Orthopedics Hyperguide Review | Dr Hutaif General Ortho -...

The normal estimated age-related bone loss per year is 0.5%. After oophorectomy or during the first 6 to 8 years after menopause, bone loss can be as high as 2.0% to 3.0% per year

Estrogen deficiency results in increased bone resorption. An increase in IL-6 expression stimulates osteoclasts to resorb bone.
An increase in M-CSF and RANKL results in increased osteoclastiCactivity. OPG decreases osteoclastiCactivity as a decoy inhibitor of RANK

Osteoblasts have receptors for androgens. Although androgens prevent bone resorption and may increase bone mass, the process is not understood at this time

Corticosteroids decrease overall protein synthesis. In the intestines, corticosteroids decrease calcium-binding proteins, hence decreasing the absorption of calcium.
Corticosteroids:
Decrease overall protein synthesis
Increase calcium excretion in the kidney
Inhibit bone formation and absorption at high doses
With the above changes, a state of secondary hyperparathyroidism exists. Correct Answer: Inhibiting calcium absorption in the intestines

Osteoporosis is a condition in which there is a deficiency of bone mass and microarchitectural deterioration of bone tissue. Osteoporosis is defined as a bone mass that is more than 2.5 SD below the mean for age-matched controls. Patients are considered osteopeniCwith mild to moderate bone deficiency with a bone density of 1.0 to 2.5 SD

Type 1 osteoporosis is the most common form of osteoporosis and is found in women during postmenopausal years. Type 1 osteoporosis is related to estrogen deficiency rather than a problem in calcium intake or absorption.
Features of type 1 osteoporosis include: Female to male ratio is 6:1
High turnover osteoporosis
Bone loss rate of 2% to 3% per year for 6 to 10 years following menopause
Trabecular bone is most affected
Related to estrogen deficiency rather than calcium intake

Type 1 osteoporosis is the most common form of osteoporosis and is found in women during postmenopausal years. Type 1 osteoporosis is related to estrogen deficiency rather than a problem in calcium intake or absorption.
Features of type 1 osteoporosis include:
Female to male ratio is 6:1
High turnover osteoporosis
Bone loss rate of 2% to 3% per year for 6 to 10 years following menopause
Trabecular bone is most affected
Related to estrogen deficiency rather than calcium intake
Type 2 osteoporosis, also called senile or involutional osteoporosis, is a low turnover osteoporosis and principally occurs in patients older than 75 years of age.
Features of type 2 osteoporosis include: Female to male ratio is 2:1
Patients older than 75 years of age
Low turnover osteoporosis
Trabecular and cortical bone affected
Associated with hip fractures
Related to a lifelong deficiency of calcium

Estrogen therapy is one of the main therapeutiCinterventions used to prevent osteoporosis in postmenopausal women. Features of estrogen interactions include:
Osteoblasts have estrogen receptors.
Estrogen indirectly affects calcium metabolism by modulating calcium absorption and renal excretion. Estrogen decreases osteoclast activity.
Estrogen prevents osteoporosis in 80% of postmenopausal women.
The protective effect of estrogren therapy ends when therapy is discontinued.

A new class of selective estrogen receptor modulator acts as an antagonist in breast tissue and an agonist in bone. Raloxifene selectively stimulates estrogen receptors in bone and is an antagonist in breast tissue.
Progestin used in conjunction with estrogen opposes the action of estrogen and lowers the risk of endometrial cancer that might occur with estrogen therapy alone.
Aredia, Fosamax, and alendronate are biphosphonates that inhibit osteoclasts, thereby decreasing bone resorption.Correct
Answer: Evista (raloxifene, Eli Lilly and Company)

Bisphosphonates are effective in the treatment of osteoporosis because they bind to the hydroxyapatite crystals and inhibit crystal resorption.
Other effects of bisphosphonates 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, alendronate decreases fracture rates (hip, spine, and wrist) by 50%. Bone mass gains are modest â 2%
to 4% per year in the vertebra and 1% to 2% per year in the hip

