Histopathology of the palmar beak ligament in trapeziometacarpal osteoarthritis

Eighteen cadaver hands were studied to investigate the relationship between degeneration of the palmar beak ligament and articular disease of the trapeziometacarpal joint. Eight of 18 joints had chondromalacia alone; 10 contained areas of eburnation in the palmar aspect of the joint. Beak ligament degeneration correlated closely with the presence of articular degeneration; all joints with eburnation demonstrated frank detachment of the ligament from its metacarpal insertion site. Histologically, the collagen fibers of the beak ligament were disorganized at the metacarpal attachment. The normal insertional zone of fibrocartilage was often unrecognizable on the metacarpal side and, in more degenerative specimens, an intervening synovial recess appeared at the palmar beak of the metacarpal. The trapezial insertion of the beak ligament showed no degenerative change. Increasingly severe cartilage disease was associated with progressive and selective degeneration of the collagen framework of the beak ligament at its insertion onto the thumb metacarpal. These localized histopathologic findings further support the existence of an anatomically distinct intra-articular beak ligament essential to the normal function of the trapeziometacarpal joint and suggest an etiologic relationship to osteoarthritic disease.