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2. Trauma MCQs

Practice Set 456 of 640

This practice set contains high-yield board review questions covering key concepts in 2. Trauma. Each clinical scenario is designed to test your diagnostic and management skills relevant to this subspecialty.

Question 9101

Topic: 2. Trauma

In the context of distraction osteogenesis, what does the Bone Healing Index (BHI) objectively measure?

. The total days in the frame divided by the length of regenerate in centimeters
. The cortical density ratio of the regenerate compared to normal diaphysis
. The millimeters of distraction achieved per day
. The maximum torque the regenerate can withstand before fracture
. The total number of days of latency required before distraction

Correct Answer & Explanation

. The total days in the frame divided by the length of regenerate in centimeters

Explanation

The Bone Healing Index (BHI) is defined as the total number of days an external fixator is required for full consolidation divided by the total amount of length gained in centimeters (days/cm). A normal BHI is typically 30-40 days/cm in children.

Question 9102

Topic: Lower Extremity Trauma

According to the White-Menelaus rule of thumb for estimating remaining growth, what is the expected annual longitudinal growth from the distal femoral and proximal tibial physes, respectively?

. 9 mm and 6 mm
. 10 mm and 8 mm
. 6 mm and 9 mm
. 12 mm and 6 mm
. 8 mm and 10 mm

Correct Answer & Explanation

. 9 mm and 6 mm

Explanation

The White-Menelaus method estimates growth as 3/8 inch (approx. 9 mm) per year for the distal femur and 1/4 inch (approx. 6 mm) per year for the proximal tibia. This is universally tested as 9 mm and 6 mm in board examinations.

Question 9103

Topic: Lower Extremity Trauma

A 45-year-old male presents with severe varus gonarthrosis. Standing long leg radiographs reveal a mechanical axis deviation (MAD) of 45 mm medial to the center of the knee. The mechanical lateral distal femoral angle (mLDFA) is 88 degrees and the medial proximal tibial angle (MPTA) is 80 degrees. The joint line convergence angle (JLCA) is 1 degree. What is the primary source of the varus deformity and the most appropriate site for osteotomy?

. Distal femur; requires a medial closing wedge osteotomy
. Proximal tibia; requires a lateral closing wedge osteotomy
. Proximal tibia; requires a medial opening wedge osteotomy
. Knee joint; requires isolated medial collateral ligament balancing
. Both femur and tibia; requires a double-level osteotomy

Correct Answer & Explanation

. Proximal tibia; requires a medial opening wedge osteotomy

Explanation

The normal mLDFA is approximately 87 degrees (range 85-90), while the normal MPTA is also 87 degrees. An MPTA of 80 degrees indicates that proximal tibial varus is the primary source of the deformity, making a proximal tibial osteotomy (such as a medial opening wedge) the corrective procedure of choice.

Question 9104

Topic: 2. Trauma

A 25-year-old male is undergoing tibial lengthening via distraction osteogenesis. The distraction rate was conservatively set at 0.5 mm per day (0.25 mm twice daily). During the distraction phase, radiographs at 3 weeks show dense, bridging trabeculae across the entire regenerate gap. What is the most likely complication of this protocol, and what is the appropriate initial intervention?

. Hypertrophic nonunion; exchange to an intramedullary nail
. Premature consolidation; increase the distraction rate
. Atrophic nonunion; decrease the distraction rate
. Pin tract infection; prescribe oral culture-directed antibiotics
. Joint contracture; initiate aggressive physical therapy

Correct Answer & Explanation

. Premature consolidation; increase the distraction rate

Explanation

A distraction rate of 0.5 mm per day is generally too slow for healthy adults, which strongly predisposes the regenerate bone to premature consolidation. The appropriate management is to increase the distraction rate to the standard 1 mm per day (divided in 3-4 increments) to overcome the consolidating callus.

