Developmental Dysplasia of the Hip

POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose. Developmental dysplasia of the hip (DDH) encompasses a broad spectrum of abnormal hip development during infancy and early development. The definition encompasses a wide range of severity, from mild acetabular dysplasia without hip dislocation to frank hip dislocation. The etiology of DDH is multifactorial. Risk factors for DDH are breech positioning in utero, female sex, being firstborn, and positive family history.1 – 4 Other conditions related to prenatal positioning, including metatarsus adductus and torticollis, are associated with DDH. Prolonged abnormal postnatal positioning via swaddling also has been suggested as a risk factor in DDH because certain ethnic populations that practice tight swaddling have a higher rate of DDH.5, 6 The treatment algorithm in patients with DDH depends on each patient’s age and severity of the condition. The goal in the treatment of DDH is to achieve and maintain a concentric reduction of the femoral head in the acetabulum to allow for continued normal development of the hip. The natural history of residual DDH or dislocation into adulthood has been associated with pain and early development of osteoarthritis. Residual sequelae of DDH are 1 of the leading causes of early hip osteoarthritis in adulthood.7 Hence, the goal is to improve hip development in infancy and early childhood to prevent subsequent functional impairment.

Developmental dysplasia of the hip (DDH) encompasses a broad spectrum of abnormal hip development during infancy and early development.The definition encompasses a wide range of severity, from mild acetabular dysplasia without hip dislocation to frank hip dislocation.The etiology of DDH is multifactorial.Risk factors for DDH are breech positioning in utero, female sex, being firstborn, and positive family history. 1 -4 Other conditions related to prenatal positioning, including metatarsus adductus and torticollis, are associated with DDH.Prolonged abnormal postnatal positioning via swaddling also has been suggested as a risk factor in DDH because certain ethnic populations that practice tight swaddling have a higher rate of DDH. 5,6 he treatment algorithm in patients with DDH depends on each patient's age and severity of the condition.The goal in the treatment of DDH is to achieve and maintain a concentric reduction of the femoral head in the acetabulum to allow for continued normal development of the hip.The natural history of residual DDH or dislocation into adulthood has been associated with pain and early development of osteoarthritis.Residual sequelae of DDH are 1 of the leading causes of early hip osteoarthritis in adulthood. 7Hence, the goal is to improve hip development in infancy and early childhood to prevent subsequent functional impairment.
A variety of methods are available achieve the overarching goal of obtaining a concentric hip reduction.The treatment methods and goals have not drastically changed in the past 20 years, although recent developments within the past 5 to 10 years have been focused on optimal surveillance methods, imaging modalities to guide treatment, outcomes assessment of treatment methods, and refining indications for treatment.It is important for both the clinicians and families to understand that the treatment of a dysplastic hip can be challenging and met with complications.
Although variations in treatment exist based on individual patient characteristics, the following algorithm is generally considered (Table 1).Infants up to 6 months of age who are confirmed to have hip instability or dislocation are generally treated with a brace initially, such as a Pavlik harness or abduction orthosis.Patients aged 6 to 18 months with dislocation can be treated with closed reduction and the application of a hip spica cast.Generally, patients >12 to 18 months of age or those who fail to achieve a concentric hip reduction with closed methods are considered candidates for open surgical hip reduction.There are outliers to this general algorithm Developmental Dysplasia of the Hip Scott Yang, MD, a Natalie Zusman, MD, a Elizabeth Lieberman, MD, a Rachel Y. Goldstein, MD b Pediatricians are often the first to identify developmental dysplasia of the hip (DDH) and direct subsequent appropriate treatment.The general treatment principle of DDH is to obtain and maintain a concentric reduction of the femoral head in the acetabulum.Achieving this goal can range from less-invasive bracing treatments to more-invasive surgical treatment depending on the age and complexity of the dysplasia.In this review, we summarize the current trends and treatment principles in the diagnosis and treatment of DDH.
because children <6 months old may occasionally require closed or open hip reduction if bracing treatment fails.Osteotomies, such as femoral shortening osteotomy and pelvic osteotomy, are considered for hip dislocation in older patients to decrease tension on the hip reduction and those with a residual shallow dysplastic acetabulum, respectively.Adolescents and young adults with residual symptomatic acetabular dysplasia are treated with periacetabular osteotomy (PAO) to preserve the native hip joint and avoid hip arthroplasty.Recent developments in each of these treatment methods will be discussed in this article.

