Calibration and performance of a 3-dimensional television system for kinematic analysis.

A three-dimensional television system for kinematic analysis has been developed using television cameras connected to a digital computer. Reflective markers on the limbs of the subject are illuminated by stroboscopes, and show up as bright spots in the television image. A television/computer interface generates the two-dimensional coordinates of these spots, and stores them on disk for later analysis. A three-dimensional calibration procedure has been developed which requires an initial survey to be made of the measurement area, but thereafter takes only a few minutes to perform on a day-to-day basis. The television system has been in routine use for over a year, and it has proved rapid, reliable and easy to use, both for purely kinematic studies, and together with a pair of forceplates for combined kinetic/kinematic studies.

Dynamic back movement measured using a three-dimensional television system.

A technique for the measurement of rotational human back movements in three dimensions has been developed. The spatial coordinates of reflective markers on rigs attached to the back surface were calculated using a calibrated television/computer system. A mathematical analysis of the change in these coordinates, as subjects performed set manoeuvres, was developed to provide unique descriptions of the rotational movements in terms of clinical angles related to anatomical frames of reference. The technique produced angles of rotation with maximum errors about any axis of +/- 2 degrees, with a root mean square error of less than 1 degree. The analysis of back movements using surface markers was shown to be feasible from studies of six volunteers who demonstrated consistent patterns of movement which were similar to previously reported patterns of spinal movement measured radiographically.

Generation and attenuation of transient impulsive forces beneath the foot: a review.

At the end of the swing phase of gait, the moving foot generates a transient force, due to the exchange of momentum as it contacts the ground. This review article examines the transient, which is known as the heelstrike in walking and the footstrike in running. The resulting 'shock wave', which passes up the limb, may produce damage, leading to degenerative joint disease and a variety of other pathologies. Protection against transient forces is provided by limb positioning at initial contact, by the anatomical heel pad, by materials used in shoe construction and by the use of viscoelastic shoe inserts.

Impulsive forces during walking and their clinical implications.

During normal walking, repetitive impulsive forces are introduced into the musculo-skeletal system. At heelstrike, there is a sharp irregularity in the ground reaction force, known as the heelstrike transient. As a result of experimental evidence indicating possible correlations between impulse loading and joint degeneration, research interest in heelstrike transients has intensified. This paper outlines the nature of the heelstrike transient and the use of accelerometers and force platforms for skeletal transient investigation. Attention is given to two experiments that analysed the response of the human body to the impact forces experienced during walking. The possible causative links between excessive impulsive loading and the progression of two pathological conditions-osteoarthritis and low back pain, respectively-are discussed in detail.

Height of centre of body mass during osteoarthritic gait.

Early attempts to locate the position of the centre of mass of the body during walking involved the use of cinematography, followed by kinetic analysis of the forces and couples acting about three axes at the ground and centre of mass. These methods, requiring data on the individual body segments, are too lengthy and complex for routine clinical use. A method is described which estimates both the trajectory and the mean height of the centre of mass, using only dynamic data from a single walk across one pair of force plates. Relating a possible trajectory height to the measured force vectors gives a profile for the horizontal velocity. The correct height is determined by seeking the smooth profile corresponding to the known horizontal velocity obtained by integration. Results are presented for 42 osteoarthritic patients undergoing total hip replacement operations.

Test-retest reliability of the Chattecx Balance System in the patient with hemiplegia.

