Table 1.
Anthropometric and subject data ± standard deviation (range) and number of previous treatments with Botulinum toxin A.
Fig 1.
Setup of freehand three-dimensional ultrasound to measure semitendinosus (ST) muscle morphology.
Subjects were positioned on an examination bed on their left side, with the hip of the measured (right) leg at 70° flexion. At knee angles corresponding to a knee moment of 0 and 4 Nm and at a knee angle of 65°, a 30–40 seconds video sequence of transverse US images was collected by a conventional 2D ultrasound apparatus, starting distally at the ST tendon to the ischial tuberosity (white arrow on the thigh indicates scan direction). The position of each ultrasound image in space was recorded by tracking the ultrasound probe (based on three markers that were rigidly attached to it—indicated by markers probe) using a motion capture system (tracking device). The images from the ultrasound video sequence were combined with the probe position data an reconstructed to a voxel array that was used for further analysis.
Fig 2.
Knee moment-angle characteristics of children with a spastic paresis (SP) and typically developing (TD) children.
The curve of SP children was shifted towards more flexed knee angles compared to the curve of TD children and has a steeper slope (i.e. higher stiffness). Black line: SP children; Grey dashed line: TD children. Values are mean ± SD.
Table 2.
Morphological characteristics of semitendinosus muscle (ST) in children with a spastic paresis (SP) and typically developing (TD) children at 65○ knee angle and knee angles corresponding to 0 Nm and 4 Nm net knee flexion moments.
P-value shows the difference between children with SP and TD children.
Fig 3.
A: Absolute and relative (rel) length changes (Δ) of the fascicles between knee angles corresponding to 0 Nm and 4 Nm net knee moment. B: Absolute and relative length changes of the distal tendon between these two knee angles.
Fascicle length and tendon length are normalized to femur length (ℓfasc_norm, ℓtdist_norm). Absolute as well as relative length changes of fascicles and tendons did not differ significantly between children with a spastic paresis (SP) and typically developing (TD) children. Data are presented as means ± SD.
Fig 4.
Typical example of 3D ultrasound images and segmentation of muscle volume of a child with a spastic paresis (left A1-C1) and typically developing child (right A2-C2).
A: longitudinal view of semitendinosus muscle (ST) (proximal on the left side); B: transversal view of ST at three locations (most proximal on left side; orientation of images: medial (left), lateral (right)); yellow: distal compartment of ST; red: proximal compartment of ST; C: Proximal (red) and distal (yellow) compartments after segmentation.
Fig 5.
Muscle volume and physiological cross sectional area (PCSA) of semitendinosus muscle (ST) of children with a spastic paresis (SP) and typically developing children (TD).
Muscle volume of ST (proximal, distal and total muscle volume) and PCSA are substantially smaller in SP children. PSCA was calculated by dividing muscle volume by fascicle length at 4 Nm. Data are presented as means ± SD; *p<0.01.
Fig 6.
Knee angle at 4 Nm (θ4Nm) plotted as a function of normalized fascicle length at 0 Nm (ℓfasc0Nm) (A) and at 4 Nm (ℓfasc4Nm) (B).
Variation in ℓfasc0Nm and ℓfasc4Nm explained a substantial part of variation in θ4Nm (49% and 60%, respectively). Lines indicate the regression lines for the combined group. Separate symbols are used to indicate data points for SP (spastic paresis) and TD (typically developing).