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Biomedical subjects

Z Susak

Publications and source records attributed to Z Susak.

At least 19 recordsLinked to original sources
PubMed1997

Predicted and measured muscle forces after recoveries of differing durations following fatigue in functional electrical stimulation.

Using 31P nuclear magnetic resonance (NMR) spectroscopy, the bioenergetics of paralyzed muscles activated by functional electrical stimulation (FES) were studied in vivo during fatigue and recovery on paraplegic subjects. During the activation phase of the muscle, the muscle force was also monitored. The phosphorus metabolites were found to vary systemically during the fatigue and to recover slowly to their rest state values after cessation of FES. During fatigue, a good correlation was found between the decaying force and each of the profiles of phosphocreatine, inorganic phosphorus, and intracellular pH. A musculotendon 5 element model was proposed for the activated muscle to predict its force generation capacity. A fatigue recovery function, based on the metabolic profiles, was introduced into the model. This model allowed us to predict the force expected to be developed as a function of the time after recovery of given time durations. Validation experimental measurements of force were carried out and included recurrent fatigue tests, both in the initially unfatigued state and at various times in the postfatigue stage of the muscle. Comparison of the predicted and measured forces indicated satisfactory agreement of the results. The developed model of muscle dynamics should help to design a strategy for reducing muscle fatigue under FES.

Electric Stimulation Therapy↗
PubMed1996

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.

Administration, Topical↗
PubMed1995

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.

Bone and Bones↗
PubMed1993

Computer-controlled portable stimulator for paraplegic patients.

A six-channel lightweight, portable and computer-controlled stimulator for the functional activation of paraplegic patients is described. To enable programming of the various functions, the stimulator was designed to work in a remote-control mode hosted by an IBM PC or compatible computer, in addition to its normally used local mode. The stimulus parameters, including current intensity, stimulus frequency and pulse width, are individually adjustable and programmable for each channel. The power source is 12 V 500 m Ah-1, from 10 rechargeable nickel cadmium batteries, with a run time of 1.5 h for a load of 200 mA in four channels. Various training programmes for the activation of paraplegics in the sitting, standing and walking positions are described. The final design of the stimulator is based on experience gained from 25 patients, treated and evaluated during the course of development. Ongoing work including clinical, biomechanical and physiological studies is carried out to evaluate performance of the activated patients and to optimize stimulation.

Humans↗
PubMed1992

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.

Amputation Stumps↗
PubMed1992

A Swedish knee-cage for stabilizing short below-knee stumps.

Stump length is an important factor in attaining successful prosthetic rehabilitation in below-knee (BK) amputees. Stability of the stump-prosthesis complex is impaired in the case of a stump shorter than 10 cm. Thus, fitting a prosthesis to a BK amputee with a stump which is very short often requires the use of different prosthetic techniques. In this work, the authors suggest the use of a Swedish knee-cage attached to a conventional patellar-tendon-bearing prosthesis as an alternative solution in the case of a short BK stump. Objective evaluation was performed by an analysis of gait and the foot-ground reaction forces. The results obtained indicate an improvement in all the measured parameters resulting from the modified stump-prosthesis complex.

Adult↗
PubMed1992

Standing sway and weight-bearing distribution in people with below-knee amputations.

Upright stability in humans has been found to decrease with age, certain diseases, or trauma. We investigated stability of standing in people with below-knee amputations (BKA) and in able-bodied controls. Body sway was evaluated during standing on a set of two Kistler force plates, first with eyes open and then with eyes closed. People with BKA were tested twice--first, one to two days after receiving their prostheses, and second, on completing their prosthetic rehabilitation. The results indicate that both able-bodied people and those with BKA sway more with their eyes closed. However, people with BKA are significantly less stable when they stand with either closed eyes or open eyes. We demonstrated that the differences between the groups studied are due to a proprioceptive deficit as a result of partial limb loss. We also found that there was a gradual process of compensation and adaptation, as some people with BKA sway less at the end of the rehabilitation period.

Adaptation, Physiological↗
PubMed1990

Recruitment, force and fatigue characteristics of quadriceps muscles of paraplegics isometrically activated by surface functional electrical stimulation.

This study deals with the recruitment characteristics of unfatigued electrically stimulated quadriceps muscles of paraplegic subjects and with the time-dependent force output of these muscles under sustained stimulation conditions. Both these aspects of the performance of paralysed stimulated muscles were studied under isometric conditions and at different muscle lengths. The forces in the knee joint resulting from stimulation of the quadriceps were also calculated. Recruitment force curves due to a ramp-like stimulation function indicated a strong dependence on muscle length and demonstrated a sigmoid-shaped curve with three distinct regions: negligible force up to threshold stimulation intensity; rapid force increase; and levelling-off of the curve after which the force remains constant even though intensity is further increased. When normalized to the maximal force, recruitment was found to be independent of muscle length, generating a typical recruitment curve for every patient, under isometric stimulation. The peak forces were obtained at the same flexion angles previously published for normal subjects, but with much lower values. Muscle fatigue in tetanic isometric conditions, defined as the decrease in force due to sustained stimulation with fixed parameters, was found to be length dependent and to have a double exponential decay. The first is the acute force loss and is the more significant for functional purposes; the second is the more moderate and asymptotic region, in which partial force recovery in the form of bursts is observed.

