Comparison of Suture Configurations for Acromioclavicular Joint Synthetic Reconstruction in Acromioclavicular Joint Separation: Finite Element Analysis

Abstract

BACKGROUND: In acromioclavicular (AC) joint separation, the weight of the upper extremity and scapula causes the scapula to rotate downward and internally along the thoracic cage. This results in displacement of the AC joint along three axes: anteroposterior, mediolateral, and vertical. Finite element models can aid in directing future biomechanical studies on this concept, not just the vertical axis, as has mainly been the focus in the past. This study uses finite element models to evaluate the stress across six suture configurations which reflects the efficacy on restraining AC joint motion after ligament resection with the upper extremity at rest. MATERIAL AND METHODS: Three finite element (FE) models were constructed to simulate AC joint stabilisation with six different suture configurations, which were anterior-, posterior-, O-, X-, O-plus-X-, and V-frames. Internal and downward rotations of scapula, along with upward rotation of clavicle were defined following a whole-cadaveric study where the AC and coracoclavicular (CC) ligaments were removed entirely. Stress magnitude and distribution across the strand of each suture configuration were evaluated. RESULTS: There is high stress in sutures that cross posteriorly and insert at the posterior clavicle (171,877-219,489 MPa) and anterior limbs (162,512-177,021 MPa). Suture crossing from the posterolateral to anteromedial point showed 36,573-39,430 MPa of stress. CONCLUSION: 1. There are significant loads on sutures crossing posteriorly across the AC joint and located at the posterior aspect of the distal clavicle, as well as the anterior limbs. 2. The sutures crossing from the posterolateral to anteromedial point experience minimal load. 3. Further biomechanic studies in cadavers and clinical studies are still necessary to strengthen the evidence base for these findings.