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REVIEW ARTICLE |
a Department of Pediatrics
b Oregon Evidence-Based Practice Center, Oregon Health and Science University, Portland, Oregon
c Department of Pediatrics, University of Texas Health Science Center, Houston, Texas
d Department of Primary Care Research, Olmsted Medical Center, Rochester, Minnesota
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ABSTRACT |
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 TOP ABSTRACT METHODSRESULTSDISCUSSIONFUTURE RESEARCHREFERENCES |
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OBJECTIVE. We sought to gather and synthesize the published evidence regarding screening for DDH by primary care providers.
METHODS. We performed a systematic review of the literature by using a best-evidence approach as used by the US Preventive Services Task Force. The review focused on screening relevant to primary care in infants from birth to 6 months of age and on interventions used in infants before 1 year of age.
RESULTS. The literature on screening and interventions for DDH suffers from significant methodologic shortcomings. No published trials directly link screening to improved functional outcomes. Clinical examination and ultrasound identify somewhat different groups of newborns who are at risk for DDH. A significant proportion of hip abnormalities identified through clinical examination or ultrasound in the newborn period will spontaneously resolve. Very few studies examine the functional outcomes of patients who have undergone therapy for DDH. Because of the high rate and unpredictable nature of spontaneous resolution of DDH and the absence of rigorous comparative studies, the effectiveness of interventions is not known. All surgical and nonsurgical interventions have been associated with avascular necrosis of the femoral head, the most common and most severe harm associated with all treatments of DDH.
CONCLUSIONS. Screening with clinical examination or ultrasound can identify newborns at increased risk for DDH, but because of the high rate of spontaneous resolution of neonatal hip instability and dysplasia and the lack of evidence of the effectiveness of intervention on functional outcomes, the net benefits of screening are not clear.
Key Words: developmental dysplasia of the hip • DDH • hip dysplasia • mass screening • infants • systematic review
Abbreviations: DDH—developmental dysplasia of the hip • AVN—avascular necrosis • CTFPHC—Canadian Task Force on Preventive Health Care • AAP—American Academy of Pediatrics • RCT—randomized • controlled trial
Developmental dysplasia of the hip (DDH) represents a spectrum of anatomic abnormalities in which the femoral head and the acetabulum are in improper alignment and/or grow abnormally. The precise definition of DDH is controversial.1,2 The spectrum includes hips that are dysplastic, subluxated, dislocatable, and dislocated. Clinical instability of the hip is the traditional hallmark of the disorder. In an unstable hip, the femoral head and acetabulum may not have a normal, tight, concentric anatomic relationship, which can lead to abnormal growth of the hip joint and may result in permanent disability. DDH can lead to premature degenerative joint disease, impaired walking, and chronic pain.
Estimates of the incidence of DDH in infants vary between 1.5 and 20 per 1000 births.3 The incidence of DDH in infants is influenced by a number of factors, including diagnostic criteria, gender, genetic and racial factors, and age of the population in question.4 The reported incidence has increased significantly since the advent of clinical and sonographic screening, which suggests possible overdiagnosis.2 In addition to a higher prevalence of DDH in females, reported risk factors for the development of DDH include a family history of DDH, breech intrauterine positioning, and additional in utero postural deformities.5–7 However, the majority of cases of DDH have no identifiable risk factors.8
Self-limited hip instability is a common finding in newborns.9 More than 80% of clinically unstable hips noted at birth have been shown to resolve spontaneously.10 Because of the potential for subsequent impairment and the widespread belief that earlier treatment leads to improved outcomes, screening newborns for DDH has become commonplace. However, the high rate of spontaneous resolution raises uncertainty about the most appropriate plan of action when a newborn has a positive screening examination for an unstable hip.
Intervention for DDH includes both nonsurgical and surgical options. A variety of abduction devices are used to treat DDH nonsurgically, with the Pavlik method among the most common. These devices place the legs and hips in an abducted and flexed position in an effort to promote proper alignment and stabilization of the hip joint. The duration of treatment varies from center to center. Complications of nonsurgical therapy are not trivial, with avascular necrosis (AVN) of the femoral head among the most serious.3
Surgical intervention may be necessary when DDH is severe, when it is diagnosed late, or after an unsuccessful trial of nonsurgical methods.11 Many surgical procedures are used to treat DDH, most of which involve manual reduction of the femoral head into the acetabulum, with or without additional procedures on the adductor and/or iliopsoas tendons, the femur, or the acetabulum. Preoperative management may include a period of traction, and postoperative management typically includes a period of fixed positioning in a spica cast. The duration and specific approach to preoperative and postoperative management are highly variable. Surgical intervention places the hip at risk of AVN in addition to standard operative risks that include general anesthesia, intraoperative complications, and postoperative wound infections.
This evidence synthesis assesses the literature on screening and intervention for DDH. It was conducted for the US Preventive Services Task Force, which had no previous recommendations for this condition. Two systematic reviews of DDH have been published previously, one by the Canadian Task Force on Preventive Health Care (CTFPHC)3 and another by the American Academy of Pediatrics (AAP).1,4 This evidence synthesis summarizes this previous work as applicable and incorporates studies published since these reviews were completed.
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METHODS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONFUTURE RESEARCHREFERENCES |
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In addition, relevant studies were identified from multiple searches of Medline (1966 to January 2005) and the Cochrane Library databases through June 2004. Specific search strategies are available from the authors. Additional articles were obtained by reviewing reference lists of other pertinent studies, reviews, editorials, and Web sites and by consulting experts. This strategy was modified for assessments of screening modalities in key question 3, in which we focused our review on the relevant literature beginning in 1996, the year in which the AAP review concluded.
