Foot+-+Lecture+Notes

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Foot

=**Foot - Lecture Notes**=

[|Lecture 1] [|Lecture 2]



**Lecture 1**
The talis bone is closely associated with the calcaneus bone (which forms the heel). The next two bones are the navicular and cuboid bones plus the three cuneiform bones (medial, intermediate, and lateral) which together from the tarsal bones.

The big toe, like the thumb only has a proximal and distal phalanges.

Bony architecture has been modified to be weight bearing. There is a dramatic medial longitudinal arch and a smaller lateral longitudinal arch as well as a transverse arch.



**Lecture 2**
The keystone bone that maintains the integrity of the foot is the talis. The arrangement of the bones (keystone), intrinsic muscles of the foot (tie beam), extrinsic foot muscles in the leg (suspension bridge), and presence of powerful ligaments (staples) helps maintain the integrity of the foot.

People with fallen arches can be due to any deficiencies of structures maintaining foot integrity.

Inversion and eversion occurs between the talis and the calcaneous joint.

The tendons of extensor digitorum longus, tibialis anterior, and extensor hallucis longus are on the dorsum of the foot. Because these tendons cross the ankle, the muscles will also dorsiflex. Because the dorsum of the foot has very thin skin, the tendons are very conspicuous.

The superficial fibular nerve goes cutaneous on the anterior lateral leg and goes down to give sensory innervation to most of the foot. The deep fibular nerve gives sensory innervation to just the adjacent skin between toes I and II.

The companion of the deep fibular nerve is the anterior tibial artery; when it crosses the ankle, it becomes the dorsal artery of the foot (dorsalis pedis artery). The deep fibular nerve and dorsal artery of the foot lie between extensor hallucis longus and extensor digitorum longus, and a pulse can be felt here.

Extensor digitorum brevis originates on the calcaneus and gives tendons to toes II, III, and IV. It skips toe V. Sometimes it will give a tendon to toe I and sometimes called extensor digitorum hallicus. Its innervated by the deep fibular nerve.

When people drop things on their foot, they often damage extensor digitorum brevis because of its superficial position.

The dorsal artery of the foot forms a dorsal arch.

The long saphenous vein universally passes anterior to the medial malleolus. Short saphenous vein passes laterally.

The dorsal artery of the foot gives off a branch between metacarpal I and II which goes deep and supplies the plantar surface of the foot, establishing collateral circulation. This is the deep plantar artery. There are interosseous muscles between the metacarpal.

Skin of the plantar surface is very thick. The superficial fascia is thick and has lots of fibrous tissue that splits the plantar surface into compartments full of fat that acts as shock absorbers.

The deep fascia is the plantar aponeurosis which starts on calcaneous and goes to each toe. Very important for protection of deeper muscles and major vessels and nerves.

On the medial side and lateral sides of the plantar aponeurosis are septa that go down and separate the foot into medial, middle and lateral compartments which connect with the compartments of the leg. Infections can spread up to compartments of the leg but not across compartments.

Three muscles of layer 1.

Muscle in the midline is flexor digitorum brevis, going from calcaneous and sending tendons to the five toes. Abductors hallicus to the big toe and abductor digity minimi to toe V. Both muscles go from the calcaneous on the medial and lateral sides respectively, attaching to their respective metacarpals. Each are also associated with the medial and lateral arches, respectively. These muscles are large fleshy muscles important in weight bearing and foot integrity rather than abducting in humans.

Muscles of layer 2.

Tendon of flexor hallicus longus to toe I, flexor digitorum longus to toe II-V come from the leg and are extrinsic muscles.

The quadratus plantae and the 4 lumbricals muscles. The lumbricals take origin from flexor digitorum longus. Lumbrical muscles help in extension of the interphalangeal joints to allow the toes to grip the floor by keeping the interphalagneal joints extended during toe flexion.

Quadratus plantae inserts to the tendon of flexor digitorum longus. Because contraction of flexor digitorum longus will tend to plantarflex, invert the foot and flex the toes, quadratus plantae redirects the force from the tendon of flexor digitorum longus to allow flexion of the toes without inverting the foot.

