The Development Of A Measuring System On Contact Stress By Using Pressure-sensitive-film And The Application Of Its In Analyzing Pressure Of Human Joint

Injury or degeneration of human joints associates with change of contact stress in the joints. Joint surgical techniques try to restore or reduce contact stress in abnormal joints. However, there has not been a direct measurement to read both magnitude and contribution of contact stress in human joints. In the present study, a measuring system was developed to measure contact stress of joint using Fuji pressure-sensitive-film, which tested contact force with gray on the film. Contact stress in wrist joint, elbow joint and lumbar facet joints were measured using the present system. Hardware of the measuring system consists of a scanner with high resolution, a computer and Fuji pressure-sensitive-film. Scanner scans Fuji pressure-sensitive-film and transfers image data into computer. Every pixel gradation on Fuji pressure-sensitive-film is transfers into pressure using a custom ~oflware. The study includes two parts. The first part presents how to develop a measuring system of contact stress of joints using Fuji pressure-sensitive-film, including calibration of the system and development of computer program. The optimal set of scanner was analyzed. The curve of gradation-intensity of pressure was obtained. In the computer program, browsing arbitrary size pictures, selecting arbitrary size range, computing pixel, saving templates and data and so on were developed. In the second part, contact stress in wrist joint, elbow joint and lumbar facet joints was measured using the present system. Their conclusions are: 1. Normally about 20% load of the carpus is transferred through the ulna., and the other 800/o is transferred through the radius. The ratio of the load transferred by the ulna is dropped with the section of the transverse part of TFCC. Compared with the intact specimen, after 1/3 section of the transverse part of TFCC, the ratio is not dropped significantly, and after 1/2 or whole section the ratio is dropped significantly. 2. About 55% force of all was transferred through the radial head. Cutting the radial head, the stress is all taken by the humerounlar joint, but the stress at different part of the facet are not the same. The stress at the lateral facet of the humerounlar joint was increased more greatly than that at the medial, and the stress at the middle crest of the olecranon process of unla is not increased significantly. The stress transferred by the radial head is various with the different position of the elbow. When the elbow was extended and the forearm was pronat, the contacted surface of the humeroradius joint was the greatest, and the stress transferred through the radial head is also the greatest. 3. When it is in the flexion position the load of the lumbar minimal joints decreased and the posterior longitudinal ligament extended, thus the pressure of the intervertebral discs is increased significantly. And when it is in the extension position the anterior longitudinal ligament and the anterior fibrous rings extend, whereas the posterior longitudinal ligament is loosen. So as the result the contacted pressure between the minimal joint facet is increased significantly. The intervertebral disks?pressure is also decreased.