Assessing accuracy requirements in high tibial osteotomy: a theoretical, computer-based model using AP radiographs.

PURPOSE: High tibial osteotomy (HTO) is a recognised treatment for medial compartment knee arthritis and in recent years has regained popularity. Preoperative planning of wedge opening is based on standing AP radiographs, aiming to deliver the WBL to a desired point. Clinical results can be unpredictable, and this may be due to an inability to deliver the preoperative plan. This study explores the theoretical wedge opening accuracy required to deliver preoperative plans, based on clinical AP radiographs. METHODS: A theoretical 2-D model of osteotomy was developed to determine the degree of radiological wedge opening accuracy required to deliver the weight-bearing line to a preoperative target of 62-66 % of the width of the tibial plateau. RESULTS: This model suggests that, to deliver the weight-bearing line to the preoperative target on plane radiographs, the theoretical medial wedge must be opened to an accuracy of ±0.9 mm. CONCLUSION: Although this study only explores a model of wedge opening based on AP radiographs, with current surgical systems, it is unlikely that the surgeon can achieve this level of accuracy within a real-life surgical setting. Surgical accuracy in HTO is known to be important for both short- and long-term clinical outcomes. This study highlights the need for improved surgical accuracy aids and/or patient stratification to mitigate the effects of surgical errors. LEVEL OF EVIDENCE: II.

Non-invasive imaging of cartilage in early osteoarthritis.

Treatment for osteoarthritis (OA) has traditionally focused on joint replacement for end-stage disease. An increasing number of surgical and pharmaceutical strategies for disease prevention have now been proposed. However, these require the ability to identify OA at a stage when it is potentially reversible, and detect small changes in cartilage structure and function to enable treatment efficacy to be evaluated within an acceptable timeframe. This has not been possible using conventional imaging techniques but recent advances in musculoskeletal imaging have been significant. In this review we discuss the role of different imaging modalities in the diagnosis of the earliest changes of OA. The increasing number of MRI sequences that are able to non-invasively detect biochemical changes in cartilage that precede structural damage may offer a great advance in the diagnosis and treatment of this debilitating condition.

Acoustic, mechanical and near-infrared profiling of osteoarthritic progression in bovine joints.

Early-stage treatments for osteoarthritis are attracting considerable interest as a means to delay, or avoid altogether, the pain and lack of mobility associated with late-stage disease, and the considerable burden that it places on the community. With the development of these treatments comes a need to assess the tissue to which they are applied, both in trialling of new treatments and as an aid to clinical decision making. Here, we measure a range of mechanical indentation, ultrasound and near-infrared spectroscopy parameters in normal and osteoarthritic bovine joints in vitro to describe the role of different physical phenomena in disease progression, using this as a basis to investigate the potential value of the techniques as clinical tools. Based on 72 samples we found that mechanical and ultrasound parameters showed differences between fibrillated tissue, macroscopically normal tissue in osteoarthritic joints, and normal tissue, yet did were unable to differentiate degradation beyond that which was visible to the naked eye. Near-infrared spectroscopy showed a clear progression of degradation across the visibly normal osteoarthritic joint surface and as such, was the only technique considered useful for clinical application.

Damage initiation and progression in the cartilage surface probed by nonlinear optical microscopy.

With increasing interest in treating osteoarthritis at its earliest stages, it has become important to understand the mechanisms by which the disease progresses across a joint. Here, second harmonic generation (SHG) microscopy, coupled with a two-dimensional spring-mass network model, was used to image and investigate the collagen meshwork architecture at the cartilage surface surrounding osteoarthritic lesions. We found that minor weakening of the collagen meshwork leads to the bundling of fibrils at the surface under normal loading. This bundling appears to be an irreversible step in the degradation process, as the stress concentrations drive the progression of damage, forming larger bundles and cracks that eventually form lesions.

Characterization of early stage cartilage degradation using diffuse reflectance near infrared spectroscopy.

Interest in localized and early stage treatment technologies for joint conditions such as osteoarthritis is growing rapidly. It has therefore become important to develop objective measures capable of characterizing the earliest (non-visible) changes associated with degeneration to aid treatment procedures. In addition to assessing tissue before treatment, it is further important to develop an effective, non-destructive means of monitoring post-treatment tissue healing, and of providing the high-quality data needed for trials of developing treatment methods. To investigate its ability to detect the early stages of degeneration in cartilage-on-bone, diffuse reflectance near infrared spectroscopy was applied to normal and osteoarthritic joints. A discriminating function was developed to relate absorbance peaks of interest and track degradation around focal osteoarthritic defects. The function could distinguish between normal and degraded tissue (100% separation of normal tissue from that within 25 mm of a defect) and between different stages of osteoarthritic progression (p < 0.05). This technique allows simple, practical and non-destructive assessment of component-level properties over the full depth of the tissue. It has the potential to increase our understanding of the underlying etiologic and pathogenic processes in early stage degeneration, to assist classification and the development of new treatment methods.

