A common data language for clinical research studies: the National Institute of Neurological Disorders and Stroke and American Academy for Cerebral Palsy and Developmental Medicine Cerebral Palsy Common Data Elements Version 1.0 recommendations

To increase the efficiency and effectiveness of clinical research studies, cerebral palsy (CP) specific Common Data Elements (CDEs) were developed through a partnership between the National Institute of Neurological Disorders and Stroke (NINDS) and the American Academy of Cerebral Palsy and Developmental Medicine (AACPDM). International experts reviewed existing NINDS CDEs and tools used in studies of children and young people with CP. CDEs were compiled, subjected to internal review, and posted online for external public comment in September 2016. Guided by the International Classification of Functioning, Disability and Health framework, CDEs were categorized into six domains: (1) participant characteristics; (2) health, growth, and genetics; (3) neuroimaging; (4) neuromotor skills and functional assessments; (5) neurocognitive, social, and emotional assessments; and (6) engagement and quality of life. Version 1.0 of the NINDS/AACPDM CDEs for CP is publicly available on the NINDS CDE and AACPDM websites. Global use of CDEs for CP will standardize data collection, improve data quality, and facilitate comparisons across studies. Ongoing collaboration with international colleagues, industry, and people with CP and their families will provide meaningful feedback and updates as additional evidence is obtained. These CDEs are recommended for NINDS-funded research for CP.

WHAT THIS PAPER ADDS

This is the first comprehensive Common Data Elements (CDEs) for children and young people with CP for clinical research. The CDEs for children and young people with CP include common definitions, the standardization of case report forms, and measures. The CDE guides the standardization for data collection and outcome evaluation in all types of studies with children and young people with CP. The CDE ultimately improves data quality and data sharing.

A degradation fragment of type X collagen is a real-time marker for bone growth velocity

Despite its importance as a key parameter of child health and development, growth velocity is difficult to determine in real time because skeletal growth is slow and clinical tools to accurately detect very small increments of growth do not exist. We report discovery of a marker for skeletal growth in infants and children. The intact trimeric noncollagenous 1 (NC1) domain of type X collagen, the marker we designated as CXM for Collagen X Marker, is a degradation by-product of endochondral ossification that is released into the circulation in proportion to overall growth plate activity. This marker corresponds to the rate of linear bone growth at time of measurement. Serum concentrations of CXM plotted against age show a pattern similar to well-established height growth velocity curves and correlate with height growth velocity calculated from incremental height measurements in this study. The CXM marker is stable once collected and can be accurately assayed in serum, plasma, and dried blood spots. CXM testing may be useful for monitoring growth in the pediatric population, especially responses of infants and children with genetic and acquired growth disorders to interventions that target the underlying growth disturbances. The utility of CXM may potentially extend to managing other conditions such as fracture healing, scoliosis, arthritis, or cancer.

Hip kinetics during gait are clinically meaningful outcomes in young boys with Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is an X-linked genetic neuromuscular disorder characterized by progressive proximal to distal muscle weakness. The success of randomized clinical trials for novel therapeutics depends on outcome measurements that are sensitive to change. As the development of motor skills may lead to functional improvements in young boys with DMD, their inclusion may potentially confound clinical trials. Three-dimensional gait analysis is an under-utilized approach that can quantify joint moments and powers, which reflect functional muscle strength. In this study, gait kinetics, kinematics, spatial-temporal parameters, and timed functional tests were quantified over a one-year period for 21 boys between 4 and 8 years old who were enrolled in a multisite natural history study. At baseline, hip moments and powers were inadequate. Between the two visits, 12 boys began a corticosteroid regimen (mean duration 10.8±2.4 months) while 9 boys remained steroid-naïve. Significant between-group differences favoring steroid use were found for primary kinetic outcomes (peak hip extensor moments (p=.007), duration of hip extensor moments (p=.007), peak hip power generation (p=.028)), and spatial-temporal parameters (walking speed (p=.016) and cadence (p=.021)). Significant between-group differences were not found for kinematics or timed functional tests with the exception of the 10m walk test (p=.03), which improves in typically developing children within this age range. These results indicate that hip joint kinetics can be used to identify weakness in young boys with DMD and are sensitive to corticosteroid intervention. Inclusion of gait analysis may enhance detection of a treatment effect in clinical trials particularly for young boys with more preserved muscle function.

