Hypothesis testing of glenoid component innovation in total shoulder arthroplasty.

A glenoid component with reliable long-term performance does not exist for total shoulder arthroplasty. The author proposes that glenoid component durability can be improved by preclinical testing eliminating weak designs before continuing to costly clinical trials. The specific mode of investigation pursued in this thesis is "hypothesised-based" research. From the universal statement that glenoid component performance weakens total shoulder arthroplasty, statements of a lesser universality ("hypotheses") regarding glenoid component designs are deduced and tested. A complex geometry, three-dimensional muscle and joint loading, and range of materials exist a the shoulder joint. In addition the joint experiences huge variability depending on the pathology, this makes bench testing problematic, and therefore, the method of three-dimensional finite element analysis is used. With adequate representation of the real situation, three hypotheses on glenoid component design are tested. The results corroborate the hypotheses showing that (i) greater durability to prevent glenoid loosening is provided by a pegged prosthesis in normal bone and a keeled prosthesis in comparison glenoid bone: (ii) an anterior offset keel provides better durability than a centre keel design: and (iii) attachment of the scapular-side component to the acromion may lead to component failure. Clinically significant deductions are then made on the basis of these three hypotheses showing that: Glenoid material property distribution plays an essential role in glenoid component design; it is essential to use good quality bone to its best advantage; removal of bad quality bone and replacement with better quality material, results in a decrease of cement stresses and essentially a lower probability of failure for the implant; remaining good bone is left to provide good support to the prosthesis.