Week 8 Outline (Exam 4)

• Lower limb anatomy and development, including bones, vasculature, innervation, muscles, and clinical considerations.

Limb Development and Rotation

• Parts of the lower limb correspond to the upper limb.
• Differences arise from rotation around the longitudinal axis during fetal development.
• Upper limbs rotate 90 degrees laterally.
• Lower limbs rotate 90 degrees medially.
• Knees point anteriorly while elbows point posteriorly due to limb rotation.
• The dorsum of the foot is anterior, whereas the dorsum of the hand is posterior.

Skeleton of the Lower Limb

• Includes the pelvic girdle and lower limb bones, such as the femur, tibia, and fibula.

Pelvic Girdle

• A basin-shaped bony ring connects the lower trunk and spinal column to the femur.
• It comprises:
  • Right and left hip bones (fusion of ilium, ischium, and pubis)
  • Sacrum (fused sacral vertebrae)
  • A joint anteriorly at the pubic symphysis

Lower Limb Bones

• Thigh contains the femur and patella
• Leg contains the tibia and fibula
• Foot contains 7 tarsals, 5 metatarsals, and 14 phalanges

Bones and Bony Landmarks

• Hip region is located between the iliac crest and greater trochanter of the femur.
• Hip bone (coxal/pelvic bone, or innominate)
  • Composed of 3 bones fused at the acetabulum by ages 15-17 and completely fused by age 23.

Ilium landmarks

• Includes iliac fossa, iliac crest at L4 level
• Anterior superior iliac spine (ASIS), anterior inferior iliac spine (AIIS)
• Posterior superior iliac spine (PSIS) which is indicated by skin dimples at S2 level
• Posterior inferior iliac spine (PIIS), and gluteal lines (posterior, anterior, inferior).

Ischium characteristics

• L-shaped, forming the posterior-inferior 1/3 of the hip bone.
• Includes Ischial tuberosity, ischial spine which separates the greater and lesser sciatic notches.
  • Greater sciatic notch is located with the ilium
• Ischiopubic ramus (ischial and inferior pubic ramus together), and obturator foramen.

Pubis

• L-shaped, forming the inferior-anterior part of the hip bone; it includes the superior and inferior pubic rami.
• Pubic tubercle is another feature
• Acetabulum: a cup-shaped socket on the lateral side.

Thigh Region

• Located between the greater trochanter and knee.
• Femur is the longest and strongest bone, ~4x a person's height.
• Femur features a head with a fovea (site for ligamentum teres), neck, greater trochanter (attachment for abductors and external rotators), and lesser trochanter (attachment for iliopsoas).
• Intertrochanteric line is the attachment for the iliofemoral ligament
• Intertrochanteric crest with quadrate tubercle (Quadratus femoris)
• Shaft (body), condyles (medial and lateral), epicondyles (medial and lateral)
• Intercondylar fossa, gluteal tuberosity, linea aspera (attachment for adductors), adductor tubercle, and pectineal line.

Leg Region

• The inferior part of the lower limb between the knee and ankle.

Bones of the Leg

• Tibia:
  • The 2nd largest bone on the medial side of the leg.
  • Possesses medial and lateral condyles (with tibial plateaus)
  • Intercondylar eminence, tibial tuberosity (attachment for patellar tendon)
  • Anterolateral tibial tubercle (Gerdy's tubercle) for IT band attachment, shaft (body), soleal line, and medial malleolus.
• Fibula (Latin: pin):
  • It is the lateral bone of the leg
  • Includes the head and lateral malleolus.

Foot's Tarsal Bones

• Consists of the Talus, Calcaneus, Navicular, 3 Cuneiforms (medial, intermediate, lateral), and Cuboid.
• Metatarsals (5) are numbered laterally from the great toe (Digit 1).
• Phalanges (14) are also numbered laterally
• Great toe has a proximal and distal phalanx
• Digits 2-5 have proximal, middle, and distal phalanges.

Fascia of Lower Limb

• Fascia Lata: deep fascia of the thigh
  • Continuous with the inguinal ligament, body of the pubis, pubic tubercle, and Scarpa fascia anteriorly.
  • Continuous with the iliac crest laterally and posteriorly.
  • Continuous with the Sacrum, coccyx, ischial tuberosity posteriorly and medially.
• Attaches to exposed parts of the bones around the knee region and deep fascia of the lower leg.
• Encloses large thigh muscles to prevent bulging.
• Thickened laterally to form the iliotibial band (tract).
• IT band extends from the iliac crest to Gerdy's tubercle of the tibia.

Deep Fascia of the Leg (Crural Fascia)

• Fascia of the lower leg that attaches to the anterior and medial borders of the tibia.
• Continuous with the periosteum.
• Forms proximal attachments of underlying muscles of the anterior leg.
• Forms extensor retinacula at the ankle joint.

Arteries of the Lower Limb

• Originate from the common iliac artery, which divides into internal and external iliac arteries.
• External Iliac Artery becomes the femoral artery and supplies the majority of the LE.
• After passing the inguinal ligament, it becomes the femoral artery.
• The femoral artery gives off a branch called the deep femoral artery.
• It becomes the popliteal artery in the popliteal fossa.
• The popliteal artery bifurcates into anterior and posterior tibial arteries.
• The anterior tibial artery becomes the dorsalis pedis artery on the dorsum of the foot.

Veins of the Lower Limb

• Drain into the external iliac veins, then to the inferior vena cava.
• Superficial veins include:
  • Great saphenous vein runs from the foot to the femoral vein along the medial calf and thigh.
  • Small saphenous vein runs from the foot to the popliteal vein along the posterior calf.
• Deep veins accompany major arteries within a vascular sheath.

