Reversing the position of ball & socket of the shoulder joint(a ball & socket type of joint) when doing total joint replacement is Reverse shoulder Arthroplasty.
A conventional shoulder arthroplasty mimics the normal anatomy of the shoulder: a “cup-prosthesis” fitted into the glenoid, and a “head-prosthesis” is attached to the top of humerus. In a reverse shoulder replacement, the socket and ball(head) are switched. The metal ball is fixed to the glenoid and the plastic cup is fixed to the upper end of the humerus.
Indications:
- Cuff-tear arthropathy
- Massive rotator cuff tear with pseudoparalysis
- Severe inflammatory arthritis with a massive cuff tear
- Failed shoulder arthroplasty:-
->Absence of tuberosities (failed hemiarthroplasty for fracture/nonunion)
->Absence of cuff (failed hemiarthroplasty for cuff-tear arthropathy)
->Instability - Proximal humeral fracture
- Proximal humeral nonunion
- Reimplantation for deep periprosthetic infection
- Reconstruction after tumor removal
- Contraindications:- 1. loss or inactivity of deltoid, 2. Excessive glenoid bone loss-no secure implantation of glenoid component, 3. Younger patients, 4. Surgeon Inexperience- a relative contraindication.
- Biomechanism:- ~Reverse prosthesis works by changing the direction of pull of the deltoid.
~With standard prosthesis, humeral head subluxate superiorly due deltoid contraction in the absence of rotator cuff
~Reverse prosthesis corrects the subluxation by placing the centre of rotation of arm laterally & re-estabilishing a fulcrum around which the deltoid-pull can restore forward elevation.