Triangular Fibrocartilage Complex Quiz

The Upper Limb - 2

• The presentation is on the upper limb, specifically the wrist.
• The wrist is a distal joint in the upper limb.
• The hand is the effector segment, enabling optimal prehension.

The Wrist

• The wrist is the distal joint of the upper limb.
• The hand, as the effector segment, positions itself for optimal prehension.
• The carpal bones are listed.

Articular Structures of the Wrist

• The wrist joint has two degrees of freedom.
• The wrist complex consists of two joints:
  • The radiocarpal (RC) joint, also called the wrist joint.
  • The midcarpal (MC) joint
• The radiocarpal joint is between the distal radius and the proximal carpal bones.
• The radiocarpal joint is an ellipsoidal joint with two concavities:
  • A transverse concavity related to adduction and abduction.
  • An antero-posterior concavity related to flexion and extension.
• The concave proximal aspect of the radiocarpal joint consists of the distal radius, coated with cartilage.
• The distal surface of the radius is divided by a blunt ridge into the scaphoid impression (laterally) and the lunate impression (medially).
• The distal aspect of the cartilage-coated articular disc is inserted into the ulnar styloid process, extending anteriorly and posteriorly.
• The base of the articular disc is inserted at the infero-medial ridge of the radius.
• At times the articular disc is incomplete, enabling a communication between the radio-ulnar and radio-carpal joints.
• The carpal bones are joined by interosseous ligaments.
• The proximal surfaces of the scaphoid, lunate, and triquetrum, and their interosseous ligaments are covered by cartilage.
• The pisiform bone, though in contact with the triquetrum, is not part of the radiocarpal joint.

The Mid-carpal (MC) Joint

• The mid-carpal joint is between the proximal and distal rows of carpal bones.
• The proximal surface of the scaphoid has two slightly convex surfaces (one for each carpal bone) and a deeply concave medial facet.
• The distal surface of the lunate has a semilunar cavity for the capitate.
• The distal surface of the triquetrum is concave distally and laterally, related to the proximal surface of the hamate.
• The proximal surfaces of the trapezium and trapezoid are in contact with the scaphoid and the head of the capitate.
• The proximal surface of the hamate is in contact with the triquetrum.
• The carpal bones are connected by interosseous ligaments.

Wrist Ligaments

• The wrist ligaments are grouped into collateral and anterior/posterior ligaments.
• The lateral (radial) collateral ligament (RCL) is attached to the styloid process of the radius and scaphoid, composed of two bands:
  • Posterior band, running from the styloid to below the lateral aspect of the proximal articular surface of the scaphoid.
  • Anterior band, a strong band stretching from the anterior edge of the radial styloid to the scaphoid tubercle.
• The medial (ulnar) collateral ligament (UCL) is attached to the styloid process of the ulna, pisiform, and triquetrum, dividing into posterior and anterior bands inserting into the triquetrum and pisiform, respectively.
• The triangular fibrocartilage complex (TFCC) supports the wrist at the distal radioulnar joint.
• The TFCC functions as a focal point for force transmitted across the wrist to the ulnar side.
• The TFCC inserts into the lunate and triquetrum via ulnolunate, ulnotriquetral, and radio-ulnar ligaments.
• The TFCC also contains a small cartilage pad called the articular disc and a homologous meniscus.
• The TFCC has both palmar and dorsal parts. The palmar parts are the ulnolunate, ulnotriquetral, and radial ligaments. The dorsal part inserts into the lunate and triquetrum via the dorsal radioulnar ligament, the extensor carpi ulnaris, and the UCL.
• The anterior ligament (or ligamentous complex) connects the anterior edge of the distal radius to the neck of the capitate.
• The anterior ligament is divided into two bands:
  • The palmar radiocarpal band.
  • The radiotriquetral band (medially).
• The posterior ligament forms a strap posteriorly and consists of two bands:
  • The dorsal radio-carpal ligament (radio-lunate and radio-triquetral bands).
  • The dorsal intercarpal ligament.
• The radiocapitate ligament runs obliquely, connecting the lateral border of the distal radius' anterior to the anterior aspect of the capitate's neck.
• The scapho-trapezium ligament links the scaphoid tubercle to the trapezium's anterior oblique crest.
• The triquetro-capitate ligament joins the anterior aspect of the triquetrum to the capitate's neck.
• The piso-hamate ligament connects the pisiform to the hamate's hook.