Inclusion/Exclusion Criteria
Investigators reviewed all abstracts identified in the searches and the previous systematic reviews and determined eligibility by applying inclusion and exclusion criteria specific to key questions.12 Full-text papers of included abstracts were then reviewed for relevance. Eligible studies had English-language abstracts, were applicable to US clinical practice, and provided primary data relevant to our key questions. Non-English literature with English abstracts was reviewed to identify any controlled trials. We excluded so-called teratological DDH, which occurs in children with neuromuscular disorders or other congenital malformations. For all included studies, initial screening had to be conducted in children <6 months of age, and screening studies needed to be prospective, primary care–based, or population-based in design. Studies of risk factors also had to be primary care–based or population-based. Intervention and outcomes studies had to report results of children who were diagnosed before 6 months of age, and interventions had to be used on the children earlier than 1 year of age on average. For intervention studies, we were particularly interested in functional outcomes including gait, pain, physical functioning, activity level, peer relations, family relations, and school and occupational performance. For noninvasive interventions, another potential benefit is a reduced need for surgery later in childhood. Therefore, intervention studies were eligible if they reported 1 of these functional outcomes and/or a subsequent need for surgery. Studies that reported only radiologic reports of anatomic structural relationships and development, which have not been shown to be valid predictors of functional outcomes, were excluded (indicated by a dotted line in Fig 1). For AVN, the predominant harm from interventions, studies needed to report the rate of this complication in the treated-patient population, meet age-based inclusion criteria, have at least 1 year of follow-up, and not experience excessive (>50%) loss to follow-up.
We used a "best-evidence" approach13; that is, for each key question, we included studies with weaker designs only if better-designed studies were not available. Case reports, series with 
5 subjects, editorials, letters, nonsystematic review articles, and commentaries were excluded from the evidence review.
Most studies of DDH are observational, uncontrolled or poorly controlled, and have significant flaws in design. To assess the quality of these studies, we considered the following: study design, clarity of diagnostic standards, comparability of subjects, variation in screening approach and/or intervention protocol, duration of follow-up, loss to follow-up, efforts to control for confounding and minimize bias, masking of outcome assessment, and validity and standardization of outcomes measured.14
Size of Literature Reviewed
Investigators reviewed 1145 abstracts of English-language articles identified by the searches, excluding 679 citations on first review. Review of an additional 544 abstracts of non–English-language articles identified no controlled trials. A total of 466 full-text articles were retrieved and reviewed; 416 were from the electronic searches and 50 were from reference lists or experts' suggestions (a list of expert reviewers is available on request from the authors). The following met inclusion criteria: 13 papers about risk factors; 59 about screening, including 3 controlled trials; 5 about harms of screening; 47 about interventions and harms of interventions, including no controlled trials; and 8 about cost.
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RESULTS |
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TOPABSTRACTMETHODSRESULTSDISCUSSIONFUTURE RESEARCHREFERENCES |
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In theory, early application of noninvasive treatments (eg, a harness) to obtain a concentric and stable reduction of the femoral head in the acetabulum may obviate the need for surgery later on. However, the evidence that screening leads to a reduced rate of surgery is weak and indirect. The 2000 CTFPHC report, which cited several descriptive studies, concluded that "[w]ith serial clinical examination, the operative rate for DDH has decreased by more than 50% to 0.2–0.7% per 1000."3 It should be noted that this reduction was observed at an ecological level: descriptive studies in screened populations were compared, indirectly, to unscreened populations or to historical rates. The studies were not comparative and did not report functional outcomes. In addition, although some studies suggest that surgical rates have declined since the adoption of universal-screening programs, they do not indicate why. The decline might be attributable to increased rates of screening, but other factors such as wider use of a period of observation before recommending surgery also could account for the declining use of these surgical procedures.
The outcome measure used in many studies was the proportion of infants and children with DDH who had surgical intervention. If screening identifies more cases than usual care, it could reduce this proportion even if the same number of cases required surgery as before. For this reason it is difficult to determine if a decrease in the surgical rate over time reflects the efficacy of noninvasive intervention or the inclusion of additional cases in the denominator who are at little or no risk of requiring surgery.
The findings are also inconsistent: some studies observed a decrease in operative rates,15–18 whereas others saw no change19,20 or an increase.21–23 Ascertainment of cases was often flawed, and the studies span several decades, which make it difficult to assess whether the varied results represent artifacts of data quality, secular trends, or differences in local practice styles.24 These studies are also limited because they typically do not follow the screen-negative population with the same vigilance as the screen-positive population and experience significant loss to follow-up in the screen-positive population that can bias the outcomes.
More recent studies also have conflicting results. In 1998, the MRC Working Party on Congenital Dislocation of the Hip reported operative rates in a randomly selected, population-based survey of 20% of all births in the United Kingdom.24 After adjustment for differences in ascertainment that had been overlooked in previous reports, the incidence of a first operative procedure for congenital dislocation of the hip was similar before and after screening was introduced (prescreening rate range: 0.66–0.85 per 1000; postscreening rate: 0.78 per 1000 live births; 95% confidence interval: 0.72–0.84 per 1000). Even in the screening era, 70% of the cases reported by surgeons to the registry had not been detected by screening. In 1999, Australian investigators reported the operative rate in the postscreening era by using an existing perinatal database and an inpatient discharge database to identify infants with congenital dislocation of the hip.25 In contrast to the United Kingdom study cited above, they reported an operative rate of 0.46 per 1000 live births and found that 97.6% of congenital dislocation cases were diagnosed before 3 months of age. The causes behind conflicting findings such as in these 2 studies are unknown.
