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

This quiz serves as a study guide specifically for the anatomy of the lower extremity, focusing on osteology. Key areas covered include the bones of the foot, leg, thigh, and gluteal region. Ideal for students preparing for the NBPME Part I exam.