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Pediatric Hip MCQs

Practice Set 104 of 104

This practice set contains high-yield board review questions covering key concepts in Pediatric Hip. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 2061

Topic: Pediatric Hip
A patient is diagnosed with severe coxa vara (neck-shaft angle < 110 degrees). How does this proximal femoral morphology uniquely alter the biomechanics of the hip joint?
. Decreases the abductor moment arm and increases joint reaction force.
. Increases the abductor moment arm and decreases joint reaction force.
. Decreases both the abductor moment arm and joint reaction force.
. Increases both the abductor moment arm and joint reaction force.
. Has no effect on the abductor moment arm but increases shear forces.

Correct Answer & Explanation

. Increases the abductor moment arm and decreases joint reaction force.

Explanation

Coxa vara lateralizes the greater trochanter, which increases the abductor moment arm. This improved mechanical advantage decreases the required abductor force and the total joint reaction force, although it dramatically increases the bending moment across the femoral neck.

Question 2062

Topic: Pediatric Hip

A newborn is diagnosed with Spondyloepiphyseal Dysplasia Congenita (SEDC). Which of the following physical findings is expected, given the specific genetic mutation associated with this condition?

. Hitchhiker thumbs
. Short trunk with normal-length limbs
. Coxa vara and myopia
. Absent clavicles
. Polydactyly

Correct Answer & Explanation

. Coxa vara and myopia

Explanation

SEDC is caused by a COL2A1 mutation affecting Type II collagen, which is abundant in articular cartilage and the vitreous humor of the eye. Patients characteristically present with a short trunk, severe coxa vara, cleft palate, and ophthalmologic issues like myopia and retinal detachment.

Question 2063

Topic: Pediatric Hip

A 9-year-old girl presents with short stature, sparse hair, a bulbous pear-shaped nose, and finger joint deformities. Radiographs of her hands show cone-shaped epiphyses in the phalanges.

What other orthopedic manifestation is highly characteristic of this syndrome?

. Multiple osteochondromas
. Premature hip osteoarthritis resembling Legg-Calve-Perthes
. Atlantoaxial instability
. Scoliosis with rib fusions
. Osteosclerosis of the skull base

Correct Answer & Explanation

. Premature hip osteoarthritis resembling Legg-Calve-Perthes

Explanation

Trichorhinophalangeal syndrome (TRPS) Type 1 is caused by a TRPS1 gene mutation. Alongside the classic facial features and cone-shaped phalangeal epiphyses, patients frequently develop severe early-onset hip dysplasia and Perthes-like changes.

Question 2064

Topic: Pediatric Hip

A 10-year-old boy with Trichorhinophalangeal syndrome type 1 (TRPS1) complains of bilateral groin pain. Radiographs reveal flattening and fragmentation of both femoral heads. What is the expected long-term orthopedic outcome if this hip pathology is left untreated?

. Spontaneous resolution with normal spherical femoral heads
. Development of secondary osteosarcoma
. Premature secondary osteoarthritis requiring early arthroplasty
. Progression to slipped capital femoral epiphysis (SCFE)
. High-output cardiac failure

Correct Answer & Explanation

. Premature secondary osteoarthritis requiring early arthroplasty

Explanation

TRPS1 is associated with Legg-Calve-Perthes-like changes in the hips. These skeletal dysplasias lead to early joint incongruity and severe premature osteoarthritis.

Question 2065

Topic: Pediatric Hip
A 10-year-old boy has bilateral Legg-Calvé-Perthes-like hip changes, a bulbous nasal tip, and cone-shaped epiphyses on hand radiographs. This syndrome is caused by a defect in a gene that functions primarily as a:
. Structural collagen component
. Zinc-finger transcription repressor
. Fibroblast growth factor receptor
. Matrix metalloproteinase
. Transmembrane ion channel

Correct Answer & Explanation

. Zinc-finger transcription repressor

Explanation

TRPS Type 1 is caused by a mutation in the TRPS1 gene, which functions as a zinc-finger transcription repressor. This regulates the development of the perichondrium and articular cartilage.