Diffuse reflectance near infrared spectroscopy can distinguish normal from enzymatically digested cartilage.

A non-destructive, diffuse reflectance near infrared spectroscopy (DR-NIRS) approach is considered as a potential tool for determining the component-level structural properties of articular cartilage. To this end, DR-NIRS was applied in vitro to detect structural changes, using principal component analysis as the statistical basis for characterization. The results show that this technique, particularly with first-derivative pretreatment, can distinguish normal, intact cartilage from enzymatically digested cartilage. Further, this paper establishes that the use of DR-NIRS enables the probing of the full depth of the uncalcified cartilage matrix, potentially allowing the assessment of degenerative changes in joint tissue, independent of the site of initiation of the osteoarthritic process.

Assessment of common hyperelastic constitutive equations for describing normal and osteoarthritic articular cartilage.

With the aim of providing information for modelling joint and limb systems, widely available constitutive hyperelastic laws are evaluated in this paper for their ability to predict the mechanical responses of normal and osteoarthritic articular cartilage. Load-displacement data from mechanical indentation were obtained for normal and osteoarthritic cartilage at 0.1 s(-1) and 0.025 s(-1) and converted to the stress-stretch ratio. The data were then fitted to the Arruda-Boyce, Mooney-Rivlin, neo-Hookean, Ogden, polynomial, and Yeoh hyperelastic laws in the MATLAB environment. Although each of the hyperelastic laws performed satisfactorily at the higher rate of loading, their ability to fit experimental data at the lower loading rate varied considerably. For the preferred models, coefficients were provided for stiff, soft, and average tissues to represent normal and degraded tissue at high and low loading rates. The present authors recommend the use of the Mooney-Rivlin or the Yeoh models for describing both normal and degraded articular cartilage, with the Mooney-Rivlin model providing the best compromise between accuracy and required computational power.

An alternative mechanical parameter for assessing the viability of articular cartilage.

This paper is a sequel to previously published findings showing that mechanical indentation alone cannot clearly discriminate between normal and degraded articular cartilage. Consequently, the structural elasticity potential Rc = epsilon r/sigma i, which combines indentation stress sigma i with near-instantaneous rebound epsilon r following unloading, is hypothesized as a potential cartilage assessment parameter, which arguably measures the integrity of the collagen fibre-proteoglycan entrapment system. To establish the validity of our hypothesis, samples of normal intact, artificially degraded, and osteoarthritic bovine cartilage were subjected to quasi-static compression at 0.1 s(-1) and 0.025 s(-1) to 30 per cent strain and then unloaded. A significant reduction in recovery was observed for artificially and naturally degraded samples in the first 5s following unloading (p < 0.01). The structural elasticity potential provided a considerable improvement over the results obtained using the individual indentation and rebound parameters to distinguish between paired normal and artificially degraded samples and indicated a high statistical significance of p < 0.005 when applied to the differentiation of normal and osteoarthritic samples.

Joint laminate degradation assessed by reflected ultrasound from the cartilage surface and osteochondral junction.

The ability to quantify and qualify the progression of joint degeneration is becoming increasingly important in surgery. This paper examines the patterns of relative ultrasound reflection from normal, artificially and naturally degraded cartilage-on-bone, particularly investigating the potential of the ratio of reflection coefficients from the surface and osteochondral junction in distinguishing normal from osteoarthritic tissue. To this end, the reflection coefficients from the articular surface and osteochondral junction of normal cartilage-on-bone samples were calculated and compared to samples after the removal of proteoglycans, disruption of the collagen meshwork, delipidization of the articular surface and mechanical abrasion. Our results show that the large variation across normal and degraded joint samples negates the use of an isolated bone reflection measurement and to a lesser extent, an isolated surface reflection. The relative surface to bone reflections, calculated as a ratio of reflection coefficients, provided a more consistent and statistically significant (p < 0.001) method for distinguishing each type of degradation, especially osteoarthritic degradation, and due to the complementary relationship between surface and bone reflections was found to be an effective method for distinguishing degraded from normal tissue in the osteoarthritic joint, independent of the site of initiation of the osteoarthritic process.

In vitro degradation of articular cartilage: does trypsin treatment produce consistent results?

