The distal humerus: A structure with two pillars

Abstract

Anatomical examination of the distal end on the human humerus, brings a new perspective on its morphology and proves the asymmetry of the two pillars. The lower extremity of the humerus is considered as a structure with two diverging columns which extend the diaphysis and flank the trochlear mass articulated with the ulna. Examination of two series of dry humeri, one of 100 and the other of 20, permits a biometrical study of the pillars. The posterior width of the columns, their antero-posterior dimensions, the angle that they form with the posterior longitudinal axis of the diaphysis, are measured on dry bones, using radiographs and by posterior tracings. The series of twenty dry humeri were then sectioned in several directions. Lastly a series of cuts of frozen elbows were made. These three methods show that the two pillars are different in form. The lateral column is thick, quadrangular, convex at the back, wide and almost vertical; in front it bears the condyle, while a lateral facet appears on its distal part; it is a column articulated with the radius and which extends down to the thumb column. The medial column is fusiform, narrow, oval in every section, concave at the back and almost horizontal; it is a muscle bearing column. The asymmetry of the pillars interests the orthopaedic surgeon in respect of bone formation after fractures and the anthropologist for comparison with the distal humerus of the hominidae and the other primates.