Manufacture and instrumentation of bio-mechanical shoulder testing rig for medical applications

Manufacture of medical simulations and devices is complex as parameters are often complex and ill-understood. Until recently the accurate measurement of contact loads acting in the Glenohumeral joint have been difficult to calculate and define. Now, contact forces and moments are measured in-vivo using telemeterized Shoulder implants. This method limits testing opportunities so a dynamic Shoulder testing apparatus has been developed to examine Glenohumeral joint motion and forces. This in-vitro study describes a novel testing arrangement and evaluates the accuracy of forces generated in the Glenohumeral joint using an instrumented prosthetic implant. Forces were applied to cables to simulate loading of the supraspinatus, subscapularis, infraspinatus/teres minor, long head biceps and anterior, middle, and posterior deltoid muscles. The test rig described reproduces the 6DOF of the Glenohumeral joint and accurately recreates the contact forces measured in-vivo. This design will allow many more tests to be simulated including comparison of fixation methods and high impact injuries. As a result of the study it will be possible to make recommendations regarding the biomechanical fixation techniques of the proximal Humerus for varying complexities of fracture, differing bone properties and populations in an attempt to find the optimal treatment to suit each individual patient. It also provides a valuable demonstration of new design and validation techniques used when developing medical simulations and devices.