Full-field strain distribution in non-arthritic and arthritic glenoid bones before and after implant placement measured by digital volume correlation method

Loosening of the shoulder joint (glenohumeral joint) implant is a leading cause of failure in total shoulder replacement surgery, primarily due to mechanical strain concentration in the bone. This study combines in situ mechanical testing with micro-X-ray computed tomography (micro-CT) to apply physiologically realistic loads on non-arthritic and arthritic glenoid bones, the socket portion of the shoulder joint, before and after implant placement, and uses digital volume correlation (DVC) to analyze 3D deformation and strain distributions within the glenoid bones. The results show that degenerative changes in bone quality and structure associated with different arthritis subtypes redistribute strain under anterior and posterior eccentric loading. Strain distributions were compared across arthritis subtypes before and after implant placement, with results indicating that implant placement often helps alleviate strain concentrations. Additionally, the percentage of bone volume experiencing strain beyond the physiological strain range typically encountered during daily activities was assessed. While the proportion of bone exceeding this strain threshold was comparable between non-arthritic and arthritic glenoid bones post-implantation, strain magnitude was notably higher in arthritic specimens, potentially increasing the risk of implant loosening. These findings provide insights for optimizing preoperative planning and implant design tailored to patient-specific bone characteristics, potentially enhancing implant longevity and reducing the risk of post-surgical loosening in patients with glenohumeral arthritis.