Question 9105

Topic: Lower Extremity Trauma

A 12-year-old boy presents with a 2.5 cm leg length discrepancy due to a prior left femoral shaft fracture. His skeletal age is identical to his chronological age. Based on the Menelaus approximation of the Green-Anderson charts, and assuming skeletal maturity at age 16, which intervention will most accurately achieve limb length equality at maturity?

. Percutaneous epiphysiodesis of the right distal femur only
. Percutaneous epiphysiodesis of the right proximal tibia only
. Percutaneous epiphysiodesis of the right distal femur and right proximal tibia
. Left femoral lengthening over an intramedullary nail
. Epiphysiodesis of the right proximal tibia and right distal fibula

Correct Answer & Explanation

. Percutaneous epiphysiodesis of the right proximal tibia only

Explanation

Using the Menelaus method, the proximal tibia grows approximately 0.6 cm (1/4 inch) per year. With 4 years of growth remaining (age 16 minus age 12), a proximal tibial epiphysiodesis will yield approximately 2.4 cm of relative shortening, neatly correcting the 2.5 cm discrepancy.

Question 9106

Topic: Lower Extremity Trauma

A 16-year-old male presents with lateral mechanical axis deviation (MAD) of the lower extremity. Standing alignment radiographs reveal a mechanical lateral distal femoral angle (mLDFA) of 81° and a medial proximal tibial angle (MPTA) of 87°. The joint line convergence angle (JLCA) is 1°. What is the primary anatomic source of his malalignment?

. Distal femur valgus deformity
. Proximal tibia valgus deformity
. Intra-articular knee joint laxity
. Proximal femur varus deformity
. Distal femur varus deformity

Correct Answer & Explanation

. Distal femur valgus deformity

Explanation

Normal mLDFA is approximately 88° (range 85°-90°) and normal MPTA is 87° (range 85°-90°). An mLDFA of 81° is abnormally low, indicating a valgus deformity originating in the distal femur.

Question 9107

Topic: 2. Trauma

A 15-year-old male undergoes gradual correction of a severe proximal tibial valgus and procurvatum deformity using a circular hexapod frame. On postoperative day 14, he develops weakness in ankle dorsiflexion and decreased sensation in the first web space. Which nerve is most likely compromised?

. Superficial peroneal nerve
. Deep peroneal nerve
. Sural nerve
. Tibial nerve
. Saphenous nerve

Correct Answer & Explanation

. Deep peroneal nerve

Explanation

The deep peroneal nerve is highly susceptible to stretch injury or anterior compartment syndrome during proximal tibial lengthening and valgus correction. Compromise classically presents with foot drop and isolated sensory loss in the first dorsal web space.

Question 9108

Topic: 2. Trauma

A 10-year-old girl (skeletal age 10) presents with a 2.5 cm leg length discrepancy (LLD) secondary to a prior left distal femur fracture. Using the Menelaus method, at what age should a right distal femoral epiphysiodesis be performed to achieve limb length equality at skeletal maturity?

. 10.5 years
. 11.0 years
. 11.5 years
. 12.0 years
. 12.5 years

Correct Answer & Explanation

. 11.5 years

Explanation

The Menelaus method estimates the distal femur grows 1 cm per year and girls reach skeletal maturity at age 14. To correct a 2.5 cm discrepancy, the procedure should be performed 2.5 years prior to skeletal maturity (14 - 2.5 = 11.5 years).

Question 9109

Topic: Pelvic & Acetabular Trauma

A 45-year-old female with a history of untreated developmental dysplasia of the hip (DDH) presents for total hip arthroplasty. Preoperative radiographs demonstrate a high hip dislocation (Crowe Type IV). Which of the following anatomic abnormalities is most consistently encountered during reconstruction of this patient's hip?

. The true acetabulum is located superior and lateral to the false acetabulum.
. The femoral neck exhibits excessive retroversion.
. The femoral medullary canal is unusually wide and capacious.
. The true acetabulum is located inferior and medial to the false acetabulum, and the femur exhibits excessive anteversion.
. The sciatic nerve is shortened and at low risk for stretch injury during reduction.

Correct Answer & Explanation

. The true acetabulum is located inferior and medial to the false acetabulum, and the femur exhibits excessive anteversion.

