Multiple Choice Questions

Basic Sciences

Please use the comments section at the bottom of the page if you have any query or feedback about any of the questions.

38. A foot is maximally dorsiflexed during this point of the gait cycle:

A) Midswing
B) Midstance
C) Toe off
D) Heelstrike
E) First one-third of stance

Correct Answer: B

During gait, a foot is dorsiflexed during midswing and foot flat. During midswing, the anterior tibial muscle maintains the foot in a dorsiflexed position to facilitate a smooth heelstrike. This is an active dorsiflexion of the foot and ankle. The maximum dorsiflexion of the foot, however, is passive and occurs as the leg moves forward over the foot during foot flat at midstance.

Author: Rajesh Bahadur Lakhey

 

37 The protein neurofibromin normally acts in which of the following ways:

A) Inhibits fibroblast growth factor 
B) Promotes proteoglycan assembly
C) Down regulates Ras protein 
D) Causes nerve cells to divide
E) Promotes tumor formation

Correct Answer: C

If defective, neurofibromin is the protein that causes neurofibromatosis. Neurofibroma is coded on chromosome 17, and it acts as a tumor suppressor by downregulating Ras protein, which enhances cell growth and proliferation

Author: Fouad Chaudery


36. Which of the following mechanisms of biphosphonate action occurs when a biphosphonate is used to treat osteoporosis:

A) Increasing calcium absorption in the intestines 
B) Decreasing urinary excretion of calcium 
C) Stimulating osteoblast precursors 
D) Binding to hydroxyapatite crystals 
E) Increasing phosphate reabsorption in the kidney 

Correct Answer: D

Biphosphonates are effective in the treatment of osteoporosis because they bind to the hydroxyapatite crystals and inhibit crystal resorption.

Other effects of biphosphonates include:

Reducing production of proteins and lysosomal enzymes by osteoclasts
Reducing the formation of new bone remodeling units
Inducing osteoclast cell death
Reducing the formation of new osteoclasts After 1 year of treatment

Author: Fouad Chaudhry

 

35. Osteoclasts have receptors for which of the following:

A) 1,25 dihydroxyvitamin D3 
B) Parathyroid hormone 
C) Osteoprotegerin 
D) Receptor activator of nuclear factor –kB 
E) Calcitonin 

Correct Answer: E

Osteoclasts have receptors for calcitonin. Calcitonin causes osteoclasts to shrink in size and reduces their ability to resorb bone

Author: Fouad Chaudhry

 

34. Parathyroid hormone inhibits the production of:

A) Osteoprotegerin 
B) 1,25 dihydroxyvitamin D3 production 
C) Interleukin-6 
D) Kidney 1 alpha-hydroxylase 
E) Receptor activator of nuclear factor –kB ligand (RANKL) 

Correct Answer: A

Parathyroid hormone inhibits the production of osteoprotegerin. Osteoprotegerin is a decoy inhibitor of the receptor activator of nuclear factor –kB. Osteoprotegerin inhibits osteoclast activation.

Author: Fouad Chaudhry

 
 

 

33. Which of the following proteins or hormones assists in the transport of calcium in the kidney against chemical and electrical gradients:

A) Calcitonin 
B) Calbindin 
C) Osteoprotegerin 
D) Parathyroid hormone 
E) Vitamin D3 

Correct Answer: B

Calbindin, a vitamin D dependent and calcium binding protein, assists in the transport of calcium against chemical and electrical gradients. Most regulation calcium resorption in the kidney occurs in the distal convoluted segment. 

Author: Fouad Chaudhry

 
 

 

32. Osteoprotegerin (OPG) has which of the following functions or effects:

A) Inhibits osteoclast apoptosis 
B) Inhibits osteoclast formation 
C) Activates osteoclast precursors 
D) Induces hypercalcemia 
E) Binds to receptor activator of nuclear factor –kB ligand (RANKL) 

Correct Answer: E

The activation of osteoclasts is a complex process. Surface receptors on the osteoclast precursor cells are called RANK. Receptor activator of nuclear factor –kB ligand (RANKL) is expressed on the surface of osteoblasts/stromal cells. The RANKL proteins leave the osteoblast and attach to the RANK receptor on the osteoclast precursor. Macrophage colony stimulating factor then facilitates the production of active osteoclasts from the osteoclast precursor. Osteoprotegerin (OPG) is an inhibitor that is produced on the cell surface of hematopoietic precursor cells and mature osteoclasts. OPG binds to RANK receptor to inhibit the activation of osteoclasts.

