After the plates have been secured, the surgeons then focus on attaching
the tendons. There are a number of tendons that are of concern when
doing a hand transplant. First of all, the tendons of the fingers need
to be attached to their corresponding tendon or muscle. There are four
extensor digitorum tendons coming from the all the digits except for
the thumb. They attach at one end to the middle phalanges and extend
into the forearm. In the forearm each attaches to the appropriate extensor
digitorum muscle. The pinky’s tendon attaches to a muscle called
the extensor digiti muscle. The surgeon takes extra care to attach the
tendons in the forearm to the appropriate tendon coming from the hand.
The surgeon can pull on the tendon to see which digit it moves. The
thumb also has a tendon called the extensor pollicis longus tendon which
attaches to the extensor pollicis longus muscle in the forearm and orginates
from the distal phalanges of the thumb.
All the tendons discussed above are on the dorsal surface. Another tendon
on the dorsal surface to take in consideration is the Extensor indicis
tendon which attaches to the pointer finger on one end and to the extensor
indicis muscle on the other end. Other tendons are attached to the palmer
side of the digits. These include the flexor digitorum superficialis tendons
that like, the extensor digitorum tendons, originate from the all the
fingers except for the thumb. Other tendons to be concerned about include
the palmaris longus tendon, flexor carpi radialis tendon (this tendon
originates from the lower phalanges of the index finger and extends to
the radius bone at the other end), and brachial radialis tendon. More
tendons include the extensor pollicis brevis tendon, which unlike the
pollicis longus tendon, originates from the second phalanges of the thumb;
the extensor carpi radialis longus tendon and extensor radialis brevis
tendon; the extensor and flexor carpi ulnaris tendons; and finally the
flexor digitorum profundus tendon. Finally depending on where the incision
is made, the surgeon should be wary that he may have to attach muscle
(for example the pronator quadratus muscle) instead of tendon.
Note on tendons: Knowing all the tendons is not necessary for
a full understanding of the surgery. The point is that this surgery is
extremely complex and tedious and requires a great deal of skill. When
looking at the name of the tendons, it helps to realize that flexor means
those tendons that help with flexing (as one can see these tendons will
lie on the palmar side of the hand) and extensor means those tendons that
help extend (which logically puts their location on the dorsal side of
the hand).
Anatomical Chart Company 2000, modified
