IPNA clinical practice recommendations for the diagnosis and management of children with steroid-sensitive nephrotic syndrome

Idiopathic nephrotic syndrome is the most frequent pediatric glomerular disease, affecting from 1.15 to 16.9 per 100,000 children per year globally. It is characterized by massive proteinuria, hypoalbuminemia, and/or concomitant edema. Approximately 85-90% of patients attain complete remission of proteinuria within 4-6 weeks of treatment with glucocorticoids, and therefore, have steroid-sensitive nephrotic syndrome (SSNS). Among those patients who are steroid sensitive, 70-80% will have at least one relapse during follow-up, and up to 50% of these patients will experience frequent relapses or become dependent on glucocorticoids to maintain remission. The dose and duration of steroid treatment to prolong time between relapses remains a subject of much debate, and patients continue to experience a high prevalence of steroid-related morbidity. Various steroid-sparing immunosuppressive drugs have been used in clinical practice; however, there is marked practice variation in the selection of these drugs and timing of their introduction during the course of the disease. Therefore, international evidence-based clinical practice recommendations (CPRs) are needed to guide clinical practice and reduce practice variation. The International Pediatric Nephrology Association (IPNA) convened a team of experts including pediatric nephrologists, an adult nephrologist, and a patient representative to develop comprehensive CPRs on the diagnosis and management of SSNS in children. After performing a systematic literature review on 12 clinically relevant PICO (Patient or Population covered, Intervention, Comparator, Outcome) questions, recommendations were formulated and formally graded at several virtual consensus meetings. New definitions for treatment outcomes to help guide change of therapy and recommendations for important research questions are given.

IPNA clinical practice recommendations for the diagnosis and management of children with steroid-resistant nephrotic syndrome

Idiopathic nephrotic syndrome newly affects 1-3 per 100,000 children per year. Approximately 85% of cases show complete remission of proteinuria following glucocorticoid treatment. Patients who do not achieve complete remission within 4-6 weeks of glucocorticoid treatment have steroid-resistant nephrotic syndrome (SRNS). In 10-30% of steroid-resistant patients, mutations in podocyte-associated genes can be detected, whereas an undefined circulating factor of immune origin is assumed in the remaining ones. Diagnosis and management of SRNS is a great challenge due to its heterogeneous etiology, frequent lack of remission by further immunosuppressive treatment, and severe complications including the development of end-stage kidney disease and recurrence after renal transplantation. A team of experts including pediatric nephrologists and renal geneticists from the International Pediatric Nephrology Association (IPNA), a renal pathologist, and an adult nephrologist have now developed comprehensive clinical practice recommendations on the diagnosis and management of SRNS in children. The team performed a systematic literature review on 9 clinically relevant PICO (Patient or Population covered, Intervention, Comparator, Outcome) questions, formulated recommendations and formally graded them at a consensus meeting, with input from patient representatives and a dietician acting as external advisors and a voting panel of pediatric nephrologists. Research recommendations are also given.

Steroid-sensitive nephrotic syndrome: an evidence-based update of immunosuppressive treatment in children

Nephrotic syndrome is one of the most common paediatric glomerular diseases, with an incidence of around two per 100,000 children per year. Corticosteroids are the mainstay of treatment, with 85%-90% of children going into remission with an 8-week course of treatment. Unfortunately, nephrotic syndrome follows a relapsing and remitting course in the majority, with 90% relapsing at least once. About half will progress to frequently relapsing nephrotic syndrome (FRNS) or steroid-dependent nephrotic syndrome (SDNS). Different initial steroid regimens have been evaluated since the first trials in Europe and America in the 1960s. Most trials have been designed to evaluate the optimal duration of the initial therapy, rather than different cumulative doses of corticosteroid, or the management of relapses. Until recently, these data suggested that an initial treatment duration of up to 6 months reduced the number of children developing a relapse, without evidence of increased steroid toxicity. Recently, three large, well-designed randomised control trials were published, which demonstrated no significant reduction in risk of relapse or of developing FRNS by extended treatment compared with 2 or 3 months. While there are few trial data to guide the treatment of individual relapses in steroid-sensitive nephrotic syndrome (SSNS), there is some evidence that a short course of corticosteroid therapy during upper respiratory tract infection may prevent relapse. In patients with FRNS or SDNS who continue to relapse despite low-dose alternate-day steroids a number of non-corticosteroid, steroid-sparing immunosuppressive agents (cyclophosphamide, ciclosporin, tacrolimus, mycophenolate mofetil, levamisole, rituximab) have been shown to reduce the risk of relapse and of FRNS. However, there are limited head-to-head data to inform which agent should be preferred. In this article, we review recent data from randomised trials to update paediatricians on the current evidence supporting interventions in SSNS.

