Limited trunk motion and posterior pelvic tilting in ambulatory children treated with bilateral rib to pelvis implants for spinal deformity control.

In young children, growth-friendly spinal implants with bilateral rib to pelvis fixation are used to control progressive spinal deformity. Whereas curve progression, complications and side-effects have been extensively studied in this patient population, no data are available on gait pattern changes and postural body adjustments. Our study evaluates whether gait pattern changed for ambulatory children treated with bilateral rib to pelvis implants compared to age-matched healthy children. In this small cohort study, gait analysis was performed using spatiotemporal and kinematic parameters of four ambulatory children with severe scoliosis and growth-friendly spinal implants using the bilateral rib to pelvis fixation. Data were statistically analyzed and compared to seven healthy age-matched children. Between both groups, no differences were seen in walking speed, cadence and stride length. The treated patients showed a lower range of motion of the pelvic obliquity and of the trunk obliquity and rotation, but a higher knee flexion. Growth-friendly spinal implants with bilateral rib to pelvis fixation are commonly used in wheelchair children and rarely indicated in ambulatory patients. The presented data show reduced trunk and pelvis motion using this implant construct. These findings help to understand body postural adjustments and add valuable information for families and care providers when considering this surgery. Level of evidence: Therapeutic level IV.

Long-term follow-up after multilevel surgery in cerebral palsy.

INTRODUCTION: Single-event multilevel surgery (SEMLS) is frequently used to correct pathological gait patterns in children with bilateral spastic cerebral palsy (BSCP) in a single session surgery. However, in-depth long-term evaluation reports of gait outcomes are limited. Therefore, we investigated if SEMLS is able to correct lower extremity joint and pelvic angles during gait towards typically developing gait patterns (TDC) in children with BSCP, and if so, if this effect is durable over a 10-year period. MATERIALS AND METHODS: In total 13 children with BSCP GMFCS level II at time of index-surgery between the ages of 7.7-18.2 years at the time of SEMLS were retrospectively recruited. Three-dimensional gait data were captured preoperatively, as well as at short-, mid-, and long-term post-operatively, and used to analyze: movement analysis profile (MAP), gait profile score (GPS), and lower extremity joint and pelvic angles over the course of a gait cycle using statistical parametric mapping. RESULTS: In agreement with previous studies, MAP and GPS improved towards TDCs after surgery, as did knee extension during the stance phase (ɳ2 = 0.67; p < 0.001), while knee flexion in the swing phase (ɳ2 = 0.67; p < 0.001) and pelvic tilt over the complete gait cycle (ɳ2 = 0.36; p < 0.001) deteriorated; no differences were observed between follow-ups. However, further surgical interventions were required in 8 out of 13 of the participants to maintain improvements 10 years post-surgery. CONCLUSIONS: While the overall gait pattern improved, our results showed specific aspects of the gait cycle actually deteriorated post-SEMLS and that a majority of the participants needed additional surgery, supporting previous statements for the use of multilevel surgery rather than SEMLS. The results highlight that the field should not only focus on the overall gait scores when evaluating treatment outcomes but should offer additional long-term follow-up of lower extremity function.

Impact of the Marker Set Configuration on the Accuracy of Gait Event Detection in Healthy and Pathological Subjects.

For interpreting outcomes of clinical gait analysis, an accurate estimation of gait events, such as initial contact (IC) and toe-off (TO), is essential. Numerous algorithms to automatically identify timing of gait events have been developed based on various marker set configurations as input. However, a systematic overview of the effect of the marker selection on the accuracy of estimating gait event timing is lacking. Therefore, we aim to evaluate (1) if the marker selection influences the accuracy of kinematic algorithms for estimating gait event timings and (2) what the best marker location is to ensure the highest event timing accuracy across various gait patterns. 104 individuals with cerebral palsy (16.0 ± 8.6 years) and 31 typically developing controls (age 20.6 ± 7.8) performed clinical gait analysis, and were divided into two out of eight groups based on the orientation of their foot, in sagittal and frontal plane at mid-stance. 3D marker trajectories of 11 foot/ankle markers were used to estimate the gait event timings (IC, TO) using five commonly used kinematic algorithms. Heatmaps, for IC and TO timing per group were created showing the median detection error, compared to detection using vertical ground reaction forces, for each marker. Our findings indicate that median detection errors can be kept within 7 ms for IC and 13 ms for TO when optimizing the choice of marker and detection algorithm toward foot orientation in midstance. Our results highlight that the use of markers located on the midfoot is robust for detecting gait events across different gait patterns.

