Developmental Dysplasia of the Hip(DDH) & Coxa Vara
DR. Ali Bakir Al-HilliAssist. Professor Fellowship, Pediatric & Spine Orthopedic/USADevelopmental Dysplasia of the Hip(DDH)
Theterm ‘congenital dislocation of the hip’ (CDH) hasbeen largely superseded by developmental dysplasia of the hip (DDH) in an attempt to describe the rangeand evolution of abnormalities that occur in this condition.This comprises a spectrum of disorders includingacetabular dysplasia without displacement,subluxation and dislocation.Normal hip development depends on proportionategrowth of the acetabular tri-radiate cartilages andthe presence of a concentrically located femoral head.Whether the instability comes first and then affectsacetabular development because of imperfect seatingof 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 innorthern Europe is approximately 1 per 1000 liveBirths.Girls are much more commonly affected, 7:1. The left hip is more oftenaffected than the right; in 1 in 5 cases the condition isbilateral.
Aetiology and pathogenesis
Genetic factors* generalized joint laxity (adominant trait), and *shallow acetabula (a polygenictrait which is seen mainly in girls and their mothers).Hormonal factors (e.g. high levels of maternaloestrogen, progesterone and relaxin in the last fewweeks of pregnancy).Intrauterine malposition (especially a breech positionwith extended legs) ‘packaging disorder’ .Postnatal factors
After weight-bearing commences, these changes areintensified. Both the acetabulum and the femoral neckremain anteverted and the pressure of the femoralhead induces a false socket to form above the shallowacetabulum.
Clinical features
The ideal is to diagnose every case atbirth. *For this reason, every newborn child should beexamined for signs of hip instability. *Where there is afamily history of congenital instability, and withbreech presentations or signs of other congenitalabnormalities, extra care is taken and the infant mayhave to be examined more than once.In Ortolani’s test, the baby’s thighs are heldwith the thumbs medially and the fingers resting onthe greater trochanters; the hips are flexed to 90degrees and gently abducted. Normally there issmooth abduction to almost 90 degrees. In congenitaldislocation the movement is usually impeded, butif pressure is applied to the greater trochanter there isa soft ‘clunk’ as the dislocation reduces, and then thehip abducts fully (the ‘jerk of entry’).
Barlow’s test is performed in a similar manner, buthere the examiner’s thumb is placed in the groin and,by grasping the upper thigh, an attempt is made tolever the femoral head in and out of the acetabulumduring abduction and adduction. If the femoral headis normally in the reduced position, but can be madeto slip out of the socket and back in again, the hip isclassed 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 lookasymmetrical and the leg is slightly short (Galeazzi’ssign) and externally rotated; a thumb in the groin mayfeel that the femoral head is missing.
With bilateraldislocation there is an abnormally wide perineal gap.Abduction is decreased.*Contrary to popular belief, late walking is not amarked feature; nevertheless, in children who do notwalk by 18 months dislocation must be excluded.Likewise, a limp or Trendelenburg gait, or a waddlinggait could be a sign of missed dislocation.
Imaging
Ultrasound scanning has replacedradiography for imaging hips in the newborn. Theradiographically ‘invisible’ acetabulum and femoralhead can, with practice, be displayed with static anddynamic ultrasound. Sequential assessment is straightforwardand allows monitoring of the hip during aperiod of splintage.Plain x-rays X-rays of infants are difficult to interpretand in the newborn they can be frankly misleading.This is because the acetabulum and femoral head are largely (or entirely) cartilaginous and therefore notvisible on x-ray. X-ray examination is more useful afterthe first 6 months, and assessment is helped by drawing
lines on the x-ray plate to define three geometric indices.
Perkins’ line & Hilgenreiner’s lineScreening
Neonatal screening in dedicated centers has led to amarked reduction in missed cases of DDH. Risk factors family history, breech presentation, oligohydramniosand the presence of other congenitalabnormalities are taken into account in selecting newborninfants for special examination and ultrasonography.Ideally all neonates should be examined.Management
THE FIRST 3–6 MONTHSWhere facilities for ultrasound scanning are available,all newborn infants with a high-risk background or asuggestion of hip instability are examined by ultrasonography.*If ultrasound is not available, the simplest policy isto regard all infants with a high-risk background or apositive Ortolani or Barlow test, as ‘suspect’ and tonurse them in double napkins or an abduction pillowfor the first 6 weeks. *At that stage they are re-examined:those with stable hips are left free but kept underobservation for at least 6 months; those with persistentinstability are treated by more formal abductionSplintage until the hip is stable and x-rayshows that the acetabular roof is developing satisfactorily(usually 3–6 months)
Splintage The object of splintage is to hold the hipssomewhat flexed and abducted; extreme positions areavoided 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 tosucceed; many surgeons would proceed straight toarthrography and open reduction.*Traction Even if closed reduction is unsuccessful (if necessary combined with psoasand adductor tenotomy) may help to loosen the tissuesand bring the femoral head down opposite theacetabulum. An arthrogram at this stage will clarifythe anatomy of the hip and show whether there is aninturned limbus or any marked degree of acetabulardysplasia.DISLOCATION IN CHILDREN OVER 4 YEARS
Reduction and stabilization become increasingly difficult. Nevertheless, in childrenbetween 4 and 8 years – especially if the dislocation isunilateral – it is still worth attempting, bearing inmind that the risk of avascular necrosis and hip stiffnessWith bilateral dislocation the deformity and thewaddling gait is symmetrical and therefore not sonoticeable; the risk of operative intervention is alsogreater because failure on one or other side turns thisinto an asymmetrical deformity. Therefore, avoid operation above the age of6 years. The untreated patient walks with a waddle butmay 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.