A high-accuracy three-dimensional coordinate digitizing system for reconstructing the geometry of diarthrodial joints.

This paper describes the design and performance evaluation of a three-dimensional (3-D) coordinate digitizing system (3-DCDS) for measuring both soft and hard biological tissue. The system incorporates a visible semiconducting laser beam and an X-Y positioning table to directly measure 3-D coordinates that define surface points. Experiments conducted to evaluate the performance of the system showed that it delivers an accuracy of 0.1 microm in the Z-direction and 1.4 microm in the X-Y plane, and an overall system root-mean-squared error (RMSE) of 8 microm on surfaces with slopes of less than 45 degrees . This error is lower than that of previously reported measurement techniques. The 3-DCDS measures 3-D coordinates of surface points uniformly separated by 500 microm in the X-Y plane. Because the 3-DCDS is automated, the coordinates are measured efficiently and the accuracy is independent of operator skill. These highly accurate coordinates can be easily incorporated into nodal values for 3-D finite element models (FEM) of diarthrodial joints. To show the use of the 3-DCDS, the 3-D surface coordinates of human menisci were measured from a cadaver specimen.