In vivo optical spectroscopy monitoring in a new model of muscular compartment syndrome.

BACKGROUND: Muscular compartment syndrome (MCS) is a rare but serious postoperative complication. In vivo optical spectroscopy (INVOS) monitors continuously and non-invasively regional oxygen saturation (rSO(2)), and could predict the development of MCS. METHODS: In 10 healthy volunteers, we inflated a tourniquet to the mean arterial pressure to produce slight venous congestion and arterial hypoperfusion. Comparisons were made between the relative reduction in rSO(2) with baseline (deltaINVOS) and the time to observe motor nerve block (with non-invasive electromyography). Neurological symptoms, pain, and invasive intracompartmental pressure (ICP) were assessed. RESULTS: In the eight volunteers completing the protocol, we observed a profound motor nerve conduction block, immediately reversible. Baseline values were: [mean (sd)] INVOS: 73.3 (8.9)% and ICP: 16.9 (8.6) mm Hg. At the time of the block, values were: INVOS: 46.4 (10.9)%, deltaINVOS: 28.7 (10.6)%, and ICP: 70.0 (5.5) mm Hg. The time to reach the block was 33.0 (10.9) min, and to a deltaINVOS>10%: 27.4 (10.4) min. Receiver-operating characteristic curves demonstrated a similar accuracy of ICP and INVOS to predict the occurrence of the block. Twenty minutes with a deltaINVOS>10% or ICP>30 mm Hg were associated with a sensitivity and a specificity of 95% and 70%; or 91% and 65%, respectively. CONCLUSIONS: We have developed a model of acute immediately reversible MCS. Monitoring using the INVOS technology is as accurate as measurement of ICP, and could be a useful tool to prevent development of intraoperative MCS.

The reasons why stroke patients expend so much energy to walk slowly.

BACKGROUND: The energy consumed per covered distance (C) is increased in hemiparetic stroke adults during walking. OBJECTIVE: To ascertain if increased C in stroke patients is a result of increased mechanical work, of decreased efficiency of work production by muscles or of slow walking speed. METHODS: C and mechanical work were computed in 20 patients walking on a force measuring treadmill at speeds ranging from 1 km h(-1) to their own maximum speed (WS(MAX)). Works done by healthy and pathological limbs were computed separately. RESULTS: For hemiparetic patients, C was around 1.7 times greater than normal. When these patients had a slower WS(MAX), they had greater C and mechanical work (r=-0.44 and -0.57, respectively). The increased C was related to the external work performed to lift the center of body mass when the healthy limb was supporting the body weight (r=0.77). CONCLUSIONS: The increase of C in stroke patients is more pronounced when WS(MAX) is slow. Moreover, this increase is related to increased mechanical work done by muscles and is not related to slow walking speed or decreased efficiency. As in healthy subjects, C and external work presented optimum speeds, indicating a preserved pendular mechanism of walking.

Towards a "gold-standard" approach to address the presence of long-range auto-correlation in physiological time series.

Series of motor outputs generated by cyclic movements are typically complex, suggesting that the correlation function of the time series spans over a large number of consecutive samples. Famous examples include inter-stride intervals, heartbeat variability, spontaneous neural firing patterns or motor synchronization with external pacing. Long-range correlations are potentially important for fundamental research, as the neural and biomechanical mechanisms generating these correlations remain unknown, and for clinical applications, given that the loss of long-range correlation may be a marker of disease. However, no systematic approach or robust analysis methods have yet been used to support the study of correlation functions in physiological series. This study investigates four selected methods (the Hurst exponent, the power spectral density analysis, the rate of moment convergence and the multiscale entropy methods). We present the result of each analysis performed on artificial computer-generated series in which the auto-correlation function is known, and then on time series extracted from gait and upper limb rhythmic movements. Our results suggest that combined analysis using the Hurst exponent and the power spectral density is suitable for rather short series (512 points). The rate of moment convergence directly supports the power spectral density analysis, and the multiscale entropy further confirms the presence of long-range correlation, although this method seems more appropriate for longer series. The proposed methodology increases the level of confidence in the hypothesis that physiological series are long-memory processes, which is of prime importance for future fundamental and clinical research.

[Multiple diabetic muscular infarctions after liver and kidney transplantation: a case report]. / Multiples infarctus musculaires diabétiques après transplantation hépatique et rénale.

