Kevin Famer, MD
Read complete study: Reverse total shoulder glenoid baseplate stability with superior glenoid bone loss
In the article “Reverse total shoulder glenoid baseplate stability with superior glenoid bone loss” by Martin et al, the authors looked to quantify glenoid baseplate stability with worsening superior glenoid bone loss. The authors utilized a polyurethane bone model, and created superior glenoid bone loss defects such that the attached baseplates had 100% support, 90% support, 75% support, and 50% support. The authors found the 50% support group had significantly greater micromotion than the other defects and the native state. The majority of micromotion occurred at the beginning of testing, indicating that some settling may occur with time. Interestingly, micromotion in the 50% support group exceeded 150 µm, which has been shown in animal models to be the maximum amount of micromotion that allows bony ingrowth.
The authors spend a lot of time describing their testing methods, compared to other published manuscripts. The authors applied cyclic loading at a fixed 60º glenohumeral angle, which mimics the superiorly directed force during the initiation of abduction, as opposed to other studies that apply force to the baseplate that mimics the force during the range of abduction. The benefits of the study design of this current study is that it allows real time assessment of micromotion during the course of the analysis, as well as pre and post testing, potentially allowing a better assessment of micromotion early in the loading process.
The information presented in this study is valuable in the sense that using real time of assessment of micromotion, the authors find that increasing superior glenoid wear leads to increasing superior micromotion early in the loading process. There also appears to be some settling over time, but the issue failure of early bony integration, and its association to loosening over time, is a concern. Surgeons should be aware of results of this study, and the potential risk of glenoid loosening with uncorrected superior glenoid wear.
When approaching superior glenoid wear, surgeons have three main options.