Gait dynamics in the wide spectrum of children with arthrogryposis: a descriptive study

AMC is a group of heterogeneous disorders characterized by multiple joint contractures [ 18]; in our study, we have illustrated the diversity of gait in children with AMC, but have not been able to identify overall characteristic gait patterns in this patient population. Variations due to their individual requirements are common. We have instead tried to classify the participants into subgroups depending on need for joint stabilization, and to describe gait dynamics in their highest possible level of ambulation. Wheelchair use was reported in 12/26 children as a complement to walking, including the entire AMC1 group, which relates to previous findings of higher energy effort during walking in children with AMC [ 9]. Hip flexion contracture of less than 20°-30° and active hip motion have been reported as important factors for independent or community ambulation [ 5, 7]. None of the children in our study group had hip flexion contractures greater than 20°, and all children had hip extensor strength of grade 4–5 except two in AMC1. In a group of children walking without orthoses, excessive trunk lean and pelvic elevation have been proposed as compensation for limited hip flexion movements and strength [ 19]. In our study group hip flexion weakness was found in 6/10 limbs in AMC1. Correlation between excessive ipsilateral trunk sway and reduced internal hip abduction moment has been reported in children with AMC walking barefoot [ 12] and was attributed as a compensatory solution for weak hip abductors [ 12], as previously been reported in children with myelomeningocele [ 20]. To improve quality of gait function and achieve a more efficient gait, the importance of hip joint stability has been advocated [ 4]. None of the children in our study group had dislocated hips at the time of gait analysis, and hip surgery had been performed in seven children.

In our study group, the foot and ankle joints were most frequently involved, which is in accordance with Bevan et al. [ 3]. Different types of orthotic ankle joints were used to compensate for plantarflexor weakness and stabilize the ankle, but also according to each individual’s acceptance, resulting in the observed spectrum of dorsi/plantarflexion moments. Use of a carbon fiber spring ankle joint has been shown to increase plantarflexion moment in children with plantarflexor weakness [ 10]. Six children, distributed into AMC1 and AMC2 used orthoses with carbon fiber spring ankle joints.

A dominating attribute in AMC1 is knee extensor weakness; KAFOs with locked knee joints were therefore used to stabilize the knees. We attribute this group’s excessive frontal and transverse trunk and pelvic movements as compensatory solutions for locked orthotic knee joints to advance the leg and clear the foot during swing. This gait pattern reduces the hip abduction moments. Hip flexion moment was low, which corresponds to their lack of hip extension during late stance in combination with an exaggerated pelvic tilt. Two children in this group had hip flexion contractures and three children did not utilize their full hip extension, which might be a gait strategy when walking with bilateral locked KAFOs. Use of walkers to maintain balance has been described in children walking with locked KAFOs bilaterally [ 21]. All such children in the present study, however, preferred to walk without a walking aid. This also highlights the importance that orthoses/shoes should be tailored to compensate for each individual’s contracture. During stance, the children’s knees were restricted in a position corresponding to their knee flexion contractures of 10°–30°. Their knee extension/flexion moments are therefore entirely due to orthoses.

The main attribute in AMC2 is plantarflexor weakness and therefore KAFOs with open knee joints or AFOs were used to stabilize the ankles. Knee varus instead of valgus moment was seen in two children using AFOs, of which one had hip abductor weakness and thereby also displayed stance hip adduction moment. The treatment concept of KAFOs with open knee joints is to stabilize the knee in frontal and transversal planes while not restricting knee flexion. Both children had used KAFO-O previously but in recent years preferred AFOs. Hip flexion moment was similar to the control group but three children with less hip extension in late stance in combination with exaggerated pelvic tilt showed lower hip flexion moment. The similar knee extension/flexion moment to the control group is likely due to orthoses stabilizing the ankle joint in the sagittal plane and knee flexion contractures less than 15°.

In AMC3, hip flexion moment was similar to that of the control group despite less hip extension during late stance and greater pelvic tilt. AMC3 had considerably lower knee flexion moment during midstance than other groups, corresponding to their greater passive dorsiflexion and corresponding lack of full knee extension. They had similar ankle moments as the control group, as they walked with only shoes and included only one child with some plantarflexor weakness.

In normal gait propulsion, approximately half of the positive work in the lower limbs is provided at the ankles [ 20, 22]. In the present study, all AMC groups displayed a proximal work shift, wherein the hip contributed more than the ankle to overall positive work. This was more pronounced in those walking with orthoses and particularly locked orthotic knee joints. The work analysis demonstrates that the children rely heavily on their hip muscles, and based on their trunk movements, presumably their core muscles to provide propulsion. AMC3 furthermore, had somewhat higher total positive work than TD children, which can be attributed to higher hip moments and higher total negative work in AMC3 but a similar walking speed to TD children.

The heterogeneity among the participants regarding joint contractures, muscle weakness and different types of orthoses used in this study might seem a limitation, but as it reflects the complexity of the condition, it was unavoidable. It could be also considered a study limitation that children with AMC were tested in orthoses or shoes rather than barefoot, but this choice was made deliberately; we have collected gait data on those who could walk barefoot, but the ambulation level was often lower or nonexistent. Children in AMC1 had no walking ability without orthoses and five of the children in AMC2 had a lower ambulation level without orthoses. We therefore analyzed what we believe is their optimal and typical gait. It may have been optimal if children in the control group had also walked with shoes, as some gait parameters change slightly with shoes [ 23]. In the present study, however, the magnitude of gait parameters differences between AMC and control group were quite large, and we therefore believe there is little risk of over-interpreting small differences accounting to shoe use. It should also be noted that while we computed the GDI, we only used it to select which side to analyze. Since GDI does not incorporate upper body movements, it probably underestimates the true deviation in this population.