Understanding the capacity of children with congenital unilateral below-elbow deficiency to actuate their affected muscles

In recent years, commercially available dexterous upper limb prostheses for children have begun to emerge. These devices derive control signals from surface electromyography (measure of affected muscle electrical activity, sEMG) to drive a variety of grasping motions. However, the ability for children with congenital upper limb deficiency to actuate their affected muscles to achieve naturalistic prosthetic control is not well understood, as compared to adults or children with acquired hand loss. To address this gap, we collected sEMG data from 9 congenital one-handed participants ages 8-20 years as they envisioned and attempted to perform 10 different movements with their missing hands. Seven sEMG electrodes were adhered circumferentially around the participant's affected and unaffected limbs and participants mirrored the attempted missing hand motions with their intact side. To analyze the collected sEMG data, we used time and frequency domain analyses. We found that for the majority of participants, attempted hand movements produced detectable and consistent muscle activity, and the capacity to achieve this was not dissimilar across the affected and unaffected sides. These data suggest that children with congenital hand absence retain a degree of control over their affected muscles, which has important implications for translating and refining advanced prosthetic control technologies for children.

Moving a missing hand: children born with below elbow deficiency can enact hand grasp patterns with their residual muscles

Children with a unilateral congenital below elbow deficiency (UCBED) have one typical upper limb and one that lacks a hand, ending below the elbow at the proximal/mid forearm. UCBED is an isolated condition, and affected children otherwise develop normal sensorimotor control. Unlike adults with upper limb absence, the majority of whom have an acquired loss, children with UCBED never developed a hand, so their residual muscles have never actuated an intact limb. Their ability to purposefully modulate affected muscle activity is often assumed to be limited, and this assumption has influenced prosthetic design and prescription practices for this population as many modern devices derive control signals from affected muscle activity. To better understand the motor capabilities of the affected muscles, we used ultrasound imaging to study 6 children with UCBED. We examined the extent to which subjects activate their affected muscles when performing mirrored movements with their typical and missing hands. We demonstrate that all subjects could intentionally and consistently enact at least five distinct muscle patterns when attempting different missing hand movements (e.g., power grasp) and found similar performance across affected and typically developed limbs. These results suggest that although participants had never actuated the missing hand they could distinctively and consistently activate the residual muscle patterns associated with actions on the unaffected side. These findings indicate that motor control still develops in the absence of the normal effector, and can serve as a guide for developing prostheses that leverage the full extent of these children's motor control capabilities.

The Human Phenotype Ontology in 2024: phenotypes around the world

The Human Phenotype Ontology (HPO) is a widely used resource that comprehensively organizes and defines the phenotypic features of human disease, enabling computational inference and supporting genomic and phenotypic analyses through semantic similarity and machine learning algorithms. The HPO has widespread applications in clinical diagnostics and translational research, including genomic diagnostics, gene-disease discovery, and cohort analytics. In recent years, groups around the world have developed translations of the HPO from English to other languages, and the HPO browser has been internationalized, allowing users to view HPO term labels and in many cases synonyms and definitions in ten languages in addition to English. Since our last report, a total of 2239 new HPO terms and 49235 new HPO annotations were developed, many in collaboration with external groups in the fields of psychiatry, arthrogryposis, immunology and cardiology. The Medical Action Ontology (MAxO) is a new effort to model treatments and other measures taken for clinical management. Finally, the HPO consortium is contributing to efforts to integrate the HPO and the GA4GH Phenopacket Schema into electronic health records (EHRs) with the goal of more standardized and computable integration of rare disease data in EHRs.

De novo TRPM3 missense variant associated with neurodevelopmental delay and manifestations of cerebral palsy

We identified a de novo heterozygous transient receptor potential cation channel subfamily M (melastatin) member 3 (TRPM3) missense variant, p.(Asn1126Asp), in a patient with developmental delay and manifestations of cerebral palsy (CP) using phenotype-driven prioritization analysis of whole-genome sequencing data with Exomiser. The variant is localized in the functionally important ion transport domain of the TRPM3 protein and predicted to impact the protein structure. Our report adds TRPM3 to the list of Mendelian disease-associated genes that can be associated with CP and provides further evidence for the pathogenicity of the variant p.(Asn1126Asp).