Biomechanical Phenomena↗
PubMed1990

The dynamics of the subtalar joint in sudden inversion of the foot.

The human subtalar joint was modelled as a quasi-linear second-order underdamped system to simulate sudden inversion motion of the foot relative to the shank. The model was fed with experimental data obtained from six subjects on a specially constructed apparatus. A total of 35 deg inversion was produced on the tested leg rapidly enough (lasting less than 40 ms) in order to ensure that the protective muscles are not activated. The parameters of the joint were evaluated and the following ranges were obtained at 35 deg inversion: elastic stiffness 14-52 Nm rad-1, damping coefficient 1.4-2.9 Nms rad-1, and natural frequency 78-125 Hz. The effects on the test parameters of weight bearing amount, foot dominance, and protective footwear were studied on one subject.

Adult↗
PubMed1990

Preoperative and postoperative gait evaluation in cerebral palsy.

The purpose of the study was to evaluate objectively and quantitatively the possible effects of surgical correction for equinus deformity on the gait of children with cerebral palsy (CP). Evaluation criteria selected were based on time and distance parameters of stride during gait. Ten children with confirmed diagnoses of CP took part in the study. They were tested before surgery and after surgery at four-month intervals for a period of up to one year. Results were compared to published data obtained on able-bodied, growing children to determine whether progress after the operation was faster than that expected in normal growth. Gait improvement was demonstrated by a decrease in support time and an increase in walking speed and stride length. Overall improvement was sometimes preceded by an initial, temporary deterioration. Results indicate that the time and distance parameters of stride can provide reliable objective evaluation of gait improvement after tendo Achilles lengthening in children with CP.

Achilles Tendon↗
PubMed1989

Bi-lateral reactive force patterns in postural sway activity of normal subjects.

Postural activity of normal subjects while standing still, as measured via the reactive foot-ground reactive forces, was investigated separately for each of the supporting legs, to provide detailed information on the individual activity of each side. Such information is not accessible if the overall reactive forces on the whole body are measured instead. Twenty-three normal adult subjects (average age 41 years) took part in the measuring tests, which were made on two collaterally installed force platforms. From the force traces obtained, the following parameters were determined: timings and amplitudes of the waveforms, separately for each foot and sequence of the force vectors on both feet and in relation to each other. Weight-bearing imbalance was defined in the vertical direction to express the difference between the average forces supported by each of the legs. Two parameters were defined by combining the force results obtained on each of the legs in the horizontal plane: sway total activity, representing the resultant of the added vector-norms in the anteroposterior and mediolateral directions, respectively; and asymmetry, representing the resultant of the subtracted above vector norms. The results indicated that, although the force traces were synchronous to each other, different vectorial force patterns were found, indicating different levels of stabilizing activities on each of the legs. This was also demonstrated by the fact that sway total activity was found considerably higher than the net reactive forces acting on the whole body during sway.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1989

Standing posture of craniocerebral injured patients: bi-lateral reactive force patterns.

Bi-lateral force measurements on the supporting limbs in postural sway while standing still were carried out to evaluate postural stability of craniocerebral injured (CCI) patients. Brain pathology of these patients was characterised by CT scans and MRI, as well as by their cognitive and behavioural disturbances. Normal subjects of the same age group were tested as controls. From the force tracings obtained, three oscillation frequencies were identified, with orders of magnitudes of 6, 1.5 and 0.1 Hz, respectively, of which the middle frequency, i.e. that corresponding to 1.5 Hz, was selected for subsequent processing and analysis, which included the determination of relative sequence of the force vectors on both feet and evaluation of timings and amplitudes of the waveforms. Weight-bearing imbalance was defined in the vertical direction to express the difference between the average forces supported by each of the legs. In the horizontal plane, two parameters were defined: Sway Total Activity (SA), to represent the vector summation of the absolute values of the horizontal force components acting on both legs; and Asymmetry (ASYM), to express the difference in activities between the two legs. The results presented disclose the reactive force patterns acting on each of the legs of CCI individuals, in comparison with normal individuals. Although the forces were shown to act synchronously on both legs, in most of the patients, they appeared to be asymmetrical in nature, with a typical vectorial pattern for every individual, which generally differed from that of normal subjects. Sway activity was found to be significantly higher in the CCI group as compared with that of the normal controls. These results justify the necessity to study the activity of each of the legs, rather than that corresponding to the resultant forces acting on the whole body, when treating the external forces involved in the stabilisation and regulation of the standing posture of these patients. An attempt to grade the patients according to ascending order of neurological deficits disclosed that their sway disturbances, as revealed by the magnitude of sway total activity and asymmetry, had a tendency to be related to the severity of neurobehavioural disturbances.

