Morbid obesity in total hip arthroplasty: Redefining outcomes for operative time, length of stay, and readmission

Background The incidence of obesity amongst patients presenting for elective Total Hip Arthroplasty (THA) has increased in the last decade and the relationship between obesity and the need for joint replacement has been demonstrated. This study evaluates the effects of morbid obesity on outcomes following primary THA by comparing short-term outcomes in THA between a morbidly obese (BMI ≥40) and a normal weight (BMI 18.5 - <25) cohort at our institution between January 2003 and December 2010. Methods Thirty-nine patients included in the morbidly obese group were compared with 186 in the normal weight group. Operative time, length of stay, complications, readmission and length of readmission were compared. Results Operative time was increased in the morbidly obese group at 122 minutes compared with 100 minutes (p=0.002). Post-operatively there was an increased 30-day readmission rate related to surgery of 12.8% associated with BMI ≥40 compared with 2.7% (p= 0.005) as well as a 5.1 fold increase in surgery related readmitted bed days - 0.32 bed days per patient for normal weight compared with 1.64 per patient for the morbidly obese (p=0.026). Conclusion Morbidly obese patients present a technical challenge and likely this and the resultant complications are underestimated. More work needs to be performed in order to enable suitable allocation of resources.

Using coloured petri nets to simulate DoS-resistant protocols

In this work, we examine unbalanced computation between an initiator and a responder that leads to resource exhaustion attacks in key exchange protocols. We construct models for two cryp-tographic protocols; one is the well-known Internet protocol named Secure Socket Layer (SSL) protocol, and the other one is the Host Identity Protocol (HIP) which has built-in DoS-resistant mechanisms. To examine such protocols, we develop a formal framework based on Timed Coloured Petri Nets (Timed CPNs) and use a simulation approach provided in CPN Tools to achieve a formal analysis. By adopting the key idea of Meadows' cost-based framework and re¯ning the de¯nition of operational costs during the protocol execution, our simulation provides an accurate cost estimate of protocol execution compar- ing among principals, as well as the percentage of successful connections from legitimate users, under four di®erent strategies of DoS attack.

Protocol engineering for protection against denial-of-service attacks

Denial-of-service attacks (DoS) and distributed denial-of-service attacks (DDoS) attempt to temporarily disrupt users or computer resources to cause service un- availability to legitimate users in the internetworking system. The most common type of DoS attack occurs when adversaries °ood a large amount of bogus data to interfere or disrupt the service on the server. The attack can be either a single-source attack, which originates at only one host, or a multi-source attack, in which multiple hosts coordinate to °ood a large number of packets to the server. Cryptographic mechanisms in authentication schemes are an example ap- proach to help the server to validate malicious tra±c. Since authentication in key establishment protocols requires the veri¯er to spend some resources before successfully detecting the bogus messages, adversaries might be able to exploit this °aw to mount an attack to overwhelm the server resources. The attacker is able to perform this kind of attack because many key establishment protocols incorporate strong authentication at the beginning phase before they can iden- tify the attacks. This is an example of DoS threats in most key establishment protocols because they have been implemented to support con¯dentiality and data integrity, but do not carefully consider other security objectives, such as availability. The main objective of this research is to design denial-of-service resistant mechanisms in key establishment protocols. In particular, we focus on the design of cryptographic protocols related to key establishment protocols that implement client puzzles to protect the server against resource exhaustion attacks. Another objective is to extend formal analysis techniques to include DoS- resistance. Basically, the formal analysis approach is used not only to analyse and verify the security of a cryptographic scheme carefully but also to help in the design stage of new protocols with a high level of security guarantee. In this research, we focus on an analysis technique of Meadows' cost-based framework, and we implement DoS-resistant model using Coloured Petri Nets. Meadows' cost-based framework is directly proposed to assess denial-of-service vulnerabil- ities in the cryptographic protocols using mathematical proof, while Coloured Petri Nets is used to model and verify the communication protocols using inter- active simulations. In addition, Coloured Petri Nets are able to help the protocol designer to clarify and reduce some inconsistency of the protocol speci¯cation. Therefore, the second objective of this research is to explore vulnerabilities in existing DoS-resistant protocols, as well as extend a formal analysis approach to our new framework for improving DoS-resistance and evaluating the performance of the new proposed mechanism. In summary, the speci¯c outcomes of this research include following results; 1. A taxonomy of denial-of-service resistant strategies and techniques used in key establishment protocols; 2. A critical analysis of existing DoS-resistant key exchange and key estab- lishment protocols; 3. An implementation of Meadows's cost-based framework using Coloured Petri Nets for modelling and evaluating DoS-resistant protocols; and 4. A development of new e±cient and practical DoS-resistant mechanisms to improve the resistance to denial-of-service attacks in key establishment protocols.