HipScreen mobile app for the measurement of hip migration percentage in children with cerebral palsy: Accuracy, reliability, and discriminatory ability

AIM

To assess the accuracy, reliability, and discriminatory ability of a mobile app for measurement of migration percentage in hip surveillance radiographs of children with cerebral palsy (CP).

METHOD

The free mobile app HipScreen (www.hipscreen.org) was utilized by a diverse group of users to measure the migration percentage of 40 hips at two time points after completing an online tutorial and competency test. The mean absolute error (MAE) was calculated against the reference standard obtained on a radiology workstation. Statistical analyses included linear regression, intraclass correlation coefficient (ICC), and area under receiver-operating characteristic curve (AUC).

RESULTS

Thirty-seven users completed the study, with 30 having a healthcare professional background, but only 15 with x-ray interpretation expertise. The overall MAE of migration percentage measurement using the HipScreen app was 5.72% (95% confidence interval [CI]: 5.38-6.06), with good reliability between time points (ICC = 0.83). With a migration percentage less than 30% considered as a positive case, the HipScreen app had a sensitivity of 94% (95% CI: 87-97), specificity of 66% (95% CI: 61-77), and an AUC of 0.92 (95% CI: 0.88-0.96).

INTERPRETATION

Users from a broad range of backgrounds can utilize the HipScreen app to measure hip surveillance radiographs with clinically acceptable accuracy, reliability, and discriminatory ability.

WHAT THIS PAPER ADDS

The HipScreen app can accurately and reliably measure migration percentage. As a screening tool, HipScreen has excellent sensitivity and discriminatory ability. A broad range of HipScreen users achieve clinically acceptable performance.

A review of upper limb pediatric prostheses and perspectives on future advancements

Many complex factors affect whether a child with a congenital upper limb deficiency will wear a prosthetic limb. Ultimately, for a child to wear and use their prosthesis, it must facilitate the effective performance of daily tasks and promote healthy social interactions. Although numerous pediatric devices are available, most provide a single open-close grasp (if a grasping function is available at all) and often offer nonanthropomorphic appearances, falling short of meeting these criteria. In this narrative review, we provide a critical assessment of the state of upper limb prostheses for children. We summarize literature using quality of life measures and categorize driving factors affecting prosthesis use into two main groupings: psychosocial and physical functioning. We define psychosocial functioning as factors related to social inclusion/exclusion, emotional function, independence, and school functioning. Physical functioning is defined as factors associated with the physical use of a prosthesis. The reviewed literature suggests that psychosocial domains of quality of life may be influenced by a congenital limb deficiency, and currently available prostheses provide little benefit in the physical functioning domains. Finally, we discuss technological advancements in adult prostheses that have yet to be leveraged for pediatric devices, including describing recently developed adult electric hands that may improve physical functioning through multiple grasping configurations and provide more hand-like cosmesis. We outline actions necessary to translate similar technologies for children and discuss further strategies to begin removing barriers to pediatric device adoption.

A Longitudinal Study of Quantitative Muscle Strength and Functional Motor Ability in Ambulatory Boys with Duchenne Muscular Dystrophy

BACKGROUND

Duchenne muscular dystrophy (DMD) is an X-linked recessive genetic disorder, that is characterized by progressive muscle degeneration and loss of ambulation between 7-13 years of age. Novel pharmacological agents targeting the genetic defects and disease mechanisms are becoming available; however, corticosteroid (CS) therapy remains the standard of care.

OBJECTIVE

The purpose of this longitudinal study was to elucidate the effect of CS therapy on the rate of muscle strength and gross motor skill decline in boys with DMD and assess the sensitivity of selected outcome measures.

METHODS

Eighty-four ambulatory boys with DMD (49-180 months), 70 on CS, 14 corticosteroid naïve (NCS), participated in this 8-year multi-site study. Outcomes included; isokinetic dynamometry, the Standing (STD) and Walking/Running/jumping (WRJ) dimensions of the Gross Motor Function Measure (GMFM), and Timed Function Tests (TFTs). Nonlinear mixed modeling procedures determined the rate of change with age and the influence of steroids.

RESULTS

Despite CS therapy the rate of decline in strength with age was significant in all muscle groups assessed. CS therapy significantly slowed decline in knee extensor strength, as the NCS group declined at 3x the rate of the CS group. Concurrently, WRJ skills declined in the NCS group at twice the rate of the CS group. 4-stair climb and 10 meter walk/run performance was superior in the boys on CS therapy.