The terminal branches of the tibial nerve show up from the deep posterior compartment, linking up with the long tendons and crossing the ankle on the medial side. As it crosses the ankle, it splits into the medial and lateral plantar nerves. These nerves give motor and sensory innervation to the plantar foot. The medial plantar nerve gives sensation to the first 3 1/2 toes including the tip and nail bed (similar to the median nerve of the hand). The lateral plantar nerve gives sensory to remaining 1 1/2 toes. The posterior tibial artery also crosses the ankle of the ankle and splits into medial and lateral plantar arteries.

Muscles of layer 3.

The flexor hallicus brevis has two heads. The flexor digiti minimi brevis. The adductor hallicus has an oblique head and a transverse head which forms a common tendon that attaches to the lateral aspect of the first metatarsal. This allows the big toe to adduction against toe II. The reference point in the foot is toe II for adduction and abduction (it was the middle finger in the hand).

Muscles of layer 4 are the interosseous muscles. These muscles are important in holding the toes together when the foot is bearing weight and don’t really do much adduction or abduction.

The lateral plantar artery has a deep arch that gives off plantar metacarpal arteries. Between metatarsal I and II, it will meet with the communication deep plantar artery coming from the deep dorsal artery of the foot.

Flexor hallicus longus and flexor digitorum brevis from the leg insert to the digits. Tibialus anterior from the anterior compartment of the leg goes to the medial side of the foot and attaches to the plantar base of the metatarsal I and the medial cuneiform; its action helps invert the foot.

Tibialis posterior comes from the posterior compartment, and comes into the plantar side of the foot and attaches extensively to the metatarsals and tarsal bones. This muscle is important in the inversion of the foot.

Fibularis brevis attaches to the base of metatarsal V. The tendon of fibularis longus parallels fibularis brevis until it gets into the foot, where it goes off  from the lateral side, going diagonally to the medial side and attaches to the medial cuneiform and acts as the most effect muscle for eversion and as a suspensory cable to help maintain arch integrity.

There are 3 plantar interosseous muscles on the plantar surface of the foot. The plantar interosseous muscles adduct the toes III, IV, and V towards toe II. There is no plantar interosseous for toe I because it has adductor hallicus.

The dorsal interosseous take origin on the adjacent sides of the metatarsals. The dorsal interosseous muscles are abductors. Toes IV and III have dorsal interosseous muscles while Toe II has 2 interosseous muscles on either side.

Medial plantar nerve supplies motor innervation to flexor hallicus brevis, flexor digitorum brevis, Abductor hallicus, and the first lumbrical. Everything else gets motor innervation from the lateral plantar nerve.

The plantar calcaneo-navicular ligament on the plantar surface. Underneath is where the head of the talis articulates with the navicular bone. This supports the joint from the plantar surface, holding the head of the talis into the fossa of the navicular bone. It is also called the “spring” ligament. If this ligament is damaged, then the arches begin to sag because its not supporting the talis, the keystone bone.

The talis articulates with the subtalar joint on the superior surface of the calcaneous bone.



The medial collateral ligament of the ankle joint that goes from tibia to calcaneous, to talis anteriorly and posteriorly, and to the navicular bones. This is sometimes called the deltoid ligament when all 4 of these subdivisions are liked together. The deltoid ligament is drawn taunt by eversion, resisting eversion actions. Injuries of forced eversion, a portion of the medial malleoulus will be torn from bone. If the deltoid ligament tears off the medial malleoulus, the distal fibula can fracture (Pott’s fracture) on the other side as the eversion motion keeps going.

The ankle joint capsule is very thin.

The components of the lateral collateral ligaments are not as numerous and smaller. The lateral collateral ligaments restrict the movements of inversion much less than eversion. These injuries are common because the inversion motion isn’t as strongly resisted. These ligaments are very strong and forced inversion can also tear the malleolus from the fibula.

Sprain is damage to ligament. Strain is damage to muscle or tendon.

Strengthen the muscles crossing the joint can often reestablish integrity to the joint after ligament damage. The quadriceps tendons help reinforce the knee joint.

The fibula does not participate with the femur at the knee joint. The fibrous capsule at the knee joint is very thick and opaque.

The fibers for semimembranosis gives off some fibers to reinforce the oblique popliteal ligament. Poplitealis muscle and tendon goes through the fibrous joint capsule. The poplitealis tendon is intracapsular. This separates the lateral (fibular) collateral ligament from the knee joint as it goes from the lateral condyle to the head of the fibula. The medial (tibial) collateral ligament is intimate and fused with the joint capsule. The lateral and medial collateral ligaments are extracapuslar.