Youth Festival Music Performance : Deception Bay

Research Background - Young people with negative experiences of mainstream education often display low levels of traditional academic achievement. These young people tend to display considerable cultural and social resources developed through their repeated experiences of adversity. Education research has a duty to provide these young people with opportunities to showcase, assess and translate their social and cultural resources into symbolic forms of capital. This creative work addresses the following research question. How can educators develop disengaged teenager's social and cultural capital through live music performances? Research Contribution - These live music performances afford the young participants opportunities to display their artistic, technical, social and cultural resources through a popular cultural format. In doing so they require education institutions to provide venues that demonstrate the skills these young people acquire through flexible learning environments. The new knowledge derived from this research focuses on the academic and self confidence benefits for disengaged young people using festival performances as authentic learning activities. Research Significance - This research is significant because it aims to maximise the number of tangible outcomes related to a school-based arts project. The young participants gained technical, artistic, social and commercial skills during this project. This performance led to more recording and opportunities to perform at other youth festivals in SE QLD. Individual performances were distributed and downloaded via creative commons licences at the Australian Creative Resource Archive. It also contributed to their certified qualifications and acted as pilot research data for two competitively funded ARC grants (DP0209421 & LP0883643)

Orthopaedics and Trauma Queensland Annual Report 2008

Orthopaedics and Trauma Queensland is an internationally recognised research group that is developing into an international leader in research and education. It provides a stimulus for research, education and clinical application within the international orthopaedic and trauma communities. Orthopaedics and Trauma Queensland develops and promotes the innovative use of engineering and technology, in collaboration with surgeons, to provide new techniques, materials, procedures and medical devices. Its integration with clinical practice and strong links with hospitals ensure that the research will be translated into practical outcomes for patients. The group undertakes clinical practice in orthopaedics and trauma and applies core engineering, modelling and clinical skills to challenges in medicine. The research is built on a strong foundation of knowledge in biomedical engineering and incorporates expertise in cell biology, mathematical modelling, human anatomy and physiology and clinical medicine in orthopaedics and trauma. New knowledge is being developed and applied to the full range of orthopaedic diseases and injuries, such as knee and hip replacements, fractures and spinal deformities.

Youth Festival Music Performance : Kingston

Research Background - Young people with negative experiences of mainstream education often display low levels of traditional academic achievement. These young people tend to display considerable cultural and social resources developed through their repeated experiences of adversity. Education research has a duty to provide these young people with opportunities to showcase, assess and translate their social and cultural resources into symbolic forms of capital. This creative work addresses the research question, how can educators maximise the social and cultural capital they help young people acquire through live music performances and studio recordings? Research Contribution - This live music performance, built on existing artistic reputations of the artists, saw the lads support one of their local heroes from Brisbane Hip Hop music scene. In doing so they showcased what their three years of concerted musical engagement can achieve within supportive flexible learning environments. The new knowledge derived from this research focuses on the academic and self confidence benefits for disengaged young people using festival performances as authentic learning activities. Research Significance - This research is significant because it aims to maximise the number of tangible outcomes related to a school-based arts project. The young participants gained technical, artistic, social and commercial status during this project. Individual performances were distributed and downloaded via creative commons licences at the Australian Creative Resource Archive. This performance also contributed to their certified qualifications and acted as pilot research data for two competitively funded ARC grants (DP0209421 & LP0883643)

Taranaki wharf in Wellington

Wellington is the capital of New Zealand, located on the southern tip of the North Island, and is a windy city, the southern-most capital city in the world and the only in the Roaring Forties. In climate it is closer to its neighbour, the South Island than to the mild major city of the north, Auckland. Yet despite, or perhaps because of this, Wellington is the undisputed cultural capital of New Zealand, with much contem porary art, design music and media coming from this town that has an absurd amount of hip bars and cafes for a population this size: 164,000 approximately. The conjunction in Lord of the Rings of incredible nature and amazing production seems to characterise the rich culture/nature hybrid that Wellington distils, the microcosm of the things that make New Zealand such an incredible place.

On analysing and interpreting variability in motor output

A recent article in the Journal of Science and Medicine in Sport by Chapman et al.1 reported data from an empirical investigation comparing lower extremity joint motions, joint coordination and muscle recruitment in expert and novice cyclists. 3D kinematic and intramuscular electromyographic (EMG) analyses revealed no differences between expert and novice cyclists for normalised joint angles and velocities of the pelvis, hip, knee and ankle. However, significant differences in the strength of sagittal plane kinematics for hip–ankle and knee–ankle joint couplings were reported, with expert cyclists displaying tighter coupling relationships than novice cyclists. Furthermore, significant differences between expert and novice cyclists for all muscle recruitment parameters, except timing of peak EMG amplitude, were also reported.