CONCLUSION

CS therapy slowed the rate of muscle strength decline and afforded longer retention of select gross motor skills in boys on CS compared to boys who were NCS. Isokinetic dynamometry, Walk/Run/Jump skills, and select TFTs may prove informative in assessing the efficacy of new therapeutics in ambulatory boys with DMD.

Three-dimensional functional workspace of thumb prehension

BACKGROUND

Clinical assessment of thumb motion is challenging, due to the complex anatomy and motion of the thumb. It is especially difficult to measure hand movement during activity, and to measure the effects of surgery that changes the morphology of the thumb. A three-dimensional model of the hand may enable clinicians to better assess prehension and thumb motion at baseline, and following surgical intervention.

METHODS

A kinematic model of the hand was developed to measure thumb and finger position during functional tasks, enabling the calculation of the volume of space in which prehension could occur. This method was validated by application to a mechanical model of the hand, and then applied to ten adult participants, using three-dimensional motion analysis with a marker array developed for the purpose of this study.

FINDINGS

This method can be used to accurately measure three-dimensional thumb joint range of motion (RoM) and predicted functional workspace during functional activities. The thumb carpometacarpal joint was predominantly responsible for thumb position during functional tasks. Predicted functional workspace is proportional to hand morphometric measurements.

INTERPRETATION

A kinematic model of the hand measures thumb RoM and predicts functional workspace during functional activities.

Longitudinal community walking activity in Duchenne muscular dystrophy

INTRODUCTION

Natural history studies for Duchenne muscular dystrophy (DMD) have not included measures of community ambulation.

METHODS

Step activity (SA) monitors quantified community ambulation in 42 boys (ages 4-16 years) with DMD with serial enrollment up to 5 years by using a repeated-measures mixed model. Additionally, data were compared with 10-meter walk/run (10mWR) speed to determine validity and sensitivity.

RESULTS

There were significant declines in average strides/day and percent strides at moderate, high and pediatric high rates as a function of age (P < 0.05). Significant correlations for 10mWR versus high and low stride rates were found at baseline (P < 0.05). SA outcomes were sensitive to change over 1 year, but the direction and parameter differed by age group (younger vs. older). Changes in strides/day and percentages of high frequency and low frequency strides correlated significantly with changes in 10mWR speed (P < 0.05).

DISCUSSION

Community ambulation data provide valid and sensitive real-world measures that may inform clinical trials. Muscle Nerve 57: 401-406, 2018.

Outcomes of Cutaneous Scar Revision During Surgical Implant Removal in Children with Cerebral Palsy

BACKGROUND

Children who have had surgery involving the placement of an implant frequently undergo a subsequent surgery for hardware removal. The cosmesis of surgical scars following initial and subsequent surgeries is unpredictable. Scar incision (subsequent surgical incision through the initial scar) or excision (around the initial scar) is selected on the basis of the quality of the initial scar. The outcomes following these techniques have not been determined.

METHODS

This prospective, consecutive case series was designed to compare outcomes following surgical scar incision versus excision at the time of implant removal in children with cerebral palsy. Photographs of the scars were made preoperatively and at 6 and 12 months following implant removal and were graded for scar quality utilizing the modified Stony Brook Scar Evaluation Scale (SBSES). Parental assessment of scar appearance was performed at the same time points utilizing a visual analog cosmetic scale (VACS).

RESULTS

The scars that were selected for incision had significantly worse SBSES scores at 6 and 12 months following the second surgery compared with preoperative values. However, parents' VACS scores of the incised scars, although worse at 6 months, were comparable with preoperative scores at 12 months. Scars that were selected for excision had significantly worse SBSES scores at 6 months but scores that were comparable with preoperative values at 12 months. VACS scores for the excised scars were comparable at the 3 time points.

CONCLUSIONS

Surgical incisions that initially healed with good scar quality generally healed well (from the parents' perspective) following subsequent incision through the previous scar. Surgical incisions that initially healed with poor scar quality did not heal better following excision of the previous scar. In such situations, surgical excision of the existing scar should occur in conjunction with additional adjuvant therapies to improve cosmesis.