HIP EXAMINATION
Early identification of infants with dysplastic hips can be performed on a routine basis from the newborn physical examination and continue until the child reaches walking age. 8 newborn infant's hips should be evaluated by using the Barlow and Ortolani physical examination maneuvers.The Barlow maneuver is performed by adducting the hip to the midline and gently applying posterior force.A positive Barlow result is when the femoral head subluxes, and a clunk is felt.A Barlow-positive hip indicates that the femoral head is resting in the acetabulum but has pathologic instability.With the thighs adducted and posteriorly depressed, the Ortolani maneuver is performed by abducting the hips while applying anterior-directed pressure at the greater trochanters.An Ortolani maneuver is considered to have a positive result if the femoral head relocates with a distinct clunk.An Ortolani-positive hip is more severe than a Barlow-positive hip because it indicates that the femoral head is dislocated at rest.The presence of a subtler hip click during examination is a nonspecific finding and often does not indicate true hip pathology. 9,10 e 2 major limitations of these maneuvers are their dependence on the skill of the examining provider and the fact that these tests are more sensitive in younger infants, whose soft tissues around the hip joint have yet to contract.Furthermore, a severely dislocated hip that is not reducible may not have a Barlow or Ortolani positive result.The sensitivity of Barlow and Ortolani examination maneuvers alone in identifying DDH is at best 54% 11 ; thus, adjunct imaging modalities for identification can be helpful.
For the older infant or child, Barlow and Ortolani examination is of limited utility due to the development of contractures.These patients are observed for leg length discrepancy, thigh-fold asymmetry, and limited hip abduction.Leg length discrepancy should be assessed for with the infant in the supine position with the pelvis flat on a level surface and the hips and knees flexed to 90°.A discrepancy is indicated by unequal knee heights, which is termed the Galeazzi sign (Fig 1).Asymmetric thigh folds and clinical examination of limb length discrepancy are prone to error and inaccuracy.The most sensitive examination for unilateral hip dislocation in a child >3 months old is an assessment for asymmetric diminished hip abduction (Fig 2). 12,13 e walking child may also present with a Trendelenburg gait (trunk tilt toward the affected hip when weight is applied) if there is a unilateral dislocation or a waddling gait (trunk tilt toward the weight-bearing side, alternating throughout the gait cycle) if there is bilateral dislocation.For infants who are Ortolanipositive or older children with any of the above examination findings, further diagnostic evaluation can be obtained, as described below.

DIAGNOSTICS: IMAGING STUDIES
Ultrasonography is the recommended imaging modality in infants <4

EARLY IDENTIFICATION AND SURVEILLANCE
The optimal method to screen for DDH is controversial.Several methods include physical examination alone, physical examination with a selective use of ultrasonography, and universal screening with ultrasonography.
There has been no comparative study of outcomes in patients who have not been screened versus those who underwent a screening program for DDH.Ultrasonography has been demonstrated to be used to identify potentially pathologic hips more than clinical examination alone.Dezateux and Rosendahl 15 reported that the identification of dysplastic hips in general populations increased from 1.6 to 28.5 per 1000 infants, with clinical examination increasing from 34.0 to 60.3 per 1000 infants with the use of screening ultrasonography.
Studies in which researchers compare clinical examination and selective ultrasonography to universal ultrasonography revealed no significant difference in decreasing the late presentation of DDH. 16,17  2013 Cochrane Review on the topic echoed this conclusion with the findings that targeted screening is not associated with significant

FIGURE 2
The right hip has limited abduction compared with the left, suggesting possible hip dislocation.

FIGURE 3
Coronal ultrasound images of a 2-month-old dysplastic hip.Key ultrasound measurements include the α (which is formed by the bony ilium and the bony roof of the acetabulum), the β angle (which is formed by the bony ilium and the labral fibrocartilage), and the percentage of the femoral head covered by the bony roof of the acetabulum.The α angle has more clinical significance than the β angle.In this image, (1) the femoral head does not seat deeply in the socket, with <50% of the femoral head being covered by the acetabulum, and (2) the acetabulum is shallow (normal α >60°).
increases in late diagnoses when compared with universal screening and is associated with a reduction in potential overtreatment. 18The American Academy of Orthopaedic Surgeons also provided a moderatestrength recommendation supporting not performing universal screening ultrasound in newborns in its recent clinical practice guideline. 19ecause many milder forms of DDH have a benign natural history, this increased identification of DDH can potentially lead to overtreatment.The true natural history of mild acetabular dysplasia on a welllocated hip on ultrasonography is unclear because many can improve without intervention, as evidenced on serial ultrasonography. 20Olsen et al 21   is more problematic and has had Pavlik harness failure in 21% to 37% of patients. 23 -25Patient-related risk factors for failure of harness treatment included increased age at initiation of treatment (>7 weeks old), 25, 26 multigravida birth, 27 the presence of a foot deformity, 27 and male sex. 24The initial ultrasonographic severity of dysplasia in the Ortolani-positive hip is prognostic for the failure of Pavlik harness treatment, with more severely dislocated hips in which the labrum is interposed between the femoral head and acetabulum being associated with failure. 23r those patients with an Ortolani-  Pavlik harness on an infant, gently holding the hips in a flexed and abducted position.