The purpose of this study was to determine the test-retest reliability of the Chattecx Balance System in the patient with hemiplegia. Twenty patients (14 male, 6 female; 14 right hemiplegia, 6 left; mean age 69.5, range 32-86 years) undergoing physical therapy, were tested on the Chattecx Balance System at the same time on 3 consecutive days. Subjects were tested on a static platform, and also using linear translation (anterior-posterior movements), and rotational angular motion about a mediolateral axis. Day 1 was used to allow the patient to become familiar with the testing equipment and the protocol. Data collected from days 2 and 3 were compared statistically using Intraclass Correlation Coefficient (ICC) formula 3,1. Comparison of the center of pressure in the mediolateral direction (COBX), the center of pressure in the anteroposterior direction (COBY), and dispersion index were analyzed for each of the three protocols. ICCs ranged from 0.58 to 0.92 for the static platform, 0.46 to 0.83 for the linear translations, and 0.62 to 0.89 for the angular rotations. Results using this testing protocol showed COBX to be highly reliable for the static and moderately reliable for linear and angular testing protocols. COBY was not reliable for any test condition. Dispersion was moderately reliable only for the static and angular testing protocols. From a clinical standpoint, measures that were found to be highly or moderately reliable may be useful for demonstrating the progress of patients with hemiplegia in their rehabilitation programs.

The effects of pelvic movement on lumbar lordosis in the standing position.

The purpose of this study was to investigate whether the maneuver of altering the angle of pelvic tilt when standing is effective in changing the angle of lumbar lordosis. The importance of the study was to establish a scientific basis for a common clinical assumption. Pelvic tilt and lumbar lordosis were measured during three conditions: with subjects in a normal standing posture, with subjects assuming a maximal anterior pelvic tilt posture, and with subject assuming a maximal posterior pelvic tilt posture. Measurements of pelvic tilt and lumbar lordosis were obtained using a television/computer system that obtained the three-dimensional coordinates of markers on the pelvis and spine at 20-msec intervals. Each measurement was made three times, and all were found to be reliable, with intraclass correlation coefficients (3,1) ranging from 0.78 to 0.95 (p < 0.001). Adopting a maximal anterior pelvic tilt changed the pelvic attitude relative to the horizontal by an average fo 11.4 degrees (p < 0.001) and increased the lumbar lordosis by an average of 10.8 degrees (p < 0.001). Adopting a maximal posterior pelvic tilt changed the pelvic attitude by an average of 8.7 degrees (p < 0.001) and decreased the lumbar lordosis by an average of 9.0 degrees (p < 0.001). The results of this study demonstrate that altering the pelvic tilt significantly changes the angle of lumbar lordosis. This lends support to the use of pelvic tilting exercises to increase or decrease the degree of lumbar lordosis, at least for the duration of the exercise.

The role of the quadriceps in controlling impulsive forces around heel strike.

The damaging effect of transient loads on joints has been observed in vitro and in vivo, and may be an aetiological factor in osteoarthrosis. The events around heel strike, when the velocity of the foot is brought rapidly to zero, may be a source of such loads in normal activity. By modifying the rate at which the limb descends to the ground, quadriceps action influences the magnitude of the heel strike transient. Experiments were carried out to analyse the occurrence of these transients, and a two-dimensional mathematical model of the knee joint and lower leg was used to calculate the forces developed at the knee in response to them. Paralysis of the quadriceps resulted in a large increase in the heel strike transient.

Caloric and exercise requirements of space flight: biostereometric results from skylab.

The biostereometric study of the Skylab astronauts used stereophotogrammetry to make accurate three-dimensional measurement of body form, from which regional and total body volumes were derived. Volume changes in the thighs and calves, over the course of the flight, showed a high correlation with inflight exercise on the bicycle ergometer, and suggested that an exercise level of 80-100 W-min/d/kg lean body mass would be necessary to prevent inflight muscle atrophy. The bicycle ergometer is thus a relatively inefficient means of preventing leg muscle atrophy. Inflight caloric intake showed a high correlation with the change in volume of the buttocks, the abdomen, and the body as a whole, and suggested that a caloric intake of 47-51 kcal/d/kg lean body mass would be necessary to prevent a change in body fat. Only one of the astronauts exceeded this range and gained body fat; the group as a whole showed a mean fat loss of 1.2 kg.

Bone mineral changes: the second manned Skylab mission.

The mineral content of the central os calcis, and distal radius and ulna was measured by the monoenergetic photon absorptiometric technique pre- and postflight on the the SL-3 crewmen. No significant changes were observed in the radius and ulna. Only the SPT showed a loss in calcaneal mineral which slowly returned to preflight levels by the 87th postflight day.