It is common practice in laboratories to create models of degraded articular cartilage in vitro and use these to study the effects of degeneration on cartilage responses to external stimuli such as mechanical loading. However, there are inconsistencies in the reported action of trypsin, and there is no guide on the concentration of trypsin or the time to which a given sample can be treated so that a specific level of proteoglycan depletion is achieved. This paper argues that before any level of confidence can be established in comparative analysis it is necessary to first obtain samples with similar properties. Consequently, we examine the consistency of the outcome of the artificial modification of cartilage relative to the effects of the common enzyme, trypsin, used in the process of in vitro proteoglycan depletion. The results demonstrate that for a given time and enzyme concentration, the action of trypsin on proteoglycans is highly variable and is dependent on the initial distribution and concentration of proteoglycans at different depths, the intrinsic sample depth, the location in the joint space and the medium type, thereby sounding a note of caution to researchers attempting to model a proteoglycan-based degeneration of articular cartilage in their experimental studies.

Tasco-Forage: III. Influence of a seaweed extract on performance, monocyte immune cell response, and carcass characteristics in feedlot-finished steers.

Tall fescue (Festuca arundinacea Schreb.) infected with the endophyte Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin) causes fescue toxicosis in cattle grazing the forage, but effects of the endophyte were considered to be abated soon after removal of the animals from pastures. Tasco-Forage, a proprietary extract from the brown seaweed Ascophyllum nodosum, is a known source of cytokinins and has increased antioxidant activity in both plants and the animals that graze the forage. Tasco was applied at 0 and 3.4 kg/ha to infected and uninfected tall fescue pastures in Virginia and Mississippi. Forty-eight steers grazed the pastures at each location during each of 2 yr (n = 192) before being transported to Texas for feedlot finishing. On arrival at the feedlot, steers from Tasco-treated pastures had higher (P < 0.01) monocyte phagocytic activity and tended (P < 0.07) to have higher major histocompatibility complex class II expression than steers that grazed the untreated pastures. A depression (P < 0.05) in monocyte immune cell function due to grazing infected fescue was detected throughout the feedlot finishing period but was reversed by Tasco. Rectal temperatures were elevated (P < 0.07) in steers that had grazed the infected tall fescue when they arrived in Texas, but by d 14 no difference was detected. However, by d 28 the temperature effects of infected tall fescue were reversed. Steers that had grazed infected fescue had lower (P < 0.01) rectal temperatures on d 112 of the feedlot period, demonstrating a much longer-lasting effect of the endophyte on thermoregulatory mechanisms than previously thought. Steers that had grazed Tasco-treated pastures had higher (P < 0.01) rectal temperatures on d 56 than steers that had grazed untreated fescue. Steers that had grazed the Tasco-treated pastures had higher marbling scores (P < 0.05) regardless of the endophyte, but no effect of Tasco or endophyte on gain was measured. Our data suggest that Tasco application to tall fescue pastures alleviated some of the negative effects of tall fescue toxicity.

Tasco-Forage: IV. Influence of a seaweed extract applied to tall fescue pastures on sensory characteristics, shelf-life, and vitamin E status in feedlot-finished steers.

Tasco-Forage is an Ascophyllum nodosum seaweed-based product that has increased antioxidant activity in both plants and animals. Endophyte (Neotyphodium coenophialum ([Morgan-Jones and Gams] Glenn, Bacon, and Hanlin)-infected and uninfected tall fescue (Festuca arundinacea Schreb.) pastures in Virginia and Mississippi during 1997 were treated or not with 3.4 kg Tasco/ha in April and July. There were two replications of each treatment at each location. Forty-eight steers (6/replication) grazed pastures at each location (n = 96) from April to October prior to transportation to Texas Tech, Lubbock, for finishing during a 160-d period in the feedlot. Blood (antemortem) and liver (postmortem) samples were collected. After slaughter and chilling, the left strip loins (IMPS #180) were collected from three randomly selected steers from within each pasture replication (n = 48). Strip loins were vacuum-packaged and stored at 2 degrees C. At postmortem d 7, 14, 21, and 28, strip loins were removed from packaging and fabricated into 2.54-cm steaks. Following each fabrication day postmortem, the strip loins were repackaged and stored at 2 degrees C until the following postmortem time. After the prescribed fabrication, steaks were overwrapped with polyvinyl chloride film, subjected to simulated retail display at 2 degrees C for up to 3 d, and subjective and objective color were evaluated daily by a trained panel. Steaks from Mississippi steers that had grazed Tasco-treated fescue retained higher (P < 0.05) CIE a* color scores throughout retail display. Steaks were more uniform and had less discoloration and less browning (P < 0.05) if they were from steers that had grazed Tasco-treated fescue, and the effect was greatest for steers from Mississippi (location x Tasco interaction; P < 0.05). The endophyte in tall fescue may decrease uniformity and increase lean discoloration and two-toning of beef steaks when removed from vacuum packaging on or beyond d 21 postmortem (endophyte x Tasco x postmortem day interaction: P < 0.05). Vitamin E in liver was increased (P < 0.06) and serum vitamin E was decreased (P < 0.09) in steers that had grazed the treated pastures. These experiments indicated that Tasco applied to tall fescue during the grazing season can improve color stability and extend beef shelf-life, particularly in cattle grazing infected tall fescue. The mode of action of Tasco is not clear, but antioxidants and specific vitamins may be involved.