Explanation

Correct Answer: The true acetabulum is located inferior and medial to the false acetabulum, and the femur exhibits excessive anteversion.In severe developmental dysplasia of the hip (Crowe Type IV), the femoral head is completely dislocated from the true acetabulum and often articulates with a false acetabulum (neoacetabulum) on the ilium. The true acetabulum is located inferior and medial to this false acetabulum and is typically shallow, deficient anteriorly and superiorly, and filled with fibrofatty tissue (pulvinar). On the femoral side, the anatomy is characterized by a narrow (stovepipe) medullary canal, excessive femoral neck anteversion, a short femoral neck, and a posteriorly displaced greater trochanter. The sciatic nerve is often shortened due to the proximal migration of the femur and is at high risk for stretch injury when the hip is brought down to the true acetabulum, often necessitating a femoral shortening osteotomy.

Question 9110

Topic: 2. Trauma

A 78-year-old female presents to the emergency department after a mechanical fall. Radiographs demonstrate a displaced spiral fracture of the proximal femur around a cemented polished taper-slip THA stem. The fracture extends to the distal tip of the stem. The stem has subsided 10 mm compared to previous films, but the proximal femoral bone stock remains adequate. What is the most appropriate surgical treatment?

. ORIF with locking plate and cerclage cables
. Revision to a long uncemented fully porous-coated or fluted tapered stem
. Impaction bone grafting and cement-in-cement revision
. Revision to a proximal femoral replacement (megaprosthesis)
. Nonoperative management in a hip spica cast

Correct Answer & Explanation

. Revision to a long uncemented fully porous-coated or fluted tapered stem

Explanation

This is a Vancouver B2 periprosthetic fracture (loose stem, adequate bone stock). The standard of care is revision of the femoral component using a long uncemented extensively porous-coated or fluted tapered stem that bypasses the fracture by at least two cortical diameters.

Question 9111

Topic: Pelvic & Acetabular Trauma

A 6-year-old non-ambulatory girl with Spinal Muscular Atrophy Type II is noted to have progressive right hip subluxation on annual surveillance radiographs. The hip is currently subluxated 40% but remains reducible. The primary biomechanical driver for this paralytic hip subluxation is an imbalance between which of the following muscle groups?

. Stronger hip abductors overpowering weaker hip adductors.
. Stronger hip extensors overpowering weaker hip flexors.
. Stronger hip flexors and adductors overpowering weaker hip extensors and abductors.
. Global spasticity of all pelvic girdle musculature.
. Primary acetabular dysplasia independent of muscle forces.

Correct Answer & Explanation

. Stronger hip flexors and adductors overpowering weaker hip extensors and abductors.

Explanation

Correct Answer: C (Stronger hip flexors and adductors overpowering weaker hip extensors and abductors.)Hip instability is a common orthopedic complication in non-ambulatory patients with SMA. It is a paralytic dislocation driven by a specific pattern of muscle weakness. In SMA, the hip extensors (gluteus maximus) and hip abductors (gluteus medius/minimus) weaken earlier and more severely than the hip flexors (iliopsoas) and hip adductors. This muscle imbalance creates a deforming force that pulls the proximal femur into flexion and adduction, gradually levering the femoral head posterolaterally out of the acetabulum. SMA is a lower motor neuron disease, so spasticity (an upper motor neuron sign) is absent.

Question 9112

Topic: Pelvic & Acetabular Trauma

A 6-year-old girl with Spinal Muscular Atrophy Type II is noted to have progressive right hip subluxation on routine surveillance radiographs. She is non-ambulatory and uses a custom-molded wheelchair. The primary driver of this hip instability is:

. Primary acetabular dysplasia secondary to a genetic collagen defect.
. Avascular necrosis of the femoral head due to recurrent microtrauma.
. Muscle imbalance characterized by relatively strong hip flexors and adductors overpowering weak abductors and extensors.
. Severe spasticity of the hip adductor musculature.
. Ligamentous laxity associated with a concurrent connective tissue disorder.

