Eric Desailly

Foot contact event detection using kinematic data in cerebral palsy children and normal adults gait

Initial contact (IC) and toe off (TO) times are essential measurements in the analysis of temporal gait parameters, especially in cerebral palsy (CP) gait analysis. A new gait event detection algorithm, called the high pass algorithm (HPA) has been developed and is discussed in this paper. Kinematics of markers on the heel and metatarsal are used. Their forward components are high pass filtered, to amplify the contact discontinuities, thus the local extrema of the processed signal correspond to IC and TO. The accuracy and precision of HPA are compared with the gold standard of foot contact event detection, that is, force plate measurements. Furthermore HPA is compared with two other kinematics methods. This study has been conducted on 20 CP children and on eight normal adults. For normal subjects all the methods performed equally well. True errors in HPA (mean+/-standard deviation) were found to be 1+/-23 ms for IC and 2+/-25 ms for TO in CP children. These results were significantly (p<0.05) more accurate and precise than those obtained using the other algorithms. Moreover, in the case of pathological gaits, the other methods are not suitable for IC detection when IC is flatfoot or forefoot. In conclusion, the HPA is a simple and robust algorithm, which performs equally well for adults and actually performs better when applied to the gait of CP children. It is therefore recommended as the method of choice.

The convex wrapping algorithm: a method for identifying muscle paths using the underlying bone mesh.

Associating musculoskeletal models to motion analysis data enables the determination of the muscular lengths, lengthening rates and moment arms of the muscles during the studied movement. Therefore, those models must be anatomically personalized and able to identify realistic muscular paths. Different kinds of algorithms exist to achieve this last issue, such as the wired models and the finite elements ones. After having studied the advantages and drawbacks of each one, we present the convex wrapping algorithm. Its purpose is to identify the shortest path from the origin to the insertion of a muscle wrapping over the underlying skeleton mesh while respecting possible non-sliding constraints. After the presentation of the algorithm, the results obtained are compared to a classically used wrapping surface algorithm (obstacle set method) by measuring the length and moment arm of the semitendinosus muscle during an asymptomatic gait. The convex wrapping algorithm gives an efficient and realistic way of identifying the muscular paths with respect to the underlying bones mesh without the need to define simplified geometric forms. It also enables the identification of the centroid path of the muscles if their thickness evolution function is known. All this presents a particular interest when studying populations presenting noticeable bone deformations, such as those observed in cerebral palsy or rheumatic pathologies.

Proximal femoral osteotomy in neurologic pediatric hips using the locking compression plate.

Background Proximal femoral osteotomy (PFO) is a widely performed reconstructive surgery in pediatric patients with diagnosis of neurologic abnormalities. Many implants have been used for the fixation of these osteotomies. These devices have been evolved to provide stable fixation. A novel fixation system, the proximal femoral locking compression plate (LCP), which has a low lateral profile system, has been developed to address the problem of loosening in the osteoporotic bone, and to reach a more precise angular reduction and fixation stability through the use of locking screws. In this study, we report the surgical technique and results of PFO in children with a neurologic diagnosis. Methods Fifty-two children with a primary neurologic diagnosis had a femoral osteotomy with the LCP device. Clinical records and radiographs, neck-shaft angle (NSA), acetabular slope, the Reimer migration percentage, and healing of the osteotomy site were studied. Among the 70 operated hips, 59 operated hips had a follow-up superior to 1 year and were included in this study. Results Among the 59 operated hips, 25 operated hips presented with subluxations. NSA improved from 145 degrees (130 degrees to 165 degrees) to 120 degrees (110 degrees to 125 degrees) and to 125degrees (115 degrees to 130 degrees) on last follow-up. The Reimer migration percentage improved from 60% (35% to 90%) to 25% (15% to 35%). Ten operated hips presented with dislocations. Their NSA improved from 150 degrees (145 degrees to 170 degrees) to 122 degrees (115 degrees to 125 degrees) and to 125 degrees (118 degrees to 130 degrees) at last follow-up. The stability of the operative reduction was maintained and full range of motion was preserved. Five operated hips presented with dysplastic hips with NSA>130 degrees without associated subluxation, 6 operated hips presented with windswept deformities, 10 operated hips presented with excessive femoral anteversion, and 3 operated hips presented with pseudarthrosis after earlier PFO were also treated and neither presented angular loosening at last follow-up. No major complications were observed. Conclusions The LCP system may be used for a wide range of indications if precise preoperative planning was achieved. Rigid primary fixation allows early mobilization and weight bearing in ambulant patient. Level of Evidence Level IV Therapeutic study investigating the results of a treatment studying a case series.

