Anna-Clara Esbjörnsson

Analytical decomposition can help to interpret ankle joint moment–angle relationship

Moment-angle relationship (dynamic joint stiffness)--the relationship between changes in joint moment and changes in joint angle--is useful for demonstrating interaction of kinematics and kinetics during gait. However, the individual contributors of dynamic joint stiffness are not well studied and understood, which has thus far limited its clinical application. In this study, ankle dynamic joint stiffness was analyzed and decomposed into three components in thirty able-bodied children during the stance phase of the gait. To verify the accuracy of the decomposition, the sum of decomposed components was compared to stiffness computed from experimental data, and good to very good agreement was found. Component 1, the term associated with changes in ground reaction force moment, was the dominant contribution to ankle dynamic joint stiffness. Retrospective data from eight children with juvenile idiopathic arthritis and idiopathic toe-walking was examined to explore the potential utility of analytical decomposition in pathological gait. Compared to controls, component 1 was the source of highest deviation in both pathological groups. Specifically, ankle dynamic joint stiffness differences can be further identified via two sub-components of component 1 which are based on magnitudes and rates of change of the ground reaction force and of its moment arm, and differences between the two patient groups and controls were most evident and interpretable here. Findings of the current study indicate that analytical decomposition can help identify the individual contributors to joint stiffness and clarify the sources of differences in patient groups.

PReS-FINAL-2024: Responsiveness of the juvenile arthritis foot disability index

Foot involvement is commonly described in children with JIA and management of foot disability is necessary to maximize physical function in children. The Juvenile Arthritis Foot disability Index (JAFI) is a questionnaire for assessing self-reported foot-related disability in children and adolescences with arthritis. The JAFI is a valid and reliable survey which is divided into three dimensions; impairment, activity limitations and participation restrictions (Andre 2004). However, its ability to measure change in foot related disability has not been established.

Self-rated walking disability and dynamic ankle joint stiffness in children and adolescents with Juvenile Idiopathic Arthritis receiving intraarticular corticosteroid joint injections of the foot

BACKGROUND Children and adolescents with Juvenile Idiopathic Arthritis (JIA) exhibit deviations in ankle dynamic joint stiffness (DJS, or moment-angle relationship) compared to healthy peers, but the relationship between ankle DJS and self-reported walking impairments has not been studied. This secondary analysis aimed to investigate the relationship between ankle DJS and self-reported walking disability in juveniles with JIA, and to determine whether intraarticular corticosteroid foot injections (IACI) were associated with long term changes in ankle DJS. RESEARCH QUESTIONS Is ankle DJS altered in children with JIA reporting walking difficulties compared to children with JIA reporting no walking difficulties? Are IACIs associated with persistent alterations in ankle DJS? METHODS Gait dynamics (DJS), foot pain, and foot-related disability were assessed in 33 children with JIA before intraarticular corticoid foot injection (IACI), and three months after IACI. Using self-reported walking capacity scores, children were classified as either having no walking difficulties (ND) or having walking difficulties (WD). Inferential statistics were used to compare demographics, pain, impairment scores, and ankle DJS between the groups. RESULTS Before treatment, in the WD group, ankle DJS was significantly decreased both in the early rising phase (ERP = 0.03+0.02 vs. 0.05+0.02 Nm(kg*deg)- 1) and late rising phase (LRP = 0.11+0.06 vs. 0.24+0.22 Nm(kg*deg)-1) compared to the ND group. At three months, the ERP was still significantly decreased in the WD group (ERP = 0.03+0.01 vs. 0.05+0.03 Nm(kg*deg)-1). SIGNIFICANCE Among children and adolescents with JIA who reported walking difficulties prior to IACIs, alterations in DJS in early stance phase (decreased ERP) remained three months after IACI suggesting persistent gait adaptations, possibly related to pain. Pre-treatment gait analysis may aid in identifying children who will not have long term benefit from IACIs in terms of improved gait, and therefore, may be informed and have the choice to be spared the risk of side effects associated with this treatment.

Ankle arthritis predicts worse outcome in children with juvenile idiopathic arthritis

The ankle joint is commonly involved in children with Juvenile Idiopathic Arthritis (JIA) and ankle arthritis predicts a more severe disease according to earlier studies. These studies have mainly been cross-sectional and the results are problematic to generalize to broader populations.