The most significant side effect of biphosphonates is esophagitis and dyspepsia. Biphosphonates must be taken on an empty stomach with no oral intake for 30 minutes. In addition, patients should remain upright

Osteopetrosis is a rare disorder in which there is decreased osteoclastiCresorption of bone and cartilage with normal bone formation. There are a number of different forms of the condition.
The most common form of osteopetrosis is an autosomal dominant type with mild features (adult or tarda). Patients may have mild anemia, have one or more fractures, or be asymptomatic.
The juvenile form of osteopetrosis is a severe autosomal disorder. Children have multiple fractures, severe anemia, thrombocytopenia, and hepatosplenomegaly. Effected children are also immunocompromised

Interferon gamma-1 is the only treatment for osteopetrosis that is approved by the Food and Drug Administration

The proper sequence when listing common orthopediCbiomaterials in order of increasing modulus is:
ElastiCModulus Cancellous bone Polyethylene Methylmethacrylate Cortical bone Titanium alloy Stainless steel Cobalt chrome

The perichondrial ring of La Croix is the source of cells which differentiate into chondrocytes and results in latitudinal physeal enlargement.
The other answers refer to specifiCgrowth plate zones which have functions. The reserve zone is for matrix production and storage. The proliferative zone is for matrix production and cellular proliferation. The hypertrophiCzone contains the zone of maturation, degeneration, and provisional calcification.

The terminal hypertrophiCchondrocytes in the hypertrophiCzone produce Type X collagen. The appearance of Type X collagen heralds ossification. Remember that Type II collagen is the most abundant collagen in the hypertrophiCzone

Salter Harris Type I and II fractures occur through the zone of provisional calcification or through the hypertrophiCzone. The reserve and proliferative zone remain intact and growth can proceed normal after healing of the fracture

The major part of the blood supply of the spinal cord is provided by the medullary or radicular arteries. The only feeder for the lower thoraciCspinal cord is the greater medullary artery or artery of Adamkiwicz (T9-T11). One should remember that in the spine, the right-sided approach is preferred to avoid the aorta and segmental artery of Adamkiwicz

Enchondral bone formation or ossification is bone formation on a cartilage model. Enchondral bone formation occurs in 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 occurs in flat bone development (pelvis, clavicle, skull bones), bone formation during distraction osteogenesis, and perichondrial bone formation

Cortical bone has a much greater density than cancellous bone. Therefore, it is stiffer and stronger. Cortical bone has a higher density than cancellous bone, is organized into osteons and lamellae, has low surface area, lower metaboliCrate than cancellous bone, remodels through osteons, and accounts for much of the structural strength of bones.
Cancellous bone has a lower density than cortical bone, has an organization of lamellar bone, has a high surface area, higher metaboliCrate than cortical bone, remodels through surface cells, and transmits forces in subchondral location.

Cadet and colleagues studied the formation of cortical bone in the metaphyses of rabbits. They found that the metaphyseal cortical bone is formed by coalescence of enchondral trabecular bone.
Important points from this study include:
Metaphyseal cortical bone is formed by coalescence of enchondral trabecular bone. The coalescence is formed by an increased osteoblast surface.
The increased osteoblast surface is likely caused by factors from the periosteum.
The bone that is produced by the cells in the groove of Ranvier probably does not contribute to the metaphyseal cortical bone.