Dual-tasking postural control in patients with right brain damage

The control of dual-tasking effects is a daily challenge in stroke neurorehabilitation. It maybe one of the reasons why there is poor functional prognosis after a stroke in the right hemisphere, which plays a dominant role in posture control. The purpose of this study was to explore cognitive motor interference in right brain-lesioned and healthy subjects maintaining a standing position while performing three different tasks: a control task, a simple attentional task and a complex attentional task. We measured the sway area of the subjects on a force platform, including the center of pressure and its displacements. Results showed that stroke patients presented a reduced postural sway compared to healthy subjects, who were able to maintain their posture while performing a concomitant attentional task in the same dual-tasking conditions. Moreover, in both groups, the postural sway decreased with the increase in attentional load from cognitive tasks. We also noticed that the stability of stroke patients in dual-tasking conditions increased together with the weight-bearing rightward deviation, especially when the attentional load of the cognitive tasks and lower limb motor impairments were high. These results suggest that stroke patients and healthy subjects adopt a similar postural regulation pattern aimed at maintaining stability in dual-tasking conditions involving a static standing position and different attention-related cognitive tasks. Our results indicate that attention processes might facilitate static postural control.

Description and classification of the effect of hamstrings lengthening in cerebral palsy children multi-site surgery.

The purpose of multi-site surgery is to improve the cerebral palsy children’s gait by associating multiple surgeries on the same therapeutic time. It is therefore complex to isolate the effect of these actions in this multifocal context. To address this problem we chose to specifically identify the effect of hamstrings lengthening (Chang 2004) in cerebral palsy children with crouch gait. The purposes of this study were as follows:

Rectus femoris transfer and musculo-skeletal modeling: Effect of surgical treatment on gait and on rectus femoris kinematics

Spasticity of the rectus femoris (RF) is one of the possible causes of stiff knee gait (SKG) in cerebral palsy. Musculoskeletal studies have shown that in SKG, length and speed of the RF are affected. No evaluation had been made to quantify the modifications of those parameters after surgery. The effect of this operation on gait quality and on RF kinematics was assessed in this study in order to identify kinematic patterns that may aid its diagnosis. For 26 transfers, clinical gait analysis pre- and post-surgery was used to compute the Gait Deviation Index (GDI) and Goldbergs index. The kinematics of the Original RF path (ORFp) was studied before and after surgery. The expression ORFp was chosen to avoid any confusion between this modeling parameter, whose computation was unchanged, and the actual anatomical path that was modified by surgery. The gait quality was improved (+18±12GDI) and there was an inverse relation between the pre-operative GDI and its improvement. The Golbergs index was improved (88% of the cases). The operation had a significant effect on the normalization of the timings of maximum length and speed of the ORFp. The improvement of SKG was correlated with the normalization of the timing of the ORFps maximum length. The global improvement of the gait quality and of the SKG was demonstrated. Some parameters of muscular kinematics (RF length and velocity) have been standardized, showing an effect of the transfer not only during the swing, but also during stance. The premature timing of the ORFp peak length has been identified as a prognostic factor of a successful surgical outcome.

