Julie Nantel

Locomotor strategies in obese and non-obese children.

Objective: The constant strain in obese children may increase the risks of articular problems in adulthood. In the short term, obesity in children could lead to modifications of the gait pattern. The purpose of this study was to compare biomechanical parameters between obese and non‐obese children during self‐paced walking.

Gait Patterns After Total Hip Arthroplasty and Surface Replacement Arthroplasty

OBJECTIVE To compare gait patterns in patients with total hip arthroplasty (THA) and surface hip arthroplasty. DESIGN Observational study. SETTING Outpatient biomechanical laboratory. PARTICIPANTS Two groups of 10 surface hip arthroplasty and THA patients and 10 control subjects participated in the study (N=30). The patients were volunteers recruited from a larger randomized study. INTERVENTIONS Not applicable. MAIN OUTCOMES MEASURES Gait patterns, hip abductor muscle strength, clinical outcomes, and radiographic analyses were compared between groups. RESULTS In the sagittal plane, the THA group showed a larger flexor moment and larger mechanical work in H2S and K3S power bursts compared with surface hip arthroplasty and control subjects. In the frontal plane, both THA and surface hip arthroplasty patients had smaller hip abductor muscles energy generation (H3F) than the control group. No difference was found for the hip abductor muscles strength. CONCLUSIONS In the THA group, the larger energy absorption in H2S and K3S would be a cost-effective mechanical adaptation to increase stability. The surface hip arthroplasty characteristics could allow the return to a more normative gait pattern compared with THA. The modification in the frontal plane in surface hip arthroplasty and THA would be related to the hip abductor muscles strength.

Deficits in visuospatial processing contribute to quantitative measures of freezing of gait in Parkinson’s disease

OBJECTIVES The aim of this study was to investigate whether an objective measure of freezing of gait (FOG) using a validated alternating stepping in place (SIP) task, is related to executive and/or visuospatial cognitive impairment in Parkinsons disease (PD). METHODS We studied prospectively 30 PD subjects with the Unified Parkinsons Disease Rating Scale (UPDRS) III, the FOGq, Trail Making Test Part B (TMTB), Wisconsin Card Sorting, Initiation/Perseveration, Matrix Reasoning (MR) and Block Design (BD). PD subjects performed three, 100s trials of alternative SIP while standing on two force platforms to assess the number and duration of freezing episodes (FE), SIP rhythmicity and symmetry. RESULTS Freezers had larger cycle asymmetry and arrhythmicity than non-freezers (P<0.05). Performance on BD and MR tests differentiated freezers from non-freezers (P<0.04; P=0.001, respectively). BD performance negatively correlated with the FOGq total (P<0.05), the number and duration of FE (P<0.01), SIP arrhythmicity and asymmetry (P=0.01, P<0.05). MR performance negatively correlated with all FOGq #3 and total as well as SIP FE metrics (P≤0.01), except for SIP asymmetry. CONCLUSION Deficits in visuospatial perception and reasoning not in executive function differentiated freezers from non-freezers. Deficits in visuospatial processing negatively correlated with all SIP freeze metrics, whereas deficits in executive function were only correlated with SIP arrhythmicity, the FOGq total and the duration of freezing episodes. These results suggest that deficits in visuospatial processing to perform a motor task contribute to FOG and that different cognitive deficits may contribute to different aspects of freezing in PD. This is the first study to our knowledge that has compared metrics of freezing to cognitive tasks in the visuospatial and visual reasoning domains.

Physical Activity and Obesity: Biomechanical and Physiological Key Concepts

Overweight (OW) and obesity (OB) are often associated with low levels of physical activity. Physical activity is recommended to reduce excess body weight, prevent body weight regain, and decrease the subsequent risks of developing metabolic and orthopedic conditions. However, the impact of OW and OB on motor function and daily living activities must be taken into account. OW and OB are associated with musculoskeletal structure changes, decreased mobility, modification of the gait pattern, and changes in the absolute and relative energy expenditures for a given activity. While changes in the gait pattern have been reported at the ankle, knee, and hip, modifications at the knee level might be the most challenging for articular integrity. This review of the literature combines concepts and aims to provide insights into the prescription of physical activity for this population. Topics covered include the repercussions of OW and OB on biomechanical and physiological responses associated with the musculoskeletal system and daily physical activity. Special attention is given to the effect of OW and OB in youth during postural (standing) and various locomotor (walking, running, and cycling) activities.

Center of Mass Compensation during Gait in Hip Arthroplasty Patients: Comparison between Large Diameter Head Total Hip Arthroplasty and Hip Resurfacing

Objective. To compare center of mass (COM) compensation in the frontal and sagittal plane during gait in patients with large diameter head total hip arthroplasty (LDH-THA) and hip resurfacing (HR). Design. Observational study. Setting. Outpatient biomechanical laboratory. Participants. Two groups of 12 patients with LDH-THA and HR recruited from a larger randomized study and 11 healthy controls. Interventions. Not applicable. Main Outcome Measures. To compare the distance between the hip prosthetic joint center (HPJC) and the COM. The ratio (RHPJC-COM) and the variability (CVHPJC-COM) were compared between groups. Hip flexor, abductor, and adductor muscle strength was also correlated between groups while radiographic measurements were correlated with the outcome measures. Results. In the frontal plane, HR shows less variability than healthy controls at push-off and toe-off and RHPJC-COM is correlated with the muscle strength ratios (FRABD) at heel contact, maximal weight acceptance, and mid stance. In the sagittal plane, LDH-THA has a higher RHPJC-COM than healthy controls at push-off, and CVHPJC-COM is significantly correlated with FRFLEX. Conclusions. One year after surgery, both groups of patients, LDH-THA and HR, demonstrate minor compensations at some specific instant of the gait cycle, in both frontal and sagittal planes. However, their locomotion pattern is similar to the healthy controls.

Postural Balance During Quiet Standing in Patients With Total Hip Arthroplasty With Large Diameter Femoral Head and Surface Replacement Arthroplasty

OBJECTIVE To compare postural balance between patients who have had either a large diameter head total hip arthroplasty or surface replacement arthroplasty. DESIGN Observational study. SETTING Outpatient biomechanical laboratory. PARTICIPANTS Two groups of 14 patients with surface replacement or large diameter head total hip arthroplasties recruited from a larger randomized study and 14 control subjects. INTERVENTIONS Not applicable. MAIN OUTCOME MEASURES Postural balance during quiet standing in dual and one-leg stance (operated leg), hip abductor muscle strength, clinical outcomes, and radiographic analyses were compared between groups. RESULTS Compared to the control group, patients in both groups showed smaller center of pressure displacement amplitude in the medial-lateral direction in dual stance. Patients with large diameter head total hip arthroplasty showed lower hip abductor muscle strength compared to control subjects. There was statistical difference between the 2 patient groups in biomechanical reconstruction of the hip. Despite these differences, there was no significant difference in the ability to complete the one-leg stance task between the 3 groups. CONCLUSIONS The muscular strength in the operated limb could be mainly responsible for the lower center of pressure displacement amplitude compared to control subjects. However, the ability to complete the one-leg stance demonstrates that patients do not fear to load the hip prosthesis when needed. The large diameter femoral head may be a major mechanical factor contributing to these results.