Long-term follow-up of Van Nes rotationplasty in patients with congenital proximal focal femoral deficiency

Van Nes rotationplasty may be used for patients with congenital proximal focal femoral deficiency (PFFD). The lower limb is rotated to use the ankle and foot as a functional knee joint within a prosthesis. A small series of cases was investigated to determine the long-term outcome. At a mean of 21.5 years (11 to 45) after their rotationplasty, a total of 12 prosthetic patients completed the Short-Form (SF)-36, Faces Pain Scale-Revised, Harris hip score, Oswestry back pain score and Prosthetic Evaluation Questionnaires, as did 12 age- and gender-matched normal control participants. A physical examination and gait analysis, computerised dynamic posturography (CDP), and timed 'Up & Go' testing was also completed. Wilcoxon Signed rank test was used to compare each PFFD patient with a matched control participant with false discovery rate of 5%. There were no differences between the groups in overall health and well-being on the SF-36. Significant differences were seen in gait parameters in the PFFD group. Using CDP, the PFFD group had reduced symmetry in stance, and reduced end point and maximum excursions. Patients who had undergone Van Nes rotationplasty had a high level of function and quality of life at long-term follow-up, but presented with significant differences in gait and posture compared with the control group.

Mechanical characterization of fourth generation composite humerus

Mechanical data on upper extremity surrogate bones, supporting use as biomechanical tools, is limited. The objective of this study was to characterize the structural behaviour of the fourth-generation composite humerus under simulated physiologic bending, specifically, stiffness, rigidity, and mid-diaphysial surface strains. Three humeri were tested in four-point bending, in anatomically defined anteroposterior (AP) and mediolateral (ML) planes. Stiffness and rigidity were derived using load–displacement data. Principal strains were determined at the anterior, posterior, medial, and lateral surfaces in the humeral mid-diaphysial transverse plane of one specimen using stacked rosettes. Linear structural behaviour was observed within the test range. Average stiffness and rigidity were greater in the ML (918 ± 18 N/mm; 98.4 ± 1.9 Nm2) than the AP plane (833 ± 16 N/mm; 89.3 ± 1.6 Nm2), with little inter-specimen variability. The ML/AP rigidity ratio was 1.1. Surface principal strains were similar at the anterior (5.41 µε/N) and posterior (5.43 µε/N) gauges for AP bending, and comparatively less for ML bending, i.e. 5.1 and 4.5 µε/N, at the medial and lateral gauges, respectively. This study provides novel strain and stiffness data for the fourth-generation composite humerus and also adds to published construct rigidity data. The presented results support the use of this composite bone as a tool for modelling and experimentation.

Using a bi-planar postural stability model to assess children with scoliosis

This study examines the postural stability of children with idiopathic scoliosis, using experimental data and a model of sway that includes mediolateral (ML) and anterioposterial (AP) components. The experimental data includes center of pressure (COP) measurements calculated from data acquired using two Advanced Medical Technology, Inc. (AMTI) force plates. Sway metrics are computed and compared with the model simulation, which successfully reproduced the clinical data from 16 children with scoliosis and 20 typically-developing children. This study is part of the first phase of a multi-year study designed to systematically assess whether fusing the spine to L4 in children with scoliosis has a significant impact on physical function and quality of life.

Analysis of postural stability following posterior spinal fusion in adolescents with idiopathic scoliosis

This study uses experimental data acquired from adolescents with idiopathic scoliosis to assess their postural control during quiet standing before and after posterior spinal fusion. Statistically significant differences were seen when comparing the pre- and post-surgical measures of balance calculated from data for three different test conditions.

Application of a bi-planar postural stability model in children with cerebral palsy

This study presents initial results from a bi-planar model used to investigate the neurological factors affecting balance deficits in children with diplegic cerebral palsy (CP). The model uses an inverted pendulum to describe sway in both the anteroposterior (AP) and mediolateral (ML) planes. The study presents Center of Pressure (COP) data from 17 children diagnosed with spastic diplegic CP using two standard AMTI force plates. Sway metrics in the time and frequency domains in the AP and ML planes were calculated and compared to simulations produced by the model. The proposed bi-planar model successfully reproduced sway signals acquired from experimental (clinical) data.

A dynamic model of the upper extremities for quantitative assessment of Lofstrand crutch-assisted gait

Appropriate models for quantitative evaluation of upper extremity dynamics in children with myelomeningocele are limited. Therefore, a three-dimensional (3D) biomechanical model of the upper extremities was developed for quantification during Lofstrand crutch-assisted gait in children with myelomeningocele. The model accurately tracks the joint angles of the trunk, shoulders, elbows, wrists, and crutches. Lofstrand crutches are instrumented with six-axis load cells to obtain force and moment components. The model is applied while performing crutch-assisted ambulatory patterns (alternate gait and swing-through gait). Analysis indicates that the model is suitable for quantifying upper extremity motion during crutch-assisted gait. This model has been designed for dynamic assessment of ambulatory patterns (upper and lower extremities) that present with pediatric myelomeningocele. It is hoped that the study findings will prove useful through advances in treatment monitoring, crutch prescription and therapeutic planning.

Quantification of reaching during stroke rehabilitation using unique upper extremity kinematic model

Quantification of rehabilitation progress is necessary for accurately assessing clinical treatments. A three-dimensional (3D) biomechanical model of the upper extremity was developed for quantification of stroke rehabilitation. The model was designed to accurately track the 3D orientation of the trunk, shoulder, elbow and wrist. This study explains the application of the upper extremity model. Strict validation of the model confirmed the system's accuracy and resolution. The model was applied to eight hemiparetic stroke patients with spasticity, while completing a set of reaching tasks. The model successfully detected statistical differences in elbow range of motion and angular velocity between the nonparetic (unaffected) and paretic (affected) arms. Both simple and complex biomechanical indices for assessment were developed. This model may aid in the assessment and planning of stroke rehabilitation, and help to decrease recovery time.

