Muscle enhancement using closed-loop electrical stimulation: volitional versus induced torque.

In cases of partial deficiency of muscle activation capacity, force augmentation can be achieved by hybrid activation, i.e., by combining electrical stimulation (ES) with volitional activation. In this activation modality the shares of the volitional and induced torques within the overall hybrid torque are unknown. The purpose of this study was to suggest a computational approach to parcel out the volitional and stimulation induced components of joint torque generated during combined voluntary and electrical activation of the Tibialis Anterior muscle (TA). For this purpose, isometric contraction of the TA was studied on 5 healthy subjects, using an activation protocol involving ES alone, volitional activation alone and hybrid activation. Ankle torque and TA EMG were measured. A computational algorithm was developed to dissociate the volitional from the overall torque, based on EMG filtering and on pre-measured calibration curves of volitional torque versus EMG. The results indicated that for a certain hybrid torque there is a linear decaying relationship between the induced torque and the volitional torque shares. Moreover, based on a defined enhancement ratio, the results indicate that within the range of stimulation intensities, there exist regions of increased facilitation, in which the stimulation efficiency is higher under combined compared to isolated conditions.

Gait rehabilitation: a new biofeedback device for monitoring and enhancing weight-bearing over the affected lower limb.

AIM: Gait rehabilitation programs often require either partial weight-bearing (PWB) or encourage full weight-bearing (FWB) on the affected limb. Until recently, there was no objective and practical way to measure correct weight-bearing during ambulation. The present study evaluates a new in-shoe device (SmartStep, Andante Medical Devices Ltd.) for measuring the amount of weight on the affected limb and for biofeedback gait training. METHODS: The first part of the study aimed to establish the validity of the SmartStep by comparing the results obtained from this device with the results obtained from a force plate. The second part aimed to evaluate the effectiveness of the SmartStep as a biofeedback method in patients who have been referred for FWB gait rehabilitation. Analysis was based on independent samples t-test and chi squared test for evaluating statistically significant differences between the 2 gait rehabilitation modes. RESULTS: The SmartStep could repeat the same results with 0.53 kg error of mean. Statistically significant correlation was found between results obtained from the SmartStep and from the force plate (R2=0.9067 and P=0.004). The use of the SmartStep auditory biofeedback, significantly (P=0.00031) improved patients' weight-bearing over the affected limb in the experimental group (7.9 kg +/-5.28) as compared to the control group (0.7+/-2.41 kg). CONCLUSIONS: The SmartStep proved to be very reliable since it generated significant repeatable results which correlated significantly with those obtained from a force plate. Patients recommended for FWB gait can significantly improve body weight loading over the affected limb by the use of the SmartStep auditory biofeedback.

Acute leukemia detection rate by automated blood count parameters and peripheral smear review.

INTRODUCTION: It is unclear what minimal criteria will identify all new cases of acute leukemia in adults in various settings. METHODS: To determine the adult acute leukemia detection rate of the various criteria, we recorded complete blood count (CBC) test results from consecutive patients with leukemia (130 hospitalized patients and 96 outpatients) and from consecutive patients without leukemia (34,827 hospitalized and 33,695 outpatients). RESULTS: Basic criteria for a reflex review (hemoglobin, platelets, and a five-part differential) detected 91% of new hospital leukemia patients (118 of 130) compared to 75% (72 of 96) outpatients. No cases were missed if we did reflex testing when there was either one of the basic criteria or an increased proportion of large unstained cells (LUC), but five cases were missed using the blast flag instead of the LUC. Adding the LUC to basic criteria resulted in the detection of all cases of acute leukemia. The cost of detection of one case of acute leukemia was 1029 and 425 peripheral smear reviews in hospital and outpatients, respectively. CONCLUSION: We conclude that basic criteria available on most hematology analyzers along with the LUC identify all adult patients with acute leukemia in both hospital and outpatient settings with minimal peripheral smear review rates.

Effect of ingested sodium bicarbonate on muscle force, fatigue, and recovery.