The treatment of stable paediatric forearm fractures using a cast that may be removed at home

We investigated whether, in the management of stable paediatric fractures of the forearm, flexible casts that can be removed at home are as clinically effective, cost-effective and acceptable to both patient and parent as management using a cast conventionally removed in hospital. A single-centre randomised controlled trial was performed on 317 children with a mean age of 9.3 years (2 to 16). No significant differences were seen in the change in Childhood Health Assessment Questionnaire index score (p = 0.10) or EuroQol 5-Dimensions domain scores between the two groups one week after removal of the cast or the absolute scores at six months. There was a significantly lower overall median treatment cost in the group whose casts were removed at home (£150.88 (sem 1.90) vs £251.62 (sem 2.68); p <  0.001). No difference was seen in satisfaction between the two groups (p = 0.48).

Cite this article: Bone Joint J 2013;95-B:1714–20.

Adolescent views on transition in diabetes and nephrology

Managing the transition of adolescents from paediatric to adult care is complex and remains an important challenge. This aim of this study was to synthesize studies on perspective on transition to adult care among young people with diabetes or chronic kidney disease. We conducted a systematic review of surveys and qualitative studies that explored adolescent perspectives on transition to adult care in diabetes and chronic kidney disease. Searches were conducted to week 4, June 2010. For quantitative questionnaires, all items were mapped into a domain schema. Thematic synthesis of the qualitative findings was performed. Fourteen studies involving 854 respondents were included. The majority of participants felt somewhat prepared but had reservations about transfer. Five major themes were identified: (1) preparedness (timing of transfer, access to providers, parental involvement), (2) overwhelmed by an impersonal environment in adult service (sterile and unwelcoming, navigating new processes, feeling displaced), (3) independence (developing self-esteem and an adult identity, taking responsibility and ownership), (4) valuing familiarity (building trust, peer support) and (5) service and information needs (leniency, lack of access, efficiency, information needs).

CONCLUSION

Holistic and adolescent focussed transition programs are needed which address adolescent needs by providing adequate access to health services, encouraging independence and ownership of health management, promoting trust in providers, giving comprehensive information about what to expect and how to navigate adult services and facilitating interaction with younger patients.

An economic evaluation of intravenous versus oral iron supplementation in people on haemodialysis

BACKGROUND

Iron supplementation can be administered either intravenously or orally in patients with chronic kidney disease (CKD) and iron deficiency anaemia, but practice varies widely. The aim of this study was to estimate the health care costs and benefits of parenteral iron compared with oral iron in haemodialysis patients receiving erythropoiesis-stimulating agents (ESAs).

METHODS

Using broad health care funder perspective, a probabilistic Markov model was constructed to compare the cost-effectiveness and cost-utility of parenteral iron therapy versus oral iron for the management of haemodialysis patients with relative iron deficiency. A series of one-way, multi-way and probabilistic sensitivity analyses were conducted to assess the robustness of the model structure and the extent in which the model's assumptions were sensitive to the uncertainties within the input variables.

RESULTS

Compared with oral iron, the incremental cost-effectiveness ratios (ICERs) for parenteral iron were $74,760 per life year saved and $34,660 per quality-adjusted life year (QALY) gained. A series of one-way sensitivity analyses show that the ICER is most sensitive to the probability of achieving haemoglobin (Hb) targets using supplemental iron with a consequential decrease in the standard ESA doses and the relative increased risk in all-cause mortality associated with low Hb levels (Hb < 9.0 g/dL). If the willingness-to-pay threshold was set at $50,000/QALY, the proportions of simulations that showed parenteral iron was cost-effective compared with oral iron were over 90%.

CONCLUSIONS

Assuming that there is an overall increased mortality risk associated with very low Hb level (<9.0 g/dL), using parenteral iron to achieve an Hb target between 9.5 and 12 g/L is cost-effective compared with oral iron therapy among haemodialysis patients with relative iron deficiency.