Lymphatics of the Lower Limb

• Superficial lymphatics accompany the saphenous veins and their tributaries.
• Vessels running with the great saphenous vein drain to superficial inguinal lymph nodes.
• Vessels running with the small saphenous vein drain to popliteal lymph nodes.
• Superficial inguinal lymph nodes drain the buttocks, external genitalia, lower vagina and vulva, anal canal, and lower abdominal wall.
• Popliteal lymph nodes surround the popliteal vein in the popliteal fossa and drain deep leg and foot structures.
• Deep inguinal lymph nodes are located medially to the femoral vein which drains deep structures of the lower extremity.

Innervation of the Lower Extremity

• Receives sensory and motor innervation from the lumbar and sacral plexus.
• Lumbar Plexus (ventral rami L1-L4):
  • Femoral N. (L2-L4) and Obturator N. (L2-L4).
• Sacral Plexus (ventral rami L4-S4):
  • Superior Gluteal N. (L4-S1), Inferior Gluteal N. (L5-S2)
  • Sciatic N. (L4-S3) which splits into the Tibial N. and Common Fibular N.
  • Posterior Femoral Cutaneous N. (S1-S3)
  • N. to Piriformis (S1-S2), N. to Obturator Internus (L5-S2), and N. to Quadratus Femoris (L4-S1).
• Dermatomes:
  • L1- inguinal region, L2-medial thigh, L3 -medial knee, L4 -Medial Malleolus, L5-Dorsum of foot over the 3rd met.
  • S1-Lateral Malleolus, S2-Popliteal Fossa.
• Myotomes:
  • L2 - Hip flexion, L3 - Knee Extension, L4-Ankle DF (dorsiflexion), L5-Toe Extension, S1 Ankle PF (plantarflexion), and S2-Toe Abduction.

Areas of Transition

• Femoral Triangle:
  • Transition between the trunk and lower extremity.
  • Passage for the femoral artery, femoral vein, and femoral nerve.
  • Structures pass under the inguinal ligament.
• Popliteal Fossa:
  • Posterior transition between the thigh and leg which includes passage for major vessels.
• Tarsal Tunnel:
  • Posteromedial transition between the leg and foot which includes passage for most nerves, vessels, and flexor tendons to plantar aspect of the foot.

Hip Joint

• Articulation between the head of the femur and the acetabulum.
• Ball and socket synovial joint with the acetabulum deepened by a cartilaginous labrum (acetabular labrum).
• Ligamentum teres: connective tissue between the fovea of the femur and the acetabulum carrying a small branch of the obturator artery.
• Transverse ligament is an extension of the labrum inferiorly.
• Ligaments: strong joint capsule, pubofemoral ligament (thickening of joint capsule anterior and inferior, limits abduction), iliofemoral ligament (Y ligament, limits hyperextension), and ischiofemoral ligament (thickening of joint capsule posterior, limits internal rotation).
• Movement: flexion/extension, abduction/adduction, external/internal rotation, and circumduction.

Anterior Thigh Muscles

• Primarily hip flexors and knee extensors
• Most are innervated by the femoral nerve (L2-L4).
• Pectineus, Sartorius (Tailor), distal ends of iliopsoas (psoas major + iliacus), and quadriceps femoris (4-headed muscle of the femur) consisting of the Rectus femoris, Vastus lateralis, Vastus medialis, and Vastus intermedius.

Medial Thigh Muscles

• Hip adductors innervated by the obturator nerve (L2-L4).
• Gracilis, adductor longus, adductor brevis, adductor magnus (adductor and hamstring portions), and obturator externus.

Pes Anserine (Goose's Foot)

• Superior part of the medial surface of the tibia which adds medial stability to the knee.
• It is the common insertion point for the sartorius, gracilis, and semitendinosus muscles.

Femoral Triangle

• A triangular depression in the anterior thigh inferior to the inguinal ligament.
• Features borders: the inguinal ligament superiorly, the lateral border of adductor longus medially, and the sartorius laterally.
• The floor is composed of the iliopsoas laterally and the pectineus medially.
• The inguinal ligament acts as a flexor retinaculum, and the structures run in the retro-inguinal space.
• The contents (lateral to medial) are the femoral nerve, femoral sheath (femoral artery and vein), deep inguinal lymph nodes, and vessels.

Adductor Canal

• A space between the vastus medialis, sartorius, and adductor longus that acts as a passage for the femoral artery and vein.

Adductor Hiatus

• An opening between the adductor and hamstring portions of the adductor magnus.
• It is a passage for the femoral artery and vein from adductor canal in the thigh to popliteal fossa of the posterior knee.

Anterior Compartment of the Leg

• Includes dorsiflexors and digit extensors, innervated by the deep fibular nerve.
• Tibialis anterior, extensor hallucis longus, extensor digitorum longus, and fibularis tertius (sometimes present)

Retinacula

• Cover anterior compartment tendons to prevent bowstringing.
• Superior extensor retinaculum: from tibia to fibula proximal to malleoli.
  • The superior fibular retinaculum contains fibularis longus and brevis tendons.
• Inferior extensor retinaculum: from medial tibia and navicular to calcaneus.
  • The inferior fibular retinaculum contains fibularis longus and brevis tendons

Clinical Notes

• Pulse points for the lower extremity.
• Varicose veins and deep vein thrombosis (DVT).
• Femur fractures and avascular necrosis (AVN).
• Hip arthroplasty, patellar tendon reflex, groin pull (strain).
• Pes anserine bursitis and tendonitis.
• Compartment syndrome.