Anatomy of Hip Joint & Developmental Dysplasia

Study Notes

The hip joint is a ball and socket joint designed for stability and weight-bearing
The head of the femur articulates with the acetabulum of the hip bone
The head of the femur is covered with hyaline cartilage except for the fovea
Acetabulum is a lunate-shaped structure that includes a notch and a fossa
The hip joint is supported by ligaments and surrounding muscles
The stability of the hip joint is also influenced by the length and obliquity of the neck of the femur

DDH is a condition involving partial or complete displacement of the femoral head from the acetabular cavity
The prevalence of DDH is higher in females (7 times more affected)
The left hip is affected more often than the right, and bilateral involvement occurs in 1 in 5 cases

DDH is associated with genetic predisposition including generalized joint laxity and shallow acetabula
Hormonal factors, including maternal relaxin and high estrogen and progesterone levels, can also contribute to DDH
Intrauterine malposition, particularly extended breech position, increases the risk of DDH
Postnatal factors play a lesser role in the development of DDH

DDH is often detected at birth or shortly after the child starts walking
Routine screening for suggestive signs in newborns, especially those at high risk, is essential
Signs of DDH in early childhood include asymmetry of groin folds, a clicking sound, and limited movement
Older children may present with a peculiar gait and lack of pain

Barlow's Test:
- Identifies an unstable hip that can be passively dislocated
- The examiner flexes the hip and knees to 90 degrees and applies posterior pressure on the knee while adducting the hip
- A positive test indicates that the femoral head is displaced out of the socket
Ortolani's Test:
- Follows Barlow's test to determine if the hip is dislocated
- The examiner flexes the hips and knees to 90 degrees, then abducts the hip and pushes the thigh anteriorly
- A positive test involves a palpable and audible clunk as the hip is reduced

Limited hip abduction, limb shortening, and external rotation
Higher buttock fold, asymmetrical thigh fold, and lordosis of the lumbar spine
Galeazzi's Sign:
- Hips flexed to 70 degrees, knees flexed
- The affected side is lower than the unaffected side
Trendelenburg's Test:
- Positive in unilateral dislocation, resulting in Trendelenburg gait
- Positive in bilateral dislocation, resulting in a waddling gait

Ultrasonography:
- Has replaced radiography for imaging hips in newborns
- Allows sequential monitoring of the hip during splintage
Plain X-rays:
- More useful after the first 6 months of age
- Assessment involves drawing lines on the x-ray to identify specific features