Lower Extremity Anatomy for NBPME Exam Part I

Lower Extremity Anatomy for NBPME Part I Exam

• This document is a study guide for an anatomy exam covering the lower extremity.
• Dr. Daniel Bareither is the author.

Part 1 - Osteology (Bony Landmarks and Associated Structures and Ossification)

• Question areas: Foot, Leg, Thigh, and Gluteal region.

Bones of the Foot

• Anatomical position: Foot is at a right angle to the leg.
• Divisions of the foot: Tarsus, Metatarsus, Phalanges, and Sesamoids.
• Tarsus: Calcaneus, talus, cuboid, navicular, and three cuneiforms.
• Metatarsus: Five metatarsal bones.
• Phalanges: Fourteen bones forming the toes.
• Sesamoids: Two bones within the tendons of flexor hallucis brevis.
• Biomechanical division of the foot: Medial and lateral columns.
  • Medial column: Calcaneus, talus, navicular, three cuneiforms, first, second, and third metatarsals with their respective phalanges, and the constant sesamoids.
  • Lateral column: Calcaneus, cuboid, and fourth and fifth metatarsals with their respective phalanges.
• Surgical division (forefoot, midfoot, and rearfoot).
  • Forefoot: Metatarsals (five), phalanges (fourteen), sesamoids (two).
  • Midfoot: Navicular, cuboid, and three cuneiforms.
  • Rearfoot: Calcaneus and talus.
  • Anatomical note: Midtarsal joint (transverse tarsal or Chopart's joint) joins the rearfoot and the midfoot, while Lisfranc's joint(tarsometatarsal joint) connects the midfoot and the forefoot.

Talus

• Second largest tarsal bone.
• Located superior and posterior aspect of the foot.
• Does not have any muscular attachments.
• Articulates with: tibia and fibula (ankle joint), calcaneus (subtalar joint), navicular (talonavicular portion of midtarsal joint).
• Composed of: Body, Neck, and Head.
  • Body: Cuboid in shape, located posteriorly, has five surfaces (superior, inferior, medial, lateral, and posterior).
  • Neck: Constricted and directed anteriorly and medially from the body. Has numerous nutrient foramina for vascular supply.
  • Head: Articular surface for the navicular, three facets on inferior surface (middle calcaneal, anterior calcaneal, and facet for spring ligament).
  • Superior surface: Trochlea, articular surface for the distal extremity of the tibia, Wider anteriorly than posteriorly.
  • Inferior surface: Posterior calcaneal articular surface for the posterior articular facet on the superior surface of the calcaneus.
  • Medial surface: Articular facet for the medial malleolus.
  • Lateral surface: Articular facet for the lateral malleolus, Roughened apex of lateral process.
• Posterior surface: Posterior process, Medial and lateral tubercle, Groove for flexor hallucis longus tendon.

Calcaneus

• Largest bone of the foot, also known as the heel bone.
• Projects posteriorly from the ankle joint to create a lever.
• Articulates with the talus (subtalar joint), cuboid (calcaneocuboid portion of midtarsal joint).
• Six surfaces: posterior, anterior, medial, lateral, superior, and inferior.
• Superior surface: Posterior, middle, and anterior facets. Calcaneal sulcus located between the posterior and middle facets.
• Inferior surface: Calcaneal tuberosity comprised of medial and lateral tubercle with a groove between. Medial process is larger than the lateral. Tubercle with a transverse groove anterior to it (infracalcaneal exostosis or heel spur).
• Other surfaces (superior, medial, lateral): Relevant articular facets.

Cuboid

• Pyramidal in shape.
• Articulates with calcaneus, fourth and fifth metatarsals (tarsal and Lisfranc's joint).
• Six surfaces (posterior, anterior, medial, lateral, superior, and inferior).
• Superior surface: Peroneal sulcus/groove for peroneus longus at anterior aspect. Peroneal ridge, ends laterally in a tuberosity (beak-like process called the beak of the cuboid, coronoid process of the cuboid).
• Other surfaces (superior, medial, lateral): Relevant articular surfaces.

Navicular (Scaphoid)

• Located on the medial side of the foot.
• Articulates with the talus (talonavicular portion of midtarsal joint), three cuneiforms (cuneonavicular joints), occasionally with the cuboid (cuboideonavicular joint), and the calcaneus (calcaneonavicular joint).
• Six surfaces (posterior, anterior, medial, lateral, superior, and inferior).
• Superior surface: Groove for tibialis posterior tendon.
• Medial surface: Tuberosity for tibialis posterior.
• Lateral surface: Occasional facet for articulation with the cuboid.
• Anterior surface: Articular surface divided into three facets for articulation with the three cuneiforms.
• Posterior surface: Articular surface for the head of the talus.

Cuneiforms

• Triangular (wedge-shaped) in morphology.
• Three in number (medial, intermediate, lateral).
• Articulations with each other and other relevant bones.