Simulation of muscle retraction in cerebral palsy. Validation of a decision support system for surgical lengthening of contractured muscles

Musculoskeletal modelling associated with gait analysis permits modelling of the muscle lengths during walking. This helps to exclude indication of a hamstrings lengthening by the objectification of a non-functional impact on a supposed muscular contracture (Arnold et al. 2006). It does not allow the establishment of a positive diagnosis of the indication of hamstrings lengthening. That iswhywedeveloped a customisablemusculoskeletalmodel able to analyse the muscles kinematics during walking and to simulate the maximum muscle length from clinical goniometric measurements (simulation of muscle retraction in cerebral palsy, SiMusCP). This connection introduces a new diagnostic approach, theoretically exhaustive, of the possible causality of muscle contracture on CP children gait impairments. The purpose of this study was to evaluate the real contribution of the SiMusCP procedure in the therapeutic decision.

Does patella lowering improve crouch gait in cerebral palsy? Comparative retrospective study

BACKGROUND Patella lowering aims to improve quadriceps function as a means of correcting crouch gait in patients with cerebral palsy. Few studies have assessed the effects of patella lowering as a component of multilevel surgery. HYPOTHESIS Including patella lowering into the components of multilevel surgery is beneficial in patients with crouch gait and patella alta. MATERIAL AND METHODS In 12 lower limbs with patella alta (Caton-Deschamps index>1.4) in 41 children with cerebral palsy, patella lowering was performed, without distal femoral extension osteotomy or hamstring release. Among limbs with similar surgical procedures (e.g., hamstring lengthening, rectus femoris transfer) except for patella lowering, controls were selected retrospectively by matching on a propensity score for patella lowering. The propensity score was computed based on preoperative knee flexion contracture, knee extension lag, and minimum knee flexion at mid-stance. Clinical and 3D kinematic data were compared between the two groups. RESULTS The improvement in minimum knee flexion at mid-stance was significantly greater in the group with patellar lowering (-24°±12°vs. -12°±7°). The Gait Deviation Index improved similarly in the two groups. Knee flexion contracture improved only in the group with patellar lowering. Extension lag did not improve in either group. Peak knee flexion during the swing phase remained unchanged in both groups. DISCUSSION Patellar lowering is effective in diminishing minimum knee flexion at mid-stance in patients with patella alta and crouch gait due to cerebral palsy. Patellar lowering has not adverse effects on gait. These findings cannot be assumed to apply to patients with normal patellar height. LEVEL OF EVIDENCE IV (retrospective study).

Assessment of the effect of rectus femoris transfer by propensity score matching in cerebral palsy

The rectus femoris transfer (RFT) as any musculotendinous transfer procedure has the specificity of having only a functional objective. In the context of single event multilevel surgery, it is associated to the surgical program with the aim to improve knee kinematics during swing phase. While many indicators have been introduced to describe knee ‘stiffness’ (this word is classically used to qualify a lack of knee flexion during swing phase and is not understood in this context as the actual biomechanical stiffness of the knee joint) and thus help to clarify RFT indication, most of the clinical studies are case series. Only one study with a randomized control group (Dreher et al., 2012) was conducted and although it highlights the positive effect of RFT, the relevance of this procedure remains controversial. Our objective in order to evaluate the effect of this gesture is to carry out an observational study with the creation of a control group by Propensity Score Matching. Our research question is to determine if the RFT is efficient at improving stiff knee gait and if it have a prophylactic benefit when the knee is not stiff.

Is physical activity of children with cerebral palsy correlated with clinical gait analysis or physical examination parameters

Cerebral palsy (CP) describes a group of permanent disorders of the development of movement and posture, causing activity limitation, that are attributed to non-progressive disturbances that occurred in the developing foetal or infant brain (Rosenbaum et al. 2007). The overall prevalence of CP is 1.77 per 1000 live births. Cerebral palsy is the largest cause of motor disability in childhood (Sellier et al. 2016). The benefits of regular physical activity on health are widely recognized, especially by World Health Organization (WHO, 2010). Children with cerebral palsy practice less daily physical activity (PA) than typically developing (TD) children (Maher et al. 2007). This may affect their quality of life and may increase their impairments. This study proposes to determine the correlations between clinical gait analysis (3-DGA) and clinical examination with physical activity. The hypothesis is that correlations are not strong enough to estimate physical activity from 3-DGA or physical examination parameters.