Subjects
The study protocol conforms to the ethical guidelines of the 1975 Declaration of Helsinki and the study was approved by the local Ethics Committee and Institutional Review Board.
Written informed consent was obtained from each child’s parent.
This prospective study included 50 hips of 25 children with spastic CP. Inclusion criteria were as follows; having diagnosis of CP verified by a physiatrist who had an experience in in pediatric rehabilitation medicine,
having at least MAS 1 spasticity in the flexor and adductor hip muscles aged from 2 to10 years,
having anteroposterior X-Ray of the pelvis within 2 months before enrollment.
Exclusion criteria were as follows; botulinum toxin or neurolytic agents (such as phenol or alcohol) injection within 6 months,
previous surgery or any interventional procedures of trauma to the hips or lower limbs,
having any other musculoskeletal or neurologic disorder except CP that affect lower limbs and hip.
The migration percentage (MP) measurement
The hips were examined with anteroposterior radiographs.
Radiographs were taken with the patient in the supine position,
the pelvis symmetric with respect to rotation,
and the femurs in the neutral abduction/adduction position relative to the pelvis.
The migration percentage (MP) was measured on all radiographs.
Radiographs were examined by both of the radiologists.
The hospital’s computer software for storing patient radiographic records was used to measure and calculate different angles and distances to minimize measurement errors.
To evaluate the MP,
the Hilgenreiner line (H) was ascertained by drawing a line between the Y-cartilages of both sides using the software’s angle measurement tool.
Next,
a second line,
known as the Perkins’ line (P),
perpendicular to the first one,
was drawn through the upper outer side of the acetabulum.
Then,
the innermost and outermost borders of the femoral head were defined,
and two lines were drawn from those inner and outer lines intercepting at an angle of 90° to the H line.
Finally,
the migration percentage was calculated as the part of the femoral head outside Perkins’ line divided by the total width of the femoral head multiplied by 100 (Fig.1).
US and Shear Wave Elastography (SWE) examinations
The stiffness of the gluteus medius and maximus,
adductor magnus and iliopsoas muscles was measured by SWE.
The US elastography evaluations were performed using a US ARFI elastography system (Acuson S 2000,
Siemens Medical Solutions,
Mountain View,
CA,
USA) with a linear transducer that enables scanning with a frequency ranging of 9−4 MHz.
All of the B-mode US images and SWE images were performed by the same radiologist.
All children were scanned on an examination bed in the prone position and then in the supine position.
If voluntary contractions of the lower limb muscles occurred,
the elastography examination has stopped.
A virtual touch tissue quantification (VTQ) application was used for the quantitative assessment of tissue stiffness.
All muscles were evaluated in longitudinal plane.
For Shear Wave Velocity (SWV) measurements,
a region of interest (ROI) cursor was placed at the mid-point of the muscles’ largest circumference (Figs.
2 and 3). By VTQ a fixed ROI of 5x5 mm was used.
SWV of each lesion were measured 3 times within the lesion.
The mean values of these were used for analysis.
SWV values are displayed as m/s (meters per second).
For SWV,
the range was 0–9 m/s.
If the system displayed the SWV as non-numeric symbols (X.XX),
and the measurements were repeated until valid values were found.
The radiologist was blind to the patients’ clinical data.
The correlation between the Reimer’s MP and the stiffness of hip flexors and adductors were analyzed.
The stiffness of the gluteus medius and maximus,
adductor magnus and iliopsoas muscles was measured. The stiffness of the hip flexor (iliopsoas) and extensor (gluteus maximus) muscles and hip adductor and abductor muscles were compared.
Also the correlations among these muscle groups were assessed.
Statistical Analysis
Descriptive statistics were expressed as mean ± standard deviation.
Kolmogorov-Smirnov test was used to test normality of data.
The correlation of sonoelastographic findings with MP was assessed using Pearson correlation coefficient test.
The correlation coefficients were interpreted as either excellent r≥0.91; good 0.90≥r≥0.71; fair 0.70≥r≥0.51; weak 0.50≥r≥0.31; or little or none r≤0.3.
The significance level was determined at p<.05.
All statistical tests were performed using IBM SPSS Statistics software program (Chicago,
IL,
USA) for Mac version 20.0.