Gross Anatomy: Leg & Foot Dorsum 2024 PDF

Gross Anatomy: Leg & Foot Dorsum Page 1 of 19 Dr. Paul Walker Session Learning Objectives By the end of this session, students should be able to accurately: I. Summarize the general anatomy of the leg including its skeletal framework and 3...

Gross Anatomy: Leg & Foot Dorsum Page 1 of 19 Dr. Paul Walker Session Learning Objectives By the end of this session, students should be able to accurately: I. Summarize the general anatomy of the leg including its skeletal framework and 3 compartments. II. Describe the posterior compartment of the leg- include a discussion of muscles and neurovascular relationships, as well as clinical applications. III. Describe the lateral compartment of the leg- include a discussion of muscles and neurovascular relationships, as well as clinical applications. IV. Describe the anterior compartment of the leg- include a discussion of muscles and neurovascular relationships, as well as clinical applications. V. Describe the anatomy of the foot dorsum- include a discussion of muscles and neurovascular relationships, as well as clinical applications Session Outline I. Anatomical Overview of the Leg A. Superficial & Deep Fascia B. Skeletal Framework C. Overview of the Leg Compartments II. Posterior Compartment of the Leg A. Superficial muscle group B. Deep muscle group C. Neurovascular anatomy III. Lateral Compartment of the Leg A. Muscles B. Neurovascular anatomy IV. Anterior Compartment of the Leg A. Muscles B. Neurovascular anatomy V. Foot Dorsum A. Muscles B. Neurovascular anatomy Supplemental Reading Gray’s Anatomy for Students, 4thEd (2020) Drake, Vogl, Mitchell (Elsevier) Chapter 6- Lower Limb Clinically Oriented Anatomy, 7thEd (2014) Moore, Dalley, Agur (Wolters Kluwer) Chapter 5- Lower Limb Gross Anatomy: Leg & Foot Dorsum Page 2 of 19 Dr. Paul Walker I. Anatomical Overview of the Leg A. Superficial & Deep Fascia Fig 1 Netter 470 The leg is the region between the knee & ankle joints (Figs 1-2). The deep fascia that covers the leg is a continuation of the fascia lata of the thigh region. The great saphenous vein is located on the medial side of the anterior leg (Fig 1) and is related to the saphenous nerve (sensory branch of femoral nerve). It arises medially from the dorsal venous network of the foot dorsum. The small saphenous vein is located on the posterior leg (Fig 2) and is related to the sural nerve (sensory branch of tibia nerve). It arises laterally from the dorsal venous network of the foot dorsum. Fig 2 Netter 471 The saphenous nerve (branch of femoral n) innervates the anterior and posterior skin surfaces of the medial leg and includes the medial knee region and medial ankle and foot regions (Figs 1 & 3). Recall the saphenous nerve travels in the adductor canal of the anterior thigh with the femoral artery and vein. The sural nerve (branch of tibial n. or common fibular n. or both) can be found in the superficial fascia near the small saphenous vein in the posterior leg (Figs 2 & 3). It innervates the skin of the lower posterolateral leg and lateral ankle and foot. A cutaneous branch of the common fibular nerve innervates the skin of the superolateral leg (including the skin of the lateral knee region). The cutaneous portion of the superficial fibular nerve innervates the skin of the anterior leg inferiorly and also much of the skin of the foot dorsum (Figs 1 & 3). Fig 3 Gray’s Anatomy for Students) Gross Anatomy: Leg & Foot Dorsum Page 3 of 19 Dr. Paul Walker B. Skeletal Framework of the Leg Learn the bony landmarks of the tibia and fibula using your atlas as well as the bones in your cadaver table drawer. A figure from the Netter atlas is included below for your reference. Fig 4 (Netter 500) Gross Anatomy: Leg & Foot Dorsum Page 4 of 19 Dr. Paul Walker Fig 5 (Gray’s Anatomy for Students) C. Overview of the Leg Compartments The deep fascia sends intermuscular septa that subdivide the leg into 3 compartments: Posterior Compartment Lateral Compartment Anterior Compartment An interosseous membrane located between the tibia and fibula separates the anterior and posterior compartments (Figs 5-6). Anterior and posterior intermuscular septa separate the lateral compartment from the other compartments. (Figs 5-6). Fig 6 (Grant’s Dissector) Note that the posterior compartment of the leg is divided into superficial and deep muscle groups