Can we define envelope of laxity during navigated knee arthroplasty?

PURPOSE

Functional outcomes after knee arthroplasty (TKA) remain poor. The ability to restore the soft tissue envelope intraoperatively may improve such outcomes. The aim of this study was to extend the scope of computer navigation as a tool to quantifying the envelope of laxity during subjective stress testing preoperatively and to quantify the effects of knee replacement and how it changes as a result of ligamentous failure.

METHODS

Loaded cadaveric legs were mounted on a purpose-built rig. Envelope of laxity was measured in 3 degrees of freedom using computer navigation. Knees were subjectively stressed in varus/valgus, internal/external rotation and anterior draw. This was performed preoperatively, during TKA and after sequential sectioning of ligaments. Real-time data were recorded at 0°, 30°, 60° and 90° of flexion. Mixed effect modelling was used to quantify the effects of intervention on degree of laxity.

RESULTS

In all cases, there was an increase in laxity with increasing flexion or ligament sectioning. Operator and movement cycle had no effect. Insertion of a TKA showed increased stability within the joint, especially in internal/external rotation and anterior drawer. Once the PCL and popliteus were cut, the implant only maintained some rotatory stability; thereafter, the soft tissue envelope failed.

CONCLUSIONS

This work has shown a novel way by which computer navigation can be used to analyse soft tissue behaviour during TKA beyond the coronal plane and throughout range of motion. Despite subjective stress testing, our results show reproducible patterns of soft tissue behaviour-in particular a wide range of mid-flexion excursion. It also quantifies the limits within which a cruciate-retaining TKR can maintain knee stability. This functionality may guide the surgeon in identifying and/or preventing soft tissue imbalances intra-operatively, improving functional results.

Infection-interactions in Ethiopian village chickens

Chickens raised under village production systems are exposed to a wide variety of pathogens, and current or previous infections may affect their susceptibility to further infections with another parasite, and/or can alter the manifestation of each infection. It is possible that co-infections may be as important as environmental risk factors. However, in cross-sectional studies, where the timing of infection is unknown, apparent associations between infections may be observed due to parasites sharing common risk factors. This study measured antibody titres to 3 viral (Newcastle disease, Marek's disease and infectious bursal disease) and 2 bacterial (Pasteurella multocida and Salmonella) diseases, and the infection prevalence of 3 families of endo- and ecto-parasites (Ascaridida, Eimeria and lice) in 1056 village chickens from two geographically distinct populations in Ethiopia. Samples were collected during 4 cross-sectional surveys, each approximately 6 months apart. Constrained ordination, a technique for analysis of ecological community data, was used to explore this complex dataset and enabled potential relationships to be uncovered and tested despite the different measurements used for the different parasites. It was found that only a small proportion of variation in the data could be explained by the risk factors measured. Very few birds (9/1280) were found to be seropositive to Newcastle disease. Positive relationships were identified between Pasteurella and Salmonella titres; and between Marek's disease and parasitic infections, and these two groups of diseases were correlated with females and males, respectively. This may suggest differences in the way that the immune systems of male and female chickens interact with these parasites. In conclusion, we find that a number of infectious pathogens and their interactions are likely to impact village chicken health and production. Control of these infections is likely to be of importance in future development planning.

Patient satisfaction with total knee replacement cannot be predicted from pre-operative variables alone: A cohort study from the National Joint Registry for England and Wales

Pre-operative variables are increasingly being used to determine eligibility for total knee replacement (TKR). This study was undertaken to evaluate the relationships, interactions and predictive capacity of variables available pre- and post-operatively on patient satisfaction following TKR. Using nationally collected patient reported outcome measures and data from the National Joint Registry for England and Wales, we identified 22 798 patients who underwent TKR for osteoarthritis between August 2008 and September 2010. The ability of specific covariates to predict satisfaction was assessed using ordinal logistic regression and structural equational modelling. Only 4959 (22%) of 22 278 patients rated the results of their TKR as 'excellent', despite the majority (71%, n = 15 882) perceiving their knee symptoms to be much improved. The strongest predictors of satisfaction were post-operative variables. Satisfaction was significantly and positively related to the perception of symptom improvement (operative success) and the post-operative EuroQol-5D score. While also significant within the models pre-operative variables were less important and had a minimal influence upon post-operative satisfaction. The most robust predictions of satisfaction occurred only when both pre- and post-operative variables were considered together. These findings question the appropriateness of restricting access to care based on arbitrary pre-operative thresholds as these factors have little bearing on post-operative satisfaction.