Biomechanics of cranial dynamics during daily living activities

Motion tracking capabilities of a head-mounted accelerometer apparatus were investigated in conjunction with three-dimensional motion analysis techniques during activities of daily living. In this report, measures between systems are compared for jogging, toe-touching, and start-from-rest tasks. Good fidelity was found for most measures between systems; some phase shifts and amplitude discrepancies were observed, and attributed to transducer orientation and system asynchrony. This preliminary work demonstrates the potential benefits of hybrid motion analysis systems.

Kinematic analysis of upper extremity joint motion in children using posterior walkers

This study applies an upper extremity model to analyze motion in 25 children with cerebral palsy using posterior walkers. The study indicates that throughout a gait cycle, the shoulders and wrist are in extension and the elbows are flexed. It also reveals that the elbows are the most asymmetrical joint of the upper extremities during walker-assisted ambulation.

Stress analysis of unilateral cleft palate using a three dimensional finite element model of pediatric subject-specific maxilla

For children with cleft palate, oral function is impaired. The hypothesis is that the stress and strain distribution within the affected maxilla with a cleft during functional tasks such as biting and chewing is abnormal and can significantly affect bone development in the growing child. To test this hypothesis, a three-dimensional finite element model of a pediatric subject-specific maxilla with and without unilateral cleft palate was established based upon pediatric subject-specific bony geometry. The stress and strain distribution of the maxillary alveolar region subjected to typical functional loads was analyzed. The preliminary results revealed that both Von Mises stress and maximum principle stress as well as principle strain distribution were unevenly distributed between the hemi-maxillae.

Biomechanical implications of the negative heel rocker sole shoe: gait kinematics and kinetics

Rocker sole shoes are commonly prescribed to diabetic patients with insensate feet. Recent passage of the therapeutic shoe bill has drawn an increased focus to prescription rehabilitative footwear. The purpose of this work is to investigate the dynamics of lower extremity joints (hip, knee and ankle) with the application of a negative heel rocker sole shoe under controlled lab conditions. Forty normal adults volunteered for gait evaluations using controlled baseline and prescription negative heel rocker sole shoes. Three-dimensional motion analysis techniques were used to acquire kinematic and kinetic data using a six-camera Vicon 370 motion system and two AMTI force plates. No significant change in walking speed or stride length was seen with the negative heel rocker shoe, although cadence was increased. The most significant kinematic changes with the application of the negative heel shoe occurred at the ankle in the sagittal plane with increased plantarflexion at terminal stance. Significant hip and knee changes were also noted with increased mid-stance hip extension and knee flexion. The most significant kinetic effects were seen in the transverse plane followed by changes in the sagittal and coronal planes. Changes in power were mostly noted in the sagittal plane. Other statistically significant changes in gait kinematics and kinetics were observed, although the magnitudes and durations were limited and as a result were not considered clinically significant. The study results indicated the negative heel rocker shoe significantly altered proximal joint metrics (hip and knee). The most significant distal joint alterations were seen in sagittal plane ankle kinetics. These kinematic and kinetic changes, along with previously studied effects of pressure relief at the metatarsal heads, should aid medical professionals in prescribing prophylactic footwear.

Combined sagittal and coronal plane postural stability model

We present a preliminary study of combined anterior posterior (AP) and medial lateral (ML) sway assuming a classic inverted pendulum with included subtalar movement. Based on a feedback control posture model in the sagittal plane as presented by Maurer and Peterka, we have investigated parameters needed to model ML sway components. Center of pressure (COP) data was collected from a population of 8 normal adults (age 18 to 30 years) using a dual AMTI force plate system. Fourteen different sway metrics were calculated. The collected data was successfully compared to numerous simulations of the model where model parameters were varied and the goal was to reproduce both AP and ML components.

Development of a computer assisted craniofacial surgery planning system

Based upon the idea that both facial appearance and functional outcomes of the craniofacial surgery need to be predicted in the pre-surgery planning stage, a CACSP system has been established. In this system, the input is in vivo CT/MRI scan data of patient with craniofacial deformity, anatomical restoration is simulated using the medical visualization packages ANALYZE, and the finite element analysis of the masticatory system has been integrated to predict the functional improvement such as bite force alteration. Preliminary studies in this laboratory have revealed the potential of this system.

Finite element (FE) modeling of the mandible: from geometric model to tetrahedral volumetric mesh

This paper presents our experience in using FE modeling of clinically relevant cases specifically in mandibular surgery. A semi-automatic procedure integrated with a group of Virtual Basic-based codes has been developed to clean the geometric models. Consequently, the time required for generate the tetrahedral volumetric mesh of mandible from patient-specific CT data has been reduced to less than 40 hours. Pre- and post-operation FE meshes are shown to be consistent and can be used for further modeling and analysis.

Surgical rehabilitation of the planovalgus foot in cerebral palsy

The objectives of this study were to quantitatively determine the effects of subtalar arthrodesis on the planovalgus foot using three-dimensional (3-D) gait analysis and plantar pressure measurements. Twelve children and adolescents with planovalgus foot deformity secondary to spastic cerebral palsy participated in this outcome study. The pediatric population were evaluated preoperatively and following subtalar fusion. Seventeen feet were operated for the correction of the planovalgus foot deformity. A Holter-type microprocessor-based portable in-shoe data acquisition system was used in this study to collect the multistep dynamic plantar pressure history, while a five-camera Vicon-based gait analysis system was used to track the lower extremity joint kinematics. The results obtained from the plantar pressure measurement showed significant increases in mean peak vertical plantar pressures postoperatively at the lateral midfoot and lateral metatarsal heads. Mean contact durations and mean pressure-time integrals were also significantly increased at these plantar locations following foot surgery. This redistribution in pressure metrics suggests the formation of new lateral plantar weight bearing areas. The 3-D gait analysis system, using standardized lower extremity measurements, was unable to reveal any significant changes in joint kinematics, particularly at the foot and ankle where the surgery was performed. This suggests the need for a more refined system to track the complex motion of the pediatric foot and ankle during gait.

