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Now we'll go to the skeleton of the hand, it's formed of three groups of bones, the
carpal bones, the metacarpal bones and the phalanges, which forms the skeleton of the
fingers. The, carpal bones are short bones, which are 8 in number in a form of two rows,
a proximal row and a distal row. The, metacarpal bones are 5. from the 1st of the thumb then
the 2nd, the 3rd, the 4th and the 5th. The, 1st metacarpal bone is very short and wide,
the last metacarpal bone which is number 5 is thin and long . So, these are the metacarpal
bones, each metacarpal bone has a base near the metacarpal bones and a head that articulates
with the proximal phalanx. The, head is convex and articulates with the lower concave surface
of the proximal phalanx to form the metacarpophalangeal joint, which is a biaxial condyloid joint,
because the movements here will be flexion, extension, adduction, and abduction. So, this
is a biaxial joint of the condyloid variety and the movements allowed are flexion, extension,
adduction and abduction. Again, each metacarpal bone has a shaft, a base and a head. The head
articulates with the proximal phalanx to form the metacarpophalangeal joint. In each finger,
we have 3 phalanges, proximal, middle and distal, except the thumb which has only two
phalanges, proximal and distal. Between, the phalanges there will be the interphalangeal
joint. The, articular surface of the interphalangeal joint is trochlear in shape and therefore
it is a uniaxial hench, which allows only flexion and extension "flexion and extension".
Now, when we go to the carpal bones, the first row in the carpal bones is formed of 4 bones,
from lateral to medial 1,2,3,4 this is the proximal row. The, most lateral bone is called
the scaphoid bone, which articulates with the "Radius", and it has a special tubercle
which is called the tubercle of the scaphoid. Next, to it there is the lunate bone, and
the most medial one is the triquetrum. So, the proximal row is formed of the scaphoid, lunate and triquetrum. And,
the triquetrum articulates anteriorly with the pisiform bone which is actually a sesamoid
bone developing inside the tendon of the flexor carpi ulnaris, this is the pisiform bone.
So, the proximal row has 3 true carpal bones, which are the scaphoid, the lunate and the
triquetrum and 1 sesamoid bone, which is a pisiform bone, which develops inside the tendon
of the flexor carpi ulnaris. Now, when we go the distal row from medial to lateral,
the 1st and the most lateral is the trapezium and it has a special character, which is the
presence of the crest here. This, crest is related to the tendon of the flexor carpi
radialis in its way to become inserted into the base of the 2nd and 3rd metacarpal bone.
Next, to the trapezium, we'll have the trapezoid and medial to the trapezoid we'll have the
capitate, which is characterized by the presence of a head, "capitate that has a Capote". And,
most medial there will be the hamate bone, which has a special character, which is the
presence of a "hook" like process. (So, to recapitulate), we have the trapezium very
lateral in the distal row with the special character which is the crest, we have the
trapezoid, we have the capitate with a special character which is the presence of a head.
And, very medial we'll have the hamate with a special character which is the hook of hamate.
So, if we come to see the most anterior prominent parts, we'll have the tubercle of scaphoid
is prominent, we'll have the crest of trapezium distal to it, this is the lateral attachment
of the flexor retinaculum. The, most prominent medially, we'll have the pisiform and distal
to it we have the hook of hamate, this will be the medial attachment of the flexor retinaculum.
Therefore, the flexor retinaculum extends between these two bony prominence, the two
lateral bony prominence are the tubercle of scaphoid and crest of trapezium laterally
and then it goes to become attached to the pisiform and hook of hamate. The space of
course deep to the retinaculum, between the retinaculum and the carpal bones, called the
carpal tunnels. If this the retinaculum like this, the space between the retinaculum and
the carpal bones is called the carpal tunnel and it allows the passage of the medial nerve
to the hand with their flexor tendons and their sheath (synovial sheath), and here the
medial nerve may be compressed, producing what is called as the carpal tunnel syndrome.
Of course, the palmaris longus muscle passes superficial to the flexor retinaculum, but
the other flexors pass deep to it. So, through the retinaculum, the medial nerve passes,
the flexors except the palmaris longus together with the synovial sheath of the tendons and
here, the medial nerve may be compressed to produce the carpal tunnel syndrome