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Biomedical subjects

H J Stam

Publications and source records attributed to H J Stam.

At least 55 records · Page 3Linked to original sources
PubMed1999

Effects of prosthetic mass and mass distribution on kinematics and energetics of prosthetic gait: a systematic review.

OBJECTIVE: To introduce the theoretical models used in literature that describe the relation between prosthetic inertial loading and amputee gait and to derive specific predictions from these models: to systematically review experimental studies on the relation between prosthetic inertial loading and energetics and kinematics of lower-limb prosthetic gait; and to compare the review outcomes with predictions derived from theoretical models. DATA SOURCES: Studies selected from Medline and from examining references in the selected Medline publications. STUDY SELECTION: Theoretical models were selected that are used in the present literature to predict the effects of prosthetic mass and mass distribution on kinematics and energetics of prosthetic gait. Experimental studies were selected that investigated the effects of prosthetic mass or center of mass location on the economy, self-selected walking speed, stride length, or stride frequency of lower limb amputee patients. DATA EXTRACTION: The design and methodologic quality was assessed using a checklist of nine criteria. Data on economy, self-selected walking speed, stride frequency, and stride length were extracted from the studies selected. DATA SYNTHESIS: The predictions of the theoretical models suggest that inertial loading of the present lightweight prostheses need not be decreased and sometimes may need to be increased to improve the gait of amputee patients. The methodologic quality of most of the experimental studies was limited. Review of the experimental studies suggests that the inertial loading of the present lightweight prostheses need not be further reduced. The discrepancy between theoretical models and experimental findings may be related to both the poor methodologic quality of the experiments as well as to the limited predictive value of the existing models.

Amputation, Surgical↗
PubMed1999

A biomechanical model on muscle forces in the transfer of spinal load to the pelvis and legs.

Based on musculoskeletal anatomy of the lower back, abdominal wall, pelvis and upper legs, a biomechanical model has been developed on forces in the load transfer through the pelvis. The aim of this model is to obtain a tool for analyzing the relations between forces in muscles, ligaments and joints in the transfer of gravitational and external load from the upper body via the sacroiliac joints to the legs in normal situations and pathology. The study of the relation between muscle coordination patterns and forces in pelvic structures, in particular the sacroiliac joints, is relevant for a better understanding of the aetiology of low back pain and pelvic pain. The model comprises 94 muscle parts, 6 ligaments and 6 joints. It enables the calculation of forces in pelvic structures in various postures. The calculations are based on a linear/non-linear optimization scheme. To gain a better understanding of the function of individual muscles and ligaments, deviant properties of these structures can be preset. The model is validated by comparing calculations with EMG data from the literature. For agonistic muscles, good agreement is found between model calculations and EMG data. Antagonistic muscle activity is underestimated by the model. Imposed activity of modelled antagonistic muscles has a minor effect on the mutual proportions of agonistic muscle activities. Simulation of asymmetric muscle weakness shows higher activity of especially abdominal muscles.

Abdominal Muscles↗
PubMed1999

Evaluation of restoration of extensor pollicis function by transfer of the extensor indicis.

The aim of this study was to assess long-term results of extensor indicis (EI) to extensor pollicis longus (EPL) transfers and to assess donor site morbidity. A specific EI-EPL evaluation method (SEEM) was used to measure EPL function after transfer. The outcomes in 17 patients are presented. Results were assessed by the Geldmacher score, the SEEM, mobility and strength of thumb and index finger, pinch and grip strength, and a questionnaire, comparing the operated and non-operated hands. Based on the SEEM, the results were excellent to good in 11 of 17 patients. There was no marked loss of independent extension of the index finger and only a 38% loss of extension strength.

Adult↗
PubMed1999

Measurement of sacroiliac joint stiffness in peripartum pelvic pain patients with Doppler imaging of vibrations (DIV).

