Glenoid failure in Total Shoulder Arthroplasty

Abstract

Compared to hip and knee, anatomic shoulder arthroplasty is relatively poorly understood, underdeveloped and reported loosening rates are very high, the common cause of failure being glenoid aseptic loosening. The aim of this thesis was first to establish in-vitro and in-vivo CT protocols allowing direct monitoring of glenoid fixation and aseptic loosening and secondly to identify key elements of the procedure that could improve results of prosthetic surgery. First, in-vitro, the ASTM standard method for evaluating loosening of glenoid implants was modified, so that, with the use of CT-scans at regular interval basis, it allows the direct monitoring of the failure observed in the laboratory setting. The failure was observed at the cement-implant interface and progressed from the edges of the implants, both superior and inferior, towards the keel. Secondly, an in-vivo CT protocol was established that eliminates most of the metallic artefacts caused by the humeral head and consequently enhances the visualisation of the radiolucent lines and osteolysis around the glenoid. The link between radiological lucencies and aseptic loosening was confirmed first in a study including 68 cases using this CT protocol, which confirmed the progression of the lucencies over time, and secondly, by the use of Spect-CT. The 3-dimensional spatial (mal)position of the glenoid component and the resulting consequences were analysed in three additional studies. The effect of malposition on clinical results and radiological lucencies; the relationship to the preoperative eroded glenoid and the relationship to polyethylene wear were all investigated. These studies stressed how inaccurately the glenoid components are positioned in clinical practise and that this inaccuracy has a detrimental effect on polyethylene wear; aseptic loosening and ultimately on clinical outcome. Future work should focus on establishing the optimal position of the glenoid implant, and how to achieve this optimal placement in surgical practise.