Prednisone and Deflazacort in Duchenne Muscular Dystrophy: Do They Play a Different Role in Child Behavior and Perceived Quality of Life?

The aim of this study was to determine whether prednisone and deflazacort play a different role in child behavior and perceived health related psychosocial quality of life in ambulant boys with Duchenne Muscular Dystrophy. As part of a prospective natural-history study, parents of sixty-seven ambulant boys with DMD (27 taking prednisone, 15 taking deflazacort, 25 were steroid naïve) completed the Child Behavior Checklist (CBCL) for assessment of behavioral, emotional and social problems and both parents and boys with DMD completed the PedsQL™4.0 generic core scale short form. Boys with DMD had higher rates of general behavioral problems than age-matched peers. No significant differences were found among the groups for any of the CBCL syndrome scales raw scores, including internalizing and externalizing behaviors; however, on average boys taking deflazacort demonstrated more withdrawn behaviors than those taking prednisone, while on average the boys taking prednisone demonstrated more aggressive behaviors than boys taking deflazacort. Age, internalizing and externalizing behaviors accounted for 39 and 48% of the variance in psychosocial quality of life for both parents and boys with DMD, respectively. Overall, the use of steroids was not associated with more behavioral problems in boys with DMD. As behavior played a significant role in psychosocial quality of life, comprehensive assessment and treatment of behavioral problems is crucial in this population.

Correlation of collagen X biomarker (CXM) with peak height velocity and radiographic measures of growth in idiopathic scoliosis

STUDY DESIGN

Prospective comparative study.

OBJECTIVES

Evaluate the correlation of CXM with established measures of growth. Theoretically higher CXM levels would correlate with rapid longitudinal bone growth and lower levels with growth cessation. Assessment of growth status in patients with pediatric spinal deformity is critical. The current gold standards for assessing skeletal maturity are based on radiographic measures and have large standard errors (SE). Type X collagen (COLX) is produced in the growing physis during enchondral ossification. CXM is a COLX breakdown product that can be measured in blood products. CXM, thus, is a direct measure of enchondral ossification.

METHODS

IRB-approved prospective study. Q6mo anthropometrics and spine PA biplanar slot scanner images including the hand were assessed for major Cobb, Risser score (RS), triradiate cartilage status (TRC), Greulich and Pyle bone age (BA), and Sanders Score (SS). Serial dried blood spots (DBS) to obtain CXM levels were collected 3 consecutive days Q1-2 months based on SS.

RESULTS

47 idiopathic scoliosis patients, Cobb ≥ 20 were enrolled. Mean enrollment age was 11.8 years (range 7.1-16.6 years). 3103 DBS samples were assayed in quadruplicate. CXM results were highly reproducible with a 3% intraassay coefficient of variation (CV), and 12% interassay CV%. The CXM 3-day average was significantly correlated with BA R = 0.9, p < 0.001, RS R = 0.6, p < 0.001, SS R = 0.7, p < 0.001 and with height R = 0.7, p < 0.001. No patient with a CXM level < 5 ng/ml had remaining growth.

CONCLUSION

CXM is the first identifiable biomarker specific to longitudinal bone growth. Early results indicate that it is a patient-specific, real-time measure of growth velocity with high correlation to the established anthropometric and radiographic measures of growth. It is predictive of cessation of growth. It is highly reproducible with a low SE. Long-term follow-up is required to determine the ability of CXM to guide clinical decision-making.