The influence of acute ingestion of NaHCO3 on fatigue and recovery of teh quadriceps femoris muscle after exercise was studied in six healthy male subjects. A bicycle ergometer was used for exercising under three loading conditions: test A, load corresponding to maximal oxygen consumption; test B, load in test A + 17%; test C, load in test B but performed 1 h after acute ingestion of NaHCO3. Functional electrical stimulation (FES) was applied to provoke isometric contraction of the quadriceps femoris. The resulting knee torque was monitored during fatigue (2-min chronic FES) and recovery (10-s FES every 10 min, for 40 min). Quadriceps torques were higher in the presence of NaHCO3 (P < 0.05): with NaHCO3 the peak, residual, and recovery (after 40 min) normalized torques were, respectively, 0.68 +/- 0.05 (SD), 0.58 +/- 0.05, and 0.73 +/- 0.05; without NaHCO3 the values were 0.45 +/- 0.04, 0.30 +/- 0.06, and 0.63 +/- 0.06. The increased torques obtained after acute ingestion of NaHCO3 indicate the possible existence of improved nonoxidative glycolysis in isometric contraction, resulting in reduced fatigue and enhanced recovery.

Reflex sympathetic dystrophy of the stump in below-knee amputees.

OBJECTIVE: To document the occurrence of reflex sympathetic dystrophy of the stump in two patients with below-knee amputation. DESIGN: A retrospective survey emphasising two clinical case reports. SETTING: Department of orthopaedic rehabilitation at a teaching rehabilitation hospital. PATIENTS: Lower limb amputees (n = 164) were accepted for prosthetic rehabilitation. Twenty-one amputees were regarded as rehabilitation failures; in two below-knee amputees intractable pain was the major problem. RESULTS: Clinical manifestations, radiological, and scintigraphic findings in the two amputees with intractable pain met the criteria for diagnosis of reflex sympathetic dystrophy. CONCLUSIONS: Reflex sympathetic dystrophy of the stump should be suspected in below-knee amputees whenever severe pain persists over a period of 3 to 4 months following amputation.

Transcutaneous FES of the paralyzed quadriceps: is knee torque affected by unintended activation of the hamstrings?

This study addresses the question whether unintended response of the knee flexors (hamstrings) accompanies transcutaneous functional electrical stimulation (FES) of the quadriceps and whether the knee torque is hereby affected. Transcutaneous FES of the right quadriceps of two paraplegic subjects was applied and measurements were made of the net torque and of the myoelectric activities of the quadriceps and hamstrings muscles of the right leg. A low correlation was obtained between the peak-to-peak amplitudes of the M-waves of the two muscles. This correlation decreased further with the development of fatigue, which indicated that the electromyography (EMG) signals from the hamstrings were not the result of cross-talk between adjacent recording sites. The force profile of each muscle was determined from a developed model incorporating EMG-based activation, muscle anthropometry as obtained from in vivo magnetic resonance imaging of the thigh, and metabolic fatigue function, based on data acquired by 31P nuclear magnetic resonance spectroscopy. A sensitivity analysis revealed that the muscle specific tension and the muscle moment arms have a major influence on the resulting muscle forces and should therefore be accurately provided. The results show that during the unfatigued phase of contraction the estimated maximal force in the hamstrings was lower than 20% of that in the quadriceps and could be considered to be practically negligible. As fatigue progressed the hamstrings-to-quadriceps force ratio increased, reaching up to 45%, and the effect of co-activation on the torque partition between the two muscles was no longer negligible.

Muscle fatigue in interrupted stimulation: Effect of partial recovery on force and EMG dynamics.

Muscle fatigue is a major problem in functional electrical stimulation (FES); the understanding of fatigue and recovery processes is thus of great interest. In interrupted stimulation, fatigue and recovery occur in sequence, and the history-dependency of the muscle's response to FES becomes significant. In this work, the force and electromyographical (EMG) fatigue characteristics of FES-activated paralysed muscles were studied, both in the initially unfatigued state (primary fatigue) and in the reactivated state, after rest periods of prescribed durations (post-recovery fatigue). Because the data were collected over weeks, longitudinal studies were also made to account for long-term training effects of the muscle. Mechanical and myoelectric profiles, the latter derived from the M-wave, were obtained from the right quadriceps of two paraplegic subjects under isometric stimulation. Force was found to correlate highly with peak-to-peak amplitude of the EMG M-wave. Training did not affect this correlation, but as the recovery duration increased, the force-EMG curves became less concave. Training was found to increase the muscle force and EMG peak-to-peak amplitude, as well as the residual force achieved, but it had no noticeable effects on the M-wave duration parameters. Both the force and EMG parameters demonstrated substantial recovery within the first 3 min of rest, and exhibited a consistent tendency to level off for higher periods of rest. After comparing this finding to those expected from previous metabolic models, it was concluded from the subjects studied and model developed that, in addition to metabolic factors, electrolytic factors may be significant in governing the dynamics of fatigue and recovery.

Knee muscle activity during ambulation of trans-tibial amputees.

