ORTHOPEDICS HYPERGUIDE MCQ 851-900

 

851. (3026) Q2-3532:

A man has an X-linked dominant condition and marries a woman who does not carry the abnormal gene. Which of the following is true concerning the offspring:

1) 50% of the daughters will be affected

3) 50% of the sons will be affected

2) 100% of the daughters will be affected

5) 25% of the sons and daughters will be affected

4) 100% of the sons will be affected

With X-linked dominant, heterozygotes will have the condition. If a woman has this condition, then she will transmit it to 50% of her sons and daughters.

In contrast, affected men transmit the condition to all of his daughters (because the daughter gets  his X

chromosome), but to none  of the sons  because the son gets  the Y chromosome.

With X-linked recessive, the patterns are different between women and men.

X-linked recessive woman: An X-linked woman with the recessive allele is a carrier, but she is not affected because the allele is recessive.

C arrier females (X-linked recessive) transmit the condition to 50% of her daughters (who become carriers) and 50% of her sons

(the sons are affected because their only X chromosome has the recessive gene). Correct Answer: 100% of the daughters will be affected

852. (3027) Q2-3533:

A woman has an X-linked dominant condition (single allele being dominant). Which of the following is true:

1) 25% of the offspring will be affected

3) 25% of the sons will be affected

2) 100% of the daughters will be affected

5) 50% of the offspring will be affected

4) 100% of the sons will be affected

With X-linked dominant, heterozygotes will have  the condition. If a woman has this condition, then she will transmit it to 50% of her sons  and daughters.

In contrast, affected men transmit the condition to all of his daughters (because the daughter gets his X chromosome), but to none of the sons because the son gets the Y chromosome.

With X-linked recessive, the patterns are different between women and men.

X-linked recessive woman: An X-linked woman with the recessive allele is a carrier, but she is not affected because the allele is recessive.

C arrier females (X-linked recessive) transmit the condition to 50% of her daughters (who become carriers) and 50% of her sons

(the sons are affected because their only X chromosome has the recessive gene). Correct Answer: 50% of the offspring will be affected

853. (3028) Q2-3535:

Which of the following are actions of parathyroid hormone (PTH):

1) Increases kidney absorption of calcium and increases kidney absorption of phosphate

3) Directly activates osteoclast precursor cells to differentiate into osteoclasts

2) Increases kidney absorption of calcium and decreases kidney absorption of phosphate

5) C auses increased production of calcium binding protein

4) Decreases 1 alpha hydroxylase activity in the kidney

Parathyroid hormone increases calcium reabsorption from the kidney tubular cells and inhibits the reabsorption of phosphate. Remember that PTH signals the osteoblasts to release receptor activator of nuclear factor -kB ligand (RANKL), which causes

osteoclast activation â this is an indirect action. PTH actions:

Facilitates absorption of calcium in the gastrointestinal system

Increases 1,25 dihydroxy vitamin D in the kidney by stimulating 1 alpha hydroxylase

Facilitates reabsorption of calcium from the distal tubular renal tubular cells

C alcium is reabsorbed in the proximal and distal tubules, but only distal tubule is PTH dependent

Inhibits reabsorption of phosphate in the kidney

Stimulates release of calcium and phosphate from bone (indirectly)

C auses release of receptor activator of nuclear factor -kB ligand (RANKL) from the surface of the osteoblasts

Correct Answer: Increases kidney absorption of calcium and decreases kidney absorption of phosphate

854. (3029) Q2-3536:

Which of the following cells has receptors for parathyroid hormone (PTH):

1) Osteoblasts, osteoclasts, and distal kidney nephron

3) Osteoclasts and osteoclast progenitor cells

2) Osteoblasts, osteoclasts, and gastrointestinal cells

5) Osteoclast progenitor cells

4) Osteoblasts and distal kidney nephron

PTH actions:

Facilitates absorption of calcium in the gastrointestinal system

Increases 1,25 dihydroxy vitamin D in the kidney by stimulating 1 alpha hydroxylase

Facilitates reabsorption of calcium from the distal tubular renal tubular cells

C alcium is reabsorbed in the proximal and distal tubules, but only distal tubule is PTH dependent

Inhibits reabsorption of phosphate in the kidney

Stimulates release of calcium and phosphate from bone (indirectly)

C auses release of receptor activator of nuclear factor -kB ligand (RANKL) from the surface of the osteoblasts

Parathyroid hormone exerts its affects through receptors on osteoblasts and kidney nephron cells. Parathyroid hormone effects on the gut are indirect through an increased synthesis of 1,25 dihydroxy vitamin D. Parathyroid hormone acts on osteoblasts to release RANKL, which then acts on the osteoclast progenitor cells to differentiate into osteoclasts.

