A low-cost solution for the restoration of femoral head centre during total hip arthroplasty

Restoration of joint centre during total hip arthroplasty is critical. While computer-aided navigation can improve accuracy during total hip arthroplasty, its expense makes it inaccessible to the majority of surgeons. This article evaluates the use, in the laboratory, of a calliper with a simple computer application to measure changes in femoral head centres during total hip arthroplasty. The computer application was designed using Microsoft Excel and used calliper measurements taken pre- and post-femoral head resection to predict the change in head centre in terms of offset and vertical height between the femoral head and newly inserted prosthesis. Its accuracy was assessed using a coordinate measuring machine to compare changes in preoperative and post-operative head centre when simulating stem insertion on 10 sawbone femurs. A femoral stem with a modular neck was used, which meant nine possible head centre configurations were available for each femur, giving 90 results. The results show that using this technique during a simulated total hip arthroplasty, it was possible to restore femoral head centre to within 6?mm for offset (mean 1.67?±?1.16?mm) and vertical height (mean 2.14?±?1.51?mm). It is intended that this low-cost technique be extended to inform the surgeon of a best-fit solution in terms of neck length and neck type for a specific prosthesis.

Hip protectors to prevent hip fractures - a waste of time and money?

Abstract:
Background: An estimated 30-60% of older
adults fall every year and about 1% of falls result in a hip fracture. Hip fracture is a serious and growing problem, with a 3-10 fold rise in worldwide incidence predicted by 2050 (Gullberg, et al 1997). Hip protectors are underwear with built in protection for the greater trochanter. They are designed to prevent hip fractures by dispersing or absorbing the force of a fall. Trials
published to 2001 were broadly supportive of
the effectiveness of hip protectors, and this
was reflected in a Cochrane review in 2000.
However, earlier trials were methodologically
flawed and subsequent trials have not demonstrated effectiveness. The most recent Cochrane review describes only a marginal benefit (Parker et al, 2005).
Review and Discussion: This presentation
evaluates the current evidence for the use
of hip protectors and discusses the use of
that evidence by manufacturers, suppliers,
professional groups and guideline developers.
Interestingly, despite the limitations of the
evidence base, most advice has been broadly
supportive. Reasons for this are proposed
and discussed in the context of a critique of
evidence-based healthcare. protectors. However, the available evidence can be used in different ways and for different purposes by those with an interest in promoting
the use of hip protectors. A conservative
approach is warranted, where, if we cannot
demonstrate that hip protectors work, we
presume that they do not. This presentation will be of use to practitioners wanting to evaluate the evidence base for hip protectors (and other recommended interventions) on behalf of clients. It will also be of interest to policy makers who must assess the claims made for health care technologies as part of the decisionmaking process.
Recommended reading:
Gullberg B, Johnell O, Kanis JA (1997) Worldwide
projections for hip fracture. Osteoporos
Int. 7(5):407-13 .
Parker MJ, Gillespie WJ, Gillespie LD (2005) Hip
protectors for preventing hip fractures in older
people. The Cochrane Database of Systematic
Reviews Issue 3. Art. No.: CD001255.pub3. DOI:
10.1002/14651858.CD001255.pub3.

A new look at dual-hop relaying: Performance limits with hardware impairments

Physical transceivers have hardware impairments that create distortions which degrade the performance of communication systems. The vast majority of technical contributions in the area of relaying neglect hardware impairments and, thus, assume ideal hardware. Such approximations make sense in low-rate systems, but can lead to very misleading results when analyzing future high-rate systems. This paper quantifies the impact of hardware impairments on dual-hop relaying, for both amplify-and-forward and decode-and-forward protocols. The outage probability (OP) in these practical scenarios is a function of the effective end-to-end signal-to-noise-and-distortion ratio (SNDR). This paper derives new closed-form expressions for the exact and asymptotic OPs, accounting for hardware impairments at the source, relay, and destination. A similar analysis for the ergodic capacity is also pursued, resulting in new upper bounds. We assume that both hops are subject to independent but non-identically distributed Nakagami-m fading. This paper validates that the performance loss is small at low rates, but otherwise can be very substantial. In particular, it is proved that for high signal-to-noise ratio (SNR), the end-to-end SNDR converges to a deterministic constant, coined the SNDR ceiling, which is inversely proportional to the level of impairments. This stands in contrast to the ideal hardware case in which the end-to-end SNDR grows without bound in the high-SNR regime. Finally, we provide fundamental design guidelines for selecting hardware that satisfies the requirements of a practical relaying system.

Hazardous alcohol consumption is associated with increased levels of B-type natriuretic peptide: evidence from two population-based studies

Russia has very high mortality from cardiovascular disease (CVD), with evidence that heavy drinking may play a role. To throw further light on this association we have studied the association of alcohol with predictors of CVD risk including B-type natriuretic peptide (BNP). Levels of BNP increase primarily in response to abnormal cardiac chamber wall stretch which can occur both as a result of atherosclerosis as well as due to other types of damage to the myocardium. No previous population-based studies have investigated the association with alcohol. We analysed cross-sectional data on drinking behaviour in 993 men aged 25-60 years from the Izhevsk Family Study 2 (IFS2), conducted in the Russian city of Izhevsk in 2008-2009. Relative to non-drinkers, men who drank hazardously had an odds ratio (OR) of being in the top 20 % of the BNP distribution of 4.66 (95 % CI 2.13, 10.19) adjusted for age, obesity, waist-hip ratio, and smoking. Further adjustment for class of hypertension resulted in only slight attenuation of the effect, suggesting that this effect was not secondary to the influence of alcohol on blood pressure. In contrast hazardous drinking was associated with markedly raised ApoA1 and HDL cholesterol levels, but had little impact on levels of ApoB and LDL cholesterol. Similar but less pronounced associations were found in the Belfast (UK) component of the PRIME study conducted in 1991. These findings suggest that the association of heavy drinking with increased risk of cardiovascular disease may be partly due to alcohol-induced non-atherosclerotic damage to the myocardium.