Stress distribution in the trochlear notch

n 16 cadaver humeroulnar joints, the distribution of subchondral
mineralisation was assessed by CT osteoabsorptiometry and the
position and size of the contact areas by polyether casting under
loads of 10 N to 1280 N. Ulnas with separate olecranon and coronoid
cartilaginous surfaces showed matching bicentric patterns of
mineralisation. Under small loads there were separate contact areas
on the olecranon and coronoid surfaces; these areas merged
centrally as the load increased. They occupied as little as 9% of
the total articular surface at 10 N and up to 73% at 1280 N. Ulnas
with continuous cartilaginous surfaces also had density patterns
with two maxima but those were less prominent, and in these
specimens the separate contact areas merged at lower loads. The
findings indicate a physiological incongruity of the articular
surfaces which may serve to optimise the distribution of stress.