1 Hand & foot
د . محمد الحيدري
تسنيم قشوع & اسماء ابو راس
بسم هللا الرحمن الرحيم
Hand and Foot
These two functional parts of the limbs have many
similarities between them, in that they have a composite
of bone which is arranged in a
manner in which large set of
bone will articulate with two
bones of the forearm or the leg. These are the
carpal bones in case of the hand and the
tarsal bones in case of the foot.
The majority of these irregularly shaped bones
have main joints between them allowing a
certain movement so that coordination of both
carpus and tarsus will allow the functional
part distally to perform its movement
There are 8 carpal bones and 7 tarsal bones
In addition, a main difference between them,
is that carpal bones are arranged into two rows
, proximal and distal with a slight concavity
on the flexor side and a slight convexity on
the dorsal side. In case of the foot, because
this functional part, is required for power
movement; for the grip of the ground. The
arrangement of these bones will take the form
of arch and this is a very important feature of
the foot. Classically, we divide the whole foot into 2 longitudinal arches,
one of them toward the medial side: called medial longitudinal arch and
the other is on the lateral side called: the lateral longitudinal arch.
*Tarsus (skeleton), the skeletal region between the tibia and fibula and the
**In tetrapods, the carpals is the sole cluster of the bones in the wrist between the
radius and ulna and the metacarpus
***The arches of the foot are formed by the tarsal and metatarsal bones and,
strengthened by ligaments and tendons, allow the foot to support the weight of the
body in the erect posture with the least weight.
These are formed by the bones:calcaneus, navicular medial cuneiform
and first metatarsal of the big toe.
Phalanges are not included in the arches and if you stand quietly and put
your feet on the ground, your pressure is transformed to the foot but your
toes can move freely. That means the pressure points are not at the toes.
The pressure is at the tips of metatarsal bones.
There is a third arch found in between metatarsal arches\ bones , that is a
transverse metatarsal arch/ transverse plantar arch.
This too allows the foot to have grip points.
In case of the hand, carpal bones have a slight convexity &concavity.
They are slightly convex at the dorsal aspect and slightly concave at the
ventral, flexor or anterior aspect.
This is what is called the carpal tunnel. It is a tunnel; a canal through
which all these large numbers of tendons of muscles of the forearm
should pass to approach their destinations in the fingers and the thumb.
In case of the foot, similarly, there are tunnels that we see them behind
medial malleolus and anteriorly in front of the extensor groups and
posteriorly behind the flexor groups of the toes.
Similar tunnels are present but they are not as clear as in case of the hand,
because the hand has more freedom of movement refers to their skeleton.
One other thing to remember about these movements is that metacarpal
phalangeal joints which allow the movement of the fingers have more
freedom of movement as you go towards the little finger. So, the little
finger has more freedom of movement than the ring finger than the
middle finger than the index.
Although all of them have free movement, the freedom goes towards the
little finger because the fine movement that is the fine grip is strongest
between the thumb and index. it is weakest between the thumb and the
In other words, as an example of fine precise movement, when we hold
the needle trying to sew something or the pen, the best precise grip for the
needle is between the thumb and index, it is the grip we best control the
This is in regard to the small joints between carpal and metacarpal joints
called intercarpal joints or carpometacarpal joints.
At this region where the carpal bones are present; large no. of tendons,
vessels and nerves, will pass from the region of the forearm into the hand.
These need to be guarded (from behind and in front), so there is a very
tough thickening of the deep fascia of the whole region which surrounds
all these tendons of muscles, nerves and vessels, we call it retinaculum.
And they are named according to their position. So, for example if we
look at the hand (diagram); in green drawn a thickening of the deep fascia
on the flexor side and because of being in front we call it flexor
retinaculum. Similarly, on the back there is another thickening of the
deep fascia which also protect and guide the extensor compartment of the
forearm into the hand , called extensor retinaculum.
In the foot there are 3 regions of retinaculum.
This is how these tendons are controlled and guided toward their
Why is this modification present?
Imagine if we put them in single compartment in a strong contraction ,all
of them will be gathered in the middle. So the power of movement won't
be as strong as required. so the retinaculum is present to guide the tendon
toward its destination.
There are other problems which we will have in nerves, we see that when
pressure is increased, called carpal tunnel syndrome(to be discussed
later in the discussions).
Talking about the flexor retinaculum, which is actually guiding or
pressing over the tendons passing through the forearm into the hand, it is
further dividing itself into 2 other compartments:
A superficial one, and a deep one. The deeper is closer to the carpal
bones. In each one of these compartments, there are 4 tendons passing
regularly in an organized manner towards the 4 fingers.
As this is in the anterior, flexor part, these superficial and deep are
actually the tendons of the superficial flexor or the profundus.
You know, we have flexor digitorum superficialis and flexor digitorum
profundus. Profundus refers to the deeper(in the deep compartment of
This is the central compartment of retinacula.
Lingual examination of the dimensions of this retinacula: if you flex your
hand toward the forehand, you will see 2 creases, one by one. The
proximal is the beginning of retinacula and the dimension of retinacula is
distal to the distal crease, it is hitting by 2 bulks of muscles. One of them
is at the side of the thumb called thenar eminence or thenar muscles this
is composed of 4 small muscles of the thumb.
