Boyer diss 2009 1046..

projects medially to a substantial degree and its medial surface, which probably formed
an attachment point for digital flexors, is oriented mediodistally. Spanning between the
medial epicondyle and the shaft (more proximally) is a strut that encloses a large,
elliptical entepicondylar foramen. The capitulum is separated from the trochlea by a deep
constriction of the articular surface, often referred to as the “zona conoidea.” The
capitulum appears “sub-spherical” as a result of (1) constriction of the zona conoidea and
(2) having a radius of curvature that first increases and then decreases lateral to the zona
conoidea. The lateral edge of the capitulum is marked by a proximodistally running
groove, but the articular surface extends laterally beyond this groove: this articular
region, lateral to the capitulum is referred to as the lateral flange (e.g., Beard, 1989). The
surface of the capitulum faces proximally, anteriorly, and distally but does not continue
onto the posterior surface of the bone. The anterior surface of the humerus, just proximal
to the capitulum, is excavated to form a substantial supracapitular fossa. The humeral
trochlea is mediolaterally narrower than the capitulum. Its radius of curvature increases
medially from the zona conoidea until its medial margin, or “keel” (Szalay and Dagosto,
1980; Beard, 1989), is reached. The posterior and anterior aspects of the trochlea are
roughly equal in the degree to which they are developed. Superior to the trochlea on the
posterior side of the humerus is a noticeable, but fairly shallow olecranon fossa. Medial
to the trochlea on the posterior surface of the medial epicondyle is a dorsoepitrochlear
fossa, for attachment of the ulnar collateral ligament. The rotational axis for the ulna and
radius on the distal articular surfaces, as well as the mediolateral axis of the entire distal
end of the humerus, is rotated lateral to the proximal end by ~30º. Thus, the medial
288