AITPM Email Newsletter Volume 0911, November 2009 : President's Message

President’s Report Hello fellow AITPM members, It is interesting to follow the news at present, where transport costs are getting a significant airing. Treasury Secretary Dr Ken Henry has enunciated something Australians may have considered extremely radical just a few years back, but in the present time appears to quite a few to be a realistic alternative. That being a rethink of the way we are charged for using our vehicles. It appears that serious consideration is being given to congestion charging, perhaps in place at least to some extent, of fuel excise. As a transport professional I am pleased that the debate has elevated to the national level, and would look forward that AITPM might contribute appropriately to it. As a motorist though, I naturally have my concerns about being hit in the hip pocket. Not that I actually drive during congested periods very much. I am fortunate to live five minutes either side of two well serviced bus corridors, one of which will eventually become a busway, and work in the central business district, which is hub from all spokes in Brisbane. As such, bus and foot are my preferred commute modes. Ah but I should not gloat, as my smart card fare is about to increase by 20 percent in the New Year! And if the newspapers are to be believed, further substantial increments are proposed over the coming few years. This is reported to recoup some more of the costs of actually providing the quality public transport system that we enjoy in our region. So I expect it will be very interesting to see how transport economics will play out in reality in the coming few years, and how governments cater to Australians who either cannot afford substantial increases in transport costs or have no viable alternatives to those facilities whose costs will increase. The 2010 AITPM National Conference, “What’s New?”, still has the opportunity for authors to submit an abstract for consideration so please consider how you might contribute to the event. Best regards to all, Jon Bunker

Effect of inaccuracies in anthropometric data and linked-segment inverse dynamic modeling on kinetics of gait in persons with partial foot amputation

The accuracy of data derived from linked-segment models depends on how well the system has been represented. Previous investigations describing the gait of persons with partial foot amputation did not account for the unique anthropometry of the residuum or the inclusion of a prosthesis and footwear in the model and, as such, are likely to have underestimated the magnitude of the peak joint moments and powers. This investigation determined the effect of inaccuracies in the anthropometric input data on the kinetics of gait. Toward this end, a geometric model was developed and validated to estimate body segment parameters of various intact and partial feet. These data were then incorporated into customized linked-segment models, and the kinetic data were compared with that obtained from conventional models. Results indicate that accurate modeling increased the magnitude of the peak hip and knee joint moments and powers during terminal swing. Conventional inverse dynamic models are sufficiently accurate for research questions relating to stance phase. More accurate models that account for the anthropometry of the residuum, prosthesis, and footwear better reflect the work of the hip extensors and knee flexors to decelerate the limb during terminal swing phase.

Corneal confocal microscopy : a novel noninvasive means to diagnose neuropathy in patients with Fabry disease

ABSTRACT: Neuropathy is a cause of significant disability in patients with Fabry disease, yet its diagnosis is difficult. In this study we compared the novel noninvasive techniques of corneal confocal microscopy (CCM) to quantify small-fiber pathology, and non-contact corneal esthesiometry (NCCA) to quantify loss of corneal sensation, with established tests of neuropathy in patients with Fabry disease. Ten heterozygous females with Fabry disease not on enzyme replacement therapy (ERT), 6 heterozygous females, 6 hemizygous males on ERT, and 14 age-matched, healthy volunteers underwent detailed quantification of neuropathic symptoms, neurological deficits, neurophysiology, quantitative sensory testing (QST), NCCA, and CCM. All patients with Fabry disease had significant neuropathic symptoms and an elevated Mainz score. Peroneal nerve amplitude was reduced in all patients and vibration perception threshold was elevated in both male and female patients on ERT. Cold sensation (CS) threshold was significantly reduced in both male and female patients on ERT (P < 0.02), but warm sensation (WS)and heat-induced pain (HIP) were only significantly increased in males onERT (P<0.01). However, corneal sensation assessed withNCCAwas significantly reduced in female (P < 0.02) and male (P < 0.04) patients on ERT compared with control subjects. According to CCM, corneal nerve fiber and branch density was significantly reduced in female (P < 0.03) and male (P < 0.02) patients on ERT compared with control subjects. Furthermore, the severity of neuropathic symptoms and the neurological component of the Mainz Severity Score Index correlated significantly with QSTand CCM. This study shows that CCM and NCCA provide a novel means to detect early nerve fiber damage and dysfunction, respectively, in patients with Fabry disease.