INTRODUCTION: Several neuromuscular diseases may complicate diabetes mellitus and transplantation, including chronic sensorimotor length dependent polyneuropathy. OBJECTIVE: Description of muscular infarction, a rare complication of diabetes mellitus, which occurred after liver and kidney transplantation. CASE REPORT: A 57-year-old patient presented with long-term diabetes mellitus and multiple complications. End-stage renal and hepatic disease led to kidney and liver transplantation. Twenty-seven days after transplantation, swelling and induration appeared in the left shoulder and forearm. Forty-three days after transplantation, the same symptoms appeared in both lower limbs. Markedly reduced range of motion led to severe disability. Bone scans showed multiple spots following muscle anatomy. Computed tomography gave negative results. Magnetic resonance imaging (MRI) confirmed muscular infarction by a high T1 signal (muscular necrosis) and soft-tissue infiltration. DISCUSSION AND CONCLUSION: Muscular infarction is a rare and unknown complication of diabetes mellitus. It is characterised by sudden painful muscular induration and swelling affecting one muscle at a time with recurrence. Our patient presented with simultaneous multiple muscular infarctions in 3 limbs. Diagnosis was based on clinical investigation and MRI. The treatment is conservative and the condition generally resolved by itself. However, the long-term prognosis of muscular infarction is not good because of the cardiovascular-associated complications of diabetes mellitus.

Efficiency of work production by spastic muscles.

The present study compared the muscular efficiency in spastic and healthy lower limbs producing the same mechanical work. Sixteen chronic post-stroke hemiparetic and spastic patients and 14 age-matched healthy subjects were submitted to a submaximal stepwise exercise testing on a bicycle ergometer, pedalling with only one lower limb. Net energetic expenditure was computed from oxygen consumption above resting values. Electrical activity of antagonistic muscles in the thigh and in the shank was recorded and co-contraction was defined as the percentage of the pedalling cycle when antagonistic muscles were activated simultaneously. The efficiency was calculated as the ratio between the mechanical work done on the ergometer and the net energetic expenditure. Spasticity was quantitatively evaluated by measuring passive ankle plantar flexor muscle stiffness. The working capacity of the patients' paretic lower limb was very low (<40W). The energy expenditure increased linearly as a function of work intensity, without statistical difference between the patients paretic lower limb (PPL), the patients healthy lower limb (PHL) and the healthy subjects lower limb (HSL). Shank co-contraction was 2.9 times greater in PPL (p<0.05) and 2.3 times greater in PHL (p<0.05) than in HSL. Thigh co-contraction was also 1.8 times greater in PPL than in HSL (p<0.05). The ankle plantar flexor muscle stiffness was statistically greater in PPL than in PHL and HSL (p<0.05). The efficiency was not statistically different between the three groups (p=0.155). In conclusion, the efficiency of work production by paretic and spastic lower limb muscles was normal ( congruent with 20%) despite significant neurological impairments.

Botulinum toxin and short-term electrical stimulation in the treatment of equinus in cerebral palsy.

Intramuscular botulinum toxin type A (BT-A) has been shown to reduce spasticity and to improve gait in children with cerebral palsy. To determine whether the efficacy of BT-A may be enhanced by electrical stimulation, as suggested in focal dystonia or in adult spastic patients, 12 children with dynamic foot equinus deformity were randomly assigned to two groups in a blinded, clinically controlled trial. Intramuscular BT-A into calf muscles was followed by adjuvant electrical stimulation in Group A (n = 6) but not in Group B (n = 6). Clinical assessment and instrumented gait analysis were performed before and 1, 3, and 6 months after treatment. The combined treatment of BT-A and electrical stimulation was not superior to BT-A alone. For all patients, improvement of the clinical and gait variables occurred at 1 and 3 months after BT-A injection.

Energy cost of riding bicycles with shock absorption systems on a flat surface.

