The direction of penetration of the femoral head following total hip replacement has been shown at revision to be superomedial, superior or superolateral. However, it is important to study well functioning components to describe normal patterns of wear. The aim of this study was to characterise the 3D direction of penetration in standard and HXLPE.

A prospective double blind randomised control trial was conducted using Radiostereometric Analysis (RSA). Fifty-four subjects were randomised to receive hip replacements with either UHMWPE liners or HXLPE liners. All subjects received a cemented CPT stem and uncemented Trilogy acetabular component (Zimmer, Warsaw, IN, USA). The 3D penetration of the head into the socket was determined to a minimum of 7 years.

The direction of penetration between one and seven years was in a superior and lateral direction for both groups. In the HXLPE group there was no significant penetration in the coronal or sagittal planes (superiorly 0.009 mm/yr, 95% confidence interval, ±0.045, p1 = 0.68, laterally 0.003mm/yr, CI 0.031, p1 = 0.85). In the UHMWPE group there was significant penetration 0.059 mm/yr superiorly (CI 0.042, p1 = 0.01) and 0.049 mm/yr laterally (CI 0.044, p1 = 0.03). The anterior-posterior steady state penetration was not significant in either group (HXLPE p1 = 0.39, UHMWPE p1 = 0.37).

We have previously demonstrated that the penetration in the first year is creep-dominated and is in the proximal direction. From one year onwards the superolateral direction of penetration is probably due to wear. The steady-state wear direction is the same in both bearings types. It is likely that creep occurs in the direction of the Joint Reaction Force i.e. superomedial, whereas wear is perpendicular to the axis of rotation and therefore superolateral. This work may enable us to develop more accurate models for predicting wear in total hip arthroplasty.

Background

Despite aggressive debridement, thorough irrigation, administration of systemic antibiotics and staged treatment, many open fractures still become infected. A graft that can promote bone regeneration and prevent infection could decrease complications. Polyurethane (PUR) scaffolds have been previously shown in separate studies to be non-toxic, osteoconductive, can promote bone growth through BMP delivery and prevent infection by having sustained release of an antibiotic. This scaffold can deliver both BMP and vancomycin simultaneously; the purpose of this study is to determine if the co-delivery of the antibiotic inhibits bone formation.

Introduction

Bearing surfaces used for total hip arthroplasty must have characteristics including bio-compatibility, low friction and low wear rate. Bearing combinations are generally characterised as Soft on Hard/Hard. In general, all newer bearing combinations have reduced wear but may present with other issues that impact on patient outcomes.

Pseudotumours (soft-tissue masses relating to the hip joint) following metal-on-metal hip resurfacing arthroplasty (MoMHRA) have been associated with elevated serum and hip aspirate metal ion levels, suggesting that pseudotumours occur when there is increased wear. This study aimed to quantify the wear of implants revised for pseudotumours and a control group of implants revised for other reasons of failure.

A total of 30 contemporary MoMHRA implants in two groups were investigated: (1) 8 MoMHRA implants revised due to pseudotumour; (2) 22 MoMHRA implants revised due to other reasons of failure. The linear wear of retrieved implants was measured using a Taylor-Hobson Roundness machine. The average linear wear rate was defined as the maximum linear wear depth divided by the duration of the implant in vivo.

In comparison with the non-pseudotumour implant group, the pseudotumour implant group was associated with: (1) significantly higher median linear wear rate of the femoral component: 8.1 um/year (range 2.75-25.4 um/year) vs. 1.97 um/year (range 0.82-13.00 um/year), p=0.002; and (2) significantly higher median linear wear rate of the acetabular component: 7.36 um/year (range 1.61-24.9 um/year) vs. 1.28 um/year (range 0.18-3.33 um/year), p=0.001. Wear on the acetabular cup components in the pseudotumour group always involved the edge, indicating edge-loading of the bearing.

Significantly greater linear wear rates of the MoMHRA implants revised due to pseudotumour support the in vivo elevated metal ion concentrations in patients with pseudotumours. This study is the first to confirm that pseudotumour occurs when there is increased wear at the MoM articulation. Furthermore, edge-loading may be the dominant wear generation mechanism in patients with pseudotumour.

Background

Every trainee in Trauma and Orthopaedics (T&O) in the UK and Ireland records their operative experience via the Faculty of Health Informatics eLogbook. Since August 2009, all doctors were subject to the full European Working Time Directive (EWTD) restrictions of 48 hours of work per week. We have previously shown that the implementation of shift working patterns in some units in preparation for these restrictions reduced training opportunities by 50% (elective surgical exposure). We have now analysed the national data to establish whether operative experience has fallen since August 2009.

Background

Unicompartmental knee replacement (UKR) is an established treatment for single compartment end-stage knee arthrosis with good recorded survivorship. Although often used in more active younger patients, patient selection remains controversial. To identify risk factors for early failure we compared patients with UKR failure requiring revision to total knee replacement (TKR) with a control group.

Introduction

The resurgence of TB worldwide has several underlying causes, but HIV infection has undoubtedly been a key factor in the current TB epidemic. Since TB is endemic in the developing world the influence of HIV is of concern, particularly with the emergence of multi-drug-resistant strains. The remarkable susceptibility of patients with AIDS to develop TB has shown the critical role of CD4 lymphocytes in protective immunity. In the absence of immunological surveillance by CD4 cells, 5-10% of persons with latent foci of TB reactivate each year.