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1. General Principles & Basic Science MCQs

Practice Set 24 of 789

This practice set contains high-yield board review questions covering key concepts in 1. General Principles & Basic Science. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 461

Topic: 1. General Principles & Basic Science
Which of the following factors has not been proven to increase the risk of thermal necrosis to a limb with a cast:
. Use of plaster
. Use of fiberglass
. Folding a splint into double-thickness
. Placing a recently casted limb on a pillow
. Using a dip water temperature more than 30°

Correct Answer & Explanation

. Use of fiberglass

Explanation

Fiberglass is less likely than plaster to produce thermal injury, likely because of the increased porosity. All of the other factors listed increase the risk of thermal necrosis.

Question 462

Topic: Infection, Pharmacology & VTE
According to the Kocher criteria, which of the following is one of the independent predictors used to differentiate septic arthritis from transient synovitis of the hip in a pediatric patient?
. History of preceding upper respiratory infection
. Serum CRP > 2.0 mg/dL
. Inability to bear weight
. Presence of knee pain
. Night sweats

Correct Answer & Explanation

. Inability to bear weight

Explanation

The four classic Kocher criteria are: inability to bear weight, temperature > 38.5°C, ESR > 40 mm/hr, and WBC > 12,000 cells/mm³. While CRP is highly sensitive and used in modified criteria, inability to bear weight is one of the original four.

Question 463

Topic: Surgical Anatomy & Approaches

A 7-year-old sustains a traumatic fall. Radiographs demonstrate an anterior dislocation of the radial head with an associated diaphyseal fracture of the ulna that is apex-anterior. Which nerve palsy is most commonly associated with this specific injury pattern?

. Ulnar nerve
. Anterior interosseous nerve
. Posterior interosseous nerve
. Superficial radial nerve
. Axillary nerve

Correct Answer & Explanation

. Posterior interosseous nerve

Explanation

This describes a Bado Type I Monteggia lesion. The posterior interosseous nerve (PIN) is the most frequently injured nerve in this anterior dislocation pattern.

Question 464

Topic: Biology, Genetics & Bone Healing

A patient presents with generalized hypermobility, a delayed closure of fontanelles, and the ability to appose the shoulders anteriorly at the midline. This disorder is most commonly caused by a mutation in which gene?

. COL1A1
. FGFR3
. RUNX2 (CBFA1)
. EXT1
. COMP

Correct Answer & Explanation

. RUNX2 (CBFA1)

Explanation

Cleidocranial dysplasia presents with clavicular hypoplasia/aplasia and delayed cranial suture closure. It is an autosomal dominant condition caused by a mutation in the RUNX2 (CBFA1) gene, critical for osteoblast differentiation.

Question 465

Topic: Infection, Pharmacology & VTE

According to the Kocher criteria, which of the following findings is NOT one of the four classic predictors used to differentiate pediatric septic arthritis of the hip from transient synovitis?

. Inability to bear weight
. Erythrocyte sedimentation rate (ESR) > 40 mm/hr
. Fever > 38.5 degrees C
. Serum C-reactive protein (CRP) > 2.0 mg/dL
. White blood cell count > 12,000 cells/mm3

Correct Answer & Explanation

. Serum C-reactive protein (CRP) > 2.0 mg/dL

Explanation

The original Kocher criteria include: non-weight bearing, ESR > 40 mm/hr, Fever > 38.5 C, and WBC > 12,000. While CRP > 2.0 mg/dL was later identified by Caird et al. as an excellent independent predictor, it is not one of the four original Kocher criteria.

Question 466

Topic: Biology, Genetics & Bone Healing

A 2-year-old boy with blue sclerae presents with his third long bone fracture. Genetic testing reveals a defect in Type I collagen. Which medical treatment has been shown to reduce fracture rates and improve bone density in this condition?

. Oral calcium supplementation
. Intravenous bisphosphonates
. Recombinant human growth hormone
. Vitamin D3
. Teriparatide

Correct Answer & Explanation

. Intravenous bisphosphonates

Explanation

Intravenous bisphosphonates (such as pamidronate) are the mainstay of medical treatment for moderate to severe Osteogenesis Imperfecta. They inhibit osteoclast resorption, leading to increased cortical thickness.

