Balance control and lower limb joint work in children with bilateral genu valgum during level walking.

BACKGROUND: Genu valgum results in lower limb malalignment and altered joint mechanics. The study aimed to identify the effects of genu valgum on balance control and muscular work at the joints during gait in children. RESEARCH QUESTION: Would bilateral genu valgum affect balance control and muscular work at the joints during gait in children? METHODS: Thirteen children with genu valgum and thirteen healthy peers walked at their preferred speed while the body's motions and ground reaction forces were measured to calculate the inclination angles (IA) and the rates of change of IA (RCIA) of the body's center of mass (COM) relative to the center of pressure (COP), as well as the muscular work done at the joints. An independent t-test was used to compare the variables between groups (α = 0.05). RESULTS: Compared to the controls, the patients showed significantly increased step width with altered frontal IA and RCIA variables (p < 0.05), including increased average IA over single-limb support and increased peak RCIA during double-limb support (p < 0.05). The patients significantly increased posterior RCIA at heel-strike but decreased anterior RCIA at toe-off (p < 0.05). The patients showed increased muscular work at both the hip and knee during single-limb support (p < 0.05). SIGNIFICANCE: The children with genu valgum showed a specific balance control strategy during gait. In the frontal plane, greater hip and knee muscular work was needed to maintain balance under an increased IA, likely owing to increased step width associated with the valgus alignment. In the sagittal plane, less smooth and less stable COM-COP control with increased RCIA at the key gait events indicates faster weight transfer between double-limb and single-limb support. It is suggested that patients with genu valgum, especially in more severe cases, should be monitored for signs of decreased ability and/or muscular strength in maintaining balance during gait.

Whole body balance control in Lenke 1 thoracic adolescent idiopathic scoliosis during level walking.

INTRODUCTION: Altered trunk shape and body alignment in Lenke 1 thoracic adolescent idiopathic scoliosis (AIS) may affect the body's balance control during activities. The current study aimed to identify the effects of Lenke 1 thoracic AIS on the balance control during level walking in terms of the inclination angles (IA) of the center of mass (COM) relative to the center of pressure (COP), the rate of change of IA (RCIA), and the jerk index of IA. The association between the Cobb angle, IA and RCIA was also evaluated. MATERIALS AND METHODS: Sixteen adolescents with AIS (age: 14.0±1.8 years, height: 154.8±4.7 cm, mass: 42.0±7.5 kg) and sixteen healthy controls (age: 14.4±2.0 years, height: 158.4±6.2 cm, body mass: 48.6±8.9 kg) performed level walking in a gait laboratory. The kinematic and ground reaction force data were measured for both concave-side and convex-side limb cycles, and used to calculate the IA and RCIA, the jerk index of IA, and the temporal-spatial parameters. Correlations between the Cobb angle, IA and RCIA were quantified using Pearson's correlation coefficients (r). RESULTS: The patients showed less smooth COM-COP motion with increased jerk index of IA in the sagittal plane during single limb support (SLS) of the concave-limb (p = 0.05) and in the frontal plane during double limb support (DLS) (p < 0.05). The patients also showed significantly increased posterior RCIA on both the concave and convex side during initial (p = 0.04, p = 0.03) and terminal (p = 0.04, p = 0.03) DLS when compared to healthy controls. In the frontal plane, the patients walking on the concave-side limb showed decreased IA over SLS (p = 0.01), and at contralateral toe-off (p<0.01) and contralateral heel-strike (p = 0.02), but increased mean IA magnitude over terminal DLS (p = 0.01). The frontal IA at contralateral toe-off and SLS for AIS-A showed a moderate to strong correlation with Cobb angles (r = -0.46 and -0.61), and the sagittal RCIA over the initial DLS for AIS-A also showed a significant, strong correlation with Cobb angles (r = -0.50). CONCLUSIONS: The patients with Lenke 1 thoracic scoliosis in the current study showed altered and jerkier COM-COP control during level walking when compared to healthy controls. During DLS, the patients increased the posterior RCIA in the sagittal plane with increased IA jerk index in the frontal plane for both the concave- and the convex-side limb, indicating their difficulty in maintaining a smooth transfer of the body weight. During SLS of the concave-side limb, the patients adopted a conservative COM-COP control strategy, as indicated by a decreased IA in the frontal plane, but showed a jerky COM-COP control in the sagittal plane. The COM-COP control of the patients was associated with the severity of the spinal deformity. The current results suggest that this patient group should be monitored for signs of an increased risk of loss of balance during weight transfer on the concave-side limb.

