Week 2: Beginning Research Project - Ben Johnston

Hi everyone, this is Ben Johnston, working with Dr. Mike Fu at HSS this summer. This week I met with my mentor and discussed my shadowing outlook for the summer and also which of the three projects I outlined in my last post I would like to take on. We also had an interactive meeting with the program leaders (Dr. Min and Dr. Prince) regarding imaging techniques/analyzing radiographs. I haven't interacted with many of the imaging modalities we reviewed since a class I took a few years ago during undergrad, so this was a nice refresher and confidence boost that I recognized most of the anatomical structures.

I have decided to pursue the finite element modeling (FEM) project I mentioned in my week 1 post. To recap, this project is centered on using FEM to analyze how glenoid implant tilt impacts long term success/healing of total shoulder arthroplasties (TSA). Micromotion - small movements between the anchors and the surrounding bone - is known to cause issues with long term implant success if above a certain threshold. This is due to the inability of the bone to successfully integrate with the implant if the forces/motion are too high. Our goal is to understand how micromotion varies both with different shoulder positions/forces and different implant angles in order to develop a better method for determining optimal implant placement. This will vary on a patient-to-patient basis as each individual has different glenoid, scapular, and humeral anatomy, and we anticipate that the development of an FEM from a number of cadaver models will assist in future patient diagnosis. The center of the discussion is to determine how to balance "optimal" glenoid implant angle and simultaneously minimizing bone reaming.

There are some existing papers that use FE analysis to examine TSA implant success, which has provided a baseline for me to start expanding my knowledge base on. Literature from Chae et al., and Bryce et al. have established that reaming of the glenoid is positively correlated with implant failure, as the decreased trabecular bone volume can lead to instability. Friedman et al. have determined that micromotion between the baseplate and the glenoid is subcritical at retroversion angles up to 25 degrees; however, their work leaves room for further studies into micromotion at the attachment sites rather than just the baseplate interface.

This coming week I plan to continue to expand my background knowledge on this topic and to start working on model analysis as well as shadowing Dr. Fu.


Cited: 

Bryce, C. D., Davison, A. C., Okita, N., Lewis, G. S., Sharkey, N. A., & Armstrong, A. D. (2010). A biomechanical study of posterior glenoid bone loss and humeral head translation. Journal of Shoulder and Elbow Surgery, 19(7), 994–1002. https://doi.org/10.1016/J.JSE.2010.04.010

Chae, S.-W., Lee, H., Kim, S. M., Lee, J., Han, S.-H., & Kim, S.-Y. (2016). Primary stability of inferior tilt fixation of the glenoid component in reverse total shoulder arthroplasty: A finite element study; Primary stability of inferior tilt fixation of the glenoid component in reverse total shoulder arthroplasty: A finite elem. J Orthop Res, 34, 1061–1068. https://doi.org/10.1002/jor.23115

Friedman, R. J., Sun, S., She, X., Esposito, J., Eichinger, J. K., & Yao, H. (2021). Effects of increased retroversion angle on glenoid baseplate fixation in reverse total shoulder arthroplasty: a finite element analysis. Seminars in Arthroplasty JSES, 31(2), 209–216. https://doi.org/10.1053/J.SART.2020.11.014


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