ORTHOPEDICS HYPERGUIDE MCQ 551-600

551. (70) Q2-110:

Which of the following statements concerning the medial and lateral menisci is correct:

1) The medial meniscus is more mobile than the lateral meniscus

3) The menisci transmit 50% of the joint forces with the knee in extension

2) The posterior horn of the lateral meniscus is the most mobile

5) The menisci transmit 50% of the joint forces with the knee in flexion

4) The lateral meniscus is important to restrain anterior tibial translation

The menisci have an important function in load transmission, shock absorption, stability, and articular cartilage nutrition. One should remember the following facts concerning the menisci:

Vascularity

Peripheral 30% of the medial meniscus is vascular. Peripheral 25% of the lateral meniscus is vascular.

Mobility

The lateral meniscus is more mobile than the medial meniscus. The anterior portion of the lateral meniscus is the most mobile.

Load transmission

Fifty percent of the joint forces are transmitted through the menisci in knee extension. Ninety percent of the joint forces are transmitted through the menisci in knee flexion.

The meniscal stiffness increases with higher deformation rates (secondary to the viscoelastiCproperties of the fibrocartilage).

Stability

The medial meniscus provides a very important secondary restraint to anterior translation of the tibia. Correct Answer: The menisci transmit 50% of the joint forces with the knee in extension

552. (71) Q2-115:

In regard to the vascularity of the menisci, which of the following statements are correct:

1) The capillary plexus penetrates the peripheral 30% of the medial meniscus.

3) The capillary plexus penetrates the peripheral 70% of the medial meniscus.

2) The capillary plexus penetrates the peripheral 50% of the medial meniscus.

5) The entire width of the medial meniscus has excellent vascularity.

4) The capillary plexus penetrates the peripheral 90% of the medial meniscus.

The periphery of the medial and lateral menisci obtain their blood supply from a peri-meniscal capillary plexus from the inferior and superior geniculate arteries. This capillary plexus extends from the periphery to:

30% of the medial meniscus

25% of the lateral meniscus

The inner 70% to 75% of the menisci contain no blood vessels (avascular) and derive their nutrients from the synovial fluid. Correct Answer: The capillary plexus penetrates the peripheral 30% of the medial meniscus.

553. (72) Q2-116:

Meniscal fibrocartilage is principally composed of which of the following types of collagen:

1) Type I

3) Type VI

2) Type II

5) Type X

4) Type IX

The meniscus is composed of a complex, 3 dimensional interlacing network of collagen fibers, proteoglycan, glycoproteins, and interspersed cells of fibrochondrocyte. The meniscal extracellular matrix is composed primarily of Type I collagen fibers that are oriented circumferentially to resist tension.

Correct Answer: Type I

554. (73) Q2-117:

Bone bruises, or occult osteochondral injury, occur in up to 80% of patients with an anterior cruciate ligament rupture. The most common location of this articular injury is:

1) Medial femoral condyle

3) Medial patellar facet

2) Medial tibial plateau

5) Lateral patellar facet

4) Lateral femoral condyle

Bone bruises, or occult osteochondral injury, occur in up to 80% of patients following an anterior cruciate ligament injury. The most common locations are the lateral femoral condyle and the lateral tibial plateau. These injuries damage not only the subchondral bone, but the articular cartilage, as well.

Correct Answer: Lateral femoral condyle

555. (74) Q2-118:

Which of the following occurs when a joint is immobilized:

1) Slow decrease in collagen concentration

3) Slow decrease in proteoglycan concentration

2) Rapid decrease in collagen concentration

5) No change in either collagen or proteoglycan concentration

4) Rapid decrease in proteoglycan concentration

Motion is essential for normal articular cartilage function. Many changes occur in the articular cartilage, ligaments, capsules, and bone within a joint when it is immobilized.

There is a rapid loss of proteoglycan when a joint becomes immobilized. This loss of proteoglycan results in an increase of deformation and fluid flux when compressive loads are applied to the joint. The collagen content of the cartilage does not change and the tensile properties are maintained.