Altered balance control in thoracic adolescent idiopathic scoliosis during obstructed gait.

Adolescent idiopathic scoliosis (AIS) is the most common spinal deformity during adolescence, leading to altered postural control with compromised stability. To identify the effects of AIS on whole-body balance control during obstacle-crossing, 14 adolescents with Lenke 1 thoracic AIS and 14 healthy controls were compared in terms of the inclination angle (IA) of the body's center of mass (COM) relative to the center of pressure (COP), the rate of change of IA (RCIA) and the jerk index of IA. Between-side comparisons were also performed for the AIS group. The patients showed less smooth COM-COP motion in the sagittal plane with significantly increased anterior RCIA and IA jerk index during crossing with either the concave side (p = 0.001) or the convex side (p = 0.001) leading when compared to healthy controls. In the frontal plane, the patients showed close-to-zero RCIA (p = 0.002) while crossing with the leading limb, with an increased IA magnitude (p = 0.039) only while crossing with the concave-side limb leading. The patients with Lenke 1 thoracic AIS were found to cross obstacles with altered, compromised COM-COP control in both sagittal and frontal planes when compared to healthy controls. The results suggest that the thoracic spinal deformity in Lenke 1 AIS affects the whole-body balance control during obstacle-crossing, which should be monitored for signs of increased risk of loss of balance in the management of such patient groups.

Bilateral asymmetry in kinematic strategies for obstacle-crossing in adolescents with severe idiopathic thoracic scoliosis.

INTRODUCTION: Adolescent idiopathic scoliosis (AIS) is the most common three-dimensional spinal deformity pathology during adolescence, often accompanied with sensory integration and proprioception problems, which may lead to abnormal postural control and altered end-point control during functional activities. This paper identifies the effects of AIS on the end-point control and on angular kinematics of the trunk and pelvis-leg apparatus during obstacle-crossing for both the concave- and convex-side limb leading. MATERIALS AND METHODS: Sixteen adolescents with severe Lenke 1 AIS (age: 14.9 ±â€¯1.7 years, height: 154.7 ±â€¯5.0 cm) and sixteen healthy controls (age: 14.8 ±â€¯2.7 years, height: 154.9 ±â€¯5.6 cm) each walked and crossed obstacles of 3 heights with either the concave- (AIS-A) or convex-side (AIS-V) limb leading. Angular motions of the trunk, pelvis and lower limbs, and toe-obstacle clearances were measured. Two-way analyses of variance were used to study between-subject (group) and within-subject (limb and height) effects on the variables. Whenever a height effect was found, a polynomial test was used to determine the linear trend. α = 0.05 was set for all tests. RESULTS: Patients with AIS significantly reduced pelvic downward list but increased dorsiflexion in both stance and swing ankles at leading limb crossing when compared to controls (p < 0.05). During AIS-A, additional kinematic modifications were observed, i.e., increased stance hip adduction (4.2 ±â€¯0.8°, p = 0.005) and increased swing knee flexion (12.6 ±â€¯1.4°, p = 0.106), with significantly decreased leading toe-clearance (AIS-A: 121.4 ±â€¯6.7 mm, controls: 140.1 ±â€¯5.6 mm, p = 0.031). CONCLUSIONS: Patients with AIS adopted an altered kinematic strategy for successful obstacle-crossing. With the concave-side limb leading, more joint kinematic modifications with reduced toe-clearance were found when compared to those during the convex-side limb leading, suggesting an increased risk of tripping. Further studies on the kinematic strategies adopted by different types of AIS will be needed for a more complete picture of the functional adaptations in such patient group.