Towards validation and standardization of automatic gait event identification algorithms for use in paediatric pathological populations.

BACKGROUND: To analyse and interpret gait patterns in pathological paediatric populations, accurate determination of the timing of specific gait events (e.g. initial contract - IC, or toe-off - TO) is essential. As currently used clinical identification methods are generally subjective, time-consuming, or limited to steps with force platform data, several techniques have been proposed based on processing of marker kinematics. However, until now, validation and standardization of these methods for use in diverse gait patterns remains lacking. RESEARCH QUESTIONS: 1) What is the accuracy of available kinematics-based identification algorithms in determining the timing of IC and TO for diverse gait signatures? 2) Does automatic identification affect interpretation of spatio-temporal parameters?. METHODS: 3D kinematic and kinetic data of 90 children were retrospectively analysed from a clinical gait database. Participants were classified into 3 gait categories: group A (toe-walkers), B (flat IC) and C (heel IC). Five kinematic algorithms (one modified) were implemented for two different foot marker configurations for both IC and TO and compared with clinical (visual and force-plate) identification using Bland-Altman analysis. The best-performing algorithm-marker configuration was used to compute spatio-temporal parameters (STP) of all gait trials. To establish whether the error associated with this configuration would affect clinical interpretation, the bias and limits of agreement were determined and compared against inter-trial variability established using visual identification. RESULTS: Sagittal velocity of the heel (Group C) or toe marker configurations (Group A and B) was the most reliable indicator of IC, while the sagittal velocity of the hallux marker configuration performed best for TO. Biases for walking speed, stride time and stride length were within the respective inter-trial variability values. SIGNIFICANCE: Automatic identification of gait events was dependent on algorithm-marker configuration, and best results were obtained when optimized towards specific gait patterns. Our data suggest that correct selection of automatic gait event detection approach will ensure that misinterpretation of STPs is avoided.

Walking on uneven ground: How do patients with unilateral cerebral palsy adapt?

BACKGROUND: Children with cerebral palsy experience movement disorders that influence gait stability. It is likely that gait stability further decreases when walking on uneven compared to even ground. Therefore, the aim of this study was to investigate gait on uneven ground in children with unilateral cerebral palsy. METHODS: Twenty children with unilateral cerebral palsy and twenty typically developing children performed a three-dimensional gait analysis when walking on even and uneven ground. Spatio-temporal parameters, full-body joint kinematics and centre of mass displacements were compared. FINDINGS: On uneven versus even ground, both groups showed decreased cadence, increased stance phase and double support time, increased toe clearance height, and increased knee and hip flexion during swing phase. Whereas only the typically developing children walked slower and had increased dorsiflexion and external foot progression during stance phase, only the patients showed increased stride width, increased elbow flexion (affected and non-affected side), and kept the centre of mass more medial when standing on the affected leg. INTERPRETATION: Patients and healthy children use similar adaptation mechanisms when walking on uneven ground. Both groups increased the toe clearance height by increasing knee and hip flexion during swing. However, whereas patients enlarge their base of support by increasing stride width, healthy children do so by increasing their external foot progression angle. Furthermore, patients seem to feel more insecure and hold their arms in a position to prepare for falls on uneven ground. They also do not compensate with their non-affected side for their affected side on uneven ground.

Outcome of medial hamstring lengthening in children with spastic paresis: A biomechanical and morphological observational study.

To improve gait in children with spastic paresis due to cerebral palsy or hereditary spastic paresis, the semitendinosus muscle is frequently lengthened amongst other medial hamstring muscles by orthopaedic surgery. Side effects on gait due to weakening of the hamstring muscles and overcorrections have been reported. How these side effects relate to semitendinosus morphology is unknown. This study assessed the effects of bilateral medial hamstring lengthening as part of single-event multilevel surgery (SEMLS) on (1) knee joint mechanics (2) semitendinosus muscle morphology and (3) gait kinematics. All variables were assessed for the right side only. Six children with spastic paresis selected for surgery to counteract limited knee range of motion were measured before and about a year after surgery. After surgery, in most subjects popliteal angle decreased and knee moment-angle curves were shifted towards a more extended knee joint, semitendinosus muscle belly length was approximately 30% decreased, while at all assessed knee angles tendon length was increased by about 80%. In the majority of children muscle volume of the semitendinosus muscle decreased substantially suggesting a reduction of physiological cross-sectional area. Gait kinematics showed more knee extension during stance (mean change ± standard deviation: 34±13°), but also increased pelvic anterior tilt (mean change ± standard deviation: 23±5°). In most subjects, surgical lengthening of semitendinosus tendon contributed to more extended knee joint angle during static measurements as well as during gait, whereas extensibility of semitendinosus muscle belly was decreased. Post-surgical treatment to maintain muscle belly length and physiological cross-sectional area may improve treatment outcome of medial hamstring lengthening.