Question 2066

Topic: Pediatric Hip
TRPS Type II (Langer-Giedion syndrome) shares many features with TRPS Type I, including sparse hair and cone-shaped epiphyses. Which of the following clinical findings uniquely distinguishes TRPS Type II from Type I?
. Legg-Calvé-Perthes-like hip disease
. Multiple osteochondromas
. Mandibular hypoplasia
. Blue sclerae
. Severe scoliosis

Correct Answer & Explanation

. Multiple osteochondromas

Explanation

TRPS Type II (Langer-Giedion syndrome) is caused by a contiguous gene deletion involving both the TRPS1 gene and the EXT1 gene, leading to the unique development of multiple osteochondromas not seen in Type I.

Question 2067

Topic: Pediatric Hip

A 10-year-old boy diagnosed with Trichorhinophalangeal Syndrome (TRPS) Type 1 presents with right hip pain and a limp. Pelvic radiographs show flattening and fragmentation of the right capital femoral epiphysis. This orthopedic manifestation of TRPS Type 1 most closely mimics which of the following conditions?

. Slipped capital femoral epiphysis
. Developmental dysplasia of the hip
. Legg-Calve-Perthes disease
. Coxa vara
. Femoroacetabular impingement

Correct Answer & Explanation

. Legg-Calve-Perthes disease

Explanation

TRPS Type 1 is characterized by a high incidence of avascular necrosis-like changes in the capital femoral epiphysis. This closely mimics Legg-Calve-Perthes disease and frequently leads to early-onset secondary osteoarthritis.

Question 2068

Topic: Pediatric Hip

An 8-year-old boy presents with a painful limp. Physical examination reveals fine sparse hair, a pear-shaped nose, and brachydactyly.

Hand radiographs show cone-shaped epiphyses. Which of the following hip pathologies is most characteristic of this patient's syndrome?

. Slipped capital femoral epiphysis
. Legg-Calve-Perthes-like avascular necrosis
. Developmental dysplasia of the hip
. Primary synovial chondromatosis
. Coxa vara

Correct Answer & Explanation

. Legg-Calve-Perthes-like avascular necrosis

Explanation

Trichorhinophalangeal syndrome (TRPS) Type 1 frequently presents with craniofacial abnormalities, sparse hair, and cone-shaped phalangeal epiphyses. The hallmark major joint manifestation is premature osteoarthritis secondary to Legg-Calve-Perthes-like avascular necrosis of the femoral heads.

Question 2069

Topic: Pediatric Hip
A 4-year-old child presents with a waddling gait. Radiographs show delayed ossification of the femoral heads with a fragmented appearance, but the acetabulum is normal and the child is otherwise healthy and of normal height. What is the most likely diagnosis?
. Legg-Calvé-Perthes disease
. Multiple Epiphyseal Dysplasia (Fairbank type)
. Meyer's dysplasia
. Spondyloepiphyseal dysplasia tarda
. Avascular necrosis secondary to steroids

Correct Answer & Explanation

. Meyer's dysplasia

Explanation

Meyer's dysplasia (dysplasia of the femoral capital epiphysis) is a benign variant of epiphyseal development. It often mimics Legg-Calvé-Perthes disease but occurs in younger children (2-4 years), is often bilateral, and typically resolves spontaneously without the significant collapse or deformity seen in Perthes.

Question 2070

Topic: Pediatric Hip

Which of the following biomechanical changes is most characteristic of coxa vara?

. Decreased hip abductor moment arm
. Increased overall hip joint reaction force
. Decreased bending moment across the femoral neck
. Increased hip abductor moment arm
. Increased functional leg length

Correct Answer & Explanation

. Decreased bending moment across the femoral neck

Explanation

In coxa vara, the decreased neck-shaft angle moves the greater trochanter more laterally, which increases the abductor moment arm. While this decreases the joint reaction force, it pathologically increases the bending moment and shear force across the femoral neck.

Question 2071

Topic: Pediatric Hip

Which of the following describes the biomechanical effect of coxa vara (decreased neck-shaft angle) on the hip joint?

