Congenital dysplasia of the hip, also referred to as developmental dysplasia of the hip (DDH), includes a spectrum of pathologies that includes mild acetabular dysplasia with a stable hip, dysplasias associated with hip subluxation, and hip dislocation. Presentation may vary and often is associated with a progressive course.1
- The etiology may be multifactorial including 1 or more hormonal, mechanical, or genetic factors.2,3
- If subluxation or dislocation occurs and then persists, the femoral head becomes flattened and femoral anteversion occurs. The acetabulum becomes shallow and dysplastic.4
- The final common pathway in the development of DDH is increased laxity of the hip capsule, in which the hip fails to maintain a stable, smooth articulation at the interface of the femoral head and the acetabulum causing increased likelihood of continued issues with subluxation or dislocation.2
Epidemiology including risk factors and primary prevention
DDH is found in approximately 1.3 per 1000 infants and children.1
Major risk factors are as follows2,3,5:
- White race.
- Hip swaddling in extension.
- Being a woman (women:men ratio is approximately 6:1).
- Positive family history.
- Ligamentous laxity.
- Breech intrauterine positioning.
- Conditions that lead to a tighter intrauterine space including oligohydramnios, high birthweight (>4000g), and first pregnancy.
Musculoskeletal deformities secondary to a crowding phenomenon in the womb may be seen in association with DDH, including metatarsus adductus in 4%6 of cases and torticollis in about 8% of cases.7
Optimal femoral head and acetabular morphology depend intimately on a smooth, concentric reduction between the two with movement aiding in hip development. When the hip spends more time in subluxed or dislocated states, more opportunity exists for dysplastic changes to occur. Key points of pathoanatomy include2:
- Fatty tissues in the depths of the hip, as well as hypertrophy of the ligamentum teres, preventing reduction.
- The transverse acetabular ligament can also thicken, narrowing the opening of the acetabulum.
- The iliopsoas tendon may shorten and become taut across the anterior hip, creating an hourglass shape to the hip capsule and limiting access of the femoral head to the acetabulum.
- Over time, the displaced femoral head places pressure on the rim and labrum of the acetabulum, causing infolding and thickening of the labrum.
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
Early detection of DDH is critical because the pathology of DDH, along with subsequent clinical management, changes with time, as follows2,8:
- Neonates: DDH will be asymptomatic and requires screening by specific clinical maneuvers (Ortolani test and Barlow test, as subsequently described in the Physical Examination section) and/or imaging.
- Infants: After 2 to 3 months, soft tissues tighten and specific physical findings include limited hip abduction, thigh shortening (Galeazzi or Allis sign), and asymmetry of gluteal or thigh folds.
- Ambulatory children: Often present after a leg-length discrepancy, limp, or waddling gait is noticed. These children will have a positive Trendelenburg sign, with a shortened femur on the affected side.
- DDH is more commonly seen in the left hip (60%) but can often be found to be present bilaterally.5
Specific secondary or associated conditions and complications
Associated conditions and complications of DDH include avascular necrosis of the femoral head, persistent limp, premature development of degenerative arthritis of the hip, leg length discrepancy, lumbar lordosis, knee pain, scoliosis, and degenerative changes of the spine.3
If in utero hip dislocation occurs and the hips are not reducible on neonatal examination, chromosomal or neuromuscular conditions should be considered in the differential diagnosis. These conditions include myelomeningocele, arthrogryposis, and Ehlers-Danlos syndrome.5
2. ESSENTIALS OF ASSESSMENT
A thorough review of the listed risk factors (i.e., positive family history, sex, breech positioning, conditions leading to a tighter intrauterine space) should help guide the examiner’s suspicion for DDH when screening.
Hip examination is recommended to be performed on all infants during routine clinical examinations. Hip instability in the neonate is classically screened via the Barlow and Ortolani tests, with the infant in a supine position2:
Barlow test, which screens for dislocation of a non-displaced hip.
- The examiner adducts the flexed hip and gently pushes the thigh posteriorly to try and dislocate the femoral head.
- The test is positive if the hip is felt to slide out of the acetabulum.
Ortolani test, which screens for dislocation by trying to reduce a dislocated femoral head.
- Grasping the child’s thigh between the thumb and index finger, the examiner lifts the greater trochanter with the 4th and 5th fingers while simultaneously abducting the hip.
- The test is positive when the femoral head slips into the hip socket with a fine clunk that should be palpable but not audible.