Population pharmacokinetics of mycophenolic acid in children and young people undergoing blood or marrow and solid organ transplantation

AIMS

To characterize the population pharmacokinetics of mycophenolic acid (MPA) and evaluate dose regimens using a simulation approach and accepted therapeutic drug monitoring targets in children and young people undergoing blood or marrow, kidney and liver transplantation.

METHODS

MPA concentration-time data were collected using an age specific sampling protocol over 12h. Some patients provided randomly timed but accurately recorded blood samples. Total and unbound MPA were measured by HPLC. NONMEM was employed to analyze MPA pharmacokinetic data. Simulations (n= 1000) were conducted to assess the suitability of the MPA dose regimens to maintain total MPA AUC(0,12h) within the range 30 and 60mg l(-1) h associated with optimal outcome.

RESULTS

A two-compartment pharmacokinetic model with first-order elimination best described MPA concentration-time data. Population mean estimates of MPA clearance, inter-compartmental clearance, volumes of distribution in the central and peripheral compartments, absorption rate constant and bioavailability were 6.42 l h(-1) , 3.74 l h(-1) , 7.24 l, 16.8l, 0.39h(-1) and 0.48, respectively. Inclusion of bodyweight and concomitant ciclosporin reduced the inter-individual variability in CL from 54.3% to 31.6%. Children with a bodyweight of 10kg receiving standard MPA dose regimens achieve an MPA AUC below the target range suggesting they may be at a greater risk of acute rejection.

CONCLUSIONS

The population pharmacokinetic model for MPA can be used to explore dosing guidelines for safe and effective immunotherapy in children and young people undergoing transplantation.

Absolute and relative accuracy of rapid urine tests for urinary tract infection in children: a meta-analysis

Rapid urine tests, such as microscopy, for bacteria and white cells, and dipsticks, for leucocyte esterase and nitrites, are often used in children that are unwell to guide early diagnosis and treatment of urinary tract infection. We aimed to establish whether these tests were sufficiently sensitive to avoid urine culture in children with negative results and to compare the accuracy of dipsticks with microscopy. Medline, Embase, and reference lists were searched. Studies were included if urine culture results were compared with rapid tests in children. Data were analysed to obtain absolute and relative accuracy estimates. Data from 95 studies in 95 703 children were analysed. Summary estimates for sensitivity and specificity for microscopy for Gram-stained bacteria were 91% (95% CI 80-96) and 96% (92-98), for unstained bacteria were 88% (75-94) and 92% (84-96), for urine white cells were 74% (67-80) and 86% (82-90), for leucocyte esterase or nitrite positive dipstick were 88% (82-91) and 79% (69-87), and for nitrite-only positive dipstick were 49% (41-57) and 98% (96-99). Microscopy for bacteria with Gram stain had higher accuracy than other laboratory tests with relative diagnostic odds ratio compared with bacteria without Gram stain of 8.7 (95% CI 1.8-41.1), white cells of 14.5 (4.7-44.4), and nitrite of 22.0 (0.7-746.3). Microscopy for white cells should not be used for the diagnosis of urinary tract infection because its accuracy is no better than that of dipstick, laboratory facilities are needed, and results are delayed. Rapid tests are negative in around 10% of children with a urinary tract infection and cannot replace urine culture. If resources allow, microscopy with Gram stain should be the single rapid test used.

Diagnostic accuracy of urine dipsticks for detecting albuminuria in indigenous and non-indigenous children in a community setting