The changes are reversible and the recovery depends upon how long the joint is immobilized. Correct Answer: Rapid decrease in proteoglycan concentration

556. (75) Q2-119:

Articular cartilage exhibits viscoelastiCbehavior (time dependent behavior). When a constant load is applied, the deformation of the articular cartilage will increase. This process is called:

1) Relaxation

3) Stretching

2) Creep

5) Fretting

4) Corrosion

Articular cartilage exhibits viscoelastiCbehavior (time dependent). If one applies a constant load, the deformation will increase with time. This process is called creep.

Correct Answer: Creep

557. (76) Q2-120:

Articular cartilage is composed of 4 zones. The chondrocytes of which of the following zones produce a high concentration of collagen and a low concentration of proteoglycan:

1) Superficial tangential zone

3) Deep zone

2) Middle zone

5) Tidemark zone

4) Calcified zone

The 4 articular cartilage layers have different functions and properties: superficial tangential zone, middle zone, deep zone, and calcified zone. The chondrocytes in the superficial tangential zone produce high concentrations of collagen and low concentrations of proteoglycan.

The functions of each of the zones is as follows:

Zone Function

Superficial tangential zone

Parallel arrangement of the collagen fibrils provides the greatest tensile stiffness; chondrocytes produce high concentrations of collagen and low amounts of proteoglycan

Middle zone Has properties intermediate between the superficial tangential zone and deep zone

Deep (radial) zone

Has the largest collagen fibrils and the highest concentration of proteoglycans, and lowest amount of water

Calcified zone Cells have a small volume and are surrounded by calcified cartilage

Correct Answer: Superficial tangential zone

558. (77) Q2-121:

Which of the following types of collagen is the most common type in articular cartilage:

1) Type I

3) Type IV

2) Type II

5) Type X

4) Type IX

Type II collagen is the predominant type in articular cartilage (95%). There are a number of other collagens in smaller amounts

(Types IV, VI, IX, X, and XI).

Type VI: Assists with matrix attachment

Types IX, XI: May help form and stabilize the collagen fibrils formed from Type II collagen

Correct Answer: Type II

559. (109) Q2-154:

A 12-year-old boy has multiple exostoses (osteochondromas). What is the most likely pattern of inheritance in this condition:

1) Autosomal recessive

3) X-linked recessive

2) Autosomal dominant

5) Almost always a spontaneous mutation

4) X-linked dominant

Multiple exostoses is transmitted in an autosomal dominant pattern. This condition is transmitted by both sexes with incomplete penetrance in females. This condition is more common in males.

Correct Answer: Autosomal dominant

560. (114) Q2-159:

Which of the following describes the microscopiCfeatures of a bone island:

1) Interlacing network of bone trabeculae in a loose, vascular, stromal connective tissue

3) Scattered giant cells in a mononuclear cell background with chicken-wire calcification

2) Compact cortical bone

5) Prominent mature bone formation and low-grade malignant spindle cell tumor

4) PleomorphiCspindle cells with osteoid production

Bone islands are microscopically composed of lamellar compact bone identical to the cortical bone. The other possible answers describe specifiClesions:

Chondroblastoma: Scattered giant cells in a mononuclear cell background with chicken-wire calcification

Osteosarcoma: PleomorphiCspindle cells with osteoid production

Parosteal osteosarcoma: Prominent mature bone formation and low-grade malignant spindle cell tumor

Osteoblastoma: Interlacing network of bone trabeculae in a loose, vascular, stromal connective tissue

Correct Answer: Compact cortical bone

561. (131) Q2-176:

Which of the following lesions would display a low to moderate signal on T1 weighted images and high signal on T2 weighted images:

1) Lipomas

3) Cortical bone

2) Subcutaneous fat

5) Tendons

4) Malignant fibrous histiocytoma

All soft tissue sarcomas have the same signal sequence - low on T1 weighted images and high on T2 weighted images. It is important to remember the appearances of common tissues on both T1 and T2 weighted images:

 T1 weighted T2 weighted

Fat High Moderate Tendons Low Low Ligaments Low Low Fascial layers Low Low Cortical bone Low Low Muscle Moderate Moderate Normal marrow High Moderate Soft tissue sarcomas Low High