OPG

  • Soluble decoy receptor for RANKL
  • Blocks osteoclast formation
  • Reduces hypercalcemia
  • Overexpression induces osteopetrosis
  • Loss of expression induces osteoporosis
  • Prevents calcification of large arteries

Author: Fouad Chaudhry

 
 

 

31. Which of the following proteins binds to osteoclast precursor cells and positively effects their final differentiation into osteoclasts:

A) Receptor activator of nuclear factor-kappa B (RANK) 
B) Osteoprotegerin 
C) Bone morphogenetic protein 7 
D) Core binding factor alpha 1 (Cbfa1) 
D) Parathyroid hormone related protein (PTHrP) 

Correct Answer: A

Four proteins that regulate osteoclast activation have been discovered:

  • Receptor activator of nuclear factor-kappa B (RANK) binds to a receptor on osteoclast precursor cells and positively effects their final differentiation into osteoclasts.
  • Osteoprotegerin is a soluble decoy receptor that resembles RANK and inhibits osteoclasts.
  • Tumor necrosis factor-related activation induced cytokine (TRANCE)
  • Osteoclast differentiation factor

Author: Fouad Chaudhry

 
 

 

30. Which of the following musculoskeletal complications may occur in patients taking fluoroquinolones, such as ciprofloxacin: 

A) Osteomalacia 
B) Osteoporosis 
C) Joint laxity 
D) Tendon ruptures 
E) Parethesias 

Correct Answer: D

Fluoroquinolones may cause side effects to the musculoskeletal system that include arthralgias, chondrotoxicity, and tendinopathy.

Achilles tendonitis and rupture is the most common tendinopathy associated with fluoroquinolone use (usually ciprofloxacin). Fifty percent of cases are bilateral. The interval to rupture is between 2 and 60 days. Patients at increased risk include:

  • Patients older than 60 years of age

  • Patients with diabetes

  • Patients with impaired renal function

  • Patients who partake in strenuous sports activities

Author: Fouad Chaudhry

 
 

 

29. The skin over the umbilicus is innervated by which of the following levels:

A) T2
B) T4
C) T7
D) T10
E) T12

Correct Answer: D

T4

Nipple line

T7

Xiphoid process

T10

Umbilicus

T12

Groin

Author: Fouad Chaudhry

 
 

 

28. The extensor hallucis longus muscle is innervated by which of the following nerve roots:

A) L1
B) L2
C) L3
D) L4
E) L5

Correct Answer: E

Remember that the L5 nerve root innervates the following muscles:
• Extensor hallucis longus
• Extensor digitorum longus and brevis
• Gluteus medius

Author: Fouad Chaudhry

 
 

 

27. The skin of the proximal one-third of the anterior thigh just distal to the inguinal ligament is innervated by which of the following sensory segmental levels: 

A) T12
B) L1
C) L2
D) L3
E) L4

Correct Answer: B

L1

Thigh, proximal third, and anterior

L2

Thigh, middle, and anterior

L3

Thigh, distal third, and anterior

Author: Fouad Chaudhry

 

 

26. The skin on the medial aspect of the leg and great toe is innervated by which of the following nerve roots: 

A) L2
B) L3
C) L4
D) L5
E) S1

Correct Answer: C

Explanation:  Remember:
• L4 Medial aspect of the leg, foot, and great toe
• L5 Lateral aspect of the leg and toes 2 to 4
• S1 Lateral aspect of the fifth toe 

Author: Fouad Chaudhry

 

 

25. Which of the following statements is true concerning the vascularity at a fracture site

A) Periosteal blood vessels are capable of supplying the endosteal region. 
B) Fracture site blood flow peaks at 2 weeks. 
C) Reamed intramedullary rods do not significantly interrupt endosteal blood supply. 
D) In animal studies, blood flow is greater at 120 days in plated vs. rodded tibias. 
E) In animal studies, blood flow is greater at 42 days in rodded vs. plated tibias. 

