CASE 78
By: Dr. Amna Kashgari MD,SSC-Rad
HISTORY: An 18-month-old girl with limping and short left leg.
What are your findings?
What is your diagnosis?
What are the risk factors for this disease?
FINDINGS:
Frontal (A) and frog leg (B) radiographs of the pelvis show shallow and steep left acetabulum with false acetabulum superiorly. The left femoral head is smaller than the right side and dislocated laterally and superiorly.
DIAGNOSIS:
Left Developmental dysplasia of the hip (DDH).
RISK FACTORS:
Breech positioning in utero.
Oligohydramnios.
Family history.
Female sex.
First born.
PEARLS AND DISCUSSION:
Developmental dysplasia of the hip (DDH) is abnormal development of the hip joint. It results in abnormal relation between the femoral head and acetabulum.
Etiology: Ligamentous laxity secondary to exposure to maternal estrogens in the perinatal period may play a role.
Risk factors:
Breech positioning in utero.
Oligohydramnios.
Family history.
Female sex.
First born.
Imaging evaluation:
| Modality | Age | Findings |
|---|---|---|
| Ultrasound hip | Birth to 6 months |
Un-ossified femoral head |
| Plain radiograph | More than 6 months | Ossified femoral head |
| CT scan | Problem solving and post-operative | High dose of ionizing radiation |
| MR scan | Treatment planning and monitoring | Lack of ionizing radiation |
Hip ultrasound to evaluate the following:
· Femoral Head Position Relative to the Acetabulum: Normally positioned femoral head is more than 50% covered by the acetabulum.
· Alpha angle: The angle formed between the vertical cortex of the ilium and the acetabular roof in coronal plan.
· Beta angle the angle formed by a line through the vertical ilium and the cartilaginous acetabular labrum.
· The stress maneuver: It is similar to the clinical Barlow examination in which the hip adducted and pressure is exerted on the knee to force the femoral head to dislocate posteriorly to determine the stability of the femoral head.
Graph method for ultrasound evaluation of DDH depends on the alpha angle to determines the type and in some instances, the beta angle is used to determine subtype.
Graph classification:
| Type | Alpha angle | Beta angle | Description |
|---|---|---|---|
| Type 1 | > 60 | < 55 | Normal |
| Type 2a | 59-50 | Physiologic immaturity at younger than 3 mo | |
| Type 2b | 59-50 | Immature at age 3 mo or older | |
| Type 2c | 49-43 | < 77 | Extremely deficient bony acetabulum; femoral head is concentric but not stable |
| Type 2d | 49-43 | > 77 | Femoral head is grossly subluxed and labrum is everted, increasing β angle |
| Type 3 | < 43 | Dislocated femoral head with shallow acetabulum | |
| Type 4 | < 43 | Dislocated femoral head with severely shallow, dysplastic acetabulum and inverted labrum |
Hip radiograph:
It is the stander method to assess DDH for children older than 6 months.
AP film: To assess the acetabulum morphology and femoral head position.
Frog leg: To assess if the subluxed hip is reducable.
Several lines are used to assess DDH on plan radiograph
Hilgenreiner line: Line crossing through both triradiate cartilages.
The acetabular angle: Between the Hilgenreiner line and a line drawn through the acetabular roof.
Neonate should be < 30.
Infant and children < 25.
Perkins line: Vertical line drawn perpendicular to the Hilgenreiner line and intersecting the lateral rim of the acetabular roof. The femoral head should be in the medial inferior quadrant.
Shenton line: C-shaped line drawn along the inferior border of the superior pubic ramus and the inferomedial border of the femoral neck. A normal Shenton line should form a smooth arc.
Hip CT-scan and MRI:
Problem solving in difficult cases.
pre- or post-operative evaluation.
Complication of DDH:
Osteoarthritis.
Leg length discrepancy.
Avascular necrosis.
FURTHER READING:
US Preventive Services Task Force. “Screening for Developmental Dysplasia of the Hip: Recommendation Statement.” PEDIATRICS 117, no. 3 (3, 2006): 898-902
Lane F Donnelly. Fundamental of pediatric radiology. ISBN-13: 978-0721690612
Johan G Blickman, Bruce R Parker, Patrick D Barnes. Pediatric Radiology: The Requisites, 3e. ISBN-10: 0323031250
