The objective of this clinical study is to evaluate the safety and efficacy of the Encore Reverse Shoulder Prosthesis (RSP). The clinical results of the RSP will be compared to clinical results published in literature for rotator cuff arthropathy and salvage procedures.

• Rotator Cuff Arthropathy
• Failed Total Shoulder
• Failed Hemi-Arthroplasty

• Experimental: Primary shoulder
• Experimental: Revision shoulder

Inclusion Criteria:

• Irreparable rotator cuff or failed hemi or total shoulder arthroplasty with irreparable rotator cuff
• Evidence of upward displacement of the humeral head with respect to the glenoid
• Loss of glenohumeral joint space
• Functional deltoid muscle
• Patient is likely to be available for evaluation for the duration of the study
• Visual Analog Pain Scale 5 or greater

Exclusion Criteria:

• Non functional deltoid muscle
• Active sepsis
• Excessive glenoid bone loss
• Pregnancy
• Neurological abnormalities, which could hinder patient's ability or willingness to follow study procedures. For example, any that may restrict physical activities such as Parkinson's, Multiple Sclerosis, or previous stroke, which affects upper extremity.
• Mental conditions that may interfere with ability to give an informed consent or willingness to fulfill the study requirements (i.e., severe mental retardation such that the patient cannot understand the informed consent process, global dementia, prior strokes that interfere with the patient's cognitive abilities, senile dementia, and Alzheimer's Disease.
• Prisoners
• Conditions that place excessive demand on the implant (i.e. Charcot's joints, muscle deficiencies, refusal to modify postoperative physical activities, skeletal immaturity).
• Known metal allergy (i.e., jewelry).
• Visual Analog Pain Scale <5.