. Increases the joint reaction force and decreases the bending moment at the femoral neck.
. Decreases the abductor moment arm and increases the joint reaction force.
. Increases the abductor moment arm, decreases the total joint reaction force, and increases the bending moment across the femoral neck.
. Decreases the abductor moment arm, decreases the joint reaction force, and decreases the bending moment across the femoral neck.
. Increases both the joint reaction force and the bending moment across the femoral neck.

Correct Answer & Explanation

. Increases the abductor moment arm, decreases the total joint reaction force, and increases the bending moment across the femoral neck.

Explanation

Coxa vara lateralizes the greater trochanter, increasing the abductor lever arm and thereby reducing the required abductor force and total joint reaction force. However, the more horizontal femoral neck experiences an increased shear force and bending moment, predisposing it to fatigue failure.

Question 2072

Topic: Pediatric Hip

A patient presents with severe coxa vara (neck-shaft angle of 95 degrees). Compared to a normal neck-shaft angle (130 degrees), which of the following biomechanical profiles is characteristic of coxa vara?

. Increased hip joint reaction force and increased femoral neck bending moment
. Increased hip joint reaction force and decreased femoral neck bending moment
. Decreased hip joint reaction force and increased femoral neck bending moment
. Decreased hip joint reaction force and decreased femoral neck bending moment
. Unchanged hip joint reaction force and increased femoral neck bending moment

Correct Answer & Explanation

. Decreased hip joint reaction force and increased femoral neck bending moment

Explanation

Coxa vara increases the abductor moment arm, which decreases the required abductor force and therefore decreases the hip joint reaction force. However, the more horizontal femoral neck increases the shear force and bending moment across the femoral neck, increasing the risk of femoral neck fracture.

Question 2073

Topic: Pediatric Hip

A Bernese periacetabular osteotomy (PAO) is performed for symptomatic developmental dysplasia of the hip (DDH). What is the primary biomechanical alteration at the hip joint achieved by this procedure?

. Lateralization of the hip joint center, increasing the abductor moment arm
. Medialization of the hip joint center, decreasing the lever arm of body weight
. Distalization of the greater trochanter, increasing abductor tension
. Anterior translation of the femoral head, increasing the Wiberg center-edge angle
. Posterior displacement of the acetabulum, decreasing pelvic tilt

Correct Answer & Explanation

. Medialization of the hip joint center, decreasing the lever arm of body weight

Explanation

A PAO allows the acetabulum to be reoriented to increase femoral head coverage (improving the center-edge angle). It also medializes the hip joint center of rotation, which decreases the lever arm of the body weight and subsequently reduces the joint reaction force.

Question 2074

Topic: Pediatric Hip

A patient with developmental dysplasia of the hip is found to have a center-edge (CE) angle of Wiberg of 12 degrees. How does this anatomic variation pathologically alter hip biomechanics?

. It increases the abductor moment arm, increasing joint forces.
. It decreases the articular contact area, resulting in increased superior joint contact stress.
. It lateralizes the center of rotation, permanently decreasing the body weight moment arm.
. It induces a functional shortening of the rectus femoris.

Correct Answer & Explanation

. It decreases the articular contact area, resulting in increased superior joint contact stress.

Explanation

A decreased CE angle (<20 degrees) indicates poor lateral acetabular coverage. This significantly decreases the contact area between the femoral head and acetabulum, leading to concentrated, elevated contact stresses superiorly and accelerating osteoarthritis.

Question 2075

Topic: Pediatric Hip

In a patient with untreated developmental dysplasia of the hip characterized by proximal migration of the femur, how is the biomechanical function of the gluteus medius primarily compromised?

. The resting muscle length is stretched, increasing passive tension.
. The abductor moment arm is decreased and the resting muscle length is shortened.
. The center of rotation is medialized, increasing the mechanical advantage.
. The line of action is shifted anteriorly, acting as a primary flexor.

Correct Answer & Explanation

. The abductor moment arm is decreased and the resting muscle length is shortened.

Explanation

Proximal migration of the greater trochanter decreases the horizontal distance between the hip center and the abductor insertion (decreased moment arm) and reduces the resting length of the muscle, resulting in a severe biomechanical disadvantage and weakness.

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