Question 467

Topic: Infection, Pharmacology & VTE

A 2-year-old boy is brought to the clinic because he refuses to bear weight on his left leg. Examination reveals minimal swelling and tenderness over the distal tibia. Initial radiographs are completely normal. What is the most appropriate next step?

. Immediate MRI of the tibia
. Aspiration of the ankle joint
. Immobilization in a long leg cast and repeat radiographs in 10-14 days
. Reassurance and immediate return to unrestricted activity
. Bone scan to rule out osteomyelitis

Correct Answer & Explanation

. Immobilization in a long leg cast and repeat radiographs in 10-14 days

Explanation

A Toddler's fracture is a nondisplaced spiral fracture of the distal tibia where initial radiographs are often normal. The standard of care is empiric immobilization and repeat imaging in 1-2 weeks.

Question 468

Topic: Infection, Pharmacology & VTE

A 2-year-old presents with a fever of 39.0°C, inability to bear weight on the right leg, an ESR of 50 mm/hr, and a serum WBC of 13,000/mm3. According to Kocher's criteria, what is the probability that this child has septic arthritis of the hip?

. 10%
. 40%
. 73%
. 93%
. 99%

Correct Answer & Explanation

. 93%

Explanation

Kocher's criteria for pediatric septic arthritis include: non-weight-bearing, ESR >40 mm/hr, fever >38.5°C, and WBC >12,000/mm3. The presence of all four criteria carries a 99% probability of septic arthritis.

Question 469

Topic: 1. General Principles & Basic Science
Which of the following levels of evidence should be assigned to a prospective, randomized therapeutic study with 80% follow-up:
. Level I
. Level II
. Level III
. Level IV
. Level V

Correct Answer & Explanation

. Level I

Explanation

A study may be level I as long as it has at least 80% follow-up.

Question 470

Topic: 1. General Principles & Basic Science
A prospective comparative study should be assigned which level of evidence:
. Level I
. Level II
. Level III
. Level IV
. Level V

Correct Answer & Explanation

. Level II

Explanation

A comparative study is one in which patients treated one way are compared with patients treated in another manner at the same institution. As long as the study is prospective, it can be assigned level II.

Question 471

Topic: 1. General Principles & Basic Science
A case-control study should be assigned which level of evidence?
. Level I
. Level II
. Level III
. Level IV
. Level V

Correct Answer & Explanation

. Level III

Explanation

A case-control study is considered level III evidence, as is a retrospective comparison study or a meta-analysis in which the lowest level of primary study is level III.

Question 472

Topic: Biology, Genetics & Bone Healing

A 10-year-old girl is noted to have a large head with delayed closure of the fontanelles, dental anomalies, and the ability to appose her shoulders anteriorly. Radiographs reveal hypoplastic clavicles. Which of the following genes is affected in this autosomal dominant condition?

. RUNX2 (CBFA1)
. FGFR3
. COL1A1
. SOX9
. FLNB

Correct Answer & Explanation

. RUNX2 (CBFA1)

Explanation

Cleidocranial dysplasia is caused by a mutation in the RUNX2 (CBFA1) gene, which is essential for osteoblast differentiation. Patients typically have absent or hypoplastic clavicles, delayed fontanelle closure, and supernumerary teeth.

Question 473

Topic: Biology, Genetics & Bone Healing

A 7-year-old girl is evaluated for a broad forehead, delayed tooth eruption, and the ability to appose her shoulders anteriorly. Radiographs show hypoplastic clavicles. What is the primary molecular defect associated with this syndrome?

. Defective osteoclast ruffled border function
. Mutation in the CBFA1/RUNX2 gene
. Abnormal type I collagen triple helix synthesis
. Defective Indian Hedgehog signaling pathway
. Mutation in the LRP5 gene

Correct Answer & Explanation

. Mutation in the CBFA1/RUNX2 gene

Explanation

Cleidocranial dysplasia is an autosomal dominant condition caused by mutations in the RUNX2 (CBFA1) gene. This gene encodes a master transcription factor essential for normal osteoblast differentiation.

Question 474

Topic: Biology, Genetics & Bone Healing

A 7-year-old boy presents with delayed tooth eruption, frontal bossing, and the ability to approximate his shoulders in the midline anteriorly. A mutation in which of the following genes is responsible for this condition?