Wrist Movements

• Wrist movements occur around two axes:
  • Transverse axis (flexion/extension).
  • Antero-posterior axis (adduction/abduction).
• In neutral position, flexion/extension & adduction/abduction range is maximal.
• The range of flexion is 85° and extension is 85°.

Muscles of the Forearm

• The forearm contains 17 muscles that cross the elbow joint. Some muscles only act on the elbow joint, while others work on the wrist, with tendons continuing to the wrist, hand, and fingers.
• In the proximal part of the forearm, muscles originate from the medial and lateral epicondyles of the humerus.
• Flexor muscles (anterior compartment) have approximately twice the bulk and strength of extensor muscles (posterior compartment).
• Flexor-pronator muscles are located in the anterior compartment and are separated from extensor muscles by the radius, ulna, and interosseous membranes.
• The tendons of most flexor muscles are located on the anterior surface of the wrist and restrained by the palmar carpal ligament and flexor retinaculum (transverse carpal ligament) which are thickenings of the antebrachial fascia.
• Flexor muscles are arranged in three layers:
  • Superficial layer (pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris).
  • Intermediate layer (flexor digitorum superficialis).
  • Deep layer (flexor digitorum profundus, flexor pollicis longus, pronator quadratus).
  • The superficial layer of the flexor-pronator muscles originates from the coronoid process and medial epicondyle of the humerus and inserts onto the middle portion of the lateral surface of the radius.
  • The superficial flexor muscles include the flexor carpi radialis, originating from the medial epicondyle and inserting on the base of the second metacarpal, and helping to flex and abduct the wrist. Next is the palmaris longus, arising also from the medial epicondyle and inserting on the distal half of the flexor retinaculum and apex of palmar aponeurosis, flexing the wrist and tightening the palmar aponeurosis for hand flexion. Lastly is the flexor carpi ulnaris, also from the medial epicondyle, and inserting on the pisiform, hook of hamate, and fifth metacarpal, flexor and adductor of the wrist.
• The intermediate layer originates from the medial epicondyle (and coronoid process) and inserts onto medial sides of the middle phalanges, flexing the middle phalanges with the same attachment as the superficial layer.
  • The deep layer of flexor-pronator muscle originates from medial and anterior sections of ulna—and extends to the base from the fourth and fifth phalanges and the second and third phalanges—flexing the distal phalanges.
• The flexor pollicis longus originates from the anterior surface of the radius, and adjacent interosseous membrane and inserts onto the base of the distal phalanx of the thumb—flexing the thumb phalanges.
• Lastly, the pronator quadratus originates from the distal quarter of the anterior surface of the ulna and inserts onto the distal quarter of the anterior surface of the radius, pronating the forearm.