Fluid (ganglions, effusions) Low High

Pigmented villonodular synovitis* Very low Very low

Signal drop out (very low signal on gradient echo sequences) Correct Answer: Malignant fibrous histiocytoma

562. (132) Q2-177:

Which of the following tissues is low signal on both T1 and T2 weighted images:

1) Subcutaneous fat

3) Muscle

2) Joint fluid

5) Tendons

4) Soft tissue sarcomas

Tissues that are principally composed of collagen and fibroblasts are low signal on both T1 and T2 weighted sequences include tendons, ligaments, and fascial layers.

It is important to remember the appearances of common tissues on both T1 and T2 weighted images:

 T1 weighted T2 weighted

Fat High Moderate Tendons Low Low Ligaments Low Low Fascial layers Low Low Cortical bone Low Low Muscle Moderate Moderate Normal marrow High Moderate Soft tissue sarcomas Low High

Fluid (ganglions, effusions) Low High

Pigmented villonodular synovitis* Very low Very low

Signal drop out (very low signal on gradient echo sequences) Correct Answer: Tendons

563. (140) Q2-185:

Which of the following describes the radiographiCfeatures of a bone island:

1) Ovoid, compact, heavily mineralized intramedullary lesion with thorny spicules

3) Surface lesion with spiculated bone formation

2) Large, nodular, heavily mineralized lesion on the surface of the bone

5) Cortically based lytiCmetaphyseal lesion with a sclerotiCborder

4) Well-demarcated nidus surrounded by a distinct zone of sclerosis

Bone islands are also referred to as enostosis. They are usually solitary and composed of dense, compact bone within the medullary cavity. Patients are often asymptomatiCand the bone island is discovered as an incidental finding.

There are three features that may lead to confusion: The lesion may be as large as 3 cm to 5 cm.

The bone scan may show mild activity within the lesion.

Bone islands may grow slowly (approximately 1 mm per year).

The other possible answers describe the radiographiCfeatures of other lesions:

Osteoid osteoma: Well-demarcated nidus surrounded by a distinct zone of sclerosis

Parosteal osteosarcoma: Large, nodular, heavily mineralized lesion on the surface of the bone

Periosteal osteosarcoma:Surface lesion with spiculated bone formation

Non-ossifying fibroma: Cortically based lytiCmetaphyseal lesion with a sclerotiCborder

Correct Answer: Ovoid, compact, heavily mineralized intramedullary lesion with thorny spicules

564. (483) Q2-669:

Which of the following statements is not true of the meniscus:

1) Only the peripheral 25% to 30% of the meniscus has a vascular supply.

3) Fifty percent of the compressive load of the knee is transmitted through the meniscus when the knee is extended.

2) The medial meniscus functions as a secondary restraint to anterior tibial translation.

5) The lateral meniscus is semicircular in shape.

4) Meniscal fibrochondrocytes have the ability to proliferate and synthesize matrix. One should remember these features of the meniscus:

1. Only the peripheral 25% to 30% of the meniscus has a vascular supply.

2. The medial meniscus functions as a secondary restraint to anterior tibial translation (when the anterior cruciate ligament is cut).

3. Fifty percent of the compressive load of the knee is transmitted through the meniscus when the knee is extended.

4. Eighty-five percent of the compressive load of the knee is borne by the menisci when the knee is in 90° of flexion.

5. Meniscal fibrochondrocytes have the ability to proliferate and synthesize matrix.

6. The medial meniscus is semicircular in shape; the lateral meniscus is circular in shape. Correct Answer: The lateral meniscus is semicircular in shape.

565. (484) Q2-670:

Which of the following collagen macromolecules found in articular cartilage confers the major amount of tensile strength and resistance to shear stress:

1) Type X collagen

3) Type IX collagen

2) Type II collagen

5) Type VI collagen

4) Type XI collagen

Type II collagen is the major collagen moiety found in articular cartilage. As such it confers the major amount of tensile strength and resistance to shear stress. Articular cartilage is a highly ordered structure with a flattened layer of chondrocytes at the surface and a tangential arrangement of surface collagen. Progressing into the transitional zone the collagen fibrils assume a random orientation. In the radial zone the fibrils become oriented perpendicular to the joint surface and interface with the subchondral bone

■Correct Answer: Type II collagen

566. (485) Q2-673:

Which of the following statements is true:

1) Cortical bone has a larger surface area than cancellous bone.

