Joint and Cartilage Diagnosis, Assessment and Modeling

Abstract

Methods for assessing the condition of a cartilage in a joint and assessing cartilage loss, particularly in a human knee, are disclosed. In one method, a method for modeling healthy cartilage, the method includes measuring the distance between each of at least two points on an articular cartilage surface corresponding to margins of a defect and a corresponding point on the sub-chondral bone surface, and interpolating a reconstructed cartilage boundary. In a second method, a method for generating a three-dimensional approximation of healthy cartilage, the method includes determining a set of distances between at least three points on a first articular surface corresponding to margins of a defect and at least three corresponding points on a second cartilage surface, and approximating a reconstructed cartilage surface.

1 . A method of modeling healthy cartilage comprising:
 a. obtaining image data representing at least a portion of a defect in cartilage to be assessed;   b. determining from the image data the location of a articular cartilage surface having the defect;   c. determining from the image data the location of a subchondral-bone surface;   d. locating at least two points on the articular cartilage surface approximately corresponding to margins of the defect;   e. measuring the distance between each of the at least two points on the articular cartilage surface and a corresponding point on the subchondral-bone surface; and   f. interpolating, based on the measured distances, a reconstructed cartilage boundary that provides an approximation of the location of the first cartilage surface without the defect in the cartilage.   
     
     
         2 . The method of  claim 1 , wherein the reconstructed cartilage surface is based on a two-dimensional image. 
     
     
         3 . The method of  claim 1 , wherein the second cartilage boundary does not contain a defect. 
     
     
         4 . The method of  claim 1 , wherein the reconstructed cartilage boundary is a three-dimensional surface. 
     
     
         5 . The method of  claim 5 , wherein the reconstructed cartilage boundary is approximated at least in part by summing a set of slices of the image data. 
     
     
         6 . The method of  claim 1 , wherein the reconstructed cartilage surface is a first reconstructed cartilage boundary corresponding to a first cross-sectional view of the joint and further comprising:
 a. generating a second reconstructed cartilage boundary corresponding to a second cross-sectional view of the joint; and   b. creating a three-dimensional reconstructed cartilage surface based on the first and second reconstructed cartilage boundary.   
     
     
         7 . A method of generating a three-dimensional approximation of healthy cartilage comprising:
 a. obtaining three-dimensional image data corresponding to a joint having defective cartilage;   b. determining from the image data the location of a first cartilage surface having a defect;   c. determining from the image data the location of a second cartilage surface;   d. locating at least three points on the first cartilage surface approximately corresponding to margins of the defect;   e. determining a set of distances between each of the at least three points on the first cartilage surface and at least three corresponding points on the second cartilage surface; and   f. approximating, based on the set of distances, a reconstructed cartilage surface that represents the first cartilage surface without the defect in the cartilage.   
     
     
         8 . The method of  claim 7 , wherein the step of determining a set of distances further comprises transforming the image data using, at least in part, a three-dimensional Euclidian distance transform. 
     
     
         9 . A method of assessing a defect in cartilage in a joint comprising:
 a. obtaining image data representing a defect to be assessed;   b. determining from the image data the location of a defective cartilage surface;   c. locating at least two points on the defective cartilage surface approximately corresponding to margins of the defect;   d. creating a current data set based at least in part on the at least two points on the defective cartilage surface; and   e. approximating a characteristic of the defect, based at least in part on the data set.   
     
     
         10 . The method of  claim 9 , wherein the approximated characteristic is the area of the defect. 
     
     
         11 . The method of  claim 9 , wherein the approximated characteristic is the volume of the defect. 
     
     
         12 . The method of  claim 9 , wherein the approximated characteristic is the depth of the defect. 
     
     
         13 . The method of  claim 9 , further comprising comparing the current data set to a previous data set to determine changes in the joint. 
     
     
         14 . The method of  claim 13 , wherein the comparison is made without registering the current data set to the pervious data set. 
     
     
         15 . The method of  claim 9 , further comprising:
 a. determining from the image data the location of a second cartilage surface; and   b. determining a set of distances between each of the at least two points on the defective cartilage surface and corresponding points on the second cartilage surface; wherein the data set is based at least in part on the set of distances.