Adult↗
PubMed1986

Alignment procedure for the optimal fitting of lower limb prostheses.

Systematic methods for optimizing the fitting and alignment of artificial legs were developed in this study. The procedures were based on gait analysis and included the following aspects: stump-prosthesis interface or socket geometry, the selection of components from which the artificial leg was constructed, and dynamic alignment of the prosthesis. The amputee's adaptation to deliberately imposed perturbations in his prosthesis, and the resulting compensatory mechanisms are also discussed.

Amputation, Traumatic↗
PubMed1986

A modified knee disarticulation. A case report.

A 36-year-old man with posttraumatic transarticular knee (TK) amputation illustrates the difficulties of prosthetic fitting. The excessively long and deformed stump was successfully overcome by an unusual surgical technique consisting of the shortening of the femoral bone by an osteotomy and plate fixation with preservation of the integrity of the condyles to correct the deformity. A short review of the literature concerning the advantages and limitations of TK amputations demonstrates some of the previously-reported surgical techniques.

Adult↗
PubMed1985

Energy expenditure and cardiac response in above-knee amputees while using prostheses with open and locked knee mechanisms.

The difference in physiological responses to ambulation effort, of above-knee (AK) amputees, using a prosthesis with open or locked knee mechanism was investigated at the Orthopaedic Rehabilitation Department of the Loewenstein Hospital. Of seventeen patients who were examined, fourteen were vascular patients over the age of fifty, and three were young traumatic amputees. Subjects performed an unrestrained walking test, using their prosthesis with an open-knee, and then with a locked knee joint mechanism. Heart rate and walking speed were measured, while oxygen consumption was evaluated only in the young patients. Results show that the use of a locked-knee joint resulted in a lower increase in heart rate in both groups. Comfortable walking velocity, as chosen by the subject himself, was higher with a locked-knee joint in the aged group and with an open-knee joint in the younger amputees. Oxygen consumption as measured for the younger patients was higher with an open-knee joint. In conclusion, a locked knee is recommended for the older amputees as it enables a higher walking velocity and lower effort. The preference of an open-knee in the young amputees is due to their better physical condition which enables a higher walking speed although energy expenditure and heart rate are higher.

Adult↗
PubMed1985

In vivo biomechanical evaluation of nail-plate fixation of femoral neck fractures of rehabilitated patients.

A major advantage of internal fixation of intertrochanteric fractures is that it can normally be followed by early and fast rehabilitation of the patient, finding expression in weight bearing and locomotion abilities of the patients. Complications which nevertheless occur, are mostly of mechanical origin. The purpose of our study was to evaluate the biomechanical performance of rehabilitated patients treated with four different types of nail-plates. Forty nine patients (12 men and 37 women) with walking ability, and with an average age of 70.5 years, were tested on a 10 m walkway, instrumented for the monitoring of the time distance parameters of the stride. This method of evaluation is especially suitable for pathological gait, free or supported, as it does not impose any constraints on the natural and individual walking trend of the patient. The average time elapsed between the actual fracture and the locomotor test was 764 days, implying that the investigated patients formed a homogeneous, well-rehabilitated group. The main average stride results were as follows: contact time 1.25 sec, double contact time 0.41 sec, stride length 68.2 cm, velocity 51.39 cm/sec and symmetry 0.51. No significant differences were found in these parameters between the subgroups of patients using different nail-plates. These results show that while the biomechanical performance of the patients with their implants was satisfactory (good walking symmetry) this group can be characterized by its smaller stride and slower gait, compared to those of a healthy population of the same age.

Activities of Daily Living↗
PubMed1985

Biomechanical evaluation of an adjustable patellar tendon bearing prosthesis.

The purpose of this study was to determine the relation between geometry of the patellar tendon (PT) insertion in the socket and the dynamic load transmitted through the PT, in a patellar tendon bearing (PTB) prosthesis. The dynamic load was measured by a specially constructed two-component load cell, which was mounted on the experimental prosthesis. Geometry of the PT insertion relative to the socket was altered by adjusting the location of the mounting frame-load cell assembly. Evaluation of performance of the prosthesis in the range of geometries investigated was made objectively by gait analysis of the patients. The latter was performed on a 10 m walkpath, including at halfway two forceplates, from which the foot-ground forces were recorded. Simultaneously, the PT forces on the prosthesis, as sensed by the load cell were monitored. Computer processing of the data included full analysis of the force-trace and the determination of criteria for optimization of the PT insertion. The resulting criteria were those which expressed minimization of abnormalities in the foot-ground forces of each patient, such as vertical and braking forces and their timings. The complete optimization procedure, which was undertaken for two below-knee male amputees, indicated the correct positioning of the PT insertion, actually taken in the final fitting procedure of the socket of the prosthesis.

Adolescent↗