Gait analysis of trans-tibial amputees brings to light asymmetries of different gait parameters between the amputated and sound legs. The present study investigated the activity of the vastus medialis and biceps femoris muscles during ambulation of trans-tibial amputees. Peak activities of the vastus medialis were reached similarly in both legs (6.06+/-4.9% and 8.84+/-3.6% of gait cycle, in the sound and amputated leg, respectively). Biceps femoris peak activities were reached at 92.43+/-6.6% of gait cycle in the sound leg, and significantly later (at 9.81+/-4.8% of gait cycle) in the amputated leg (p < 0.05). Integrated EMG activity ratios, between swing and stance periods, were similar for the vastus medialis (0.33 in the sound and 0.35 in the amputated leg). However, these ratios differed significantly for the biceps femoris since the amputated leg presented a substantial (p < 0.05) smaller ratio (0.22) compared with the sound leg (0.83). The use of prosthesis in trans-tibial amputees requires further activity of the biceps femoris during stance period to improve support of the amputated leg knee joint.

Reflex sympathetic dystrophy of both patellae following burns.

This study describes a previously undescribed cause of reflex sympathetic dystrophy involving both patellae. This syndrome developed following burns inflicted over both knees in a male industrial worker. The report highlights physical examination findings, investigation results, socioeconomic and psychological evaluation, and rehabilitation treatments involved in patients suffering from reflex sympathetic dystrophy.

Fatigue-induced changes in decline running.

OBJECTIVE: Study the relation between muscle fatigue during eccentric muscle contractions and kinematics of the legs in downhill running. DESIGN: Decline running on a treadmill was used to acquire data on shock accelerations, muscle activity and kinematics, for comparison with level running. BACKGROUND: In downhill running, local muscle fatigue is the cause of morphological muscle damage which leads to reduced attenuation of shock accelerations. METHODS: Fourteen subjects ran on a treadmill above level-running anaerobic threshold speed for 30 min, in level and -4 degrees decline running. The following were monitored: metabolic fatigue by means of respiratory parameters; muscle fatigue of the quadriceps by means of elevation in myoelectric activity; and kinematic parameters including knee and ankle angles and hip vertical excursion by means of computerized videography. Data on shock transmission reported in previous studies were also used. RESULTS: Quadriceps fatigue develops in parallel to an increasing vertical excursion of the hip in the stance phase of running, enabled by larger dorsi flexion of the ankle rather than by increased flexion of the knee. CONCLUSIONS: The decrease in shock attenuation can be attributed to quadriceps muscle fatigue in parallel to increased vertical excursion of the hips.

Shock accelerations and attenuation in downhill and level running.

OBJECTIVE: A study was conducted to investigate the possible effects of fatigue on the heel strike-initiated shock accelerations and on attenuation of these shocks along the body during eccentric muscle contractions. DESIGN: Level and decline running on a treadmill were used to acquire the experimental data on the foot strike-initiated shock accelerations. BACKGROUND: Eccentric contractions of the lower limb muscles in combination with shock generation and propagation during downhill running and muscle fatigue may diminish their ability to dissipate and attenuate loading on the system. METHODS: Fourteen young healthy males ran on a treadmill at a speed exceeding their anaerobic threshold by 5% for 30 min, as follows: (a) level running and (b) downhill running with a decline angle of -4 degrees. The foot strike-induced shock accelerations were recorded every five minutes on the tibial tuberosity and sacrum. Fatigue was monitored by means of the respiratory parameters. RESULTS: The downhill running related with eccentric muscle contractions was associated with increased shock propagation from the tibial tuberosity to the sacrum levels, even though fatigue did not develop. CONCLUSIONS: Shock propagation from the tibial tuberosity to the sacrum is augmented due to the eccentric action of the muscles, without metabolic fatigue development. RELEVANCE: Eccentric muscle contraction in downhill running reduces the musculoskeletal ability to attenuate the heel strike-induced shock waves. Knowledge about the effect of fatigue on the shock propagation between the shank and the sacrum levels may help in understanding the mechanism of stress fractures and joint damage.

Influence of prosthesis alignment on the standing balance of below-knee amputees.

The effect of alignment of the prosthesis on the standing balance of below knee amputees was investigated in this work. Alignment variations consisted of varus and valgus tilt and plantar- and dorsiflexions. The foot-ground reaction forces measured in the anteroposterior, mediolateral, and vertical directions as well as global parameters describing the total sway activity, asymmetry, and weight-bearing imbalance were used to compare the various alignment positions studied. The results indicate the presence of a common standing pattern in below-knee amputees, where activity of the foot-ground reaction forces in the anteroposterior direction is significantly higher in the contralateral limb compared with the amputated limb. It was also found that the varus and valgus alignments were the least stable of all alignments.

