Disclosure The term congenital dislocation of the hip dates back to the time of Hippocrates. This condition, also known as hip dysplasia or developmental dysplasia of the hip (DDH), has been diagnosed and treated for several hundred years. Most notably, Ortolani, an Italian pediatrician in the early 1900s, evaluated, diagnosed, and began treating hip dysplasia (Ortolani, 1976). Galeazzi later reviewed more than 12,000 cases of DDH and reported the association between apparent shortening of the flexed femur and hip dislocation. Since that time, significant progress has been made in the evaluation and treatment of DDH. Problem: The definition of DDH is not universally agreed upon. According to Webster's Third New International Dictionary, dysplasia is defined as abnormal growth or development, thus making the term DDH somewhat redundant. 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 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. It 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:
Frequency: The overall frequency is usually reported as approximately 1 case per 1000 individuals, although Barlow believed that the instance of hip instability during newborn examinations was as high as 1 case per 60 newborns (Barlow, 1962). According to that study, more than 60% 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. Etiology: The etiology is not clear, but hip dysplasia does appear to be related to a number of different factors. One factor is racial background; among Native Americans and Laplanders, the prevalence of hip dysplasia is much higher (nearly 25-50 cases per 1000 persons), and the prevalence is very low among southern Chinese and African American populations (Getz, 1955; Hoaglund, 1973; Rabin, 1965; Skirving, 1979). 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 DDH compared with those whose parents did not (Bjerkreim, 1978). 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. Eighty percent of persons with DDH are female (Wilkinson, 1972), and the rate of breech positioning in children with DDH is approximately 20% (compared with 2-4% in the general population [Carter, 1964; Salter, 1968]). The prevalence of DDH in females born in breech position is as high as 1 case in 15 persons (Ramsey, 1976). Other musculoskeletal disorders of intrauterine malpositioning or crowding, such as metatarsus adductus and torticollis, have been reported to be associated with DDH (Kumar, 1982; Weiner, 1976). Oligohydramnios is also reported to be associated with an increased prevalence of DDH (Dunn, Clin Orthop 1976 119:11-22). 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 (Dunn, Clin Orthop 1976 119:11-22). Children in cultures in which the mother swaddles the baby, forcing the hips to be adducted, also have a higher rate of hip dysplasia (Kutlu, 1992). Hip dysplasia can be associated with underlying neuromuscular disorders, such as cerebral palsy, myelomeningocele, arthrogryposis, and Larsen syndrome, although this is not usually considered DDH. Pathophysiology: 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 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 do tend to have a shallow acetabulum (McKibbin, 1970; Ralis, 1973). This may provide a susceptible period in which abnormal positioning or a brief period of ligamentous laxity may result in hip instability. This characteristic is not as true for children of African American descent, who have a lower rate of DDH (Skirving, 1979). Clinical: Early clinical manifestations of 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 (Bond, 1997; Darmonov, 1996). 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. A clunk, similar to turning a light switch on or off, is felt when the hip is reduced. This should be performed gently, such that the fingertips do not blanch (Ortolani, 1976). Barlow described a test 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 (Barlow, 1962). Late clinical examination, 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 (Bjerkreim, 1978). 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. Examination should demonstrate that one leg appears shorter than the other. Although this is usually due to hip dislocation, realizing that any limb length discrepancy results in a positive Galeazzi sign is important. Additional physical examination findings for late dislocation include asymmetry of the gluteal thigh or labral skin folds, decreased abduction on the affected side, standing or walking with external rotation, and leg length inequality. Bilateral dislocation of the hip, especially at a later age, can be quite difficult to diagnose. This often manifests as a waddling gait with hyperlordosis. Many of the aforementioned clues for a unilateral dislocated hip are not present, such as the Galeazzi sign, asymmetrical thigh and skin folds, or asymmetrically decreased abduction. Careful examination is needed, and a high level of suspicion is important. Of primary importance is making the diagnosis of hip dislocation or dysplasia. Once this diagnosis is made, the patient should be examined to be sure he or she has no underlying medical or neuromuscular disorder. Proximal femoral focal deficiency can masquerade as hip dysplasia and often manifests similarly. Because the femoral head does not ossify, the radiographic appearance also may be deceiving. Other neuromuscular disorders can manifest as dysplasia later in life, such as Charcot-Marie-Tooth disease.
