Introduction

Historical studies have reported incidences of taper corrosion in retrieved MoP hips of 20–50%. These studies relied on visual assessments, rather than using modern analytical techniques.

National guidelines suggest which investigations should be performed for patients admitted with an acute hip fracture. We have observed practice often deviates from these guidelines. Our study aims to identify the incidence of deviation with regards to blood investigations and review the effect of deviation on management, and the financial burden on the healthcare system.

A total of 250 acute hip fracture admissions over 12-months period reviewed retrospectively. Admission blood tests, time of presentation, and time of operation were recorded. The cost of admission blood investigations was calculated.

Seventy-nine percent of admissions had one or more non-routine blood investigation tested. Twenty-Nine percent of these tests had abnormal results and these were found to be clinically relevant in 6% of patients. The most commonly requested non-routine investigations were: LFT in 79%, Coagulation screen in 56%, and CRP in 48%. Fifteen percent of patients did not have surgery within the time frame of 36 hours. The total cost of non-routine investigations was £1995.04.

Deviation from admission investigations guidelines for hip fractures without clinical indication adds little clinical value, has no effect on management, and can be a potential cause of unnecessary investigations. This in turn leads to further delays and extra costs.

Aim

The purpose of this study was to investigate the effects of plaster/splint immobilisation of the knee/ankle on driving performance in healthy individuals.

Introduction

Internal fixation of pertrochanteric fractures is evolving as newer implants are being developed. Proximal Femoral Nail Antirotation (PFNA) is a recently introduced implant from AO/ASIF designed to compact the cancellous bone and may be particularly useful in unstable and osteoporotic hip fractures. This study is a single and independent centre experience of this implant used in management of acute hip fractures.

Introduction

Adverse reaction to metal debris (ARMD) is an increasingly recognised complication of metal-on-metal hip arthroplasty. A previous study described poor results following revision and recommended early intervention¹. We determined the outcome of revision for ARMD and present the largest case series to date.

Patients most at risk of osteoporosis are post-menopausal women. However, for many such women, presentation of osteoporosis is only made following their first fragility fracture. Often in the UK, osteoporosis investigation occurs following discharge, and any subsequent secondary prevention starts in the community. This may result in patients with osteoporosis not being investigated or not receiving correct prophylactic treatment.

143 post-menopausal women (av. age 77.7 years) starting secondary osteoporosis prophylaxis following fragility fractures requiring operative intervention were included in this retrospective study. Osteoporosis was defined by DEXA scan using the WHO criteria (122 hip fractures and 21 wrist fractures), following the UK's national guidelines for osteoporosis prophylaxis. Treatment was started following discussion and explanation of treatment with each patient, and either commenced by the surgical team during the acute hospital admission with the fracture, or in an out-patient setting within 6 weeks of the fracture by an orthopaedic specialist nurse. To check compliance, either the patient themselves or the patients' family physician was contacted.

Results showed that 120 of the women (83.9%, 102 hip fractures, and 18 wrist fractures) were still compliant with secondary osteoporosis prophylaxis at an average follow-up of 200 days (5 hip fractures lost to follow-up, 0 wrist fractures). 12 women with hip fractures died (0 wrist fractures), and 6 women stopped taking their prophylaxis (3 hip fractures, 3 wrist fractures): 4 for medical reasons, and 2 for unknown reasons. No women sustained further fractures.

Few studies have previously investigated compliance of osteoporosis secondary prevention, and our results compare favorably. We therefore recommend the prompt commencement of secondary prevention treatment by the orthopaedic surgical team following osteoporotic fractures.

Background: There is a paucity of published data with regard to the wear of failed metal on metal (MoM) resurfacing devices.

Materials and Methods: MoM components retrieved from patients from two independent centres experiencing failure secondary to ARMD were analysed using a Mitutoyo Legex 322 coordinate measuring machine (CMM) which has an accuracy of 0.8 microns. Between 4000 – 6000 points were taken on each explant, dependent on the size of the bearing surface. Maximum wear depths and total volumetric wear were calculated. These values were compared to those from control samples retrieved following uncomplicated fractures/femoral collapse secondary to avascular necrosis (after calculating equivalent yearly wear rates).

Results: 58 ARMD components were analysed. This included 22 36mm MoM THRs (DePuy Pinnacle), 28 DePuy ASRs and 8 Zimmer Duroms. There were 30 resurfacing fracture/avascular necrosis controls. Volumetric wear rates and maximum wear depths of ARMD resurfacing components were significantly greater than the resurfacing control group for both the ASR and Duroms (p< 0.05) however 2 ARMD components exhibited similar amounts of wear compared to controls. Wear rates of the ARMD THR group were significantly lower than the ARMD resurfacing group (p< 0.05).

Conclusions: Increased articular wear is associated with an increased incidence of local adverse effects including tissue necrosis, joint effusions and fractures. However, there are a minority of patients who can develop tissue necrosis in the absence of accelerated wear, implying a spectrum of sensitivity This is reflected in the incidence of ARMD in the patient groups at the main study centre: > 5% in the ASR group and approx 1% in the THR group. We believe this indicates a failure of adequate lubrication and the resultant negative effects in larger bearing devices.

Dual Energy X-ray absorption (DEXA) has been used to measure bone mineral density (BMD) around total hip prostheses. With the recent increase in the use of metal on metal hip resurfacing, such as the Birmingham Hip Resurfacing (BHR), there has been renewed concern over per prosthetic femoral neck fracture and implant loosening. DEXA quantitatively measures bone mineral density and therefore could predict impending loosening and fracture. To the best of our knowledge, there are no recorded studies assessing BMD around metal-on-metal hip resurfacings such as the BHR. Our intention was to produce a reliable method of measuring bone density around a metal-on-metal hip resurfacing, such as the BHR, prior to a prospective study.

We performed DEXA scans on five patients (7 BHR’s), who had undergone resurfacing with the BHR within the last two years, using the Hologic QDR 45000A scanner. Each BHR was scanned twice on the same day with complete patient repositioning between scans. We analysed the data with the Hologic prosthetic hip (v 8.26a: 3) scan analysis software (operating software 9.80D) by identifying a variable number of same-sized regions of interest (ROI) within the femoral neck. These ROI’s were derived from an inter-trochanteric line and the axis of the BHR stem in the femoral neck. Each of the 14 scans was analysed twice, by three of the authors independently; with at least one week between repeat analysis by the same observer. Statistical analysis was carried out by the local University Department of Statistics.

The variation within the same ROI in a given BHR was 0.00353, whereas the variation between all ROI’s was 1.155. The intraclass-correlation was 0.997 (i.e. the correlation between any two assessments of one ROI) with an overall coefficient of variation of 5%. The variation between the two scans for each BHR and between the three assessors was not significant (p=0.87 and p=0.42 respectively). The mean BMD of the individual ROI’s, between the two assessments of the same scans by the same assessor (i.e. intra-observer variation) was lower on the second assessment by 0.0214gcm⁻² (SD=0.0025) representing 0.5% mean density for all ROI’s. This difference was statistically significant (p< 0.001).

This method demonstrates excellent reproducibility of the method. Inter-scan and inter-observer variation was so negligible that a tiny intra-observer variation of 0.5% (of mean bone density) became statistically significant (p< 0.001), despite it making no difference to the overall intraclass-correlation. Statistical advice suggested that this very small difference in mean density (intra-observer) only reached significance due to the highly sensitive measurements and excellent reproducibility.

We have designed and demonstrated a safe, non-invasive and highly reproducible method for scanning BHR implants in vivo using DEXA. We will now use this method to prospectively study our BHR population to detect impending loosening or fracture.