Correct Answer: Osteoblasts and distal kidney nephron

855. (3030) Q2-3537:

Which of the following is an action of 1,25 dihydroxy vitamin D:

1) Increases synthesis of calcium binding protein

3) Increases bone resorption by directly signaling osteoclasts

2) C auses kidney tubule cells to absorb calcium

5) C auses kidney tubule cells to absorb phosphorus

4) Increases parathyroid hormone (PTH) production

Vitamin D acts on the intestinal to increase calcium absorption. C alcium binding protein synthesis is increased. Vitamin D is an intracellular messenger, acting through the nucleus.

Vitamin D actions:

Increase the efficiency of calcium absorption in the intestine (primarily duodenum) Increases synthesis of calcium binding protein (and others)

Increases passage of calcium through the cell membrane

Moves calcium through the cell cytoplasm and into the circulation

Increases bone resorption by telling the osteoblasts to release receptor activator of nuclear factor -kB ligand

Osteoblasts have vitamin D receptors

Vitamin D receptors exert a negative feedback on 1,25 dihydroxy vitamin D production

Decreases PTH production

Correct Answer: Increases synthesis of calcium binding protein

856. (3031) Q2-3538:

Which of the following cause the release of receptor activator of nuclear factor -kB ligand (RANKL) from the osteoblast cell surface:

1) Osteoprotegerin

3) Insulin-like growth factor

2) Transforming growth factor beta

5) C alcitonin

4) Parathyroid hormone (PTH) receptor

Osteoclast progenitor cells are activated to transform into osteoclasts when the RANKL activates the RANK receptor. The following factors cause release of RANKL from the osteoblast:

PTH

1,25 dihydroxy vitamin D Interleukin 11

Prostaglandin E2

Correct Answer: Parathyroid hormone (PTH) receptor

857. (3032) Q2-3539:

Which of the following cause the release of receptor activator of nuclear factor -kB ligand (RANKL) from the osteoblast cell surface:

1) C alcitonin

3) Transforming growth factor B

2) 1,25 dihydroxy vitamin D

5) Tumor necrosis factor

4) Insulin-like growth factor

Osteoclast progenitor cells are activated to transform into osteoclasts when the RANKL activates the RANK receptor. The following factors cause release of RANKL from the osteoblast:

PTH

1,25 dihydroxy vitamin D Interleukin 11

Prostaglandin E2

Correct Answer: 1,25 dihydroxy vitamin D

858. (3033) Q2-3540:

C alcitonin has which of the following functions:

1) Inhibits the release of receptor activator of nuclear factor -kB ligand (RANKL) from the surface of osteoblasts

3) C auses osteoclasts to withdraw from the bone surface

2) Increases the release of osteoprotegerin from the surface of osteoblasts

5) C auses a decrease in conversion of 25 hydroxy vitamin D into 1,25 dihydroxy vitamin D

4) C auses a decrease in conversion of vitamin D into 25 hydroxy vitamin D

C alcitonin has 1 major action:

Inhibits osteoclastic bone resorption â the osteoclast shrinks and withdraws from the bone surface

C alcitonin can be used in the following conditions:

Paget's disease

Osteoporosis

Hypercalcemia of malignancy

C alcitonin is used less frequently today than in the past. Diphosphonate agents are the main therapeutic agents. Correct Answer: C auses osteoclasts to withdraw from the bone surface

859. (3034) Q2-3541:

Which of the following soft tissue tumors may cause tumor-induced osteomalacia:

1) Liposarcoma

3) Synovial sarcoma

2) Malignant fibrous histiocytoma

5) Atypical lipoma

4) Hemangiopericytoma

Tumor-induced osteomalacia can be caused by a small tumor of bone or soft tissue (phosphaturic tumor). Small tumors may not be detected.

I. General Features

A. Presentation

1. C hronic, vague symptoms - principally, bone pain

2. Muscle weakness

3. Fractures may occur

B. Metabolic profile

1. Hypophosphatemia

2. Low reabsorption of phosphate from the kidney

3. 1,25 dihydroxy vitamin D - low or normal

4. 25 hydroxy vitamin D, 24,25 dihydroxy vitamin D - normal

C . Tumor types

1. Soft tissue

a.  Hemangiopericytoma b.  Sclerosing angioma

c. Benign angiofibroma d.  Neurofibromatosis

D. Pathophysiology

1. A molecule that wastes phosphorus - phosphatonin

E. Radiographic features

1. Osteopenia

2. Pseudofractures

3. C oarsened trabeculae

4. Soft tissue - a small, well-circumscribed soft tissue mass may be noted

F. Treatment

1. Oral phosphate

2. 1,25 dihydroxy vitamin D Correct Answer: Hemangiopericytoma

860. (3035) Q2-3542:

Which of the following bone tumors may cause tumor-induced osteomalacia:

1) Osteosarcoma

3) Osteoblastoma

2) Ewing's sarcoma

5) Malignant fibrous histiocytoma

4) Adamantinoma

Tumor-induced osteomalacia can be caused by a small tumor of bone or soft tissue (phosphaturic tumor). Small tumors may not be detected.

