Last-Ditch Option for Restoring Shoulder Function

A novel prosthesis design reverses the position of the standard ball-and-socket shoulder design, enabling reconstruction even if the rotator cuff is torn beyond repair.

The Reverse shoulder prosthesis modifies the normal position of the shoulder's ball and socket, putting a metal (titanium) stem topped with a plastic cup where the head of the humerus was positioned, and on the other side, putting a metal plate and partial sphere (glenosphere) where the depression of the glenoid cavity on the scapula is situated. According to design engineers, this reversal changes the center of rotation within the joint, making the new head of the prosthesis inherently stable, regardless of the health of the rotator cuff.

With the reverse design, good glenoid bone quality is mandatory, since it must hold the screws anchoring the plate that holds the metal glenosphere. A functioning deltoid muscle is also important since the new prosthesis depends upon this muscle for its arm-lifting power. The rehabilitation program with a reverse shoulder is similar to that with an anatomic shoulder design, but it often can begin sooner, since the shoulder's more innately stable design is less dependent on the health and healing of surrounding tissues. However, the reverse shoulder procedure is not an ideal solution. The design puts a higher than normal load on the glenoid anchoring screws and with repeated stress, can become loose and cause premature failure. The Reverse shoulder prosthesis is a product of Encore Medical (Austin, TX, USA).

"When we replace a shoulder joint, it's normally with a traditional, anatomically shaped design,” said Joseph P. Iannotti, M.D., Ph.D., chairman of the department of orthopedic surgery at the Cleveland Clinic (OH, USA). "But this design only makes sense if the tears in your rotator cuff are repairable.”


Related Links:
Encore Medical
Cleveland Clinic