Key Question 2: Can Infants at High Risk for DDH Be Identified, and Does This Group Warrant a Different Approach to Screening Than Children at Average Risk?
Risk factors are considered an adjunct to, rather than a substitute for, universal screening by physical examination. For example, the AAP recommends using risk factors to identify newborns whose risk for DDH may exceed the comfort level of physicians, prompting additional screening with ultrasound. The rationale for this approach is that, in high-risk newborns, clinical examination alone can miss many cases of DDH that ultrasound may be able to identify. The assumptions underlying this approach are that (1) risk factors can identify a group of newborns at a high risk of DDH and (2) ultrasound is more sensitive than clinical examination for identifying infants at risk of complications from DDH.
In case-control and observational studies, breech positioning at delivery, family history of DDH, and female gender have been shown most consistently to have an association with the diagnosis of DDH. Additional risk factors may include maternal primiparity, high birth weight, oligohydramnios, and congenital anomalies.
Primary care–based and population-based cohort studies26–36 that include 
1 of the major risk factors are summarized in Table 1. Consistently, only a minority (10–27%) of all infants diagnosed with DDH in population-based studies have identified risk factors (with the exception of female gender),30,32,33,35 and among those with risk factors, between 1% and 10% have DDH.30,33,35 This wide range illustrates the impact of the reference standard on the relative importance of risk factors. Those studies with a more strict standard for diagnosing "true" DDH (eg, limited to those patients who receive treatment) demonstrate substantially lower rates of DDH among those with risk factors. For example, in a recent cohort study of 29323 births at 1 hospital, the prevalence of treated DDH was 20 per 1000 in breech females versus 110 per 1000 in this group if the diagnosis of DDH had been based on an abnormal clinical examination. Additional rates of DDH using the more strict reference standard were 12 per 1000 in family history–positive females, 4 per 1000 in breech males, and 5 per 1000 and 0.3 per 1000 in females and males with no risk factors, respectively.28
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Several potential biases should be considered in evaluating risk-factor data. In studies in which the examiner is aware of the patients' risk-factor status, the diagnosis of DDH may be overestimated because of more careful or thorough examinations or more aggressive follow-up and reexamination in infants with known risk factors. Moreover, in retrospective studies researchers apply criteria to improve the reliability of their record review; this approach, although necessary to conduct such a study, reduces the influence of an equivocal or inaccurate history. A predictor such as family history may be less reliable in a prospective, practice-based study than in case-control studies that exclude patients (charts) who have equivocal or incomplete information about it. Finally, investigators' awareness of the subjects' final diagnoses could influence the way that risk-factor information is handled in retrospective studies.
Key Question 3: What Is the Accuracy of Screening Tests for DDH, and Does Screening for DDH Lead to Early Identification of Children With DDH?
The most common methods of screening for DDH involve the physical examination of the hips and lower extremities. Provocative testing includes the Barlow and Ortolani maneuvers, which involve adduction of the flexed hip with gentle posterior force and abduction of the flexed hip with gentle anterior force. The Barlow test attempts to identify a dislocatable hip,10,37 whereas the Ortolani examination attempts to relocate a dislocated hip.38 Because of variations in technique, the Barlow and Ortolani tests have been shown to have a high degree of operator dependence.39 In addition, confusion about the identification of a "click" versus a "clunk" on these tests, and the significance of each of these findings, can lead to disparate conclusions between examiners. Additional findings sometimes reported on clinical examinations for DDH in infants include asymmetry of gluteal and thigh skin folds, discrepant leg lengths, and diminished range of motion (particularly abduction) in an affected hip.4
To measure sensitivity of a test directly in a prospective study, infants who had negative initial screening tests must be followed and examined at older ages to identify false-negative initial test results. Measuring sensitivity is also difficult because results of the Barlow test can be classified into several levels rather than just 2 ("positive" or "negative"). Conversely, measuring specificity and false-positives is difficult because, in most studies, all infants who have a positive screening test are treated with a nonsurgical intervention; the great majority of these infants improve, and it is impossible to say how many of them "responded" and how many of them did not have DDH in the first place.
Assessing the impact of a screening program on the rate of late diagnosis of DDH provides an indirect measure of sensitivity. It is apparent that screening tests performed soon after birth identify some individuals at risk of developing DDH sooner than they would be identified otherwise: most children would otherwise not come to medical attention until they present with crawling or gait delays or disturbances. However, it is difficult to quantify the impact of screening tests on the incidence of late diagnosis with the available literature. Studies of the impact of screening programs on the frequency of late diagnosis have had mixed results.16–18,21,25,40–52 Most of these studies report the experience of a screening program in a defined geographic or hospital service area over many years. The comparisons are ecological, and these studies have the same methodologic problems as those that examined the effect of screening on rates of surgical treatment (discussed above in "Key Question 1"). Some studies in this group reported that, after a screening program was adopted, late diagnosis was very rare, whereas others report that screening had no effect on the rate of late diagnosis and that unexplained fluctuations in late-diagnosis rates were observed from year to year within the postscreening era (Fig 2). *
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To apply this standard, a cohort study must follow infants for a long enough period without applying any treatment to determine if the abnormal findings persist and lead to clinical problems. In 1 good-quality prospective cohort study that followed untreated infants for 2 to 6 weeks, 
9 of 10 infants with initially abnormal ultrasound examinations revert to normal.2 Similarly, by 2 to 4 weeks of age, >60% of infants identified at birth by abnormal clinical examination (Barlow or Ortolani tests) have reverted to normal when judged by repeat clinical examination or by ultrasound examination.10,37,54 Longer prospective studies28,53–59 and a systematic review of observational studies of ultrasound screening60 demonstrate that in untreated hips, mild dysplasia without frank instability usually (consistently >90%) resolves spontaneously between 6 weeks and 6 months.