Albuminuria predicts cardiovascular and end-stage kidney disease in indigenous populations. Early detection in indigenous children may identify those who could benefit from early treatment. Community-based detection of albuminuria needs to be performed using a reliable, inexpensive, and widely available test, such as a proteinuria dipstick. Dipstick accuracy for detecting albuminuria in a community setting has not been evaluated. We assessed the accuracy of Multistix 10 SG dipsticks to detect baseline albuminuria and predict for persistent albuminuria at a 2-year follow-up in a population-based cohort of Australian Aboriginal and non-Aboriginal elementary-school-aged children. Variability in the accuracy of dipsticks in subgroups of higher risk children was analyzed using the relative diagnostic odds ratio (RDOR). Using Multistix 10 SG dipsticks, index-test-positive cases were defined as >/=0.30 g/L (1+) proteinuria and index-test-negative cases as <0.30 g/L (negative or trace) proteinuria. Referent-test-positive cases were defined as spot albumin:creatinine (ACR) >/=3.4 mg/mmol, and referent-test-negative cases as ACR <3.4 mg/mmol. There were 2,266 children (55.1% Aboriginal, 51.0% boys, mean age 8.9 years) enrolled. At the 2-year follow-up, 1,432 (63.0%) children were retested (54.0% Aboriginal, 50.5% boys, mean age 10.5 years). Prevalence of baseline albuminuria was 7.3%, and persistent albuminuria was 1.5%. Dipsticks had a sensitivity of 62% and specificity of 97% at baseline. In predicting persistent albuminuria, sensitivity was 75% and specificity 93%. Accuracy did not vary with ethnicity, gender, or body mass index. Accuracy was less in younger children (4.0-7.9 years), and in those with hematuria. The performance characteristics of Multistix dipsticks make them suitable for albuminuria detection in Aboriginal and other higher-risk groups of children. More than two thirds of children detected at a single test will have transient rather than persistent albuminuria. Multistix dipsticks are particularly useful for detecting children who will have persistent albuminuria.

Early chronic kidney disease in Aboriginal and non-Aboriginal Australian children: remoteness, socioeconomic disadvantage or race?

Indigenous people suffer substantially more end-stage kidney disease (ESKD), especially Australian Aboriginals. Previous work suggests causal pathways beginning early in life. No studies have shown the prevalence of early markers of chronic kidney disease (CKD) in both Indigenous and non-Indigenous children or the association with environmental health determinants--geographic remoteness and socioeconomic disadvantage. Height, weight, blood pressure, and urinary abnormalities were measured in age- and gender-matched Aboriginal and non-Aboriginal children from elementary schools across diverse areas of New South Wales, Australia. Hematuria was defined as>or=25 red blood cells/microl (>or=1+), proteinuria>or=0.30 g/l (>or=1+), and albuminuria (by albumin:creatinine)>or=3.4 mg/mmol. Remoteness and socioeconomic status were assigned using the Accessibility and Remoteness Index of Australia and Socio-Economic Indexes For Areas. From 2002 to 2004, 2266 children (55% Aboriginal, mean age 8.9 years) were enrolled from 37 elementary schools. Overall prevalence of hematuria was 5.5%, proteinuria 7.3%, and albuminuria 7.3%. Only baseline hematuria was more common in Aboriginal children (7.1 versus 3.6%; P=0.002). At 2-year follow-up, 1.2% of Aboriginal children had persistent hematuria that was no different from non-Aboriginal children (P=0.60). Socioeconomic disadvantage and geographical isolation were neither significant nor consistent risk factors for any marker of CKD. Aboriginal children have no increase in albuminuria, proteinuria, or persistent hematuria, which are more important markers for CKD. This suggests ESKD in Aboriginal people may be preventable during early adult life.

Nutrition and growth in kidney disease: CARI guidelines

The Caring for Australasians with Renal Impairment (CARI) guidelines initiative is an Australia/New Zealand evidence based project that aims to provide high quality, evidence based clinical practice guidelines for the management of all stages of kidney disease. This article summarises CARI guidelines on Nutrition and growth in kidney disease and forms part of a series of articles on aspects of management of patients with chronic kidney disease.

4. Bedwetting and toileting problems in children

Bedwetting (nocturnal enuresis) is common. It occurs in up to 20% of 5 year olds and 10% of 10 year olds, with a spontaneous remission rate of 14% per year. Weekly daytime wetting occurs in 5% of children, most of whom (80%) also wet the bed. Bedwetting can have a considerable impact on children and families, affecting a child's self-esteem and interpersonal relationships, and his or her performance at school. Primary nocturnal enuresis (never consistently dry at night) should be distinguished from secondary nocturnal enuresis (previously dry for at least 6 months). Important risk factors for primary nocturnal enuresis include family history, nocturnal polyuria, impaired sleep arousal and bladder dysfunction. Secondary nocturnal enuresis is more likely to be caused by factors such as urinary tract infections, diabetes mellitus and emotional stress. The treatment for monosymptomatic nocturnal enuresis (bedwetting with no daytime symptoms) is an alarm device, with desmopressin as second-line therapy. Treatment for non-monosymptomatic nocturnal enuresis (bedwetting with daytime symptoms--urgency and frequency, with or without incontinence) should initially focus on the daytime symptoms.Bedwetting without daytime symptoms, the most common toileting problem, can be effectively treated with an alarm device.