3) Cortical bone has higher metaboliCactivity than cancellous bone.

2) Cortical bone has a higher density than cancellous bone.

5) Cortical bone has a higher porosity than trabecular bone.

4) Cortical bone remodels more rapidly than cancellous bone.

Cortical bone is denser, less porous, and stiffer and stronger than cancellous bone. Cortical bone has less surface area, a slower metaboliCrate, and remodels slower than cancellous bone

■Correct Answer: Cortical bone has a higher density than cancellous bone.

567. (486) Q2-674:

Which of the following statements is not true regarding vitamin D metabolism:

1) Vitamim D is transformed into 25 hydroxy vitamin D in the liver.

3) 1,25 dihydroxy vitamin D is produced in the liver as a result of parathyroid hormone stimulation.

2) Vitamin D is synthesized initially from 7 dehydrocholesterol in the skin.

5) 1,25 dihydroxy vitamin D increases calcium absorption across the gut wall.

4) 25 hydroxy vitamin D has a longer half life than 1,25 dihydroxy vitamin D.

1,25 dihydroxy vitamin D is produced in the kidney, not the liver. Vitamin D is transformed into 25 hydroxy vitamin D in the liver. This metabolite has an approximate half-life of 3 days. Via parathyroid hormone stimulation, this metabolite is hydroxylated again in the kidney to form the active metabolite of vitamin D, namely 1,25 dihydroxy vitamin D. This form has a short half-life of approximately 8 hours

■Correct Answer: 1,25 dihydroxy vitamin D is produced in the liver as a result of parathyroid hormone stimulation.

568. (487) Q2-675:

Which of the following clinical findings is not associated with hyperparathyroidism:

1) Bone pain

3) PathologiCfractures

2) Brown tumors

5) Increased erythrocyte sedimentation rate and anemia

4) Renal stones

Features of hyperparathyroidism include bone pain, Brown tumors, pathologiCfractures, and kidney stones. Hypercalcemia and a low or normal phosphate level are also present. The parathyroid levels are high in patients with hyperparathyroidism.

An increased sedimentation rate and anemia are associated with multiple myeloma. Correct Answer: Increased erythrocyte sedimentation rate and anemia

569. (488) Q2-677:

During fracture repair systemiCas well as local factors come into play. Which of the following is considered a systemiCfactor in fracture healing:

1) Degree of vascular injury

3) Age

2) Degree of bone loss

5) Degree of immobilization

4) Type of bone affected

The degree of vascular injury is considered a local factor in fracture healing. Other such factors include degree of local trauma, type of bone affected, degree of bone loss, degree of immoblization, infection and local pathologiCconditions. SystemiCfactors include age of the patient, hormone function, functional activity, nerve function and nutritional state

■Correct Answer: Age

570. (489) Q2-678:

Linear elastiCtheory is used as model for real material behavior. All of the following are fundamental assumptions of this theory except:

1) Stress and strain are not proportional to each other.

3) The material is insensitive to the rate of load application.

2) Srain is reversible when the stress is removed.

5) Strain is dimensionless.

4) The proportionality constant is called elastiCmodulus.

One of the fundamental assumptions of linear elastiCtheory is that stress and strain are proportional to each other. The proportionality constant expressed by these two entities is the material's elastiCmodulus. Stress is the internal reaction of a material to an externally applied force distributed over the cross-section of the material. Strain is the internal deformations of a material in response to an applied stress

■Correct Answer: Stress and strain are not proportional to each other.

571. (490) Q2-679:

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

1) Callus formation during fracture healing

3) Cartilage degeneration in osteoarthritis

2) HeterotopiCbone formation

5) Perichondrial bone formation

4) EmbryoniClong bone development

Enchondral bone formation or ossification is bone formation on a cartilage module. Enchondral bone formation occurs in each of

the following scenarios: embryoniClong 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.