Correct Answer: B

In the normal long bone, the periosteal vessels supply the outer one-third of the cortex. The nutrient artery enters at the diaphysis of a long bone and has ascending and descending vessels that supply the inner two-thirds of the cortex.

Important points to remember:

  • The periosteal blood supply cannot supply the inner two-thirds of the cortex even if the endosteal blood supply has been interrupted, as in intramedullary reaming.

  • Blood flow markedly drops at the fracture site at the time of the fracture and peaks at 2 weeks.

  • Intramedullary reamed rods destroy the endosteal blood supply. In dog experiments, the blood supply is reconstituted to normal in 120 days.

  • In dog experiments, the blood supply is decreased in both plated and rodded tibias at 42 and 90 days. The decrease is greater in the rodded tibias.

  • The oxygen tension is low in the fracture hematoma and in the newly formed cartilage and bone. The oxygen tension is highest in the fibrous tissue. The hypoxic state favors cartilage formation.

Author: Fouad Chaudhry

 

24. A 25-year-old soccer player sustained a closed tibia fracture when his planted leg was struck by another player. Which of the following would be the most common fracture pattern and mechanism:

A) Short spiral fracture — torsion 
B) Oblique fracture — uneven bending 
C) Transverse fracture — pure bending 
D) Oblique fracture with a butterfly fragment — bending and compression 
E) Segmental fracture — four-point bending 

Correct Answer: C

A transverse fracture is secondary to a pure bending force.

The other patterns included:

  • Oblique fracture — uneven bending: This type of injury typically occurs following motorcycle accidents when the tibia is subjected to uneven bending forces.

  • Segmental fracture — four-point bending: This injury most commonly follows a high-energy injury, such as a pedestrian being struck by a car bumper.

  • Oblique fracture with a butterfly fragment — bending and compression: This is a common fracture that occurs with low- and high-speed injuries. These fractures may occur from car bumpers and motorcycles.

  • Short spiral fracture — torsion: This mechanism is usually from a low velocity skiing injury.

 

Author: Fouad Chaudhry

 

23. The net effect of 1,25 dihydroxyvitamin D3 on the calcium and phosphate concentration of the extracellular fluid and serum is: 

A) Increased calcium, increased phosphate 
B) Increased calcium, decreased phosphate 
C) Decreased calcium, decreased phosphate 
D) Increased calcium, no effect on phosphate 
E) Transient decrease in serum calcium 

Correct Answer: A

Parathyroid hormone, the active form of vitamin D (1,25 dihydroxyvitamin D), and calcitonin each have a net effect on calcium and phosphorus concentrations in extracellular fluid and serum:

Net Effect

Parathyroid hormone

Increased serum calcium
Decreased serum phosphate

Vitamin D3 (1,25 dihydroxyvitamin D)

Increased serum calcium
Increased serum phosphate

Calcitonin

Decreased serum calcium
(transient)

 

Author: Fouad Chaudhry

 

22. Which of the following serum levels is the best indicator of body stores of Vitamin D3:

A) 7-dehydrocholesterol 
B) 1,25 dihydroxyvitamin D3 
c) 25 hydroxyvitamin D3 
D) 24,25 dihydroxyvitamin D3 
E) Parathyroid hormone levels 

Correct Answer: C

A serum 25 hydroxyvitamin D3 level is the best indicator of body stores of vitamin D3. Remember that 1,25 dihydroxyvitamin D3 is the active metabolite and 24,25 dihydroxyvitamin D3 is the inactive form.

Author: Fouad Chaudhry

 

21. Which of the following cells have receptors for parathyroid hormone:

A) Osteoclasts 
B) Osteoblasts 
C) Lymphocytes 
D) Mast cells 
E) Fibroblasts 

Correct Answer: B

Parathyroid hormone (PTH) mediates bone resorption by stimulation of PTH receptors on the osteoblasts. Osteoclasts do not have receptors for PTH.