by the transverse intermuscular septum (Fig 6). Neurovascular structures such as the tibial nerve and posterior tibial artery and vein are found in this plane. Gross Anatomy: Leg & Foot Dorsum Page 5 of 19 Dr. Paul Walker Posterior Compartment Lateral Lateral femoral condyle femoral condyle Mainly Mainly to tonavicular naviculartuberosity tuberosity& & medial medial cuneiform. cuneiform. Lateral Compartment Anterior Compartment & Foot Dorsum Gross Anatomy: Leg & Foot Dorsum Page 6 of 19 Dr. Paul Walker Visual diagram of leg muscle attachments: Fig 7 (Netter 506) Gross Anatomy: Leg & Foot Dorsum Page 7 of 19 Dr. Paul Walker II. Posterior Compartment of the Leg Main actions of muscles: foot plantarflexion, foot inversion, & toe flexion. All muscles innervated by the tibial nerve. A. Superficial Muscle Group: Fig 8 (Netter 503) Gastrocnemius m (Fig 8) G- refers to calf of leg: 2 heads- medial and lateral Proximal Attachment: Distal femur superior to the femoral condyles. Distal Attachment: The heads converge and form a thick tendon distally- the calcaneal (Achilles) tendon that inserts on the posterior surface of calcaneus (heel bone). Innervation: tibial n. Actions: leg flexion, foot plantarflexion. Gross Anatomy: Leg & Foot Dorsum Page 8 of 19 Dr. Paul Walker Soleus m (Figs 9-10) L: sandal, sole of foot: Fig 9 (Grays Anatomy for Students) Proximal Attachment: soleal line of the tibia, head of the fibula Distal Attachment: joins the calcaneal (Achilles) tendon to insert on the calcaneus. Innervation: tibial n. Actions: foot plantarflexion. There is a tendinous arch of the soleus located between the tibia/fibula origins of the muscle that arches over the popliteal vessels and tibia nerve as they pass out of the popliteal fossa (Fig 10). Plantaris m (Fig 10): Sometimes absent. Proximal Attachment: supracondylar line above the lateral head of the gastrocnemius. Distal Attachment: long thin tendon joins the calcaneal tendon Innervation: tibial n. Actions: weak leg flexion, foot plantarflexion. The plantaris tendon is humorously called the ‘freshman nerve’ because inexperienced students mistake it for a nerve. Clinical Note: Achilles Tendon Injuries: The Achilles tendon can become weak and thin with age, and also because of certain illnesses (diabetes, arthritis) or medications (quinolone antibiotics such as Levaquin or Cipro). A weakened Achilles tendon is prone to rupture in recreational sports that require sudden pivoting, jumping, and running. Achilles tendon injuries are also common in normal healthy athletes that perform these movements. Fig 10 (Netter 504) Gross Anatomy: Leg & Foot Dorsum Page 9 of 19 Dr. Paul Walker B. Deep Muscle Group: Fig 11 (Left 2015 prosection, Right Grays Anatomy for Students) Popliteus m: Proximal Attachment: lateral femoral condyle. Distal Attachment: posterior surface of proximal tibia (superior to soleal line). Innervation: tibial n. Actions: Weak leg flexor. Also rotation of leg at knee. When the tibia is fixed (foot on ground), the primary action of the popliteus is lateral (external) rotation of femur to unlock knee joint. This is needed to initiate leg flexion from a fully-extended (locked) leg. When the tibia is not fixed (foot in air as in running), the popliteus helps stabilize the knee joint by resisting excessive rotation. Gross Anatomy: Leg & Foot Dorsum Page 10 of 19 Dr. Paul Walker Fig 12 (Grays Anatomy for Students) Tibialis Posterior (TP) m. Proximal Attachment: interosseous membrane and adjacent regions of proximal tibia and fibula. Distal Attachment: mainly to tuberosity of navicular bone and medial cuneiform. Innervation: tibial n. Actions: main inverter of the foot. Also plantarflexes foot and supports medial arch during walking. Flexor Digitorum Longus (FDL) m. Proximal Attachment: medial surface of posterior tibia inferior to soleal line. Distal Attachment: base of distal phalanges II-V. Innervation: tibial n. Actions: flexes lateral 4 toes and plantarflexes foot. Flexor Hallucis Longus (FHL) m. Proximal Attachment: interosseous membrane and distal 2/3 of posterior fibula. Distal Attachment: base of distal phalanx I. Innervation: tibial n. Actions: flexes great toe and plantarflexes foot. The great toe is the last to leave the ground during transition from stance to swing and FHL is important to pushing off with the great toe during walking and running. The FHL