Intramembranous bone formation includes: flat bone development (pelvis, clavicle, and skull bones), bone formation during distraction osteogenesis, and perichondrial bone formation.

Correct Answer: Perichondrial bone formation

572. (491) Q2-680:

During chondrocyte maturation at the growth plate, an orderly sequence of morphologiCand biochemical changes occur. Which of the following statements regarding these changes is false:

1) Cells from the proliferating and upper hypertrophied zones are metabolically aerobically active and accumulate intracellular lipid and glycogen.

3) During hypertrophy of chondrocytes, the major proteoglycan produced is in the form of macromolecular complexes composed of aggrecan monomers bound noncovalently by a link glycoprotein to a hyaluroniCacid backbone filament.

2) Proliferating chondrocytes in the upper growth plate contribute to most of the increase in long bone length.

5) Indian hedgehog and PTHrP form a negative feedback loop.

4) Type X collagen is produced in abundant amounts during endochondral ossification in the zone of provisional calcification.

Proliferation of chondrocytes in the upper growth plate does contribute somewhat to longitudinal growth. However, it is the process of cell hypertrophy that contributes most to increases in long bone length

■Correct Answer: Proliferating chondrocytes in the upper growth plate contribute to most of the increase in long bone length.

573. (492) Q2-681:

Which of the following skeletal dysplasias is a result of a mutation in FGF receptor-3:

1) Multiple exostoses

3) Achondroplasia

2) Multiple epiphyseal dysplasia

5) Schmid metaphysial dysplasia

4) Pseudoachondroplasia

A mutation in the fibroblast growth factor (FGF) receptor-3, leads to achondroplastiCdwarfism. The other answers have corresponding genetiCdefects:

Multiple epiphyseal dysplasia â Cartilage oligomeriCmatrix protein (COMP) of type IX collagen (COL9A2) Pseudoachondroplasia â COMP

Schmid metaphyseal dysplasia â Type X collagen Multiple hereditary exostoses â EXT1 and EXT2 genes Correct Answer: Achondroplasia

574. (493) Q2-683:

Which of the following wear mechanisms is the worst possible situation:

1) Adhesive wear

3) Third body

2) Fatigue

5) Fretting

4) Corrosive wear

A third body or particle becomes trapped between the two surfaces or materials in contact. The particle often scratches the bearing surface and results in rapid generation of wear products and further degradation of the bearing surface

■Correct Answer: Third body

575. (494) Q2-685:

Which of the following statements inaccurately describes human bone as a biomaterial:

1) Bone is isotropic.

3) Bone's strength and elastiCmodulus are approximately proportional to the square of its density.

2) Bone is viscoelastic.

5) Bone remodels its structure to maintain overall resistance to loading while the material itself weakens.

4) Bone is a composite.

Bone is anisotropiCas the properties of the material vary with the direction of loading. This is true of most biologiCmaterials and thus makes them difficult, if not impossible, to fully categorize

■Correct Answer: Bone is isotropic.

576. (495) Q2-687:

All of the following are true regarding abrasion chondroplasty except:

1) The subchondral bone plate is penetrated, allowing the subjacent bone marrow communication with the synovial fluid compartment.

3) Incomplete integration of the fibrocartilaginous matrix with the adjacent normal cartilage matrix may occur impairing the tissue's resistance to shear stress.

2) The organized collagen fibril orientation of normal articular cartilage is usually achieved in over 70% of cases.

5) Patients must be nonweight bearing for 8-12 weeks after chondroplasty.

4) The procedure depends on the ability of mesenchymal stem cells located in the subchondral bone marrow to differentiate into fibrocartilaginous tissue.

This statement is false. The organized collagen fibril orientation of normal articular cartilage, with tangentially oriented fibrils at the surface layer and radially oriented fibrils in the deep layer, never develops after the abrasion chondroplasty

■Correct Answer: The organized collagen fibril orientation of normal articular cartilage is usually achieved in over 70% of cases.

