Detection of nerve entrapment during limb lengthening by means of near-nerve recording

Eight patients undergoing limb lengthening by the Ilizarov method had near-nerve needle electrode conduction studies when they developed clinical signs of nerve entrapment. The near-nerve technique was chosen because it is highly sensitive to configurational changes which appear in the action potential as injury occurs. In 10 out of 13 symptomatic limbs the near-nerve potential was found to be abnormally small and its usually smooth contour had become notched and irregular. In the remaining 3 limbs the potentials were normal initially but became abnormal as further constriction of the nerve took place. Nerve potentials remained normal in size and shape in asymptomatic limbs undergoing lengthening and were not altered by application of the Ilizarov frames themselves. The near-nerve technique proved useful in the early detection of nerve injury in these patients and thus enabled surgical intervention before nerve damage had become permanent.