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1. General Principles & Basic Science MCQs

Practice Set 55 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 1081

Topic: 1. General Principles & Basic Science

A 12-year-old girl is diagnosed with Multiple Epiphyseal Dysplasia (MED). She complains of knee pain and a waddling gait. Which of the following radiographic findings is uniquely characteristic of this condition?

. Bullet-shaped vertebrae
. Double-layered patella
. Hitchhiker thumb
. Erlenmeyer flask deformity
. Metaphyseal flaring

Correct Answer & Explanation

. Double-layered patella

Explanation

A double-layered, or fragmented, patella observed on a lateral knee radiograph is a classic finding in Multiple Epiphyseal Dysplasia (MED). MED is caused by mutations in genes such as COMP, MATN3, and type IX collagen.

Question 1082

Topic: Biology, Genetics & Bone Healing

A 9-year-old boy presents with unusually wide cranial sutures, delayed closure of the fontanelles, and the ability to bring his shoulders together in the midline anteriorly. Which of the following best describes the underlying pathophysiology of his condition?

. Defective endochondral ossification
. Defective intramembranous ossification
. Mutation in the FGFR3 gene
. Deficiency in type I collagen production
. Defective osteoclastic resorption

Correct Answer & Explanation

. Defective intramembranous ossification

Explanation

The clinical picture describes Cleidocranial Dysplasia, which is caused by a mutation in the RUNX2 (CBFA1) gene. This gene is critical for osteoblast differentiation, leading primarily to defective intramembranous ossification of the clavicles, cranium, and pelvis.

Question 1083

Topic: Biology, Genetics & Bone Healing

A 6-month-old infant is evaluated for failure to thrive, hepatosplenomegaly, and cranial nerve palsies. Radiographs show a generalized, uniform increase in bone density with a "bone-within-a-bone" appearance in the spine. What is the primary cellular defect responsible for this condition?

. Impaired osteoblast differentiation
. Overactive osteoblasts producing excessive woven bone
. Absence of functional osteoclasts
. Fibrous tissue replacing normal bone marrow
. Defective chondrocyte proliferation in the growth plate

Correct Answer & Explanation

. Absence of functional osteoclasts

Explanation

The patient has malignant infantile osteopetrosis, a condition characterized by osteoclast failure (often due to carbonic anhydrase II or TCIRG1 mutations). The inability to resorb bone leads to excessively dense but brittle bones, marrow obliteration, and secondary hepatosplenomegaly from extramedullary hematopoiesis.

Question 1084

Topic: 1. General Principles & Basic Science
A 2.5-year-old boy has severe spastic diplegia and hips that are subluxating. His abduction is 20° on each side. The migration index is 35% on each side. Recommended treatment includes:
. Traction followed by bilateral Salter osteotomy
. Trochanteric transfer
. Nighttime abduction splinting
. Bilateral adductor lengthening and abduction bracing
. Physical therapy each day to stretch abductors along with night

Correct Answer & Explanation

. Bilateral adductor lengthening and abduction bracing

Explanation

If followed by postoperative bracing, lengthening of the adductors is usually successful in children younger than 4 to 6 years of age. Traction would not be appropriate because the muscles are spastic. The surgical plan does not include the most important component weakening the overactive adductors. Trochanteric transfer is not advisable in patients younger than 8 years old. Trochanteric transfer would not help decrease the overpull of the adductors which is the cause of the subluxation. Nighttime abduction splinting should be a component of the care after surgery. Bracing alone would not be an adequate treatment. Physical therapy in the absence of surgery does not seem to be enough to overcome the pull of the adductors.

Question 1085

Topic: Infection, Pharmacology & VTE

Definitive diagnosis of septic arthritis is made by:

. Magnetic resonance imaging
. Plain radiographs
. Needle aspiration
. Open biopsy
. Serologic testing

Correct Answer & Explanation

. Needle aspiration

Explanation

Definitive diagnoisis of septic arthritis is made by needle asperation.

