The shoulder joint is a “ball and socket” joint. It is formed by the articulation of the humeral head “ball” with the glenoid “socket”. The reverse total shoulder replacement is a relatively new shoulder prosthesis. It is different from the native anatomy of the shoulder and the conventional total shoulder replacement in that the position of the “ball” (humeral head) and “socket” (glenoid) are reversed. The “ball” is positioned on the glenoid and is termed the glenosphere, while the “socket” is positioned on the humeral shaft.
The primary indication for a reverse total shoulder replacement is for rotator cuff arthropathy. This is a condition of progressive arthritic degeneration of the shoulder joint due to longstanding rotator cuff dysfunction as a result of chronic rotator cuff tears within the shoulder. At least two of the four rotator cuff muscles (supraspinatus, infraspinatus, teres minor and subscapularis) need to be torn or dysfunctional in order to develop rotator cuff arthropathy. As a result of the dysfunction, the normal biomechanics of the shoulder joint are lost. The pathologic mechanics of the shoulder joint lead to the eventual development of disabling arthritic change of the shoulder. This condition is termed rotator cuff arthropathy. This prosthesis is ideally suited for the older patient with lower functional demands with significant functional limitations as a result of this condition. Other conditions for which a reverse shoulder arthroplasty can be considered include:
- Failed total shoulder replacement
- Chronic shoulder infection after surgery
- Chronic proximal humerus fracture
Patients with rotator cuff arthropathy will typically present with pain and weakness within the involved shoulder. Often, they may describe a sentinel event such as a fall that led to an initial rotator cuff tear. Patients may have also had a prior rotator cuff repair or a history of multiple repairs. There is often progressive weakness with the most classic symptom being the inability to raise the arm above shoulder level to perform overhead activities. Reaching behind the back is also another activity that becomes progressively more difficult or impossible for the patient to perform. The patient as a result tries to avoid these activites or commonly will use the other arm to position the affected arm in regards to over head activities. Patients commonly will also complain of night pain due to the chronic rotator cuff tears.
The evaluation of a patient with a suspected rotator cuff tear consists of a histyr and physical exam, radiographs, and sometimes an MRI.
Treatment for rotator cuff arthropathy can be most reliably addressed by the use of a reverse total shoulder replacement. This can restore the patient’s ability to position the arm overhead. It relies on the presence of a functional deltoid muscle and utilizes the glenosphere as a fulcrum to raise the arm overhead. The reverse total shoulder replacement procedure is performed as an inpatient procedure with patients typically staying in the hospital for 2 days post-operatively.
Post-operative recovery involves sling immobilization of the operative arm for 6 weeks. Physical therapy only focuses on elbow, wrist and digital range of motion exercises for the first 6 weeks. Patients will then be able to move the shoulder after this time period. Recovery from the procedure typically takes 6-8 months.