Note that clicks audible during Barlow and Ortolani maneuvers are usually benign and result from soft tissues snapping over bony prominences.1
After 2 to 3 months of age, the soft tissues around the hip tighten, so the Barlow and Ortolani tests become unreliable. In infants at this stage of development, the examiner must consider other physical findings as follows2,8:
- Galeazzi (Allis) sign, which screens for shortening of the thigh.
- With the infant supine, the examiner flexes the hips and knees, looking for asymmetry in the height of the knees.
- This test is positive if 1knee (when flexed) is lower than the other.
- Asymmetry of the gluteal or thigh folds.
- Limited hip abduction, especially if assymmetric (more difficult to detect if DDH is bilateral).
- Apparent limb shortening. A direct measurement of the ‘true’ limb length can be obtained from anterior superior iliac spine to the medial malloli.
A walking child may present with abnormal gait signs, including any of the following2:
- Waddling gait.
- Positive Trendelenburg sign.
- Assymetry of pelvic alignment, as viewed from the frontal plane (use pelvic brim, anterior superior iliac spine, posterior superior iliac spine, and/or greater trochanters as landmarks).
Manual serial hip examinations are recommended until a child walks. Subsequently, gait anomalies, including a Trendelenberg limp, waddling, and hyperlordosis, may be clues to the presence of DDH.
Ultrasound is the diagnostic modality of choice, especially in asymptomatic infants, because it is superior to radiographs in evaluating cartilaginous structures of the femoral joint.2,3
- Placing the transducer on the greater trochanter allows visualization of the ilium, bony acetabulum, labrum, and femoral epiphysis, allowing visual confirmation of femoral head displacement, as well as pathologic malformation of bony and cartilaginous structures.2
- A dynamic technique, which assesses stability of the femoral head in the acetabulum as well as the static anatomy, is preferred.
- False-positives can occur in the early newborn period, because the acetabulum is immature and the joint has some temporary laxity (0-4 weeks of age).
- Favored for infants from 4 weeks to 4-6 months of age, which loses utility after 4-6 months.
- The Graf method of classification was developed in 1980 with severity ratings from type I (normal hip) to type IV (dislocated hip). A good quick reference for this classification is found at: http://radiopaedia.org/articles/graf-method-for-ultrasound-classification-of-developmental-dysplasia-of-the-hip
Radiographs (anteroposterior [AP] view) are recommended after femoral head ossification (4-6 months) occurs.2
- Lateral femoral head migration is measured by the intersection of the Hilgenreiner line (horizontal through the triradiate cartilage) and the Perkins line (vertical from the lateral acetabulum).
- The AP view is interpreted via the acetabular index (AI), which measures the slope of the ossified acetabular roof. AI >30 degrees is abnormal.
- A broken Shenton line (a curved line drawn from the medial femoral neck to the lower border of the superior pubic ramus) is indicative of hip subluxation or dislocation.
Computed tomography is helpful for follow-up as opposed to initial diagnosis.9
Magnetic resonance imaging is used to help evaluate for avascular necrosis in patients with progressive DDH.9
Hip arthrogram is primarily done in the operating room by an orthopedic surgeon to evaluate the joint during and/or after closed reduction of the hip.9
3. REHABILITATION MANAGEMENT AND TREATMENTS
Available or current treatment guidelines
Clinical practice guidelines on early detection and management have been published by the American Academy of Pediatrics in 2000.10 This report includes a clinical algorithm for screening and recommended actions in the presence of risk factors.
At different disease stages
All newborn infants should be evaluated at birth. The primary care practitioner bears the responsibility for initial assessment and newborn screening. Referral to an orthopedist should be made if a positive Ortolani or Barlow sign is detected. If the newborn screening exam is equivocal or negative in the presence of risk factors, periodic follow-up exams are recommended, as described in the clinical practice guidelines published by the American Academy of Pediatrics.5,10 Children with equivocal physical exam findings or increased risk factors should undergo imaging.
Triple diapering is a common practice in newborns, which lacks clinical evidence for effectiveness in treatment and may delay appropriate referral to orthopedics when clearly dislocated.3
The Pavlik harness is indicated for children with evidence of hip dysplasia and an abnormal ultrasound or persistent subluxation.5 Due to growth, adjustments of the straps every 2 weeks is required to account for the growth of infants. Failure to make these adjustments can result in additional hip pathology or dislocating a previously reduced hip.5 Weaning from the Pavlik harness over a 3 to 4 week period may start once the ultrasound findings become normal and serial clinical examinations demonstrate stability at the hips.5 After 6 months of age, the Pavlik harness is replaced by a hip abduction orthoses to manage persistent hip instability. If follow-up physical examinations and/or ultrasounds do not show that the hip is reduced after 3 to 4 weeks, the harness should be abandoned and orthopedic consultation obtained.
