Manubriosternal joint dislocation in rheumatoid arthritis: the role of thoracic kyphosis

A case report of manubriosternal joint (MSJ) dislocation in a rheumatoid patient with thoracic kyphosis is presented together with a review of the relevant literature. Variations in the anatomical nature of the MSJ between normal individuals are described. In 43% of the population its characteristics are noted to be such that it may be involved in rheumatoid arthritis (RA). A joint thus involved can be dislocated by forces generated by longstanding thoracic kyphosis and transmitted to the manubrium via the first rib. Xeroradiographs of the MSJ region in our patient showed dislocation of the joint in the upright position and its subsequent reduction on lying the patient flat. We suggest that this demonstrated reduction is secondary to the lessening of the thoracic kyphosis that occurs in the supine position. It is concluded that in RA MSJ dislocation is a function of thoracic kyphosis.