Metatarsals (1-5)

• Miniature long bones with a base, shaft, and head.
• Numbered 1 to 5 from medial to lateral.
• Distal projection (in the articulated foot): 2>3>1>4>5 (major variation is 2>1>3>4>5)
• Shaft: Tapers from base to head, articular with tarsus, & lesser metatarsals (articulating with each other), and five surfaces (posterior, medial, lateral, superior, and inferior).
• Proximal extremity: Heads of lesser metatarsals, articulate with the proximal phalanx.
• Common characteristics of the head and base.
  • Heads - Concave plantarly, lateral and medial extensions; plantar condyles.
  • Base - Articulate with the tarsus, and lesser metatarsals with each other.

First Metatarsal

• Shortest but strongest .
• Articulates with first cuneiform (tarsometatarsal joint), proximal phalanx of hallux (metatarsophalangeal joint), medial and lateral sesamoids (metatarsophalangeal joint), and second metatarsal base (intermetatarsal joint).
• Base, Shaft, and Head.
• Significant clinical considerations.

Second Metatarsal

• Longest.
• Articulates with second cuneiform (tarsometatarsal joint), proximal phalanx (metatarsophalangeal joint), first cuneiform (tarsometatarsal joint), third cuneiform (tarsometatarsal joint), third metatarsal base (intertarsal joint), and first metatarsal base (intertarsal joint).
  • Base - Triangular, medial surface: oval facet for first cuneiform, lateral: two facets for third metatarsal.
  • Shaft - Same as common characteristics.
  • Head - Same as common characteristics.

Third Metatarsal

• Intermediate size.
• Articulates with third cuneiform (tarsometatarsal joint), proximal phalanx (metatarsophalangeal joint), second metatarsal base (intertarsal joint), fourth metatarsal base (intertarsal joint), and cuboid (cuneocuboid joint).
  • Base - Triangular, medial surface: two facets for second cuneiform, lateral: facet for fourth.
  • Shaft - Same as common characteristics.
  • Head - Same as common characteristics.

Fourth Metatarsal

• Articulates with cuboid (tarsometatarsal joint), proximal phalanx (metatarsophalangeal joint), third cuneiform (tarsometatarsal joint), third metatarsal base (intermetatarsal joint), and fifth metatarsal base (intermetatarsal joint).
  • Base - Posterior surface: Quadrate, medial: facet for third, lateral: facet for fifth.
  • Shaft - Same as common characteristics.
  • Head - Same as common characteristics.

Fifth Metatarsal

• Articulates with cuboid (tarsometatarsal joint), proximal phalanx (metatarsophalangeal joint), fourth metatarsal base, (intermetatarsal joint).
  • Base - Posterior surface: triangular, medial: facet for fourth, lateral: large and prominent.
  • Shaft - Same as common characteristics.
  • Head - Same as common characteristics.

Phalanges

• Bones that make up the toes.
• The first toe (hallux) has 2 phalanges, other toes have 3.
• Consist of: Base, shaft, and head.
• Proximal, middle, and distal phalanges for each toe.

Constant Sesamoids

• Medial or tibial sesamoid
• Lateral or fibular sesamoid
• Embedded in flexor hallucis brevis tendons and plantar plate.
• Articulate with the inferior surface of the first metatarsal head.

Ossification of Bones

• Ossification times are average values from various studies.
• Females usually ossify faster than males.
• Not uncommon for one foot to develop slightly differently than the other.
• Primary centers typically begin in fetal development, although some appear after birth
• Secondary centers also occur during fetal development but most finalize after birth.

Accessory Bones

• Accessory bones are not part of the normal osteology but are sometimes present in a small percentage of the population.
• The two types of accessory bones are: -Ossicles resulting from anomalous development or ossification -Sesamoids found in tendons and joint capsules to decrease friction.
• Common locations for accessory ossicles on the dorsum: -Os trigonum (talus secondarius) -Os tibiale externum -Os intermetatarseum -Os supranaviculare
• Less common locations for ossicles: -Os paracuneiform
  • Os supranaviculare or talonavicular dorsalis, or calcaneonavicular (dorsal)
  • Os subtibiale
  • Os subfibulare

Part 2 - Arthrology (Joint Classification, Articular Facets, Ligamentous Support, Movements)

• Question areas: Ankle, foot, knee, tibiofibular, pelvis, and hip

Ankle Joint

• Synovial joint formed by the malleolar fork (medial and lateral malleoli of tibia and fibula) and the talar dome.
• Superficial and deep deltoid (medial) ligaments and lateral (anterior talofibular) and (calcaneofibular) ligaments.

