Anchor Hole Placement for Bankart Repairs and its Interaction with Variable Size Hill-Sachs Defects- Minimising Risk of Glenoid Rim Fractures

: As the use of glenoid suture anchors in arthroscopic and open reconstruction, for instability after Bankart lesions of the shoulder, increases, an emerging problem has been the incidence of glenoid rim fractures through suture drill holes. Very little is known regarding the effect of the Hill-Sachs lesion on the glenoid's susceptibility to fracture and how drill hole location can further affect this. This study used finite element modelling techniques to investigate the risk of fracture of the glenoid rim in relation to variable sized Hill-Sachs defects impacting on the anterior glenoid edge with suture anchor holes placed in varying positions. The distribution of Von Mises (VM) stresses and the Factor of Safety (FOS) for each of the configurations were calculated. The greatest peak in von Mises (VM) stresses was generated when the glenoid was loaded with a small Hill-Sachs lesion. The VM stresses were lessened and the FOS increased (reducing likelihood of failure) with increasing size of the Hill-Sachs lesion. Placement of the suture drill holes at 2mm from the glenoid rim showed the highest risk of failure; and when combined with a medium sized Hill-Sachs lesion, which matched the central line of the drill holes, a potentially clinically significant configuration was presented. The results of this study are useful in assisting the surgeon in understanding the interaction between the Hill-Sachs lesion size and the placement of suture anchors with the purpose of minimising the risk of subsequent rim fracture with new injury.