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Title: Failure of the femoral component of metal-on-metal hip resurfacing arthroplasty
Author: Baker, Richard Paul
Awarding Body: University of Bristol
Current Institution: University of Bristol
Date of Award: 2015
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Historically, hip resurfacing failed from polyethylene wear and osteolysis. Modern hip resurfacing has seen a recent resurgence in its use with a different metal on metal bearing but higher failure rates than conventional total hip arthroplasty. This MD thesis explores the causes of femoral failure over nine experiments. Vascular foramina of the femoral neck are unlikely to be damaged by preparation of the femoral head for resurfacing. Increased porosity of the cancellous bone of the prepared femoral head is noted when radiographic cysts are present and in larger femoral heads. Cement penetration in the femoral head was independent of its surface porosity. The swirl cementing technique is superior to traditional bolus techniques, but neither is perfect. Temperatures reached during mechanical preparation of the femoral head are sufficient to cause osteonecrosis in one third of cases. Temperatures can be reduced with ice cold saline to safe threshold levels. The pedestal sign is a progressive phenomenon, associated with decreasing function and failure. Pedestal sign classification systems have moderate inter and intra-observer agreement, modification has improved its accuracy. Femoral necks thin over the first five years and then stabilise. Failure from fracture was associated with surgical error - notching and varus stem position and patient related factors (increased BMI). Late failure was associated with obesity. The outcome from revision of resurfacing is similar to revision of a conventional THA. Better patient selection, careful femoral head preparation, reduction of thermal injury and improved cementing technique should improve the outcome of hip resurfacing. Pedestal sign formation predicts failure and its progression is associated with decreased functional outcome.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available