Maturation and experience in action representation: Bilateral deficits in unilateral congenital amelia

Congenital unilateral absence of the hand (amelia) completely deprives individuals of sensorimotor experiences with their absent effector. The consequences of such deprivation on motor planning abilities are poorly understood. Fourteen patients and matched controls performed two grip selection tasks: 1) overt grip selection (OGS), in which they used their intact hand to grasp a three-dimensional object that appeared in different orientations using the most natural (under-or over-hand) precision grip, and 2) prospective grip selection (PGS), in which they selected the most natural grip for either the intact or absent hand without moving. For the intact hand, we evaluated planning accuracy by comparing concordance between grip preferences expressed in PGS vs. OGS. For the absent hand, we compared PGS responses with OGS responses for the intact hand that had been phase shifted by 180°, thereby accounting for mirror symmetrical biomechanical constraints of the two limbs. Like controls, amelic individuals displayed a consistent preference for less awkward grips in both OGS and PGS. Unexpectedly, however, they were slower and less accurate for PGS based on either the intact or the absent hand. We conclude that direct sensorimotor experience with both hands may be important for the typical development or refinement of effector-specific internal representations of either limb.

Can Quantitative Muscle Strength and Functional Motor Ability Differentiate the Influence of Age and Corticosteroids in Ambulatory Boys with Duchenne Muscular Dystrophy?

BACKGROUND

In the absence of a curative treatment for Duchenne Muscular Dystrophy (DMD), corticosteroid therapy (prednisone, deflazacort) has been adopted as the standard of care, as it slows the progression of muscle weakness and enables longer retention of functional mobility. The ongoing development of novel pharmacological agents that target the genetic defect underlying DMD offer hope for a significant alteration in disease progression; however, substantiation of therapeutic efficacy has proved challenging. Identifying functional outcomes sensitive to the early, subtle changes in muscle function has confounded clinical trials. Additionally, the alterations in disease progression secondary to corticosteroid therapy are not well described making it difficult to ascertain the benefits of novel agents, often taken concurrently with corticosteroids.

OBJECTIVE

The purpose of this study was to examine outcome responsiveness to corticosteroid therapy and age at the onset of a natural history study of ambulatory boys with DMD.

METHODS

Eighty-five ambulatory boys with DMD (mean age 93 mo, range 49 to 180 mo) were recruited into this study. Fifty participants were on corticosteroid therapy, while 33 were corticosteroid naïve at the baseline assessment. Within each treatment group boys were divided in two age groups, 4 to 7 years and 8 and greater years of age. The Biodex System 3 Pro isokinetic dynamometer was used to assess muscle strength. Motor skills were assessed using the upper two dimensions (standing/walking, running & jumping) of the Gross Motor Function Measure (GMFM 88) and Timed Motor Tests (TMTs) (10-meter run, sit to stand, supine to stand, climb 4-stairs). Two way analysis of variance and Pearson correlations were used for analysis.

RESULTS

A main effect for age was seen in select lower extremity muscle groups (hip flexors, knee extensors and ankle dorsiflexors), standing dimension skills, and all TMTs with significantly greater weakness and loss of motor skill ability seen in the older age group regardless of treatment group. Interaction effects were seen for the walking, running, and jumping dimension of the GMFM with the naïve boys scoring higher in the younger group and boys on corticosteroid therapy scoring higher in the older group. The TMT of climb 4-stairs demonstrated a significant treatment effect with the boys on corticosteroid therapy climbing stairs faster than those who were naïve, regardless of age. Examination of individual items within the upper level GMFM dimensions revealed select motor skills are more informative of disease progression than others; indicating their potential to be sensitive indicators of alterations in disease progression and intervention efficacy. Analysis of the relationship between muscle group strength and motor skill performance revealed differences in use patterns in the corticosteroid versus naïve boys.

