Radiology of orthopaedic implants
Cobalt levels painful vs well functioning MOM hips (Larger version)
Principal Investigator: Alister Hart
The annual worldwide use of hip replacements is already more than 1 million procedures and is forecast to increase by up to 170% between 2005 and 2030. The commonest reason for redo surgery (currently 10% of all hip replacement operations are redo or revision procedures) is implant loosening caused by the poor biocompatibility between particles worn from the hip which cause an inflammatory reaction resulting in either destruction of bone or pain.
Our research involves the assessment of clinically useful advances in imaging (MRI and CT) to diagnose and quantify biocompatibility of hip and knee replacements.
Using Metal Artefact Reduction Sequence (MARS) MRI we have shown that 62% (16/26) patients with painful MOM hips had soft tissue masses (Hart AJ, Sabah S, Henckel J, Lewis A, Cobb J, Sampson B, Mitchell A, Skinner JA. The painful metal-on-metal hip resurfacing. J Bone Joint Surg Br 2009;91-B-6:738-44.)
Examples of these are shown below
MARS MRI intrapelvic mass
Hip bursa fluid level
CT vs plain radiograph measurement
In trying to understand whether component position is involved with the mechanism of the formation of inflammatory masses on MARS MRI we have also carried out metal artefact reduction CT with 3D component position measurement. This is a challenging field because the measurement of cup angles of large diameter MOM hips on xray is difficult because the femoral head obscures the cup face.
CT more accurate than xray (larger version)
Bland Altman Plot Xr vs CT
A Bland-Altman plot of the difference between 2 methods of measurement (plain radiographic and 3D CT) for the version angle of the cup of MOM hips. (In press).
Bland Altman Plot Xr vs CT (larger version)
