Developmental Dysplasia of the Hip | Pediatric Radiology Reference Article | Pediatric Imaging

Etiology:
— Abnormalities of intrauterine positioning
— Breech presentation (20%)
Imaging US Normal:
— Alpha (bony) angle (greater than 60 degrees) and beta (cartilaginous) angle (less than 55 degrees) and there is greater than 50% coverage of femoral head
US Immature:
— Age less than 3 months and alpha angle is 50-59 degrees
Imaging US Dysplastic:
— Age less than 3 months and alpha angle is less than 50 degrees, age greater than 3 months and alpha angle is 50-59 degrees, hip has less than 50% coverage of femoral head, beta angle greater than alpha angle, beta angle greater than 55 degrees means lateral displacement
Imaging Radiograph:
— Asymmetric ossification of femoral epiphyses with the dysplastic side have delayed ossification due to delayed epiphyseal development
Imaging Radiograph lines for hip dislocation:
— Hilgenreiner’s line through the bilateral triradiate cartilage horizontally
— Perkin’s line is perpendicular to Hilgenreiner’s line through superolateral corner of acetabulum, it should bisect middle third of metaphysis, femoral ossification center should be medial to Perkin’s line in lower inner quadrant
— Shenton’s line is a smooth curve along the inferior border of the superior pubic ramus and along the inferomedial border of the neck of femur
— Acetabular angle is line along roof of acetabulum to Hilgereiner’s line and is less than 30 degrees at birth and decreases to 22 degrees at 1 year, is increased in developmental dysplasia of hip and neuromuscular disorders and achondroplasia and first year of life in Trisomy 21
DDX:
Complications: If missed see acetabular dysplasia or pseudoacetabulum which leads to leg length discrepancies and limp and pain and osteoarthritis
Treatment: Pavlick harness in neonate and then surgical if harness is unsuccessful
Clinical:
— For patients with positive Barlow and Ortolani manueuver get hip US at 2 weeks
— For patients with breech birth get hip US at 4-6 weeks or up to 8-10 months and after 4-6 months can do radiograph for screening

Perkin's line                    Perkin's line
    |                                |
____|________________________________|____ Hilgenreiner's line
    |                                |
    | Femoral head      Femoral head |

Radiology Cases of Developmental Dysplasia of the Hip

Radiograph of developmental dysplasia of the hip — Frogleg radiograph of the pelvis shows markedly asymmetrical ossification of the femoral epiphyses, with the left femoral epiphysis smaller in size than the right femoral epiphysis. The left acetabulum is also more shallow than the right acetabulum and the left femoral epiphysis appears slightly subluxed laterally and superiorly.

US of development dysplasia of the hip — Coronal US of the bilateral hips shows lateral subluxation of the left femoral head out of the left acetabulum with less than 50% coverage of the left femoral head and a decreased alpha angle of the left hip of 45 degrees. There is a normal alpha angle of the right hip of 69 degrees and the right femoral head is > 50% covered.

US of developmental dysplasia of the hip — Coronal ultrasound images of the left hip (left) and right hip (right) were obtained after 5 weeks of therapy in a Pavlik harness with the patient located in the Pavlik harness during the exam. The coronal view is meant to simulate an anterior-posterior radiograph of the hip. The left hip is still dysplastic with there still being a shallow acetabulum and decreased alpha angle even though the left hip appears fairly well located in the left acetabulum. The left hip alpha angle measured 45 degrees (normal is usually greater than 60 degrees) but had increased since the last exam. The right hip was normal in appearance.