Interventions for idiopathic steroid-resistant nephrotic syndrome in children

BACKGROUND

The majority of children, who present with their first episode of nephrotic syndrome, achieve remission with corticosteroid therapy. Children who fail to respond to corticosteroids may be treated with immunosuppressive agents such as cyclophosphamide, chlorambucil or cyclosporin or with non-immunosuppressive agents such as ACE inhibitors. Optimal combinations of these agents with least toxicity remain to be determined. The aims of this systematic review are to assess the benefits and harms of interventions used to treat idiopathic steroid resistant nephrotic syndrome (SRNS) in children.

OBJECTIVES

We aimed to evaluate the benefits and harms of all interventions for children with SRNS.

SEARCH STRATEGY

Published and unpublished randomised controlled trials (RCTs) were identified from the Cochrane Controlled Trials Register, MEDLINE, EMBASE, reference lists of articles and abstracts from conference proceedings.

SELECTION CRITERIA

RCTs and quasi-RCTs were included if they compared different immunosuppressive agents or non-immunosuppressive agents with placebo, prednisone or other agent given orally or parenterally in children aged 3 months to 18 years with SRNS.

DATA COLLECTION AND ANALYSIS

Two reviewers independently searched the literature, determined trial eligibility, assessed quality, extracted data and entered it in RevMan. For dichotomous outcomes, results were expressed as relative risk (RR) and 95% confidence intervals (CI). Data were pooled using the random effects model.

MAIN RESULTS

Nine RCTs involving 225 children were included. Cyclosporin when compared with placebo or no treatment significantly increased the number of children who achieved complete remission (three trials, 49 children: RR for persistent nephrotic syndrome 0.64, 95% CI, 0.47 to 0.88). There was no significant difference in the number of children who achieved complete remission between oral cyclophosphamide with prednisone and prednisone alone (two trials, 91 children: RR 1.01, 95% CI 0.74 to 1.36), between intravenous cyclophosphamide and oral cyclophosphamide (one study, 11 children: RR 0.09, 95% CI 0.01 to 1.39) and between azathioprine with prednisone and prednisone alone (one trial 31 children: RR 1.01, 95% CI 0.77 to 1.32). No RCTs were identified comparing combination regimens comprising high dose steroids, alkylating agents or cyclosporin with single agents, placebo or no treatment.

REVIEWERS' CONCLUSIONS

Further adequately powered and well designed RCTs are needed to confirm the efficacy of cyclosporin and to evaluate other regimens for idiopathic SRNS including high dose steroids with alkylating agents or cyclosporin.

The management of idiopathic nephrotic syndrome in children

Childhood nephrotic syndrome is a rare condition with an incidence of 1-2 per 100000 children aged below 16 years. Untreated idiopathic nephrotic syndrome (INS) is associated with increased risks of life-threatening infection, thromboembolism, lipid abnormalities, and malnutrition. The aim of the management of INS in children is to induce and maintain complete remission with resolution of proteinuria and edema without serious adverse effects of therapy. The majority of children have corticosteroid sensitive idiopathic nephrotic syndrome (CSINS), and in these children, corticosteroid therapy is the mainstay of therapy to induce remission. Data from a meta-analysis of randomized controlled trials (RCTs) indicate that prolonged courses of corticosteroids (up to 7 months) given in the first episode of CSINS reduce the risk of relapse. Nevertheless, many children relapse, and are at risk of corticosteroid toxicity if frequent courses of corticosteroids are required. Data from RCTs supports the use of alkylating agents (cyclophosphamide, chlorambucil), cyclosporine, and levamisole in these children to achieve prolonged periods of remission. The specific management of corticosteroid-resistant idiopathic nephrotic syndrome (CRINS) is more difficult since few therapies are consistently effective, and data from RCTs are limited. In such children, cyclosporine, alkylating agents, and high dose intravenous methylprednisone may be used. In addition to specific therapies for INS, supportive therapies are commonly used to control edema (loop diuretics, aldosterone antagonists, albumin infusions, angiotensin-converting enzyme inhibitors), reduce the risk of infection (antibacterials, pneumococcal vaccination) and thromboembolism (aspirin [acetylsalicylic acid]), and to control hyperlipidemia (HMG-CoA reductase inhibitors), especially in children with CRINS.

