Developmental Dysplasia of Hip (DDH) — Screening & Management

Developmental dysplasia of the hip (DDH) encompasses a spectrum of abnormalities in the developing hip, ranging from mild acetabular dysplasia to frank dislocation, in which the femoral head is not properly seated within the acetabulum. It is the most common musculoskeletal condition identified by newborn screening. Early diagnosis and treatment are essential — untreated DDH leads to abnormal hip development, progressive subluxation or dislocation, and early onset hip osteoarthritis in adulthood.

• Incidence: approximately 1–2 per 1000 live births have frank dislocation; up to 10–20 per 1000 have some degree of instability at birth; female:male ratio 6:1; left hip more commonly affected than right (due to the foetal position — left occiput anterior presentation increases left hip adduction against the mother`s sacrum); bilateral involvement in approximately 20% of cases
• Risk factors: female sex; first-born child; breech presentation (most significant risk factor — particularly frank breech, 20× increased risk); positive family history (12–33× increased risk if first-degree relative affected); oligohydramnios; swaddling with hips extended and adducted (culturally specific risk); restricted intrauterine movement; neuromuscular disorders
• The developing acetabulum requires the femoral head to be correctly positioned within the socket for normal concentric development — the femoral head acts as a template for acetabular growth; if the femoral head is dislocated or subluxed, the acetabulum remains shallow (dysplastic) and the femoral head deforms; the longer the hip remains dislocated, the worse the deformity

• Ortolani test: a dislocated hip is reduced by the examiner; patient supine; hip flexed to 90°; gentle abduction with upward lift of the greater trochanter; a palpable/audible "clunk" as the femoral head reduces back into the acetabulum = positive Ortolani; tests for a reducible dislocation (the hip is dislocated at rest and reduces with the manoeuvre); the Ortolani "clunk" must be distinguished from benign "clicks" which are soft tissue snapping sounds with no clinical significance
• Barlow test: a located hip is dislocated by the examiner; hip flexed to 90°; gentle adduction and posterior pressure on the greater trochanter; the hip is provoked to dislocate; a palpable "clunk" as the femoral head subluxes or dislocates posteriorly = positive Barlow; tests for a dislocatable (unstable) hip; Ortolani = reduces a dislocated hip; Barlow = dislocates a located hip — these are complementary tests performed together in the newborn examination
• Signs in the older infant and child: limited hip abduction in flexion (most reliable sign after 3 months); asymmetric skin folds (Galeazzi sign — apparent femoral shortening when hips and knees are flexed — the dislocated side knee is lower); waddling gait and Trendelenburg gait in the walking child; limb length discrepancy; delayed walking
• UK national screening programme: clinical examination of all newborns (Ortolani and Barlow tests) at the newborn and 6-week check; targeted ultrasound screening of high-risk infants (breech presentation, positive family history, clinical instability) at 4–6 weeks; universal ultrasound screening is not currently recommended in the UK (unlike Germany and some other European countries) due to over-diagnosis and overtreatment concerns

• Ultrasound (Graf classification): the investigation of choice under 4–6 months of age; the femoral head is cartilaginous (not yet ossified) and is not visible on plain X-ray; ultrasound uses the bony and cartilaginous acetabular rim as landmarks; the Graf classification measures the alpha angle (bony acetabular angle — normal >60°) and beta angle (cartilaginous roof angle); Graf Type I: normal (>60°); Type IIa: physiological immaturity (50–59°, acceptable under 3 months); Type IIb: delayed ossification (>3 months, 50–59°); Type IIc/D: critical (43–49°, at risk); Type III/IV: dislocated
• Plain radiograph (AP pelvis): used after 4–6 months of age when the femoral head ossification centre is present; the ossification centre normally appears at 3–6 months; Hilgenreiner`s line, Perkins line, and the Shenton`s arc are the key landmarks

• Pavlik harness rules: the hip must be confirmed as reduced within 2–3 weeks by ultrasound; if the hip is not reduced by 3–4 weeks, the harness should be abandoned — continued use with an unreduced hip causes posterior acetabular erosion (Pavlik harness disease) which significantly complicates subsequent closed or open reduction; the harness flexes the hip to approximately 100° and allows active abduction but prevents adduction and extension

• AVN of the femoral head as a complication of DDH treatment: the most serious complication of DDH treatment at any age; caused by excessive or forced abduction (stretching the retinacular vessels) or by pressure from a poorly positioned spica cast; the risk is highest with: forced abduction reduction without pre-traction, open reduction in the older child, and high-riding dislocations requiring greater reduction forces; the Ramsey zone of safety defines the range of abduction that achieves reduction without excessive pressure — within this zone, AVN risk is minimised; femoral shortening osteotomy reduces tension and lowers AVN risk in older children requiring open reduction
• Periacetabular osteotomy (Bernese PAO) for adult DDH: indicated for symptomatic acetabular dysplasia (lateral centre-edge angle <25°, Tönnis angle >10°) in young adults without significant OA (Tönnis OA Grade 0–1); the Bernese PAO (Ganz) mobilises the acetabular fragment on all sides (four cuts) while preserving the posterior column and pelvic ring continuity; the acetabulum is redirected to improve lateral coverage; good to excellent results in 70–80% at 10 years; failure predictors — advanced OA, spherical incongruity, patient age >40
• THA in DDH — technical challenges: complex primary THA; features — dysplastic shallow acetabulum, medialized or high-riding hip centre, small femoral head, anteverted femoral neck, narrow femoral canal, contracted soft tissues, shortened limb; key technical points: restoring the true acetabular centre of rotation (not cementing a cup in the false acetabulum position), bone grafting the dysplastic acetabulum if coverage is inadequate, subtrochanteric shortening osteotomy if the hip is high-riding (>3–4 cm proximal migration), careful leg length equalization

• Ortolani: reduces a dislocated hip (clunk of reduction); Barlow: dislocates a located hip (clunk of dislocation); both performed in newborn examination; "clunk" is significant, "click" is benign
• Risk factors: female, breech (most significant — 20× increased risk), first-born, family history, oligohydramnios, left hip
• Graf ultrasound: alpha angle >60° = normal; 50–59° = Type IIa (physiological if <3 months); <43° = dislocated; investigation of choice under 4–6 months
• Perkins line + Hilgenreiner line: ossification centre in inferomedial quadrant = normal; superolateral quadrant = dislocated
• Shenton`s arc: smooth = normal; broken = superior displacement of femoral head
• Pavlik harness: 0–6 months; 85–95% success; check reduction at 2–3 weeks by USS; abandon at 3–4 weeks if not reduced — Pavlik disease (posterior acetabular erosion) if continued with irreducible hip
• AVN: most serious DDH treatment complication; caused by forced abduction; Ramsey zone of safety defines safe reduction range; femoral shortening reduces risk in older children
• Adult DDH: Bernese PAO for symptomatic dysplasia without OA in young adults; lateral centre-edge angle <25° = dysplastic; THA for established OA
• Acetabular index: normal <30° at birth, <25° at 1 year; elevated = dysplastic
• Spica cast human position: hip flexion 90–100°, abduction 40–50°, neutral rotation; arthrogram confirms reduction; medial dye pool <5 mm = adequate