Question 1086

Topic: Infection, Pharmacology & VTE

Osteomyelitis in the child

. requires operative debridement in the majority of cases.
. requires antibiotic therapy for 3 to 6 weeks.
. never causes growth disturbance of the involved bone.
. occurs in the diaphysis in most cases.
. Always crosses the physis in children

Correct Answer & Explanation

. requires antibiotic therapy for 3 to 6 weeks.

Explanation

Osteomyelitis in the child requires 3-6 weeks of antiobiotics which may be administered parenterally or internally.

Question 1087

Topic: 1. General Principles & Basic Science

All of the following characterize lateral patellar compression syndrome except:

. Anterior knee pain localized to the patellofemoral joint
. A tight lateral retinaculum
. Subluxation of the patella
. A lateral patella tilt with narrowing of the lateral patella and femoral articular surfaces on the sunrise radiograph
. May be unilateral or bilateral

Correct Answer & Explanation

. Subluxation of the patella

Explanation

By definition, patients with a lateral patellar compression syndrome do not have a subluxation or dislocation of the patella.

Question 1088

Topic: Biomechanics & Biomaterials

Pediatric bone:

. Has a higher modulus of elasticity than adult bone.
. Has lower bending strength than adult bone.
. Has a short plastic phase on the load-deformation curve.
. Has periosteum, which is more prone to tear than adult periosteum.
. Is more mineralized than adult bone

Correct Answer & Explanation

. Has lower bending strength than adult bone.

Explanation

Pediatric bone has less mineral and more vascular channels than adult bone. This gives it a lower bending strength and lower modules of elasticity than adult bone.

Question 1089

Topic: 1. General Principles & Basic Science

Which category of failure of formation anomalies is most often associated with systemic anomalies?

. Radial deficiencies.
. Ulnar deficiencies.
. C entral deficiencies.
. Transverse deficiencies.
. Tibial deficiencies

Correct Answer & Explanation

. Radial deficiencies.

Explanation

Radial deficiencies are often seen in the later association. which may include cardiac,renal,anorectal and tracheoesphogeal abnormalities.

Question 1090

Topic: 1. General Principles & Basic Science

Arthrogryposis multiplex congenita:

. Primarily affects joints, and secondarily the muscles which move them.
. Is more often neuropathic than myopathic.
. Is typically asymmetrical.
. Does not respond to passive joint mobilization.
. Has a natural history of increasing joint range of motion with time

Correct Answer & Explanation

. Primarily affects joints, and secondarily the muscles which move them.

Explanation

Arthrogryposis multiplex congenita is an idiopathic disorder that may be due to a primary deficiency of anterior horn cells. Arthrogryposis multiplex congenita results in lack of muscle development; the joint stiffness is secondary to this. It is usually reasonably symmetrical.

Question 1091

Topic: 1. General Principles & Basic Science
In studying a newly recognized disorder using a large population of affected individuals, geneticists discover that although the disorder often affects siblings, it was rarely, if ever, detected in their ancestors. This disorder most closely follows which pattern of inheritance?
. Autosomal dominant
. Autosomal recessive
. Sex-linked
. Multifactorial
. Anticipation

Correct Answer & Explanation

. Autosomal recessive

Explanation

Autosomal recessive conditions classically show "horizontal" inheritance. Ancestors do not display the gene because they would likely have only one copy of the mutant allele. Only when two carriers reproduce is the phenotype manifest in approximately one-fourth of their offspring. Autosomal dominant inheritance is characterized by vertical transmission. Many generations manifest the trait because it takes only a single copy of a mutant allele to display the phenotype. Sex-linked conditions are often traced back in a family. Normally the males are affected and the females are carriers. Multifactorial conditions are thought to result from the combination of different genes. Although the risk of recurrence in kindred is somewhat greater than the population as a whole, it is still quite low (only a few percent). It is rare for siblings to be affected. Anticipation refers to the phenomenon in which successive generations are likely to display more severe forms of a given disorder. Myotonic dystrophy is a classic example of this phenomenon.

