Patients exposed to a surgical safety checklist experience better postoperative outcomes, but this could simply reflect wider quality of care in hospitals where checklist use is routine.

III.

Metal artefact reduction (MAR) MRI is now widely considered to be the standard for imaging metal-on-metal (MoM) hip implants. The Medicines and Healthcare Products Regulatory Agency (MHRA) has recommended cross-sectional imaging for all patients with symptomatic MoM bearings. This paper describes the natural history of MoM disease in a 28 mm MoM total hip replacement (THR) using MAR MRI. Inclusion criteria were patients with MoM THRs who had not been revised and had at least two serial MAR MRI scans. All examinations were reported by an experienced observer and classified as A (normal), B (infection) or C1-C3 (mild, moderate, severe MoM-related abnormalities). Between 2002 and 2011 a total of 239 MRIs were performed on 80 patients (two to four scans per THR); 63 initial MRIs (61%) were normal. On subsequent MRIs, six initially normal scans (9.5%) showed progression to a disease state; 15 (15%) of 103 THRs with sequential scans demonstrated worsening disease on subsequent imaging. Most patients with a MoM THR who do not undergo early revision have normal MRI scans. Late progression (from normal to abnormal, or from mild to more severe MoM disease) is not common and takes place over several years.

The avidity of antibodies for antigens can be measured by determining what remains bound after exposing the antibody-antigen complex to a chaotropic agent such as urea. This method has been gaining popularity for assessing the immune response to the human immunodeficiency virus type 1 (HIV-1) surface glycoprotein gp120 (or its counterpart from simian immunodeficiency virus), during natural infection or after subunit vaccination. High-avidity antibodies have been considered to be a possible correlate of protection. We have examined the avidity assay to determine what it, in fact, measures. First, we studied the development of the anti-gp120 response in seroconverting individuals. Urea elution reduced the polyclonal anti-gp120 titers by 3- to 10-fold. After allowing for the consequent reduction in assay sensitivity, there was no obvious change in the rate of development of the high-avidity and unfractionated antibody responses. Furthermore, in the one individual who developed a strong autologous, virus-neutralizing response, the appearance of neutralizing antibodies and high-avidity antibodies did not coincide. Antibodies to the V3 loop, when present, comprised a major fraction of the polyclonal response that survives urea elution. We next examined the effect of urea elution on the binding to gp120 of a panel of monoclonal antibodies (MAbs). Urea treatment preferentially eluted MAbs to discontinuous rather than continuous epitopes, independent of their affinities. Furthermore, these patterns of epitope stability were unaltered by the presence of polyclonal anti-gp120 antibodies. As most broadly neutralizing anti-gp120 antibodies recognize discontinuous epitopes, this skewing effect must be taken into account when interpreting studies using polyclonal sera.

Surgical practice in the UK changed in 1993, when Suzanne Holmes and her cardiac surgical colleagues introduced the surgical care practitioner role (SCP). Within a consultant led extended surgical team, SCPs work alongside a variety of healthcare practitioners to provide safe patient care, meet service demands and educate the future surgical workforce. This article reviews the history of this development over the last fifteen years in the context of a busy orthopaedic department and discusses some unforeseen consequences.