FIGURE 6
Ilfeld abduction orthosis on a patient.This orthosis allows for the hips to be held more rigidly in abduction than a Pavlik harness.Hence, the timing of performing the osteotomy is controversial although typically performed at ∼3 to 5 years of age for residual acetabular dysplasia.The most commonly used pelvic osteotomies are termed the Salter, Pemberton, and Dega.All these osteotomies use a single cut above the acetabulum, with their differences being in the completion or direction of the cut (Fig 8).On the basis of recently available literature, the radiographic and clinical outcomes for which researchers compare the various types of osteotomy appear to be similar in the treatment of residual acetabular dysplasia. 47 -50Although there is no clear upper-age limit guideline to the above osteotomies, it is more difficult to achieve adequate acetabular coverage of the dysplastic hip with a single osteotomy with increasing age.For older children with an open triradiate cartilage growth center, typically >6 years of age, a triple innominate osteotomy can be considered.In the triple innominate osteotomy, all 3 osseous regions surrounding the acetabulum are cut to allow for a free reorientation of the acetabular and the achievement of increased correction of acetabular dysplasia (Figs 9 and 10).
At this juncture, it appears that pelvic osteotomies are useful in improving radiographic coverage of the femoral head and preventing reoperation for residual instability after open reduction.The technique of osteotomy appears to be at the discretion of the surgeon because 1

PAOs for Adolescents
There has been recent momentum in the field of adolescent and young adult hip preservation surgery, with the goal being preventing degenerative osteoarthritis related to DDH.The Bernese PAO is a technique developed in Switzerland and has gained popularity over the past several decades.In this osteotomy, specific cuts are made around the acetabulum to allow for a complete reorientation of the acetabular cartilage while maintaining an intact posterior column and without causing any structural changes to the intrapelvic space (Fig 11).The goal in an osteotomy is to realign the native acetabulum to allow for improved acetabular coverage of the femoral head (Figs 12 and  13).This theoretically improves abnormal contact forces of the hip that predispose the hip to early degenerative osteoarthritis and early hip arthroplasty.
The current indications for patients to undergo PAO include young patients with hip pain who have a closed triradiate acetabular cartilage growth center, radiographic evidence of femoral head uncoverage due to a shallow acetabulum, and a congruent hip joint without radiographic signs of arthritic degeneration.The recent developments in adolescent and young adult hip preservation surgery are in refining patient selection as to who can most benefit from the procedure.Although a strict age cutoff for the procedure is not well defined, poorer outcomes after PAO have been associated in patients aged >35 years. 51To optimize patient selection, several centers have been using a delayed gadoliniumenhanced MRI of cartilage protocol preoperatively to specifically

FIGURE 8
Schematic of the differences between Salter, Dega, and Pemberton osteotomies.

FIGURE 9
Lateral view of the pelvis, with the 3 characteristic osteotomies surrounding the acetabulum in a triple innominate osteotomy.

FIGURE 10
A, A 10-year-old skeletally immature girl with bilateral hip dysplasia with deficient coverage of bilateral femoral heads.B, Four months' status after left triple innominate osteotomy with improved coverage of the left femoral head.evaluate early cartilage degeneration that is not detected by using routine radiography. 52,53 his tool can be helpful in selecting patients without cartilage degeneration who can benefit most from PAO.
Early-term and midterm outcomes of PAOs have been favorable in appropriately selected adolescents or young-adult patients.Most patients demonstrate improved hip pain symptoms after PAO.A detailed evaluation of patient-reported outcomes in the short-term revealed significant improvement in quality of life, pain, and function after PAO. 54More modest improvements in patient-related outcomes after surgery are associated with patients with milder radiographic DDH and obesity. 54The PAO appears to have an excellent result in the intermediate term.Several studies revealed that 93% to 95% of young patients undergoing PAO (mean age: 25.4-26 years) did not require a hip replacement at 10 years' follow-up. 55,56 here is a paucity of long-term follow-up of PAO.The only long-term study of >30 years' follow-up revealed that as many as 71% of patients continued to progress to develop pain symptoms, have radiographic evidence of osteoarthritis, or require hip replacement after PAO. 57However, this sample did not represent a strict selection criterion for surgery that is often used today because advanced osteoarthritis was present in 24%

FIGURE 11
Lateral view of the pelvis, with the characteristic osteotomies surrounding the acetabulum in PAO.The posterior column of the acetabulum is preserved, which differs from a triple innominate osteotomy.

