Bộ máy bên trong bao gồm các cơ interosseus lưng, interossei volar, và lumbricals. Bốn lưng interossei chèn vào 89 phalanges gần và bắt cóc các ngón tay và yếu flex đốt gần. Ba volar interossei không gắn vào xương nhưng thay vì chèn vào các ban nhạc bên đoàn kết với phiếu bên của các gân duỗi. | 534 Practical Plastic Surgery Figure . The extensor tendon mechanism. Intrinsic Musculature 89 The intrinsic apparatus includes the dorsal interosseus muscles the volar in-terossei and the lumbricals. The four dorsal interossei insert onto the proximal phalanges and abduct the fingers and weakly flex the proximal phalanx. The three volar interossei do not attach to bone but rather insert onto the lateral bands that unite with the lateral slips of the extensor tendons. They adduct the fingers and flex the PIP joint. The lumbricals arise from the tendon of FDP on the palmer side and insert onto the radial lateral band of each finger. They primarily extend the IP joints and function as flexors of the MP joints. The intrinsic muscles are innervated primarily by the ulnar nerve except for the first and second lumbricals which are innervated by the median nerve. The intricate extensor flexor and intrinsic systems are interconnected aligned and stabilized with a system of ligaments found in each finger. The triangular transverse retinacular and oblique retinacular ligaments perform a variety of complex actions. The pathology of these ligaments is addressed in the chapter on Dupuytren s disease. A detailed discussion of their functions is listed at the end of this chapter see Suggested Reading . Blood Supply The extensor tendons are supplied by a number of sources. Vessels from the muscles and bony insertions travel distally and proximally respectively down the length of the paratenon. The dorsal aspect of the tendon is not as well vascularized as the deeper surface which receives branches from the periosteum and palmar digital arteries. Unlike the flexor tendons the extensors have no vincular system. Synovial diffusion plays a major role in the delivery of nutrients less so than in the flexor tendon system. Extensor Tendon Injuries 535 Figure . The zones of extensor tendon injury in the fingers and hand. Zones of Injury The dorsum of the fingers hand and wrist can
