Developmental dysplasia of Hip (DDH)

Normal Growth For Normal Growth; genetic balance of: Growth of acetabular & triradiate cartilages. Well located and centered femoral head. Factors affecting the shape of Proximal part of femur: Growth plates, Muscle pull, Weight bearing forces, Normal joint nutrition. By the 11th intrauterine week, hip joint is fully formed.

Acetabular Depth determined by: Spherical femoral head, Growth of acetabular cartilage, Appositional growth under the prichondrium, Growth of adjacent bones The majority of acetabular shape is determined by the age of 8 years. Whether instability comes first then affects acetabular development, or primary acetabular dysplasia is not known, Both may be right.

DDH Dysplasia : Inadequate development of femoral head +/- acetabulum. Was called “Congenital Dislocation of the Hip”, Now “Developmental Dysplasia of the Hip” It comprises a spectrum of : Dislocation during neonatal period Sublaxation or partial displacement Shallow acetabulum (dysplasia) with no actual displacement.

Incidence: Risk Factors: Female Frank Breech 5-20 / 1000 live births have hip instability 2-3 / 1000 live births. Increasing since screening. F : M = 6 : 1 Left Hip : Right Hip = 4 : 1 Risk Factors: Female Frank Breech Fluid abnormality : Oligohydraminos Family History First born Foot deformity Facial asymmetry; Torticolis

Etiology: Genetic Factors, including generalized joint laxity / shallow acetabulum Hormonal changes in late pregnancy could aggravate ligamentous laxity (premature low incidence) Intrauterine malposition (breech with extended legs) Postnatal factors

Pathogenesis Excessive capsular laxity and shallow acetabulum. Normally femoral head is held in the acetabulum by surface tension done by synovial fluid. This is lost in dysplasia. Glides over a ridge. “Ortolani sign”. Majority of abnormalities are on the acetabular side. Changes on the femoral head are secondary to anteversion and pressure changes from acetabulum or ilium due to sublaxation. Dysplastic hip has a ridge in the sup- post. and inferior acetabulum. This ridge produces palpable sensation of Ortolani sign.

Changes associated with Dysplasia: Acetabular labrum become enlarged. Acetabulum becomes flattened (dysplastic), bc not stimulated to develop around the absent femoral head. Ligamentum teres becomes lengthened, hypertrophic and redundant. Transverse acetabular ligament: pulled superiorly with capsule which blocks the lower portion of the acetabulum. Capsule of hip joint becomes expanded. Muscles crossing the hip joint becomes shortened and contracted.

Clinical Findings: Ortolani Test “ Click of Entry”: For dislocated hip Thighs are held with thumbs medially and fingers on greater trochanter Hips flexed to 90 degrees, gently abducted (normally, abd to 90 degrees smooth), With dysplasia movement is restricted, with pressure on greater trochanter “clunk” is felt, and the dislocation reduces, then full abd. If no clunk or jerk of entry, irreducible dislocation.

Barlow Test “ Click of Exit”: To dislocate the hip Pelvis is stabilized with finger and thumb of one hand Hips flexed to 90 degrees, gently abducted (normally, abd to 90 degrees smooth), Middle finger of examining hand on the greater trochanter, and flexed leg contained in the palm Thumb is on the inner side of the thigh on lesser trochanter. Move leg to adduction at the same time press backward and downward, then upward again If femoral head moves out then in again; felt as a “clunk”, so hip is dislocatable “unstable”.

Barlow Test

These tests can detect early cases, most accurate with in 48 - 72hrs of birth then decrease. 90% specificity and 60% sensitivity, poor screening tests. Every hip with signs of instability - +ve tests – should be examined by ultrasonography. Which shows shape of socket and position of femoral head. Ideally children should be examined at 6, 12 and 18 months. In order not to miss late signs of DDH. Occasionally dislocation does not occur until several months after birth.

Parents may notice delayed walking, and presence of a limp. Galleazi’s sign: shortening of affected side, extra skin creases, seen when knees and hips flexed. Dysplasia: used for +ve Ortolani sign ( hip that is dislocated and can be reduced). Dislocation: used for –ve Ortolani sign (unreducable hip), ass with 2ary adaptive changes; shortening, dec. abduction, asymmetry of folds.

