[Anterior joints of the thoracic cage]

The chondro-sternal, interchondral, costo-chondral joints and the upper and lower sternal joints were studied in the thorax of 60 children and human adults. Chondro-sternal joints occur as frequent symphyses in the 5th, 6th and 7th joints or ellipsoid joints which are mainly found in the 2nd, 3rd and 4th joints. Diarthrosis frequency increases with age in every joint. An articular space appears particularly in the lower part of the 2nd, 3rd and 4th joints; in fewer cases a space is found in the upper part of the 5th, 6th and 7th joints. These partial spaces disappear with age and are replaced by spaces occupying the whole articulation. The first joint is a synchondrosis which does not vary with age. Interchondral joints are diarthrodial or trochoid joints from earliest childhood and their frequency increases with age. No direct articular contact was observed between the 9th and 10th costal cartilages. Costo-chondral joints are synarthrosis. The upper sternal joint, which is a synchondrosis in the child, may develop into a non-synovial cavity with age, or even turn into synostosis. The lower sternal joint is a synchondrosis which develops partially towards synostosis.