Biotribological assessment for artificial synovial joints : the role of boundary lubrication

Biotribology, the study of lubrication, wear and friction within the body, has become a topic of high importance in recent times as we continue to encounter debilitating diseases and trauma that destroy function of the joints. A highly successful surgical procedure to replace the joint with an artificial equivalent alleviates dysfunction and pain. However, the wear of the bearing surfaces in prosthetic joints is a significant clinical problem and more patients are surviving longer than the life expectancy of the joint replacement. Revision surgery is associated with increased morbidity and mortality and has a far less successful outcome than primary joint replacement. As such, it is essential to ensure that everything possible is done to limit the rate of revision surgery. Past experience indicates that the survival rate of the implant will be influenced by many parameters, of primary importance, the material properties of the implant, the composition of the synovial fluid and the method of lubrication. In prosthetic joints, effective boundary lubrication is known to take place. The interaction of the boundary lubricant and the bearing material is of utmost importance. The identity of the vital active ingredient within synovial fluid (SF) to which we owe the near frictionless performance of our articulating joints has been the quest of researchers for many years. Once identified, tribo tests can determine what materials and more importantly what surfaces this fraction of SF can function most optimally with. Surface-Active Phospholipids (SAPL) have been implicated as the body’s natural load bearing lubricant. Studies in this thesis are the first to fully characterise the adsorbed SAPL detected on the surface of retrieved prostheses and the first to verify the presence of SAPL on knee prostheses. Rinsings from the bearing surfaces of both hip and knee prostheses removed from revision operations were analysed using High Performance Liquid Chromatography (HPLC) to determine the presence and profile of SAPL. Several common prosthetic materials along with a novel biomaterial were investigated to determine their tribological interaction with various SAPLs. A pin-on-flat tribometer was used to make comparative friction measurements between the various tribo-pairs. A novel material, Pyrolytic Carbon (PyC) was screened as a potential candidate as a load bearing prosthetic material. Friction measurements were also performed on explanted prostheses. SAPL was detected on all retrieved implant bearing surfaces. As a result of the study eight different species of phosphatidylcholines were identified. The relative concentrations of each species were also determined indicating that the unsaturated species are dominant. Initial tribo tests employed a saturated phosphatidylcholine (SPC) and the subsequent tests adopted the addition of the newly identified major constituents of SAPL, unsaturated phosphatidylcholine (USPC), as the test lubricant. All tribo tests showed a dramatic reduction in friction when synthetic SAPL was used as the lubricant under boundary lubrication conditions. Some tribopairs showed more of an affinity to SAPL than others. PyC performed superior to the other prosthetic materials. Friction measurements with explanted prostheses verified the presence and performance of SAPL. SAPL, in particular phosphatidylcholine, plays an essential role in the lubrication of prosthetic joints. Of particular interest was the ability of SAPLs to reduce friction and ultimately wear of the bearing materials. The identification and knowledge of the lubricating constituents of SF is invaluable for not only the future development of artificial joints but also in developing effective cures for several disease processes where lubrication may play a role. The tribological interaction of the various tribo-pairs and SAPL is extremely favourable in the context of reducing friction at the bearing interface. PyC is highly recommended as a future candidate material for use in load bearing prosthetic joints considering its impressive tribological performance.

New findings with old drugs for osteoporosis

Background : Postmenopausal osteoporosis is common and is associated with stooped posture, loss of height, back pain and fractures. Objectives/methods : This evaluation is of clinical outcome trials with tibolone (Long-Term Intervention of Fractures with Tibolone) and strontium ranelate (Spinal Osteoporosis Therapeutic Intervention) in postmenopausal osteoporosis. Results : Although the Long-Term Intervention of Fractures with Tibolone trial established that tibolone decreased the incidence of vertebral and non-vertebral fractures in postmenopausal osteoporosis, it also showed that tibolone caused a small increase in the incidence of stoke. The Spinal Osteoporosis Therapeutic Intervention trial established that strontium ranelate decreased the incidence of vertebral fractures, but had little effect on the incidence of non-vertebral fractures. Conclusions : As some of the bisphosphonates (alendronate, risedronate, zoledronic acid) have been shown to prevent hip fractures without increasing the incidence of stroke, they should be preferred to tibolone and strontium in the treatment of postmenopausal osteoporosis.

The X-Factor and its relationship to golfing performance

It is often postulated that an increased hip to shoulder differential angle (`X-Factor') during the early downswing better utilises the stretch-shorten cycle and improves golf performance. The current study aims to examine the potential relationship between the X-Factor and performance during the tee-shot. Seven golfers with handicaps between 0 and 10 strokes comprised the low-handicap group, whilst the high-handicap group consisted of eight golfers with handicaps between 11 and 20 strokes. The golfers performed 20 drives and three-dimensional kinematic data were used to quantify hip and shoulder rotation and the subsequent X-Factor. Compared with the low-handicap group, the high-handicap golfers tended to demonstrate greater hip rotation at the top of the backswing and recorded reduced maximum X-Factor values. The inconsistencies evident in the literature may suggest that a universal method of measuring rotational angles during the golf swing would be beneficial for future studies, particularly when considering potential injury.