A longitudinal study of MARS MRI scanning of soft-tissue lesions around metal-on-metal total hip arthroplasties and disease progression.

We investigated the changes seen on serial metal artefact reduction magnetic resonance imaging scans (MARS-MRI) of metal-on-metal total hip arthroplasties (MoM THAs). In total 155 THAs, in 35 male and 100 female patients (mean age 70.4 years, 42 to 91), underwent at least two MRI scans at a mean interval of 14.6 months (2.6 to 57.1), at a mean of 48.2 months (3.5 to 93.3) after primary hip surgery. Scans were graded using a modification of the Oxford classification. Progression of disease was defined as an increase in grade or a minimum 10% increase in fluid lesion volume at second scan. A total of 16 hips (30%) initially classified as 'normal' developed an abnormality on the second scan. Of those with 'isolated trochanteric fluid' 9 (47%) underwent disease progression, as did 7 (58%) of 'effusions'. A total of 54 (77%) of hips initially classified as showing adverse reactions to metal debris (ARMD) progressed, with higher rates of progression in higher grades. Disease progression was associated with high blood cobalt levels or an irregular pseudocapsule lining at the initial scan. There was no association with changes in functional scores. Adverse reactions to metal debris in MoM THAs may not be as benign as previous reports have suggested. Close radiological follow-up is recommended, particularly in high-risk groups.

Out-of-hours MRI provision in the UK and models of service delivery.

AIM: To examine current out-of-hours magnetic resonance imaging (MRI) provision through a snapshot survey of National Health Service (NHS) trusts and to assay how radiographer staffing cover was provided for out-of-hours services. MATERIALS AND METHODS: A snapshot postal survey was mailed to heads of service of all 234 trusts in England and Wales. A literature search on the models of service delivery and correlation with the authors' internal MRI rota, which has provided a full on-call service for 20 years was undertaken. RESULTS: The response rate was 45.7% (107 of 234); 14% of responders provided full access to MRI 24 h a day; 63% provided extended weekday service, typically to 20.00 h; and 81% provided a weekend daytime service. The radiographers running the service were typically from the core MRI team. Approximately one-third (29.9%) of trusts provided training in basic brain and spine MRI to non-core MRI team members, but they typically did not participate in out-of-hours provision. CONCLUSION: There is currently a paucity of information on the provision of out-of-hours MRI in the NHS. However, there is increasing pressure to provide complex imaging out of hours, and in the future, trauma centres may be required to provide MRI to assess spinal injury. The authors describe a system to provide access to MRI at no additional cost to the organization based on 20 years of experience. A minority of surveyed acute NHS trusts have full out-of-hours access to MRI. Demand for MRI provision out of core hours is likely to increase.

The premature failure of the Charnley Elite-Plus stem: a confirmation of RSA predictions.

We performed a clinical and radiological study to determine the rate of failure of the Charnley Elite-Plus femoral component. Our aim was to confirm or refute the predictions of a previous roentgen stereophotogrammetric analysis study in which 20% of the Charnley Elite-Plus stems had shown rapid posterior head migration. It was predicted that this device would have a high early rate of failure.We examined 118 patients at a mean of nine years after hip replacement, including the 19 patients from the original roentgen stereophotogrammetric study. The number of revision procedures was recorded and clinical and radiological examinations were performed. The rate of survival of the femoral stems at ten years was 83% when revision alone was considered to be a failure. It decreased to 59% when a radiologically loose stem was also considered to be a failure. All the patients previously shown in the roentgen stereophotogrammetric study to have high posterior head migration went on to failure. There was a highly significant difference (p = 0.002) in posterior head migration measured at two years after operation between failed and non-failed femoral stems, but there was no significant difference in subsidence between these two groups. Our study has shown that the Charnley Elite-Plus femoral component has an unacceptably high rate of failure. It confirms that early evaluation of new components is important and that roentgen stereophotogrammetric is a good tool for this. Our findings have also shown that rapid posterior head migration is predictive of premature loosening and a better predictor than subsidence.

An oral sodium citrate-citric acid non-particulate buffer in humans.

We have investigated the effect on the pH of the gastric fluid of a single dose of sodium citrate 0.3 mol litre-1 (antacid) and a solution containing sodium citrate dehydrate (100 mg ml-1) with citric acid monohydrate (66 mg ml-1) (buffer). The dose for both solutions was 0.4 ml kg-1 via a nasogastric tube. Each group comprised 10 patients undergoing neurosurgical operations of 5-7 h duration. A control group of 10 patients received no gastric solution. The pH of the gastric aspirate was measured hourly using a Metrohm 632 digital pH meter (Synectics Medical, Sweden). Mean baseline gastric pH was 2.64 (SD 1.71). In the control group, pH increased to 4.4 (1.51) at 5 h, returning to baseline at 7 h. In the antacid group, pH increased to 6.11 (0.47) at 15 min and decreased to 3.70 (1.94) at 7 h (P < 0.01). In the buffer group, pH was stable at 3.80-3.95 (0.22) over 7 h (P > 0.01). Total mean gastric aspirate was 0.5 ml kg-1.