Author: Fouad Chaudhry

 

20. Which of the following areas of the osteoclast is responsible for attachment to the bone surface prior to the bone resorption process: 

A) Golgi apparatus 
B) Ribosome 
C) Clear zone 
D) Ruffled border 
E) Secretory vesicles 

Correct Answer: D

Active osteoclasts resorb the mineral and organic matrix of bone. Active osteoclasts also attach the cell to exposed bone matrix. When osteoclasts are studied with an electron microscope, there are two prominent findings — a ruffled border and a clear zone. In the clear zone, the osteoclast seals off the area of bone to be resorbed and attaches to the bone surface through a receptor-mediated process with the assistance of proteins called integrins. The ruffled border is an area found in the infoldings of the cell membrane. 

At the area of the ruffled border, the osteoclasts lower the pH with hydrogen ions through the carbonic anhydrase system. This lowered pH increases the solubility of the apatite crystals and the mineral can be removed. The organic components of the bone are then hydrolyzed through acidic proteolytic digestion.

Author: Fouad Chaudhry

 

19. Which of the following is characteristic of an active osteoclast: 

A) A large amount of rough endoplasmic reticulum 
B) Paucity of intracellular smooth vesicles 
C) Ruffled border adjacent to the bone surface 
D) Few mitochondria 
E) Low acid phosphatase activity 

Correct Answer: C

Active osteoclasts resorb the mineral and organic matrix of bone. Active osteoclasts also attach the cell to exposed bone matrix. When osteoclasts are studied with an electron microscope, there are two prominent findings — a ruffled border and a clear zone. In the clear zone, the osteoclast seals off the area of bone to be resorbed and attaches to the bone surface through a receptor-mediated process with the assistance of proteins called integrins. The ruffled border is an area found in the infoldings of the cell membrane. 

At the area of the ruffled border, the osteoclasts lower the pH with hydrogen ions through the carbonic anhydrase system. This lowered pH increases the solubility of the apatite crystals and the mineral can be removed. The organic components of the bone are then hydrolyzed through acidic proteolytic digestion. 

Author: Fouad Chaudhry

 

18. A genetic mutation accounts for the manifestations of achondroplasia. Which of the following proteins has a genetic mutation that has been linked to achondroplasia:

A) Fibroblast growth factor (FGF) receptor 3
B) Type I collagen 
C) Fibrillin 
D) Type II collagen 
E) Cartilage oligomeric matrix protein (COMP) 

Correct Answer: A

The genetic defect in achondroplasia involves fibroblast growth factor (FGF) receptor 3.

The other answers refer to:

Osteogenesis imperfecta

Type I collagen

Marfan syndrome

Fibrillin

Spondyloepiphyseal dysplasia

Type II collagen

Pseudoachondroplasia

Cartilage oligomeric matrix protein (COMP)

Author: Fouad Chaudhry

 

17. The tidemark in articular cartilage separates which of the following two zones:

A) The superficial tangential zone and the middle zone 
B) The middle zone and the deep zone 
C) The superficial zone and the deep zone 
D) The deep zone and the calcified zone 
E) The calcified cartilage zone and the subchondral bone zone 

Correct Answer: D

The collagen fibers, proteoglycans, and chondrocytes are distributed through the four articular cartilage zones:

Superficial tangential zone (gliding zone)

  • Thin collagen fibrils are parallel to the articular surface

  • Chondrocytes are elongated with the axis parallel to the surface

  • Proteoglycan content is at the lowest level

  • Water content is at the highest level

Middle Zone

  • Larger diameter collagen fibers/less organization

  • Rounded chondrocytes

Deep Zone

  • Collagen fibers are large and perpendicular to the articular surface

  • Highest concentration of proteoglycans

  • Lowest water content

  • Chondrocytes are spherical and arranged in columnar fashion

Calcified Zone

  • Small cells in cartilage matrix encrusted with apatitic salts

Author: Fouad Chaudhry

 

16. Following a traumatic nerve injury, in which time period would a physician find denervation activity with fibrillation and positive sharp waves in the affected muscles:

A) Immediately following the injury 
B) 7 to 10 days following injury 
C) 2 to 5 weeks following injury 
D) 6 to 8 weeks following injury 
E) 12 weeks following injury 

Correct Answer: C

Nerve conduction studies can help distinguish between the three principle types of nerve injury: neuropraxia, axonotmesis, and neurotmesis.