tendon passes posterior to the distal end of the tibia and then slips into a groove on the posterior process of the talus. The FHL tendon then curves anteriorly under the talus and then under the sustentaculum tali of the calcaneus (Fig 13) as it travels through the sole of the foot to insert on the base of the distal phalanx of the great toe. These bony features act as a pulley to change the direction of force applied to the FHL tendon, thus giving the great toe more power to flex and assist in plantarflexion of the entire foot. Fig 13 (Netter 512) Gross Anatomy: Leg & Foot Dorsum Page 11 of 19 Dr. Paul Walker C. Neurovascular Anatomy of the Posterior Leg Compartment Fig 14 (Grays Anatomy for Students) The popliteal vessels and tibia nerve enter the posterior leg compartment from the popliteal fossa by passing between the heads of the gastrocnemius m. superficial to the popliteus m. The neurovascular structures pass through the tendinous arch of the soleus muscle and travel within the transverse intermuscular septum superficial to the tibialis posterior m. Immediately after the popliteal a. passes under the tendinous arch of the soleus m., it divides into the posterior tibial a. and anterior tibial a. The anterior tibial a. passes into the anterior leg compartment by traveling between the tibial & fibular origins of the tibialis posterior m. and then through a superior gap of the interosseous membrane. The posterior tibial a. continues traveling with the tibial n within the transverse intermuscular septum. About 2-3 cm distal to the popliteus m., the fibular artery arises from the posterior tibial a. and travels to supply the lateral compartment of the leg. Both posterior tibial a. and tibial n. continue distally to enter the foot via the tarsal tunnel (described below) along with the tendons of the deep muscles of the posterior leg compartment. The sural nerve branches from the tibial nerve at the level of the popliteal fossa and pierces the deep fascia at midpoint of the posterior leg. The nerve becomes cutaneous to innervate the skin of lateral ankle and foot. It travels with the small saphenous vein. Gross Anatomy: Leg & Foot Dorsum Page 12 of 19 Dr. Paul Walker Clinical Notes Deep Vein Thrombosis (DVT) of the leg veins may generate a thrombosis (clot) that propagates into the femoral veins, IVC, and heart to occlude the pulmonary artery resulting in cardiopulmonary arrest. A significant number of surgery patients develop DVT so most procedures involve prophylactic anti-coagulants and graduating stockings. Compartment Syndrome occurs when there is swelling of a fascial enclosed muscle compartment of the limbs (both upper/lower). If tissue perfusion is compromised even for a limited period, neuromuscular damage ensues. This can be quite painful. Peripheral Vascular Disease is characterized by reduced blood flow (ischemia) to the legs and is usually accompanied by more widespread arterial disease. Chronic leg ischemia usually results when vessels exceed 50% luminal narrowing. The most common symptom is intermittent claudication- pain developing in the calf or buttocks that occurs with walking. The patient rests and is able to continue walking until the pain recurs. Fig 15 below (Grays Anatomy for Students) D. Tarsal Tunnel (Fig 15) The flexor retinaculum is a band of connective tissue between the medial malleolus and the inferomedial surface of the calcaneus. It is continuous with the deep fascia of the leg above and the plantar aponeurosis of the foot below. Septa from the retinaculum form tubular channels for the tendons to pass. Synovial membranes surround the tendons to allow smooth movement. Deep to the flexor retinaculum is a depression formed by the medial and inferior surfaces of the talus and the medial surface of the calcaneus. The inferior surface of the sustentaculum tali is also located in this depression. The tarsal tunnel is the passageway through this region that allows structures to travel from the leg to the foot. Structures passing through the tarsal tunnel include: Tibialis posterior tendon Flexor Digitorum Longus tendon Posterior Tibial artery and vein Tibial nerve Flexor Hallucis Longus tendon Mnemonic for the anterior to posterior (or medial to lateral) organization of structures passing through the tarsal tunnel is: Tom, Dick, and very nervous Harry. Clinical Note: The pulse-point for