Developmental dysplasia of the hip (DDH) results from an abnormal relationship of the femoral head to the acetabulum. It usually occurs from ligamentous laxity and / or abnormal position in utero (therefore is more common with oligohydramniotic pregnancies).
Demographics and clinical presentation
DDH is usually suspected in the early neonatal period due to the widespread adoption of clinical examination (including Ortolani test, Barlow maneuvers, Galeazzi sign). The diagnosis is then usually confirmed with ultrasound, although the role of ultrasound in screening is controversial 1,3.
The reported incidence varies between 1.5 and 20 per 1000 births 1, with the majority (60 - 80%) of abnormal hips resolving spontaneously within 2 - 8 weeks 1 (so called immature hip).
Risk factors include 1,4
- female gender (M:F ratio ~ 1:8)
- family history
- breech presentation
Ultrasound is the modality of choice prior to ossification of the proximal femoral epiphysis. Once there is significant ossification then x ray examination is required.
For some reason the left hip is said to be more frequently affected 4.
Ultrasound is the test of choice in the infant ( < 6 months) as the proximal femoral epiphysis has not yet significantly ossified. Additionally it has the advantage of being a real time dynamic examination allowing the stability of the hip to be assessed with stress views.
A number of values are used to 'objectively' asses morphology.
Angle formed by the acetabular roof to the vertical cortex of the ilium. This is a similar measurement as that of the acetabular angle (see below). The normal value is greater than or equal to 60 degrees.
Angle formed between the vertical cortex of the ilium and the triangular labral fibrocartilage (echogenic triangle). The normal value is less than 77 degrees, but is only useful in assessing immature hips when combined with the alpha angle (see Sonographic Classification of Development Dysplasia of the Hip (DDH) ).
The percentage of the femoral epiphysis covered by the acetabular roof. A value of greater than 58% is considered normal.
The key to plain film assessment is looking for symmetry and defining the relationship of the proximal femur to the developing pelvis. The ossification of the superior femoral epiphyses should be symmetric. Delay of ossification is a sign of DDH.
Hilgenreiner's line is drawn horizontally through the superior aspect of both triradiate cartilages. It should be horizontal, but is mainly used as a reference for Perkin's line and measurement of the acetabular angle.
Perkin's line is drawn perpendicular to Hilgenreiner's line, intersecting the lateral most aspect of the acetabular roof. The upper femoral epiphysis should be seen in the inferomedial quadrant (i.e below Hilgenreiner's line, and medial to Perkin's line)
The acetabular angle is formed by the intersection between a line drawn tangential to the acetabular roof and Hilgenreiner's line, forming an acute angle. It should be approximately 30 degrees at birth and progressively reduce with maturation of the joint.
Shenton's line is drawn along the inferior border of the superior pubic ramus and should continue laterally along the inferomedial aspect of the proximal femur as a smooth line. If there is superolateral migration of the proximal femur due to DDH then this line will be discontinuous.
Treatment and prognosis
- Pavlik harness : usually for younger patients (< 6 months of age)
- closed reduction : usually for older patients
- open reduction : much older patient or if closed reduction not successful
- 1. US Preventive Services Task Force. “Screening for Developmental Dysplasia of the Hip: Recommendation Statement.” PEDIATRICS 117, no. 3 (3, 2006): 898-902. doi:10.1542/peds.2005-1995.
- 2. R Graf "The diagnosis of congenital hip-joint dislocation by the ultrasonic Compound treatment." Arch Orthop Trauma Surg. 1980; 97(2):117-33
- 3. Roposch Andreas, Nicole M. Moreau, Elizabeth Uleryk and Andrea S. Doria. “Developmental Dysplasia of the Hip: Quality of Reporting of Diagnostic Accuracy for US1.” Radiology 241, no. 3 (December 2006): 854-860. doi:10.1148/radiol.2413051358.
- 4. Taeusch H. William, Roberta A. Ballard, Christine A. Gleason and Mary Ellen Avery. Avery's diseases of the newborn. Elsevier Health Sciences, 2005. ISBN: 0721693474, 9780721693477.
Synonyms & Alternative Spellings
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