PRECISION AND ACCURACY OF BONE LANDMARKS IN CHARACTERIZING HAND AND WRIST POSITION

Characterization of the motion of the hand and wrist requires referenc e to the underlying bones which, for three-dimensional analyses, are a ssumed to be rigid bodies. Stereoradiogrammetric techniques involving the identification of prominent bone landmarks have been used as the s tandard against which surface markers used for in vivo testing have be en evaluated The precision and accuracy with which the 3D positions of bone landmarks in the hand and wrist could be determined was evaluate d in a small inter-observer and inter-cadaver study and compared to th e precision and accuracy with which implanted lead markers could be lo cated. A subset of landmarks suitable for evaluating wrist and metacar pal-phalangeal joint motion was identified; the mean precison for iden tifying these points was better than 1.1 mm in all hand positions with a mean inter-observer accuracy of 2.3 mm. These values show that the average uncertainty in locating bone landmarks is at best roughly twic e that for implanted markers.