[Noninvasive analysis of cartilage volume and cartilage thickness in the human elbow joint using MRI]

The aim of the study was to non-invasively analyse the cartilage volume and thickness in the human elbow joint with magnetic resonance imaging. 12 fresh frozen specimens (ages 20 to 69 yrs.) were investigated using a 1.5 T magnet, and a water-excitation FLASH-3D sequence at a resolution of 1 x 0.25 x 0.25 mm3. After linear interpolation to 0.125 x 0.125 mm2 in the image plane, the cartilages were segmented interactively with a Snake algorithm. Following three-dimensional reconstruction, the cartilage volumes were determined, and the mean and maximal cartilage thickness computed by Euclidean distance transformation. The total cartilage volume of the human elbow joint amounted to between 3.90 and 7.17 ml (mean 5.5 ml +/- 20%). The humerus occupied 49 to 60%, the radius 15 to 27% and the ulna 20 to 29% of the total volume. The mean cartilage thickness ranged from an average of 0.9 (proximal part of the ulna) to 1.4 mm (capitulum humeri), and the maximal thickness from 2.3 mm (proximal part of the ulna) to 2.9 mm (distal part of the ulna). The ulnar cartilage showed a more inhomogeneous distribution than that of the humerus and radius. The interindividual variability of the cartilage thickness was less than that of the volume. There was no significant relationship of the volume with age (r = 0.11) or body weight (r = 0.51). However, based on the joint size (r = 0.71-medio-lateral extension of the articular surfaces) about 50% of the variability of the total cartilage volume could be predicted. The technique presented is suitable for designing computer models to investigate the load transmission and functional adaptation of diarthrodial joints, and for diagnosing and monitoring joint disease.