Prosthetic design considerations in total shoulder arthroplasty.

Total shoulder replacements should, as far as possible, be designed after normal anatomy. A small mismatch in curvature between the humeral head and glenoid surfaces may reduce edge loading when the humerus translates on the glenoid, but may increase contact stresses caused by point loading. Modularity increases sizing options but decreases head size for a given soft-tissue space and introduces the risk of component dissociation. Releases and soft-tissue balancing at surgery, and rehabilitation afterwards, are more important than the type of glenohumeral prosthesis implanted.