Utilizing hemodynamic delay and dispersion to detect fMRI signal change without auditory interference: the behavior interleaved gradients technique.

A major problem associated with the use of functional magnetic resonance imaging (fMRI) is the attendant gradient noise, which causes undesirable auditory system stimulation. A method is presented here that delays data acquisition to a period immediately after task completion, utilizing the physiological delay and dispersion between neuronal activity and its resulting hemodynamic lag. Subjects performed finger movements with the gradients off, followed by a rest period with the gradients on. This resulted in task-related signals comparable to those obtained with concurrent task performance and image data acquisition. This behavior interleaved gradients technique may be particularly useful for the studies involving auditory stimulation or overt verbal responses.

Sex and hemispheric differences for rapid auditory processing in normal adults.

Previous research suggests that left hemisphere specialisation for processing speech may specifically depend on rate-specific parameters, with rapidly successive or faster changing acoustic stimuli (e.g. stop consonant-vowel syllables) processed preferentially by the left hemisphere. The current study further investigates the involvement of the left hemisphere in processing rapidly changing auditory information, and examines the effects of sex on the organisation of this function. Twenty subjects participated in an auditory discrimination task involving the target identification of a two-tone sequence presented to one ear, paired with white noise to the contralateral ear. Analyses demonstrated a right ear advantage for males only at the shorter interstimulus interval durations (mean = 20 msec) whereas no ear advantage was observed for women. These results suggest that the male brain is more lateralised for the processing of rapidly presented auditory tones, specifically at shorter stimulus durations.

Influence of Neotyphodium coenophialum on copper concentration in tall fescue.

Poor performance of livestock that graze tall fescue (Festuca arundinacea Schreb.) has been associated with the endophyte fungus Neotyphodium coenophialum [Morgan-Jones and Gams] Glenn, Bacon, and Hanlin). Recent evidence suggests lowered Cu status and a depression of Cu-related immune function in steers that graze endophyte-infected (E+) tall fescue. Greenhouse and field studies investigated relationships between the endophyte and Cu concentrations in tall fescue. Seventeen infected 'Kenhy' clones were divided, and one plant of each pair was treated three times with Benomyl to remove the endophyte (E-). Plants were watered with nutrient solution in a greenhouse for 6 mo before sampling. Copper concentrations were greater (P < .001) in E- than in E+ clones (3.4 vs 2.8 microg/g; SE, .06). In the second greenhouse experiment, genetically similar E+ and E- 'Kentucky'-31 (KY-31) and 'Georgia Jessup' were grown from seed and fertilized with nutrient solution to produce mature plants. Copper concentrations were higher (P < .05) in E- than in E+ tall fescue (8.6 vs 7.6 microg/g; SE, .3). In a field plot experiment in Texas, E+ and E- KY-31 were grown with 0, 50, and 100% replacement of potential evapotranspiration. By September, Cu concentrations were higher (P < .05) in E- than in E+ tall fescue (7.3 vs 6.6 microg/g; SE, .2). In pasture experiments, KY-31 E+ (> 70% infection level) and E- (< 5% infection level) tall fescue were grown in Virginia at two locations with three rates of N fertilizer. Copper concentrations were higher (P < .05) in E- than in E+ tall fescue (4.8 vs 4.5 microg/g; SE, .1) and increased (P < .01) linearly in response to N. Our data demonstrate that the presence of the endophyte is associated with lower Cu concentrations in tall fescue, which may contribute to lowered Cu status in animals and thus contribute to the etiology of fescue toxicity.

Effects of sex and MK-801 on auditory-processing deficits associated with developmental microgyric lesions in rats.

Neonatally induced microgyric lesions produce defects in rapid auditory processing in adult male rats. Given that females across species are less susceptible to the deleterious effects of neural injury and that treatment with neuroprotective agents at the time of injury can reduce neural damage, the authors tested the effects of sex and neuroprotectant exposure on the behavioral consequences of microgyric lesions in rats. Results showed that sham but not microgyric males were able to perform the task at the fastest rate of stimulus presentation. Microgyric females, in contrast, discriminated at all stimulus conditions and did not differ from female shams. Microgyric males treated with MK-801 had reduced cortical damage and performed the discrimination at the fastest condition. Results suggest that females are less susceptible to the behavioral effects of neocortical microgyria and that MK-801 may ameliorate the behavioral consequences of these lesions in male rats.