CONCLUSION

Significant muscle weakness is apparent in young boys with DMD regardless of corticosteroid treatment; however, older boys on corticosteroid therapy tend to have greater retention of muscle strength and motor skill ability than those who are naive. Quantification of muscle strength via isokinetic dynamometry is feasible and sensitive to the variable rates of disease progression in lower extremity muscle groups, but possibly most informative are the subtle changes in the performance characteristics of select motor skills. Further analysis of longitudinal data from this study will explore the influence of corticosteroid therapy on muscle strength and further clarify its impact on motor performance.

Surgical outcomes for spinal deformity in osteogenesis imperfecta

STUDY DESIGN

IRB approved retrospective review of the the SHOnet (Shriners Health Outcomes Network).

OBJECTIVES

Osteogenesis imperfecta (OI) is the most prevalent genetic disorder of bone and connective tissue in the pediatric population, with an incidence of 1/15,000-20,000. Scoliosis has been reported to be present in 39-100% of OI patients and may continue to progress into adulthood but there is little information on the perioperative outcomes, rates of revision surgery and complications in this fragile population. The purpose of this study is to examine the prevalence of scoliosis in the OI population across a tertiary care multihospital system. The rate at which these patients progress to surgery, the perioperative complication rate and if there is an association between complications and age at surgical intervention, pre-operative Cobb angle, number of fractures, and type of OI. Incidence of scoliosis in OI may be lower than previously reported, many may never require surgical intervention and those that do require surgical intervention have an 8% reoperation rate at an average of 3.3 years postop.

METHODS

IRB approved retrospective review of the the SHOnet (Shriners Health Outcomes Network), electronic health record data warehouse from January 1, 2011 and December 31, 2017. Inclusion criteria included International Classification of Diseases (ICD) code for osteogenesis imperfecta and scoliosis. The data warehouse was queried for age, gender, presence of vertebral body fractures, proximal junctional kyphosis, basilar invagination, bisphosphonate use, and perioperative complications including postoperative infection.

RESULTS

There were 2372 patients with osteogenesis imperfecta, 429 or 18.1% also had a diagnosis of scoliosis, while 81.9% did not (see Table 1). Only 74 patients (17.2%) of the patients that had scoliosis underwent spine surgery, 12 of which had staged surgery with an average preop thoracic Cobb 58.18 (range 7-115), and thoracolumbar Cobb 59.83 (range 5-145). Six patients (8%) required revision spine surgery. Average time to revision was 3.88 years (6.9-69mo). Bisphosphonate use was present in 35.5% of patients that did not require surgery and in 40.5% that did.

CONCLUSION

With over 2300 patients, this is the largest study to date on scoliosis in patients with OI. We found that contrary to prior studies which had indicated the incidence of scoliosis ranges from 39 to 100% that it was only present in 18% of our patients. This indicates that the incidence of scoliosis in OI is potentially lower than previously reported, though due to the nature of this study it may be underreported. Furthermore, only 17% of those patients in our study with scoliosis eventually underwent surgery. It is important to note that many patients treated non-operatively had deformity within the operative range, which may indicate that they were not considered good candidates for surgical intervention. Lastly, we found that bisphosphonate use did not appear to affect the likelihood of progression to surgery in this group of patients, though this may be due to later initiation of the bisphosphonate use.

The role of free radical scavengers, inhibitors of prostaglandin synthesis, and hypomethylating agents in reactivation of latent herpes simplex virus

Reactivation of herpes simplex virus (HSV) was assumed to be dependent on prostaglandin synthesis [Kurane et al. (1984) J Gen Virol 65:1665-1674]. Since free radicals are generated in the course of prostaglandin synthesis and inhibitors of prostaglandin synthesis are free radical scavengers, the question arose whether free radicals are most important in viral reactivation. Therefore, the influence of five different inhibitors of prostaglandin synthesis was compared with the activity of two combinations of classical radical scavengers. Since the efficiency of both groups of compounds was similar, the role of free radicals in viral reactivation was strongly assumed, whereas the role of prostaglandins has to be revisited. All drugs tested were effective in the early phase after explantation of the latently infected ganglia and could be omitted in the later stages of co-cultivation. As free radicals are suspected of activating nuclear factors, it was of interest to confirm the enhancement of HSV reactivation by DNA hypomethylating drugs. 5-Azazytidine proved to be more effective than dimethylsulfoxide (DMSO). The effect of combinations of DMSO with inhibitors of prostaglandin synthesis was dependent on the mode of action of the inhibitors.