The clinical examination approach to diagnosis for DDH shifts over time. The Barlow and Ortolani tests become less sensitive as infants age because of factors including increased strength, bulk, and size.3,4 In their place, assessment of hip abduction becomes the preferred examination, because infants with dislocated hips have increased contractures of the hip adductors.4 In general, the specificity of examination improves as infants age, because the hips of the newborn infant are more likely to exhibit transient and clinically insignificant laxity than they will subsequently.37 Two recent studies provide indirect insight into the changing signs of DDH as the infant ages. In a study of 1071 referred infants at 1 center, only 2 of 34 (6%) hips in patients with positive Barlow or Ortolani tests, confirmed as dislocatable by ultrasound, had any limitation in abduction at 1 to 2 weeks of age, which suggests that limited abduction has poor sensitivity in newborns.61 Specificity of limited hip abduction in newborns was also poor: among 203 1- to 2-week-old infants with limited abduction, <20% had abnormalities on ultrasound. These findings contrasted with older children: of the 8 patients who presented after 6 months of age with dislocatable hips, hip abduction was limited in 7 patients (87.5%). In the second study, a prospective observational study limited to infants who were >3 months of age (N = 683), unilateral limited hip abduction had a sensitivity of 69% (156 of 226) and specificity of 54% (247 of 457).62 The reference standard in this study was any ultrasound abnormality; among the subset of subluxable and dislocatable hips, sensitivity of limited hip abduction was >82%. Of the 136 patients with limited abduction and normal ultrasound findings at the initial examination, none showed examination or gait abnormalities at 5 years of age. Although not conclusive, these studies suggest that hip abduction is a relatively insensitive and nonspecific marker of DDH in early infancy but becomes more accurate after 3 to 6 months of age and with more severely affected hips.
Additional physical examination findings sometimes linked to DDH include asymmetrical gluteal and thigh skinfolds, and leg-length discrepancy. No studies from the past 40 years were identified that assessed the value of these findings in diagnosing DDH. In 1962, Barlow10 pointed out the lack of utility of asymmetric skin folds because of their poor sensitivity and specificity, and in 1961 Palmén63 studied 500 random newborns and found that 27% had no thigh skinfolds, 40% were symmetrical, and 33% asymmetrical; 4 of these 500 infants had an abnormal provocative test of stability, of which 2 had symmetrical skinfolds. Based on this scarce and unsupportive literature, it is difficult to conclude that these additional findings on examination are useful.
The degree of training and experience with the clinical examination of the hip in infants has been shown to be a strong predictor of the test characteristics. Pediatricians have been shown to have a case identification rate of 8 per 1000, whereas orthopedists identify 11 per 1000.1 Two studies show that having duplicate blinded examinations by a pediatrician and an orthopedist improves the sensitivity, specificity, and predictive value of clinical examination screening.64,65 Additional studies show that well-trained nonphysicians, including physiotherapists and neonatal nurse practitioners, perform at least as well as physician examiners and better than physician trainees.66–68 In 1 single-site longitudinal study, as the number of pediatricians involved in screening infants increased (holding steady the overall number of newborns screened), a greater number of cases of DDH were missed despite an increased rate of suspected cases identified.69 In other words, both sensitivity and specificity suffered when there was less centralized oversight of the newborn screening program and when fewer infants were screened, on average, by each pediatrician.
Studies comparing pediatricians with orthopedic surgeons often use a study design in which the orthopedist reviews a subset of hips found to be positive or questionable by a previous examiner. This second examination may happen days after the initial examination. Also, the surgeons often have at their disposal the results of ultrasonography, and their clinical examination is not blinded from the ultrasound examination. It is not surprising that such studies show a higher sensitivity and specificity of clinical examination in the hands of the specialist.
Use of Imaging to Screen for DDH
In addition to the clinical examination, ultrasonography and radiography are also used to screen for DDH. The use of ultrasonography and/or radiography in screening has been controversial, particularly because of reports of high false-positive rates that lead to unnecessary and potentially harmful follow-up and intervention.70 Despite the controversy, ultrasound has been widely incorporated into DDH screening programs in many developed countries.71,72 Ultrasound methods include both static and dynamic assessments of the hip. As is the case with clinical examination, all imaging methods used to screen for DDH are variably subjective and operator-dependent.