Joints of the Foot

• Intertarsal (synovial): Gliding, rotational.
• Functional subtalar (talocalcaneal): Single axis for triplanar motion, allows supination and pronation. -Open kinetic chain (OKC) and Closed kinetic (CKC) aspects of movement.
• Functional midtarsal (transverse tarsal or Chopart's): Calcaneocuboid and talonavicular. Allows simultaneous inversion/eversion and pronation/supination.
• Tarsometatarsal (Lisfranc's): Connects the cuneiforms and cuboid with the metatarsal bases. Provides more mobility at the 1st and 5th tarsometatarsal joints.
• Intermetatarsal: Lesser metatarsal bases articulate with each other.
• Lesser metatarsophalangeal (MPJ): Synovial, biaxial joints where the metatarsals articulate with the proximal phalanges of toes 2-5.
• Hallux metatarsophalangeal (MPJ): Synovial, permits dorsiflexion/plantarflexion movements around a transverse axis, and abduction/adduction around a vertical axis.
• Interphalangeal (IPJ) joints (proximal and distal): Synovial, facilitate only dorsiflexion and plantarflexion.

Knee Joint

• Synovial, biaxial, hinge-type joint between the distal end of the femur and the proximal tibia, and the patella.
  • Synovial membrane: Projects around the cruciate ligaments so that the they are extrasynovial, but superiorly the synovial cavity connects with the suprapatellar bursa.
  • Ligaments:
  • Collateral ligaments (medial and lateral)
  • Cruciate ligaments (anterior and posterior)
• Menisci: crescent-shaped fibrocartilages embedded in the joint, distribute force across the tibial plateau.

Hip Joint

• Ball-and-socket synovial joint combining the head of the femur with the acetabulum of the os coxae.
• Synovial articulation, with a fibrocartilaginous acetabular labrum to deepen the cavity and an articular capsule.
• Ligaments: Iliofemoral, Ischiofemoral, Pubofemoral ; Ligamentum capitis femoris

Sacroiliac Joint

• Synovial joint between the paired auricular surfaces of the sacrum and ilium, allowing for limited movement, chiefly to accommodate the changes in posture and position throughout life.
• Ligaments: Anterior, Posterior, Interosseous sacroiliac.

Miscellaneous Ligaments of the Thigh

• Inguinal, Lacunar, Pectineal, Obturator membrane.

Part 3 – Myology (Muscle Origins, Insertions, Actions; Fascia and Retinacula)

• Question areas: Foot, Leg, Thigh, and Pelvis

Dorsum of the Foot

• Skin
• Deep fascia
• Superior extensor retinaculum
• Inferior extensor retinaculum
• Flexor retinaculum
• Extensor digitorum brevis: Origin, Insertion, Action
• Tendons of extrinsic muscles
• Extensor hood or extensor expansion

Plantar Surface of the Foot

• Skin
• Deep fascia
• First layer of plantar muscles
• Second layer of plantar muscles
• Third and fourth layers of plantar muscles
• Tendons of extrinsic muscles

Muscular Compartments of the Foot

Muscles of the Leg

Anterior compartment of leg muscles

• Tibialis anterior, Extensor hallucis longus, Extensor digitorum longus, Peroneus tertius.

Lateral compartment of leg muscles

• Peroneus longus, Peroneus brevis

Posterior compartment of leg muscles

• Superficial group: Gastrocnemius, Soleus, Plantaris
• Deep group: Popliteus, Flexor digitorum longus, Tibialis posterior, Flexor hallucis longus

Popliteal Fossa

Part 4 - Angiology (Arteries, Veins, and Lymphatics)

• Question areas: Foot, Leg, Thigh, and Pelvis

Superficial Veins of the Foot and Leg

• Great saphenous and Small saphenous.

Arteries of the Foot and Leg

• Dorsalis pedis and Plantar
• Medial, Lateral, Perforating
• Collateral, Cruciate anastomoses arteries of the knee and hip.

Part 5 – Peripheral Nervous System (Lumbar and Sacral Plexuses, Their Cutaneous, Articular, Somatic, Motor and Sympathetic Branched of the Lower Extremity)

• Question Areas: Foot, Leg, Thigh, Hip, and Pelvis • Cutaneous innervation of the lower extremity • Muscular innervation of the lower extremity
• Lumbosacral Plexus (Lumbar and Sacral Portions)
• Lumbar portion: Iliohypogastric, Ilioinguinal, Genitofemoral, Lateral femoral cutaneous nerve, Obturator nerve, Femoral nerve
• Sacral portion: Nerve to quadratus, nerve to obturator internus, nerve to piriformis, Superior gluteal nerve, Inferior gluteal nerve, Posterior femoral cutaneous nerve, Sciatic nerve, Tibial nerve, Common peroneal nerve, Pudendal nerve.

Part 6 - Integument

• Composition
• Thick skin
• Thin skin
• Hypodermis

Part 7 - Limb Development (Limb Bud and Limb Rotation; Pre-axial Versus Post-axial Position and Function)

• Limb Bud Formation
• Limb Bud Structure
• Limb Bud Coordinates
• Mesoderm of Limb Bud
• Limb Differentiation
• Limb Rotation