LEVEL OF EVIDENCE

Therapeutic Level II. See Instructions for Authors for a complete description of levels of evidence.

Rasch analysis of items from two self-report measures of motor function: determination of item difficulty and relationships with children's ability levels

AIM

The aim of this article was to determine item measurement properties of a set of items selected from the Gillette Functional Assessment Questionnaire (FAQ) and the Pediatric Outcome Data Collection Instrument (PODCI) using Rasch analysis, and to explore relationships between the FAQ/PODCI combined set of items, FAQ walking scale level, Gross Motor Function Classification System (GMFCS) levels, and the Gait Deviation Index on a common measurement scale.

METHOD

Rasch analysis was performed on data from a retrospective chart review of parent-reported FAQ and PODCI data from 485 individuals (273 males; 212 females; mean age 9 y 10 mo, SD 3 y 10 mo) who underwent first-time three-dimensional gait analysis. Of the 485 individuals, 289 had a diagnosis of cerebral palsy (104 GMFCS level I, 97 GMFCS level II, 69 GMFCS level III, and 19 GMFCS level IV). Rasch-based person abilities and item difficulties based on subgroups defined by the FAQ walking scale level, Gait Deviation Index, and the GMFCS level were compared.

RESULTS

The FAQ/PODCI item set demonstrated necessary Rasch characteristics to support its use as a combined measurement scale. Item groupings at similar difficulty levels were consistent with the mean person abilities of subgroups based on FAQ walking scale level, Gait Deviation Index, and GMFCS level.

INTERPRETATION

Rasch-derived person ability scores from the FAQ/PODCI combined item set are consistent with clinical measures. Rasch analysis provides insights that may improve interpretation of the difficulty of motor functions for children with disabilities.

Gillette Functional Assessment Questionnaire 22-item skill set: factor and Rasch analyses

AIM

To determine dimensionality and item-level properties of the Gillette Functional Assessment Questionnaire (FAQ) 22-item skill set using factor and Rasch analyses.

METHOD

A retrospective review of parent-reported FAQ 22-item skill set data was conducted of 485 individuals (273 males, 212 females; mean age 9 y 10 mo, SD 3 y 10 mo), including 289 with cerebral palsy and 196 with a variety of other neuromusculoskeletal conditions with orthopedic impairments. Factor analyses to validate unidimensionality of the skill set and Rasch analyses to determine relative item difficulty, item and test level information, and content coverage of the item set were performed. Differential item functioning analysis of sub-groups based on sex, diagnosis grouping, and age was conducted. Precision of score estimates for the item set was analyzed.

RESULTS

The FAQ 22-item skill set demonstrates unidimensional structure and good item fit statistics. No floor or ceiling effects were noted. Differential item functioning (DIF) based on age was noted for seven items, four items showed diagnosis group-related DIF, and one item sex-related DIF. Precision was adequate in the mid-range range of abilities.

INTERPRETATION

Based on this analysis, the FAQ 22-item skill set is a hierarchical set of interval scaled items suitable for measuring locomotor skill ability in children.

Factor- and item-level analyses of the 38-item activities scale for kids-performance

AIM

Children and adolescents highly value their ability to participate in relevant daily life and recreational activities. The Activities Scale for Kids-performance (ASKp) instrument measures the frequency of performance of 30 common childhood activities, and has been shown to be valid and reliable. A revised and expanded 38-item ASKp (ASKp38) version has been reported in recent literature and is currently used in clinical research. The aim of this paper is to assess the factor structure and item-level statistics of the ASKp38.

METHOD

Our study used factor analyses and Rasch analyses to determine the item-set dimensionality and to calculate item-level statistics respectively, for existing ASKp38 data from 200 children (104 males; 96 females; mean age 12y 7mo; SD 2y 8mo; range 6-20y) with physical disabilities. The children had a variety of physical impairments including cerebral palsy (n = 105; range 8-13 y), limb salvage (n = 18; range 11-20y), arthrogryposis (n = 13; 6-17y), and other, including individuals with spina bifida and spinal cord injury (n = 64; 8-19 y).

RESULTS

A two-factor model, with components of activities of daily living and play, most optimally fit the data. Item-fit statistics based on this two-factor model demonstrated adequate fit and content coverage.

INTERPRETATION

The ASKp38 appears to consist of two factors, defined as (1) activities of daily living and (2) play, and may be used to measure the frequency of activity performance on two corresponding subscales.