Parent-requested treatment

The decision about EPO was referred to and made by the Drug Committee, a committee of physicians, nurses and pharmacists. This committee has perforce to make decisions about drugs and vaccines, decisions which sometimes have a significant ethical component due to concerns about cost, safety and efficacy. Our hospital is considering developing a Clinical Ethics Advisory Committee, to assist with difficult ethical decisions such as this one. Should such a committee be asked to make acute ethical judgements on patient management? Larcher describes his ideal Hospital Ethics Committee as nonprescriptive, and suggests a more appropriate role is retrospective analysis and reflective discussion of clinical ethical problems. Such discussion may help with future rather than current management issues, and can help support clinicians in their decisions and hospital staff in their management of patients.

Non-corticosteroid treatment for nephrotic syndrome in children

BACKGROUND

Eighty to ninety per cent children with steroid sensitive nephrotic syndrome (SSNS) have one or more relapses. About half of these children relapse frequently and are at risk of the adverse effects of corticosteroids. Non-corticosteroid immunosuppressive agents are used to prolong periods of remission in children, who relapse frequently. However these non-corticosteroid agents also have significant potential adverse effects. Currently there is no consensus as to the most appropriate second line agent in children who are steroid sensitive, but who continue to relapse. In this systematic review of randomised controlled trials (RCTs), the benefits and harms of these immunosuppressive agents are evaluated.

OBJECTIVES

To evaluate the benefits and harms of non-corticosteroid immunosuppressive agents in relapsing SSNS in children.

SEARCH STRATEGY

Published and unpublished randomised controlled trials were identified from the Cochrane Controlled Trials Register, MEDLINE, EMBASE, reference lists of articles, abstracts from proceedings and contact with known investigators in the area.

SELECTION CRITERIA

Randomised or quasi-randomised trials were included if they were carried out in children (aged three months to 18 years) with relapsing SSNS, if they compared non-corticosteroid agents with placebo, prednisone or no treatment, different doses and/ or durations of the same non-corticosteroid agent, different non-corticosteroid agents and if they had outcome data at six months or more.

DATA COLLECTION AND ANALYSIS

Two reviewers independently reviewed all eligible studies for inclusion, assessed study quality and extracted data. The principle outcome measure was the number of children with and without relapse after six and 12 to 24 months. Secondary outcomes sought were the mean time to next relapse, the mean number of relapses per year and adverse events. A random effects model was used to estimate summary effect measures after testing for heterogeneity. Examination of possible between-study differences due to study quality, different interventions and different populations was attempted by subgroup analysis.

MAIN RESULTS

Eighteen trials involving 828 children were identified. Cyclophosphamide (three trials; relative risk (RR) 0.44; 95% confidence intervals (95% CI) 0.26 to 0.73) and chlorambucil (two trials; RR 0.13; 95% CI 0.03 to 0.57) significantly reduced the relapse risk at six to twelve months compared with prednisone alone. In the single chlorambucil versus cyclophosphamide trial, there was no observed difference in relapse risk at two years (RR 1.31; 95% CI 0.80 to 2.13). Cyclosporin was as effective as cyclophosphamide (one trial, RR 1.07; 95% CI 0.48 to 2.35) and chlorambucil (one trial, RR 0.82; 95% CI 0.44 to 1.53) but the effect was not sustained when cyclosporin was ceased. During treatment levamisole (three trials, RR 0.60; 95% CI 0.45 to 0.79) was more effective than steroids alone but the effect was not sustained. Mizoribine (one trial) and azathioprine (two trials) were no more effective than placebo or prednisone alone in maintaining remission.

REVIEWER'S CONCLUSIONS

Eight weeks courses of cyclophosphamide or chorambucil and prolonged courses of cyclosporin and levamisole reduce the risk of relapse in children with relapsing SSNS compared with corticosteroids alone. Clinically important differences in efficacy among these agents are possible and further comparative trials are still needed. Meanwhile choice between these agents depends on physician and patient preferences related to therapy duration and the type and frequency of complications.