the posterior tibial artery is midway between the heel and the medial malleolus. We will resume studying the above structures in the sole of the foot in the next lecture. Gross Anatomy: Leg & Foot Dorsum Page 13 of 19 Dr. Paul Walker III. Lateral Compartment of the Leg Main actions of muscles: foot eversion & plantar flexion. All muscles innervated by superficial fibular nerve. Fig 16 (Grays Anatomy for Students) A. Muscles Fibularis Longus (FL) m. (Fig 16) Proximal Attachment: head of fibula and upper 2/3 lateral surface of fibula. Distal Attachment: medial cuneiform (undersurface) and base metatarsal I. Innervation: superficial fibular n. Actions: foot eversion and plantarflexion. Helps support foot arches. Fibularis Brevis (FB) m. (Fig 13) Proximal Attachment: lower 2/3 lateral surface of fibula. Distal Attachment: tuberosity of metatarsal V. Innervation: superficial fibular n. Actions: foot eversion and plantarflexion. B. Fibular Retinaculum (Fig 17) 2 fibular (peroneal) retinacula bind the FL and FB tendons to the lateral side of the foot. Superior Fibular Retinaculum- between lateral malleolus and calcaneus Inferior Fibular Retinaculum- lateral side calcaneus. Inferior attachment is fibular trochlea of calcaneus. Blends with base of inferior extensor retinaculum. At the fibular trochlea of the calcaneus, a septum separates the compartment of the FB tendon above from the FL tendon below. Fig 17 (Grays Anatomy for Students) Gross Anatomy: Leg & Foot Dorsum Page 14 of 19 Dr. Paul Walker B. Neurovascular Anatomy of Lateral Compartment of the Leg There is no major artery that runs in the lateral compartment. Muscles are supplied by branches of the fibular artery that penetrate into the lateral compartment. The common fibular n. arises from the sciatic n. in the posterior thigh or popliteal fossa. It runs along the medial edge of the biceps femoris tendon and passes superficial to the lateral head of the gastrocnemius m. as it travels toward the head of the fibula. Prior to splitting into superficial and deep fibular nerves, the common fibular n. gives 2 branches: lateral sural cutaneous n. that innervates skin of upper lateral leg, and sural communicating n. which joins the sural n. As such the sural n. contains both tibial and common fibular n. contributions. The common fibular n. wraps around the neck of the fibula and passes into the lateral compartment between the fibularis longus m. origin from fibular head and shaft. Here it divides into superficial and deep fibular nerves. The superficial fibular n. supplies the lateral compartment muscles and then continues as a sensory n. that emerges between the fibularis longus and brevis m. to pierce the deep fascia and travel superficially to innervate skin areas of the distal anterolateral leg and foot dorsum. The deep fibular n. pierces the intermuscular septum to enter the anterior compartment of the leg. Fig 18 (Grays Anatomy for Students) Gross Anatomy: Leg & Foot Dorsum Page 15 of 19 Dr. Paul Walker IV. Anterior Compartment of Leg Main actions of muscles: foot inversion & dorsiflexion. All muscles innervated by deep fibular nerve Fig 19 (Grays Anatomy for Students) Tibialis Anterior (TA) m. Proximal Attachment: lateral tibial condyle & proximal ½ lateral tibia & interosseous membrane. Distal Attachment: medial cuneiform and base metatarsal I. Innervation: deep fibular n. Actions: foot dorsiflexion & inversion. Supports medial arch of foot. Extensor Digitorum Longus (EDL) m. Proximal Attachment: lateral tibial condyle & proximal ½ fibula & interosseous membrane. Distal Attachment: extensor expansions to distal phalanges II-V. Innervation: deep fibular n. Actions: extends toes II-V and foot dorsiflexion. Fibularis Tertius (FT) m. Proximal Attachment: distal medial surface of fibula (considered extension of EDL) Distal Attachment: dorsum base metatarsal V. Innervation: deep fibular n. Actions: foot eversion and dorsiflexion. Extensor Hallucis Longus (EHL) m. Proximal Attachment: middle ½ fibula & interosseous membrane. Distal Attachment: dorsal base distal phalanx I. Innervation: deep fibular n. Actions: extends great toe and foot dorsiflexion. Gross Anatomy: Leg & Foot Dorsum Page 16 of 19 Dr. Paul Walker B. Neurovascular Anatomy of Anterior Compartment of the Leg Fig 20 (Grays Anatomy for Students) After passing over the superior aperture of the interosseous