Prevalence of enteric parasitic infection among HIV-infected attendees of an inner city AIDS clinic.

One hundred individuals confirmed to be infected with the human immunodeficiency virus (HIV), volunteered to participate in a pilot study comparing clinical status and enteric parasite burden with race, age, CD4 levels, risk factors and sexual practice. The prevalence of enteric parasites was 55 (55%) for Giardia lamblia, 6 (6%) for Cryptosporidium, 10 (10%) for Isospora belli and 3 (3%) for Entamoeba histolytica. There was no associations between demographic variables and the presence of parasites. The presence of giardia was significantly associated with anal-penile sex (P = .017), with an odds ratio of 2.9. A logistic regression model was used to explain the presence of any parasite by a number of sexual practices. The only practice found to be significant was anal-penile sex, which substantially increased the likelihood of the presence of the parasites. In this regression, 38.5% of pairs were concordant and 12.2% were discordant. These findings differed from surveys conducted in similar populations. The significance of this will be discussed in the context of medical service provision to this and similar populations.

The urban church and cancer control: a source of social influence in minority communities.

A study was conducted to examine the efficacy of a church-based model of social influence in improving access to and participation of underserved minority women in a cervical cancer control program. The model expanded on strategies used in previous hypertension control and health promotion research. A total of 24 churches, stratified by faith tradition, were randomly selected to participate in the cancer control program from a pool of 63 churches in a defined geographic area of Los Angeles County, CA. Female parishioners ages 21 years and older were eligible to participate in cervical cancer education sessions, and screening was offered to adult women who had not had Papanicolaou tests within the last 2 years. Church participation rate was 96 percent. Thirty lay health leaders were selected by the clergy to serve as messengers, recruiters, and organizers for their respective congregations. Ninety-seven percent of these lay health leaders participated in two training sessions designed to prepare them for their leadership role. Social support structures such as child care, meals, or transportation for targeted women were organized by lay health leaders in 78 percent of the churches. A total of 1,012 women between the ages of 21 and 89 years attended educational sessions. Forty-four percent of the eligible women were targeted for screening because they had not had a Papanicolaou test within the last 2 years or had never been screened. Black women were 6.6 times more likely than Hispanics to have been screened in the past 2 years. Hispanic women were 4.2 times more likely than African Americans never to have had a Papanicolaou test or been tested in 3 or more years.Overall, 90 percent of the women targeted for screening recruitment presented for tests.Fifty-two percent of the churches initiated cancer control activities by the end of the 2-year period following the culmination of the intervention program.The findings suggest that a church-based model of social influence can leverage the participation of minority women in cervical cancer control, provide access to underserved Hispanic women in particular,and sustain cancer control activities beyond the life of an intervention program.The findings further suggest that a more discrete assessment of screening history may improve the participation levels of African American women, and that the gratis offering of screening services may adversely affect their participation rates.

HIV-1 seroprevalence in an inner-city public hospital.

In a hospital-based seroprevalence survey for human immunodeficiency virus type 1 (HIV-1) infection, a stratified sampling method based on age and gender was used to collect 5429 blood samples at an inner-city hospital. Sentinel Hospital Surveillance System (SHSS) criteria developed by the Centers for Disease Control and Prevention were used to classify patient diagnoses into two categories by the likelihood of being associated with HIV-1 infection. The two categories were those with high likelihood of association with HIV-1 (SHSS-ineligible) and those with low likelihood of association with HIV-1 infection (SHSS-eligible). Of the 5429 blood samples, 4262 were SHSS-eligible and 1167 were SHSS-ineligible. After personal identifies were removed, specimens were tested by ELISA and confirmed by Western blot analysis. The overall prevalence rate of HIV-1 infection was 0.98%. The seroprevalence rate was almost 2.6 times higher in high-association patients compared with low-association patients (1.89% versus 0.73%, P < .001). Results from this study indicate a high unsuspected HIV-1 seroprevalence rate in a subpopulation (SHSS-eligible) considered to have diagnoses with low likelihood of association with HIV-1 infection. These patients may better approximate HIV-1 seroprevalence in the general population of the area served by the hospital than would a sample of all patients. Monitoring HIV-1 seroprevalence in the SHSS-eligible group will be a useful measure for community serosurveillance for HIV-1 infection.