We retrospectively revised all hip MRI carried out in our institution in the last 4 years (from January 2009 to December 2012).
There were a total of 90 studies of 89 patients between 20 and 67 years old (mean age of 38). We reviewed the studies using the PACS.
We also reviewed all the clinical histories of our patients,
paying special attention to the clinical onset symptoms and the radiology reports from the MRI studies,
as well as the background and follow-up after treatment of our patients. We used the computer system of our institution (SAP).
1.
MRI technique:
All MRI were performed in a 1.5 or 3T using a phased array coil.
Our protocol includes the standard sequences of a hip study: axial and coronal T1 and DP fat suppressed weighted images of the pelvic ring and T1 and DP fat suppressed weighted images localized at the hip in the three planes.
In all cases both hips were imaged with MRI.
Radial planes were realized in some cases.
Contrast material was given in a few cases.
2.
Measurements and other parameters taken into consideration:
Pelvic anatomy must be known precisely to be able to depict this abnormality,
and there are different structures to be considered.
MRI images of all patients were analyzed for the following data:
1.
Neck-shaft angle: the angle between the long axis of the femoral neck and the long axis of the femoral shaft on coronal images.
In a normal adult, this is about 125°,
being greater in newborns (150°) and smaller in elderly populations (120°).2 An increase in the inclination angle of the femur neck is defined as a coxa valga that will affect both knee and hip function.
2.
Wiberg angle: also known as CE (centre-end of the roof).
Angle formed by a line drawn from the centre of the femoral head to the outer edge of the acetabular roof,
and a vertical line drawn through the centre of the femoral head on a coronal plane.
Angles greater that 25º are considered normal and angles less than 25º indicate dysplasia.3 Fig. 1
3.
Anterior acetabular sector angle (AASA),
posterior acetabular sector angle (PASA) and femoral anteversion.
These measurements are particularly useful in the evaluation of acetabular dysplasia.3 Fig. 2
4.
Ischiofemoral space (IFS): the smallest distance between the lateral cortex of the ischial tuberosity and the medial cortex of the lesser trochanter of the femur.
The normal distance is 20mm or more,
measured on axial planes2.
A distance of under 20mm is considered abnormal and IFI must be considered as responsible for the symptoms.
5.
Quadratus femoris space (QFS): space between the hamstring tendons and the lesser trochanter on axial images.
This is the space through which the quadratus femoris muscle passes.
It is considered normal when the smallest distance is above 7mm.2
6.
Hamstring tendon area (HTA): semimembranosis,
semitendinosis,
and the biceps femoris tendons form the hamstring tendons and may contribute to the narrowing of the QFS and the development of IFI.
7.
The quadratus femoris muscle is a flat quadrilateral muscle that extends from the external border of the ischial tuberosity and inserts into the quadrate tubercle of the femur in the lesser trochanter.
Changes in the intensity signal may be seen in acute and chronic cases of muscle entrapment,
such as edema,
fibrilar ruptures and fatty replacement.