Accessory Structures of the Hand

Extensor retinaculum attachments

Radius, ulna, pisiform, triquetrum, ulnar collateral ligament

Septa of extensor retinaculum

Run to the carpal bones and form separate tunnels for extensor tendons

Extensor retinaculum functions

Prevents bowstringing and protects underlying structures

Flexor retinaculum attachments

Scaphoid and trapezium to pisiform and hamate

Flexor retinaculum function

Prevents bowstringing, protects underlying structures, converts anterior concavity of bones into carpal tunnel - forms anterior boundary of tunnel, provides attachment for six muscles

Carpal tunnel

Fibro-osseous tunnel at wrist that allows passage for nine tendons and median nerve, floor and walls made of carpal bones, roof from flexor retinaculum

Tendons in carpal tunnel

Four flexor digitorum superficialis, four flexor digitorum profundus and one flexor pollicis longus - tendons of fds have common tendon sheath and tendons of fdp have common tendon sheath

Carpal tunnel syndrome

Compression of median nerve in carpal tunnel

Palmar aponeurosis

Triangular shaped sheet of fascia that extends from flexor retinaculum to deep transverse metacarpal ligaments

Function of palmar aponeurosis

Protects underlying vessels and nerves, anchors the skin, aids in grip

Intertendinous connections

Fibrous connections between bands of extensor digitorum muscles just proximal to mcp joints

Function of intertendinous connections

Prevents independent extension of any one finger and ensures hand opens as a unit when releasing grip

Dorsal digital expansion

Forms an aponeurosis over posterior surface of each finger, receives attachment from extensor digitorum, lumbricals and interossei

Function of dorsal digital expansion

Ensures simultaneous extension of interphalangeal joints in each finger when releasing grip

Fibrous flexor sheaths

Fibro-osseus tunnels for flexor tendons in the digits, bone posteriorly and fibrous sheath anteriorly - wraps from bone around synovial tendon sheath

Functions of fibrous flexor sheaths

Acts as pulleys for flexor tendons - binds them to bone and prevents bowstringing within digits, increases leverage and efficiency

Synovial flexor sheaths

Surround each tendon as it passes under fibrous sheath, double layered tube

Function of synovial flexor sheaths

Allows friction free gliding of tendon under fibrous sheath

Snuff box

Anatomical space that contains radial artery, ventral boundary is epb and apl, dorsal boundary is epl, floor is scaphoid bone