2023 ISAKOS Biennial Congress Paper
Glenoid Concavity Affects Anterior Shoulder Stability In A Biomechanical Model Including Soft Tissue and The Rotator Cuff’s Compressing Forces
Sebastian Oenning, MD, Münster GERMANY
Jens Wermers, Prof., Steinfurt GERMANY
Philipp Michel, MD, Muenster GERMANY
Michael J. Raschke, MD, Prof., Münster GERMANY
Sebastian Oenning, MD, Münster GERMANY
Alina Köhler, MD, Münster GERMANY
Mats Jonas Wiethölter, MD, Münster GERMANY
J. Christoph Katthagen, MD, Münster, NRW GERMANY
University Hospital Muenster, Department of Trauma, Hand and Reconstructive Surgery, Muenster, NRW, GERMANY
FDA Status Not Applicable
Summary
In our biomechanical shoulder model, including soft tissue and muscle forces, the glenoid concavity correlated with shoulder stability and with that should be considered in the individualized therapy of glenoid defects.
Abstract
The therapy of anterior shoulder instability in the presence of bony glenoid defects usually depends on the defect size, which is considered the main indicator of instability. Recent studies, based on computed tomography and simplified bony biomechanical models, revealed the glenoid concavity to be relevant for shoulder stability as well. However, the concavity’s effect in the presence of soft tissue and muscular forces, which are included in this study, is still unknown. We hypothesized, that the glenoid concavity would have a major impact on stability in a shoulder model including soft tissue surroundings and glenohumeral compression forces, exerted by the rotator cuff.
In n=8 human shoulder specimens, glenoid depth and concavity was measured and individual coordinate systems were calculated based on anatomical landmarks. Static load was applied to the rotator cuff’s tendons, the deltoid muscle and the biceps’ long head tendon. In a robotic test setup, an anteriorly directed force was applied to the humeral head until its translation of 5 mm. This was performed in native joints, as well as in joints with Bankart lesions and glenoid bone defects of 10% and 20%. Depending on their concavity, the specimens were divided into two subgroups (low vs. high concavity with n=4, respectively).
A high correlation between native glenoid concavity and stability could be shown (R²=0.79). For each level of defect, we found a significantly higher stability in joints with high concavity compared to the low concavity subgroup (p=0.027). In bony defects of 20% the loss of stability correlated with the initial concavity (R²=0.89), as we could see a higher loss of stability in initially high concavity joints compared to lower concavity (p=0.004).
In a test setup including soft tissue and muscle forces, the glenoid concavity correlates with shoulder stability. In bony defects, loss of concavity has a severe impact on instability. Thus, glenoid concavity should be considered in a differentiated, individualized therapy of bony glenoid defects.