Inside the capsule, the poplitealis tendon is inside the capsule. Inside the capsule are also the posterior and anterior cruciate ligaments which form a cross. These intracapsular ligaments help hold the femur to the tibia. There are lateral and medial menisci under the medial and lateral condyles of the femur which are fibrous cartilage and deepen the articular surface between the tibia and the femur.

The medial collateral ligament is intimately attached to the fibrous joint capsule, and is anchored to the medial meniscus. The lateral meniscus is more mobile because it is not attached by the lateral collateral ligament because of the poplitealis tendon. As a result, the medial meniscus is more vulnerable because of its restricted mobility. Thus, damage to the medial collateral ligament often is accompanied by damage to the medial meniscus.

The capsule on the anterior side is very thin incomplete, filled in by the patela ligament. It gets some tendon reinforcement from the vastus medialis and lateralis tendons.

The origin of poplitealis tendon comes from the lateral condyle.

The menisci thicken on the deep edge to help deepen the articular surface. The lateral portion is vascular; the medial portion is not vascular, getting nutrients from the synovial fluid and takes a long time to heal from damage. Pieces of articular cartilage can break off and get stuck in the articular surface – this is called joint “mice” and float around in the synovial cavity and can be extremely painful when they get stuck in between the articular surface.

Sports have developed rules for illegal moves because they easily damage the knee. Knee is most vulnerable when partially flexed and the foot is planted on the ground. Blocking below the waist (blocking the femur) in football will damage the anterior cruciate ligament.

The anterior drawer test can test the anterior cruciate ligament. With patient sitting with leg dangling over the edge, test by trying to move the tibia (like a drawer) with the femur fixed. If it displaces anteriorly, then the anterior cruciate ligament is damage. If the tibula can be displaced posteriorly, then the posterior cruciate ligament is damaged.

If the tibia can rotate laterally, and the patient has pain, that is lateral meniscus damage; rotation medially with pain is lateral meniscus damage.

The unhappy triad – damage on the medial collateral ligament, the medial meniscus, the anterior cruciate ligament (ACL).

The poplitealis muscle rotates the tibia medially up to 5 degrees laterally when the limb is not bearing weight. The poplitealis muscle rotates the femur up to 5 degrees medially when the limb is bearing weight (and the leg is locked with the ankle).

There are 3 extracapuslar ligaments reinforcing the hip joint. The largest is the one comes from the ileum and goes over to the intertrochanteric line, called the ileofemoral ligament (a.k.a. Y-ligament, or Bigalow ligament). Arguably, it is the strongest ligament in the body. It is important in limiting hyperextension of the leg joint; also explains why you can get more flexion angle than extension angle from the hip joint.

The pubofemoral ligament goes from the pubis to the proximal end of the femur. This ligament is important in resisting abduction of the hip joint.

Diverticuli of the synovial membrane can outpocket and form bursa through holes in these extracapsular ligament. This allows structures passing through to slide across the fibrous joint capsule easily.

The ischiofemoral ligament is the thinnest and most poorly developed of the 3 hip extrinsic tendons. It is supposed to resist flexion of the hip joint.

The articular surface of the hip joint at the acetabulum is incomplete. The inside of the acetabulum has bone in the middle so the articular surface is C-shaped. There is a labrum to increase the depth of the socket. The head of the femur fits inside the labrum and the acetabulum fits in beyond its equator (meaning more than 1/2 is inside). The fovea of the femur contains a blood vessel that goes into the head of the femur; not a substantial blood supply to sustain the head of the femur just by itself.

Most of the head of the femur and neck of the femur gets most of its blood supply on the medial circumflex femoral artery.

"Broken Hip" is usually a fracture of the femur at the neck region. This fracture at the neck is very precarious because it can compromise the medial circumflex femoral artery and cut off the blood supply; if broken, the bone would not only not heal, but become necrotic and lead to the loss of the joint.

Deep into the acetabulum, the aacetabulum can be very thin; trauma can cause the femur to drive right through the acetabulum, causing a pelvic fracture. This can easily happen in an automobile accident without seatbeats and the femur goes right into the dashboard.