通过“简单转化试验”这一临床诊断过程分析肩部下盂肱韧带的生物力学机理

Abstract

The shoulder is one of the most complex and often injured joints in the human body. Injuries to the soft tissue restraints of the shoulder are frequently difficult to diagnose and treat effectively. The inferior glenohumeral ligament (IGHL) of the glenohumeral capsule is especially prone to injury, and differential diagnosis is difficult due to the multiple soft tissue structures that complement its function in vivo. The objective of this research was to examine the function of the IGHL during a clinical diagnostic procedure termed the “simple translation test” using the finite element method. A finite element (FE) model of the humerus, scapula, humeral head cartilage and IGHL was constructed from a subject-specific CT dataset. A repeatable reference state for strain measurement was established by using compressed air to inflate the capsule to a pressure of 1 KPa. The CT dataset was acquired while the capsule was inflated, and the finite element model geometry was extracted to mimic this configuration. Starting from this reference state, experimentally measured 6-DOF kinematics were applied to the finite element model. At maximum anterior translation, first principal strains in the IGHL were highly inhomogeneous. In the AB-IGHL, strains of 0-19% were predicted over all three angles of external rotation. Strains of 0-31% were predicted in the axillary pouch of the IGHL. In the PB-IGHL, strains of 1-38% were predicted. The highest strains occurred during maximum external rotation at the insertion sites. In the sensitivity study, reduction of the IGHL modulus by one standard deviation generally increased strains in the IGHL near the scapula and decreased strains near the humerus, with changes ranging from –56.8 to 12.7 %. Regional strain results point to a transfer of load from the scapular insertion site of the IGHL to the humeral insertion site with increasing external rotation,in the form of increasing strain near the humerus and decreasing strain near the scapula. This could be due to the observation that as the material properties of the cartilage and IGHL were varied, the extent and location of contact between the IGHL and cartilage changed. Using the techniques developed within this research project, an improved understanding of the role of the IGHL in anterior stability of the joint can be gained. This will lead to better rehabilitation protocols and improved surgical procedures.