Walker-assisted gait in rehabilitation: a study of biomechanics and instrumentation

While walkers are commonly prescribed to improve patient stability and ambulatory ability, quantitative study of the biomechanical and functional requirements for effective walker use is limited. To date no one has addressed the changes in upper extremity kinetics that occur with the use of a standard walker, which was the objective of this study. A strain gauge-based walker instrumentation system was developed for the six degree-of-freedom measurement of resultant subject hand loads. The walker dynamometer was integrated with an upper extremity biomechanical model. Preliminary system data were collected for seven healthy, right-handed young adults following informed consent. Bilateral upper extremity kinematic data were acquired with a six camera Vicon motion analysis system using a Micro-VAX workstation. Internal joint moments at the wrist, elbow, and shoulder were determined in the three clinical planes using the inverse dynamics method. The walker dynamometer system allowed characterization of upper extremity loading demands. Significantly differing upper extremity loading patterns were identified for three walker usage methods. Complete description of upper extremity kinetics and kinematics during walker-assisted gait may provide insight into walker design parameters and rehabilitative strategies.

Variability in three-dimensional measurements of back contour with raster stereography in normal subjects

Forty normal children with a mean age of 9.1 years were investigated by using a Quantec Spinal Image System (QSIS). The QSIS uses computerized raster stereography technology to acquire three-dimensional measurements of back contour. Within a 95-percentile confidence interval (a) coronal-plane QSIS angles ranged from 0.05 to 2.36 degrees; (b) transverse-plane QSIS angles ranged from 0.03 to 1.96 degrees; and (c) sagittal-plane QSIS angles ranged from 36.8 to 44.8 degrees. Trunk-alignment deviation ranged from 3.51 to 7.45 mm within a 95-percentile confidence interval. An intraobserver standard deviation of +/-4.2 degrees was noted across all angular metrics. Normal ranges of QSIS-determined values for a population of 40 children without clinical evidence of pathology are reported.

Hindfoot coronal alignment: a modified radiographic method

Accurate clinical evaluation of the alignment of the calcaneus relative to the tibia in the coronal plane is essential in the evaluation and treatment of hindfoot pathologic condition. Previously described radiographic views of the foot and ankle do not demonstrate the true coronal alignment of the calcaneus relative to the tibia. Some of these views impose on the patient an unnatural posture that itself changes hindfoot alignment, whereas other methods distort the coronal alignment by the angle of the x-ray beam. Our purpose was to develop a modified radiographic view and measurement method for determining an angular measurement of hindfoot coronal alignment based on a cadaver study of the radiographic characteristics of the calcaneus and motion analysis of standing subjects. The view was obtained by having the subject stand on a piece of cardboard to create a foot template. The template was then positioned so that each foot was x-rayed perpendicular to the cassette while still maintaining the natural base of support. A method using multiple ellipses was developed to determine more accurately the coronal axis of the posterior calcaneus. A study using cadavers was performed in which radio-opaque markers were placed on multiple bony landmarks on the calcaneus. The tibia was held fixed in a vertical position, and the foot was x-rayed using the above techniques in different degrees of rotation without changing the relation of the calcaneus to the tibia. The radiographs of the modified Cobey and our view were examined to verify which markers were visible at different angles of rotation and how the hindfoot alignment measurements changed with foot rotation. To define further the differences between the views, an analysis of postural stability was conducted while the subjects were standing with the feet in the positions for imaging both the Buck modification of the Cobey view and our hindfoot alignment view. The combined results of the cadaver, radiographic measurement, and postural stability segments of the study reveal that this coronal hindfoot alignment view and measurement method is reproducible, more closely measures "true" coronal hindfoot alignment, and is more clinically applicable because the alignment is measured while the patient is standing with a normal angle and base of stance. The modified radiographic measurement method relies on posterior calcaneal anatomic landmarks, is less affected by rotation of the foot and ankle, and is reproducible between observers.

Instantaneous postural stability characterization using time-frequency analysis

Postural stability assessment is critical to a more accurate understanding of sway and balance control. The center of pressure (COP) metric has been shown to be a suitable output measure for time and frequency analysis. However, the center of pressure is a non-stationary signal. Standard time and frequency analysis methods may not be adequate for monitoring the dynamic changes in the center of pressure signal. In this study a time-frequency method, based on data-adaptive evolutionary spectral estimation, is applied to monitor the dynamic changes of the center of pressure in a non-stationary environment. Metrics including the instantaneous mean frequency (IMF), instantaneous spectral bandwidth (ISB), and instantaneous average power (IAP) are analyzed to characterize the center of pressure signal in both the anterior-posterior (AP) and the medial-lateral (ML) planes. Within the confines of this study, the IMF was found to be inversely proportional to IAP. The inverse proportionality factors were calculated in both eyes-open and eyes-closed trials during upright quiet standing. These findings suggest that the time-frequency analysis provides instantaneous metrics which describe the amplitude changes and frequency shift of the center of pressure under a variety of environmental conditions, thus providing a more reliable quantification of postural control.

Effects of surface electrode size on computer simulated surface motor unit potentials

Surface myoelectric signals are recorded in motor nerve conduction, fatigue and kinesiologic studies using discrete electrodes. Single site recordings have limited means to reduce cross-talk and to enhance timing and quantification of relative muscular activity. These limitations are compounded by the effects of the electrode size. A grid electrode would reduce some of these limitations. However, an optimum grid electrode requires detail examination of the effects of the size of individual electrodes and the interelectrode distance. The purpose of this study is to investigate the temporal and spatial effects of the electrode size on surface motor unit potentials (SMUP). Muscle fiber action potentials and surface electrodes are simulated by computer models. Peak to peak amplitude, the mean frequency of SMUP, and the muscle conduction velocity were calculated as functions of the size of the electrode. The random variations of these parameters due to systematic errors are also simulated and investigated.