Correct Answer & Explanation

. Muscle imbalance characterized by relatively strong hip flexors and adductors overpowering weak abductors and extensors.

Explanation

Correct Answer: CHip subluxation and dislocation are highly prevalent in non-ambulatory patients with SMA. The primary etiology is a paralytic muscle imbalance around the hip joint. In SMA, the hip flexors (iliopsoas) and adductors typically retain more strength relative to the profoundly weak hip abductors (gluteus medius/minimus) and extensors (gluteus maximus). Over time, this unopposed flexion and adduction force progressively drives the femoral head laterally and superiorly out of the acetabulum. Because SMA is a lower motor neuron disease, spasticity (an upper motor neuron sign) is absent.

Question 9113

Topic: 2. Trauma

A 12-year-old girl with Osteogenesis Imperfecta Type IV presents to the emergency department with acute posterior elbow pain and an inability to actively extend her elbow against gravity after a minor fall onto a flexed elbow. Radiographs reveal a displaced fracture. Given her underlying diagnosis, which of the following fracture patterns is highly characteristic and frequently bilateral in this patient population?

. Supracondylar humerus fracture
. Radial neck fracture
. Olecranon apophyseal avulsion fracture
. Lateral condyle humerus fracture
. Coronoid process fracture

Correct Answer & Explanation

. Olecranon apophyseal avulsion fracture

Explanation

Correct Answer: COlecranon apophyseal avulsion fractures are a highly characteristic and classic fracture pattern seen in patients with Osteogenesis Imperfecta. Because the bone is inherently weak and osteopenic, the sudden, forceful eccentric contraction of the triceps muscle during a fall or sudden deceleration can easily avulse the olecranon apophysis. This injury is frequently bilateral in OI patients, either occurring simultaneously or sequentially. While OI patients can sustain any fracture, the olecranon avulsion is a known hallmark of the disease's biomechanical failure at the tendon-bone interface. Treatment often requires tension band wiring or heavy suture fixation, taking care not to crush the fragile bone.

Question 9114

Topic: 2. Trauma

A 7-year-old boy with SMA Type 2 requires urgent surgical fixation of a displaced femur fracture. During anesthetic induction, which of the following neuromuscular blocking agents is strictly contraindicated due to the risk of a lethal complication?

. Rocuronium
. Vecuronium
. Succinylcholine
. Cisatracurium
. Pancuronium

Correct Answer & Explanation

. Succinylcholine

Explanation

Succinylcholine is contraindicated in patients with SMA. The denervation of muscle leads to an up-regulation of extrajunctional acetylcholine receptors, which can cause massive potassium release and fatal hyperkalemia when depolarized.

Question 9115

Topic: 2. Trauma
A 7-year-old boy presents with blue sclerae, normal stature, and a history of three low-energy long bone fractures. Genetic testing reveals a premature stop codon in the COL1A1 gene. Which of the following best describes the underlying collagen defect in this patient?
. Qualitative defect with production of structurally abnormal type I collagen.
. Quantitative defect resulting in a decreased amount of structurally normal type I collagen.
. Defect in the conversion of procollagen to collagen via N-proteinase.
. Mutation in the cartilage oligomeric matrix protein (COMP) gene.
. Defect in type II collagen synthesis.

Correct Answer & Explanation

. Quantitative defect resulting in a decreased amount of structurally normal type I collagen.

Explanation

The patient has OI Type I, classically caused by a null mutation (e.g., premature stop codon) in COL1A1 leading to haploinsufficiency. This results in a quantitative defect (decreased amount of normal collagen), unlike Types II, III, and IV which typically involve qualitative defects.

