ABSTRACT
The extrinsic muscles that extend the hand and fingers enter the wrist through six synovial-lined, dorsal compartments covered by the extensor retinaculum (Table 89.1). The extrinsic muscles o f extension are innervated by the radial nerve. At the wrist, the tendons are surrounded by a sheath, but this sheath is not present in the hand and fingers. The four fingers are extended by EDC; however the com munis tendon to the little finger is present only 50% of the time. The index and little fingers also have independent extensor muscles-EIP and EDM , respec tively. These tendons usually lie ulnar and deep to the communis tendons to these two fingers.