The following is the sequence of events following traumatic nerve injury:

Timing

Electrophysiologic abnormality

Onset of injury

Conduction block across nerve injury site

7 to 10 days

Reduced amplitudes on distal stimulation

2 to 5 weeks

Denervation changes on electromyographic (EMG)
(fibrillation, positive sharp waves)

6 to 8 weeks

Re-innervation on EMG

 

Author: Fouad Chaudhry

 

15. Which of the following terms is used to describe a localized conduction block in a peripheral nerve in which the nerve is intact and full recovery is expected: 

A) First-degree injury (neuropraxia) 
B) Second-degree (axonotmesis) 
C) Third-degree 
D) Fourth-degree 
E) Fifth-degree 

Correct Answer: A

A first-degree injury is a neuropraxia. There is a local conduction block in which the nerve is intact and full recovery is expected.
• First-degree: Neuropraxia, the nerve structure is intact, full recovery is expected
• Second-degree: Axonotmesis, severance of the axon leading to Wallerian degeneration, continuity of endoneurial sheath is intained, repair is orderly, complete motor and sensory loss with denervation and fibrillation potentials
• Third-degree: Injury to axons and the endoneurial tube, arrangement of individual fascicles is maintained (perineurium intact), recovery is variable
• Fourth-degree: Injury to axons, endoneurial tube, fascicles with the nerve trunk intact, Wallerian degeneration and a higher incidence of proximal nerve cell body degeneration, repair is unlikely and surgical repair of the nerve is necessary (excision and grafting)
• Fifth-degree: Loss of nerve trunk continuity, neuroma formation in the proximal stump, wallerian degeneration distally

Author: Fouad Chaudhry

 

14. Enchondral ossification is responsible for mineralization in all of the following conditions except: 

A) Callus formation during fracture healing
B) Heterotopic bone formation
C) Cartilage degeneration is osteoarthritis
D) Embryonic long bone development
E) Perichondrial bone formation

Correct Answer: E

Enchondral bone formation or ossification is bone formation on a cartilage module. Enchondral bone formation occurs in each of the following scenarios: embryonic long bone development, epiphyseal secondary center of ossification formation, callus formation during fracture healing, degenerating cartilage of osteoarthritis, calcifying cartilage tumors, and bone formed with use of demineralized bone matrix.

Author: Fouad Chaudhry

 

13. The most common location of a chordoma is: 

A) Cervical vertebra
B) Thoracic vertebra
C) Lumbar vertebra
D) Sacrococcygeal region
E) Spheno-occipital region 

Correct Answer: D

Over 50% of the time, chordomas commonly occur in the sacrococcygeal region. Cervical, thoracic, and lumbar vertebral chordomas account for approximately 10% of chordomas. The remaining chordomas occur in the spheno-occipital region.

Author: Fouad Chaudhry

 

12. Which of the following processes may produce cystic bone erosions in the cortex on both sides of a joint:

A) Septic Arthritis
B) Synovial chondormatosis
C) Pigmented villonodular synovitis 
D) Ochronosis
E) Hemochromatosis

Correct Answer: C

Pigmented villonodular synovitis is a synovial proliferative disorder characterized by atraumatic recurrent effusions and cystic erosions of the periarticular bone surfaces. The synovial tissue becomes hypertrophic and can cause large erosions on both sides of the joint. These erosions most commonly occur in the hip joint because of the tight capsule and the limited amount of space for extension of the disease. Conversely, in the knee, there is room for expansion and these erosions occur late in the disease.

Author: Fouad Chaudhry

 

11. What is the most likely complication following treatment of the humeral shaft fracture shown in the figure attached?

A) Nonunion
B) Shoulder pain
C) Infection
D) Elbow injury
E) Radial nerve injury

Correct Answer: B

The humerus was treated with an intramedullary nail. Findings from two prospective randomized studies of intramedullary nailing or compression plating of acute humeral fractures have shown approximately a 30% incidence of shoulder pain with antegrade humeral nailing. This is the most common complica-tion in both of these series. Nonunions are present in approximately 5% to 10% of humeral fractures treated with an intramedullary nail. Infection has an incidence of approximately 1%. Elbow injury is unlikely unless the nail is excessively long. Rarely, injury to the radial nerve is possible if it is trapped in the intramedullary canal.