OBJECTIVES: The research question of the present study was: are sacroiliac joint stiffness levels of peripartum pelvic pain patients different from those of healthy subjects? STUDY DESIGN: A cross-sectional comparative sacroiliac joint stiffness analysis of peripartum pelvic pain patients with healthy subjects. In previous studies we introduced a new technique, Doppler imaging of vibrations (DIV), to assess sacroiliac joint stiffness using colour Doppler imaging and vibrations. The measurements were performed on a group of peripartum pelvic pain patients (n=56) and on a control group (n=52). The differences in sacroiliac joint stiffness between the patient group and the control group were tested statistically by means of the Wilcoxon's two sample test, the chi-square test and Student's t-tests. RESULTS: Both patients and controls displayed stiff as well as unstiff joints with no significant difference. There was a significant difference between the groups with regard to the relative difference of sacroiliac joint stiffness between left and right. CONCLUSIONS: A diagnostic tool which can possibly be developed in the future could demonstrate an objective finding among women with peripartum pelvic pain. DIV is easy to apply and non-invasive. Asymmetric stiffness of the sacroiliac joints seems to be more directly related to low back pain and pelvic pain, not the stiffness level of a single sacroiliac joint.

Adult↗
PubMed1999

Tendon displacement assessment by pulsed Doppler tissue imaging: validation with a reciprocating string test target.

After hand trauma and surgery, assessment of tendon excursion is important in reconstructive surgery and rehabilitation. Aimed as a more reliable alternative to traditional noninvasive methods, a colour Doppler imaging scanner was adapted to measure longitudinal tendon displacement. Displacement was quantified by integrating the velocity estimated from the zero-crossing rate of the Doppler signal. The system was tested by measuring displaced distances of a rubber string that was moved back and forth. At a determined optimal receiver gain, 1.5-cm string displacements were measured with less than +/- 0.05-cm bias throughout an echo-signal dynamic range of 22 dB; standard deviations were around 0.05 cm. Regression analysis between measured and true displacements in the range 0.5-2.5 cm resulted in a best fit straight line with slope 0.927, intercept 0.041 cm and residual standard error of 0.06 cm. A transfer technique was conceived to ensure accuracy when measuring tendons in the body. This CDI-based pulsed Doppler system merits verification for measurement of tendon excursion in patients.

Biomechanical Phenomena↗
PubMed1999

Tennis elbow, natural course and relationship with physical activities: an inquiry among physicians.

BACKGROUND: The main purposes of the study were to answer the following two questions: is a restrictive therapeutic management in case of tennis elbow (TE) better or worse than a regular therapeutic approach and do racket sports and other physical activities influence the risk to get TE and to what extent. METHODS DESIGN: Cross-sectional study by means of a postal questionnaire. The impression was verified that physicians are reserved about medical interventions when treating themselves for tennis elbow. The frequency of therapeutic measures and their results were compared with data reported in literature. Physical activities of physicians who had TE were compared with those of physicians who never had TE. SETTING: Physicians who attended postgraduate courses on diagnosis and treatment in orthopedic medicine from 1984 to 1992. PARTICIPANT: 72 physicians who had TE and 266 with no history of TE. MEASURE: The study is based on self-assessment of therapeutic approaches and their results, reported physical activities at the onset of TE and at the moment of the inquiry. By a team of experts the grade of grasping and/or dorsiflexion of the physical activities was classified. RESULTS: Compared with patients in general practice, physicians treating themselves for TE were more restrictive to use NSAID's, ointments or local steroid injections or to consult a specialist. No-one was treated with surgery and no-one interrupted her/his work because of TE. In all but two of the 72 cases the TE resolved within two years. The odds ratio for TE for playing racket sports versus not playing racket sports was 2.8 (95% confidence interval 1.64-4.82). The odds ratio for activities with low-grade grasping and/or dorsiflexion versus "no sports or hobbies" was 0.11 (0.02-0.50). CONCLUSIONS: Absence from work and therapeutic measures for TE are (in physicians) not necessary for a good result on the long term. Playing racket sports increases the risk to get TE by a factor of 2.8. Performing weekly activities with low grade grasping and/or dorsiflexion of the wrist may have a protective effect against developing tennis elbow.

