Tracking the motion of hidden segments using kinematic constraints and Kalman filtering.

Motion capture for biomechanical applications involves in almost all cases sensors or markers that are applied to the skin of the body segments of interest. This paper deals with the problem of estimating the movement of connected skeletal segments from 3D position data of markers attached to the skin. The use of kinematic constraints has been shown previously to reduce the error in estimated segment movement that are due to skin and muscles moving with respect to the underlying segment.

Correlation between clinical assessment and force plate measurement of postural control after stroke.

Objectives: To explore the correlation between clinical assessment and force plate measurement of postural control after stroke when selected balance tasks are performed under similar spatial and temporal conditions, and to examine the inter-rater agreement of assessment of weight distribution during quiet stance in subjects with stroke.

Design: A descriptive and correlational study.

Methods: Clinical assessment of postural control using Berg Balance Scale, video recording for rating of weight distribution, and force plate measurement with the Vifor-system, were performed in 20 subjects with stroke.

Possibilities of texture based motion analysis.

Analysis of motion patterns in the human locomotion apparatus is important in many clinical areas like orthopaedics, physiotherapy, neurology, and sports medicine. Today marker based human motion analysis (HMA) is completely dominant in the clinical context. Technically, these systems are stable and dependable, and about a dozen variants are commercially available.

Using an extended kalman filter for rigid body pose estimation.

Rigid body pose is commonly represented as the rigid body transformation from one (often reference) pose to another This is usually computed for each frame of data without any assumptions or restrictions on the temporal change of the pose. The most common algorithm was proposed by Söderkvist and Wedin (1993, "Determining the Movements of the Skeleton Using Well-configured Markers," J. Biomech.

Relationships between fore- and hindlimb ground reaction force and hoof deceleration patterns in trotting horses.

Reasons For Performing Study: The transmission of shockwaves following hoof impact is proposed to be one major source of stress to the limb. In the forelimb, there are indications that the period of horizontal deceleration of the hoof is related to the attenuation of shockwaves. In the hindlimb, information about the hoof deceleration has been lacking.

Force measurements of postural sway and rapid arm lift in seated children with and without MMC.

Objective: The aim was to investigate the horizontal ground reaction forces of seated postural sway and rapid arm lift in children with and without myelomeningocele. BACKGROUND; It is unclear whether children with myelomeningocele have limited control of body posture entirely caused by the impairment in the legs or also by other dysfunction.

Methods: 11 children with myelomeningocele, 10-13 years, and 20 children without physical impairment were investigated.

Biomechanics of slips.

The biomechanics of slips are an important component in the prevention of fall-related injuries. The purpose of this paper is to review the available literature on the biomechanics of gait relevant to slips. This knowledge can be used to develop slip resistance testing methodologies and to determine critical differences in human behaviour between slips leading to recovery and those resulting in falls.

Amplitude and frequency analysis of force plate data in sitting children with and without MMC.

Objective: To investigate if force plate measurements can be used to detect postural sway differences in sitting children with and without myelomeningocele (spina bifida).BACKGROUND. The postural sway has not been investigated in children with myelomeningocele previously.

From stride period to stride frequency.

The stride-cycle frequency of gait data is often estimated by taking the inverse of the average stride-cycle time (stride period) over several stride-cycles. We derive the density function of the stride-cycle frequency frequency (stride frequency) and describe some of its properties. We also show the conditions under which the inverse of the mean stride period is a 'good' estimate of the mean stride frequency.

Dominant pattern extraction from 3-D kinematic data.

A new method for the extraction of a repeating pattern in cyclic biomechanical data is proposed--singular value decomposition pattern analysis (SVDPA). This method is based on the recent work of Kanjilal and Palit [14], [15] and can be applied to both contiguous and repeated trials without being constrained to be strictly periodic. SVDPA is a data-driven approach that does not use a preselected set of basis functions; but instead utilizes a data matrix with a special structure to identify repeating patterns.

Gait abnormalities in diabetic neuropathy.

Objective: To investigate the effect of peripheral neuropathy on gait in diabetic patients.

Research Design And Methods: Gait analysis was performed in the following groups matched for age, sex, and BMI: 20 normal healthy control subjects (NC), 20 non-neuropathic diabetic control subjects (DC), 20 neuropathic diabetic subjects (DN), and 20 neuropathic diabetic subjects with a history of foot ulceration (DNU). All subjects with orthopedic foot problems were excluded from the study.

Estimation of the knee joint location using colour video.

Analysis of the knee joint moment might be useful for predicting the risk of prosthetic loosening. The moment can be estimated if the location of the centre of pressure in the knee joint and the ground reaction force vector are known. Usually, skin mounted markers are used to locate the knee joint centre.

Knee joint loading and tibial component loosening. RSA and gait analysis in 45 osteoarthritic patients before and after TKA.

We report a prospective study of gait and tibial component migration in 45 patients with osteoarthritis treated by total knee arthroplasty (TKA). Migration was measured over two years using roentgen stereophotogrammetry. We used the previously established threshold of 200 microm migration in the second postoperative year to distinguish two groups: a risk group of 15 patients and a stable group of 28 patients.

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.

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).

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.

Ground reaction force and its moment with respect to the knee joint centre in a total condylar arthroplasty series.

In a group of patients with rheumatoid arthritis (n = 5)and osteoarthrosis (n =3) who had had had 12 total condylar knee arthroplasties a new technique for assessment of ground reaction forces was used. This technique graphically displays force vectors superimposed in real time on a video recording of the subject walking. We found that this new technique could assess reliably moments of the ground reaction force vectors with respect to the centre of the knee joint.

Assessment of foot disorders using biomechanical analysis of foot loads during locomotion.

The aim of this study was to investigate techniques for assessment of surgical procedures for foot disorders. An optoelectronic system was used to obtain position data during walking for the knee joint, ankle joint and the second metatarsal joint. The ground reaction forces were simultaneously measured and the moment of force at the mentioned joints were analysed.

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.

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.

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.

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.

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.

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.