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Biology 103
2002 Second Paper
On Serendip

The Hip Questions

Katie Campbell

Controversy surrounds the abnormal development of the acetabulum and femoral joint in infants, the hip. The definition of Congenital Hip Dysplasia or Developmental Dislocation of the Hip (CHD/DDH) is a variety of types and degrees of severity diagnosed by the many tests that are used for its diagnosis. Treatments vary as well and by far the most confusing question to CHD/DDH is the question of its root cause. Congenital Hip Dysplasia is thought to "run in families" (1) and many statistics support the assumption that it is a concern of genetics. However, other research has also observed that an infant has the probability of developing problems with the hip in the womb and after birth, unassociated with the genetic factor, identifying the disorder as Developmental Dislocation of the Hip. Whether one identifies with the evidence to support its heredity or the idea that any child can suffer from a deformed femur and acetabulum through any fault of development, it is important to be aware of CHD/DDH affecting one to five children per 1,000 births (3), how it is diagnosed, the different degrees of severity to which it occurs and the multiple choices in treatment.

CHD/DDH is the abnormal formation of the hip joint, causing easy subluxation or dislocation of the hip. The hip joint, a "ball and socket" joint, is comprised of the acetabulum, the socket and the head of the femur, the ball. There are three main classifications of CHD/DDH. Dysplasia is the term to describe just the "abnormal development" or malformation of the femur and/or the acetabulum. Subluxation classifies a partially dislocated hip and a further classification is a completely dislocated hip. A four tiered scale developed by Dr. Crowe in 1979 is used in diagnosing newborns to identify the severity of malformation and degree of dislocation. Crowe I is the least severe; the femur and acetabulum are almost normally developed and there is less than fifty percent dislocation. Crowe II hips result from abnormal development of the acetabulum and a fifty to seventy-five percent dislocation. In Crowe III stage, the acetabulum lacks a roof and so the femur portion creates a "false acetabulum" using the pelvis, resulting in complete dislocation. "High hip dislocation" can be used to describe the classification of Crowe IV because the acetabulum is completely underdeveloped and the femur sits high on the pelvis in attempt to form some sort of joint articulation. (1)

To diagnose CHD/DDH and indicate the degree of severity a variety of tests are routinely performed on newborns. The Barlow test is positive, when the "hip is flexed...thigh adducted [and] pushing posteriorly in ling of the shaft of [the] femur causing [the] femoral head to dislocate posteriorly from [the] acetabulum" (7). This however is not entirely conclusive of CHD/DDH and it is confirmed by the performance of Ortolani's test. The Ortolani test involves bringing the "femoral head from its dislocated posterior position to opposite the acetabulum," reducing the dislocated hip, otherwise described as bringing it back into proper positioning (6). If positive, this produces an audible "clunk" as the hip is reduced. The Barlow test shows that a hip has the potential to dislocate whereas the Ortolani test confirms its dislocation. Because both of these physical tests require experience and specific skills to identify the feelings and sounds of positive results, controversy surrounds the use of the Barlow and Ortolani tests. Examination by x-ray and ultrasound has become an additional tool in diagnosis. X-ray, however is less common because whereas it shows the hip in one fixed position, ultrasound can allow the hip to be seen in many positions and during movement. Ultrasound was first developed as a CHD/DDH diagnostic tool in 1978 to confirm positive physical tests and identify the degree of abnormality of the hip. A scaled developed by Graf is based on the depth and shape of the acetabulum as viewed in ultrasound and is similar to the Crowe scale described earlier. A type one is normal and no treatment is necessary while a type two hip has a shallow acetabular cup and is just "developmentally immature" in infants less than three months but should be treated in those older. In type three the hip is partially dislocated and in four is completely dislocated, both requiring treatment. (5) Other general symptoms that prompt further examination is a discrepancy in leg lengths, asymmetrical skin folds around the pelvic area, and a limp.