The other bulk is smaller and located at the base of the little finger, called
So these are 2 projections and the retinacula passes from the proximal
crease of the forearm to the distal crease underneath these 2 bulks of
As a result of folding of the deep fascia, 2 creases are formed in the palm,
and another 2 in the wrist; one by one very close to each other.
Down syndrome:is a congenital abnormality, having one crease only in
the palm is a diagnostic feature.
The retinaculum is just a channel for the tendons. More deeply, it will
be fused with certain sheath covering the tendon which minimizes the
friction, called synovial sheath, for the tendons. Each one is directed to
different digit or different finger.
Retinacula is a thickening / second membranous. So in surgery, it can be
opened/slit when there is pressure over the nerve. so, it is an extension in
width from the proximal crease and distal to the distal crease; side by side
laterally, the retinacula is hidden underneath these 2 bulks of muscles.one
at the basal part of thumb and the other at the base of little finger; called
thenar eminence and hypothenar eminence respectively.
This is the dimension of flexor retinaculum. We have seen that 2
compartments are also found underneath it. One of them is for the 4
tendons of flexor digitorum superficialis and the other deep one is for the
4 tendons of flexor digitorum profundus.
In addition to these, to the thumb side; that is laterally, there is another
flexor as compared to the flexors of the fingers: superficialis and
profundus. That is flexor pollicis longus, means the long flexor of the
All of them are underneath the flexer retinaculum and with them there is
the large nerve which is the median nerve a clinical example of this:
during pregnancy in females they will retain some water so there is an
excessive fluid which might cause a compression in this area especially in
the morning then they start to complain of pain and dullness in the finger
( because of the compression of this nerve ) and this will be so severe that
some times we require to relieve and open some gates for those important
tendons so they cut through the retinaculum which is tough (yemazquha)
, that will not affect the function of the hand because you will cut in
certain regions .
So the major contents are :
The large long powerfull flexors for the whole fingers ( flexor pollicis
longus , flexor digitorum superficialis flexor and digitorum profundus )
plus the median nerve but we know that at the anterior side of the hand
we have tow nerves not only the median but the ulnar nerve ( this nerve
supplies the fifth and half of the ring finger the other fingers are supplied
by the median ) also , but this nerve will enter the hand superficial (
above the retinaculum ) , so when the retinaculum become tight then
there will be a pressure over the median nerve and the patient will come
and complain of the three fingers but the other fingers are normal .
On the dorsal side ( the extensor compartment ) another retinaculum is
present and there is a large number of tendons and there is the radial
nerve and it's branches . the extensor retinaculum is divided by
thickenings in to six compartments ( by five septa ) .
Usually most of the branches of the radial nerve are superficial to the
retinaculum ,so they are not affected if there is a pressure on the
But remember that because of the convexity of the carpal bones there is
no space or tunnel so there is a very little chance for a fluid to collect
in the extensor side , so carpal tunnel syndrome is a case that affect the
flexor retinaculum ( so we are not worried of the radial nerve and it's
branches or the tendons passing in this compartment )
The largest one ( the central one ) of those compartments is the one that
contain tendons of the extensor digitorum .
In the extensor side the index is supplied by special muscle (in addition to
extensor digitorum) which is the extensor indicis that increase the power
of the extensor digitorum to the index finger .
In the flexor side we have two flexors for the digits( flexor digitorum
superficialis flexor, digitorum profundus ) , in the extensor side we have
one extensor for the digits ( extensor digitorum ) , so the flexion of the
digits is more powerful than the extension .
The foot retinacula :
Retinacula is present also in the foot for the same purpose (to guide the
tendons of the muscles to their destination and keep them there). we can
see that the retinacula is located anteriorly infront of the joint and this is
what is called the extensor retinaculum , also there is another one which
extend behind the medial malleolus to the calcaneus
(keeps the tendons of the medial side muscles ) and
this is the flexor retinaculum , and the last one is
the peroneal retinacula which extends from the
lateral malleolus to the calcaneus and keeps the
tendons of the peroneal longus and brevis muscles (
responsible about the eversion of the foot ) .
The foot is making an angle with the leg ( not like the hand which is
straight( no angle ) with the forearm ) so there so we have superior and
inferior retinacula ( this is the major difference between the retinacula
of the foot and the arm ) .
The problems in the foot are very rare because there is no chances of
trapment as we see in the flexor compartment in the hand .
The knee joint
In this diagram we are looking to the foot after the
removal of the tibia , so we are looking to the talus
( it has a convex upper surface , and the tibia has a
concave upper surface so the tibia is located over
The ankle joint is a very complex joint the main
bone that makes the ankle joint is the talus it
articulate with the tibia superiorly( the talotibial
joint ) and the calcaneus inferiorly that ( subtalar
or the talocalcaneal ) , those two joints form the
ankle joint .
The flexion(plantar flexion) and the
extension(dorsi flexion) occur at the talotibial joint
, the eversion and the inversion occur at the
talocalcaneal joint .
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