Indications for surgery are met if the results of the surgery would be better than the results of the natural progression of DDH. The natural history of hip dysplasia depends, in part, on the severity of the disease, bilaterality, and whether or not a false acetabulum is formed (Wedge, 1978). Unilateral dislocations result in significant leg length inequality, with a gait disturbance and possibly associated hip and knee pain. The development of a false acetabulum is associated with a poor outcome in approximately 75% of patients. Bilateral hip dislocation in a patient without false acetabuli has a better overall prognosis. In fact, a case was reported of a 74-year-old man with no history of hip or thigh pain whose dislocated hips were only discovered shortly before his death (Milgram, 1976). Indications for treatment depend on the patient's age and the success of the previous techniques. Children younger than 6 months with instability upon examination are treated with a form of bracing, usually a Pavlik harness. If this is not effective or if the hip instability or dislocation is noted when the child is older than 6 months, closed reduction is typically recommended, often with traction prior to the reduction. When the child is older than 2 years or with failure of the previous treatment, open reduction is considered. If the patient is older than 3 years, femoral shortening is performed instead of traction, with additional varus applied to the femur if necessary. A patient with residual acetabular dysplasia who is older than 4 years should be treated with an acetabular procedure. Treatment for DDH that is diagnosed when the patient is a young adult can be considered for residual acetabular dysplasia. Unfortunately, radiographic characterization of DDH that is severe enough to lead to early osteoarthrosis is difficult. A center-edge angle less than 16° often has been used to predict early osteoarthrosis (Wiberg, 1939), but other authors have found this measurement to be less reliable (Cooperman, 1983; Stulberg, 1974). Subluxation, defined as a break in the Shenton line, has been demonstrated to be associated with osteoarthrosis and decreased function (Cooperman, 1983).
Relevant Anatomy: The normal growth of the acetabulum depends on normal epiphyseal growth of the triradiate cartilage and on the 3 ossification centers located within the acetabular portion of the pubis (os acetabulum), ilium (acetabular epiphysis), and ischium. Additionally, normal growth of the acetabulum depends on normal interstitial appositional growth within the acetabulum (Ponseti, 1978). The presence of the spherical femoral head within the acetabulum is critical for stimulating normal development of the acetabulum (Harrison, 1961). The anatomy of the dislocated hip, especially after several months, often includes formation of a ridge called the neolimbus. Closed reduction is often unsuccessful at a later date, secondary to various obstacles to reduction. These include adductor and psoas tendon contraction, ligamentous teres, a transverse acetabular ligament, and pulvinar and capsular constriction. With long-standing dislocations, interposition of the labrum can also interfere with reduction (Dunn, Clin Orthop 1976 119:23-7; Fleissner, 1994; Noble, 1978; Ponseti, 1978). Contraindications: Relative contraindications to surgery include older age (>8 y for a unilateral hip dislocation or >4-6 y for bilateral hip dislocation, especially if a false acetabulum is not present). Other contraindications to surgery include a neuromuscular disorder, such as a high myelomeningocele or spinal cord injury, or cerebral palsy in a patient who has had a hip dislocation for more than 1 year. |
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Lab Studies:
Imaging Studies:
Diagnostic Procedures:
Medical therapy: The treatment of hip dysplasia begins with a careful examination of the newborn. If evidence of instability is present, a Pavlik harness should be considered and, if used, fitted appropriately (Mubarak, 1981; Pavlik, 1992; Viere, 1990). The Pavlik harness should be placed such that the chest strap is at the nipple line with 2 fingerbreadths of space between the chest and strap. The anterior strap is at the midaxillary line and should be set such that the hips are flexed to 100-110°. Excessive hip flexion can lead to femoral nerve compression and inferior dislocations. Quadriceps function should be determined at all clinic visits. The posterior abduction strap should be at the level of the child's scapula and adjusted to allow for comfortable abduction. This should prevent the hips from adducting to the extent that the hips dislocate. Excessive abduction should be avoided because of concern regarding the development of avascular necrosis. Fitting should then be checked clinically within the first week and then weekly thereafter. Carefully monitoring the patient to ensure the harness fits and the hips are reduced is important. Ultrasonography is an excellent means of documenting the reduction of the hip in the Pavlik harness and should be performed early in the course of treatment (Suzuki, 1993). If the hip is posteriorly subluxed, then the Pavlik harness therapy should be discontinued. Using the Pavlik harness for guided reduction, which occurs when the hip does not completely reduce initially but is pointed towards the triradiate cartilage, is controversial. When the harness is used for guided reduction, the physician should obtain a radiograph after the Pavlik harness is placed to determine if the femoral heads are pointing towards the triradiate cartilage. An ultrasonogram should be obtained to determine the success, or lack thereof, of the guided reduction. The overall duration of Pavlik harness therapy has not been universally agreed upon. If the hip is reduced satisfactorily in the harness, then the author maintains this treatment at least until the hip is stable clinically and based on ultrasound findings with the patient out