Gait analysis in rehabilitation medicine: a brief report

Gait analysis can be a powerful tool for rehabilitation research and clinical practice. However, there has been little coordinated effort to set goals for the application of gait analysis in rehabilitation. Therefore, a priority setting process was engaged to obtain the opinions of a diverse pool of experts related to human motion analysis. The primary goal of this process was to develop priorities for future research, development, and standardization in gait analysis. A multistep approach was used that included expert testimony, group discussions, individually developed priorities, and a ranking process. Several important priorities emerged from this activity. The highest priority was assigned to research on the efficacy, outcomes, and cost-effectiveness of gait analysis.

A noninvasive, three-dimensional spinal motion analysis method

STUDY DESIGN

A three-dimensional, noninvasive motion analysis method was developed by monitoring the orientation of the principal axes of each vertebra.

OBJECTIVES

To develop a method of performing three-dimensional, noninvasive motion analysis of the spine using computed tomography data.

SUMMARY OF BACKGROUND DATA

The concept of using principal axes of the moment of inertia tensor to measure the orientation and position of a rigid body has been applied to the wrist and subtalar joints, but has not yet been applied to the spine.

METHODS

Scans were taken of two isolated vertebrae in various known positions. Centroids, area, moments, and product of inertia of each scan were determined using a commercial program. Custom software combined data using the parallel axis theorem to give three-dimensional data for each vertebra. Changes in the centroid and principal axes were used to calculate translation and rotation, respectively.

RESULTS

The system accuracy was within 1.0 degree in rotation and 1.0 mm in translation. Some errors occurred in minor motions when a smaller number of scans were used. System resolution was 0.43 mm.

CONCLUSIONS

A system has been developed capable of calculating three-dimensional spinal motion based on measurements of a series of computed tomography images. The system has an accuracy similar to that of current motion analysis methods, but future studies will be necessary to apply this system in vivo.

A Holter-type, microprocessor-based, rehabilitation instrument for acquisition and storage of plantar pressure data

A Holter-type, microprocessor-based, portable, in-shoe, plantar pressure data acquisition system has been developed. The system allows continuous recording of pressure data between the sole of the foot and the shoe during the performance of daily living activities. Fourteen conductive polymer sensors acquire the plantar pressure history, which is then stored in the system memory. Pressures are sampled at a rate of 40 Hz from each of the 14 sensors for up to 8 hrs. The extended recording and processing capacity of the system developed in this study allows quantitative analysis of cumulative plantar pressure and temporal gait data necessary for characterization of event-related alterations in plantar pressures. The alterations that could be examined with the system include rehabilitative, therapeutic, surgical, and nonsurgical treatment. The system is fully portable and does not disrupt the natural gait pattern of the subject during ambulation. Peak plantar pressures, pressure-time integrals, and contact durations are determined for each of the insole sensors.

A comparison study of plantar foot pressure in a standardized shoe, total contact cast, and prefabricated pneumatic walking brace

Total contact casting is the current recommended treatment for Wagner Stage 1 and 2 neuropathic plantar ulcers. The rationale for this treatment includes the equalization of plantar foot pressures and generalized unweighting of the foot through a total contact fit at the calf. Total contact casting requires meticulous technique and multiple cast applications to avoid complications before ulcer healing. An alternative to total contact casting is the use of a prefabricated brace designed to maintain a total contact fit. This study compares plantar foot pressure metrics in a standardized shoe (SS), total contact cast (TCC), and prefabricated pneumatic walking brace (PPWB). Five plantar foot sensors (Interlink Electronics, Santa Barbara, CA) were placed at the first, third, and fifth metatarsal heads, fifth metatarsal base, and midplantar heel of 10 healthy male subjects. Each subject walked at a constant speed over a distance of 280 meters in a SS, PPWB, and TCC. A custom-made portable microprocessor-based system, with demonstrated accuracy and reliability, was used to acquire the data. No significant differences in peak pressure or contact duration were found between the initial and repeat SS trials (P > 0.05). Peak pressures were reduced in the PPWB as compared to the SS for all sensor locations (P < 0.05). Similarly, peak pressures were reduced in the TCC compared to the SS for all sensor locations (P < 0.05) with the exception of the fifth metatarsal base (P = 0.45). Our results are summarized as follows: (1) the methods used in the current study were found to be reliable through a test-retest analysis; (2) the PPWB decreased peak plantar foot pressures to an equal or greater degree than the TCC in all tested locations of the forefoot, midfoot, and hindfoot; (3) compared to a SS, contact durations were increased in both the TCC and PPWB for most sensor locations; and (4) the relationship of peak pressure over time, the pressure-time integral, is lower in the brace compared to the shoe at the majority of sensor locations. The values are not significantly different between the cast and shoe. These findings suggest an unweighting of the plantar foot and equalization of plantar foot pressures with both the PPWB and TCC. Based on these findings, the PPWB may be useful in the treatment of neuropathic plantar ulcerations of the foot.