I. General Features

A. Presentation

1. C hronic, vague symptoms - principally, bone pain

2. Muscle weakness

3. Fractures may occur

B. Metabolic profile

1. Hypophosphatemia

2. Low reabsorption of phosphate from the kidney

3. 1,25 dihydroxy vitamin D - low or normal

4. 25 hydroxy vitamin D, 24,25 dihydroxy vitamin D - normal

C . Tumor types

1. Bone

a. Nonossifying fibroma b.  Osteoblastoma

c. Giant cell tumor d. Fibrous dysplasia

D. Pathophysiology

1. A molecule is produced by the tumor that wastes phosphorus - phosphatonin

E. Radiographic features

1. Osteopenia

2. Pseudofractures

3. C oarsened trabeculae

4. Soft tissue - a small, well-circumscribed soft tissue mass may be noted

F. Treatment

1. Oral phosphate

2. 1,25 dihydroxy vitamin D Correct Answer: Osteoblastoma

861. (3036) Q2-3543:

Which of the following would be the metabolic profile for a patient with tumor-induced osteomalacia:

1) Low serum calcium, low serum phosphate

3) Normal serum calcium, low serum phosphate

2) Low serum calcium, high serum phosphate

5) High serum calcium, low serum phosphate

4) Normal serum calcium, high serum phosphate

I. General Features

A. Presentation

1. C hronic, vague symptoms - principally, bone pain

2. Muscle weakness

3. Fractures may occur

B. Metabolic profile

1. Hypophosphatemia

2. Low reabsorption of phosphate from the kidney

3. 1,25 dihydroxy vitamin D - low or normal

4. 25 hydroxy vitamin D, 24,25 dihydroxy vitamin D - normal

C . Pathophysiology

1. A molecule is produced by the tumor that wastes phosphorus - phosphatonin

D. Radiographic features

1. Osteopenia

2. Pseudofractures

3. C oarsened trabeculae

4. Soft tissue - a small, well-circumscribed soft tissue mass may be noted

E. Treatment

1. Oral phosphate

2. 1,25 dihydroxy vitamin D

Correct Answer: Normal serum calcium, low serum phosphate

862. (3037) Q2-3544:

Serum                                                     Urine

C a    P    AP     PTH     25 D     1,25 D       C a Scenario 1            L     L    H       H          L            L             L Scenario 2            N     L    H       N         N           N            N Scenario 3            N     L    N       N         N           N            N Scenario 4            L     L    H       H         N           L             L Scenario 5            L     L    H       H        N/H        N/H           L Scenario 6            L     L    H       H         N           N            H Scenario 7            L     H    H       H          L            L             L

In a patient with metabolic bone disease, which of the above metabolic patterns is most likely vitamin D-deficient rickets:

1) Scenario 1

3) Scenario 3

2) Scenario 2

5) Scenario 5

4) Scenario 4

In patients with vitamin D-deficient rickets, a low amount of vitamin D is present in the diet. Because of a low calcium level in patients with vitamin D deficiency, patients develop secondary hyperparathyroidism.

The increased parathyroid hormone (PTH) causes increased absorption of calcium from the small intestine and decreased absorption of phosphorus from the kidney. Therefore, serum calcium is low or normal, serum phosphate is decreased, and PTH is high. Increased bone resorption occurs, and 25 hydroxy and 1,25 dihydroxy vitamin D are low.

Patients are treated with supplemental vitamin D in their diet. Correct Answer: Scenario 1

863. (3038) Q2-3545:

Serum                                                     Urine

C a    P    AP     PTH     25 D     1,25 D       C a Scenario 1            L     L    H       H          L            L             L Scenario 2            N     L    H       N         N           N            N Scenario 3            N     L    N       N         N           N            N Scenario 4            L     L    H       H         N           L             L Scenario 5            L     L    H       H        N/H        N/H           L Scenario 6            L     L    H       H         N           N            H Scenario 7            L     H    H       H          L            L             L

In a patient with metabolic bone disease, which of the above scenarios would be consistent with dietary phosphate deficiency:

1) Scenario 1

3) Scenario 3

2) Scenario 2

5) Scenario 5

4) Scenario 4

Dietary phosphate deficiency is rare. Patients have a normal serum calcium and parathyroid hormone level, and the vitamin D

levels are also normal. Because of an insufficient amount of phosphate, normal bone mineralization does not occur. Patients are treated with supplemental neutral phosphate.