of the brace. Abduction splinting is maintained thereafter if radiographic evidence of residual dysplasia is present. The use of an abduction brace after a failure of the Pavlik harness has been suggested. In one study, 13 of 15 patients were treated successfully in this manner and the remaining 2 patients had a successful closed reduction (Hedequist, 2002). When the patient is older than 6 months, the success rate with a Pavlik harness is less than 50%; therefore, it should not be used in patients older than 6 months (Weinstein, 2001). If the child is diagnosed when older than 6 months or if the Pavlik harness is determined to be unsuccessful, a closed reduction is attempted. Often, traction is performed for a 2- to 3-week period before closed reduction is attempted. Traction (usually skin traction) can be performed either at home or in the hospital. This must be monitored carefully to ensure the integrity of the skin. The overall benefit of traction is quite controversial, although most pediatric orthopedic surgeons do use skin traction (Fish, 1991; Wenger, 1995). Closed reduction is typically performed with the aid of arthrography, which is used to determine the adequacy of the reduction. A medial dye pool and an interposing limbus are both associated with a poor prognosis. If, on the other hand, a sharp or even a blunted limbus and no medial dye pooling are present, prognosis is good (Fleissner, 1994). Also, the safe zone of Ramsey, which is the angle between maximum abduction and minimum abduction in which the hip remains reduced, should be at least 25° and can be increased with release of the adductor longus. The cone of stability has also been defined; it is a cone that involves hip flexion, abduction, and internal/external rotation. If this cone measures greater than 30°, it is considered satisfactory (Fleissner, 1994). A spica cast is placed, with care taken in molding over the posterior aspect of the greater trochanter of the ipsilateral limb. After this is performed, a CT scan is then obtained to ensure that no evidence of posterior subluxation is present. The cast is typically worn for 6-12 weeks, at which time the hip is reexamined, and, if found to be stable, the patient is placed in an abduction brace. If it remains unstable, the patient is again placed in a spica cast. Surgical therapy: Open reduction is the treatment of choice for children older than 2 years at the time of initial diagnosis or for children in whom attempts at closed reduction have failed. In children with teratologic hips, with failure at a much younger age, open reduction can be performed through a medial approach. The medial approach has a number of advantages, as follows:
Problems with this approach include the possibility of increased avascular necrosis, the potential lack of familiarity of surgeons with this approach, and the inability to perform capsular placation or a pelvic procedure through this incision. With the use of a medial approach, the cast plays a much more important role. Most often, especially in older children, the standard anterolateral or Smith-Petersen approach is used. This can be combined with a capsule placation, if needed, and/or an acetabular procedure. In a child older than 3 years, femoral shortening is typically performed instead of traction (Schoenecker, 1984) (see Image 3). At that time, if proximal femoral dysplasia is present, such as that observed with significant anteversion or coxa valga, this can also be corrected. Whether traction or femoral shortening should be performed in children aged 2-3 years is controversial. Pelvic osteotomy may be needed for residual hip dysplasia. When this should occur is, again, somewhat controversial. Some authors suggest pelvic osteotomy in children as young as 18-24 months, while others suggest waiting until children are aged at least 4 years. If open reduction is performed in a child older than 4 years with significant hip dysplasia, an acetabular procedure should be considered at the time of open reduction. If closed reduction is performed earlier, at least 12-18 months of acetabular remodeling should be allowed before an acetabular procedure is undertaken. At that time, if no evidence of acetabular modeling is noted, a pelvic osteotomy should be considered. Postoperative details: When open reduction is performed, a spica cast is worn for 6 weeks. The patient is then placed in an abduction orthosis. Follow-up care: The duration a child remains in hip orthosis is quite controversial and depends on the treating physician's experience and the individual patient.
Numerous possible complications can occur, including redislocation, stiffness of the hip, infection, blood loss, and, possibly the most devastating, necrosis of the femoral head. The rate of femoral head necrosis varies significantly; depending on the study, the rate is 0-73% (Keret, 1991). Numerous studies demonstrate that extreme abduction, especially combined with extension and internal rotation, results in a higher rate of avascular necrosis (Fogarty, 1981; Schoenecker, 1978).
Overall, the prognosis for children treated for hip dysplasia is very good, especially if the dysplasia is managed with closed treatment. If closed treatment is unsuccessful and open reduction is needed, the outcome is less favorable, although short-term outcome appears to be satisfactory. If secondary procedures are needed to obtain reduction, then the overall outcome is significantly worse.
Early diagnosis is the most crucial aspect of the treatment of children with DDH. The use of ultrasonography and other diagnostic imaging modalities and the implementation of improved educational programs will most likely decrease the number of children with DDH diagnosed late. Newer, less invasive surgical techniques (eg, endoscopic techniques, image-guided surgery) are currently being developed in an effort to decrease the morbidity of surgery and to ease recovery.
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