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. OBJECTIVE: To compare hoof deceleration patterns between the fore- and hindlimbs. METHODS: Seven Standardbreds were trotted by hand over a force plate covered with sand, with triaxial accelerometers mounted on the fore and hind hooves. Variables representative of decelerations (first 2 main vertical deceleration peaks; characteristic minimum and maximum values in the craniocaudal deceleration; hoof braking time) and ground reaction forces (vertical loading rates; maximum and the following local minimum of the craniocaudal force) of the initial part of the stance phase, and the differences between individual fore- and hindlimb time and amplitude variables were used for statistical analyses. RESULTS: Force plate data showed significantly greater vertical loading rate (mean +/- s.d. 6.5 +/- 5.9 N/sec) and horizontal loads (190.4 +/- 110.2 N) in the forelimb than the hindlimb, but the parameters from accelerometer data showed no significant differences. CONCLUSIONS: No significant difference was found in the hoof deceleration, but the deceleration curves displayed a common pattern that described in detail the kinematics of the fore and hind hooves during the initial period of hoof braking. POTENTIAL RELEVANCE: These results contribute to further knowledge about the characteristics of these potential risk factors in the development of subchondral bone damage in the horse. Further studies are required on the influence of hoof braking pattern at higher speed, different shoeing and ground surfaces with different properties.

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. Ground reaction forces at the shoe-floor interface have been extensively studied and are probably the most critical biomechanical factor in slips. The ratio of the shear to normal foot forces generated during gait, known as the required coefficient of friction (RCOF) during normal locomotion on dry surfaces or 'friction used/achievable' during slips, has been one biomechanical variable most closely associated with the measured frictional properties of the shoe/floor interface (usually the coefficient of friction or COF). Other biomechanical factors that also play an important role are the kinematics of the foot at heel contact and human responses to slipping perturbations, often evident in the moments generated at the lower extremity joints and postural adaptations. In addition, it must be realized that the biomechanics are dependent upon the capabilities of the postural control system, the mental set of the individual, and the perception of the environment, particularly, the danger of slipping. The focus of this paper is to review what is known regarding the kinematics and kinetics of walking on surfaces under a variety of environmental conditions. Finally, we discuss future biomechanical research needs to help to improve walkway-friction measurements and safety.

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. Since many of these children are not able to stand independently, force plate measurements during sitting could be one way to detect differences in their postural sway compared to normal children. However, there is very little published regarding assessment of seated postural sway.METHODS. Force plate measurements on 15 six years old children with myelomeningocele and 20 age-matched normal children were analysed. The standard deviation and the median frequency of the horizontal ground reaction force were used to characterise the body sway.RESULTS. The standard deviation of the force was larger only for some of the children with myelomeningocele as compared to the control group. The median frequency was significantly lower in the myelomeningocele group as compared to the control group. Visual input and seat base inclination did not influence the postural sway significantly. CONCLUSIONS: The results show that frequency analysis can be used to detect fundamental differences in postural sway that can not be observed visually. RelevanceIn this paper a new method for analysis of seated postural sway is described. The lack of relatively high spectral frequencies for children with myelomeningocele shows that the output from the postural control system differs as compared to the control group.

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. Several important features of SVDPA are described including its close relationship to the Kahunen-Loève transform. The dominant pattern is defined as the average energy component (AEC). The AEC is obtained from the SVD of the data matrix and is equivalent to the optimal [maximal signal-to-noise ratio (SNR)] ensemble average pattern. The degree of periodicity and SNR for the AEC are defined explicitly from the singular values of the data matrix. We illustrate the usefulness of SVDPA for dominant pattern extraction by applying it to the quasiperiodic three-dimensional trajectory of a marker attached to the trunk during treadmill locomotion. The AEC obtained for the normalized trajectory and error estimates at each point suggests that SVDPA could be a useful tool for the extraction of the fine details from cyclic biomechanical data.

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. Copyright 1998 Elsevier Science B.V.

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. The following gait parameters were investigated: 1) walking speed; 2) stance phase duration; 3) joint angles and moment arms for the ankle, knee, and hip joints in both sagittal and frontal planes; 4) the components of the ground reaction force (GRF) vector; and 5) the ankle, knee, and hip joint moments originating from the GRF vector in both planes. RESULTS: There were no statistical differences in any of the parameters studied between the NC and DC groups. Walking speed was significantly slower in the DNU group compared with the two control groups (P < 0.02). The maximum knee joint angle was smaller in the sagittal plane for the DNU group compared with the DC group values (P < 0.05). The maximum value of the vertical component of GRF was found to be higher (P < 0.03) in the two control groups compared with the DNU group. The maximum value of the anteroposterior forces was also found to be higher (P < 0.001) in the DC group compared with the DNU group. The maximum frontal plane ankle joint moment was significantly higher (P < 0.05) in the DN compared with the NC group. CONCLUSIONS: Diabetic subjects with peripheral neuropathy demonstrate alterations in some gait parameters during walking. These alterations could facilitate foot injuries, thus contributing to frequent foot ulceration.

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. Since marker based methods have several drawbacks investigations of alternative methods are needed. A new method for location of the knee joint is outlined in this paper. The subject is video filmed during gait with an elastic blue band wrapped around the knee. The band is located by splitting the video images into the RGB-components, and the centroid of the band is used as an estimate of the knee joint centre location. The band is easier to mount than markers, and it is not sensitive for axial leg rotation like markers are, which simplifies the analysis. If desired, the axial leg rotation can be determined by attaching a circular cyan marker on the band. The centroid of the marker relative to the band centroid gives an approximation of the leg rotation. In this study, the band could easily be located in the images and the leg axial rotation estimated in the frontal and the sagittal view showed the same trend. Further, the band-based results were found to be comparable to results where a marker was 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. We performed gait analysis before operation and at six months and at two years after TKA. On all three occasions we found significant differences between the two groups in the mean sagittal plane moments of the knee joint. The risk group walked with higher peak flexion moments than the stable group. The two groups were not discriminated by any clinical or radiological criteria or other gait characteristics. The relationship which we have found between gait with increased flexion moments and risk of tibial component loosening warrants further study as regards the aetiology of prosthetic loosening and possible methods of influencing its incidence.

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.

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.

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.

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. Four patients had bilateral total condylar knee arthroplasty. All patients were subjectively satisfied with their operations and had neither radiographic nor clinical signs of loosening. Considerable moments were found in the dorsal part of the medial tibiofemoral compartment. These moments increased with extension deficits and varus angles. The size of these moments were consistent with earlier findings of increased bone strengths in the same compartment as the biological answer to stress demands and earlier studies of moment after total condylar knee arthroplasty.

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. Pressure transducers in the shoe were used to measure the local pressure at the great toe, first and fifth metatarsal heads, and heel pad. Among studied procedures were Keller's operation for hallux rigidus and distal oblique osteotomy for hallux valgus. The study indicated that both methods can be used to assess mediolateral shifts of the centre of pressure on the foot due to the operation. A difference between operation results were that the moment arm of the ground reaction force with respect to the knee joint increased after distal oblique osteotomy, while it decreased after the Keller type operation. From a clinical point of view this can have the effect that the loads at the knee joint and especially at the medial condyle increases after the distal oblique osteotomy. The study showed that the described techniques have a potential for assessment of surgery for first metatarsophalangeal joint. Of special relevance is the possibility of studying the effect of foot pathologies on the loads at the knee joint.

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.

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. 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.

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.

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.

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.