The contralateral unimpaired arm as a control for upper extremity kinematic analysis in children with brachial plexus birth palsy

BACKGROUND

Kinematic studies of abnormal upper extremity (UE) motion provide the unique and valuable perspective of motion analysis during simulated functional tasks. However, they require comparison with healthy control data. Obtaining this control data usually entails testing a healthy population, which can be costly and time consuming, requiring separate subject inclusion criteria, recruitment, and institutional review board approval. The kinematics of the unimpaired UE in people with unilateral impairment have not been analyzed and documented. The purpose of this study was to compare UE motion during activities of daily living in the contralateral unimpaired arm of subjects with brachial plexus birth palsy (BPBP) with an age-matched control population.

METHODS

The contralateral arms of 40 subjects with unilateral BPBP were compared with the arms of 15 healthy subjects using an established 3-dimensional upper extremity motion analysis protocol.

RESULTS

There were no significant differences between the 2 arms on 17 of 19 motion parameters. The 2 differences that were statistically significant (P < 0.05) were not clinically meaningful.

CONCLUSIONS

The contralateral arms of children with unilateral BPBP can be used as controls for future upper extremity motion analysis studies of this population, and further recruitment of age-matched controls is not necessary for comparison with 5- to 8-year-old children with BPBP.

Outcome assessments in children with cerebral palsy, part II: discriminatory ability of outcome tools

Discriminatory ability of several pediatric outcome tools was assessed relative to Gross Motor Function Classification System (GMFCS) level in patients with cerebral palsy. Five hundred and sixty-two patients (400 with diplegia, 162 with hemiplegia; 339 males, 223 females; age range 4-18y, mean 11y 1mo [SD 3y 7mo]), classified as GMFCS Levels I to III, participated in this prospective multicenter, cross-sectional study. All tools were completed by parents and participants when appropriate. Effect size indices (ESIs) for parametric variables and odds ratios for non-parametric data quantified the magnitude of differences across GMFCS levels. Binary logistic regression models determined discrimination, and receiver operating characteristic curves addressed sensitivity and specificity. Between Levels I and II, the most discriminatory tools were Gross Motor Function Measure (GMFM-66), velocity, and WeeFIM Mobility. Between Levels II and III, the most discriminatory tools were GMFM Dimension E, Pediatric Functional Independence Measure (WeeFIM) Self-Care and Mobility, cadence, and Gillette Functional Assessment Questionnaire Question 1. Large ESIs were noted for Parent and Child reports of Pediatric Outcomes Data Collection Instrument (PODCI) Sports & Physical Function, Parent report of PODCI Global Function, GMFM Dimension E, and GMFM-66 across all GMFCS level comparisons. The least discriminatory tools were the Quality of Life and cognition measures; however, these are important in comprehensive assessments of treatment effects.

Impact of prostheses on function and quality of life for children with unilateral congenital below-the-elbow deficiency

BACKGROUND

Children with unilateral congenital below-the-elbow deficiency present a dilemma to clinicians. Parents want the child to have a prosthesis and, because it seems that the deficiency will cause functional problems, one is customarily prescribed for infants. Use of the prosthesis is then encouraged throughout childhood. However, these children frequently abandon the prosthesis. There are no evidence-based guidelines regarding prescription of prostheses or standard methods for assessing use and function.

METHODS

A multicenter outcomes study was done to assess the quality of life and function of 489 children with a unilateral congenital below-the-elbow deficiency; 321 wore a prosthesis, and 168 did not. The Unilateral Below-the-Elbow Test (UBET) was designed, validated, and administered to these children along with several outcomes measures, including the Pediatric Outcomes Data Collection Instrument (PODCI), the Pediatric Quality of Life Inventory (PedsQL), and the Prosthetic Upper Extremity Functional Index (PUFI).

RESULTS

Use of a prosthesis was not associated with any clinically relevant differences in PODCI or PedsQL scores. Non-wearers performed either the same as or better than wearers on the UBET. When queried (with use of the PUFI) about performance of various tasks, non-wearers scored themselves higher than wearers. Children with a unilateral congenital below-the-elbow deficiency scored the same as or higher than the general population on the PedsQL. They scored significantly lower than the general population on the PODCI Upper Extremity Physical Function Domain and higher on the Happiness Domain, but the differences were small.