Evaluation of a rehabilitative pedorthic: plantar pressure alterations with scaphoid pad application

Scaphoid or longitudinal arch pads are frequently prescribed pedorthics for foot and ankle rehabilitation. These pedorthics are reported to be effective in mechanically supporting the medial longitudinal arch while reducing plantar and medial soft tissue strain. The objective of this study was to measure alterations in ambulatory plantar pressure metrics in a group of adults secondary to scaphoid pad application. The biomechanical rationale of this study was that the geometry of foot contact would be altered secondary to foot inversion. Ten adult male subjects with biomechanically normal feet were evaluated during multiple trials. A Holter type microprocessor-based portable in-shoe plantar pressure data acquisition system was used to record the dynamic data. Pressures were recorded from eight discrete plantar locations at the hindfoot, midfoot, and forefoot regions of the insole. Statistically significant (p < or = 0.05) increases in peak pressures were seen laterally with scaphoid pad application, while significant decreases in peak pressures with pad usage occurred at the hallux and the calcaneal region of the foot. At the medial longitudinal arch, peak pressures increased from near 0 to 115.3 kPa, contact durations increased from near 0 to 438 ms, and pressure-time integrals increased from near 0 to 33.4 kPa.s.

An optoelectric plantar "shear" sensing transducer: design, validation, and preliminary subject tests

A prototype miniature plantar shear sensing transducer was developed, characterized, and tested in this study. Electro-optical components were chosen for the design because of the fast response time, low cost, small size, low power requirements, and adaptability to this application. The optoelectric circuit employed a 660 nm wavelength light source and photodiode solar cell. Signal amplification and sensitivity were adjusted to provide an output voltage proportional to light power. The sensor shell was designed to encapsulate the electro-optical sensing components while providing mechanical resistance to shear through a spring mechanism. A naval bronze was chosen for the shell due to its strength and nonreflective characteristics (alloy of copper and tin). Static and dynamic characteristics of the shear sensor were determined through a series of calibration tests. Mechanical crosstalk sensitivity ranged from 14.34 to 30.51 mV/N. This represented 1% full-scale/Newton sensitivity. Nonlinearity averaged 5.6% in the forward direction and 7.6% in the reverse direction. Overall sensor output hysteresis was 1.1 +/- 3.1% while the natural frequency of the sensor to an input shear transient was approximately 5 Hz. Temperature sensitivity was -7.0 mV/degree C or 3.5% full-scale/degree C. Testing of five adult subjects revealed peak anterior-posterior shear ranging from 6.7 kPa (posterior heel) to 51.4 kPa (great toe) and medial-lateral shear ranging from 5.4 kPa (great toe) to 43.5 kPa (first metatarsal head). Stress-time integral values ranged from 0.78 kPa-sec (posterior shear at the posterior heel) to 37.3 kPa-sec (medial shear at the posterior heel). Contact durations ranged from 0.28 sec (posterior shear at the posterior heel) to 1.25 sec (medial shear at the posterior heel). Further application of the sensor for plantar shear characterization in able-bodied subjects and those with pathology is suggested.

Investigation of spectral content from discrete plantar areas during adult gait: an expansion of rehabilitation technology

Evaluation of foot contact frequency components with the use of a standard force plate has been reported to be helpful in the clinical assessment of degenerative joint disease. Spectral analysis has also been used as a tool for the evaluation of prosthetic and orthotic designs. In this paper, we examine and employ a new method for determining spectral characteristics of discrete plantar foot surface areas. This method is used to characterize spectral frequency content of foot strike at discrete plantar locations in ten normal controls. Spectral data obtained from a standard force plate are also presented and compared to reports in the literature. Measurements at six discrete points under the foot were made with a custom-manufactured strain gage-based force dosimeter. In addition, measurements of ground reaction forces in the sagittal, coronal, and transverse planes were made using a high resonant frequency force plate during barefoot and shod walks for ten adult male control subjects. Spectral frequency components of all forces measured were determined through Fourier analysis. The hypothesis of the study was that discrete plantar frequencies would be essentially similar to those reported in earlier studies of foot contact with a ground reaction force plate. While Fourier transform of time domain force plate data revealed frequency contents that were contained primarily below 10 Hz, as has been previously reported, higher frequency components associated with impulsive loading at heel strike were also observed (75 Hz for barefoot walk and 60 Hz for shod). The anterior-posterior (AP) frequency spectrum of barefoot walking contained higher amplitude components than did shod walking, though both signals contained dominant frequencies of about 1 Hz. Medial-lateral (ML) frequency analyses were similar for both walking conditions with dominant components of about 4 Hz noted. Broader frequency spectrums were seen in the discrete force dosimeter data. Components were contained mostly below 12 Hz with some higher frequency content also noted. Discrete foot force dosimeter and force plate AP and ML spectral data during ambulation have not been previously reported.

"Guided" intramuscular fine wire electrode placement. A new technique

This report describes a new technique for placing intramuscular fine wire electrodes into muscles for kinesiologic electromyographic (EMG) studies. Currently, a pair of fine wire electrodes (one active, one reference) within a hypodermic needle is inserted into the selected muscle. The needle is then withdrawn, leaving the two fine wires positioned within the muscle. Electrical stimulation of the muscle through these fine wire electrodes confirms their correct placement. However, if positioning is incorrect, additional pairs of wires are inserted within needles until correct placement is achieved. Our "guided" method combines this "blind" technique with diagnostic needle EMG techniques. Using a conventional EMG machine and selective activation of the desired muscle, the electromyographer inserts the hypodermic needle while monitoring the muscle's electrical signal through the advancing fine wire electrodes. This signal is used to "guide" the needle into the proper muscle. Once correct positioning of the wires is confirmed by the EMG signal, the needle is removed. With this techniques additional needle insertions are avoided, electrical stimulation is seldom needed, and rarely studied muscles are accessed as easily as commonly studied ones. We have used this technique with pediatric and adult patients as well as in kinesiologic EMG research and have found it to be well tolerated and reliable.