Just as there are many different degrees of dislocation and dysplasia (malformation) associated with this disorder, there are many different treatments. The purpose of treatment is to force correct development of the acetabulum so that the femoral head can sit properly in the joint and further subluxation or permanent dislocation does not ensue. The most common and perhaps simple way of achieving such an effort is the use of the Pavlik harness, von Rosen splint, or a stiff shell cast. Each are used on infants in the first six months of life to spread the infant's legs apart and force the femoral head into the acetabulum, applying pressure to "enlarge and deepen the socket" (2) and develop the hip normally. Closed manipulation repositions the joint by moving the leg around to get the femoral head in the proper location. In cases of children older than six months and other severe cases, treatments can involve surgery. Surgery manually repositions the joint. Before the age of four, femoral osteotomies are performed to reconstruct the hip. Pelvic osteotomies are performed after the age of four to limit instability and reduce the dislocation of the hip (1). A malformed joint and dislocated hip is obviously not fatal but treatment is important because the resulting pain is often unbearable. If undetected CHD/DDH can cause severe, painful arthritis as the forces of weight bearing wear down the cartilage of the femoral head that usually allows for comfortable and easy motion of the joint. CHD/DDH left undetected requires later treatments involving the use of anti-inflammatories, walking devices (such as a cane), physical therapy, and most often a resort to total hip replacements to correct hip alignment (1).

Despite the variety of CHD/DDH types and treatments, CHD/DDH is fairly uncommon only resulting in 1.5 births per thousand, although with more specified examination techniques this number is possibly as high as 5 births per thousand. It is hard to connect each case with one another and determine the specific cause of CHD/DDH. There are significant similarities in cases of hip malformation that have suggested the genetic causes of CHD/DDH. In many cases, CHD/DDH has "run in families" (1) and in particular ethnic groups. The prevalence in North American Indian communities has often been as high as 35 cases in one thousand births (3) and a frequency in the Lapp community, the natives of Norway (4). Also, since the majority of cases are of the left hip in female infants as well as the first born genetics could connect these cases. It has been observed that there is an increased incidence in mothers that carry a high level of a particular collagen, a bone and cartilage building material (1), often have CHD/DDH newborns. Also, mother's with high hormonal changes and a strong estrogen presence during pregnancy results in "increased ligament laxity...thought to cross over the placenta and cause the baby to have lax ligaments" (2) affecting the development of the hip. Causes of CHD/DDH are then tied together in common hereditary features.

CHD/DDH is also argued to be purely developmental, meaning it could result in any person just based on particular physical situations. For example, CHD/DDH is common in breech and caesarian births probably because of the positioning and pressure on the acetabulum and femur. Another argument is that in the case of increased incidence in the Native communities of North America and Norway is not that genetics play a role, because the practice of swaddling and use of cradleboards results in "extreme adduction" (2), bringing the hips together and displacing the femoral head from proper positioning in the acetabulum. Developmentally, the femoral head has reached its maturity in the womb while the acetabulum completes its development in the first few months of life (3). In cases of unusual positioning of the hips the acetabulum could fail to properly develop its superior position, thus allowing dislocation. Finally, because some cases of diagnosed CHD/DDH self-correct with the completed development of the acetabulum in the first few months of life it could be possible that this development of normalcy is in much the same manner as the chance that the dislocation is a developed disorder.

While CHD/DDH is simply defined as the subluxation or complete dislocation of the hip joint, the variety in which it presents itself, confusion in diagnosis and the controversy surrounding the identity of its cause makes CHD/DDH truly complicated. Whatever the root cause, it is fortunate the answers are sought to the questions raised. Increasing awareness allows more and more infants to be diagnosed and treated, usually resulting in 90% success (4). Complication in understanding CHD/DDH is beneficial, as it allows for more observation of cases and the further discovering and understanding the phenomena behind it and within it.


World Wide Web Sources

1)Total Hip Replacement in Congenital Hip Dysplasia, useful general CHD information resource, also delving into the subject of the treatment of hip replacement.

2)Congenital Hip Dysplasia, general information source, including good introduction of common treatments.

3)Developmental Dislocation of the Hip, comprehensive notes of occurance statistics, risk factors, treatments, and links to sites that futher explain tests and treatments.

4)What is Hip Dysplasia?, general information and brief history of the common Pavlik harness treatment.

5)Screening for Developmental Dysplasia of the Hip, comprehensive overview of CHD/DDH complete with good visual resources.

6)Ortolani's Test: for Congenital Hip Dislocation, simple and understandable description of the Ortolani test.

7)Barlow's Test, simple and understandable description of the Barlow test.

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