Pressure erosions of bone in rheumatoid arthritis: A subject review

Pressure erosions develop as a result of a variety of different diseases but are most commonly found in persons with rheumatoid arthritis. A combination of pathophysiologic mechanisms is responsible for the erosions. Joint effusions result in increased intra-articular pressure and stretching of joint restraints. Inflammation contributes to laxity of the periarticular supporting structures resulting in malalignment and abnormal contact between bones. Osteopenia weakens the bone. The action of abnormally aligned muscular forces results in bone-on-bone pressure. Given the possible pathophysiologic mechanisms creating pressure erosions in rheumatoid arthritis, several characteristics are evident. Pressure erosions develop because the bone is inherently weakened to the point that pressure resorption cannot be resisted. They are distributed according to malalignments where bone rubs against bone, a situation caused by soft-tissue laxity due to the disease itself. Finally, pressure erosions differ from marginal erosions in that pressure erosions are a biomechanical phenomenon mediated through bone resorption, whereas marginal erosions are the result of direct bone destruction by hypertrophic synovium and pannus formation.