The hindlimb in walking horses: 1. Kinematics and ground reaction forces

The objective was to study associations between kinematics and ground reaction forces in the hindlimb of walking horses. Video (60 Hz) and force (2000 Hz) data were gathered for 8 strides from each of 5 sound horses during the walk. Sagittal plane kinematics were measured concurrently with the vertical and longitudinal ground reaction forces. The hindlimb showed rapid loading and braking in the initial 10% stride. The stifle, tarsal and coffin joints flexed and the fetlock joint extended during this period of rapid loading. The vertical ground reaction force showed 2 peaks separated by a dip; this pattern was similar to the fetlock joint angle-time graph. Peaks in the longitudinal ground reaction force did not appear to correspond with kinematic events. Total braking impulse was equal to total propulsive impulse over the entire stride. Flexion and extension of the hip were responsible for protraction and retraction of the entire limb. Maximal protraction occurred shortly before the end of swing and maximal retraction occurred during breakover. During the middle part of stance the tarsal joint extended slowly, while the stifle began to flex when the limb was retracted beyond the midstance position at 28% stride. Flexion cycles of the stifle and tarsal joints were well coordinated during the swing phase to raise the distal limb as it was protracted. The results demonstrate a relationship between limb kinematics and vertical limb loading in the hindlimbs of sound horses. Future studies will elucidate the alterations in response to lameness.

The hindlimb in walking horses: 2. Net joint moments and joint powers

The objective of the study was to describe net joint moments and joint powers in the equine hindlimb during walking. The subjects were 5 sound horses. Kinematic and force data were collected synchronously and combined with morphometric information to determine net joint moments at each hindlimb joint throughout stance and swing. The results showed that the net joint moment was on the caudal/plantar side of all hindlimb joints at the start of stance when the limb was being actively retracted. It moved to the cranial/dorsal side around 24% stride at the hip and stifle and in terminal stance at the more distal joints. It remained on the cranial/dorsal side of all joints during the first half of swing to provide active limb protraction, then moved to the caudal/plantar aspect to reverse the direction of limb motion prior to ground contact. The hip joint was the main source of energy generation throughout the stride. It was assisted by the tarsal joint in both stance and swing phases and by the fetlock joint during the stance phase. The coffin joint acted as an energy damper during stance, whereas the stifle joint absorbed almost equal amounts of energy in the stance and swing phases. The coffin and fetlock joints absorbed energy as the limb was protracted and retracted during the swing phase, suggesting that their movements were driven by inertial forces. Future studies will apply these findings to detect changes in the energy profiles due to specific soft tissue injuries.

The forelimb in walking horses: 1. Kinematics and ground reaction forces

Video (60 Hz) and force (2000 Hz) data were collected from 5 sound horses during walking. Forelimb data were analysed for 8 strides (4 left, 4 right) per horse to determine sagittal plane kinematics and ground reaction forces (GRFs). The results suggested that brachial rotation was responsible for protraction and retraction of the limb as a whole, while rotations of the scapula and antebrachium elevated the distal limb during breakover and early swing then lowered it in preparation for ground contact. The coffin joint was flexed maximally at the time of peak longitudinal braking force, which occurred during breakover of the contralateral forelimb. The metacarpus was vertical at 28% stride. This was considerably earlier than the change from a braking to a propulsive longitudinal force (34% stride), which coincided with maximal extension of the fetlock joint. The longitudinal propulsive force peaked just after contact of the contralateral forelimb. During the swing phase the joints distal to the shoulder showed a single flexion cycle that peaked at 76% stride at the carpus, 81% stride at the fetlock and 84% stride at the elbow and coffin joints. The coffin and shoulder joints began to extend in the terminal swing phase and continued to extend through ground contact and early stance. The results provide normative data that will be applied in detecting changes in kinematics and ground reaction forces that are associated with specific lamenesses.

The forelimb in walking horses: 2. Net joint moments and joint powers

The objective was to measure the net joint moments and joint powers for the joints of the equine forelimb during the walk. Videographic and force data were combined with morphometric information using an inverse dynamics method. During stance phase the predominant joint moment was on the palmar aspect of all forelimb joints except the shoulder, where the peak moment was considerably higher than at any other joint. The entire forelimb showed net energy absorption in both stance and swing phases. The elbow was the only joint that showed net generation of energy, which was used to maintain the limb in extension in early stance as the horse's body vaults over the limb and to drive protraction and retraction of the limb during swing. The carpus aligned the limb into a supportive strut, but did not play an important role in energy absorption or generation. A small burst of positive work on the flexor aspect at the start of breakover indicated that the carpus played an active role in initiating breakover during walking. The fetlock functioned elastically to store and release strain energy during stance. The coffin joint acted as an energy damper during most of stance with a small burst of energy generation on the flexor aspect as the joint flexed during breakover. The magnitude of the peak joint power during swing decreased in a proximal to distal sequence. It is concluded that the elbow joint is the main site of energy generation. The shoulder and coffin joints act as energy dampers during stance. The distal joints had very low joint powers and appeared to be driven by inertial forces during the swing phase. This information will be applied to describe how horses compensate for different lamenesses in terms of redistributing the functions of energy generation and absorption between joints.

Increased surface expression of the membrane glycoprotein IIb/IIIa complex induced by platelet activation. Relationship to the binding of fibrinogen and platelet aggregation

Platelet activation altered the binding of three monoclonal antibodies (monovalent Fab' fragment) directed against the glycoprotein (GP) IIb/IIIa complex. An increased binding of two- to threefold occurred after stimulation with thrombin or phorbol myristate acetate (PMA), with slight but significant increase in the dissociation constants (Kd) of two antibodies (LJ-CP8 and LJ-P9). In contrast, no statistically significant changes were observed with ADP-stimulated platelets. The increased binding of LJ-CP3, but not of the other two antibodies, to activated platelets decreased by 30% to 40% in the presence of EDTA at 22 to 25 degrees C. Platelets stimulated by thrombin or PMA bound more fibrinogen than did those stimulated by ADP, and significant differences in the extent but not in the affinity of fibrinogen binding were observed with various platelet agonists. When the pool of GP IIb/IIIa molecules exposed on the surface of unstimulated platelets was reacted with the monoclonal antibody LJ-CP3 to block ADP-induced fibrinogen binding and platelet aggregation, stimulation with thrombin or PMA still induced substantial binding of antibody and fibrinogen, and aggregation ensued. Therefore, platelets exposed to "strong" agonists exhibit an increased number of surface-oriented epitopes associated with GP IIb/IIIa. The GP IIb/IIIa molecules bearing these newly exposed epitopes are functional in that they can bind fibrinogen and mediate platelet aggregation.

Independent modulation of von Willebrand factor and fibrinogen binding to the platelet membrane glycoprotein IIb/IIIa complex as demonstrated by monoclonal antibody

In this study we have used two new monoclonal antibodies, designated LJP5 and LJP9, as well as a previously described one, AP2, all specific for the platelet membrane glycoprotein (GP)IIb/IIIa complex. None of them reacted with dissociated GPIIb or GPIIIa. The monovalent Fab fragment of both LJP5 and LJP9 bound to unstimulated platelets in a saturable manner, but binding was markedly decreased after platelets had been incubated at 37 degrees C in the absence of added extracellular calcium. The binding of LJP9 was not affected by AP2, but was blocked by excess LJP5. On the contrary, the binding of LJP5 was blocked in the presence of both AP2 and LJP9. Thus, these antibodies bound to distinct epitopes of GPIIb/IIIa. At saturation, the binding to unstimulated platelets was between 2.41 and 10.9 X 10(4) molecules/platelet for LJP5 and between 3.47 and 9.1 X 10(4) molecules/platelet for LJP9 (range of 11 and 10 experiments, respectively). Binding increased up to 50% after thrombin stimulation. The estimated association constant, Ka, was 2.7 X 10(7) M-1 for LJP5 and 3.85 X 10(7) M-1 for LJP9. Both LJP5 and LJP9 partially inhibited the association of 45Ca2+ with the surface of unstimulated platelets. Moreover, both antibodies blocked the binding of von Willebrand factor (vWF) to stimulated platelets, whereas only LJP9, but not LJP5, blocked fibrinogen binding. LJP9 was also a potent inhibitor of platelet aggregation, whereas LJP5 was without effect in this regard. The results of the present study demonstrate that independent modulation of vWF and fibrinogen binding to stimulated platelets can be attained with monoclonal antibodies directed against distinct epitopes of GPIIb/IIIa.