Developmental Dysplasia of Hip for FRCS Orth

Courtesy: Rishi Dhir, FRCS Tr and Orth, CEO, Let’s Talk Dr

DEVELOPMENTAL DYSPLASIA OF HIP

Defined as abnormal development of the hip resulting from capsular laxity along with combination of genetic and mechanical factors. It results in a spectrum of disease from dysplasia to subluxation and then to frank dislocation

Pathophysiology

Initial instability which causes dysplasia (abnormal development) of acetabulum which causes subluxation of femoral head, which gradually progresses to dislocation.
Over a long period of time secondary barriers develop which then hinders reduction.
As a result of chronic dislocation, certain anatomical changes occur in the form of
• Flattening of femoral head
• Increased femoral and acetabular anteversion
• Increased obliquity and decreased concavity of acetabular roof
• Thickening of medial acetabular wall

Evaluation

Every baby is screened for hip abnormalities at birth. Those who have an abnormal examination are referred to baby ultrasound clinic within 6 weeks where triple assessment of babies are done.

Triple assessment includes

1. History (risk factors)- 5 F’s
• First bone
• Female
• Fluid(oligohydramnios)
• Foetal malposition (breech)
• Family history

2. Examination
• Asymmetry of skin creases on gluteal fold
• Asymmetry of leg length (Galeazzi test)
• Barlow’s test
• Ortolani’s test

Barlow’s test: In a dislocatable hip, hip is dislocated by adducting the hip and depressing a flexed femur (clunking sound is heard)
Ortolani’s test: In a reducible hip, the dislocated hip is reduced by abducting the hip and elevating the flexed femur

Radiological assessment – using USG

In DDH the alpha angle decreases and beta angle increases
Alpha angle: angle between baseline(ilium) and acetabular roof, normal>60 degree
Beta angle : angle between baseline(ilium) and labrum, normal<55 degree
In a 4-6 month old child we can use an x-ray to diagnose DDH.
Typical x-ray finding are
• Ossific nucleus will be small
• Shenton’s line will be broken
• Acetabular index increases (normally 5 years),
lateral centre edge angle of Wiberg. Normally it will be <25 degree, whereas it increases in acetabular dysplasia

Treatment

Goals

• Stable hip
• Concentric reduction of hip
• Normal acetabular development
• Prevent degenerative joint disease

-AGE < 6 MONTHS: Pawlik’s Harness
• Flexion abduction orthosis(dynamic)
• 4 straps- shoulder, chest, anterior strap, posterior strap(abduction strap)
• Ramsey safe zone(too much abduction causes AVN whereas too much adduction causes dislocation)

-AGE 6 MONTHS: X-ray+ EUA +Arthrogram + adductor tenotomy + closed reduction , followed by hip spica application

Blocks for reduction- Intrinsic & extrinsic
Extrinsic – tight muscles(psoas, rectus femoris, hamstrings etc)
Intrinsic- hour glass capsule constriction, inverted labrum, transverse acetabular ligament, pulvinar fat

-AGE 12 MONTHS: Open reduction, followed by hip spica application
• Smith Peterson- anterior approach, internervous plane between femoral and superior gluteal nerve
• Ludloff – medial approach

-AGE 18 MONTHS OR OLDER: Osteotomies

1. Femoral- Varus derotation osteotomy, shortening osteotomy
2. Acetabular redirectional osteotomies