Visual targeting one step before force plates has no effect on gait parameters in orthopaedic patients during level walking.

In clinical gait analysis, it is challenging to acquire usable force plate data for a patient in a limited amount of time. The aim of this study was to compare three measurement protocols, to investigate if any one of them was more time-efficient than the others at collecting kinetic data. Three conditions were compared for 15 orthopaedic patients: 1) approaching the force plate with four steps, 2) approaching the force plate with six steps, and 3) approaching the force plate with four steps while stepping on a target one step before the first force plate. Then, the following characteristics were analysed: the rate of usable force plate steps, the spatio-temporal parameters, the full-body gait kinematics, and the lower body kinetics. For the condition with four steps and targeting, the rate of usable force plate steps was highest: 84% (6.8 usable trials out of 8.1 trials on average per patient). Left hip adduction and rotation, right shoulder flexion, and total left hip power were the gait parameters with statistically significant differences between the four and six step approach. Left cadence, right step time, left thorax lateroflexion, left shoulder abduction, total right knee power, hip rotation, thorax tilt, and head tilt on both sides were statistically different between the four step approach with targeting and without targeting. None of the differences in gait parameters (except for head tilt) were of clinical relevance. Therefore, approaching the force plate with four steps and stepping on a foot-sized target one step prior to stepping on the force plate increases the rate of usable kinetic data.

Upper extremity motion during gait in adolescents with structural leg length discrepancy-An exploratory study.

BACKGROUND AND PURPOSE: Depending on the extent of a structural leg length discrepancy (LLD), several compensatory mechanisms take place in order to maintain function and to optimize energy consumption during gait. However, studies describing the influence of a structural LLD on upper limb motion are lacking. The current study therefore aimed at the evaluation of upper limb motion during gait in LLD patients compared to healthy controls. METHODS: Motion capture data from 14 patients with structural LLD and 15 healthy controls that were collected during barefoot walking at a self-selected speed were retrospectively analyzed. Specifically, kinematic parameters of the shoulder and elbow joints as well as the trunk segment were investigated and considered in relation to a minimal clinically important difference of 5°. RESULTS: The shoulders in LLD patients were kept constantly in a more extended and at initial contact in a more adducted position as compared to healthy controls. In addition, the patients' elbow joints showed increased flexion motion and the trunk segment indicated a constant trunk lateral-flexion and axial rotation tendency towards the affected side. CONCLUSIONS: Patients with structural LLD indicated clinically relevant secondary deviations in shoulder and elbow motion. While some of these deviations were most likely passive physical effects, others might have occurred as active strategies to maintain balance or to regulate total body angular momentum. These findings contribute to the understanding of secondary gait deviations induced by a structural LLD and might serve as a basis for further investigations using complex musculoskeletal models.

Knee Moment-Angle Characteristics and Semitendinosus Muscle Morphology in Children with Spastic Paresis Selected for Medial Hamstring Lengthening.

To increase knee range of motion and improve gait in children with spastic paresis (SP), the semitendinosus muscle (ST) amongst other hamstring muscles is frequently lengthened by surgery, but with variable success. Little is known about how the pre-surgical mechanical and morphological characteristics of ST muscle differ between children with SP and typically developing children (TD). The aims of this study were to assess (1) how knee moment-angle characteristics and ST morphology in children with SP selected for medial hamstring lengthening differ from TD children, as well as (2) how knee moment-angle characteristics and ST morphology are related. In nine SP and nine TD children, passive knee moment-angle characteristics and morphology of ST (i.e. fascicle length, muscle belly length, tendon length, physiological cross-sectional area, and volume) were assessed by hand-held dynamometry and freehand 3D ultrasound, respectively. At net knee flexion moments above 0.5 Nm, more flexed knee angles were found for SP compared to TD children. The measured knee angle range between 0 and 4 Nm was 30% smaller in children with SP. Muscle volume, physiological cross-sectional area, and fascicle length normalized to femur length were smaller in SP compared to TD children (62%, 48%, and 18%, respectively). Sixty percent of the variation in knee angles at 4 Nm net knee moment was explained by ST fascicle length. Altered knee moment-angle characteristics indicate an increased ST stiffness in SP children. Morphological observations indicate that in SP children planned for medial hamstring lengthening, the longitudinal and cross-sectional growth of ST muscle fibers is reduced. The reduced fascicle length can partly explain the increased ST stiffness and, hence, a more flexed knee joint in these SP children.