FIGURE 12
A 17-year-old skeletally mature girl with bilateral hip pain and dysplasia with deficient coverage of bilateral femoral heads. of the hips before PAO in the study.More time will be required to truly appreciate the long-term benefit of the PAO procedure.

CONCLUSIONS
The treatment of DDH remains challenging, yet recent advances have refined our understanding of how best to survey for the condition during infancy, minimize complications during early treatment, and refine the selection of patients who can best benefit from hip preservation surgery.The ideal continued target would be to prevent missed hip dislocations or dysplasia during the infant period, prevent AVN during early treatment, and decrease the incidence of total hip arthroplasty in adulthood related to undertreated DDH.

FIGURE 4 AP
FIGURE 4AP pelvis radiograph of a left-hip dislocation.On an AP pelvis radiograph, classic measurements include drawing several lines to help identify dysplasia.H is drawn as a horizontal line, connecting the bilateral acetabular triradiate cartilage.P is then drawn perpendicular to H at the lateral edge of the acetabulum.In the normal right hip, the ossific nucleus rests along the bottom-inner quadrant formed by the intersection of the 2 lines.In the dislocated hip, the ossific nucleus rests lateral to the intersection of the 2 lines.S should reveal a smooth arch from the obturator foramen to the inferior aspect of the femoral neck, as in the right hip. S is disrupted on the left hip, suggesting dislocation.The acetabular index is the angle formed along the acetabular roof and H, with steeper values indicating acetabular dysplasia.Notice also that the left femoral head ossific nucleus is smaller, and its appearance is more delayed compared with the nondysplastic side.AI, acetabular index; AP, anteroposterior; H, Hilgenreiner line; P, Perkins line; S, arc of Shenton.
positive hip who fail to stabilize after initial Pavlik harness treatment, authors of recent literature suggest that a trial of a more rigid abduction hip orthosis, such as an Ilfeld orthosis (Fig 6), may obviate the need for either closed or open reduction in the operating room.Sankar et al 28 demonstrated that a stable hip reduction was achieved in 82% of patients who underwent rigid orthosis treatment after Pavlik harness failure in Ortolani-positive hips, with equivalent radiographic outcomes to closed reduction and casting being observed.Rigid abduction orthotic management allows for an alternative pathway to avoiding general anesthesia and casting in young children.Complications of the Pavlik harness or abduction orthoses are rare, although they can include avascular necrosis (AVN) of the femoral head, skin irritation, and femoral nerve palsy.Femoral nerve palsy is apparent when the infant stops demonstrating spontaneous knee extension while in the Pavlik harness.In a recent study, researchers compiled cases of femoral nerve palsy with Pavlik harness treatment and demonstrated that all patients recovered nerve function after the discontinuation or loosening of the Pavlik harness straps. 29More importantly, patients who developed femoral nerve palsy had a high (47%) failure rate of Pavlik harness treatment, possibly indicating that this complication occurs in more severe cases of DDH or that the

FIGURE 7 A 5 -
FIGURE 7A 5-year-old girl, 2 years after right-hip open reduction, who underwent femoral and pelvic osteotomy, with the development of femoral head fragmentation and irregularity suggestive of AVN.

FIGURE 13 (
FIGURE 13(Continued) Six months' status after right PAO with improved coverage of the right femoral head.

TABLE 1
General Treatment Algorithm for Hip Dislocation Galeazzi sign.With the pelvis level on a flat surface, the heights of the knees are asymmetric.
Novais EN, Hill MK, Carry PM, Heyn PC.Is age or surgical approach associated with osteonecrosis in patients with developmental dysplasia of the hip?A meta-analysis.Clin Orthop Relat Res.2016;474(5):1166-1177 43.Schoenecker PL, Strecker WB.Congenital dislocation of the hip in children.Comparison of the effects of femoral shortening and of skeletal traction in treatment.J Bone Joint Surg Am. 1984;66(1):21-27 44.Ning B, Yuan Y, Yao J, Zhang S, Sun J. Analyses of outcomes of one-stage operation for treatment of latediagnosed developmental dislocation of the hip: 864 hips followed for 3.2 to 8.9 years.BMC Musculoskelet Disord.2014;15:401 45.Yagmurlu MF, Bayhan IA, Tuhanioglu U, Kilinc AS, Karakas ES.Clinical and radiological outcomes are correlated with the age of the child in single-stage surgical treatment of developmental dysplasia of the hip.Acta Orthop Belg.