Residency · Residency · Orthopedic Surgery
Developmental Dysplasia of the Hip
Introduction
Developmental dysplasia of the hip (DDH) encompasses a spectrum of abnormalities ranging from mild acetabular dysplasia to frank dislocation of the femoral head. Early detection and treatment are paramount, as untreated DDH leads to progressive joint degeneration and is a leading cause of hip arthroplasty in young adults. The orthopedic surgeon must be proficient in screening, diagnosis, and age-appropriate management.
Epidemiology and Risk Factors
The incidence of clinical instability at birth is approximately 1 per 100 live births, while true dislocation occurs in 1 to 2 per 1,000. DDH has a strong female predominance (4 to 8 times more common) due to ligamentous laxity from maternal estrogen. The left hip is affected more commonly than the right (60% left, 20% right, 20% bilateral). Risk factors include breech presentation (especially frank breech, the strongest single risk factor), family history of DDH (12-fold increased risk with an affected first-degree relative), first-born child (tighter uterine environment), oligohydramnios and other packaging disorders (torticollis, metatarsus adductus), and swaddling with legs in extension and adduction.
Pathoanatomy
The normal neonatal hip is inherently unstable due to the cartilaginous acetabulum and ligamentous laxity. In DDH, the acetabulum is shallow and excessively anteverted. The labrum may become inverted (limbus), blocking reduction. Capsular redundancy allows femoral head subluxation or dislocation. With persistent displacement, secondary adaptive changes develop: pulvinar hypertrophy (fibrofatty tissue in the acetabulum), ligamentum teres elongation and hypertrophy, iliopsoas tendon constriction over the acetabular rim (hourglass deformity of the capsule), and transverse acetabular ligament narrowing.
Clinical Examination
Neonatal Period (0-6 months)
The Ortolani test is performed with the hip flexed to 90 degrees, gently abducting while lifting the greater trochanter. A palpable "clunk" indicates reduction of a dislocated hip. The Barlow test is performed with the hip flexed, adducting and applying a posteriorly directed force. A "clunk" indicates the hip dislocates (a positive test means an unstable hip that can be dislocated). A true clunk (pathologic) must be distinguished from a click (usually benign, from ligaments or tendons). Asymmetric skin folds and apparent limb length discrepancy (Galeazzi sign) may be present.
Older Infant and Walking Child
The Ortolani and Barlow tests become negative after 3 to 6 months as soft tissues contract. Limited hip abduction (less than 60 degrees) is the most reliable clinical sign. The Galeazzi sign shows apparent shortening of the thigh on the affected side. A Trendelenburg gait or waddling gait (in bilateral cases) and increased lumbar lordosis to compensate for hip flexion contracture may be observed.
Imaging
Ultrasound
Ultrasound is the primary imaging modality for infants under 4 to 6 months (prior to femoral head ossification). The Graf classification measures the alpha angle (bony acetabular coverage) and beta angle (cartilaginous coverage). Type I is normal (alpha greater than 60 degrees). Type II is physiologically immature (IIa, age less than 3 months) or dysplastic (IIb, age greater than 3 months). Type III is subluxated. Type IV is dislocated. Dynamic ultrasound evaluates stability during provocative maneuvers. Screening is recommended at 6 weeks for high-risk infants (breech, family history, clinical concern).
Radiography
Radiography is used after 4 to 6 months when the femoral head ossific nucleus appears. Hilgenreiner's line is a horizontal line through the triradiate cartilages. Perkins' line is a vertical line at the lateral edge of the acetabulum. The femoral head ossific nucleus should lie in the inferomedial quadrant formed by these lines. Shenton's line is a smooth arc along the medial femoral neck and superior obturator foramen; disruption indicates subluxation or dislocation. The acetabular index is the angle between Hilgenreiner's line and a line along the acetabular roof; normal is less than 30 degrees at birth, decreasing with age.