. FGFR3
. COMP
. COL1A1
. RUNX2 (CBFA1)
. SOX9

Correct Answer & Explanation

. RUNX2 (CBFA1)

Explanation

The child has cleidocranial dysplasia, characterized by hypoplastic or absent clavicles, delayed cranial suture closure, and dental anomalies. It is an autosomal dominant condition caused by a mutation in the RUNX2 (CBFA1) gene, which regulates osteoblast differentiation.

Question 475

Topic: Biology, Genetics & Bone Healing

A 5-year-old child with blue sclerae, dentinogenesis imperfecta, and multiple prior fractures is started on pamidronate therapy. What is the primary mechanism of action of this medication?

. Stimulates osteoblast proliferation
. Inhibits osteoclast-mediated bone resorption
. Increases intestinal calcium absorption
. Enhances cross-linking of type I collagen
. Decreases renal calcium excretion

Correct Answer & Explanation

. Inhibits osteoclast-mediated bone resorption

Explanation

Pamidronate is a bisphosphonate used to treat Osteogenesis Imperfecta. It acts by inducing osteoclast apoptosis and inhibiting osteoclast-mediated bone resorption, thereby increasing bone mineral density and decreasing fracture rates.

Question 476

Topic: Biology, Genetics & Bone Healing

A 3-year-old child presents with progressive bowing of the lower extremities, short stature, and a waddling gait.

Laboratory studies show a normal serum calcium, markedly low serum phosphate, elevated alkaline phosphatase, and normal PTH. What is the most likely diagnosis?

. Nutritional rickets
. X-linked hypophosphatemic rickets
. Vitamin D-dependent rickets type I
. Renal osteodystrophy
. Hypophosphatasia

Correct Answer & Explanation

. X-linked hypophosphatemic rickets

Explanation

X-linked hypophosphatemic rickets results from a mutation in the PHEX gene, leading to excessive FGF23 and renal phosphate wasting. Classic lab findings include low phosphate, normal calcium, normal PTH, and normal vitamin D levels, distinguishing it from nutritional rickets.

Question 477

Topic: 1. General Principles & Basic Science

A patient who does not walk outdoors or independently but can walk with a walker in physical therapy is listed as what level according to the Gross Motor Function Measure (GMFM):

. Level 1
. Level 2
. Level 3
. Level 4
. Level 5

Correct Answer & Explanation

. Level 1

Explanation

The GMF C lassification System (GMFC S) is a concise way of expressing overall motor ability. According to this system, level 1 is walking and running indoors and out with impaired speed, level 2 is impairment in running on uneven surfaces, level 3 is ambulation indoors and out with assistive devices, and level 4 is limited walking with a walker, and level 5 is nonambulatory.

Question 478

Topic: 1. General Principles & Basic Science

The patient shown in the clinical photograph (Slide 1) and radiograph (Slide 2) has which of the following conditions:

. Klippel-Trenaunay-Weber syndrome
. Neurofibromatosis-1
. Proteus syndrome
. Gorham disease
. Maffucci syndrome

Correct Answer & Explanation

. Klippel-Trenaunay-Weber syndrome

Explanation

This patient has Klippel-Trenaunay-Weber syndrome. This syndrome is characterized by a triad of cutaneous nevi, varicose veins, and limb overgrowth in length and/or width.

Question 479

Topic: Physiology & Rehabilitation

Which of the following is a description of a closed kinetic chain exercise:

. The distal ends of a limb are against fixed resistance
. The distal ends of a limb are free to travel in space
. The distal limb exerts force against an elastic chain
. The limb is suspended from a chain
. Two limbs move together

Correct Answer & Explanation

. The distal ends of a limb are against fixed resistance

Explanation

A closed kinetic chain exercise is one in which the ends of a limb are fixed from free movement by resistance.

Question 480

Topic: Biology, Genetics & Bone Healing

The action of bisphosphonates is primarily upon which component of bone:

. Osteoclast
. Osteoblasts
. Cartilage
. Periosteum
. Nutrient vessel

Correct Answer & Explanation

. Osteoclast

Explanation

Bisphosphonates act to inhibit osteoclasts, thereby decreasing resorption and increasing bone mineral density in many conditions.

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