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Title: Capsular restraints of the glenohumeral joint
Author: Southgate, Dominic F. L.
ISNI:       0000 0004 2680 930X
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2009
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The glenohumeral joint is the articulation between the glenoid of the scapula and the head of the humerus; its high mobility requires a combination of active and passive stabilisers to maintain a functional joint. The aim of this thesis was to establish the mechanical properties of the glenohumeral capsule and model its contribution to stability of the joint. A six degree of freedom cadaveric testing apparatus was constructed and instrumented to facilitate laxity experiments of glenohumeral specimens in any physiological position. A pilot study examining rotational laxity of the specimens in different positions was performed to determine the optimum position for preconditioning, which was found to be 30° glenohumeral abduction with a minimum axial rotation moment of 0.5 Nm. The second stage of cadaveric testing investigated the effect of negative intra-articular pressure on joint laxity and established the envelope of translational laxity for varying levels of abduction, flexion and axial rotation. Venting the joint capsule was found to significantly increase translation in certain positions, whilst the role of the long head of biceps tendon was also studied and found to significantly reduce translations when placed under tension. Pathology of the superior glenoid labrum was simulated, repaired and tested, and a clinical test for these lesions was also replicated using the testing apparatus. However, little mechanical effect was observed in the pathology simulation experiments. The ultimate strength of the lesion repairs was also tested and found that the primary cause of failure was tendon mid-substance rupture. The data from cadaveric testing was used to evaluate a computational model of the glenohumeral ligaments and modify the parameters to improve the accuracy of the simulations. A musculoskeletal model of the upper limb, capable of predicting the muscle forces at the shoulder, was modified to accept additional inputs due to the ligament forces. The sensitivity of the ligament model and the musculoskeletal model to the ligament parameters was also analysed. Through these techniques, the ligament forces were found to increase predicted glenohumeral joint force and shoulder muscle activation at higher levels of abduction and forward flexion. The results of this work can be used to improve surgical techniques and rehabilitation for a range of different shoulder pathologies. Future study should focus on improving geometrical wrapping techniques and model assumptions not covered in this work.
Supervisor: Bull, Anthony ; Hansen, Ulrich Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral