Functional gait analysis of trans-femoral amputees using two different single-axis prosthetic knees with hydraulic swing-phase control: Kinematic and kinetic comparison of two prosthetic knees.

This paper reports a comparison of the gait patterns of trans-femoral amputees using a single-axis prosthetic knee that coordinates ankle and knee flexions (Proteor's Hydracadence system) with the gait patterns of patients using other knee joints without a knee-ankle link and the gait patterns of individuals with normal gait. The two patient groups were composed of 11 male trans-femoral amputees: six patients had the Hydracadence joint (Group 1) and five patients had other prosthetic knees (Group 2). The reference group was made up of 23 normal volunteers (Group 3). In this work, trunk, hip, knee, and ankle 3-D motion was assessed using the VICON system. Kinetic data were collected by two AMTI force plates, and the knee moment was calculated via the 3-D equilibrium equations. An original questionnaire was used to assess the participants' activity level and clinical background. The results reveal that, during stance, all knee types guaranteed security. After heel strike, the plantar flexion of the ankle enabled by the Hydracadence prosthesis seems to increase stability. During swing phase, hip and knee sagittal motion was nearly the same in both Group 1 and Group 2. By contrast, hallux and sole vertical positions were significantly higher in Group 1 than in Group 2; thus, it seems the link between the ankle joint and the knee joint makes foot clearance easier. No alteration of the lateral bending of the trunk was observed. The protocol proposed in this paper allows a functional comparison between prosthetic components by combining clinical data with objective 3-D kinematic and kinetic information. It might help to determine which prosthetic knees are best for a specific patient.

A functional evaluation of prosthetic foot kinematics during lower-limb amputee gait.

This paper reports on a functional evaluation of prosthetic feet based on gait analysis. The aim is to analyse prosthetic feet behaviour under loads applied during gait in order to quantify user benefits for each foot. Ten traumatic amputees (six trans-tibial and four trans-femoral) were tested using their own prosthetic foot. An original protocol is presented to calculate the forefoot kinematics together with the overall body kinematics and ground reaction forces during gait. In this work, sagittal motion of the prosthetic ankle and the forefoot, time-distance parameters and ground reaction forces were examined. It is shown that an analysis of not only trans-tibial but also trans-femoral amputees provides an insight in the performance of prosthetic feet. Symmetry and prosthetic propulsive force were proved to be mainly dependant on amputation level. In contrast, the flexion of the prosthetic forefoot and several time-distance parameters are highly influenced by foot design. Correlations show influential of foot and ankle kinematics on other parameters. These results suggest that prosthetic foot efficiency depends simultaneously on foot design and gait style. The evaluation, proposed in this article, associated to clinical examination should help to achieve the best prosthetic foot match to a patient.

No effect of calcitriol on insulin-mediated glucose uptake in healthy subjects.

Administration of active vitamin D (calcitriol) improves insulin sensitivity in uraemic patients. These patients have subnormal plasma calcitriol concentrations in parallel with increased intact parathyroid hormone (PTH) concentrations. It is therefore unclear whether the improvement in insulin sensitivity results from a direct effect of calcitriol or from amelioration of secondary hyperparathyroidism. So far, no evidence has been presented that insulin sensitivity is specifically affected by calcitriol in healthy subjects. We investigated the effect of (supra)therapeutic doses of calcitriol on insulin sensitivity in healthy volunteers. In a double-blind parallel group design, 18 healthy male subjects received in random order either placebo or 1.5 micrograms of calcitriol per day by mouth for 7 days. Insulin-mediated glucose uptake, i.e. insulin sensitivity, was assessed using the euglycaemic clamp technique. Mean glucose disposal rate, i.e. M-value, was not significantly affected by placebo or calcitriol treatment (placebo: 7.1 +/- 1.3 mg kg-1 min-1 before and 7.2 +/- 1.5 mg kg-1 min-1 after treatment; calcitriol 7.0 +/- 1.4 mg kg-1 min-1 and 7.2 +/- 1.4 mg kg-1 min-1). There were no significant changes in mean plasma glucose, insulin, phosphate, bicarbonate and ionized calcium concentrations after administration of placebo or calcitriol. Furthermore, platelet intracellular calcium concentration (assessed by fluorescence spectroscopy) and mean arterial blood pressure (24 h ambulatory measurement) did not change with placebo and calcitriol treatment. On the other hand, mean intact PTH concentration decreased significantly (P < 0.01) with calcitriol treatment, but not with placebo. In addition, mean 24 h urinary calcium excretion increased significantly (P < 0.05) with calcitriol administration but was unchanged with placebo. Administration of (supra)physiological doses of calcitriol has no effect on insulin sensitivity in healthy subjects, despite a significant decrease in PTH concentrations. These observations are compatible with the notion that the effect of calcitriol on insulin sensitivity is present only in uraemic calcitriol-depleted patients.

Subacute infusion of physiological doses of parathyroid hormone raises blood pressure in humans.

BACKGROUND: Acute administration of parathyroid hormone (PTH) causes vasodilation and blood pressure decrease in experimental animals. This effect contrasts with the putative role of secondary hyperparathyroidism in the pathogenesis of hypertension of patients with renal failure. Uraemia is characterized by insulin resistance and hyperinsulinaemia. We therefore investigated whether subacute administration of physiological doses of human 1,34-PTH affects blood pressure under conditions of controlled insulin levels (euglycaemic clamp technique) in humans. METHODS: In a double-blind cross-over design 10 healthy male subjects received, on two occasions, in random order, for 2 h, either a sham infusion or an infusion of 200 units of 1,34-PTH. RESULTS: Mean ionized calcium concentration increased significantly (P < 0.01) within the normal range during euglycaemic hyperinsulinaemia, both with sham infusion (from 1.25 +/- 0.04 to 1.29 +/- 0.02 mmol/l) and with infusion of 1,34-PTH, but the increase was more marked with 1,34-PTH administration (from 1.26 +/- 0.05 to 1.33 +/- 0.07). In addition, mean platelet intracellular calcium concentration (by fluorescence spectroscopy) was unchanged with sham infusion (49.9 +/- 4.1 versus 50.3 +/- 5.0 nmol), but increased significantly (P < 0.05; paired t-test) after 1,34-PTH infusion (from 49.8 +/- 5.0 to 52.8 +/- 5.8). The infusion of 1,34-PTH resulted in a significant (P < 0.01) increase in mean MAP (from 84 +/- 5 to 88 +/- 5 mmHg) as compared with sham infusion (85 +/- 4 versus 86 +/- 4). The intra-individual changes in intracellular calcium concentration (delta[Ca2+]i) were significantly correlated to the changes in mean MAP (delta MAP) (r = 0.87, P < 0.001). In contrast to blood pressure, insulin sensitivity was not affected by 1,34-PTH infusion (M-value: 7.2 +/- 1.6 mg/kg per min) as compared with sham infusion (7.3 +/- 1.4). CONCLUSION: Subacute administration of physiological doses of parathyroid hormone under hyperinsulinaemic conditions significantly affects intracellular calcium and blood pressure in healthy subjects, but does not affect the action of insulin.

Changes in plasma phosphate levels influence insulin sensitivity under euglycemic conditions.

The euglycemic clamp technique is a useful tool to evaluate insulin-mediated glucose uptake. The plasma phosphate concentration decreases during euglycemic clamp studies. Because insulin-dependent glucose uptake is closely related to phosphate uptake, we investigated whether modulation of plasma phosphate levels in the range observed during clamp studies influences insulin sensitivity. We studied 11 healthy (phosphate-replete) male volunteers (mean age, 27.5 +/- 1.8 yr;, mean body mass index, 23.9 +/- 1.6 kg/m2) in a double blind placebo-controlled cross-over study. The volunteers received in random order on two occasions either an infusion of sodium chloride (sham infusion) or an infusion of sodium phosphate. Insulin sensitivity was assessed under euglycemic conditions (clamp technique). The mean plasma phosphate concentration decreased with sham infusion from 1.09 +/- 0.17 to 0.64 +/- 0.13 mmol/L, whereas it increased with phosphate infusion from 1.06 +/- 0.19 to 1.32 +/- 0.13 mmol/L. In all volunteers except one the glucose disposal rate (M-value) was higher after phosphate infusion (mean M-value, 10.4 +/- 1.5 mg/kg.min) than that after sham infusion (mean M-value, 9.4 +/- 1.5 mg/kg.min; P < 0.01, by Wilcoxon's test for paired samples). There were no significant differences in mean plasma glucose, sodium, insulin, or arterialized standard bicarbonate levels with the two infusion protocols. Mean plasma calcium, albumin-corrected calcium, and potassium levels, however, were all significantly (P < 0.05) lower after phosphate infusion than after sham infusion. The mean PTH level decreased with sham infusion from 28 +/- 9 to 20 +/- 6 ng/L, whereas it increased with phosphate infusion from 26 +/- 9 to 36 +/- 8 ng/L, whereas it increased with phosphate infusion from 26 +/- 9 to 36 +/- 8 ng/L. The difference between the two infusion protocols was statistically significant (P < 0.01). The data presented illustrate that plasma phosphate (and calcium) levels may be confounders that should be at least monitored, and possibly controlled for, when performing euglycemic clamp studies.

The effect of dietary salt on insulin sensitivity.

Acute reduction of salt intake causes an increase in serum lipid and insulin levels in healthy volunteers and patients with essential hypertension, suggesting induction of insulin resistance by salt restriction. Direct measurements of insulin sensitivity using the euglycaemic clamp showed no significant change after 7 days of salt restriction. Our previous study showed a time dependent course of dyslipidaemia after institution of a low salt diet. We therefore assessed insulin sensitivity (M-value) under euglycaemic conditions (clamp technique) at discrete time points using a parallel group design. Two groups of healthy males were examined on high (200 mmol d-1) and low (20 mmol d-1) salt intake. One group (n = 7, 25 +/- 3 years, BMI 22.4 +/- 2.1 kg m-2) received high and low salt diet in random order each for 7 days. The other group (n = 7, 26 +/- 3 years, 22.1 +/- 1.9 kg m-2) received the respective diet in random order for 3 days. A significantly (P < 0.01) different mean M-value was noted in the group receiving the diets for 3 days, i.e. after low salt intake it was 7.4 +/- 1.2 mg kg-1 min-1 and after high salt intake 8.6 +/- 1.1 mg kg-1 min-1. In contrast, the mean M-value was similar after low and high salt periods in the group of individuals who had been studied after 7 days on either salt take (7.8 +/- 1.8 on low salt vs. 7.6 +/- 1.3 mg kg-1 min-1 on high salt).(ABSTRACT TRUNCATED AT 250 WORDS)