In the first 4 to 6 months of life, ultrasound has been deemed to be a more appropriate test than radiographs for anatomic hip abnormalities as well as instability of the hip because of incomplete ossification of the femoral head in early infancy. No study has addressed the comparative value of ultrasound to radiograph. However, there is strong endorsement of the superiority of ultrasound in the early months of life in the literature, ranging from historical studies reporting on timing of ossification and analyzing the technical challenges of hip radiography in the young infant63,73 to contemporary systematic reviews.1,4
However, ultrasound screening is not without its shortcomings. In addition to the high rate of identification of nonpathological hip findings summarized above, the most widely used ultrasound-grading system, the Graf classification,74 has come under scrutiny. The Graf score is used in the vast majority of the screening literature to differentiate normal hips from immature hips, minor dysplasia, or major dysplasia and stable from unstable, subluxable, and dislocatable/dislocated. Many studies base treatment decisions on these classifications. A study examining the reliability of Graf classification found that among normal hips, intraobserver and interobserver reliability is quite high, with a 98% chance of having the same assessment on future readings. However, among ultrasounds that are read as abnormal by at least 1 person, intraobserver reliability was moderate (
= 0.41) and interobserver reliability was fair ( = 0.28). In addition, knowledge of the patients' history and physical examination versus blinded review of the ultrasound lowered the intraobserver value from 0.41 to 0.37.75
Another study found moderate agreement between observers with subjective ultrasound reading ( = 0.5), but this decreased to 0.3 when objective measurements of anatomic relationships were conducted. Grading of dynamic hip stability showed only moderate agreement between examiners ( = 0.42), even when dislocated and dislocatable hips were grouped together. This study estimated that the decision to treat would have been affected in 2.4% of cases because of discordance between reviewers.76 Considerable effort was given to standardizing ultrasound assessment in this study, including a training session and 100 repetitions of conducting measurements before the start of the study. Still another study found ultrasound reliability to be similarly suspect, with values ranging from 0.52 to 0.68 and 0.09 to 0.30 for intraobserver and interobserver agreement, respectively, across 7 anatomic measures used in grading DDH.77 These findings raise concerns about the operator dependence of this evaluation for DDH and may shed light on the variability of ultrasound screen-positive rates found in the literature.
Although there are no trials or comparative studies of a screened to an unscreened population, 2 randomized, controlled trials (RCTs)78,79 and 1 non-RCT53 provide some insight into the accuracy of clinical and ultrasound examinations. These trials reported data about test performance of one screening strategy versus another (Table 2). The first RCT compared universal ultrasound screening to selective screening at a population level.78 In the trial, patients at the University of Trondheim, Norway, were randomly assigned to 1 of 2 groups over a 5-year period. In the first group, each of the 7840 patients received clinical examination and ultrasound. In the other group, 7689 received clinical examination alone or, if they had risk factors (abnormal examination, breech, family history, foot deformities), ultrasound and clinical examination. In the selective-ultrasound group, 5 infants presented between 5 and 6 months with previously undiagnosed DDH, whereas in the universal-screening group there was only 1 case of late diagnosis. In all these late-presenting cases, treatment with an abduction brace was implemented and the hips were reported to be normal on follow-up, with none requiring subsequent surgery. Overall treatment rates were equivalent in the 2 groups.
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A non-RCT conducted in 1994 compared 3613 infants in a universal ultrasound screening program to 4388 in a selective screening program and 3924 who received only clinical examination.53 In the selective-ultrasound cohort, a positive clinical examination was considered to be a risk factor prompting ultrasound. The authors concluded that the universal-ultrasound cohort had a significantly higher treatment rate overall but no higher rate among high-risk infants. There was a nonsignificant trend toward a lower rate of cases diagnosed after 1 month of age in the universal-screening patients. Among those who were not treated, many more children with mildly dysplastic hips were identified by ultrasound, resulting in more follow-up visits and ultrasounds for a greater number of patients without persistent DDH in the universal-screening approach.
Table 3 includes studies of population-based or primary care clinic–based cohorts screened by clinical examination as well as ultrasound screening that were published since the 1996 end point of the AAP review.28,70,72,80–83 Despite variation in the reference standards used in these studies, several important findings emerge. First, a high proportion of hips diagnosed with minor findings of dysplasia undergo spontaneous resolution. It is important to note that minor dysplasia is not identified by clinical examination but only by ultrasound. Because of the identification of anatomic variations that are marginal and self-limited, the potential exists for overtreatment on the basis of ultrasound. On the other hand, in 4 of the 7 studies listed in Table 3, 38% to 87% of abnormal findings on clinical examination were not DDH, leading to a similar risk of unnecessary therapy on the basis of clinical examination.72,80,81,83 Very few of these studies followed patients longitudinally, particularly those patients who did not screen positive by examination or ultrasound.
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Radiation Exposure
A single-center study of radiation exposure and increased theoretical risk of fatal cancers or reproductive defects reported the radiographic history of 173 patients who completed a course of treatment for DDH between 1980 and 1993. Based on cumulative radiation exposure, males and females with DDH who had surgery (a marker for significantly elevated levels of exposure) were calculated to have a 0.09% and 0.12% increased risk of fatal leukemia and a 0.23% and 0.5% increased risk of reproductive defects, respectively.88 There was no increased risk of fatal breast cancer in either gender. Attributable risks in nonsurgical DDH patients were approximately one half to one third of those reported for surgical patients. Given changes in technology and management in the time interval since these data were gathered, it is not clear whether the level of radiation exposure documented in this study is still applicable.
Psychosocial
We found no published studies that sought to identify or quantify the psychosocial stresses of the diagnosis of DDH. No evidence was identified regarding adverse effects suffered by the child or family from false-positive identification. Presumably, there is a cost borne by the family and/or society for the follow-up evaluation that ensues, but this has not been quantified. Other adverse effects may be experienced but are not represented in the literature.
Key Question 5: Does Early Diagnosis of DDH Lead to Early Intervention, and Does Early Intervention Reduce the Need for Surgery or Improve Functional Outcomes?