577. (496) Q2-689:

Which of the following techniques used to repair articular surface defects does not involve the use of mesenchymal stem cells:

1) Abrasion chondroplasty

3) Autologous chondrocyte transplantation

2) Perichondral transplants

5) Realignment osteotomy and periochondral transplant

4) Mesenchymal stem cell transplantation

In this technique, a small amount of cartilage is harvested arthroscopically from a non-weight bearing articular surface and the chondrocytes isolated by collagenase digestion. The isolated cells are then expanded in tissue culture and suspended in a collagen gel carrier. The resultant chondrocyte population is then reimplanted in a second procedure under a periosteal flap used to cover the articular cartilage defect

■Correct Answer: Autologous chondrocyte transplantation

578. (497) Q2-692:

Which of the following statements regarding the healing potential of the anterior cruciate ligament (ACL) and medical collateral ligament (MCL) is false:

1) MCL fibril diameters are larger and more densely packed than ACL fibrils.

3) MCL fibroblasts proliferate less rapidly than ACL fibroblasts.

2) MCL cells are more spindle shaped with cytoplasmiCprocesses which are in contact with collagen, while ACL cells are more oval shaped and have ground substance between the cell and collagen fibrils.

5) Healing MCL has higher mRNA for pro-collagen expression than healing ACL.

4) MCL fibroblasts have increased expression of integrins on the cell surface as compared minimal integrin expression on healing

ACL cells.

This statement is false. MCL fibroblasts proliferate more rapidly than ACL fibroblasts and respond differently to growth factors

■Correct Answer: MCL fibroblasts proliferate less rapidly than ACL fibroblasts.

579. (498) Q2-694:

Of the four phases of fracture repair when fixation of any variety is used, which phase occurs rapidly and crosses gaps:

1) Primary response

3) Intramedullary callus formation

2) Extramedullary callus formation

5) Intramedullary callus and primary osteonal response

4) Primary osteonal response

The extramedullary callus formed in a fixed fracture develops rapidly, requires motion, crosses gaps and depends on soft tissue viability. Immobilization inhibits this process

■Correct Answer: Extramedullary callus formation

580. (499) Q2-696:

Which of the following cell type-cell function pairings is false:

1) Pre-osteoblasts â stem cell for osteoblasts

3) Ostecytes â maintain mineral homeostatsis

2) Osteoblasts â synthesize organiCmatrix

5) Osteoblasts â receptors for PTH

4) Osteoclasts â synthesize organiCmatrix

Osteoclasts resorb bone by attaching to the bone surface, releasing enzymes, and dissolve the organiCmineral phases of bone. Osteoclasts do not have hormone receptors

■Correct Answer: Osteoclasts â synthesize organiCmatrix

581. (500) Q2-697:

The following statements are all true regarding parathyroid hormone (PTH) function except:

1) Increases activity of hepatiChydroxylase for conversion to 25 (OH) Vitamin D

3) Stimulates production of 1, 25 dihydroxy Vitamin D in the kidney

2) Increases calcium retention in the kidney via increased excretion of phosphate

5) Indirectly increases bone resorption via 1,25 dihydroxy Vitamin D

4) Directly stimulates increased gut absorption of calcium

This statement is false. PTH indirectly stimulates increased gut absorption of calcium via its direct effect of increasing renal production of active Vitamin D

■Correct Answer: Directly stimulates increased gut absorption of calcium

582. (501) Q2-698:

Which of the following individuals has the highest dietary calcium requirement:

1) A healthy growing child

3) A healthy 60-year-old post-menopausal woman

2) A healthy pregnant 23-year-old woman

5) A healthy 29-year-old post-partum lactating mother

4) A healthy adolescent

A healthy child requires approximately 400-700 mg of dietary calcium per day. An adolescent requires approximately 1300 mg per day. An adult requires 500 mg dietary of calcium per day. A pregnant woman requires 1500 mg of dietary calcium per day to support her own needs and those of the growing fetus. A post-partum lactating mother requires the highest intake of dietary calcium at 2000 mg per day. A post-menopausal woman requires roughly 1500 mg per day

