Nerve function

Nerve injuries should be approached aggressively in open injuries, as there is never a better time to evaluate and to perform repairs. In the context of an adjacent open wound, nerve dysfunction should be considered an open nerve injury until proven otherwise. Partial nerve lacerations are clearly best treated by early repair. If untreated, the nerve heals with a large neuroma, and partial function returns. If such an injury is explored late, it may be impossible to distinguish neuroma from scarred nerve fibers in continuity, and the surgeon may face the no-win choice of either leaving things as they are or performing a segmental complete nerve excision and grafting, possibly leaving the patient worse off than they were prior to surgery.
If a nerve appears injured, but is not explored, nerve studies may not be helpful in distinguishing neuropraxia from more severe nerve injury for several weeks. At that point, conditions may not be favorable for nerve exploration, and it may be reasonable to wait for nerve recovery, assuming that the nerve is injured but in continuity. How long is it reasonable to wait before expecting to see signs of muscle recovery following an in continuity injury? This can be calculated, making a few assumptions: 1) Muscle recovery is poor if motor point reinnervation is delayed past 12 months, and unlikely if delayed past 18 months; 2) Following repair, axon growth proceeds at an average of 30 millimeters per month; 3) That the probable site of the nerve injury is known; 4) That there is no other evidence contrary to the diagnosis of a closed stretch injury. If these assumptions apply, it should be "safe" to wait for distal muscle to s how signs of reinnervation for a period of 12 months minus (distance in millimeters from injury to motor end point divided by 30 mm per month), or 12 - (distance/30) months. Within that time frame, recovery could still be anticipated even if delayed excision and repair is performed. So, for example, in an ulnar nerve injury, if the distance from a forearm injury to the first dorsal interosseous muscle along the course of the ulnar nerve was 180 millimeters, it would be "safe" to wait up to (12 - 180/30 =) six months before the window of opportunity for surgical success began to close.
e-Hand Previous Next Search Chapter Textbook