Age-Based Treatment Algorithm
| Age | Primary Treatment | Key Details | Success Rate |
|---|---|---|---|
| 0-6 months | Pavlik harness | Flexion 100-110°, abduction 50-70°; full-time 6-12 weeks | 85-95% |
| 6-18 months | Closed reduction + spica cast | Under GA with arthrography; adductor tenotomy if safe zone narrow | Variable |
| 18 months - 4 years | Open reduction | Anterior approach (Smith-Petersen) ± pelvic osteotomy | Requires osteotomy |
| > 4 years | Combined procedures | Open reduction + pelvic osteotomy + femoral osteotomy (shortening/varus/derotation) | Complex |
0-6 Months: Pavlik Harness
The Pavlik harness is the first-line treatment for infants diagnosed in the first 6 months. It maintains the hip in flexion (100 to 110 degrees) and abduction (50 to 70 degrees) to center the femoral head in the acetabulum. It is worn full-time for 6 to 12 weeks until the hip is clinically and ultrasonographically stable. Success rates reach 85 to 95% for Ortolani-positive hips, with lower rates for irreducible (Ortolani-negative) dislocations. Complications include Pavlik harness disease (avascular necrosis from excessive abduction or forced positioning) and femoral nerve palsy (from excessive flexion). If the hip does not reduce within 3 to 4 weeks, the harness should be discontinued to avoid AVN.
6-18 Months: Closed Reduction and Spica Casting
Closed reduction is indicated when the Pavlik harness fails or diagnosis is made after 6 months. It is performed under general anesthesia with arthrography to confirm concentric reduction. An adductor tenotomy is performed if the safe zone of Ramsey (range between maximum abduction and redislocation position) is narrow. The hip is immobilized in a spica cast in the human position (100 degrees flexion, 40 to 50 degrees abduction, neutral rotation) for 12 weeks (changed at 6 weeks). Post-reduction CT or MRI confirms maintained reduction.
18 Months to 4 Years: Open Reduction
Open reduction is typically required as soft tissue contractures prevent concentric closed reduction. The medial approach (Ludloff or Ferguson) is used in younger patients (under 12 to 18 months) and avoids capsulorrhaphy. The anterior approach (Smith-Petersen) is preferred after 12 to 18 months, allowing capsulorrhaphy and addressing all blocking structures. Open reduction is often combined with a pelvic osteotomy and/or femoral shortening osteotomy in older children.
Over 4 Years: Combined Procedures
Open reduction is combined with a pelvic osteotomy (Salter innominate, Pemberton, Dega) and femoral osteotomy (shortening, varus, derotation). Femoral shortening reduces pressure on the femoral head and lowers the risk of AVN after reduction.
Complications
AVN of the femoral head is the most significant complication of treatment, with the highest risk occurring with forced abduction, delayed diagnosis, and repeated manipulations. Residual dysplasia may require periacetabular osteotomy (PAO) in adolescence or young adulthood. Redislocation requires revision reduction and may necessitate additional procedures. Stiffness is rare in young children but may occur after prolonged immobilization.
Clinical Pearls
The Ortolani test detects a dislocated hip that can be reduced, while the Barlow test detects a hip that can be dislocated. Both become unreliable after 3 to 6 months as soft tissues tighten. The Pavlik harness is most effective when initiated before 6 weeks of age; if the hip has not reduced by 3 to 4 weeks, the harness should be discontinued to prevent Pavlik harness disease. AVN is the most serious complication of DDH treatment and is directly related to excessive abduction, forceful reduction, or prolonged immobilization in non-physiologic positions. Ultrasound is the imaging modality of choice before 4 to 6 months; after the ossific nucleus appears, standard radiography with Shenton line, Perkins line, and acetabular index guides management.
References
- American Academy of Pediatrics. Clinical practice guideline: early detection of developmental dysplasia of the hip. Pediatrics. 2000;105(4):896-905.
- Weinstein SL, Mubarak SJ, Wenger DR. Developmental hip dysplasia and dislocation: Part II. J Bone Joint Surg Am. 2003;85(10):2024-2035.
- Graf R. The diagnosis of congenital hip-joint dislocation by the ultrasonic compound treatment. Arch Orthop Trauma Surg. 1980;97(2):117-133.
- Pavlik A. The functional method of treatment using a harness with stirrups as the primary method of conservative therapy for infants with congenital dislocation of the hip. Clin Orthop Relat Res. 1992;(281):4-10.