Congenital hepatic fibrosis in 5 dogs

Congenital hepatic fibrosis is a disorder of biliary system development histologically characterized by diffuse periportal to bridging fibrosis with numerous small often-irregular bile ducts and reduction in the number of portal vein branches. The condition results from abnormal development of the ductal plate, the embryonic precursor to the interlobular bile ducts. It has rarely been reported in veterinary species, and it has never been reported in dogs. This article describes 5 cases of a ductal plate malformation in dogs consistent with congenital hepatic fibrosis. On light microscopy, all 5 livers had severe bridging fibrosis with a marked increase in the number of small bile ducts, which often had irregular, dilated profiles reminiscent of the developing ductal plate. In addition, 80% (4 of 5) of cases lacked typical portal vein profiles. Cytokeratin 7 and proliferating cell nuclear antigen immunohistochemistry was performed on the 3 cases for which paraffin-embedded tissue was available. The bile duct profiles were strongly positive for cytokeratin 7 in all 3 cases, and they were negative for proliferating cell nuclear antigen or only had rare positive cells. All 5 dogs presented with clinical signs of portal hypertension. Congenital hepatic fibrosis should be considered in the differential diagnosis in young dogs that present with portal hypertension and lesions that may have been interpreted as bridging biliary hyperplasia or extrahepatic biliary obstruction.

No association between ambient particulate matter exposure during pregnancy and stillbirth risk in the north of England, 1962-1992

OBJECTIVES

Research evidence suggests that exposure to ambient air pollutants can adversely affect the growth and development of the foetus and infant survival. Much less is known regarding the potential for an association between black smoke air pollution and stillbirth risk. This potential association was examined using data from the historical cohort UK Particulate Matter and Perinatal Events Research (PAMPER) study.

METHODS

Using data from paper-based neonatal records from the two major maternity hospitals in Newcastle upon Tyne (UK), a birth record database of all singletons born during 1961-1992 to mothers resident in the city was constructed. Weekly black smoke levels were obtained from routine data recorded at 20 air pollution monitoring stations over the study period. A two-stage statistical modelling strategy was used, incorporating temporally and spatially varying covariates to estimate black smoke exposure during each trimester and for the whole pregnancy period for each individual pregnancy. Conditional logistic regression models, with stratification on year of birth, were used to assess potential associations between black smoke exposures in pregnancy and stillbirth risk.

RESULTS

The PAMPER database consists of 90,537 births, between 1962 and 1992, with complete gestational age and residential address information, of which 812 were stillborn. There was no association between black smoke exposures in any trimester or across whole pregnancy and risk of stillbirth. Adjustment for potential confounders did not alter these results.

CONCLUSIONS

While black smoke in pregnancy is likely to be related to other pregnancy outcomes, our findings do not suggest that black smoke air pollution exposure during pregnancy increases the risk of stillbirth.

Bovine tuberculosis in cattle: reduced risk on wildlife-friendly farms

The associations between habitat and other factors that lead to the risk of bovine tuberculosis (bTB) in diary cattle were examined in an unmatched case-control study. Data from 60 herds with recent history of bTB and 60 controls were analysed using logistic regression. The predictors included farmland habitat, topography, indices of badger density and herd size. Information-theoretic approaches were used to identify those predictor variables explaining the greatest variation in cattle herd bTB breakdowns. Reduced risk of bTB was associated with the management of farmland in ways favourable to wildlife conservation, as encouraged by recent (2005) European Common Agricultural Policy reforms.