Bike shock absorption systems reduce the energy variation induced by terrain irregularities, leading to a greater comfort. However, they may also induce an increase in energy expenditure for the rider. More specifically, cross-country racers claim that rear shock absorption systems generate significant energy loss. The energy losses caused by such systems may be divided in terrain-induced or rider-induced. This study aims at evaluating the rider-induced energy loss of modern suspended bicycles riding on a flat surface. Twelve experienced competitive racers underwent three multistage gradational tests (50 to 250 W) on a cross-country bicycle mounted on an electromagnetically braked cycle ergometer. Three different tests were performed on a fully suspended bike, front suspended and non-suspended bicycle, respectively. The suspension mode has no significant effect on VO2. The relative difference of VO2 between the front-suspended or full-suspended bike and the rigid bike reaches a non significant maximum of only 3%. The claims of many competitors who still prefer front shock absorption systems could be related to a possible significant energy loss that could be present at powers superior to 250 W or when they stand on the pedals. It could also be generated by terrain-induced energy loss.

Increase of physical activity level after successful renal transplantation: a 5 year follow-up study.

BACKGROUND: Physical activity (PA) level of end-stage renal disease (ESRD) patients after renal transplantation (TP) is a largely unexplored field, although it is an important component of quality of life. METHODS: Using the Baecke self-administered and the Five-City Project 7-day PA recall questionnaires, PA level was estimated in 32 consecutive ESRD patients (12 males, 20 females; mean age 45.9+/-13.1 years; mean dialysis duration 23.5+/-21.8 months) admitted for renal TP and to whom no exercise programme of any kind was proposed. PA were recorded 1, 3, 6, 12 and 60 months after TP. RESULTS: Immediate pre-TP PA level of renal transplant candidates was between 18 and 35% less than that of age-matched healthy subjects (P < 0.05), depending on gender and questionnaire. After an immediate decrease in PA level 1 month post-TP, mean PA level increased and reached a plateau 1 year after TP. This gain in PA capacity reached 30%, as compared with pre-TP values (P = 0.06 to P < 0.01). During the fifth year after TP, the mean level of PA was unchanged. A more qualitative analysis, allowed by the sub-score comparisons, showed that although the occupational status of the patients remained the same, they participated significantly more in moderate and even high intensity PA (leisure, sports, household chores) after TP. CONCLUSIONS: Most renal graft recipients are spontaneously more active after TP, an observation consistent with a better quality of life. Therefore, they should be advised precisely about how to resume more strenuous activities such as sports in order to avoid cardiac or musculoskeletal disorders in relation to their weakened pre-TP condition.

[Objective measures of muscle stiffness in the ankle. Evaluation of the effect of intrathecal injection of baclofen in spastic patients]. / Mesure objective de la raideur musculaire des fléchisseurs de la cheville. Evaluation de l'effet de l'injection intra-thécale de baclofène chez un patient spastique.

This paper presents the objective and quantitative measurement of muscle stiffness described by Rack and Lehmann. This method allows analysis of the pathophysiological mechanism of spasticity and assessment of anti-spastic treatment. This is illustrated by a case report, showing the objective effect of intrathecally administered baclofen in a spastic patient.

Mechanics and energetics of human locomotion on sand.

Moving about in nature often involves walking or running on a soft yielding substratum such as sand, which has a profound effect on the mechanics and energetics of locomotion. Force platform and cinematographic analyses were used to determine the mechanical work performed by human subjects during walking and running on sand and on a hard surface. Oxygen consumption was used to determine the energetic cost of walking and running under the same conditions. Walking on sand requires 1.6-2.5 times more mechanical work than does walking on a hard surface at the same speed. In contrast, running on sand requires only 1.15 times more mechanical work than does running on a hard surface at the same speed. Walking on sand requires 2.1-2.7 times more energy expenditure than does walking on a hard surface at the same speed; while running on sand requires 1.6 times more energy expenditure than does running on a hard surface. The increase in energy cost is due primarily to two effects: the mechanical work done on the sand, and a decrease in the efficiency of positive work done by the muscles and tendons.

Gait analysis and motor point block in dynamic varus of the rear foot in a head injured adult.

This clinical note describes a typical case of dynamic varus deformity of the hind part of the foot in a head injured adult. Gait analysis objectified, by kinematic data, the perturbed movement of the rear foot in the frontal plane and identified, by dynamic electromyography, the overactive muscle (posterior tibialis) involved in the deformity. The diagnosis was confirmed by a motor point block of the posterior tibialis muscle with functional improvement. Kinematic data also showed improvement after the block. This case report illustrates the usefulness of gait analysis in diagnosis and management of gait disturbances in adult patients.