Author: Salam Al-Abayachi

 

10. Bleeding is encountered while developing the internervous plane between the tensor fascia lata and the sartorius during the anterior approach to the hip. The most likely cause is injury to what artery?

A) Ascending branch of the lateral femoral circumf ex
B) Superior gluteal
C) Femoral
D) Profunda femoris
E) Medial femoral circumfl ex

The correct answer is : A

The ascending branch of the lateral femoral circumfl ex artery crosses the gap between the tensor fascia lata and the sartorious and must be identifi ed and ligated or coagulated. The other ves-sels are out of the f eld of dissection.

Author : Salam Al-Abayachi

 

9. The anatomy of the sciatic nerve as it exits the pelvis is best described as exiting through the:

A) greater sciatic notch and passing between the inferior gemellus and the obturator externus.
B) greater sciatic notch and passing between the piriformis and the superior gemellus.
C) obturator foramen and passing between the obturator internus and the obturator externus.
D) lesser sciatic notch and passing between the piriformis and the superior gemellus.
E) lesser sciatic notch and passing between the superior gemellus and the inferior gemellus.

Best answer:  B

The sciatic nerve is formed by the roots of the lumbosacral plexus. It exits the pelvis through the greater sciatic notch and appears in the buttock anterior to the piriformus. From that point, the sciatic nerve passes posteriorly over the superior gemellus, obturator internus, inferior gemellus, and quadratus femoris before it passes deep to the biceps femoris. The tendon of the obturator internus passes through the lesser sciatic notch.

Author: Salam Al-Abayachi

 

8. Through a retroperitoneal approach to the L4-5 disk, what structure must be ligated to safely mobilize the common iliac vessels toward the midline laterally and gain exposure?

A) Obturator vein
B) Iliolumbar vein
C) External iliac vein
D) Middle sacral artery
E) Hypogastric artery

Best answer:  B

To mobilize the common iliac vessels across the midline, the iliolumbar vein must be ligated. It has a short trunk and can be torn if mobilization is attempted without ligation. It is the only branch off the common iliac vessels (there are no arterial branches) prior to the terminal branches, and the internal (hypogastric) and external iliac vessels. The middle sacral vessels run distally from the axilla of the bifurcation and are a factor when accessing the L5-S1 disk.

Author: Salam Al-Abayachi

 

7. What structure is located at the tip of the arrow in the figure attached?

A) Left L3 nerve root
B) Right L3 nerve root
C) Right L4 segmental artery
D) Right L4 nerve root
E) Left lateral disk herniation

Best answer:  B

The structure shown is the exiting nerve root at the L3-4 disk, which is the right L3 root.

Author: Salam Al-Abayachi

 

6. What structure is most at risk for injury from a retractor against the tracheoesophageal junction during an ant. approach to the cervical spine?

A) Esophagus
B) Trachea
C) Superior laryngeal nerve
D) Recurrent laryngeal nerve
E) Sympathetic chain

Best answer:  D

Although any of these structures can be injured by pressure from the medial blade of a self-retaining retractor, the recurrent laryngeal nerve runs cephalad in the interval between the esopha-gus and trachea and is vulnerable to pressure if caught between the retractor and an infl ated endotra-cheal tube balloon.

Author: Salam Al-Abayachi

 

5. When harvesting an iliac crest bone graft from the post. approach, what anatomic structure is at greatest risk for injury if a Cobb elevator is directed too caudal?

A) Sciatic nerve
B) Cluneal nerves
C) Inferior gluteal artery
D) Superior gluteal artery
E) Sacroiliac joint

Best answer:  D

If a Cobb elevator is directed caudally while stripping the periosteum over the iliac wing, it will encounter the sciatic notch. Although this puts the sciatic nerve at risk, the fi rst structure encountered is the superior gluteal artery. Because it is tethered at the superior edge of the notch, it is very vulnerable to injury and can then retract inside the pelvis, making it diffi cult to obtain hemostasis. 

