Anatomical leg length discrepancy in children: Can it be accurately determined using 3-D motion capturing?

BACKGROUND: Leg length discrepancy (LLD) is common in youth and is cause by several conditions. Long leg X-rays is the gold standard technique of measuring LLD. It is highly accurate and reliable compared to clinical method, but expose the subject to radiation. Instrumented Gait Analysis (IGA) serves not only as a means to measure joint kinematics during gait but also as a valuable tool for assessing Leg Length Discrepancy (LLD) while standing. RESEARCH QUESTION: The purpose of this study was to compare different methods of determining the LLD in paediatric population. We hypothesize that IGA using joint centres is more accurate and precise than the tape measurement. METHODS: Thirty-one patients with mean age 12.3 (SD=2.4) years were retrospectively included in the study. Their LLD varied between 0 and 36 mm. Three methods for determining LLD were compared to radiography using Bland-Altman analysis: 1. Tape measurement, 2. IGA, summarizing the distance from the spina iliaca anterior superior to the medial malleolus marker via the medial knee condyle marker. 3. IGA, summarizing distances between ankle, knee, and hip joints centres where the latter is calculated with different equations. RESULTS: The IGA joints method performed better than the tape measurement or IGA markers method. The equations of Davis calculating the hip joint centre had the highest accuracy with mean difference to radiography of 0.7 mm (SD=6.3). The simple Harrington method resulted in a slightly reduced accuracy but higher precision 0.9 mm (SD=6.2). The Harrington method with leg length as input was less accurate 1.0 mm (SD=6.7), but was still considerably better than the tape measurement 1.8 mm (SD=7.0) or IGA markers method 1.1 mm (SD=11.5). SIGNIFICANCE: Determining LLD with IGA using the distances between ankle, knee and hip joints centres is a feasible method that can be applied in clinical practice to calculate LLD.

Frontal plane knee moment in clinical gait analysis: A systematic review on the effect of kinematic gait changes.

INTRODUCTION: The frontal plane knee moment (KAM1 and KAM2) derived from non-invasive three-dimensional gait analysis is a surrogate measure for knee joint load and of great interest in clinical and research settings. Many aspects can influence this measure either unintentionally or purposely in order to reduce the knee joint load to relieve symptoms and pain. All these aspects must be known when conducting a study or interpreting gait data for clinical decision-making. METHODS: This systematic review was registered with PROSPERO (CRD42020187038). Pubmed and Web of Science were searched for peer-reviewed, original research articles in which unshod three-dimensional gait analysis was undertaken and KAM1 and KAM2 were included as an outcome variable. Two reviewers independently screened articles for inclusion, extracted data and performed a methodological quality assessment using Downs and Black checklist. RESULTS: In total, 42 studies were included. Based on the independent variable investigated, these studies were divided into three groups: 1) gait modifications, 2) individual characteristics and 3) idiopathic orthopedic deformities. Among others, fast walking speeds (1) were found to increase KAM1; There were no sex-related differences (2) and genu valgum (3) reduces KAM1 and KAM2. CONCLUSION: While consistent use of terminology and reporting of KAM is required for meta-analysis, this review indicates that gait modifications (speed, trunk lean, step width), individual characteristics (body weight, age) and idiopathic orthopedic deformities (femoral or tibial torsion, genu valgum/varum) influence KAM magnitudes during walking. These factors should be considered by researchers when designing studies (especially of longitudinal design) or by clinicians when interpreting data for surgical and therapeutic decision-making.

Is there a correlation between static radiographs and dynamic foot function in pediatric foot deformities?

BACKGROUND: Idiopathic flexible flatfeet, congenital clubfeet and pes cavovarus are the most common foot deformities in children. Accurate assessment to quantify the severity of these deformities by clinical examination alone can be challenging. Radiographs are a valuable adjunct for accurate diagnosis and effective treatment. However, static radiographs during relaxed standing may not reflect the dynamic changes in the foot skeleton during functional activities such as walking. Therefore, the aim of this study is to predict dynamic foot movements during walking from planar standing radiographs to reveal the significance of the radiographic analysis for the assessment of foot function. METHODS: Patients 8-17 years with flexible flatfeet (FFF, n=217) recurrent clubfeet (RCF n=38) and overcorrected clubfeet (OCCF, n=71) of non-neurogenic or syndromic origin and pes cavovarus due to peripheral neuropathy (PNP, n=48) were retrospectively included. Patients underwent gait analysis with the Oxford Foot Model and radiographic examination in anterior-posterior and lateral view during standing. Multilinear predictor analysis of selected gait parameters was performed based on radiographic measures. RESULTS: The variance that was explained by radiography was greatest for the transverse plane forefoot abduction with 33% for OCCF, 50% for RCF and 59% for PNP. Flatfeet and foot kinematics in the other planes or between rearfoot and tibia showed little or no relation. CONCLUSIONS: The static measures of foot deformities by radiography could explain only a small amount of variance in foot kinematics during walking, in particular for FFF. An explanation may be that the forces during weight bearing bear little resemblance to those during gait in terms of neither magnitude nor direction. These findings suggest that foot function cannot be accurately assessed solely from static radiographic observations of the foot, commonly undertaken in clinical practice.

Cluster analysis to identify foot motion patterns in children with flexible flatfeet using gait analysis-A statistical approach to detect decompensated pathology?

INTRODUCTION: The paediatric flexible flatfoot constitutes the major cause of clinic visits for orthopaedic foot problems. It shows variations of deformities in different planes and locations of the foot and its indication for treatment have been extensively discussed. Despite its high prevalence there exists no classification of flatfeet during walking as a prerequisite for treatment decision. Therefore, the aim of this study is to classify flexible flatfeet based on 3D foot kinematics during walking. METHODS: Patients age 7-17 years with flexible flatfeet (N = 129, 255 feet) of non-neurogenic or syndromic origin, were retrospectively included. Patients underwent gait analysis using the Oxford Foot Model after standard clinical examination. A k-means cluster analysis was performed on 3 scores derived from the principal component analysis of the foot kinematic waveforms over the gait cycle. Gait and clinical parameters were then statistically tested between clusters. RESULTS: Cluster analysis revealed two groups of flexible flatfeet that were discriminated best by the inversion at push-off during walking. Cluster 2, including 110 feet, showed an average eversion instead of an inversion at push-off and a lower number of heel rises in the clinical test. Both was significantly different between clusters (p < 0.001). DISCUSSION: Based on the findings, the resultant clusters can be interpreted as describing compensated and decompensated feet, with the latter presenting a group that may require surgical interventions, even if they are not yet present with pain. The hindfoot inversion capability at push-off is the most important variable in the 3D gait analysis to classify flexible flat feet.