MCQs – Hip 3

Modern Study Review (AI-Generated)

High-Yield Summary

This topic is a staple of the Royal College exam, focusing heavily on pediatric hip disorders including SCFE, CDH, Perthes disease, and femoral neck fractures. The single most important clinical trade-off is the risk of avascular necrosis (AVN) versus achieving stable hip reduction or fixation, especially in older children and displaced fractures. The examiner often forces a choice between closed versus open reduction or osteotomy based on patient age, deformity severity, and vascular risk. While classic teaching favors closed reduction in younger children, modern practice increasingly emphasizes early open reduction and tailored osteotomies to minimize AVN and optimize hip biomechanics.

High-Yield Decision Matrix

Active Recall Q&A

SCFE

Q: What deformities are expected in a child with SCFE having a 50° Southwick angle on AP and 30° on lateral?
A: Obligatory external rotation deformity in flexion, varus hip, limp, and decreased internal rotation.
Related Pearl: The Southwick angle quantifies slip severity and guides treatment; external rotation deformity reflects posterior displacement of the femoral head.

Q: What degree of slip on the lateral Southwick angle is considered mild in SCFE?
A: A slip of 30-50 degrees on the lateral view is considered mild.
Related Pearl: Mild slips often present with subtle clinical signs but require close monitoring to prevent progression.

CDH (Congenital Dislocation of the Hip)

Q: What are the anatomical blocks to reduction in CDH?
A: Inverted labrum, pulvinar, capsule (hourglass constriction), ligamentum teres, and psoas tendon (causes hourglass constriction). Acetabular version does not influence reduction.
Related Pearl: Recognizing these blocks is critical to avoid failed closed reductions and subsequent AVN.

Q: Why is closed reduction hazardous in a 4-year-old with CDH?
A: It carries a high risk of avascular necrosis (AVN).
Related Pearl: Older children have less remodeling potential and more fragile blood supply, increasing AVN risk.

Q: What hip positions increase the risk of AVN in CDH treatment?
A: Extreme abduction causes AVN; extreme hyperflexion may force the femoral head inferiorly within the acetabulum.
Related Pearl: Safe positioning during reduction is essential to preserve femoral head vascularity.

Q: How common is truly congenital hip dislocation at birth, and which side is more affected?
A: It is uncommon and more common on the left side.
Related Pearl: Left-sided predominance may relate to intrauterine positioning and vascular factors.

Osteotomies and CP

Q: What is the indication for Chiari osteotomy?
A: Coxa magna with lateral subluxation.
Related Pearl: Chiari osteotomy medializes the acetabulum to improve coverage in subluxated hips.

Q: Why is innominate osteotomy inappropriate initially in children with cerebral palsy?
A: Because acetabular deficiency is not the initial problem; it is a paralytic problem.
Related Pearl: Posterior acetabular deficiency may develop later and is treated with Dega osteotomy.

Perthes Disease

Q: What factors portend a worse prognosis in Perthes disease?
A: Whole head involvement, female sex, loss of containment, and presence of metaphyseal cysts.
Related Pearl: Females tend to have more severe disease and worse outcomes.

Q: What are the Caterrall “Head at Risk” signs in Perthes disease?
A: Gage’s sign, metaphyseal cysts, horizontal physis, lateral epiphyseal calcification, and lateral subluxation.
Related Pearl: These radiographic signs predict femoral head collapse and poor prognosis.

Q: What age and radiographic involvement indicate the worst prognosis in Perthes?
A: Age of onset beyond 8 years and involvement of the lateral pillar.
Related Pearl: Older children have less remodeling potential; lateral pillar involvement indicates severe epiphyseal damage.

Q: What is the classic age range for Perthes disease?
A: 4-9 years, but it can appear as early as 2 and as late as 12 years.
Related Pearl: Early diagnosis within this window improves management outcomes.

Q: What causes coxa breva in Perthes disease, and how should it be treated?
A: Coxa breva results from AVN causing a short neck, often in varus with trochanteric overgrowth. It should not be treated with varus osteotomy; abductor strengthening and distal/lateral GT transfer may help.
Related Pearl: Varus osteotomy worsens abductor mechanics in coxa breva.

DDH (Developmental Dysplasia of the Hip)

Q: What surgical options exist for an older DDH child with trochanteric overgrowth due to AVN?
A: Growth arrest of the greater trochanter if young; distal transfer of the greater trochanter if older.
Related Pearl: Trochanteric overgrowth causes abductor insufficiency and Trendelenburg gait.

Femoral Neck Fractures

Q: Which femoral neck fracture type has the worst prognosis for AVN?
A: Transepiphyseal (Delbert I) fractures with dislocation of the head have an AVN rate approaching 100%.
Related Pearl: Preservation of the femoral head blood supply is nearly impossible with transepiphyseal fractures.

Q: What is the AVN rate for basicervical (Delbert III) femoral neck fractures in children?
A: Nearly 25%, which is higher than in adults.
Related Pearl: Pediatric femoral neck fractures have different vascular risks compared to adults, influencing prognosis.

Classic Clinical Notes

• In a kid with SCFE with a 50 degree head-neck shaft angle on the AP and a 30 degree head-neck shaft angle on the lateral (Southwick angles), there would be an obligatory external rotation deformity in flexion, a varus hip and limp, and a decrease in internal rotation. A 30-50 degree slip on the lateral is considered to be a mild slip (normal is adduction deformity of the hip, postural scoliosis, and a valgus deformity of the knee may develop.

• The following are blocks to reduction of CDH: inverted labrum, pulvinar, capsule (hour glass constriction), ligamentum teres, psoas tendon (causes the hourglass constriction); acetabular version does not influence reduction.

• In a 4 year old with CDH, doing a closed reduction will be very hazardous for creating AVN.

• Extreme abduction will cause AVN in CDH. Extreme hyperflexion may force the heads inferiorly within the acetabulum.

• A truly congenital dislocation of the hip (present at birth) is uncommon. It is more common on the left.

• Indications for Chiari include coxa magna with subluxation laterally.

• In a child with CP, innominate osteotomy is inappropriate because acetabular deficiency is not the problem, at least not initially – this is a paralytic problem. Later on, there may be acetabular deficiency more POSTERIORLY – treat with Dega osteotomy.

• The following portends a worse prognosis in Perthes: whole head involvement, females (tend to get more head involvement), loss of containment, and the presence of metaphyseal cysts.

• The Caterrall “Head at Risk” signs for Perthes include: Gage’s sign, metaphyseal cysts, horizontal physis, lateral epiphyseal calcification, lateral subluxation. In the final analysis, age of onset beyond 8, and involvement of the lateral pillar may be the worst.

• For the older DDH kid with trochanteric overgrowth because of AVN, surgical alternatives to deal with the limp and trendelenberg include either a growth arrest of the GT if young, and if older, a distal transfer of the GT.

• The classic age for Perthes is 4-9, although it can appear in kids as young as 2, and as old as 12.

• Coxa breva secondary to Perthes is a result of AVN – the neck is short, and often in varus with trochanteric overgrowth. Do no treat this with a varus osteotomy. Abductor strengthening, and distal/lateral transfer of the GT may be helpful.

• The worst of the femoral neck fractures is the transepiphyseal (Delbert I). With dislocation of the head, the AVN rate approaches 100%. Rates for the remaining probably depend mostly on displacement, although the interesting thing is that the basicervical fractures (III) have an AVN rate of nearly 25%, which is very different than in the adults.

Last Updated on January 25, 2026 by Christian Veillette