Extensor Muscles

• Extensor muscles are in the posterior compartment (extensor-supinator) of the forearm.
• These muscles are organized into three groups:
  • Muscles extending and abducting/adducting the hand at the wrist joint.
  • Muscles extending the medial four fingers.
  • Muscles extending or abducting the thumb.
  • Extensor tendons are held in place by the extensor retinaculum, preventing displacement. They are covered by synovial sheaths reducing friction. The extensor retinaculum attaches to the distal radius and ulna.
• Anatomical organization is superficial and deep layers.
  • Superficial layer: brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, and extensor carpi ulnaris.
  • Deep layer: supinator, extensor indicis, abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis.
  • The brachioradialis arises from the proximal two-thirds of the supraepicondylar ridge of the humerus and inserts onto the proximal end of the lateral surface of the radius. Its function is weak forearm flexion, prominent during a midpronated position.
  • The extensor carpi radialis longus originates from the lateral supraepicondylar ridge of the humerus. It inserts on the dorsal aspect of the base of the second metacarpal and extends/abducts the hand at the wrist joint—being active during fist clenching.
  • The extensor carpi radialis brevis, also from the lateral epicondyle of the humerus, inserts onto the dorsal surface of the base of the third metacarpal and extends/abducts the wrist.
  • Extensor digitorum originates from the lateral epicondyle of the humerus—inserting into the distal phalanges of the medial four fingers—extending these fingers primarily at the metacarpophalangeal joints, secondarily at the interphalangeal joints.
  • Extensor digiti minimi originates from the lateral epicondyle of the humerus and inserts onto the distal phalanx of the fifth digit—extending the fifth digit at the metacarpophalangeal joint, with secondary extension at the interphalangeal joint.
  • The extensor carpi ulnaris arises from the lateral epicondyle of the humerus and posterior border of the ulna—inserting on the dorsal aspect of the fifth metacarpal—extending and adducting the wrist during fist clenching.
  • Deep layer muscles: the supinator, originating from the lateral epicondyle of the humerus, radial collateral and anular ligaments, and crest of the ulna inserting onto the lateral, posterior, and anterior surfaces of the proximal part of the radius—supinates and rotates the forearm. The extensor indicis originates from the posterior surface of the distal ulna and interosseous membrane—inserting into the distal phalanx of the second digit, extending the second digit, and assisting in extending the hand at the wrist. The abductor pollicis longus originates from the posterior surfaces of the proximal ulna, radius, and interosseous membrane—inserting onto the base of the first metacarpal—abducting the thumb and extending it at the carpometacarpal joint. The extensor pollicis longus arises from the middle third of the ulna and interosseous membrane, attaching at the base of the distal phalanx of the thumb— extending the distal thumb phalanx and involving the interphalangeal and carpometacarpal joints. The extensor pollicis brevis originates from the posterior distal radius and interosseous membrane, attaching to the dorsal aspect of the base of the proximal phalanx of the thumb, extending the proximal thumb phalanx at the metacarpophalangeal joint and involving the carpometacarpal joint.

Hand

• The hand is the effector organ of the upper limb. It supports the limb mechanically and enables optimal positioning for actions.
• The hand contains 5 metacarpal bones, with the first metacarpal articulating proximally with the trapezium. The other 4 metacarpals articulate with the trapezoid, capitate, and hamate.
• The hand has 14 phalanges.
• The hand's ligaments:
  • At the CMC joint, the volar plate is part of the joint capsule—limiting extension and restricting radial and ulnar motion; hyperextension is possible due to the plate's proximal attachment.
  • At interphalangeal joints, the volar plate limits extension.
• Radial & ulnar motion is restricted by the collateral ligaments.
• Hand muscles are classified into intrinsic and extrinsic groups.

Extrinsic Extensors

• The extrinsic extensors of the hand are supplied by the radial nerve.
• They include 3 wrist extensors and a large group of thumb and digit extensors.
• The main wrist extensors are the ECRB, ECRL, and ECU.
• Extension of the digits is due to extensor digitorum communis, extensor indicis proprius, and extensor digiti minimi.
• Extension of the thumb involves the abductor pollicis longus, extensor pollicis brevis, and extensor pollicis longus.

Extrinsic Flexors

• The hand has 3 wrist flexors and a larger group of thumb and digit flexors.
• The major wrist flexors include the flexor carpi radialis, flexor carpi ulnaris, and palmaris longus.
• The digital flexors include the flexor digitorum superficialis, flexor digitorum profundus, and flexor pollicis longus.

Intrinsic Muscles

• Intrinsic hand muscles are located entirely within the hand.
• They are grouped into 4 compartments: thenar, adductor, hypothenar, and lumbricals.

Thenar Muscles

• The thenar muscles enable thumb movements like abduction, flexion, opposition, and adduction.
• They include the abductor pollicis brevis, flexor pollicis brevis, opponens pollicis, and sometimes the adductor pollicis.

Hypothenar Muscles

• Hypothenar muscles facilitate little finger movements including abduction, flexion, opposition, and adduction.
• They consist of the palmaris brevis, abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi.

Lumbrical Muscles

• Four lumbrical muscles contribute to the flexion of the metacarpophalangeal (MCP) joints and extension of the proximal interphalangeal (PIP) joints.

Interossei Muscles

• The interossei muscles, divided into palmar and dorsal groups, control finger adduction and abduction.
• The palmar group is responsible for adduction, while the dorsal group handles abduction.

Test your knowledge on the anatomy and functions of the triangular fibrocartilage complex (TFCC) in the wrist. This quiz covers key ligaments, their contributions, and roles within the complex. Perfect for students of anatomy and orthopedic studies.