| The glenohumeral joint is unique in that it has the greatest mobility among the human joints. Stability of the glenohumeral joint is provided by the complex interaction between the passive and active stabilizers. To date, extensive research has been performed to investigate the contribution of each stabilizer, such as bony geometry, capsuloligaments structure, or muscles, to glenohumeral joint stability. It has been demonstrated that the function of each stabilizer is highly dependent on joint position. Since the bony and soft tissue stabilizers do not function separately, it is required to quantitatively measure the contribution of each stabilizer with all stabilizers functioning simultaneously. To achieve this goal, a geometry-driven biomechanical analysis was developed and used to evaluate the contribution of the bony and soft tissue stabilizers of the glenohumeral joint. Chapter 2 describes the development of the anatomic glenohumeral joint testing system, the geometry-driven biomechanical analysis of the glenohumeral joint, and the biomechanical parameters quantified. In chapter 3, the contributions of the glenohumeral joint capsule and muscles on biomechanical characteristics were quantitatively evaluated by comparing range of motion, glenohumeral joint forces, contact characteristics, maximum capsular length, and the geometric center of the humeral head for three conditions including intact capsule with compressive loading, intact capsule with simulated muscle loading, and resected capsule with simulated muscle loading. In chapter 4, study application of the geometry-driven biomechanical analysis, the influence of the internal rotator muscles on maximal external rotation and the capsular length, was described. In conclusion, a geometry-driven biomechanical analysis based on the specimen-specific geometry has been successfully developed to quantify the biomechanical parameters of the glenohumeral joint. Further biomechanical parameters, such as subacromial impingement, potential moments generated by each muscle, internal impingement of the rotator cuff, simulation of the net muscle force vector change by increasing or decreasing specific muscle forces, simulation of muscle transfer by alternating muscle insertions, and contact simulation could be analyzed. Additionally this technique could also be applied to other joints to improve the understanding of orthopaedic biomechanics. |