A Holter-type microprocessor-based rehabilitation instrument for acquisition and storage of plantar pressure data in children with cerebral palsy

A multichannel, portable data acquisition system has been developed to measure discrete plantar pressures in the rehabilitation of children who have cerebral palsy and planovalgus foot deformity. The microprocessor-based system is designed to be lightweight (350 g with batteries) and portable (no umbilicus) in order to minimize encumbrances to gait patterns. It provides an improved method for obtaining accurate and reliable data during extended recording and rehabilitative periods that is not available from commercial systems. Twelve conductive polymer force (pressure) sensors are used to acquire pressure data, which are then stored in the system memory. Plantar pressures are sampled at a rate of 40 Hz from each of the 12 sensors for up to 2 h. The system consists of 16 analog amplifiers, a 12 b sampling analog-to-digital converter, an 8 b Dallas semiconductor microprocessor (DS5001FP-16, Dallas, TX), 4 MB of pseudo static RAM, and serial and parallel I/O interfaces. The interfaces are used to upload data into a PC for further processing, analysis, and display. During subject testing, sensors are located at predetermined anatomic areas under the calcaneus, medial and lateral midfoot, medial and lateral metatarsal heads, and hallux. Foot pressure data has been acquired from two pediatric subjects during multiple walking trials to illustrate system application in the normal and planovalgus foot. The system is considered to be appropriate for further clinical application and for characterization of event related alterations including rehabilitative, therapeutic, surgical, and nonsurgical treatment.

A system for the analysis of foot and ankle kinematics during gait

A five-camera Vicon (Oxford Metrics, Oxford, England) motion analysis system was used to acquire foot and ankle motion data. Static resolution and accuracy were computed as 0.86 +/- 0.13 mm and 98.9%, while dynamic resolution and accuracy were 0.1 +/- 0.89 and 99.4% (sagittal plane). Spectral analysis revealed high frequency noise and the need for a filter (6 Hz Butterworth low-pass) as used in similar clinical situations. A four-segment rigid body model of the foot and ankle was developed. The four rigid body foot model segments were 1) tibia and fibula, 2) calcaneus, talus, and navicular, 3) cuneiforms, cuboid, and metatarsals, and 4) hallux. The Euler method for describing relative foot and ankle segment orientation was utilized in order to maintain accuracy and ease of clinical application. Kinematic data from a single test subject are presented.

Walking cadence effect on plantar pressures

OBJECTIVE

Prior studies have examined the effect of cadence on ground reaction forces by use of a force plate. Force plate studies generally analyze isolated steps and do not provide insight into ongoing step-to-step variations or in-shoe plantar pressures. The objective of this study was to evaluate the effect of walking cadences on in-shoe plantar pressures over extended periods of continuous walking.

DESIGN

Nonrandomized control trial.

SETTING

Laboratory.

PATIENTS OR OTHER PARTICIPANTS

Volunteer sample of 8 able-bodied subjects.

INTERVENTIONS

In-shoe plantar pressures were studied during four minutes of continuous walking at controlled cadences of 70, 80, 90, 100, 110, and 120steps/min. For each cadence more than 200 steps were analyzed for each of the 8 subjects.

MAIN OUTCOME MEASURES

Pressure-time integrals, foot-to-floor contact durations, and peak pressures at all 14 locations were processed for each step. Changes were calculated compared to values at 70steps/min.

RESULTS

With increasing cadence, mean pressure-time integrals continuously decreased (45% at 120steps/min); mean foot-to-floor contact durations continuously decreased (64% at 120steps/min); and mean peak pressures increased (119% at 120steps/min).

CONCLUSIONS

Our results show that as walking cadence increases, pressure-time integrals and foot-to-floor contact durations decrease, and peak plantar pressures increase. This is clinically relevant to all kinetic gait studies because our results suggest that normal values should be established for each cadence.

Plantar pressures with total contact casting

Total contact casting has been used to aid in the healing of plantar neurotrophic ulcerations. The efficacy of total contact casts in promoting ulcer healing is presumably due to a reduction in the load over high pressure areas with pressure redistribution over the entire surface of the foot. The purpose of this study was to quantify the effectiveness of total contact casting in reducing plantar pressures. A portable microprocessor-based data-acquisition system was used for recording plantar pressures. Plantar pressures were collected from six nondisabled individuals with and without total contact casting at cast-walking cadence. In our study, there was a decrease in plantar loading under the metatarsal heads (first, fourth, fifth), the great toe, and the heel. The average decrease was 32% under the fifth metatarsal, 63% under the fourth metatarsal, 69% under the first metatarsal, 65% under the great toe, and 45% under the heel. Our study quantitatively showed that total contact casting does reduce vertical plantar pressures in high load areas.

Comparison of two fixation methods of oblique lesser metatarsal osteotomies: a biomechanical study

Two methods of internal fixation of oblique lesser metatarsal osteotomies were compared biomechanically using fresh-frozen human cadaver bones. Osteotomies were made obliquely through the metatarsal shafts and fixed with either crossed Kirschner wires or a single AO screw using the lag technique. The specimens were then fixed at their proximal end and loaded to failure using an axial torsion material testing system (MTS, Minneapolis, MN). Load displacement curves were obtained and the stiffness of the constructs were determined. Single-screw fixation was found to be significantly stiffer than the crossed wire configuration (P < .01). Single-screw fixation resulted in a stiffness of 211.2 +/- 111.7 N/cm (mean +/- SD), while stiffness of the crossed wire configuration averaged 56.9 +/- 25.1 N/cm.