Biostereometric analysis of body form: the second manned Skylab mission.

Biostereometrics is the measurement and the mathematical description of the three-dimensional form of biological objects. Stereophotogrammetry was used to derive the Cartesian coordinates of numerous points on the body surface of the Skylab crewmen, both before and after flight, on all three Skylab missions. Mathematical analysis of the coordinate description allows the computation of surface area and volume of the body, as well as the volume of body segments, and the area and shape of cross sections. Loss of body weight in the first two Skylab flight crews was accompanied by comparable loss of volume and little change in density. Volume loss wad divided about equally between the trunk and the legs; however, because the volume of the legs is less than that of the trunk, this finding represented a greater proportional volume loss in the legs. Comparison of cross-sectional areas suggests that the calf undergoes shrinkage to a greater extent than does the thigh. The suggested interpretation of these changes is that, during flight, a reduction in bulk of many of the body tissues occurs. This reduction is probably caused, at least in part, by disuse atrophy of skeletal muscles in the absence of gravity. The atrophy is lessened to some extent by the in-flight exercise program. The stereoscopic images of the crewmen from a permanent archival record of body form on which more detailed measurements may be made in the future.

Mineral and nitrogen balance study observations: the second manned Skylab mission.

A metabolic study of the effects of space flight on various chemical elements, particularly those with special revelance to the musculoskeletal system, was carried out on the three astronauts of the SL-3 mission for 21 d preflight, during the 60 d flight phase, and for 17 d postflight. The study required of the cooperating crewmen quite constant dietary intake, continuous 24-hour urine collections and total fecal collections. Urinary calcium was significantly increased during flight in all three crewmen with man-to-man variation in pattern and amount; the degree of calcium loss was, in general, similar to that in the prior study of the 28-d Skylab flight (SL-2). The similarity to bedrest immobilization in the pattern of urinary calcium increases and of total calcium shifts suggested that calcium losses would continue for a very long time. Significant losses of nitrogen and phosphorus occurred that were associated with observed reduction in muscle tissue. Both mineral and muscle losses occurred despite vigorous exercise regimens during flight. It was concluded that these studies give warning that capable musculoskeletal function may be significantly impaired during prolonged space flights lasting 1.5 to 3 years unless protective measures are developed.

Performance of three walking orthoses for the paralysed: a case study using gait analysis.

Three types of walking orthosis are currently available to enable paralysed people to achieve reciprocal gait. This case study assesses the performance in walking of one patient who was proficient in the use of all three devices. The results of a biomechanical analysis are presented in which comparisons are made between the orthoses in terms of general gait parameters and movement of the lower limbs and pelvis.

Functional biomechanical assessment of the Oxford Meniscal Knee.

The Oxford Meniscal Knee is an unconstrained surface arthroplasty that has given good clinical results. The biomechanics of knee function during walking in patients with this arthroplasty were examined using a three-dimensional television/force platform/computer system. Two groups of patients were studied: a retrospective group of 13 patients with single joint disease and a prospective group of 13 knee arthroplasties in 10 patients with mixed joint pathology. General gait parameters (cadence, velocity, and stride length) were near normal in the retrospective group and showed a useful improvement in the prospective group. In the sagittal plane the knee showed some limitation of extension and a tendency toward an abnormal flexion-extension moment pattern. In the coronal plane, the knee arthroplasty generally corrected errors of alignment, but about one-third of the patients had adduction/abduction moments outside the normal range. The clinical results of the arthroplasty are thus better than the biomechanical results, an observation common to all of the knee arthroplasties that have been studied using comparable methods.

Influence of gait parameters on the loading of the lower limb.