Ten different nonsurgical abduction devices are represented in the published literature, and 23 different surgical procedures are used to treat DDH (see ref 12 for a complete listing). The indications and timing of treatment and the protocol for the selected treatment modality vary from study to study, further obfuscating attempts at clarifying effectiveness. These circumstances are characteristic of interventions that have not been evaluated, or proven effective, in controlled trials.89 Because no experimental or prospective cohort studies compare intervention with no intervention, the net benefits and harms of interventions for DDH are unclear, not only for infants diagnosed early but for all children.90
Poor functional outcomes from hip pathology may not manifest for decades. Thus, functional outcomes have not commonly been measured. Even when measured, the effect of interventions on functional outcomes is unknown because of (1) the absence of an appropriate comparison cohort and (2) the substantial risk of bias stemming from short duration of follow-up, significant loss to follow-up, and/or nonstandardized, unblinded assessment methods without adequate rigor to ensure their validity (eg, the surgeon's subjective report of the patient's function and pain). Because of these methodologic problems, the evidence assessing whether interventions improve functional outcomes is poor, and study details have been excluded. Details about intervention studies91–103 that included any assessment of functional outcomes are included in ref 12.
Given the absence of direct evidence from controlled trials, the case for the effectiveness of early intervention rests on less secure grounds, as follows.
Biological Plausibility
It is biologically plausible that placing the femoral head into the acetabulum would facilitate normal development. Although they are retrospective, careful analyses of late-presentation cases provide convincing fair-quality evidence that late-presentation dislocations are often accompanied by premature arthritis, indicating that, at least in some cases, untreated DDH can have serious consequences.104–106
Based on this information, it is reasonable to hypothesize that relocating hips long before clinical symptoms occur may prevent morbidity and improve function. Unfortunately, an understanding of the effectiveness of interventions for DDH is confounded by the fact that many unstable and dysplastic hips undergo spontaneous resolution.10 Thus, without a study design that includes an untreated cohort, the benefit attributable to an intervention remains in doubt.
Although the number of studies is small, it is clear that untreated DDH has an unpredictable course with outcomes that are not universally poor. Among 628 Navajo infants born in a single region from 1955 to 1961, 548 were examined and radiographed during the first 4 years of life (20% in the first 6 months of life but none as neonates).107,108 Eighteen (3.3% of those examined) were found to have hip dysplasia (including subluxation but not including frank dislocation) by accepted radiographic criteria. None were treated. Of these 18 children, 17 were followed for 7 to 19 years, and all had stable hips with normal radiographs.108 When 10 of these patients were followed up at 33 to 37 years of age, none were aware that they had ever had a problem with their hips. Although 6 did report a history of mild hip pain, it did not correlate with the degree of abnormality on radiograph. In addition, all patients had normal function, engaged in light to heavy labor, and were able to contribute to society without limitations.107 Another study followed 51 consecutive patients with a normal clinical examination but evidence of dysplasia on radiograph. Altogether, 6 patients were lost over 5 years of follow-up. Forty-four affected hips (number of patients not reported) were normal after 5 years, 4 had undergone successful abduction therapy, and 20 were borderline on repeat imaging. No progression to subluxation or dislocation was noted in any of the hips.109
Reduced Need for Surgery
Early noninvasive intervention may reduce the need for surgery. This is a key observation that underlies previous recommendations favoring screening for DDH. As discussed earlier, however (see "Key Question 1"), the evidence supporting this assertion is conflicting. Moreover, the need for surgery is a moving target: when they are observed, reductions in surgical rates might have occurred because of changing indications or because of wider use of a period of observation before surgery rather than because of screening itself.
Earlier intervention may reduce the risk of complications. Several observational studies examined the impact of age at the time of intervention.25,81,95,110–113 In 1 small study that included children initiating therapy for DDH from birth through 4 months of age, duration of treatment increased in a dose-response fashion as the age at initiation of treatment increased, holding the severity of DDH steady.81 In a separate series of patients who underwent surgery for DDH (70% of whom had failed therapy with a Pavlik harness), those who were 6 to 9 months of age (18 patients) required no additional corrective surgeries, whereas 29% of the patients 10 to 11 months of age, 13% of patients 12 to 14 months of age, 26% of patients 15 to 18 months of age, and 30% of patients 19 to 24 months of age required additional surgical interventions.110 Another study, based on unadjusted analysis, reported that the average age of DDH cases complicated by AVN was >15 months, whereas uncomplicated cases averaged 11 months of age.111 Two additional studies found that intervention initiated after 6 months of age was associated with significantly higher rates of AVN.95,112 In a study that focused on late diagnosis of DDH, closed reduction failed in a similar proportion of cases in children aged 0 to 3 months as those 3 to 6 months but failed significantly more frequently after 6 months of age (no upper age limit was identified, potentially biasing these conclusions).113 Finally, a study of 55 children who underwent operative procedures for DDH between 1988 and 1998 found that procedures were less invasive in children who were <6 months. All children >12 months who underwent a procedure for DDH required an osteotomy, the most invasive procedure.25 Although inconclusive, these studies provide fair evidence that initiation of interventions after 6 months of age may carry added risks of harms.
In contrast, 3 retrospective observational studies did not support an effect of age on success of treatment.94,114,115 The first study reviewed the rate of success of closed reduction and showed no difference among patients who were treated with this intervention at <6, 7 to 12, or 13 to 18 months.114 A study limited to 168 children with hip subluxation or dislocation and a minimum follow-up of 5 years compared children in whom a Pavlik harness was successful with those who required closed reduction and those who eventually required open reduction and found that age was not a predictive factor of the success of nonsurgical therapy.115 Finally, a study of 75 children with DDH who were treated within the first 14 weeks of life with the Pavlik method showed that age at initiation (ranging from 5 to 13 weeks) had no influence on duration of treatment, success rate, or AVN outcome at 1 year of age.94
It is possible that some relevant literature was excluded because we limited the review to studies in children whose intervention began within their first year of life. Within this period, conclusive evidence of a clear benefit of earlier intervention is elusive. The design of the studies cannot exclude other plausible explanations for the association between age at intervention and rates of surgery. One of these explanations is that passive abduction therapy may be less effective because children become stronger and more mobile beyond 6 months of age. Another explanation is that the early-treated group included a high proportion of children with mild disease that would have recovered without intervention, whereas the older children had persistent disease that would not have responded even if they had been treated earlier.
