Palsy of the common peroneal nerve due to a traumatic hematoma within its nerve sheath is described as a complication of spiral fractures of the distal part of the leg. This unusual complication was observed after two skiing injuries. Traction was apparently transmitted along the nerve, from ankle to mid-thigh, where a vas nervorum of the common peroneal nerve was ruptured below the sciatic bifurcation, with a resulting hematoma between the epineurium and perineurium. In neither case was there evidence of direct trauma to the region of the hematoma or of ligamentous injury at the knee. The same condition may result from an inversion sprain of the ankle.

The common peroneal nerve and its branches would appear to be vulnerable to remote torsion injuries of the distal part of the leg and ankle. Severe intractible pain after reduction and immobilization of a fracture of the tibia and fibula may be an important clue to nerve involvement, and should alert the surgeon to investigate for motor and sensory deficits.

In the two cases reported, early exploration of the nerve and its branches with evacuation of the hematoma and ligation of the ruptured was nervorum was followed by swift and dramatic recovery. Awareness of the vulnerability of the vasa nervorum of the commons peroneal nerve near the sciatic bifurcation is important in determining the level for exploration.

It seems likely that some peroneal nerve palsies heretofore attributed to overstretching of nerve fibers or to external pressure from a cast may in fact have been the result of a traumatic hematoma within the nerve sheath. Since irreversible palsies may presumably result from unirecognized traumatic hematomata, it is important to be aware of this entity and to be prepared to evacuate the hematoma promptly.