Biodiversity in urban habitat patches

We examined the biodiversity of urban habitats in Birmingham (England) using a combination of field surveys of plants and carabid beetles, genetic studies of four species of butterflies, modelling the anthropochorous nature of the floral communities and spatially explicit modelling of selected mammal species. The aim of the project was to: (i) understand the ecological characteristics of the biota of cities model, (ii) examine the effects of habitat fragment size and connectivity upon the ecological diversity and individual species distributions, (iii) predict biodiversity in cities, and (iv) analyse the extent to which the flora and fauna utilise the 'urban greenways' both as wildlife corridors and as habitats in their own right. The results suggest that cities provide habitats for rich and diverse range of plants and animals, which occur sometimes in unlikely recombinant communities. The studies on carabids and butterflies illustrated the relative importance of habitat quality on individual sites as opposed to site location within the conurbation. This suggests that dispersal for most of our urban species is not a limiting factor in population persistence, although elements of the woodland carabid fauna did appear to have some geographical structuring. Theoretical models suggested that dormice and water voles may depend on linear habitats for dispersal. The models also indicated that other groups, such as small and medium sized mammals, may use corridors, although field-based research did not provide any evidence to suggest that plants or invertebrates use urban greenways for dispersal. This finding indicates the importance of identifying a target species or group of species for urban greenways intended as dispersal routeways rather than as habitat in their own right. Their importance for most groups is rather that greenways provide a chain of different habitats permeating the urban environment. We suggest that planners can have a positive impact on urban biodiversity by slowing the pace of redevelopment and by not hurrying to tidy up and redevelop brownfield sites.

Minimal requirements for the binding of selectin ligands to a C-type carbohydrate-recognition domain

The C-type carbohydrate-recognition domains of E-selectin and rat serum mannose-binding protein have similar structures. Selectin/mannose-binding protein chimeras created by transfer of key sequences from E-selectin into mannose-binding protein have previously been shown to bind the selectin ligand sialyl-Lewis(X) through a Ca(2+)-dependent subsite, common to many C-type lectins, and an accessory site containing positively charged amino acid residues. Further characterization of these chimeras as well as analysis of novel constructs containing additional regions of E-selectin demonstrate that selectin-like interaction with sialyl-Lewis(X) can be faithfully reproduced even though structural evidence indicates that the mechanisms of binding to E-selectin and the chimeras are different. Selectin-like binding to the nonfucosylated sulfatide and sulfoglucuronyl glycolipids can also be reproduced with selectin/mannose-binding protein chimeras that contain the two subsites involved in sialyl-Lewis(X) binding. These results indicate that binding of structurally distinct anionic glycans to C-type carbohydrate-recognition domains can be mediated by the Ca(2+)-dependent subsite in combination with a positively charged region that forms an ionic strength-sensitive subsite.

Impact of landscape management on the genetic structure of red squirrel populations

Landscape management practices that alter the degree of habitat fragmentation can significantly affect the genetic structure of animal populations. British red squirrels use "stepping stone" patches of habitat to move considerable distances through a fragmented habitat. Over the past few decades, the planting of a large conifer forest has connected groups of forest fragments in the north of England with those in southern Scotland. This "defragmentation" of the landscape has resulted in substantial genetic mixing of Scottish and Cumbrian genes in squirrel populations up to 100 kilometers from the site of the new forest. These results have implications for the conservation management of animal and plant species in fragmented landscapes such as those found in Britain.

Virtual reality: a new prosthesis for brain injury rehabilitation

Virtual Reality (VR) technology is a relatively new application to rehabilitation medicine, yet it offers considerable potential to achieve significant successes in assessment, treatment and improved outcome, thereby increasing our knowledge of neuroplasticity. The capabilities of VR are especially evident in neurological rehabilitation, where cognitive and behavioural problems often interact with physical impairments to reduce the overall level of functioning and interaction. The need for effective interventions in neurological rehabilitation demands communication and collaboration between disciplines. This paper presents some of the current areas of the clinical applications of VR, emphasising the link between experimental evidence on recovery after brain damage and the clinical problems encountered in a ward setting.