Adult↗
PubMed1998

Tendon excursion measurements with colour Doppler imaging.

We assessed the applicability of tendon excursion measurement by means of Colour Doppler Imaging (CDI) on human specimens, and also assessed the correlation between values measured by Doppler and by displacement meters. Muscles were separately connected to a mass of 1 kg with a steel wire running over a pulley. This weight moved the telescopic end of a digital displacement meter up and down during passive extension and flexion of the fingers. Excursion was measured with a pulsed multi-channel CDI scanner on the same arm. Assessment of finger tendon excursion with CDI correlated well with the mechanical micro displacement meter, the latter being considered the most accurate method in cadaver studies.

Aged↗
PubMed1998

Ambulatory accelerometry to quantify motor behaviour in patients after failed back surgery: a validation study.

In the treatment of patients with pain, measures related to (pain) behaviour are of major importance. Ambulatory activity monitoring can be used to obtain insight into actual behaviour. This study was designed to validate the Activity Monitor (AM), an instrument based on long-term ambulatory monitoring of accelerometer signals, to assess several physical activities during normal daily life. Ten failed back surgery (FBS) patients performed a number of functional activities in and around their own houses. During the measurements, continuous ambulatory registrations of accelerometer signals were made, based on four body-mounted accelerometers (one on each upper leg, two on the trunk). Video recordings made simultaneously with the measurements were used as a reference. The continuous output of the AM (postures, transitions, dynamic activities) was compared with visual analysis of the videotapes. The overall results showed an agreement between AM output and video analysis of 87% (inter subject range: 83-88%). The maximal error in the determination of the duration of activities was 0.3%. The overall number of dynamic periods was determined well (AM: 359; video: 368), while the number of transitions was slightly overestimated (AM: 228; video: 205). The results when using the three-sensor version of the AM were somewhat less accurate (overall agreement from 87% to 82%). The AM appeared to be a valid instrument to quantify aspects of behaviour of FPS patients, such as duration of activities and number of transitions. This new technique of ambulatory measurement of mobility activities seems to be a relevant and promising extension of the techniques currently used in the evaluation of pain treatment.

Acceleration↗
PubMed1998

EMG recordings of abdominal and back muscles in various standing postures: validation of a biomechanical model on sacroiliac joint stability.

In a biomechanical model we described that for stability of the flat sacroiliac joints (SIJ) muscle forces are required which press the sacrum between the two hip bones (self-bracing). Shear loading of these joints is caused by gravity and longitudinally oriented muscles. Protection against shearing can come from transversely oriented muscles like the internal oblique (OI) abdominal muscles. For validation we used standing postures with significantly more or less OI activity compared to activity in a standardized erect standing reference posture. OI activity decreased significantly when (a) resting on one leg (the contralateral), as can be observed at bus stops, (b) tilting the pelvic backward and (c) applying a pelvic belt. We explain this decrease of OI activity by, respectively, decrease of gravity load, decrease of load from the psoas major muscles, and a substitute of self-bracing. The outcome of this study is in line with the biomechanical model on SIJ stability. Clinical relevance of this study regards aspecific low back pain and is found in the effect of the use of a pelvic belt, of a trunk position as adopted when wearing a small rucksack and of the benefit of exercising trunk muscles in extension and torsion.

Abdominal Muscles↗
PubMed1998

Quantification of physical activities by means of ambulatory accelerometry: a validation study.

The objective of the study was to assess the validity of an activity monitor (AM) within a psychophysiological study. The AM was based on four body-fixed accelerometers and discriminated postures, transitions, and dynamic activities. Three subjects participated in each of two 4-hr sessions. During each session, consisting of two protocols, ambulatory accelerometer and heart rate measurements were made. The output of the AM was compared with simultaneously recorded video tapes. An overall agreement between AM and video of 88 and 96% was found. The number of transitions and dynamic periods, and the duration of activities were well determined. Posture-related heart rate changes were demonstrated. A three-sensor configuration hardly influenced the validity scores. The AM appeared to be a valid instrument to quantify aspects of physical activity, and offers new possibilities for ambulatory psychophysiological research.