membrane, the Anterior Tibial artery descends through the anterior compartment on the interosseous membrane (Figs 20 & 21- next page). In the distal leg, the anterior tibial a. lies between the TA & EHL muscles. Prior to crossing the ankle joint, the anterior tibial a. gives off the anterior medial malleolar a. and anterior lateral malleolar a. that connect with vessels from the posterior tibial a. to form an anastomotic network around the ankle joint (Figs 20 & 21- next page). The anterior tibial a. passes across the ankle joint anterior to the distal end of the tibia and enters the dorsum of the foot. There its name changes to Dorsalis Pedis artery. After it enters the proximal region of the anterior leg compartment, the deep fibular n. travels deep to the EDL m (Fig 20). It then travels with the anterior tibial a. sending muscular branches to anterior compartment muscles and continuing to the dorsum of the foot to innervate the extensor digitorum brevis m. and then continues as a sensory nerve to innervate the skin between the great and 2nd toe. Clinical Notes: Foot-Drop: A patient with damage to the common fibular n. experiences ‘footdrop’- the inability to dorsiflex the foot. This results in ‘steppage’ gait- elevation of the knee during swing phase to keep the foot from dragging. The foot slaps to the ground at the end of swing phase. Shin Splints (Medial Tibial Stress Syndrome): Common in runners and results from injury to connective tissue attachments to the tibia. Dull aching pain is felt in the area of the shin (lower medial tibia) that increases to intense pain during exercise. Gross Anatomy: Leg & Foot Dorsum Page 17 of 19 Dr. Paul Walker Fig 21 (Netter 509) Gross Anatomy: Leg & Foot Dorsum Page 18 of 19 Dr. Paul Walker B. Extensor Retinaculum Fig 22 (Grays Anatomy for Students) Two retinacula strap down the extensor muscles and tendons to prevent bowing during foot & toe extension (dorsiflexion). Superior Extensor Retinaculum thickening of leg deep fascia between distal tibia and fibular, above the ankle joint. Inferior Extensor Retinaculum Y-shaped structure at the ankle joint. Base attached to lateral side of calcaneus. Wraps over dorsal ankle region. One arm (superior) attaches to medial malleolus. The other arm (inferior) attaches to medial side of plantar aponeurosis. EDL and FT tendons travel through a synovial compartment located laterally under the inferior extensor retinaculum. EHL and TA tendons travel through separate synovial compartments located medially under the inferior extensor retinaculum. The dorsal pedis artery is the continuation of the anterior tibial artery distal to the ankle joint. It enters the foot dorsum between the EDL and EHL tendon compartments. Gross Anatomy: Leg & Foot Dorsum Page 19 of 19 Dr. Paul Walker V. Foot Dorsum Fig 23 (Netter 517) The dorsum of the foot can be studied as an extension of the anterior compartment of the leg distal to the ankle joint. A. Intrinsic Muscles There are 2 intrinsic muscles of the foot located in the foot dorsum: Extensor Digitorum Brevis (EDB) m. Proximal Attachment: superolateral surface of calcaneus (area of tarsal sinus). Distal Attachment: lateral sides of extensor expansion tendon of digits II-IV. Innervation: deep fibular n. Actions: extends toes II-IV. Extensor Hallucis Brevis (EHB) m. Proximal Attachment: superolateral surface of calcaneus (area of tarsal sinus). Distal Attachment: lateral side of extensor expansion tendon of digit I. Innervation: deep fibular n. Actions: extends great toe. B. Vascular Relations After entering the foot dorsum, the Dorsalis Pedis artery gives off: Fig 24 (Netter 518) Medial and lateral tarsal branches that contribute to the anastomotic network of the ankle joint. The lateral tarsal a. travels with a muscular branch of the deep fibular n. to the EDB and EHB muscles. Arcuate a. that courses laterally over the dorsal surface of the metatarsals. It gives rise to dorsal metatarsal branches. The Dorsalis Pedis artery gives off the Deep Plantar artery that courses between the two heads of the 1st dorsal interosseous muscle into the sole of the foot. The Deep Plantar artery connects to the plantar arch of the foot formed by the lateral plantar artery. Clinical Note: The dorsal pedis arterial pulse can be detected between the EDL and EHL tendons in the foot dorsum. Fig 25 (Grays Anatomy for Students)