Presentation
Extensive cuff deficiency in a patient with a ‘‘pseudoparalytic’’ painful shoulder.
Patient Data
Narrowing of the acromiohumeral interval because of a massive rotator cuff tear (classified as Hamada grade 4B). There are also surgical outcomes of refixation of a torn supraspinatus tendon with 3 bone anchors.
This patient is an ideal candidate for reverse total shoulder arthroplasty.
Prosthesis reverses the orientation of the shoulder joint by replacing the glenoid fossa (socket) with a glenosphere (ball), and the humeral head with a shaft and concave cup.
Elevation torque in the Paul-Marie Grammont reverse total shoulder arthroplasty is increased because of a medialized and lowered center of rotation (L2 x F2 > L1 X F1). The lever arm distance (L) is increased and deltoid force (F) is increased by lowering and medializing the center of rotation. Elevation torque (FxL) in abducting the arm is increased. Deltoid tension is increased on lifting and lowering the arm with joint compression and a gain of 105° in elevation. Medialising the center of the rotation recruits more of the deltoid fibers for elevation or abduction. The rotation center located on the glenoid surface protects it against excessive shearing forces.
Case Discussion
The reverse total shoulder arthroplasty is a treatment for patients requiring a shoulder replacement for osteoarthritis of the shoulder associated with:
complex fractures
the revision of a previously failed replacement in which the rotator cuff tendons are deficient or absent
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