Adult↗
PubMed1998

Validity and reliability of measurements obtained with an "activity monitor" in people with and without a transtibial amputation.

BACKGROUND AND PURPOSE: In this study, the validity and reliability of measurements obtained with an "Activity Monitor" (AM) were examined. The instrument is designed to monitor ambulatory activity by use of accelerometer signals, and it detects several activities associated with mobility (standing, sitting, lying, transitions, movement-related activities). SUBJECTS: Four men with a transtibial amputation and 4 men without a transtibial amputation participated. METHODS: The subjects performed normal daily activities, during which accelerations were measured and videotape recording were made (reference method). Validity was assessed by calculating agreement scores between the AM output and the videotape recordings and by comparing the number of transitions and the duration of activities determined by both methods. RESULTS: The overall agreement between the AM output and the videotape recordings was 90%. Other agreement scores, in addition to the determination of the number of transitions and the duration of activities, were generally within a range of error of 0% to 10%. CONCLUSION AND DISCUSSION: The reliability and validity of the AM measurements appeared to be good, which supports its potential use in rehabilitation and physical therapy. [Bussmann HBJ, Reuvekamp PJ, Veltink PH, et al. Validity and reliability of measurements obtained with an "Activity Monitor" in people with and without a transtibial amputation.

Activities of Daily Living↗
PubMed1998

Techniques for measurement and assessment of mobility in rehabilitation: a theoretical approach.

OBJECTIVE: Mobility is an important construct in rehabilitation; many instruments have emerged which measure or assess (aspects of) mobility. In the selection or development of an appropriate technique, knowledge about the fundamentals of rehabilitation medicine is needed, as well as about essential characteristics of techniques and fundamental differences between them. The aim of this paper is to classify, assess and discuss current techniques which are or can be used to measure aspects of mobility. DESIGN: Eight techniques (physical science techniques, clinimetry, observation, diaries, questionnaires, actigraphy, physiological techniques and activity monitors) are classified, assessed and discussed, based on the level of outcome measures, the aspect of mobility they measure, and methodological and practical criteria. RESULTS AND CONCLUSIONS: Rehabilitation medicine has a particular need for instruments that enable measurement of outcome measures on the level of activity and role fulfillment. Techniques differ in the type and number of mobility aspects they measure. Furthermore, important differences exist based on methodological and practical criteria. One optimal technique does not exist: the choice of a technique always depends on a complexity of factors, such as clinical problem, research questions, the mobility aspect of interest, required methodological strength, costs and availability.

Activities of Daily Living↗
PubMed1997

Variations in foot breadth: effect on aspects of postural control during one-leg stance.

OBJECTIVE: To test the hypothesis that changing body weight toward the narrower rearfoot or the wider forefoot causes a decrease or increase in the amount of center of pressure (CoP) displacement per unit of foot tilt (EQ), and to examine the effect on postural control. DESIGN: Experimental, within-subject design with one controlled variable. SETTING: A biomechanics laboratory of a university department of biomedical physics and technology. SUBJECTS: Ten healthy, young subjects. MAIN OUTCOME MEASURES: The sagittal plane position of the CoP (Y) reflecting foot loading, EQ, and horizontal ground reaction forces (Fx) representing postural control. RESULTS: Shifting body weight to the rearfoot or forefoot decreases (d) or increases (i) Y (Pd = .002, Pi = .000) and EQ (Pd = .018, Pi = .064). In both cases Fx (Pd = .008, Pi = .098) increased and postural control deteriorated. CONCLUSIONS: Shifting body weight to the rearfoot or forefoot decreases or increases EQ. Besides the changes in EQ encountered here, other factors are held responsible for the deterioration of postural control. The absence or presence of changes in Y can be used to exclude or include the presence of an effect of EQ or these unknown factors on postural control.