Closed reduction of the hips, followed by hip spica casting, is the preferred method of treatment for persistent dislocated hips in children under 18 months of age. Casts are typically used for 3 to 4 months, with cast changes every 6 weeks.5 If a child receives a spica cast, specialized car seating systems may need to be ordered such as the Hippo Car Seat as they spica cast may prohibit safe car transport while wearing.
Internal reduction is required when the Pavlik harness and/or closed reduction is ineffective. This most commonly occurs after the child is 18 months of age. Surgical interventions may include open reduction, percutaneous adductor tenotomy, psoas tenotomy, femoral osteotomy, and pericapsular osteotomy.3
Failure to adequately achieve reduction in the older child may lead to more chronic medical issues requiring continued treatment. Pain, osteoarthritis, and gait deviations may occur if the hip is not properly reduced. Long-term complications can arise, such as a need for earlier total hip arthroplasty in the young adult period.11 Postsurgical rehabilitation should include a physical therapy program focusing on stretching of tight hip and leg muscles, positioning, weight bearing, and appropriate orthoses.12
Coordination of care
Once DDH is identified, consultation with an orthopedic surgeon is required. On occasion, pediatric rehabilitation physicians may be asked to provide advice on positioning and splinting. Because undiagnosed or mismanaged DDH may lead to undesired consequences, communication between the primary care provider, orthopedist, and pediatric physical medicine and rehabilitation is essential. Patients and orthotists need communication regarding who is the primary physician managing the orthotic. If pediatric therapists are involved in helping the family use the hip positioning devices, it is important the therapists provide feedback to the physician directing the treatment program.
Patient & family education
Helping educate the family about the process of care necessary to screen for DDH can be of great value. They could be more likely to bring their child to the primary care provider for routine well-child visits (where serial hip exams can be performed), because a DDH diagnosis can often be missed.3,9
4.CUTTING EDGE/EMERGING AND UNIQUE CONCEPTS AND PRACTICE
5. GAPS IN THE EVIDENCE-BASED KNOWLEDGE
- Sewell MD, Rosendahl K, Eastwood DM. Developmental dysplasia of the hip. BMJ. 2009;339:1242-1248.
- Sankar, WN, Horn DH, Wells L, Dormans JP. The hip. In: Kliegman RM, Stanton BF, St. Geme JW III, Schor NF, Behrman RE, eds. Nelson Textbook of Pediatrics. 19th ed. Philadelphia, PA: Elsevier; 2011:2355-2365.
- Moberg-Wolff, E. Hip: developmental hip dysplasia. In: Nelson MR, ed. Pediatrics: Rehabilitation Medicine Quick Reference. New York, NY: Demos Medical; 2011:116-117.4.
- Aronsson D, Goldberg M, Kling T, Roy D. Developmental dysplasia of the hip. Pediatrics. Aug 1994; 94 (2).
- Alexander MA, Matthews DJ, eds. Pediatric Rehabilitation: Principles and Practice. 4th ed. New York, NY: Demos Medical; 2010:386-389.
- Paton RW, Choudry Q. Neonatal foot deformities and their relationship to developmental dysplasia of the hip. J Bone Joint Surg Br. 2009;91:655-658.
- Walsh JJ, Morrissy RT. Torticollis and hip dislocation. J Pediatr Orthop. 1998;18:219-221.
- Nemeth B, Narotam V. Developmental Dysplasia of the Hip. Pediatrics in Review. Dec 2012, 33(12). 553-561.
- Rossi, R, Alexander, M, Cuccurullo, SJ. Pediatric rehabilitation. In: Cuccurullo SJ, ed. Physical Medicine and Rehabilitation Board Review. 2nd ed. New York, NY: Demos Medical; 2010:713-808.
- Karmazyn, BK, Gunderman RB, Coley BD, et al. ACR Appropriateness Criteria on developmental dysplasia of the hip-child. J Am Coll Radiol. 2009;6:551-557.
- Herring JA. Tachdijan’s Pediatric Orthopedics. Philadelphia, PA: Elsevier Sanders; 2014.
- Driscoll SW, Skinner J. Musculoskeletal complications of neuromuscular disease in children. Phys Med Rehabil Clin N Am. 2008;19:163-194.
Original Version of the Topic:
Frank S. Pidcock, MD, Andrew H. Gordon, MD, PhD. Congenital hip dysplasia. Publication Date: 2013/01/09
Matthew McLaughlin, MD
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