LHRD_LoadingApparatus
Development of an Automated Test Bed to Assess the Performance of Shoulder Implants
Presenting Author: David E. Cunningham
Contributing Authors: Dr. George Athwal, Dr. Jim Johnson
Description
The design and assessment of orthopaedic implants for the replacement of the diseased shoulder is an important process in the development of these implant systems. We have developed a specialized test-bed that assesses the fixation and stability of implants relative to bone. This employs high resolution machine-vision cameras to quantify implant stability, and a specialized loading protocol based on published clinical loading data collected via instrumented implants (Figure 1). We have the ability to quantify bone-implant fixation (viz. micromotion) to an accuracy of less than 10 microns. With respect to the loading protocols, we have found that the use of anatomically relevant loading states produces a much more robust testing approach (Figure 2) relative to the currently used techniques which employ simply planar force loading scenarios. The system is standalone which allows us to assess and implant design for a wide sequence of loading states before replacing the specimen with a subsequent implant and repeating the extensive loading protocol. All data collected by the new system is synchronized with the loading input values and exported for easy statistical analysis (Figure 3). An image of the final 3D loading apparatus is visible in Figure 4.
Custom Loading Apparatus and Digital Micromotion Tracking System
Figure 1: The plot above shows the 3D loading apparatus and an image acquired using one of the (3) high-resolution digital cameras, focused on the bone-implant interface.
3D Loading Plot of (Left) Humerus during Clinically-Relevant Motions
Figure 2: Varied Anatomical Loading Profiles on a 3D Humeral Model. This interactive plot of the left humerus shows the variation of loading vectors that are applied to the glenohumeral articualtion during everyday activities. Please note that if this plot is being viewed on a phone you may have to rotate the screen to a landscape orientation for the best viewing experience.
Custom Python-Based Desktop Application
Figure 3: The image and video above show the custom Python-Based controller software created for control of the triaxial loading apparatus and syncrhonized data colleciton.
Loading Apparatus 3D Model
Figure 4: 3D loading apparatus 3D model. This interactive 3D plot shows the rendered SolidWorks design of the loading apparatus. Please note that the rendering may take a minute or two to load, and must be viewed in landscape orientation if viewed on a phone.