Student Presentation -- Hema Sulkar
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Ph.D. Research Proposal, Thursday April 19, 2018 -- Kinematics and Biomechanics of the Reverse Total Shoulder Arthroplasty (rTSA)

WEB 3780 - Evans Conference Room, 2:00 pm

Speaker: Hema Sulkar. Advisor: Dr. Heath Henninger


Abstract:

The reverse total shoulder arthroplasty (rTSA) is a joint replacement surgery where the ball and socket components of the joint are "reversed". The unique design allows the deltoid muscle to provide mobility and stability in presence of a compromised rotator cuff. rTSA was originally recommended for patients with rotator cuff tears and arthritis presenting with pain and sever loss of range of motion (ROM). Since FDA approval in 2003, utilization of rTSA is growing accounting to expansion of indications, aging population and use in younger patients (as young as 34). While other outcomes are generally positive, ROM outcomes are highly variable. Increases in abduction by 30 degrees to 180 degrees and changes in external rotation from loss (-60 degrees) to full recovery (90 degrees) have been reported. The causes of such high variability in outcomes are unclear. Recovery dependent kinematics leading up to maximum ROM plateau (first year after surgery) have not been studied. Additionally, reported increases in scapular motion contributions post-operatively beyond 2 years compared to healthy individuals indicate a shift from normal scapular kinematics. The effects of contributions from musculoskeletal adaptations and rTSA implant design and the progression of these changes during early recovery are unknown.

We will use in vivo and in vitro approaches to increase understanding of effects of the non-anatomic intervention. To study the changes in vivo, we will measure longitudinal 3D kinematics of rTSA patients from pre-operative to 1-year post-operative. This will allow us to study progression of anatomical adaptations during early recovery and their influence on ROM. We predict that increased scapular contributions are largest post-operatively and decrease as recovery progresses. To separately analyze effects of musculoskeletal adaptations and rTSA surgery, we will simulate human motions in vitro using a biomechanical simulator. We will develop and validate a dynamic scapula shoulder simulator that will allow recreation of human motions with accurate humerus to scapula relationships. We predict that the altered motion kinematics resulting from musculoskeletal adaptations after rTSA will cause a greater increase in intrinsic shoulder muscle force efficacy compared to the rTSA implant. Findings from this research will improve understanding of the effects of the non-anatomic intervention on structural and functional changes in the shoulder joint. In the future, this information could refine physical therapy and rehabilitation protocols to provide targeted treatment to rTSA patients.