3D video-based deformation measurement of the pelvis bone under dynamic cyclic loading.

BACKGROUND: Dynamic three-dimensional (3D) deformation of the pelvic bones is a crucial factor in the successful design and longevity of complex orthopaedic oncological implants. The current solutions are often not very promising for the patient; thus it would be interesting to measure the dynamic 3D-deformation of the whole pelvic bone in order to get a more realistic dataset for a better implant design. Therefore we hypothesis if it would be possible to combine a material testing machine with a 3D video motion capturing system, used in clinical gait analysis, to measure the sub millimetre deformation of a whole pelvis specimen. METHOD: A pelvis specimen was placed in a standing position on a material testing machine. Passive reflective markers, traceable by the 3D video motion capturing system, were fixed to the bony surface of the pelvis specimen. While applying a dynamic sinusoidal load the 3D-movement of the markers was recorded by the cameras and afterwards the 3D-deformation of the pelvis specimen was computed. The accuracy of the 3D-movement of the markers was verified with 3D-displacement curve with a step function using a manual driven 3D micro-motion-stage. RESULTS: The resulting accuracy of the measurement system depended on the number of cameras tracking a marker. The noise level for a marker seen by two cameras was during the stationary phase of the calibration procedure ± 0.036 mm, and ± 0.022 mm if tracked by 6 cameras. The detectable 3D-movement performed by the 3D-micro-motion-stage was smaller than the noise level of the 3D-video motion capturing system. Therefore the limiting factor of the setup was the noise level, which resulted in a measurement accuracy for the dynamic test setup of ± 0.036 mm. CONCLUSION: This 3D test setup opens new possibilities in dynamic testing of wide range materials, like anatomical specimens, biomaterials, and its combinations. The resulting 3D-deformation dataset can be used for a better estimation of material characteristics of the underlying structures. This is an important factor in a reliable biomechanical modelling and simulation as well as in a successful design of complex implants.

The influence of sole wedges on frontal plane knee kinetics, in isolation and in combination with representative rigid and semi-rigid ankle-foot-orthoses.

BACKGROUND: In earlier stages of knee osteoarthritis orthotic treatments with knee orthoses or modified footwear are often considered. Although the load reducing effects of knee orthoses have been well established, wearing modified footwear would be more comfortable for the patient and less encumbering. The effect of modified footwear on the frontal load of the knee is controversial. This article describes the effect of medial or lateral shoe wedges alone or together with two different types of ankle-stabilizing orthoses. METHODS: The effect on frontal knee loading was measured during standing and walking with medially and laterally placed wedges under the sole of the shoe. The wedges were also combined with two types of orthotic devices - an Ankle-Foot-Orthosis that was rigid in the frontal plane but allowed unrestricted sagittal plane motion and an ankle support that was semi-rigid in the frontal plane. Joint loading of 10 healthy persons (mean (standard deviation): age 34 (9) years, height 178 (4)cm, mass 73 (9)kg) was investigated by means of a special measuring device that accurately determines static loads (Lasar Posture) and with instrumented gait analysis (Vicon/Kistler). FINDINGS: Using a lateral wedge under the sole of the shoe (without orthotic support) showed no significant reduction in the mean maximal knee moment in the frontal plane. Adding an Ankle-Foot-Orthosis that is rigid in the frontal plane resulted in significant reduction in the maximal frontal moment from 0.54 Nm/kg to 0.38Nm/kg (p0.01). Using a medial wedge, without and with Ankle-Foot-Orthosis, produced a significant increase in the maximal frontal moment to 0.59 Nm/kg (p0.05) or 0.67 Nm/kg (p0.01), respectively. INTERPRETATION: These results suggest that the application of a sole wedge significantly influences frontal knee loading when used in combination with an Ankle-Foot-Orthosis that is rigid in the frontal plane.