Unilateral dislocation: Skin creases are asymmetrical No full abduction Shorter leg, rotated internally. Bilateral dislocation: (difficult to detect): No asymmetry Waddling gait (normal toddling) Perianal gap abn wide Abduction limited

DDH on X ray: The bony acetabular roof slopes upward Socket is unusually shallow Ossification centre of femoral head is underdeveloped Head looks displaced upward and backward. Hilgenreiner & Perkin’s lines should be drawn and the head should be in the inner lower quadrant. The acetabular index < 30 degrees at the age of one year.

In a normal hip, the Shenton line is a smooth unbroken arc that bridges the medial femoral metaphysis and the inf edge of the sup pubic ramus. Displacement of the femoral head out of the joint space and disruption of the Shenton line is suggestive of DDH.

The acetabular index is the angle between the Hilgenreiner line and a line drawn from the triradiate epiphysis to the lateral edge of the acetabulum.. The Shenton line is a line drawn from the medial aspect of the femoral neck to the inferior boarder of the pubic ramus.

In Normal Hip: The ossification centers of the capital femoral epiphyses are symmetric and located in the joint spaces. Both heads project in the inner lower quadrants formed by the intersection of the Hilgenreiner (H) and Perkin (P) lines. Shenton lines (S) are continuous. The acetabular angles are symmetric and less than 28° bilaterally.

The abnormally located hip articulates with a false neoacetabulum.

Legs in the frog-leg position indicates that the plane of the femoral projection is toward the triradiate cartilage, suggesting that the hips are reducible.

DDH on Ultrasound: Most effective way!!! Advantages: Gives accurate diagnosis of dislocation, Non invasive For < 4-6 months of age, more accurate than radiograph ( after 4 mnths radiograph is more useful) Provides a dynamic ass of shape of socket and position of femoral head Disadvantages: Over diagnosis of dysplasia. It could be a sign of acetabular immaturity not pathology, and so over treatment. SO “ WAIT & WATCH” 90% of dysplasia at birth resolve by 6-9 weeks.

Prognosis: The earlier the better… Should start treatment within a week or two then follow up. If treated after the first year, has 50% chance of going back to normal or near. If untreated; will have progressive deformity and disability. In bilateral dislocation disability is less marked.

Management Of Dislocated Hip Aims: Concentric reduction Early acetabular development Pavlik harness: In newborn (birth – 6 months): Treatment; directed to stabilize the hip with +ve Ortolani or Barlow test, use double napkins or abduction pillows for 6 wks. If still unstable treat with abduction splintage for 3-6 mnths, ass with AVN ( not recommended). Success rate of 85% - 95%, if treated during first 2 months of life.

2. Toddlers ( 6months – 6 yrs ): For larger infants, Pavlik Harness is better. 2. Toddlers ( 6months – 6 yrs ): Success rate of Pavlik decreases significantly after 4-6 months. Treatment: Closed reduction under anasth. Risk of AVN, so Reduction is gradual, adequate preoperative traction to both legs (vertical frame) and abduction gradually incr. until 3 wks.

3. Could be aided with adductor tenotomy, may achieve concentric reduction. 4. Arthrogram will show if femoral head reduced. If concentrically reduced: Use plaster spica at 60 degrees of flexion, 40 abduction and 20 internal rotation. For 6 wks. Then movement. If no concentric reduction: open reduction then spica for 3 mnths.

3. Children (> 4 yrs): Unilateral dislocation: Operative reduction up to the age of 10 yrs. May combine with osteotomy. In older children the force may cause AVN, so wait for pain or abnormal function for other surgeries. Bilateral dislocation: Deformity is symmetrical , less noticable Risk of operation is great bc of failure of one side causes asymmetry So most surgeons avoid operation unless pain or deformity is sever. ( hip replacement may be justified).

Avascular necrosis in DDH: The most serious complication ass with treatment of DDH Sequence of AVN: Femoral head deformity Acetabular dysplasia Lateral sublaxation of femoral head Relative overgrowth of greater trochanter Limb length inequalities Osteoarthrosis.

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