Improved Radiographic Appearance
Use of noninvasive treatments is often associated with improvements in radiographic or sonographic appearance. Although radiographic reduction may be an essential step in the causal pathway from congenital dislocation to prevention of serious complications, radiographic outcomes have not been shown to be valid or reliable surrogates for functional outcomes. The most commonly used and widely accepted radiographic assessment is a 6-level scale that was described initially by Severin116 in 1941, which was based on radiologic appearance of hips in 16- to 24-year-olds. One study examined the validity of the Severin classification with functional outcomes in patients, at an average of 31 years postintervention, who had received surgery for dislocation of the hip.117 The study found that radiographic findings (normal position of femoral neck and head, degree of arthritis, and shape of the femoral head) were poorly correlated with the outcomes of range of motion and pain.
Two studies assessed the reliability of the Severin classification.118,119 Ali et al118 found intraobserver reliability among pediatric orthopedists in the United Kingdom with 7 years experience to be moderate to substantial ( ranging from .58 to .77) and interobserver reliability to be poor to slight in the intermediate Severin classes of II and III ( = 0.19–0.20) and moderate ( = 0.44–0.54) in the disparate Severin classifications of I (normal) and V (marginal dislocation). Ward et al119 found even less reassuring results. Blinded assessments by pediatric orthopedists in this study were assessed by dichotomous observer groups as well as multirater groups and found scores in the range of 0.0 to 0.29 across the range of Severin classes and no higher than 0.56 for overall agreement across any 2 surgeons. Even more concerning was that the operating surgeon’s unblinded scores showed uniform poor reliability ( = 0.02–0.21) when compared with each of the blinded observer's scores. Despite the absence of studies supporting the reliability of radiographic measures, intervention studies rarely included blinded or repeated assessments of radiographic outcomes. Because of highly suspect validity and reliability, studies that reported only radiographic outcomes were excluded from additional review.
Closer Follow-up
Diagnosis leads to attentive follow-up of infants with DDH, which facilitates quick detection and intervention. Thus, children who undergo early noninvasive therapy may benefit from closer follow-up and the physician's ability to react to a deteriorating condition more rapidly. Although limited, available evidence supports the notion that a high proportion of families follow through with the initial referral.29 However, we could not determine how many families adhere to ongoing follow-up.
Underlying the effectiveness of early diagnosis and early intervention is the degree to which families adhere to medical recommendations. One study assessed failure to follow-up with a specialty appointment after identification of newborns with an abnormality on examination or the presence of a risk factor for DDH.29 This specialty clinic, a part of Britain's national health system, followed a systematic approach to contacting nonattenders, including up to 2 letters to the family that explained the reason for referral and safety of ultrasound and offered an appointment the following week, followed by contact with the general practitioner to persuade the family. With this approach, nearly 95% of patients followed up. The groups with the highest follow-up rate (>98%) included those with an unstable hip at the newborn examination and those with a positive family history. It may be unlikely that the average orthopedic clinic in the United States will achieve an equivalent rate of follow-up, given access barriers and less robust efforts at contacting those who initially miss scheduled appointments.
A second study, based in the United States, examined the rates of parental adherence to recommended abduction therapy with the Pavlik harness.120 Of 32 patients treated by the same physician, only 2 families reported strict adherence to the physician's orders in a posttreatment questionnaire. Nonadherence was defined as failure to do 1 of the following: (1) full-time use during the initial period of reduction when the hip was not stable; (2) altering or deliberating misplacing the harness; or (3) discontinuing use of the harness for prolonged periods of time without permission. Nearly two thirds of the mothers who participated in the study had a college education or advanced degree; their age range was 17 to 40 years (average: 29 years). Harness therapy failed for 3 of the 32 patients, and by the authors' report these cases were not more egregious in their degree of noncompliance than successfully treated children. The single exception was a mother who routinely removed or adjusted the harness because the child could not fit into a car seat because of the limited adduction.120
Key Question 6: What Are the Adverse Effects of Early Diagnosis and/or Intervention?
Good-quality literature examining harms of intervention for DDH would include a comparison of 2 (ideally randomized) cohorts, each exposed to a standardized intervention and followed over sufficient time (with limited loss to follow-up) to ensure complete ascertainment of the potential harms with an assessment of the effect of the measured harms on patient outcomes. Unfortunately, these studies have not yet been conducted. In their absence, we reviewed the fair-quality literature on adverse effects of both nonsurgical and surgical interventions.
The most well-described adverse effect from interventions aimed at treating DDH is AVN of the femoral head. This is the most common adverse effect for both abduction therapy and surgical interventions. AVN severity ranges from a persistent but asymptomatic radiographic finding to a severe condition that causes growth arrest and can lead to eventual destruction of the joint. The rates described in the literature for AVN vary greatly for abduction therapy as well as surgical interventions (Fig 3). 
