PRIMARY NERVE LESIONS IN INJURIES OF THE ELBOW AND WRIST

1. Primary ulnar palsy in elbow injuries has the same pathogenesis as delayed ulnar palsy, in that it is produced by traction in cubitus valgus deformity.

a. It is relatively frequent in outward dislocation but not in backward and outward dislocations. It is most common in outward dislocation with displacement of the internal epicondylar epiphysis into the joint, because in addition to having been stretched, the nerve is now kinked or twisted at the joint level.

b. Injuries of the internal epicondyle are only associated with primary ulnar palsy when they have been produced indirectly by traction. Contusion injury is rare.

c. In supracondylar fractures, forward and outward displacement of the distal fragment is necessary for primary ulnar palsy to arise by traction over the fractured margin.

2. Primary musculospiral and median palsies in elbow injuries are due to traction in backward displacements. They are not serious in backward dislocations, but frequently require exploration in supracondylar fractures.

3. Primary ulnar palsy in wrist injuries rarely arises by traction, because the nerve has free mobility, but sometimes complicates severe displacements of the lower radial epiphysis when the injury is due to contusion by the radial diaphysis.

4. Primary median palsy in wrist injuries is rarely due to fractures of the lower end of the radius, because the nerve is protected by the pronator quadratus, but is frequently due to forward dislocation of the carpal semilunar bone.

Dislocations of the semilunar seen within seven days should be reduced by manual, but not by instrumental manipulation; if seen within eight weeks, they should be reduced by a non-traumatizing operation; if not seen until later than this, the bone should be excised.

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