CHAPTER 18 : The Joints of the wrist , hand and fingers

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Fibrous and Synovial Flexor sheaths

  • Fibrous flexor sheaths form tunnels for digital tendons. Each tunnel holds the deep and superficial flexor tendons except the pollex where the tunnel contains only the flexor pollicis longus.

  • The sheaths are alternately dense (annular pulleys) and lax (cruxiform pulleys) along the fingers.

  • Tendons within the carpal tunnel are invested with synovial sheath that extend proximally about 3cm in lower part of the forearm.

  • Tendon of superficialis and profundus are enclosed together in a sheath incomplete on the radial side

  • This common sheath is only extended to the terminal phalanx of the small digit

  • The sheath ends beyond the flexor retinaculum for the index, ring and middle finger. However a separate synovial sheath lines the fibrous flexor tunnels.

  • The tendon of flexor pollicis longus has its own sheath that continues from the carpal tunnel to the distal phalanc of the pollex. These sheaths communicate with the common sheath for the profundus and superficialis in about 50% of individuals.