Question 9116

Topic: 2. Trauma
A 5-year-old boy with Osteogenesis Imperfecta Type III presents with severe anterolateral bowing of bilateral femurs and a history of recurrent fractures. He is planned for multiple osteotomies and intramedullary fixation. Which of the following is the primary advantage of using a single-entry telescopic rod over a traditional solid intramedullary nail?
. Decreased risk of intraoperative fat embolism.
. Accommodation of longitudinal bone growth without the need for frequent revisions.
. Enhanced rotational stability due to a locking proximal mechanism.
. Superior resistance to bending forces in the diaphysis.
. Stimulation of endosteal bone formation via intramedullary reaming.

Correct Answer & Explanation

. Accommodation of longitudinal bone growth without the need for frequent revisions.

Explanation

Telescopic rods (e.g., Fassier-Duval) are designed to elongate as the child grows, significantly reducing the frequency of revision surgeries for outgrown implants. Single-entry systems also minimize joint violation compared to older double-entry designs.

Question 9117

Topic: 2. Trauma

A patient with scleroderma presents with severe, refractory digital ischemia secondary to Raynaud's phenomenon, which has not responded to calcium channel blockers and PDE-5 inhibitors. What surgical intervention may be considered to improve digital perfusion?

. Sympathectomy of the superficial palmar arch
. Ligation of the ulnar artery
. Amputation at the metacarpophalangeal joint
. Fasciotomy of the forearm compartments
. Tendon transfer to restore intrinsic function

Correct Answer & Explanation

. Sympathectomy of the superficial palmar arch

Explanation

For refractory digital ischemia in scleroderma, digital sympathectomy involving stripping adventitia from the superficial palmar arch and digital arteries can relieve vasospasm. This helps heal ulcers and restore perfusion.

Question 9118

Topic: 2. Trauma

A 9-year-old boy presents with a pathologic fracture of the proximal humerus following a minor fall. Radiographs show a centrally located, completely lytic lesion in the metaphysis that does not breach the cortex, with a small bony fragment settled at the bottom of the cyst. What is the most appropriate initial management after fracture healing?

. En bloc resection and allograft reconstruction
. Curettage and bone grafting
. Observation or intra-lesional corticosteroid injection
. Preoperative chemotherapy followed by wide excision
. Prophylactic internal fixation with flexible nails

Correct Answer & Explanation

. Observation or intra-lesional corticosteroid injection

Explanation

The presentation and the "fallen leaf" sign are classic for a unicameral bone cyst (UBC). First-line treatment for an active UBC after fracture healing typically involves observation or minimally invasive options like corticosteroid injections.

Question 9119

Topic: 2. Trauma

A 9-year-old boy sustains a pathological fracture through a central, lytic lesion in the proximal humerus after throwing a baseball. Radiographs demonstrate the 'fallen leaf' sign. What is the recommended initial management if the cyst remains active and expansile after the fracture heals?

. Wide surgical resection
. En bloc resection and structural allograft
. Intralesional injection with corticosteroids or bone marrow aspirate
. Radiation therapy
. Observation alone despite high risk of refracture

Correct Answer & Explanation

. Intralesional injection with corticosteroids or bone marrow aspirate

Explanation

The 'fallen leaf' sign is pathognomonic for a unicameral bone cyst (UBC). If the cyst remains active and prone to refracture after initial healing, intralesional aspiration and injection (corticosteroids, BMA, or DBM) is the first-line surgical treatment.

Question 9120

Topic: 2. Trauma

An 8-year-old boy presents to the emergency department after a minor fall. Radiographs show a fracture through a central, radiolucent, cystic lesion in the proximal humerus metaphysis. A cortical fragment is seen resting at the dependent portion of the cyst ('fallen leaf' sign). What is the most appropriate initial management?

. Immediate intralesional curettage and bone grafting
. Sling immobilization to allow the fracture to heal
. Wide surgical resection of the proximal humerus
. Immediate intralesional corticosteroid injection
. External fixation

Correct Answer & Explanation

. Sling immobilization to allow the fracture to heal

Explanation

The 'fallen leaf' sign is pathognomonic for a Unicameral Bone Cyst (UBC). When a fracture occurs through a UBC, the initial management is immobilization to allow the fracture to heal; the cyst may occasionally heal and obliterate itself as the fracture remodeling occurs.

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