Multistep measurement of plantar pressure alterations using metatarsal pads

Metatarsal pads are frequently prescribed for nonoperative management of metatarsalgia due to various etiologies. When appropriately placed, they are effective in reducing pressures under the metatarsal heads on the plantar surface of the foot. Despite the positive clinical reports that have been cited, there are no quantitative studies documenting the load redistribution effects of these pads during multiple step usage within the shoe environment. The objective of this study was to assess changes in plantar pressure metrics resulting from pad use. Ten normal adult male subjects were tested during a series of 400-step trials. Pressures were recorded from eight discrete plantar locations at the hindfoot, midfoot, and forefoot regions of the insole. Significant increases in peak pressures, contact durations, and pressure-time integrals were noted at the metatarsal shaft region with pad use (P < or = .05). Statistically significant changes in metric values were not seen at the other plantar locations, although metatarsal pad use resulted in mild decreases in mean peak pressures at the first and second metatarsal heads and slight increases laterally. Contact durations decreased at all metatarsal head locations, while pressure-time integrals decreased at the first, second, third, and fourth metatarsal heads. A slight increase in pressure-time integrals was seen at the fifth metatarsal head. The redistribution of plantar pressures tended to relate not only to the dimensions of the metatarsal pads, but also to foot size, anatomic foot configuration, and pad location. Knowledge of these parameters, along with careful control of pad dimensions and placement, allows use of the metatarsal pad as an effective orthotic device for redistributing forefoot plantar pressures.

Biomechanical and reflex responses to joint perturbations during electrical stimulation of muscle: instrumentation and measurement techniques

A test device is developed to measure ankle joint compliance and muscle activity when the ankle is subjected to perturbations in angular position (or torque) from bias positions achieved volitionally or via electrical stimulation. The ankle measurement system uses a pivoting footplate and is operable with the subject sitting or supine. A companion platform for the knee is developed that uses a rotary arm and attached leg brace and is operable with the subject's leg in the horizontal or vertical plane. The knee fixture's pivoting arm can slide to account for the cam-like movement of the knee during rotation. The devices use similar hardware and share common instrumentation and control. Precise torque or position perturbations are delivered by a computer-controlled torque motor to the ankle or knee. Angular displacement, torque, acceleration, knee fixture moment arm and electromyographic data are collected on analogue tape and simultaneously digitised and stored. A special stimulator/recording amplifier permits the recording of electromyographic signals from the stimulated muscle. Experimental data indicate that the ankle and knee devices, operated horizontally, are purely inertial systems. Sample ankle and knee joint responses to perturbations are presented.

Comparison of stability of proximal crescentic metatarsal osteotomy and proximal horizontal "V" osteotomy

Proximal metatarsal osteotomies are often performed in patients with hallux valgus and significant metatarsus primus varus. The crescentic osteotomy is popular; however, some authors have reported malunion of the metatarsal shaft caused by dorsal angulation of the osteotomy in a significant number of cases. Recently, proximal transverse "V" osteotomies have been reported to have good results, with rapid healing and no dorsal malunions. We compared the stability of a transverse, proximal "V" osteotomy, using two 0.062-inch K-wires or a 3.5-mm cortical screw for fixation, with that of the proximal crescentic osteotomy, using a 3.5-mm cortical screw fixation. The three osteotomy/fixation techniques were performed on 30 fresh-frozen cadaver feet. The specimens were loaded to failure at the fixation site by applying a load through the plantar surface of the first metatarsal head. Force versus displacement curves were obtained to calculate the failure load and stiffness. Statistical differences among the three groups were determined by the nonparametric Mann-Whitney U-test and the standard t-test. The "V" osteotomy/screw group was more stable than either the "V" osteotomy/pin group or the crescentic osteotomy/screw group. Differences in failure strength between the "V"/screw group and the other two groups were significant at the P < .01 level and the differences in stiffness were significant at the P = .05 level. No statistical differences were found between the "V"/pins and the crescentic/screw groups.

Procedures for gait analysis

Observational gait analysis is clinically useful with videotape slow-motion replay and freeze-frame, offering significant improvement over unaided visual observation. Any form of observational gait analysis, however, has limited precision and is more descriptive than quantitative. This article reviews procedures that are available for gait analysis. Gait analysis systems have evolved from cine with manual digitization, electrogoniometry, and video technology to sophisticated automated tracking systems. When used in conjunction with biomechanical models, these systems allow quantitative analysis of many specific gait characteristics such as joint moments and powers (kinetic analysis), joint angles, angular velocities, and angular accelerations (kinematic analysis). Analysis of dynamic electromyographic activity and energy consumption adds useful clinical information to gait analysis. The combination of a careful clinical assessment and gait analysis can be a powerful tool for the clinician.

Sensate and insensate in-shoe plantar pressures

In the individual with loss of protective sensation, the presence of high plantar pressures has been considered a risk factor for the development of plantar ulceration. Previous studies of insensate plantar pressures have measured a limited number of isolated, barefoot steps in a laboratory setting. Such isolated snapshots of barefoot plantar pressures do not give us insight into possible step-to-step variations or what plantar pressures occur when wearing shoes. The purpose of this study was to quantitatively examine and compare in-shoe plantar pressures during continuous walking by normal sensate and diabetic insensate subjects. A portable, insole data-acquisition system was used for pressure measurement during 4 minutes of normal continuous walking. Seven pressure sensors were placed in each insole under posterior and anterior heels, the metatarsal heads, and hallux. Twelve sensate and five insensate subjects were studied. We found that the insensate group had higher plantar pressures under posterior and anterior heels and the first metatarsals compared with the sensate group. From the study of the coefficients of variation, we demonstrated a larger step-to-step variation in plantar pressures for the insensate during continuous walking, suggesting the need for caution in interpreting the data from isolated force plate steps when studying insensate individuals.

A biomechanical impact test system for head and facial injury assessment and model development

A biomechanical test system has been developed and validated to conduct controlled uniaxial impact experiments of head and facial trauma. The design reduces off-axis accelerations which are not in the direction of impact and allows accurate positioning of test specimens. Impact forces, displacement histories, impulses at impact and spectral responses are compared to free-fall test results at contact velocities representative of facial injuries (2.5, 3.1 and 3.8 m s-1). Models based on the experimental results are developed to reveal stiffness and inertial properties of impact for use in the design of biomechanically protective steering wheels, air bags and other potential impact structures. The results indicate that the system provides a flexible yet controllable method for positioning and testing impact structures reliably.

