Congenital Hip Dysplasia

Congenital hip dysplasia A malformation of the hip joint that is present at birth. Genetic factors likely play a role in this disorder. Features include hip dislocation, asymmetry of leg positions, asymmetric fat folds, and diminished movement on the affected side. Some children will exhibit little or no features and must be diagnosed by physical examination of the hip joints.

Causes of Congenital hip dysplasia Clinical studies show a familial tendency toward Congenital hip dysplasia, with more females affected than males. This disorder is found in many cultures around the world. However, statistics show that the Native American population has a high incidence of hip dislocation. This has been documented to be due to the common practice of swaddling and using cradleboards for restraining the infants. This places the infant's hips into extreme adduction (brought together). The incidence of congenital Congenital hip dysplasia is also higher in infants born by caesarian and breech position births. Evidence also shows a greater chance of this hip abnormality in the first born compared to the second or third child. Hormonal changes within the mother during pregnancy, resulting in increased ligament laxity, is thought to possibly cross over to the placenta and cause the baby to have lax ligaments while still in the womb. Other symptoms of complete dislocation include a shortening of the leg and limited ability to abduct the leg.

Treatment of Congenital hip dysplasia The objective of treatment is to replace the head of the femur into the acetabulum and, by applying constant pressure, to enlarge and deepen the socket. In the past, stabilization was achieved by placing rolled cotton diapers or a pillow between the thighs, thereby keeping the knees in a frog like position. More recently the Pavlik harness and von Rosen splint are commonly used in infants up to the age of six months. A stiff shell cast may be used, which achieves the same purpose, spreading the legs apart and forcing the head of the femur into the acetabulum. In some cases, in older children between six to 18 months, surgery may be necessary to reposition the joint. Also at this age, the use of closed manipulation may be applied successfully, by moving the leg around manually to replace joint. Operations are not only performed to reduce the dislocation of the hip, but also to repair a defect in the acetabulum. A cast is applied after the operation to hold the head of the femur in the correct position. The use of a home traction program is now more common. However, after the age of eight years, surgical procedures are primarily done for pain reduction measures only. Total hip surgeries may be inevitable later in adulthood.

dislocation

Problem The definition of developmental dysplasia of the hip (DDH) is not universally agreed upon. Typically, the term DDH is used when referring to patients who are born with dislocation or instability of the hip, which may then result in hip dysplasia.

A broader definition of DDH is simply abnormal growth of the hip. Abnormal development of the hip includes the osseous structures, such as the acetabulum and the proximal femur, and the labrum, capsule, and other soft tissues. This condition may occur at any time, from conception to skeletal maturity. The author prefers to use the term hip dysplasia because he believes this term is simpler and more accurate. Internationally, this disorder is still referred to as congenital dislocation of the hip. More specific terms are often used to better describe the condition; these are defined as follows: • • • •

Subluxation – This is incomplete contact between the articular surfaces of the femoral head and acetabulum. Dislocation – This refers to complete loss of contact between the articular surface of the femoral head and acetabulum. Instability – This consists of the ability to subluxate or dislocate the hip with passive manipulation. Teratologic dislocation – This refers to antenatal dislocation of the hip.

Frequency The overall frequency of developmental dysplasia of the hip (DDH) is usually reported as approximately 1 case per 1000 individuals, although Barlow believed that the incidence of hip instability during newborn examinations was as high as 1 case per 60 newborns.5 According to his study, more than 60% of hip instability became stable by age 1 week, and 88% became stable by age 2 months, leaving only 12% (of the 1 in 60 newborns, or 0.2%) with residual hip instability.5

Etiology The etiology of hip dysplasia is not clear, but this condition does appear to be related to a number of different factors.6 One such factor is racial background; among Native Americans and Laplanders, the prevalence of hip dysplasia is much higher (nearly 25-50 cases per 1000 persons) than other races, and the prevalence is very low among southern Chinese and black populations.7,8,9,10 An underlying genetic disposition also appears to exist in that a 10-fold increase in the frequency of hip dysplasia occurs in children whose parents had developmental dysplasia of the hip (DDH) compared with those whose parents did not.11 Other factors possibly related to DDH include intrauterine positioning and sex, and some of these are interrelated. Female sex, being the first-born child, and breech positioning are all associated with an increased prevalence of DDH. An estimated 80% of persons with DDH are female,12 and the rate of breech positioning in children with DDH is approximately 20% (compared with 2-4% in the general population).13,14 The prevalence of DDH in females born in breech position has been estimated to be as high as 1 case in 15 persons in some studies.15

Other musculoskeletal disorders of intrauterine malpositioning or crowding, such as metatarsus adductus and torticollis, have been reported to be associated with DDH.16,17 Oligohydramnios is also reported to be associated with an increased prevalence of DDH.18 The left hip is more commonly associated with DDH than the right, and this is believed to be due to the common intrauterine position of the left hip against the mother's sacrum, forcing it into an adducted position.18 Children in cultures in which the mother swaddles the baby, forcing the infant's hips to be adducted, also have a higher rate of hip dysplasia.19 Hip dysplasia can be associated with underlying neuromuscular disorders, such as cerebral palsy, myelomeningocele, arthrogryposis, and Larsen syndrome, although these are not usually considered DDH.