■Correct Answer: A healthy 29-year- old post-partum lactating mother

583. (502) Q2-699:

Which of the following is not a facilitator of calcium absorption:

1) Parathyroid hormone

3) GastriCpH

2) 1,25 dihydroxy Vitamin D

5) Achlorhydria

4) Ca:P ratio of 1:1 or 1:2

1,25 dihydroxy Vitamin D increases the absorption of calcium and phosphorus from the small intestine. A reduction of stomach acid decreases the absorption of calcium in the gut. Parathyroid hormone indirectly stimulates gut absorption by increasing the amount of 1,25 dihydroxy Vitamin D

■Correct Answer: Achlorhydria

584. (503) Q2-701:

Laboratory findings found in rickets and/or osteomalacia, include the following except:

1) Decreased urinary calcium

3) Decreased serum phosphorous

2) Normal or decreased serum calcium

5) Decreased alkaline phosphatase

4) Increased parathyroid hormone

Vitamin D deficiency results in osteomalacia. The lack of Vitamin D may be secondary to dietary deficiency, gastrointestinal complications, or renal insufficiency. With a Vitamin D deficiency, one sees the following:

Normal or decreased calcium Decreased serum phosphorus Increased serum alkaline phosphatase Increased serum parathyroid hormone

Decreased serum 1,25 dihydroxy Vitamin D Decreased urinary calcium

Correct Answer: Decreased alkaline phosphatase

585. (504) Q2-702:

Which of the following disease state-therapy pairs is correct:

1) Vitamin D deficiency â increased dietary phosphate and low intake of Vitamin D

3) Renal osteodystrophy â selective parathyroidectomy

2) Renal osteodystrophy â low calcium, high phospate diet.

5) Paget's disease â chroniCetidronate use

4) Vitamin D resistant rickets â high intake of Vitamin D and increased dietary calcium

Renal osteodystrophy is treated with increased dietary calcium, low dietary phosphate, selective use of calcium phosphate binders, and selective parathyroidectomy (neck exploration). Paget's disease cannot be treated with longterm etidronate because this first-generation diphosphonate inhibits bone resorption and formation

■Correct Answer: Renal osteodystrophy â selective parathyroidectomy

586. (505) Q2-703:

Which of the following is not a form of primary hyperparathyroidism:

1) Single parathyroid adenoma

3) Parathyroid hyperplasia

2) Renal osteodystrophy

5) Multiple parathyroid adenoma

4) Malignant parathyroid tumor

Primary hyperparathyroidism can be caused by single or multiple parathyroid adenomas, parathyroid hyperplasia, or a malignant parathyroid tumor. Secondary forms include renal osteodystrophy, Vitamin D deficiency, and age-related osteoporosis

■Correct Answer: Renal osteodystrophy

587. (719) Q2-980:

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:

1) First-degree injury (neuropraxia)

3) Third-degree

2) Second-degree (axonotmesis)

5) Fifth-degree

4) Fourth-degree

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 retained, 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

Correct Answer: First-degree injury (neuropraxia)

588. (721) Q2-982:

Which of the following terms is used to describe complete severance of a peripheral nerve with loss of the nerve trunk continuity:

1) First-degree injury (neuropraxia)

3) Third-degree

2) Second-degree (axonotmesis)

5) Fifth-degree

4) Fourth-degree

A fifth-degree injury refers to complete disruption of the nerve trunk.

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 maintained, 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 being 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

Correct Answer: Fifth-degree

589. (722) Q2-983:

Which of the following describes the sequence in which motor and sensory nerves fail in response to an injury:

1) Motor, proprioceptor, touch, temperature, and pain

3) Touch, proprioceptor, temperature, pain, and motor

2) Pain, proprioceptor, touch, temperature, and motor

5) Proprioceptor, touch, temperature, pain, and motor

4) Temperature, touch, temperature, motor, and pain

Motor and sensory nerves fail in the following sequence: Motor

Proprioceptor Touch Temperature Pain

Recovery is usually in the reverse order.

