Impairment evaluation based on spinal range of motion in normal subjects.

Spinal range of motion is a major determinant of impairment in many disability rating schedules used today. The validity of using spinal motion as the primary variable for impairment ratings must be questioned because of the large spectrum of age-related changes in motion in a normal population. The purpose of this investigation was to test the validity of this concept by determining spinal impairment in normal subjects using one of the more popular rating systems, the American Medical Association (AMA) Guides to the Evaluation of Permanent Impairment. Ninety-five individual measurements of cervical and lumbar spine motion were performed on each of 81 healthy subjects by two examiners using the double-inclinometer method. Based on the AMA criteria, all of the normal subjects were noted to have some degree of impairment ranging from 2 to 38.5%, with a mean value of 10.8%. The level of impairment increased with age for cervical, lumbar, and total impairment percentages (p = 0.0001). The current method of impairment determination based on spinal motion may not accurately reflect impairment in many patients. Impairment may be overestimated by up to 38%. Alternate methods of impairment evaluation should be developed that are more specific for individuals with true functional impairment and that account for age-related differences in spinal motion.