Developmental dysplasia of the hip
Firstly, consider some of the details of the muscles of the hip, the insertion points of the main muscles are listed in the table below.
The hip joint is a ball-and-socket joint between the acetabulum and the head of the femur. Its range of movement is limited by the acetabulum and the ligaments around the cavity. The range of movement for the hip joint is:
- Extension-flexion - 10-0-130
- Abduction-Adduction - 40-0-30
- Lateral rotation-medial rotation - 50-0-40
Developmental dysplasia of the hip (DDH) is an important group of pediatric diseases. It is a term that refers to abnormal hip development resulting in dislocation (D), subluxation (C) or laxity/dysplasia (B) of the hip (A is normal).
Within the spectrum of diseases, DDH includes:
- Dysplasia - shallow or underdeveloped acetabulum
- Subluxation - displacement of the joint with some contact remaining between articular surfaces
- Dislocation - complete displacement of the joint with no contact between the original articular surfaces
- Teratologic hip - dislocation in utero and irreducible on exam, presents with pseudoacetabulum and is associated with neuromuscular conditions (e.g. Ehlers-Danlos)
The condition is the most common orthopaedic disorder in newborns with an incidence as high as 1:100 for the dysplastic form (1:1000 for the dislocation form). It is more common in females, and in the left left. Risk factors include being the firstborn, having a family history of the disease, being breech and oligohydramnios.
The pathogenesis is thought to be initial instability of the joint that leads to dysplasia. Dysplasia can then lead to subluxation and gradual dislocation. If not resolved shortly after birth then there are severe consequences to the natural history of the disease:
- Development of secondary barriers to reduction
- Pulvinar thickens
- Ligamentum teres thickens and elongates
- Transverse acetabular ligament hypertrophies
- Hip capsule and iliopsoas form hourglass shape
- Anatomic changes
- Increased femoral anteversion
- Flattening of femoral head
- Increased acetabular anteversion
- Increased obliquity and decreased concavity of the acetabular roof
- Thickening of the medial acetabular wall
DDH is commonly missed unless screened for in newborns. There are three examinations that can be done to check for DDH:
- Barlow maneuver
- Adduct the hip, while bending the knee to 90, and put pressure posteriorly through the hip joint, feel for a ‘clunk’
- Ortolani maneuver
- Flex the hip and knees of the infant to 90 degrees then then place anterior pressure on the greater trochanters, gently and smoothly abducting the infant's legs using the examiners thumbs