The reasons for these disparate findings are not straightforward and most likely relate to a complex and confounded set of variables including but not limited to the wide spectrum of the disorder, heterogeneous populations studied (age at intervention, specific type of DDH, previous interventions received), the variety of interventions and the poorly standardized approach to interventions (particularly the preintervention and postintervention phase of management), variable training and talent among the treating physicians, different lengths of follow-up across studies, and disparate approaches to follow-up in different health care systems. As calculated in the AAP review, meta-analytic rates of AVN range from 13.5 to 109 per 1000 infants who undergo treatment (nonsurgical versus surgical rates were not specified).1
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A fair-quality study that assessed the long-term psychological impact on children of successfully treated DDH showed that parents and teachers found that children with DDH were more "disordered" than peers with no hospitalizations, 1 hospitalization, and multiple hospitalizations on the domains of "health," "habits," and "behavior."130 This 1983 study implies (but does not quantify) extended hospitalizations for children with DDH as a rule and thus may not be generalizable to the impact of treatment today.
Key Question 7: What Cost-Effectiveness Issues Apply to Screening for DDH?
Several economic analyses of screening for DDH have been published.79,90,131–136 Most of them concern the marginal benefit of ultrasound screening in relation to screening with clinical examination.79,90,132,133,136 None of the available studies used quality-adjusted life-years, and none used models based on US data or the US health care system. These analyses demonstrate that the economic impact of ultrasound screening is complex, reflecting that ultrasound may have mixed effects on the diagnosis of DDH: it may identify false-positive clinical examinations, reducing or shortening the duration of unnecessary treatments, but it also identifies many abnormalities in infants who have normal physical examinations, potentially leading to more early treatment and greater follow-up costs. The mixed results of the economic studies largely reflect mixed results of the clinical studies on which they are based. The best-quality economic study, derived from an RCT (in the United Kingdom) of clinical examination screening versus clinical examination plus ultrasound maintained detailed records of utilization of medical services and related costs.79 Although the costs of ultrasound were predictably higher in the cohort receiving ultrasound, hospitalization costs in this group were lower. In sum, the overall direct medical costs for the 2 approaches were not statistically significantly different.79 This study did not report indirect costs such as missed work by the family, nor did it include the costs of long-term follow-up or complications.
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Despite a paucity of evidence supporting its value in improving outcomes, universal screening for DDH is a well-established approach to the disorder. However, the approach to screening varies significantly. In addition to physical examination with the provocative tests of Barlow and Ortolani and evaluation of range of motion that emphasizes abduction of the hip, static and dynamic ultrasound are used to identify anatomic abnormalities and stability of the hip, respectively. Some have recommended risk stratification to inform selective use of ultrasound, with females in breech positioning at delivery found to have the highest rate of clinical hip instability (84 per 1000). Yet, when a more conservative reference standard for DDH is used, the value of ultrasound as an aid to diagnosis in those with risk factors is less conclusive. Some health systems have elected to use universal ultrasound screening in an effort to reduce the incidence of late diagnosis of DDH. The use of ultrasound to further evaluate hips found to be unstable on clinical examination may reduce the rate of unnecessary treatment but also may lead to higher rates of follow-up for hips that ultimately will spontaneously normalize. The reliability of DDH classification by ultrasound is questionable. Theoretical harms from screening include examiner-induced hip pathology with vigorous provocative testing, elevated risk of certain cancers from increased radiation exposure from follow-up radiographic tests, and parental psychosocial stress from the diagnosis and therapy. None of these have been quantified in patients/families in clinical studies published to date beyond anecdotes.
It is known that a significant number of hips with positive screening tests, by both physical examination and ultrasound, will normalize over time without intervention. This is particularly true of ultrasound in hips that are stable on clinical examination of the neonate: >90% of abnormal ultrasound findings in this situation have been shown to normalize spontaneously. Although limited fair-quality evidence exists to support the value of initiating treatment within the first 6 months of life, there is little to suggest that immediate treatment in the neonatal period is associated with improved outcomes or a reduced need for subsequent surgery. However, no study has examined the effect of timing of treatment initiation and controlling for the degree of hip instability.
First-line intervention includes abduction bracing of the hips, which attempts to induce passive alignment of the hip. Several devices are used for abduction, with a wide range of institutional protocols. Failure of abduction therapy, or the occasional case of dislocated and clinically irreducible hips at presentation, leads to surgical intervention. The indications and protocols for surgery vary widely, as do the preoperative and postoperative approaches to management.
Estimates of the effectiveness of therapy are confounded by spontaneous resolution of hip dysplasia, which has only rarely been assessed and never in a prospective or comparative fashion. The impact of interventions on functional outcomes is rarely addressed in the literature and when addressed is of poor quality because of a lack of standardization within studies and the absence of validated functional outcome measures across studies.
The most significant and common adverse effect of both nonsurgical and surgical intervention for hip dysplasia is AVN of the femoral head, which can lead to growth arrest and eventual destruction of the hip joint. The balance of benefits and harms of intervention is obscured by significant gaps in the available evidence. Similarly, assessment of the cost-effectiveness of screening for DDH requires more conclusive information about effectiveness.
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Address correspondence to Scott A. Shipman, MD, MPH, Department of Pediatrics, Oregon Health and Science University, 707 SW Gaines Rd, CDRC-P, Portland, OR 97239. E-mail: shipmans{at}ohsu.edu
The authors have indicated they have no financial relationships relevant to this article to disclose.
* Refs 16–18, 20–22, 29, 33, 40, 45, 50, and 53. 
Refs 91–95, 97, 99, 101–103, 112, and 121–129.
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indicates clinical exam only; •, clinical exam and universal ultrasound; 
, clinical exam and selective ultrasound.