Neurology Edited by Professor Emeritus Desire' Dubounet, IMUNE

Example: If the metacarpophalangeal joint moves from 0° extension to90° flexion, then V flex, = 90° and V ext = 0°. In this case, 90° is also thelargest theoretical Vflex, and 0° the smallest theoretical Vext.When joint flexion is decreased, F (loss of flexion) =(largest theoretical Vflex)- (measured Vflex).Example: If the metacarpophalangeal joint has 60° flexion, F = 90° -60° = 30°.Similarly, the E (loss of extension) =(measured Vext) - (smallest theoretical Vext).Example: If the metacarpophalangeal joint has -20° extension,E = 20° - 0° = 20°.With decreasing flexion and extension, Vflex and Vext will finally meet at thesame point on the arc of motion, or Vflex = Vext . When this occurs, thereis ankylosis, or total loss of potential arc of motion.ThereforeA (Ankylosis, or total loss of motion) = E (loss of extension) + F (loss offlexion), or A = E + FExample: If the metacarpophalangeal joint has 40° ankylosis in flexion:Vext = Vflex = 40°; E = 40°; F = 90° - 40° = 50°; A = 40° + 50° = 90°.Note that A always equals the normal, full range of motion of the joint.Furthermore, impairment of finger motion can be caused by a loss ofextension (E), with or without loss of flexion (F), or ankylosis (A). Therestricted motion impairment percentages are called IE%, IF%, and IA%,respectively, and are functions of the angle (V) measured at examination.IE is a function of Vext and is 0% when Vext reaches its smallesttheoretical value.IF is a function of Vflex and is 0% when Vflex reaches its largesttheoretical value.