Question 1092

Topic: 1. General Principles & Basic Science

Diseas es caused by enzyme deficiency are commonly inherited by which of the following patterns:

. Autosomal dominant
. Autosomal recessive
. X-linked dominant
. Multifactorial
. Non-mendelian

Correct Answer & Explanation

. Autosomal recessive

Explanation

Two copies of a mutant allele are required to reduce enzyme function to levels that cause clinical impairment. Enzyme defects are rarely inherited by an autosomal dominant pattern because even half of the normal activity of most enzymes is adequate to maintain normal function. Enzyme defects are rarely inherited in an X-linked dominant pattern because one copy of a mutant allele is usually sufficient. Multifactorial inheritance refers to the interaction of multiple, or different genes, to produce a disorder. Enzyme deficiencies are typically the result of a defect in a single gene. Because enzymes are typically coded by a single gene, they follow mendelian patterns.

Question 1093

Topic: 1. General Principles & Basic Science

Which of the following descriptions is more characteristic of tuberculosis than of pyogenic spondylitis:

. Disc space is narrowed before significant bony changes occur.
. Involvement of multiple contiguous levels is uncommon.
. Bony erosions seen on computerized tomography are usually small and focal.
. Vertebral destruction exceeds disc destruction.
. Magnetic resonance imaging rarely shows significant soft tissue swelling.

Correct Answer & Explanation

. Vertebral destruction exceeds disc destruction.

Explanation

Vertebral destruction exceeds disc destruction in tuberculosis. Bony changes occur earlier in tuberculosis than in pyogenic spondylitis. Involvement of multiple contiguous levels is more common in tuberculosis than pyogenic spondylitis. Bony erosions seen on computerized tomography are large in tuberclosis and small in pyogenic spondylitis. Magnetic resonance imaging often shows significant soft tissue involvement in both disorders.

Question 1094

Topic: 1. General Principles & Basic Science

Which of the following statements is true of demineralized bone matrix:

. Demineralized bone matrix is weakly osteoinductive.
. Demineralized bone matrix is consistent between forms and different sterilization methods.
. Demineralized bone matrix is not osteoconductive.
. Demineralized bone matrix is osteogenic.
. Demineralized bone matrix is strongly osteoinductive.

Correct Answer & Explanation

. Demineralized bone matrix is weakly osteoinductive.

Explanation

Demineralized bone matrix is weakly osteoinductive. The term osteogenic refers to direct transmittal of cells capable of making bone. Demineralized bone matrix is not osteogenic. Demineralized bone matrix varies in efficacy between different forms and different methods of sterilization. The term osteoconduction refers to provision of a favorable scaffold and environment for bone formation. Demineralized bone matrix is osteoconductive.

Question 1095

Topic: 1. General Principles & Basic Science

Which of the following is not a specific feature in making the diagnosis of a dystrophic curve in neurofibromatosis 1:

. Penciling of the ribs
. Scalloping of the vertebrae
. Widening of the foramen
. Thinning of the transverse processes
. Vertebral rotation

Correct Answer & Explanation

. Vertebral rotation

Explanation

Vertebral rotation is not a specific characteristic of dystrophic curves. Rotation is more pronounced in dystrophic curves than in nondystrophic curves, but it is commonly present in both types of curves. Penciling of the ribs is one of the features specific for dystrophic curves in neurofibromatosis 1. Scalloping of the vertebrae anteriorly and posteriorly is characteristic of dystrophic curves in neurofibromatosis 1. Widening of the neural foramen is specific for dystrophic curves in neurofibromatosis 1. Widening of the neural foramen is due to tumorous masses passing through the foramen. Thinning of the transverse process is a characteristic of dystrophic curves in neurofibromatosis 1.

Question 1096

Topic: 1. General Principles & Basic Science

A 28-year-old man sustains a complete laceration of the flexor digitorum profundus (FDP) in zone II. Following a robust multi-strand surgical repair, which rehabilitation protocol is most appropriate to minimize tendon adhesions?

