DR. Ali Bakir Al-Hilli Assist. Professor Fellowship, Pediatric & Spine Orthopedic/USA Developmental Dysplasia of the Hip(DDH) & Coxa Vara

Developmental Dysplasia of the Hip(DDH) The term ‘congenital dislocation of the hip’ (CDH) has been largely superseded by developmental dysplasia of the hip (DDH) in an attempt to describe the range and evolution of abnormalities that occur in this condition. This comprises a spectrum of disorders including acetabular dysplasia without displacement, subluxation and dislocation.

Normal hip development depends on proportionate growth of the acetabular tri-radiate cartilages and the presence of a concentrically located femoral head. Whether the instability comes first and then affects acetabular development because of imperfect seating of the femoral head, or is a result of a primary acetabular dysplasia, is still uncertain. Both mechanisms might be important.

The reported incidence of neonatal hip instability in northern Europe is approximately 1 per 1000 live Births. Girls are much more commonly affected, 7:1. The left hip is more often affected than the right; in 1 in 5 cases the condition is bilateral.

Aetiology and pathogenesis Genetic factors * generalized joint laxity (a dominant trait), and *shallow acetabula (a polygenic trait which is seen mainly in girls and their mothers). Hormonal factors (e.g. high levels of maternal oestrogen, progesterone and relaxin in the last few weeks of pregnancy). Intrauterine malposition (especially a breech position with extended legs) ‘packaging disorder’. Postnatal factors

After weight-bearing commences, these changes are intensified. Both the acetabulum and the femoral neck remain anteverted and the pressure of the femoral head induces a false socket to form above the shallow acetabulum.

Clinical features The ideal is to diagnose every case at birth. *For this reason, every newborn child should be examined for signs of hip instability. *Where there is a family history of congenital instability, and with breech presentations or signs of other congenital abnormalities, extra care is taken and the infant may have to be examined more than once.

In Ortolani’s test, the baby’s thighs are held with the thumbs medially and the fingers resting on the greater trochanters; the hips are flexed to 90 degrees and gently abducted. Normally there is smooth abduction to almost 90 degrees. In congenital dislocation the movement is usually impeded, but if pressure is applied to the greater trochanter there is a soft ‘clunk’ as the dislocation reduces, and then the hip abducts fully ( the ‘jerk of entry ’).

Barlow’s test is performed in a similar manner, but here the examiner’s thumb is placed in the groin and, by grasping the upper thigh, an attempt is made to lever the femoral head in and out of the acetabulum during abduction and adduction. If the femoral head is normally in the reduced position, but can be made to slip out of the socket and back in again, the hip is classed as ‘ dislocatable ’ (i.e. unstable).

Late features An observant mother may spot asymmetry, a clicking hip, or difficulty in applying the napkin (diaper) because of limited abduction.

With unilateral dislocation the skin creases look asymmetrical and the leg is slightly short (Galeazzi’s sign) and externally rotated; a thumb in the groin may feel that the femoral head is missing.

With bilateral dislocation there is an abnormally wide perineal gap. Abduction is decreased. *Contrary to popular belief, late walking is not a marked feature; nevertheless, in children who do not walk by 18 months dislocation must be excluded. Likewise, a limp or Trendelenburg gait, or a waddling gait could be a sign of missed dislocation.

Imaging Ultrasound scanning has replaced radiography for imaging hips in the newborn. The radiographically ‘invisible’ acetabulum and femoral head can, with practice, be displayed with static and dynamic ultrasound. Sequential assessment is straightforward and allows monitoring of the hip during a period of splintage.

Plain x-rays X-rays of infants are difficult to interpret and in the newborn they can be frankly misleading. This is because the acetabulum and femoral head are largely (or entirely) cartilaginous and therefore not visible on x-ray. X-ray examination is more useful after the first 6 months, and assessment is helped by drawing

lines on the x-ray plate to define three geometric indices.

Perkins’ line & Hilgenreiner’s line

Screening Neonatal screening in dedicated centers has led to a marked reduction in missed cases of DDH. Risk factors family history, breech presentation, oligohydramnios and the presence of other congenital abnormalities are taken into account in selecting newborn infants for special examination and ultrasonography. Ideally all neonates should be examined.

Management THE FIRST 3–6 MONTHS Where facilities for ultrasound scanning are available, all newborn infants with a high-risk background or a suggestion of hip instability are examined by ultrasonography.

*If ultrasound is not available, the simplest policy is to regard all infants with a high-risk background or a positive Ortolani or Barlow test, as ‘suspect’ and to nurse them in double napkins or an abduction pillow for the first 6 weeks. *At that stage they are re-examined: those with stable hips are left free but kept under observation for at least 6 months; those with persistent instability are treated by more formal abduction Splintage until the hip is stable and x-ray shows that the acetabular roof is developing satisfactorily (usually 3–6 months)

Splintage The object of splintage is to hold the hips somewhat flexed and abducted; extreme positions are avoided and the joints should be allowed some movement in the splint. The three golden rules of splintage are: (1)the hip must be properly reduced before it is splinted. (2) extreme positions must be avoided. (3) the hips should be able to move.

PERSISTENT DISLOCATION: 6–18 MONTHS If the hip is still incompletely reduced, or if the child presents late with a ‘missed’ dislocation, the hip must be reduced by closed methods or operation, and held reduced until acetabular development is satisfactory. Closed reduction is suitable after the age of 3 months. General anaesthesia with an arthrogram to confirm a concentric reduction.

PERSISTENT DISLOCATION: 18 MONTHS – 4 YEARS In the older child, closed reduction is less likely to succeed; many surgeons would proceed straight to arthrography and open reduction. *Traction Even if closed reduction is unsuccessful (if necessary combined with psoas and adductor tenotomy) may help to loosen the tissues and bring the femoral head down opposite the acetabulum. An arthrogram at this stage will clarify the anatomy of the hip and show whether there is an inturned limbus or any marked degree of acetabular dysplasia.

DISLOCATION IN CHILDREN OVER 4 YEARS Reduction and stabilization become increasingly difficult. Nevertheless, in children between 4 and 8 years – especially if the dislocation is unilateral – it is still worth attempting, bearing in mind that the risk of avascular necrosis and hip stiffness

With bilateral dislocation the deformity and the waddling gait is symmetrical and therefore not so noticeable; the risk of operative intervention is also greater because failure on one or other side turns this into an asymmetrical deformity. Therefore, avoid operation above the age of 6 years. The untreated patient walks with a waddle but may be surprisingly uncomplaining.

COXA VARA The normal femoral neck–shaft angle is 160 degrees. at birth, decreasing to 125 degrees in adult life. less than 120 degrees is called coxa vara. Congenital or Acquired.

CONGENITAL COXA VARA It is due to a defect of endochondral ossification in the medial part of the femoral neck. When the child starts to crawl or stand, the femoral neck bends, and with continued Weight bearing it collapses increasingly.

Clinical features *The condition is usually diagnosed when the child starts to walk. *The leg is short and the thigh may be bowed. *X-rays show that the femoral neck is in varus and abnormally short. * A helpful alternative is to measure Hilgenreiner’s epiphyseal angle – the angle subtended by a horizontal line joining the centre (triradiate cartilage) of each hip and another parallel to the physeal line; the normal angle is about 30 degrees. *At maturity the deformity may be quite bizarre.

Treatment *If the epiphyseal angle is degrees, the child should be kept under observation and re-examined at intervals for signs of progression. *If it is more than 60 degrees, or if shortening is progressive, the deformity should be corrected by a subtrochanteric or intertrochanteric valgus osteotomy.