Glenoid failure in Total Shoulder Arthroplasty
Author(s)
Gregory, Thomas Maurice Stewart
Type
Thesis
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.
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.
Date Issued
2010
Date Awarded
2011-07
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Hansen, Ulrich
Emery, Roger
Amis, Andrew
Creator
Gregory, Thomas Maurice Stewart
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)