Pathophysiology Developmental dysplasia of the hip (DDH) involves abnormal growth of the hip. Ligamentous laxity is also believed to be associated with hip dysplasia, although this association is less clear. DDH is not part of the classic description of disorders that are associated with significant ligamentous laxity, such as Ehlers-Danlos syndrome or Marfan syndrome. Children often have ligamentous laxity at birth, yet their hips are not usually unstable; in fact, it takes a great deal of effort to dislocate a child's hip. Therefore, more than just ligamentous laxity may be required to result in DDH. At birth, white children tend to have a shallow acetabulum.20,21 ; this may provide a susceptible period in which abnormal positioning or a brief period of ligamentous laxity may result in hip instability. However, this characteristic is not as true for children of black descent, who have a lower rate of DDH.10

Presentation Early clinical manifestations of developmental dysplasia of the hip (DDH) are identified during examination of the newborn. The classic examination finding is revealed with the Ortolani maneuver; a palpable "clunk" is present when the hip is reduced in and out of the acetabulum and over the neolimbus. A high-pitched "click" (as opposed to a clunk) in all likelihood has little association with acetabular pathology.22,23 Ortolani originally described this clunk as occurring with either subluxation or reduction of the hip (in or out of the acetabulum). More commonly, the Ortolani sign is referred to as a clunk, felt when the hip reduces into the acetabulum, with the hip in abduction. To perform this maneuver correctly, the patient must be relaxed. Only one hip is examined at a time. The examiner's thumb is placed over the patient's inner thigh, and the index finger is gently placed over the greater trochanter. The hip is abducted, and gentle pressure is placed over the greater trochanter. In the presence of DDH, a clunk, similar to turning a light switch on or off, is felt when the hip is reduced. The Ortolani maneuver

should be performed gently, such that the fingertips do not blanch.24 Barlow described another test for DDH that is performed with the hips in an adducted position, in which slight gentle posterior pressure is applied to the hips. A clunk should be felt as the hip subluxes out of the acetabulum.5 The clinical examination for late DDH, when the child is aged 3-6 months, is quite different. At this point, the hip, if dislocated, is often dislocated in a fixed position.11 The Galeazzi sign is a classic identifying sign for unilateral hip dislocation (see Image 1). This is performed with the patient lying supine and the hips and knees flexed. The examination should demonstrate that one leg appears shorter than the other. Although this finding is usually due to hip dislocation, realizing that any limb-length discrepancy results in a positive Galeazzi sign is important.

The Galeazzi sign is a classic identifying sign for unilateral hip dislocation. To elicit the sign, the patient lies supine and the hips and knees are flexed. The examination should demonstrate that one leg appears shorter than the other. Although this appearance is usually due to a hip dislocation, realizing that any limb-length discrepancy results in a positive Galeazzi sign is important. Ankle fractures: The ankle bones and ligaments form a ring that connects the tibia and fibula to the talus and calcaneus. Within the ring, stability is provided by 2 bones (the medial malleolus of the tibia and lateral malleolus of the fibula) and 2 ligament complexes (medially, the deltoid ligament; laterally, mainly the anterior and posterior talofibular ligaments and calcaneofibular ligament—see Fig. 7: Fractures, Dislocations, and Sprains: Ligaments of the ankle. ). Ankle fractures are common and can result from multiple injury mechanisms. Fractures that disrupt the ring in one place often disrupt it in another (eg, if only one bone is fractured, a ligament is often simultaneously and severely torn). If fractures disrupt ≥ 2 of the structures stabilizing the ankle ring, the ankle is unstable. Disruption of the medial deltoid ligament also causes instability. For unstable injuries, surgery may be required, and prognosis is guarded. Most stable ankle fractures without other indications for surgery can be treated with a cast for 6 wk; prognosis is good.

Fig. 7 Ligaments of the ankle.

Fractures of the 2nd metatarsal bone base with dislocation (Lisfranc's fracturedislocation): The usual mechanism is a fall on a foot in plantar flexion. Usually there is significant soft-tissue swelling. These rare fractures are difficult to appreciate on plain xrays and are often misdiagnosed, leading to sometimes serious complications, such as osteoarthritis and rarely compartment syndrome. A plain x-ray can show a fracture at the base of the 2nd metatarsal or chip fractures of the cuneiform but may not show disruption of the tarsometatarsal joint, which should be suspected even if it is not visible on plain xrays. Dislocations often spontaneously reduce, but immediate referral, usually for closed reduction, which requires general anesthesia, may be warranted. Fractures of the 5th metatarsal bone base (dancer's fracture): The usual injury mechanism is a twist (typically, inversion) or crush injury. These fractures usually heal relatively quickly; nonunion is uncommon. Treatment is a protective walking shoe. Fractures of the 5th metatarsal bone diaphysis (Jones fracture): The usual injury mechanism is a crush injury. These fractures are less common than those of the metatarsal bone base, and delayed union or nonunion occurs more commonly. Treatment is a cast that immobilizes the ankle. Avulsion fractures of the base of the fifth metatarsal can occur with inversion ankle injuries and are less significant than a true Jones fracture, the latter being predisposed to nonunion. Toe fractures: The usual injury mechanism is a crush injury. Unless rotational deformity or joint involvement is suspected or the proximal phalanx of the great toe is injured, xrays are usually unnecessary. Treatment is taping the injured toe to an adjacent toe (dynamic splinting or buddy taping). Markedly displaced toe fractures should be reduced to restore alignment.