The SHOnet learning health system: Infrastructure for continuous learning in pediatric rehabilitation

Introduction

To describe the development and implementation of learning health system (LHS) infrastructure for a pediatric specialty care health system to support LHS research in pediatric rehabilitation settings.

Methods

An existing pediatric common data model (eg, PEDSnet) of standardized medical terminologies for research was expanded and leveraged for this stud, and applied to SHOnet, a clinical research data resource consisting of deidentified data extracted from the electronic health record (EHR) from the Shriners Hospitals for Children speacialty pediatric health care system. We mapped EHR data for laboratory, procedures, drugs, and conditions to standardized vocabularies including ICD-10, CPT, RxNorm, and LOINC to the common data model using an established extraction-transformation-loading process. Rigorous quality checks were conducted to ensure a high degree of data conformance, completeness, and plausibility. SHOnet data elements from all sources are de-identified and the server is managed by the SHC Information Systems Department. SHOnet data are refreshed monthly and data elements are continually expanded based on new research endeavors.

Interventions

Not applicable.

Results

The Shriners Health Outcomes Network (SHOnet) includes data for over 10 000 distinct observational data elements based on over two million patient encounters between 2011 and present.

Conclusion

The systematic process to develop SHOnet is replicable and flexible for other pediatric rehabilitation research settings interested in building out their LHS capabilities. Challenges and facilitators may arise for building such LHS infrastructure for rehabilitation in areas of (a) data capture, curation, query, and governance, (b) generating knowledge from data, and (c) dissemination and implementation of new institutional knowledge. Further research studies are needed to evaluate these data resources for scalable system-learning endeavors.SHOnet is an exemplar of an LHS for rehabilitation and specialty care settings. The success of an LHS is dependent on engagement of multiple stakeholders, shared governance, effective knowledge translation, and deep commitment to long-term strategies for engaging clinicians, administration, and families in leveraging knowledge to improve clinical outcomes.

Longitudinal changes in energy cost during walking in boys with Duchenne Muscular Dystrophy (DMD)

BACKGROUND

In boys with DMD, muscle weakness progresses in a proximal to distal pattern, leading to compensatory gait strategies, including hyperlordosis and equinus, that increase energy cost and accelerate the loss of walking capacity.

RESEARCH QUESTION

The purpose of this study was to determine the changes in the energy cost of walking that occur with disease progression and to determine the optimal normalization scheme for the longitudinal assessment of the energy cost of walking in boys with DMD.

METHODS

Energy cost was assessed with the COSMED K4b². Three normalization schemes were examined: gross energy cost (EC), net non-dimensional oxygen cost (NNcost) and speed-matched control energy cost (SMC-EC). Nonlinear mixed modeling procedures determined the rate of change with age. Linear regression was used to asses the relationship between each normalization scheme and age and body height.

RESULTS

74 boys with DMD were assessed for the energy cost of walking. Velocity decreased at a significant rate (-.00245/month, p = .03) across time; (Fig. 2), while gross EC (.003248/month, p = 0.0026), NNcost (.006155/month, p < 0.0001) and SMC-EC (.001690/month, p = 0.03) all increased significantly. Age and height were significantly associated with NNcost and SMC-EC. The sensitivity of NNcost and SMC-EC to age over time were similar, while SMC-EC was less sensitive to changes in height over time than NNcost.

