not cover all diseases, physical conditions, ailments or treatments. The information should NOT be used in place of visit with your healthcare provider, nor should you disregard the advice of your health care provider because of any information you read in this topic.