Biomechanical and physiological evaluation of FES-activated paraplegic patients.

Four paraplegic patients with traumatic upper motor neuron lesions at the spinal levels between D5 and D12 were activated by functional electrical stimulation (FES) and evaluated biomechanically and physiologically. After a training program aimed at strengthening the muscles of the lower legs, the patients were able to stand up, maintain the standing position, and walk for short distances while being supported. Biomechanical evaluation included weight bearing on the patients' own legs during standing as measured on a force platform and analysis of the time-distance parameters of the stride during walking as measured on a walkway. Physiological evaluation included heart rate and oxygen consumption at rest, when activated by FES in the sitting position, during standing, and during walking. The results obtained indicate that while significant standing and walking performances are achieved, the corresponding physical effort can reach relatively high levels requiring the support of anaerobic energy sources. The practical implications of these results are discussed.

Mobility of persons after traumatic lower limb amputation.

The objective of this study was to determine the influence of time span since amputation on mobility of persons experiencing traumatic lower limb amputation. A special questionnaire was sent to such persons and responses were analysed statistically. The subjects comprised 223 persons after traumatic lower limb amputation, residents of Slovenia. We discovered that 186 (74.2%) are using their prosthesis for more than 7 hours per day, 109 (52.2%) are able to walk outdoors without crutches, and 129 (57.8%) climb more than 20 stairs per day. In addition, those who are walking without crutches, walking longer distances, still cycling and driving a care are, on average, 5-10 years younger than the others. However, around one-third of persons who were young at the time of amputation face limitations of mobility later in life. A total of 76 (35.3%) are able to walk only up to 500 m out of doors, 38 (18.2%) can walk only with a pair of crutches, 62 (29.7%) need a cane or one crutch, and 37 (16.6%) cannot climb stairs. We conclude that successful fitting and usage of a prosthesis by persons after lower limb amputation promotes independent walking and mobility in everyday life. The level of independence achieved is related to time span since amputation.

The control of genu recurvatum by combining the Swedish knee-cage and an ankle-foot brace.

Genu recurvatum is a consequence of a poor control over the knee joint due to muscle weakness, impaired tonus and deficit in joint proprioception. Uncontrolled locking of the knee during ambulation causes recurrent microtrauma which leads to degenerative changes and instability. Known methods to control hyperextension of the knee during ambulation often fail. We have used the Swedish knee-cage attached to ankle-foot brace in an attempt to improve control over the knee in three patients. Gait analysis was performed to evaluate the effectiveness of this combined orthosis. Quality of gait improved, as demonstrated by a decrease in stance time asymmetry in the order of 45%; stride increased by 29% and speed of ambulation increased by 72%.

Self-injury resulting in amputation among vascular patients: a retrospective epidemiological study.

In the course of 24 months, 164 nontraumatic vascular amputees were accepted for prosthetic rehabilitation; 120 (73%) were diabetic and 44 (27%) non-diabetic. Subjects were divided into two groups, the first consisting of 114 with spontaneous foot infection or gangrene and the second of 50, of whom 44 were diabetic and six had peripheral arterial disease on its own. Sixty-five per cent of all amputees had fewer than nine years of formal education and 46% were in the low-income bracket, but no significant relationship was found between mechanism of self-injury and level of education and income. All patients in the second group were able to detail ways in which they had injured their feet. The relationship between the mechanism of self-injury and the presence of diabetes mellitus was found to be highly significant. By instructing in better self-care it may be possible to prevent or at least postpone amputation in these patients.

Trans-tibial amputee gait: time-distance parameters and EMG activity.