Correct Answer: Scenario 2

864. (3039) Q2-3546:

Serum                                                     Urine

C a    P    AP     PTH     25 D     1,25 D       C a Scenario 1            L     L    H       H          L            L             L Scenario 2            N     L    H       N         N           N            N Scenario 3            N     L    N       N         N           N            N Scenario 4            L     L    H       H         N           L             L Scenario 5            L     L    H       H        N/H        N/H           L Scenario 6            L     L    H       H         N           N            H Scenario 7            L     H    H       H          L            L             L

A patient has gastrointestinal surgery and develops osteomalacia (rickets). Which of the above scenarios would be the most likely metabolic panel:

1) Scenario 1

3) Scenario 3

2) Scenario 2

5) Scenario 5

4) Scenario 4

Patients who have gastrointestinal surgery or have gastrointestinal disease (eg, C rohn's disease) may develop osteomalacia. The metabolic parameters are similar to that seen with dietary vitamin D deficiency â a low calcium level and resulting hyperparathyroidism.

C alcium is poorly absorbed or a steatorrhea is present, which binds the calcium so that it cannot be well absorbed. Because of a low calcium level, patients develop secondary hyperparathyroidism.

The increased parathyroid hormone (PTH) causes increased absorption of calcium from the small intestine and decreased absorption of phosphorus from the kidney. Therefore, serum calcium is low or normal, serum phosphate is decreased, and PTH is high. Increased bone resorption occurs, and 25 hydroxy and 1,25 dihydroxy vitamin D are low.

Correct Answer: Scenario 1

865. (3040) Q2-3547:

Serum                                                     Urine

C a    P    AP     PTH     25 D     1,25 D       C a Scenario 1            L     L    H       H          L            L             L Scenario 2            N     L    H       N         N           N            N Scenario 3            N     L    N       N         N           N            N Scenario 4            L     L    H       H         N           L             L Scenario 5            L     L    H       H        N/H        N/H           L Scenario 6            L     L    H       H         N           N            H Scenario 7            L     H    H       H          L            L             L

A patient has phosphate diabetes (vitamin D-resistant rickets). Which of the above metabolic profiles would most likely result:

1) Scenario 1

3) Scenario 4

2) Scenario 3

5) Scenario 7

4) Scenario 6

Phosphate diabetes is a type of vitamin D-resistant rickets. Patients are unable to reabsorb phosphate in the kidney tubules. The serum phosphate level is low, and patients are unable to mineralize osteiod because of the low phosphate. Serum calcium, parathyroid hormone, and vitamin D levels are normal. Patients are treated with large amounts of neutral phosphate in the diet.

Patients are resistant to vitamin D because of their inability to reabsorb phosphate in the kidney tubules. Correct Answer: Scenario 3

866. (3041) Q2-3548:

Serum                                                     Urine

C a    P    AP     PTH     25 D     1,25 D       C a Scenario 1            L     L    H       H          L            L             L Scenario 2            N     L    H       N         N           N            N Scenario 3            N     L    N       N         N           N            N Scenario 4            L     L    H       H         N           L             L Scenario 5            L     L    H       H        N/H        N/H           L Scenario 6            L     L    H       H         N           N            H Scenario 7            L     H    H       H          L            L             L

Which of the above metabolic profiles occurs in a patient who had vitamin D-resistant rickets with the inability to produce adequate amounts of the 1,25 dihydroxy vitamin D:

1) Scenario 3

3) Scenario 5

2) Scenario 4

5) Scenario 7

4) Scenario 6

Vitamin D-resistant rickets may occur when there is an inability to convert 25 hydroxy vitamin D into 1,25 dihydroxy vitamin D. Patients develop secondary hyperparathyroidism. A low serum calcium level causes an increased parathyroid hormone (PTH)

level. Parathyroid hormone causes the kidneys not to reabsorb phosphorus, and the serum phosphate is low. The serum 1,25 dihydroxy vitamin D level is low.

The metabolic profile is: Serum calcium          Low

Serum phosphate      Low

Serum PTH               High

25 vitamin D             Normal

1,25 vitamin D          Very low

Treatment is by dietary 1,25 dihydroxy vitamin D. Correct Answer: Scenario 4

867. (3042) Q2-3549:

Serum                                                    Urine

C a   P   AP     PTH     25 D     1,25 D       C a Scenario 1            L     L    H       H          L            L             L Scenario 2            N    L    H       N         N           N            N Scenario 3            N    L    N       N         N           N            N Scenario 4            L     L    H       H         N           L             L Scenario 5            L     L    H       H        N/H        N/H           L Scenario 6            L     L    H       H         N           N            H Scenario 7            L     L    H       H          L            L             L

Which of the above metabolic profiles occurs in a patient with vitamin D-resistant rickets with end-organ insensitivity to 1,25 dihydroxy vitamin D:

1) Scenario 3

3) Scenario 5

2) Scenario 4

5) Scenario 7

4) Scenario 6

One form of vitamin D-resistant rickets is end-organ insensitivity to 1,25 dihydroxy vitamin D. The small intestine gastrointestinal cells are not able to respond to 1,25 dihydroxy vitamin D. The serum calcium is low, and patients develop secondary hyperparathyroidism - high serum parathyroid hormone (PTH). The high serum PTH causes the kidneys not to reabsorb phosphate so that the serum phosphate level is low.