SIGNIFICANCE

In contrast to able-bodied peers, boys with DMD decrease their velocity while all walking energy cost measures increased over time. Both SMC-EC and NNcost proved appropriate normalization schemes for boys with DMD. Compared to gross EC, both NNcost and SMC-EC were less sensitive to changes in age over time, while SMC-EC was less sensitive to changes in height than NNcost. Therefore, both NNCost and SMC-EC are suggested normalization schemes for the longitudinal assessment of energy cost in boys with DMD.

The incidence of avascular necrosis in children with cerebral palsy after hip containment surgery

PURPOSE

To establish the rate of avascular necrosis after hip reconstruction surgery in children with cerebral palsy and to identify risk factors that influence the development of avascular necrosis in this population.

METHODS

An institutional review board-approved retrospective review was conducted on children with cerebral palsy who underwent hip containment surgery at a single institution. Radiographs were evaluated at three time points. The Reimer's migration percentage, neck shaft angle, epiphyseal shaft angle, acetabular index, center edge angle, and acetabular angle were measured. The presence of avascular necrosis was evaluated and graded by the Bucholz/Ogden and the Kalamchi/MacEwen classification systems. Multivariate logistic regression was performed to identify risk factors associated with the development of avascular necrosis.

RESULTS

A total of 154 children with cerebral palsy underwent hip containment surgery on 223 hips. Twenty-nine children (18.8%) underwent both pelvic and femoral procedures; 36 children (23.4%) had only femoral procedures; 47 children (30.5%) had femoral and soft tissue; and 42 children (27.3%) had pelvic, femoral, and soft tissue procedures. Using the Bucholz and Ogden or the Kalamchi classifications, the rate of avascular necrosis was 24.7% (38/154). Of the variables evaluated, preoperative Reimers was found to be significant predictors of avascular necrosis. The rate of avascular necrosis was 26.7% for Gross Motor Functional Classification System level III, 24.1% for Gross Motor Functional Classification System level IV, and 27.3% for Gross Motor Functional Classification System level V.

CONCLUSION

The overall rate of avascular necrosis in children undergoing hip containment surgery was 26.7%. Together, age at surgery, open reduction, previous surgery, preoperative Reimers, and estimated blood loss contributed to the development of postoperative avascular necrosis; however, only preoperative Reimers significantly contributed to the development of avascular necrosis in children with cerebral palsy undergoing hip containment procedures.

Validation of Parental Reports in Assessing Idiopathic Toe Walking Using Quantitative In-Shoe Device Measurements

BACKGROUND

Toe walking is prevalent among children, affecting 5% to 24% of the pediatric population. Clinicians rely on parental reports of frequency of toe walking to guide clinical decision making and outcomes assessment. However, recall accuracy and differing environments challenge the reliability of parental reports. This study aims to validate parental reports against quantitative in-shoe device measurements (NURVV/RUN).

METHODS

Twenty children with persistent idiopathic toe walking (ITWp) (mean age: 9.6y; 13 males, 7 females) from 8 pediatric orthopaedic specialty care sites participated in this multicenter study. Parents assessed toe walking frequency using a 6-point scale, while children wore NURVV/RUN insoles for 8 hours/day over 7 days. Insole sensors recorded foot strike patterns (rearfoot, midfoot, and forefoot), which were classified using the same severity scale. Agreement between parental reports and NURVV data was assessed using weighted Kappa statistics (P<0.05).

RESULTS

Before intervention, children with ITWp exhibited daily walking patterns: 61.7% forefoot, 15.3% midfoot, and 22.8% hindfoot contact. Agreement analysis showed substantial agreement (k=0.688, P<0.001) for combined forefoot and midfoot contacts and fair agreement (k=0.381, P<0.005) for isolated forefoot contact.

CONCLUSION

Parental reports of toe walking prevalence in their children are relatively accurate, supporting their use in clinical management. However, quantitative in-shoe devices provide a more objective and quantitative understanding of ITWp frequency and have the potential to guide clinical decision-making and outcomes assessment children with ITWp.

LEVEL OF EVIDENCE

Level II-diagnostic study. See instructions to authors for a complete description of levels of evidence.