Gait analysis of trans-tibial (TT) amputees discloses asymmetries in gait parameters between the amputated and sound legs. The present study aimed at outlining differences between both legs with regard to kinematic parameters and activity of the muscles controlling the knees. The gait of 14 traumatic TT amputees, walking at a mean speed of 74.96 m/min, was analysed by means of an electronic walkway, video camera, and portable electromyography system. Results showed differences in kinematic parameters. Step length, step time and swing time were significantly longer, while stance time and single support time were significantly shorter on the amputated side. A significant difference was also found between knee angle in both legs at heel strike. The biceps femoris/vastus medialis ratio in the amputated leg, during the first half of stance phase, was significantly higher when compared to the same muscle ratio in the sound leg. This difference was due to the higher activity of the biceps femoris, almost four times higher than the vastus medialis in the amputated leg. The observed differences in time-distance parameters are due to stiffness of the prosthesis ankle (the SACH foot) that impedes the normal forward advance of the amputated leg during the first half of stance. The higher knee flexion at heel strike is due to the necessary socket alignment. Unlike in the sound leg, the biceps femoris in the amputated leg reaches maximal activity during the first half of stance, cocontracting with the vastus medialis, to support body weight on the amputated leg. The obtained data can serve as a future reference for evaluating the influence of new prosthetic components on the quality of TT amputee's gait.

The use of Methenamine as an antiperspirant for amputees.

The socket of a prosthesis is a tightly closed container. Sweating inside the socket is annoying and may also irritate the skin over the stump or lead to local infection such as folliculitis. The most effective method of preventing sweating is by the use of astringent agents. Formaldehyde is a very strong astringent but is not pleasant to use and may cause skin irritation and systemic reactions. Methenamine, in water or when applied to the skin, decomposes to generate formaldehyde in small quantities which do not cause side effects. Methenamine was used on the stump of sixteen amputees. The trial was conducted as a double blind study using two different solutions market as solution A and as solution B. The effectiveness of the solutions as an antiperspirant was evaluated clinically by the subjects and the physician. Solution A containing Methenamine, was found significantly effective, both by the subjects and physician when compared with the solution B the blank one. The use of Methenamine as an antiperspirant is recommended in amputation stumps.

The influence of prosthetic foot alignment on trans-tibial amputee gait.

An optimally aligned prosthesis, as accomplished by the subjective judgment of the prosthetist, guarantees the best quality of gait. Yet, amputees can adapt to a large variety of geometrical configurations of the prosthetic components. Different external rotation angles of the foot in trans-tibial (TT) prostheses were investigated. The study tried to identify (a) the relationship between foot angle and other gait parameters and (b) the compensating pattern of the amputees to excessive external rotation of the foot. Eight (8) TT amputees, fitted with an identical type of prosthesis, were investigated during ambulation. The prosthetic foot was externally rotated as follows: optimal angle (10.94 x degrees +/- 5.21 degrees), optimal angle plus another 18 degrees, and optimal angle plus another 36 degrees. Analysis of gait was performed with the aid of an electronic walkway. Speed of gait, stance and swing time, and foot angle were monitored in 4 runs for each of the three foot angles. Speed of gait remained almost constant in the three tests. Stance and swing time, as well as step length, significantly changed when 36 degrees were added to the optimal foot angle. This foot position significantly influenced inter-legs time difference and symmetry between the legs. During ambulation, prosthetic foot external rotation was decreased by internal rotation of the limb at the hip joint level. It is concluded that TT amputees can maintain an efficient speed of gait even when the prosthetic foot is malpositioned in excessive external rotation. Although such a malalignment significantly influences other gait parameters during walking, amputees are able to adapt themselves by internal rotation of the hip joint in the amputated leg.

Stump length as related to atrophy and strength of the thigh muscles in trans-tibial amputees.

Stump length and the thigh muscles strength of the amputated limb are among the major factors influencing outcome of prosthetic rehabilitation of trans-tibial amputees. In the present study the authors evaluated and compared the strength of quadriceps and hamstrings muscles of both limbs in trans-tibial amputees, as measured by means of an electrical dynamometer. The obtained results showed that the thigh muscles of the sound limbs are significantly stronger than those of the amputated limbs (p < 0.01). The results obtained for amputees with shorter stumps were compared with those with longer stumps. In the group of amputees (n = 9) with a stump shorter than 15.1 cm, values of peak torque (in isokinetic contraction) and maximal average torque (in isometric contraction) were significantly (p < 0.5) weaker when compared to those (n = 9) with a stump longer than 15.1 cm. The results obtained for amputees with a higher rate of thigh muscle atrophy were compared to those with lesser atrophy. In the group of amputees where muscle atrophy was accompanied by decrease in thigh girth of over 5.9 cm, muscles strength did not significantly decrease (p < 0.5) as compared to amputees where thigh girth decrease was less than 5.9 cm. It is concluded that atrophy of the thigh muscles of trans-tibial amputees is accompanied with a significant decrease in strength. In amputees with a short stump, the short lever action provided by the stump interferes with the ability of the thigh muscles to control the prosthesis efficiently during daily activities such as standing and walking.