The metabolic profile is: Serum calcium          Low

Serum phosphate      Low

Serum PTH               High

25 vitamin D             Normal or high

1,25 vitamin D          Normal or high

Treatment is difficult; some patients with mild involvement are treated with vitamin D, and patients with severe disease may require calcium infusions.

Correct Answer: Scenario 7

868. (3043) Q2-3550:

Serum                                                     Urine

C a    P    AP     PTH     25 D     1,25 D       C a Scenario 1            L     L    H       H          L            L             L Scenario 2            N     L    H       N         N           N            N Scenario 3            N     L    N       N         N           N            N Scenario 4            L     L    H       H         N           L             L Scenario 5            L     L    H       H        N/H        N/H           L Scenario 6            L     L    H       H         N           N            H Scenario 7            L     H    H       H          L            L             L

Which of the above metabolic profiles occurs in a patient with renal tubular acidosis:

1) Scenario 3

3) Scenario 5

2) Scenario 4

5) Scenario 7

4) Scenario 6

In patients with renal tubular acidosis, the kidney has to secrete a positive ion (Na, C a) to balance the pH. The secretion of calcium ions results in ostomalacia or rickets as there is insufficient calcium to mineralize newly formed osteiod.

With low serum calcium levels, the serum parathyroid hormone (PTH) level increases, causing decreased reabsorption of phosphate. Vitamin levels are normal. Renal tubular acidosis is the only condition in which there is increased urinary excretion of calcium.

The metabolic profile is: Serum calcium          Low

Serum phosphate      Low

Serum PTH               High

25 vitamin D             Normal

1,25 vitamin D          Normal

Urinary C a               High

The treatment of renal tubular acidosis is to alkalinize the urine. Correct Answer: Scenario 6

869. (3044) Q2-3551:

Serum                                                     Urine

C a    P    AP     PTH     25 D     1,25 D       C a Scenario 1            L     L    H       H          L            L             L Scenario 2            N     L    H       N         N           N            N Scenario 3            N     L    N       N         N           N            N Scenario 4            L     L    H       H         N           L             L Scenario 5            L     L    H       H        N/H        N/H           L Scenario 6            L     L    H       H         N           N            H Scenario 7            L     H    H       H          L            L             L

Which of the above metabolic profiles occurs in a patient with renal osteodystrophy:

1) Scenario 1

3) Scenario 5

2) Scenario 3

5) Scenario 7

4) Scenario 6

In patients with renal osteodystrophy, the renal tubular cells are damaged, resulting in the retention of phosphate. The kidney cells are unable to produce 1,25 dihydroxy vitamin D. Because the serum calcium level is low, patients develop secondary hyperparathyroidism.

The metabolic profile is: Serum calcium          Low

Serum phosphate      High

Serum PTH               High

1,25 vitamin D          Low

The treatment is correction of the hyperparathyroidism. Correct Answer: Scenario 7

870. (3045) Q2-3552:

Which of the following serum metabolic profiles describes a patient with hypophosphatasia:

1) Normal calcium, normal dihydroxy vitamin D, and low alkaline phosphatase

3) Low calcium, low dihydroxy vitamin D, and low alkaline phosphatase

2) Low calcium, normal dihydroxy vitamin D, and low alkaline phosphatase

5) High calcium, high dihydroxy vitamin D, and high alkaline phosphatase

4) High calcium, high dihydroxy vitamin D, and low alkaline phosphatase

Hypophosphatasia is the inability to synthesize alkaline phosphatase by the bone, leukocytes, kidney, and intestine

1. Autosomal recessive

2. High levels of phosphoethanolamine  in the urine

3. When severe (high mortality)

a. Growth retardation, failure to thrive b. Irritability, fever, vomiting

4. When mild

a. Fractures

b. Short stature

c. Poor fracture healing d.  Osteomalacia

5. Radiographic features a.  Osteopenia

b. C up-shaped deformities of the proximal long bones

6. Histological features - unmineralized osteiod seams

7. Laboratory features

a. Low serum alkaline phosphatase

b. Normal Ca, 1,25 dihydroxy vitamin D

8. C ause - inability to mineralize osteiod because the absence of alkaline phosphatase

9. Treatment - high doses of vitamin D

Correct Answer: Normal calcium, normal dihydroxy vitamin D, and low alkaline phosphatase

871. (3046) Q2-3553:

Which of the following inheritance patterns occurs in patients with hypophosphatasia:

1) Autosomal recessive

3) X-linked dominant

2) Autosomal dominant

5) Sporadic

4) X-linked recessive

Hypophosphatasia is the inability to synthesize alkaline phosphatase by the bone, leukocytes, kidney, and intestine