The inferior gluteal artery exits the sciatic notch below the piriformis and is more protected. The cluneal nerves are at risk only if the incision extends too anteriorly, and the sacroiliac joint can be entered while harvesting the graft.

Author: Salam Al-Abayachi

 

4. The single most important treatment in preventing acute renal failure following crush injury is:

A) maintenance of an alkaline urine (pH > 6) to prevent cast formation
B) maintenance of adequate urine output with mannitol
C) vigourous intravenous fluid replacement
D) administration of xanthine oxidase inhibitors to prevent hyperuricemia
E) emergent dialysis to remove myoglobin from the circulation

Best answer:  C

Treatment focuses on preventing myoglobin precipitation in the urine by maintaining a brisk alkaline diuresis.

* Immediately administer saline to patients with volume depletion.
* Follow-up with mannitol to induce diuresis, supported by adequate IV fluids.
* Raising the pH of the urine to 6.5 or more can be facilitated by adding sodium bicarbonate to the fluids.

 Author: Firas Arnaout

 

3.  A 28 years old man was involved in a motorbike road traffic accident sustaining head injury resulting in a coma and hip fracture. 

Indomethacin is indicated here to prevent which complication?

A) Non union
B) Infection
C) Vascular compromise
D) Pressure ulcers
E) Heterotopic ossification 

Best answer:  E

Heterotopic ossification is formation of bone in the soft tissues, may occur spontaneously or following trauma .It is usually not painful, but presents with loss of movements. 

Prolonged ventilation time, brain injury, spinal cord injury, burns, and amputation thru the zone of injury in a patient injured in a blast are all literature proven risk factors for development of heterotopic ossification. 

Prophylaxis is with the use of Bisphosphonates and Indomethacin and raditherpay.Surgical excision could be performed if there is sever loss of movements.

Ref: Pape HC, Lehmann U, van Griensven M, Gänsslen A, von Glinski S, Krettek C. Heterotopic ossifications in patients after severe blunt trauma with and without head trauma: incidence and patterns of distribution. J Orthop Trauma. 2001 May; 15(4):229-37

Author :Firas Arnaout

 

2.  Number of hits during taper assembly can influence taper seating mechanisms. 

Which of the statement is true regarding single hit versus three hits?

A) One-hit assembled tapers exhibit more contact pressure and total seating of the head taper
B) Three-hits assembled tapers provide superior taper seating
C) Three-hits assembled tapers leads to increased plastic strain
D) One-hit imparts low impulse that is insufficient to seat the modular taper
E) It does not make a difference if you hit once or multiple times to sit the modular taper

Best Answer : A

One-hit assembled tapers exhibit more contact pressure, plastic strain, and total seating of the head tapers relative to the stem taper compared with three-hit sequence to the same peak load. Subsequent mallet hits leads to inferior taper seating

Author - Fouad Chaudhry

 

1.  All of the statements regarding the atypical femur fracture due to bisphosphonate therapy are true EXCEPT :

A) Fracture is located along femoral diaphysis from distal to the lesser trochanter to proximal to supracondylar ridge
B) Fracture is sustained with minimal or no trauma
C) Complete fracture extends through both cortices
D) The fracture line originates at the lateral cortex and is usually transeverse
E) The incomplete fracture can involve either the medial or lateral cortex

Best Answer : E

In 2013, the American Society for Bone and Mineral Research task force developed a revised case definition of atypical femoral fractures. Its definition is that of a fracture located along the femoral diaphysis from just distal to the lesser trochanter to just proximal to the supracondylar flare, with at least four of five major features present. These features are: sustained with minimal or no trauma, the fracture line originates at the lateral cortex and is substantially transverse in its orientation (although it may become oblique as it progresses medially across the femur).

Complete fractures extend through both cortices and may be associated with a medial spike; incomplete fractures involve only the lateral cortex, non-comminuted or minimally-comminuted fractures and localized periosteal or endosteal thickening of the lateral cortex is present at the fracture site.

Author - Fouad Chaudhry

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