CONCLUSIONS

Prostheses may help with social acceptance or may be useful as tools for specialized activities, but they do not appear to improve function or quality of life, which are nearly normal for children with unilateral congenital below-the-elbow deficiency regardless of whether they wear a prosthesis. These findings call into question the standard practices of fitting infants with prostheses and encouraging young children to wear the prosthesis.

The Unilateral Below Elbow Test: a function test for children with unilateral congenital below elbow deficiency

The Unilateral Below Elbow Test (UBET) was developed to evaluate function in bimanual activities for both the prosthesis wearer and non-wearer. Nine tasks were chosen for each of four age-specific categories defined by development stages of hand function (2-4y, 5-7y, 8-10y, and 11-21y). Two scales, Completion of Task and Method of Use, were designed to rate performance. To measure reliability, four occupational therapists scored samples of videotaped UBET performances. For Completion of Task, an interval scale, agreement in scoring was measured with interclass correlation coefficients (ICC; n=9; five females, four males). For Method of Use, a nominal scale, chance-adjusted association was calculated with Cohen's kappa coefficients (interobserver n=198; 111 females, 87 males; intraobserver n=93; 56 females, 37 males). For Completion of Task, the average ICC was 0.87 for the prosthesis-on condition, and 0.85 for the prosthesis-off condition. ICCs exceeded 0.80 for eight out of nine tasks for the two older age groups, but for only five out of nine tasks in the younger age groups. Higher inter- and intraobserver kappa coefficients for Method of Use resulted when scoring children with their prostheses on versus off. The oldest age group had lower kappa values than the other three groups. The UBET is recommended for the functional evaluation of Completion of Task in children with unilateral congenital below elbow deficiency with and without their prostheses. Method of Use scoring can evaluate individuals for directed therapy interventions or prosthetic training.

Assessment of children with brachial plexus birth palsy using the Pediatric Outcomes Data Collection Instrument

The purpose of this study was to determine whether the Pediatric Outcomes Data Collection Instrument (PODCI) measures differences in function between children with brachial plexus birth palsy (BPBP) who are candidates for shoulder tendon surgery and age-matched controls. The PODCI was administered prospectively to 23 children with BPBP who were candidates for shoulder tendon surgery. Their results were compared with published PODCI data for control subjects, and factors associated with function within the BPBP cohort were determined. Children in the BPBP cohort had significantly lower PODCI scores in upper extremity function, sports, and global function than control subjects. Limited active shoulder external rotation was significantly associated with lower functional scores. The PODCI measures diminished upper extremity function in children with BPBP who are candidates for shoulder tendon surgery, thereby showing promise as a tool for measuring baseline function and postoperative functional gains for children with BPBP.

Gross Motor Function Classification System and outcome tools for assessing ambulatory cerebral palsy: a multicenter study

The relationships between different levels of severity of ambulatory cerebral palsy, defined by the Gross Motor Function Classification System (GMFCS), and several pediatric outcome instruments were examined. Data from the Gross Motor Function Measure (GMFM), Pediatric Orthopaedic Data Collection Instrument (PODCI), temporal-spatial gait parameters, and oxygen cost were collected from six sites. The sample size for each assessment tool ranged from 226 to 1047 participants. There were significant differences among GMFCS levels I, II, and III for many of the outcome tools assessed in this study. Strong correlations were seen between GMFCS level and each of the GMFM sections D and E scores, the PODCI measures of Transfer and Mobility, and Sports and Physical Function, Gait Velocity, and Oxygen Cost. Correlations among tools demonstrated that the GMFM sections D and E scores correlated with the largest number of other tools. Logistic regression showed GMFM section E score to be a significant predictor of GMFCS level. GMFM section E score can be used to predict GMFCS level relatively accurately (76.6%). Study data indicate that the assessed outcome tools can distinguish between children with different GMFCS levels. This study establishes justification for using the GMFCS as a classification system in clinical studies.

