REIDER PART 148

138 Charter 4 Hand and Wrist

Figurę 4-54. A, Assessing wrist extensor strength. B, Resisted extension in a position of ulnar deviation to emphasize extensor carpi ulnaris. C, Resisted extension in a position of radiaJ devia-tion to emphasize extensor carpi radialis longus and brevis.

patients wrist tends to deviate to thc radial sidc whenever the patient attempts to perform active wrist extension.

The primary extensor of the four fingers is the exten-sor digitorum communis. In addition, the index finger and the little finger have their own supplementary extensors, the extensor indicis proprius and the extensor digiti minimi (exten$or digiti ąuinti), respectively. Ali of these muscles are innervated by the posterior interosseous branek of the radial nerve. Complicating the evaluation of the finger extensors is the role of the intrinsic muscles of the hand, the lumbri-cals and interossei. Owing to their insertions at the base of the proximal phalanx and into the dorsal hood of the exten-sor tendon, the intrinsic muscles tend to act as flexors of thc MCP joints but extensors of the interphalangeal joints of the fingers. For this reason, testing the patients ability to extend thc MCP joints against rcsistancc is thc best way to evaluate the long finger extensors by themselves.

Extension of the four fingers is usually tested together bccause tethering among the extensor tendons by the junctura tendinae makes it difficult to extcnd thc long finger and the ring finger if the others are held in flexion. The index finger and the little finger are less tethered bccause they have independent extensors, and they may be tested independently, if desired. To test thc extensor digitorum communis strength, the patients elbow is flexed and thc forearm fully pronated. The patient is instructed to extend the fingers fully at all joints and to retain that position against the examiner^>s attempt to passively flex the fingers. One of the examiner s hands then supports the patients hand while the examiner’s other hand presses downward on the patients fingers in an attempt to flex the MCP joints (Fig. 4-55). The examiner should be carcfi.il to position this hand proximal to thc patient s PIP joints so that extension of the MCP joints is isolatcd. The average exam-iner should be able to break the finger extensor strength of most patients, but moderate resistance should be noted.

Wrist and Finger Flexors

The principal wrist flexors are the flexor carpi radialis and flexor carpi ulnaris. They are assisted by thc long