Biomedical subjects

H Lanshammar

Publications and source records attributed to H Lanshammar.

9 recordsLinked to original sources

PubMed1995

A marker-free method to estimate joint centre of rotation by video image processing.

A marker-free video measurement and image processing method that provides numerical estimation of the 2-D centre of rotation of one rigid segment is tested. The algorithm is based on binary region moment features. A comparison is made between this method and a marker-based one, where the location of the markers has been calculated in two ways. The algorithm is also extended to handle two rigid segments. The method is to be applied in human locomotion analysis in order to calculate the centre of rotation of the hip joint. It's accuracy has been tested by a comparison with in vivo radiological measurements on humans.

Adult↗

PubMed1995

Knee joint moments in work-related situations.

Circumstantial evidence in the literature points towards a relationship between heavy labour and arthrosis of the knee. The aim of this study was to demonstrate which occupational activities yield the greatest knee moments and thus indicate possible gonarthrosis-inducing occupational hazards. Twelve healthy and uninjured medical students were studied in set occupational situations in a laboratory for gait analysis, using a force plate with video display of force vectors and knee joints (VIFOR). With normal walking as a baseline for moment it was found that activities involving knee flexion, such as lifting objects from one level to the other, climbing stairs and ladders, and jumping down, revealed a significant increase in moment. On the other hand, carrying objects in one or both hands did not yield significant increase in knee moment compared with normal walking. Flexed knee lifting had significantly lower moment than jumping down from a height of 0.5 m on to one or both feet. Three levels of knee moment could thus be identified, i.e., normal walking, flexed knee lifting and jumping down.

Adult↗

PubMed1995

A relationship between dynamic and static assessments of knee joint load. Gait analysis and radiography before and after knee replacement in 45 patients.

In a prospective study of 45 gonarthrosis patients treated with total knee arthroplasty, we performed gait analysis with the Vifor system preoperatively and 6 months and 2 years postoperatively. An evaluation was made of the relationship between dynamic measurements of knee joint load and static, radiographic measurements of alignment. Correlations were found between the knee joint moments in the frontal plane and the Hip-Knee-Ankle (HKA) angles on all measurement occasions, likewise between changes of moments and changes in HKA by the operation. Thus, static alignment reflects the loading conditions during gait.

Aged↗

PubMed1982

On practical evaluation of differentiation techniques for human gait analysis.

Numerical differentiation of noisy measurement data represents a problem frequently encountered in the field of gait analysis. There are two major determinants of the quality in calculated derivatives, namely the quality of the measurement data and the quality of the used differentiation technique. The quality of the measurement data, with respect to the maximum precision that can be obtained in calculated derivatives, is discussed with the help of an error formula valid for all differentiating techniques. It is verified that high precision can be obtained in the calculated second derivatives even with crude techniques, provided that the quality of the measurement data are good enough. This point is illustrated by the differentiation film data from Pezzack et al. (1977), using a least squares polynomial fitting. For the evaluation and comparison of different techniques for numerical differentiation it is recommended that measurement data with a considerable amount of noise is used, and that the quality of calculated derivatives are evaluated not only by visual inspection of graphical displays, but also with the use of a quantitative criteria, such as the root mean squares error.

Biomechanical Phenomena↗

PubMed1982

On precision limits for derivatives numerically calculated from noisy data.

This paper has three purposes. (1) To verify an error formula from which the maximal precision in derivatives obtained from noisy measurement data can be calculated. The formula is verified by comparison with the resulting noise in derivatives obtained by local least squares polynomial fitting. It is also verified that differentiation by Fourier series expansion gives noise exceeding the minimum value according to the error formula. (2) An index called the "Relative Noise Amplification" (RNA) is introduced. For an arbitrary differentiating filter it is defined as the noise transmission of the filter divided by the minimal noise transmission according to the above mentioned error formula. When the filter produces unbiased estimates the value of the RNA always exceeds one. The RNA can be used as a quality index for differentiating filters. The filter with the smallest value on the RNA also has the smallest amount of noise superimposed on the calculated derivatives provided the input noise is white and additive. (3) The bandwidth and the Relative Noise Amplification of differentiating filters obtained by local least squares polynomial fitting are presented. The 0th, 1st and 2nd order derivatives have been investigated for polynomials up to 8th order. These results can be used for the determination of suitable filter parameters in various applications.

Biomechanical Phenomena↗

PubMed1982

Variation of mechanical energy levels for normal and prosthetic gait.

Mechanical energy levels were investigated for normals and for below-knee amputees during level walking. The weight of the prostheses was varied by attaching 0.5 kg extra weight to the prostheses. The measurements and analyses were made with the ENOCH system consisting of a minicomputer (HP 21 MX), an optoelectronic device for displacement data measurement (Selspot) and a force plate (Kistler) for measurement of ground reaction forces. Results by Winter et al (1976) on the energy changes during normal walking obtained from displacement data on one leg only were verified using data from both legs and the trunk. For the amputees it was concluded that the energy changes increased for the prosthetic shank when the weight increased. For the other body segments and for the body total no significant differences were found.

Adult↗

PubMed1982

An investigation of kinematic and kinetic variables for the description of prosthetic gait using the ENOCH system.

Gait patterns, joint angles, floor reaction forces and joint moments during walking were investigated for normal subjects and above-knee and below-knee amputees. The investigation showed that the hip-knee angle diagram as well as different symmetry diagrams (e.g. left knee angle versus right knee angle) provide an easily interpreted means of evaluating abnormalities in the gait pattern. It was further concluded that a combined gait pattern-force vector diagram is valuable for the evaluation of the joint moments. Floor reaction forces and muscular moments at the joints were also included in the analysis. The joint moments at the knee were quite different for both above-knee and below-knee amputees as compared to the normal subjects. Some interesting trends were also found concerning the knee stability of the amputees. A system called ENOCH was used for the measurement and analysis. This system consists of a minicomputer connected on-line to equipment for measurement of displacement (Selspot) and floor reaction forces (Kistler). A graphic computer terminal (Tektronix) was used for the result presentation.

Amputation, Surgical↗

PubMedDate not supplied

Postoperative evaluation of Keller's arthroplasty and arthrodesis of the first metatarsophalangeal joint using the EMED gait analysis system.

The authors examined 10 patients who had arthrodesis at the first metatarsophalangeal joint and 10 patients who had Keller's arthroplasty operation. The EMED gait analysis was used to measure the pressure distribution over the sole of the foot during walking. Arthrodesis group had significantly increased maximum pressure in the first and third metatarsal regions. The Keller arthroplasty group had the lowest maximum pressure in the big toe but it was not significant.

Adult↗

PubMedDate not supplied

Postoperative pressure under the rheumatic feet.

The authors examined ten seropositive rheumatoid arthritis patients with an EMED gait analysis system in a mean four years after foot surgery and compared that with ten normal subjects who formed a control group. The maximum pressure in the toe regions was almost the same as in the control group. The rheumatoid arthritis group had significantly increased maximum pressure in the first metatarsal and tarsal region.

Adult↗