Muscle volume and physiological cross sectional area (PCSA) of semitendinosus muscle (ST) of children with a spastic paresis (SP) and typically developing children (TD).

<p>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.</p

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).

<p>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.</p

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.

<p>Fascicle length and tendon length are normalized to femur length (ℓ_{fasc_norm}, ℓt_{dist_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.</p

Anthropometric and subject data ± standard deviation (range) and number of previous treatments with Botulinum toxin A.

<p>Anthropometric and subject data ± standard deviation (range) and number of previous treatments with Botulinum toxin A.</p

Setup of freehand three-dimensional ultrasound to measure semitendinosus (ST) muscle morphology.

<p>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.</p

Knee angle at 4 Nm (θ_4Nm) plotted as a function of normalized fascicle length at 0 Nm (ℓfasc^0Nm) (A) and at 4 Nm (ℓfasc^4Nm) (B).

<p>Variation in ℓfasc^0Nm and ℓfasc^4Nm explained a substantial part of variation in θ_4Nm (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).</p

Individual gait kinematics before and after hamstring lengthening surgery.

<p>Pelvic tilt at mid-stance and terminal swing (A, B), hip angle at mid-stance and terminal swing (C, D) and knee angle at mid-stance and terminal swing (E, F) at baseline and 8–20 months after surgery. Pelvic tilt changed towards more anterior tilt and knee joint was more extended both at mid-stance and terminal swing, while effects on hip angles were variable. The grey area represents the mean and two standard deviations of a group of typically developing children. Note that most of the children used a walking device during gait analysis, which most likely contributed to the anterior pelvic tilt. In addition, during gait analysis three subjects (subjects 3, 4 and 6) walked with different support after surgery than before (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0192573#pone.0192573.s003" target="_blank">S3 Table</a>).</p

Individual effects of hamstring surgery on ST morphology.

<p>Muscle belly length and tendon length were measured at knee angles corresponding to 0 Nm (A, B), 4 Nm (C, D) and at 65° knee flexion angle (E, F). Muscle belly decreased after surgery, while tendon length increased. Time points used for statistical analysis are highlighted by red circles.</p

Typical example of 3D ultrasound images and segmentation of muscle volume of a child with a spastic paresis before medial hamstring lengthening.

<p>Images before surgery (left, A1-C1) and 12 months after surgery (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 is medial-lateral). Yellow: distal compartment of ST; red: proximal compartment of ST. C: Proximal (red) and distal (yellow) compartments after segmentation. After surgery, this child showed a reduction of muscle volume by 26%, muscle belly length decreased by 32% and tendon length increased by 62%, measured at a knee angle corresponding to 4 Nm knee moment. Note the post-surgical increase in ultrasound echo intensity (cf. A2 and A1), which complicated exact identification of structures, in particular the distal and proximal ends of the tendinous inscription. The tendinous inscription is indicated by a red arrow in A1 and A2.</p

Effects of hamstring muscle surgery on gait kinematics.

<p>Presented data were measured before (Baseline, yellow) and 8–20 months (Medium follow-up, red) after medial hamstring lengthening. In grey the reference data of a group of typically developing children (TD) are presented. Values are mean±standard deviation. MSt = Mid-stance; TSw = Terminal Swing. **p<0.01; *p<0.05.</p