The ground reaction force which acts on the foot during normal walking consists of the sum of two components: the support of the weight of the body and the acceleration of the body. The relationships between the initial loading rate of the lower limb (ignoring the contribution of the heelstrike transient) and the general gait parameters--cadence, stride length, and velocity--have been examined. Plots of the resultant ground reaction force were used to calculate the loading rate of the limb. A sample of 13 normal male subjects, aged from 18 to 63 years, walked at five different self-selected speeds. Velocity showed the highest correlation with loading rate (r = 0.95) and stride length the lowest (r = 0.85). The relationship between cadence and loading rate was non-linear.

Initiation of gait in normal subjects: a preliminary study.

The initiation of gait, from standing at rest to the toe-off of the second leg, was analysed in 15 normal subjects wearing shoes. Thirty-two parameters were identified and measured. The pattern of forces, angular movement and timing in this period are described and analysed. Two groups, one of 8 female subjects and another of 7 males, were compared statistically. Sex-related differences were found in the mediolateral and vertical forces as well as in which leg was the first to leave the ground. The values of all the parameters are given, as part of a database to be used in the future for diagnostic and assessment purposes in orthopaedics.

Results of treatment of dermatitis herpetiformis with a gluten-free diet after one year.

Twenty-one patients with dermatitis herpetiformis initially controlled by dapsone or sulphonamides have been treated with a gluten-free diet and reassessed at intervals for up to 15 months (mean 11.9 months). According to routine histological and dissecting microscope criteria the small-bowel lesion improved in 10, but when mean epithelial cell height was used as a measure 15 patients improved. Five of the patients with diarrhoea improved after withdrawing gluten from the diet but none reverted to completely normal bowel habit. The tests for malabsorption showed little improvement in the treatment period. Twelve patients needed less dapsone to control their skin complaint, the mean dose falling from 144 mg. to a mean of 70 mg. per day; of these three stopped using this drug altogether.

Movements of the lumbar spine measured by three-dimensional X-ray analysis.

Techniques for the calculation from biplanar radiographs of the three-dimensional coordinates of anatomical landmarks on human lumbar vertebrae, and of the movements in three dimensions of the vertebrae between different positions of the spine are presented. The calculation of three-dimensional coordinates uses a calibration procedure based on direct linear transformation. Coordinate systems are used to define the orientations of each vertebra, and movements are derived from coordinate transformations between neighbouring vertebrae. The root mean square error in determining the absolute locations of anatomical landmarks was found to be less than 1 mm. For the movements of one vertebra relative to its neighbour the root mean square errors for translations were less than 2 mm and for rotations were less than 1.5 degrees. The system has been used to assess patients after spinal fusions and is currently being used in the diagnosis and assessment of patients with specific pathologies.

Influence of walking speed on gait parameters.

Modern three-dimensional gait analysis systems give information on joint angles and moments in the sagittal and coronal planes, for which normal ranges may not be readily available in the literature. Since patients with joint disease tend to walk slowly and with a short stride, it is essential that normal ranges for gait parameters should be defined with reference to speed of walking. This we have done using a population of 10 normal male subjects aged from 18 to 63 years, walking at speeds which range from very slow to very fast. The ranges of knee angle and moment are given, together with the changes in these parameters with walking speed. Peak knee flexion moment is strongly related to walking speed, whereas coronal plane knee angle is virtually independent of it. The stride length is probably the best basis for deciding the normal range for a particular measurement.

A comparative trial of two walking systems for paralysed people.

A trial has been performed to compare two designs of reciprocal walking orthosis for paralysed people--the hip guidance orthosis (HGO) from Oswestry, England, and the reciprocating gait orthosis (RGO) from New Orleans, USA. Eighteen male and 4 female paraplegic subjects used each orthosis for 4 months, in a crossover study. All aspects of the provision and use of the devices were monitored, and a variety of assessments were made. Fifteen subjects were able to use both orthoses, 5 were unable to use either and 2 succeeded with the HGO but not the RGO. At the end of the trial 12 subjects chose to keep the RGO, 4 the HGO, and 6 kept neither. Those choosing the RGO liked its appearance; those choosing the HGO liked the speed of donning and doffing. The RGO was about 50% more expensive to supply than the HGO.