Why Reverse?
The reverse ball and socket design has had early success in
restoring shoulder function and relieving pain in patients with a
rotator cuff deficient shoulder1-7 . Shoulder prostheses which were
derived directly from hip replacements, with a constrained ball and
socket, have failed. Hemiarthroplasty, the current standard of care
for this condition, offers only “limited goals” for functional improvement
and only modest improvements in pain 8-11.
Likewise, bipolar
implants, used in an effort to improve stability, have produced
results not significantly better than hemiarthroplasty 12,13.
In the reversed design, the forces in the joint are directed through the center of the glenosphere, converting the centrifugal (outward) forces into centripetal (inward) forces. This in turn creates inherent stability in the reversed design because of the congruency of the humeral socket and glenosphere.