Neuroelectric stimulation in cerebral palsy: long-term quantitative assessment

Results from multiple tests including somatosensory evoked potentials, passive resistance to motion, upper extremity motor skills evaluation, neuromuscular examination, and parental interview were evaluated in 13 children with cerebral palsy (CP) who received chronic cerebellar stimulation (CCS) for reduction of spasticity and movement disorders during the past 14 years. The prospective study included immediate postoperative follow-up data as well as longer term results from the quantitative test series. Although CCS was effective in reducing hypertonicity in CP children during the immediate short-term, the diminishment waned significantly 3-5 years postoperatively.

A microprocessor-based data-acquisition system for measuring plantar pressures from ambulatory subjects

We have developed a portable microprocessor-based data-acquisition system to measure discrete plantar pressures within the shoe from ambulatory subjects. The system offers improved accuracy, repeatability, portability, and flexibility not available in current commercial systems. It consists of 14 conductive polymer pressure sensors, 14 analog amplifiers, an 8-bit analog-to-digital converter, a microprocessor, 120 kbytes of memory space, and a parallel I/O interface. Seven pressure sensors are embedded within each insole and located at the posterior heel, anterior heel, the four metatarsal heads, and hallux of each foot. The system is capable of continuously sampling 14 channels of pressure data for 7 min at a 20-Hz sample rate. The recorded data are downloaded into a microcomputer for further processing, analysis, and display. Foot pressures have been acquired from a sensate subject during multiple walking trials.

Foot pressure distribution during walking and shuffling

The insensate foot is vulnerable to tissue damage from areas of repetitive, excessive pressures. It has been previously stated that a shuffling gait with short steps would increase the period of foot flat and thus minimize any excessive local plantar pressures. This theory was quantitatively evaluated with a portable, in-shoe pressure data-acquisition system. Seven pressure sensors were located in the left and right insoles under the metatarsal heads, hallux, and posterior and anterior heels. Plantar pressure data were acquired from ten able-bodied subjects during four minutes of continuous shuffling and walking at a metronome-controlled cadence. Peak pressures, foot-to-floor contact durations, and pressure-time integrals under each sensor during shuffling and walking were analyzed and compared. Peak pressures were decreased at all sensor sites during a shuffling gait. The greatest decreases were noted at the first and second metatarsals (up to 57.8%) and hallux (up to 63.2%). A 41.6% decrease in overall summated peak plantar pressures during shuffling was found. Foot-to-floor contact durations during shuffling were increased from 22.0% to 76.9% at all 14 sensor locations. Pressure-time integrals during shuffling were increased at the heels (up to 78.9%) and decreased at the metatarsal heads and great toes (up to 26.7%). There was a 3.3% increase in the overall summated pressure-time integral during shuffling. Our findings are consistent with the hypothesis that a shuffling gait increases the period of foot flat and the area of weight bearing, resulting in lower peak plantar pressures on any one area.

Posteromedial release for idiopathic talipes equinovarus. A long-term follow-up study

Eighteen children with 26 idiopathic talipes equinovarus deformities were treated by postermedial release (PR) in the interval between 1975 and 1980 and investigated retrospectively. Evaluations included physical examination, functional evaluation, roentgenographic evaluation, and evaluation of foot track tracing pattern. The average follow-up period was 8.2 years. Thirty percent had had previous tendo Achilles lengthenings and 15% had had previous lengthenings plus posterior capsulotomies. Based on Turco's criteria, the results of PR were graded 38.9% excellent, 26.9% good, 15.6% fair, and 18.6% failure.

Analysis of neuroelectric implant integrity

A 10-year follow-up study of neuroelectric implant integrity has been completed for 27 subjects who were treated for movement disorders associated with cerebral palsy. Data used for analysis included X-ray material, clinical data, and results from electrophysiological testing. Of the 21 subjects with subcutaneous receivers placed in the thoracic region, 81% experienced wire (67%) or receiver (14%) failure. Of the 6 subjects with subcutaneous receivers placed in the occipital region, there were no wire failures and one (17%) receiver failure. The occipital units lasted a minimum of 5.2 years without complications, whereas the thoracic units failed as early as 6 months after surgery, and lasted an average of 3.8 years. All wire fractures occurred between C1 and T1. Two types of fracture occurred, one consisting of a clean break and the other consisting of a scenario of bending and kinking, then thinning and fraying, and finally progressive multiple fragmentation. With a few exceptions the clean breaks occurred between C1 and C3, while the fraying scenario occurred between C6 and T1. Mechanisms for failure are discussed, as are results from material tests of wire samples.

Thoracic suspension: quantitative effects upon seating pressure and posture

Seating pressure in 10 subjects using a thoracic suspension orthosis was studied quantitatively. Anterior, posterior, and ischial pressures were measured bilaterally both unsuspended and during a 90 to 120 minute interval while suspended. Significant decreases in seating pressure were noted following suspension, with a mean decrease of 59.8%. Significant changes in lateral support were noted with suspension, as was a reduction in both the absolute pressure and relative distribution of pressure to the ischial areas. Relative redistribution of pressure in the anterior-posterior direction was related to leg support condition. All subjects who presented with pressure sores healed subsequent to thoracic suspension. Those with spinal curvature showed a 10 to 20 degree correction immediately following suspension. This correction generally was not maintained, however, in a temporal analysis. The data indicates that thoracic suspension can effectively reduce seating pressure and alter lateral posture, while leg support condition has a greater effect upon anterior-posterior pressure distribution. The use of a seat cushion to prevent subject swinging while suspended did not adversely affect the overall suspended pressures in this study, although the subjects without seat cushions showed lower overall suspended pressures.