1. Autosomal recessive

2. High levels of phosphoethanolamine  in the urine

3. When severe (high mortality)

a. Growth retardation, failure to thrive b. Irritability, fever, vomiting

4. When mild

a. Fractures

b. Short stature

c. Poor fracture healing d.  Osteomalacia

5. Radiographic features a.  Osteopenia

b. C up-shaped deformities of the proximal long bones

6. Histological features - unmineralized osteiod seams

7. Laboratory features

a. Low serum alkaline phosphatase

b. Normal C a, 1,25 dihydroxy vitamin D

8. C ause - inability to mineralize osteiod because the absence of alkaline phosphatase

9. Treatment - high doses of vitamin D Correct Answer: Autosomal recessive

872. (3047) Q2-3554:

Which of the following is the basic defect in patients with pseudohypoparathyroidism  (Albright Hereditary Osteodystrophy

[AHO]):

1) End-organ resistance to 1,25 dihydroxy vitamin D

3) Inability to reabsorb phosphate in the kidney

2) End-organ resistance to parathyroid hormone (PTH)

5) Inability to synthesize alkaline phosphatase

4) Inability to produce 1,25 dihydroxy vitamin D

Pseudohypoparathyroidism  (AHO) - end-organ insensitivity; in AHO, germline mutation that leads to loss of function of Galpha S (GNAS1); causes end-organ resistance to PTH

1. PHP - short stature, short metacarpals (4th and 5th), rounded facies a. Mental retardation, tetany

b. Sex-linked dominant

2. Laboratory features a.  Hypocalcemia

b.  Hyperphopshatemia c.  Normal PTH

Correct Answer: End-organ resistance to parathyroid hormone (PTH)

873. (3048) Q2-3555:

Which of the following is the mode of inheritance for pseudohypoparathyroidism  (Albright Hereditary Osteodystrophy [AHO]):

1) Autosomal recessive

3) Sex-linked dominant

2) Autosomal dominant

5) Sporadic

4) Sex-linked recessive

Pseudohypoparathyroidism  (AHO) - end-organ insensitivity; in AHO, germline mutation that leads to loss of function of Galpha S (GNAS1); causes end-organ resistance to PTH

1. PHP - short stature, short metacarpals (4th and 5th), rounded facies a. Mental retardation, tetany

b. Sex-linked dominant

2. Laboratory features a.  Hypocalcemia

b.  Hyperphopshatemia c.  Normal PTH

Correct Answer: Sex-linked dominant

874. (3049) Q2-3556:

Which of the following is the defect in pseudohypoparathyroidism  (Albright Hereditary Osteodystrophy [AHO]):

1) C artilage oligometric matrix protein

3) Sulfate transport protein

2) Fibroblast growth factor receptor 3

5) Galpha S (GNAS1)

4) Type II collagen

Pseudohypoparathyroidism  (AHO) - end-organ insensitivity; in AHO, germline mutation that leads to loss of function of Galpha S (GNAS1); causes end-organ resistance to PTH

1. PHP - short stature, short metacarpals (4th and 5th), rounded facies a. Mental retardation, tetany

b. Sex-linked dominant

2. Laboratory features a.  Hypocalcemia

b.  Hyperphopshatemia c.  Normal PTH

The other responses are also important to know:

C artilage oligometric matrix protein - pseudoachondroplasia

Fibroblast growth factor receptor 3 - achondroplasia Sulfate transport protein - diastrophic dysplasia Type II collagen - spondyloepiphyseal dysplasia

Correct Answer: Galpha S (GNAS1)

875. (3071) Q2-3579:

Which of the following methods reduce radiation exposure to a surgeon during fluoroscopic procedures:

1) Avoiding the inverted C -arm position

3) Limiting the use of the foot pedal for controlling the fluoroscopy unit

2) Avoiding collimation of the radiation beam

5) Increasing the amperage of each exposure

4) Always standing on the opposite side of the C -arm

One of the best ways to limit radiation exposure is to increase distance from the C -arm. Surgeons should always stand on the opposite side of the C -arm and remember the following methods for reducing radiation exposure:

Increase distance (doubling distance reduces exposure by a factor of 4) Inverted position of the C -arm (increases distance)

Shielding: 90% attenuated by 0.25-mm apron

C ollimation (reduces the size of the beam)

Foot pedal to control the fluoroscopy unit (decreases the amount of exposure)

Correct Answer: Always standing on the opposite side of the C -arm

876. (3072) Q2-3580:

At which of the following distances can surgeons expect to have no radiation exposure from scatter from a fluoroscopy unit:

1) 6 in

3) 2 ft

2) 1 ft

5) 6 ft

4) 3 ft

Radiation exposure decreases by a factor of 4 when a surgeon doubles the distance from the radiation beam. No radiation exists 6 ft from a fluoroscopy unit.Correct Answer: 6 ft

877. (3073) Q2-3581:

Which of the following amounts of radiation is received from a chest radiograph:

1) 1 mrem

3) 25 mrem

2) 10 mrem

5) 1,000 mrem

4) 500 mrem

Surgeons should know the radiation doses from common diagnostic tests. C ommon radiation exposures:

C hest radiograph

Hip radiograph

Hip computed tomography

C -arm (in beam)

Mini C -arm (in beam)

25 mrem

500 mrem

1,000 mrem

1,200 mrem/min to 4,000 mrem/min

120 mrem/min to 400 mrem/min

Correct Answer: 25 mrem

878. (3074) Q2-3582:

Which of the following amounts of radiation is received from a hip radiograph:

1) 10 mrem

3) 100 mrem

2) 25 mrem

5) 1,000 mrem

4) 500 mrem

Surgeons should know the radiation doses from common diagnostic tests. C ommon radiation exposures:

C hest radiograph

Hip radiograph

Hip computed tomography

C -arm (in beam)

Mini C -arm (in beam)

25 mrem

500 mrem

1,000 mrem

1,200 mrem/min to 4,000 mrem/min

120 mrem/min to 400 mrem/min

Correct Answer: 500 mrem

879. (3075) Q2-3583:

Which of the following amounts of radiation are received from a computed tomography (C T) scan of the hip:

1) 25 mrem

3) 500 mrem

2) 100 mrem

5) 5,000 mrem

4) 1,000 mrem

Surgeons should know the radiation doses from common diagnostic tests. C ommon radiation exposures:

C hest radiograph               25 mrem Hip radiograph                   500 mrem Hip computed tomography  1,000 mrem

C -arm (in beam                 1,200 mrem/min to 4,000 mrem/min

Mini C -arm (in beam          120 mrem/min to 400 mrem/min

Correct Answer: 1,000 mrem

880. (3076) Q2-3584:

Which of the following amounts of radiation are the maximum annual exposures to the whole body, thyroid gland, and hands:

1) 1 rem, 15 rem, 25 rem

3) 5 rem, 60 rem, 100 rem

2) 2 rem, 30 rem, 50 rem

5) 20 rem, 100 rem, 200 rem

4) 10 rem, 75 rem, 150 rem

Surgeons should know the maximum annual exposures of radiation.

Total body dose

Eye Thyroid Skin, hands Fetus

Correct Answer: 2 rem, 30 rem, 50 rem

2 rem or 5 rem

15 rem

30 rem

50 rem

0.5 rem over a period of 9 months

(<0.05 mrem per month)

881. (3077) Q2-3585:

Which of the following numbers is the approximate number of intramedullary nailings of the tibia or femur that can be performed safely in regard to the maximum allowable radiation dose from a C -arm unit:

1) 50

3) 200

2) 100

5) 400

4) 300

C - arm fluoroscopy units- 4,000 mrem/min in the beam

5 mrem/min at 2 ft: scatter

1 mrem/min at 4 ft: scatter

Distances for which no radiation is expected

Scatter: 0.1%, 3 ft from beam

0.025%, 6 ft from beam

Intramedullary nailing 100 mrem/nailing to127 mrem/nailing

Translates to 394 nailings per year for safe exposure

Intramedullary nailing (femur, tibia)

Average exposure: 100 mrem/operation

Average exposure (hands): 127 mrem/operation

Tolerance:

Hands: Approximately 400 patients per year

Thyroid gland: 1,960 patients per year

Important points

Placing pedicle screws results in the highest radiation exposure.

Surgeons should avoid placing their hands directly in the radiation beam. Correct Answer: 400

882. (3261) Q2-4088:

Which of the following statements is true concerning anterior cruciate ligament (AC L) tears in children with open physes:

1) The pattern of AC L failure is the same as adults.

3) The Lachmanâs test is seldom positive.

2) Associated meniscal tears are uncommon.

5) The pivot shift test is seldom positive.

4) The tear often occurs at the tibial insertion.

Although AC L injuries are less common in children than adults, this knee injury is becoming more common as children are involved in more athletic activities. Important points to remember include:

In children, the AC L collagen fibers extend from the ligament to epiphyseal cartilage. Many AC L injuries occur at the tibial insertion.

Tibial eminence avulsion fractures often accompany AC L injury. Associated meniscal injuries are common.

The physical examination findings are the same as in adults. Bicycle accidents are a common mechanism of injury.

Correct Answer: The tear often occurs at the tibial insertion.

883. (3262) Q2-4090:

Which of the following is found during differentiation of chondrocytes and the formation of the cartilage anlagen during enchondral growth:

1) C BAF1/RUNX2

3) Osterix

2) Vascular endothelial factor alpha (VEGF-A)

5) Receptor activator of nuclear factor-kB ligand (RANKL)

4) Low level of beta-catenin

Low levels of beta-catenin cause the mesenchyme to differentiate into cartilage (upregulation of SOX9). The chondrocytes develop organelles and produce cartilage specific collagens, types II, IX, and XI. The cartilage anlagen grows by interstitial and appositional growth, taking the shape of normal bones (epiphysis, metaphysis, and diaphysis).