Correct Answer: Motor, proprioceptor, touch, temperature, and pain

590. (723) Q2-984:

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

1) Immediately following the injury

3) 2 to 5 weeks following injury

2) 7 to 10 days following injury

5) 12 weeks following injury

4) 6 to 8 weeks following injury

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 traumatiCnerve injury:

Timing ElectrophysiologiCabnormality

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 Correct Answer: 2 to 5 weeks following injury

591. (724) Q2-985:

Following a traumatiCnerve injury, in which time period would a physician find re-innervation of the affected muscles:

1) Immediately following the injury

3) 2 to 5 weeks following injury

2) 7 to 10 days following injury

5) 12 weeks following injury

4) 6 to 8 weeks following injury

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 traumatiCnerve injury:

Timing ElectrophysiologiCabnormality

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 Correct Answer: 6 to 8 weeks following injury

592. (725) Q2-986:

Which of the following collagen types accounts for 10% to 20% of the wet weight of articular cartilage:

1) Type I

3) Type V

2) Type II

5) Type XI

4) Type IX

Collagen type II is the most common type of collagen in articular cartilage. Other collagen types include: Type V

Type VI Type IX Type X Type XI

The major components of cartilage are: Water: 65% to 80%

Type II collagen:10% to 20%

Aggrecan: 4% to 7%

The minor components (< 5%) of cartilage are: Proteoglycans

Collagens â Types V, VI, IX, X, XI Link protein

Hyaluronate Fibronection Lipids

Correct Answer: Type II

593. (726) Q2-987:

The affinity of articular cartilage for water is most related to which of the following tissues:

1) Type II collagen

3) HydrophiliCnature of the proteoglycans

2) Type I collagen

5) Fibronectin

4) Link protein

The affinity of articular cartilage for water is most directly related to the hydrophiliCnature of the proteglycans. Proteoglycans attract water through two physicochemical mechanisms â Donnan osmotiCpressure and the electrostatiCrepulsive forces that are developed between the fixed negative charges along the proteoglycan molecules.

Correct Answer: HydrophiliCnature of the proteoglycans

594. (727) Q2-988:

In which of the following articular cartilage zones is the collagen fiber oriented in a random manner:

1) Superficial tangential zone

3) Deep zone

2) Middle zone

5) Calcified zone

4) Tidemark

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 (random) 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 apatitiCsalts

The tidemark separates the deep zone and calcified zone

■Correct Answer: Middle zone

595. (728) Q2-989:

In which of the following articular cartilage zones is the collagen fiber oriented perpendicularly to the articular surface:

1) Superficial tangential zone

3) Deep zone

2) Middle zone

5) Tidemark

4) Calcified zone

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 apatitiCsalts

The tidemark separates the deep zone and calcified zone

■Correct Answer: Deep zone

596. (729) Q2-990:

In which of the following articular cartilage zones are the collagen fibers oriented parallel to the articular cartilage surface:

1) Superficial tangential zone

3) C. Deep zone

2) B. Middle zone

5) E. Calcified zone

4) D. Tidemark

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 apatitiCsalts

The tidemark separates the deep zone and calcified zone

■Correct Answer: Superficial tangential zone

597. (730) Q2-991:

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

1) The superficial tangential zone and the middle zone

3) The superficial zone and the deep zone

2) The middle zone and the deep zone

5) The calcified cartilage zone and the subchondral bone zone

4) The deep zone and the calcified zone

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 apatitiCsalts

The tidemark separates the deep zone and calcified zone

■Correct Answer: The deep zone and the calcified zone

598. (731) Q2-992:

In which of the articular cartilage zones is the highest concentration of proteoglycans:

1) Superficial tangential zone

3) Deep zone

2) Middle zone

5) Tidemark

4) Calcified cartilage zone

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 apatitiCsalts

The tidemark separates the deep zone and calcified zone

■Correct Answer: Deep zone

599. (732) Q2-993:

In which of the following articular cartilage zones is the highest water content:

1) Superficial tangential zone

3) Deep zone

2) Middle zone

5) Tidemark

4) Calcified zone

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 c