Kinematic and kinetic analysis of running in children with cerebral palsy

Computer-based analysis of gait was used to study walking and running in 19 children with spastic-diplegic cerebral palsy (CP) and 15 healthy control children. Temporospatial parameters, kinematic and kinetic data were compared and contrasted between groups for both types of gait. The majority of children with diplegic CP, who are independent ambulators, are able to run. These children increase their velocity by increasing their cadence, a mechanism that is distinct (and presumably less energy efficient) from that used by healthy children. Sagittal-plane kinematic and kinetic profiles at the ankle in children with CP were more similar to normal profiles in running than in walking, suggesting that the primary deviations at the ankle associated with CP are better tolerated at greater velocities. Relative power analysis showed that, like healthy children, those with CP depend more upon the proximal musculature about the hip for power generation as the velocity of gait increases. Children with CP achieve energy transfer between adjacent joints during walking and running in a manner comparable to unaffected children. Running is an important activity for children and should be considered in the functional assessment of those with CP.

A dynamic biomechanical analysis of the etiology of adolescent tibia vara

Biomechanical overload of the proximal tibial physis due to static varus alignment and excessive body weight has been implicated in the etiology of infantile tibia vara. Whether a similar pathophysiologic process applies to adolescent tibia vara is controversial, with poor consensus concerning the nature and significance of static knee alignment early in the course of the disease. This study examines the hypothesis that dynamic gait deviations to compensate for increased thigh girth associated with obesity (fat-thigh gait) could result in increased loading of the medial compartment of the knee during the gait cycle. Three-dimensional motion analysis was used to identify the kinematic/kinetic profile associated with fat-thigh gait. Gait deviations identified were dynamic stance-limb knee varus, increased stance-limb knee rotation, and swing-limb circumduction. Pathologic compressive forces were generated in an anthropometric model by using recorded fat-thigh gait deviations and clinically appropriate excessive body weight. This analysis supports the clinical observation that underlying static varus malalignment of the knee is not a prerequisite for the development of adolescent tibia vara and illustrates the significance of dynamic gait deviations when considering knee-joint loading.

A biomechanical and clinical evaluation of a patellofemoral knee brace

A clinical and biomechanical evaluation of a patellofemoral knee brace was conducted to determine subjectively and objectively if the brace was effective in controlling knee motion and relieving patellofemoral pain symptoms. The subjective results indicated that the patellofemoral brace was able to significantly improve the level of perceived knee stability and decrease the level of pain experienced by all the subjects during their daily living and athletic activities. The objective results showed that the patellofemoral brace had no effect on knee flexion angle during gait or level walking, stair ascent, or stair descent for 2 groups of subjects (patellofemoral patients and controls). Joint pain and stability are affected by factors other than knee flexion angle.

The prediction of metabolic energy expenditure during gait from mechanical energy of the limb: a preliminary study

Measurements of metabolic energy consumption and free-walking velocity were recorded for four persons with trans-femoral amputation with variations of prosthesis mass and mass distribution. Hot-film anemometers, rate gyroscopes, and a force platform were used to measure prosthetic limb segment velocities and ground reaction forces. Metabolic energy consumption for the nine configurations of mass and mass distribution averaged 1.177 cal/kg/m with a standard deviation of +/- 0.052 cal/kg/m. Two measures of mechanical work of the amputated extremity, one based on power developed across joints (W1) and the other based on changes in energy of the body segments (W2), were computed to be 0.162 +/- 0.014 and 0.175 +/- 0.025 cal/kg/m, respectively. A linear regression model led to rejections of both W1 and W2 as predictors of metabolic energy expenditure of the amputee at a significance level of 0.05.

Ankle weight effect on gait: orthotic implications

Oxygen consumption during ambulation was measured in 10 normal subjects wearing ankle weights of 0.91 kg, 1.82 kg, and 2.73 kg, either on the right ankle or bilaterally. Subjects walked at self-selected speeds and oxygen consumption was measured over 1-minute intervals during steady-state walking. Oxygen consumption per unit distance and oxygen consumption rate demonstrated significant positive linear correlations with added weight (P = .001, P = 0.007, respectively). Velocity demonstrated a significant decrease when correlated with added weight (P = 0.03). Multiple regression analysis was used to relate these measures of oxygen consumption rates to velocity, age, and added weight, yielding predictive relationships. Based on these results, the weight of orthoses should be minimized in order to maximize walking velocity and minimize oxygen consumption per unit distance. The advantage of a light-weight, molded plastic ankle-foot orthosis (AFO) over heavier AFO designs is demonstrated by this study.