Different processes and signals occur when the diaphysis ossifies. The cartilage cells stop growing and they hypertrophy. The chondrocytes express C BAF1/RUNX2 and VEGF-A. These factors attract blood vessels, osteoblasts, cartilage, and bone resorbing cells. The primary ossification center is then formed. The cartilage is removed, and the bone forms. At the surface of the diaphysis, the mesenchymal cells become osteoblasts and form bone.

Correct Answer: Low level of beta-catenin

884. (3263) Q2-4091:

Which of the following is found during the process of forming the primary ossification center (transition from primary cartilage anlagen to bone):

1) SOX9

3) Low levels of beta-catenin

2) Osteoprotegerin (OPG)

5) Receptor activator of nuclear factor-kB ligand (RANKL)

4) High levels of beta-catenin

Low levels of beta-catenin cause the mesenchyme to differentiate into cartilage (up-regulation of SOX9). The chondrocytes develop organelles and produce cartilage specific collagens, types II, IX, and XI. The cartilage anlagen grows by interstitial and appositional growth, taking the shape of normal bones (epiphysis, metaphysis, and diaphysis).

Different processes and signals occur when the diaphysis ossifies. The cartilage cells stop growing and they hypertrophy. High levels of beta-catenin induce this process (involves Wnt signaling and up-regulation of beta-catenin). The chondrocytes express C BAF1/RUNX2 and VEGF-A. These factors attract blood vessels, osteoblasts, cartilage, and bone resorbing cells. The primary ossification center is then formed. The cartilage is removed, and the bone forms. At the surface of the diaphysis, the mesenchymal cells become osteoblasts and form bone.

Correct Answer: High levels of beta-catenin

885. (3264) Q2-4101:

Which of the following occurs with myopathies:

1) Focal demyelination

3) High amplitude-long duration motor unit potentials

2) Nerve conduction velocity slowing

5) Specific conduction block sites

4) Small amplitude-short duration motor unit potentials

With focal nerve compression, focal demyelination is present. The axon remains intact but, with myelin loss, slowing of conduction occurs and a conduction block is possible.

C ommon findings with focal nerve compression include: Focal demyelination

Nerve conduction velocity slowing

C onduction block across the site

Fibrillation potentials

Positive sharp waves

High amplitude-long duration motor unit potentials (chronic denervation)

In contrast, small amplitude-short duration motor unit potentials are found in myopathy. Correct Answer: Small amplitude-short duration motor unit potentials

886. (3265) Q2-4103:

Which of the following is typically found with electrodiagnostic testing in neurogenic lesions:

1) C omplex repetitive discharges

3) Myotonic discharges

2) Myokymic potentials

5) Fibrillations

4) Positive sharp waves

With electrodiagnostic testing, a clinician may find several characteristic features in different disorders: Denervation

Fibrillation

Positive sharp waves

Fasciculations

Neurogenic lesions

Fasciculations

Myokymic potentials

Myopathies

C omplex repetitive discharges

Myotonic discharges

Correct Answer: Myokymic potentials

887. (3266) Q2-4104:

Which of the following is typically found with electrodiagnostic testing in myopathies:

1) Positive sharp waves and fibrillations

3) C omplex repetitive discharges and myotonic discharges

2) Positive sharp waves

5) Myokymic potentials

4) Fasciculations and myokymic potentials

With electrodiagnostic testing, a clinician may find several characteristic features in different disorders: Denervation

Fibrillation

Positive sharp waves

Fasciculations

Neurogenic lesions

Fasciculations

Myokymic potentials

Myopathies

C omplex repetitive discharges

Myotonic discharges

Correct Answer: C omplex repetitive discharges and myotonic discharges

888. (3267) Q2-4106:

Fasciculation potentials are spontaneous discharges of whole motor units. This type of electrodiagnositic finding is found in each of the following disorders except:

1) Anterior motor horn disease

3) C ervical spondylytic myelopathy

2) Radiculopathy

5) Demyelinating myopathy

4) Muscle denervation

Fasciculation potentials are spontaneous discharges of the whole motor unit. This electrodiagnostic finding is found in:

Anterior motor horn diseases C ervical spondylytic myelopathy Radiculopathy

Demyelinating neuropathy

With denervation of skeletal muscle, electrodiagnostic testing includes:

Fibrillation potentials

Low amplitude short bi- or triphasic deflections

Positive sharp waves

Positive deflections followed by a negative wave

Correct Answer: Muscle denervation

889. (3268) Q2-4111:

Which of the following statements is true concerning intraoperative acetabular fractures following uncemented total hip arthroplasty:

1) The incidence is lowest with an elliptical monoblock design.

3) The location of the fracture is most commonly anterosuperior.