Metal Artefact Reduction Sequence (MARS) MRI is being increasingly used to detect soft tissue inflammatory reactions surrounding metal-on-metal hip replacements. The UK MHRA safety alert announced in April 2010 recommended cross-sectional imaging such as MRI for all patients with painful MOM hips. The terms used to describe the findings include bursae, cystic lesions and solid masses. A recently used term, pseudotumour, incorporates all of these lesions. We aimed to correlate the pattern of abnormalities on MRI with clinical symptoms. Following our experience with over 160 MARS MRI scans of patients with MOM hips we recognized patterns of lesions according to their: wall thickness, T1/T2 signal, shape, and location. We categorised the 79 lesions from 159 MARS MRI scans of into our novel classification scheme of 1, 2a, 2b and 3. There were two groups of patients: well functioning and painful.Introduction
Method
In large diameter hip arthroplasty, the femoral head size and shape have to be optimised to avoid neck on socket impingement if the head is too small, or psoas tendonopathy if the head is too large, overhanging the normal head neck junction in the sagittal plane. Currently there is no published guideline to help the surgeon select an optimal size femoral head. Instead, the novice surgeon may inadvertently oversize the femoral component through fear of notching the femoral neck—causing psoas impingement, especially in female patients. We sought to provide anatomically based advice for surgeons to optimise both the position of the femoral head and the head neck ratio. 100 hips were reviewed. Fifty radiographically normal hips in elderly patients with fractures of the contralateral side and 50 hips from patients whose contralateral side was arthritic secondary, either to Cam or pincer type impingement, or DDH. The head neck ratios were calculated using two methods: the plain AP radiographs were measured on PACS (Picture Archiving and Communication System) and CT scans obtained as part of the work up to hip surgery were measured in validation. The head neck ratio was calculated by dividing the diameter of the widest point across the femoral head by the narrowest part across the femoral neck. The HNR of 39 patients who attended a painful MOM clinic were also reviewed.Background
Materials and Methods
In 2009, surgeon error is a major factor contributing to premature failure in conventional arthroplasty. Technology has revolutionised quality control in all manufacturing industries, yet it has made little or no impact on practice in arthroplasty. Currently, no agreed standards exist—in either the UK or Australia— that allows us to state whether or not the operation was performed correctly. In hip arthroplasty, acetabular orientation may be considered a non-controversial metric for assessing surgical precision in hip arthroplasty. We considered that a trained surgeon should be able to orientate the acetabular component within the safe zone 19 times out of 20. 40 trainees at different stages in their training and 20 trained surgeons, (half of whom had performed over 1000 hip replacements) were assessed for their ability to orient an acetabular cup within the safe zone on three stations, one with the pelvis in the anatomic orientation, one with the pelvis in a distorted position, and one with the pelvis clad in a body preventing reliable palpation of landmarks and in a distorted position. Their scores were compared to the standard we set, and to the scores of medical students using robotic technology to assist them.Introduction
Materials and methods
