Mid-range shoulder instability modeled as a cam-follower mechanism. Issue 10 (16th July 2015)

• Record Type: Journal Article
• Authors: Willemot, Laurent; Thoreson, Andrew; Ryan Breighner, ; Hooke, Alexander; Verborgt, Olivier; An, Kai-Nan
• Is Part Of: Journal of biomechanics. Volume 48:Issue 10(2015)
• Page Start: 2227
• Page End: 2231
• Publication Date: 2015-07-16
• Subjects: Glenohumeral instability -- Kinematics -- Modeling; Animal mechanics -- Periodicals; Biomechanics -- Periodicals; Biomechanics -- Periodicals; Mécanique animale -- Périodiques; Biomécanique -- Périodiques; Electronic journals; 571.4305
• DOI: 10.1016/j.jbiomech.2015.02.053
• Languages: English
• ISSNs: 0021-9290

Abstract

Abstract: In this paper, we model a simplified glenohumeral joint as a cam-follower mechanism during experimental simulated dislocation. Thus, humeral head trajectory and translational forces are predicted using only contact surface geometry and compressive forces as function inputs. We demonstrate this new interpretation of glenohumeral stability and verify the accuracy of the method by physically testing a custom-molded, idealized shoulder model and comparing data to the output of the 2D mathematical model. Comparison of translational forces between experimental and mathematical approaches resulted in r 2 of 0.88 and 0.90 for the small and large humeral head sizes, respectively. Comparison of the lateral displacement resulted in r 2 of 0.99 and 0.98 for the small and larger humeral head sizes, respectively. Comparing translational forces between experiments and the mathematical model when varying the compressive force to 30 N, 60 N, and 90 N resulted in r 2 of 0.90, 0.82, and 0.89, respectively. The preliminary success of this study is motivation to introduce the effects of soft tissue such as cartilage and validation with a cadaver model. The use of simple mathematical models such as this aid in the set-up and understanding of experiments in stability research and avoid unnecessary depletion of cadaveric resources.