Alterations in stress distribution patterns through the forearm joint surface of the elbow in baseball players...

The distribution of subchondral bone density well reflects long-term resultant stress acting on an articular surface in living joints. Consequently, a measurement of the distribution pattern can determine the stress distribution across the elbow joint surface under long-term loading conditions of baseball pitching. Our purpose was to elucidate the characteristic alterations in the distribution pattern of subchondral bone density across the forearm bones of the elbow with pitching activities. The hypothesis is that pitching activities would change the stress distribution in living subjects.

The analysis was performed using computed tomography (CT) images obtained from the dominant elbow of ten nonthrowing athletes (control group), ten college baseball fielders (fielder group), and ten college baseball pitchers (pitcher group). The distribution pattern of subchondral bone density through the articular surface of the proximal radius and ulna bones was assessed using CT osteoabsorptiometry.

The maximum density area was located in the posterior part of the trochlea notch in all study participants. This maximum density area was significantly increased in the baseball groups compared with that in the control group. The pitcher group also showed a significant distribution of the maximum density area in the anterior part of the radial head.

Our analysis indicates that pitching activities increase actual stress on the articular surface not only in the posterior part of the trochlea notch but also in the anterior part of the radial head. The stress across the elbow may be expanded from the ulnohumeral to the radiohumeral joint by repetitive pitching activities in living subjects.