Mechanical testing of shoulder and elbow implants

The upper limb undergoes a large range-of-motion (ROM); and therefore, the mechanical testing techniques for the corresponding joint implants need to reflect these movements.The literature shows that aseptic loosening and implant instability are the main shoulder implant related reasons for revision surgery. Aseptic loosening occurs when excessively high stresses lead to degradation of the articular surface of the implant component, resulting in generation of wear debris and implant instability that is mostly caused by eccentric loading. Therefore shoulder implant testing generally falls under two different testing modes: wear testing and stability testing.Both anatomic and reverse type shoulder implants have been tested using a variety of different testing regimes including static and dynamic as well as constant loading, variable loading, and physiological loading.There are currently no standard mechanical testing protocols available for Elbow implants, with only a few reports of varus-valgus laxity test methods found in the literature.