. Strict immobilization for 6 weeks
. Early active extension and passive flexion
. Immediate full active range of motion
. Passive extension and active flexion
. Dynamic splinting locked in full extension

Correct Answer & Explanation

. Early active extension and passive flexion

Explanation

Early active extension and passive flexion (e.g., the modified Kleinert or Duran protocol) is the gold standard after zone II flexor tendon repairs. It stimulates intrinsic healing and excursion to prevent adhesions while preventing excessive tension that could rupture the repair.

Question 1097

Topic: 1. General Principles & Basic Science
A 22-year-old rugby player grabs an opponent's jersey and feels a pop in his ring finger. He cannot actively flex the distal interphalangeal (DIP) joint. Ultrasound shows the flexor digitorum profundus (FDP) tendon retracted into the palm. What is the classification and ideal timing for surgery?
. Type I, requiring surgery within 7 to 10 days
. Type II, requiring surgery within 3 to 4 weeks
. Type III, requiring surgery within 3 months
. Type I, observation only
. Type IV, requiring primary distal interphalangeal joint fusion

Correct Answer & Explanation

. Type I, requiring surgery within 7 to 10 days

Explanation

This is a Leddy and Packer Type I FDP avulsion, characterized by tendon retraction into the palm and complete disruption of the vincula. Surgery must be performed within 7 to 10 days to prevent permanent tendon retraction and ischemic necrosis.

Question 1098

Topic: Biomechanics & Biomaterials

When analyzing the biomechanical properties of a tendon, it is noted that applying a constant load over a prolonged period causes the tendon to gradually elongate. This viscoelastic phenomenon is best described as:

. Stress relaxation
. Creep
. Hysteresis
. Fatigue failure
. Isotropic behavior

Correct Answer & Explanation

. Creep

Explanation

Creep is the time-dependent deformation or elongation of a viscoelastic material when it is subjected to a constant load. In contrast, stress relaxation is the decrease in internal stress over time when the material is held at a constant length or strain.

Question 1099

Topic: Biology, Genetics & Bone Healing

A 30-year-old woman presents with a lytic epiphyseal lesion of the distal femur. Biopsy confirms a Giant Cell Tumor (GCT) of bone. Prior to surgical curettage, she is given neoadjuvant denosumab to consolidate the tumor margins. What is the mechanism of action of this medication?

. Inhibition of vascular endothelial growth factor (VEGF)
. Monoclonal antibody that binds to and inhibits RANK ligand (RANKL)
. Direct alkylation of DNA leading to cell apoptosis
. Inhibition of matrix metalloproteinases
. Stimulation of osteoprotegerin (OPG) production

Correct Answer & Explanation

. Monoclonal antibody that binds to and inhibits RANK ligand (RANKL)

Explanation

Denosumab is a human monoclonal antibody that binds directly to RANK ligand (RANKL). This prevents the activation of the RANK receptor on osteoclast precursors, which dramatically reduces the characteristic osteoclast-like giant cells in GCTs.

Question 1100

Topic: Biology, Genetics & Bone Healing

A 5-year-old child presents with frequent bone fractures, cranial nerve palsies, and diffuse osteosclerosis on radiographs. A genetic defect impairing the acidification of the osteoclast resorption pit is suspected. Which of the following enzymes or proteins is most likely deficient?

. Alkaline phosphatase
. Cathepsin K
. Carbonic anhydrase II
. Matrix metalloproteinase-9 (MMP-9)
. Tartrate-resistant acid phosphatase (TRAP)

Correct Answer & Explanation

. Carbonic anhydrase II

Explanation

Osteopetrosis is caused by defective osteoclast function. A deficiency in Carbonic anhydrase II impairs the osteoclast's ability to secrete protons and acidify the resorption pit, which is absolutely necessary for breaking down the inorganic bone matrix.

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