Adult↗
PubMed1997

Routing through the health care system and level of functioning of lower limb amputees.

OBJECTIVES: To describe the routing through the health care system and the level of functioning of a consecutive series of lower limb amputees at a general Dutch hospital. METHODS: A descriptive cohort study (medical records examination) with a follow-up interval of 11.7 months. All 124 major lower limb amputations (ankle to hip) between 1 July 1989 and 31 December 1992 are included in the study: 123 patients, average age 73.8 years, 96% vascular disease. Amputation levels are 55.3% transfemoral, 12.2% knee disarticulation and 32.5% transtibial. At follow-up two patients are missing. RESULTS: Before admission to hospital 75.6% of patients are able to walk and 79.9% live independently. Discharge destinations from hospital are 22.5% home, 42.3% inpatient rehabilitation and 32.4% nursing home. At follow-up, 59% of surviving patients have a prosthesis, 47.7% are able to walk and 70.5% live independently. Mortality after one year is 28.5%. Poor preoperative walkers seem to die more often within the first year and have less chance of being fitted with a prosthesis. Poor walkers, older than 75, with diabetes mellitus and a transfemoral amputation seem to stay more often in a nursing home after one year. DISCUSSION: Although the results are largely comparable with other studies, there appear to be differences in age, amputation level and course and duration of treatment. The predicting factors found here may help the rehabilitation specialist in advising on the best moment and level of amputation and course of treatment.

Activities of Daily Living↗
PubMed1996

Understanding peripartum pelvic pain. Implications of a patient survey.

STUDY DESIGN: An analysis was made of the self-reported medical histories of patients with peripartum pelvic pain. OBJECTIVES: To compile an inventory of the disabilities of patients with peripartum pelvic pain, analyze factors associated with the risk for development of the disease, and to formulate a hypothesis on pathogenesis and specific preventive and therapeutic measures. SUMMARY OF BACKGROUND DATA: Pregnancy is an important risk factor for development of chronic low back pain. Understanding the pathogenesis of pelvic and low back pain during pregnancy and delivery could be useful in understanding and managing nonspecific low back pain. METHODS: By means of a questionnaire, background data were collected among patients of the Dutch Association for Patients With Pelvic Complaints in Relation to Symphysiolysis. Results were compared with the general population. Subgroups were compared with each other. RESULTS: Peripartum pelvic pain seriously interferes with many activities of daily living such us standing, walking, sitting, and all other activities in which the pelvis is involved. Most patients experience a relapse around menstruation and during a subsequent pregnancy. Occurrence of peripartum pelvic pain was associated with twin pregnancy, first pregnancy, higher age at first pregnancy, larger weight of the baby, forceps or vacuum extraction, fundus expression, and a flexed position of the woman during childbirth; a negative association was observed with cesarean section. CONCLUSIONS: It is hypothesized that peripartum pelvic pain is caused by strain of ligaments in the pelvis and lower spine resulting from a combination of damage to ligaments (recently or in the past), hormonal effects, muscle weakness, and the weight of the fetus.

Adult↗
PubMed1996

Colour doppler ultrasound examination of hand tendon pathologies. A preliminary report.

Apart from real-time sonography, in most of the imaging techniques used to examine the musculoskeletal system, such as X-ray, computerized tomography scan and magnetic resonance imaging produce mainly static images. Although colour Doppler imaging (CDI) is generally used in the examination of blood flow, it may offer the opportunity to study the dynamic characteristics of tendons and muscles. The purpose of this study was to examine the unilateral flexor and extensor tendon pathologies of the hand and compare these images with the healthy side. A Phillips Quantum Doppler was used to study patients with tendon adhesions and trigger finger. The normal and pathological tendons were scanned at three anatomical levels: wrist, metacarpal and proximal phalanx. The results obtained from the comparison of pathological images with normal ones indicate that CDI offers a promising approach to image dynamically and, in the future, to quantify the function of the tendons and muscles in the musculoskeletal system and to define their pathologies.

Adolescent↗