The Effects of Lower Extremity Rotational Malalignment on Pediatric Patient-reported Outcomes Measurement and Information System (PROMIS) Scores

BACKGROUND

There is sparse literature demonstrating the relationship between lower limb pediatric idiopathic rotational malalignment (IRM) and patient-reported outcomes measurement information system (PROMIS) scores. Our goal is to determine and quantify the amount that IRM deformities, as measured with the 3D gait analysis, affect childrens' pain interference, mobility, and peer relationship PROMIS domains. Secondary outcomes include investigating the potential relationships between IRM and various subgroups (Pediatric Outcomes Data Collection Instrument (PODCI), gender, Body Mass Index (BMI), femur Versus tibia). We also examine whether the PROMIS domains correlate with PODCI in this population.

METHODS

This study was a retrospective cohort, single institution, and consecutively recruited cases series. We identified 47 children over a 3-year period who were evaluated at the motion analysis center at our tertiary care hospital, with increased torsion of the femur or tibia. After exclusions, 25 children with IRM, documented PROMIS data and gait analysis were considered.

RESULTS

Femoral malrotation had a significant relationship with female gender ( P =0.001) and increased BMI ( P <0.001). Femoral malrotation had a correlation with PROMIS pain interference ( P =0.016), whereas tibial rotation did not achieve significance ( P =0.084). In the ANOVA regression analysis, there was a strong prediction of the PROMIS mobility domain when both malrotation and pain interference were present ( P =0.007). There were Pearson Correlations of PROMIS and PODCI domains for Mobility Versus Sports ( P =0.007) and Pain Interference Versus Comfort/Pain ( P =0.004), respectively.

CONCLUSION

The evident relationship between lower limb rotational malalignment and PROMIS scores signifies the likelihood for gait and pain disturbance. This in turn could show us that children are likely to be more debilitated and thus may benefit from timely correction. We aim to conduct this as a multicentre trial to confirm our findings.

LEVEL OF EVIDENCE

Level IV.

The Effect of Knee Height Asymmetry on Gait Biomechanics

BACKGROUND

Though the primary goal for limb length discrepancy (LLD) management is to equalize the leg lengths, symmetry between corresponding long bones is usually not achieved, leading to knee height asymmetry (KHA). To date, there is minimal information on what effect KHA has on gait biomechanics and joint loading. Thus, the purpose of this study is to determine the impact of KHA on gait biomechanics.

METHODS

Seventeen subjects with KHA after limb equalizing surgery and 10 healthy controls were enrolled. Subjects participated in 3D gait analysis collected using self-selected speed. Lower extremity kinematics, kinetics, work generated/absorbed, and total work were calculated. Standing lower limb x-rays and scanograms were used to measure LLD and calculate the tibia-to-femur (TF) ratio for each limb. Two sample t tests were used to compare differences in standing LLD, TF ratio, and work between groups. Bivariate correlation using Pearson correlation coefficients was conducted between TF ratio and total mechanical work, as well as between knee height asymmetry indices and total work asymmetry (α=0.05).

RESULTS

Among participants, there were no differences between LLD; however, there were differences between TF ratio and knee height asymmetry. We found a nonsignificant relationship between TF ratio and total mechanical work for individual lower extremities. Therefore, the length of individual bones (TF ratio) relative to each other within the individual lower extremity was not associated with the amount of work produced. However, when a difference exists between sides (asymmetry, ie, TF ratio asymmetry), there were associated differences in work (work asymmetry) produced between sides (r=0.54, P =0.003). In other words, greater knee height asymmetry between limbs resulted in more asymmetrical mechanical work during walking.

CONCLUSIONS

These findings may have implications for the management of LLD. Asymmetrical total mechanical work could lead to atypical joint loading during gait. Surgeons may want to consider prioritizing achieving knee height symmetry as a postoperative goal when correcting limb length discrepancy.

LEVEL OF EVIDENCE

Level III, Case Control Study.