Normal glenoid version in nonarthritic shoulders is
between 2 anteversion and 9 retroversion. Finite
element analyses have shown that retroverted glenoid
components in TSR create problematic eccentric contact
forces, especially when retroversion exceeds and
that this off-center loading results in increased tensile and
shear stresses about the cement-bone interface. Clinically,
asymmetric load distribution of the humeral head on
the glenoid can lead to early loosening of the glenoid
component analogous to the ‘‘rocking horse’’ phenomenon
that was originally described in rotator cuffedeficient
shoulders undergoing TSR.15