Important concepts to remember regarding signaling proteins include:
Indian hedgehog (IHH) and core binding factor alpha 1 (Cbfa1) influence embryoniCbone formation and fracture healing. Vascular endothelial growth factor (VEGF) plays a role in cartilage hypertrophy at the growth plate and during fracture healing.
Transforming growth factor-beta (TGF-B) and platelet derived growth factor (PDGF) are found in early fracture hematoma, and these factors modulate cell proliferation and differentiation.
Bone morphogenetiCprotein and interleukin 1 and 6 are expressed during cartilage formation. Correct Answer: Indian hedgehog (IHH) and core binding factor alpha 1 (Cbfa1)

Important concepts to remember regarding signaling proteins include:
Indian hedgehog (IHH) and core binding factor alpha 1 (Cbfa1) influence embryoniCbone formation and fracture healing. Vascular endothelial growth factor (VEGF) plays a role in cartilage hypertrophy at the growth plate and during fracture healing.
Transforming growth factor-beta (TGF-B) and platelet derived growth factor (PDGF) are found in early fracture hematoma, and these factors modulate cell proliferation and differentiation.
Bone morphogenetiCprotein and interleukin 1 and 6 are expressed during cartilage formation. Correct Answer: Transforming growth factor-beta (TGF-B) and platelet derived growth factor (PDGF)

Important concepts to remember regarding signaling proteins include:
Indian hedgehog (IHH) and core binding factor alpha 1 (Cbfa1) influence embryoniCbone formation and fracture healing. Vascular endothelial growth factor (VEGF) plays a role in cartilage hypertrophy at the growth plate and during fracture healing.
Transforming growth factor-beta (TGF-B) and platelet derived growth factor (PDGF) are found in early fracture hematoma, and these factors modulate cell proliferation and differentiation.
Bone morphogenetiCprotein and interleukin 1 and 6 are expressed during cartilage formation. Correct Answer: Vascular endothelial growth factor (VEGF)

In primary osteonal bone healing, osteoclasts cut channels across the bone contact sites and blood vessels, and osteoblasts fill in the gap with new bone.
To achieve osteonal healing, there must be an anatomiCreduction with rigid fixation, an adequate blood supply, and the amount of motion at the fracture site must be very small to none (very low strain levels).
Moderate-to-high strain levels occur if there is motion at the osteosynthesis site. This motion results from poor fixation (lack of rigidity) or excessive loading during the healing period. High strain levels in the gap favor the formation of granulation tissue rather than bone.

There are many factors that increase the rigidity of an external fixator, including: Increased pin diameter
Increased pin number Decreased bone-to-rod distance Increased pin group separation Separating half pins by 45°
Increasing the bone-to-rod distance decreases the rigidity of the system. The fracture gap is also important. The fracture gap should be minimized for excellent bone apposition.

Grafting materials may include osteoconductive and/or osteoinductive properties and osteoprogenitor cells.
Cancellous bone and vascularized bone graft are the only materials that have significant osteoconductive, osteoinductive, and osteoprogenitor cells.
Several materials are mainly osteoinductive. Remember the definition of osteoinductive and osteoconductive properties: Osteoinductive factors: Molecules that have the capability of inducing osteoblastiCprecursors to differentiate into mature bone
forming cells.
Osteoinductive factors (without significant osteoconductive properties) include growth factors such as BMP-2 and rhBMP-7 (OP-1, Stryker Biotech, Hopkinton, Mass) and demineralized bone matrix.
Osteoconductive factors: The ability of a porous material to provide a scaffold for new bone formation.
Osteoconductive materials (without significant osteoinductive properties) include ceramics such as coral-based hydroxyapatite graft substitutes, Norian skeletal repair system (Norian Corporation, Cupertino, Calif), and calcium sulfate pellets (Osteoset, Wright Medical Technology Inc., Arlington, Tenn).
Bone marrow has the potential of supplying osteoprogenitor cells but has little osteoinductive or osteoconductive properties. Correct Answer: Cancellous bone graft

Grafting materials may include osteoconductive and/or osteoinductive properties and osteoprogenitor cells.
Cancellous bone and vascularized bone graft are the only materials that have significant osteoconductive, osteoinductive, and osteoprogenitor cells.
Several materials are mainly osteoinductive. Remember the definition of osteoinductive and osteoconductive properties: Osteoinductive factors: Molecules that have the capability of inducing osteoblastiCprecursors to differentiate into mature bone
forming cells.
Osteoinductive factors (without significant osteoconductive properties) include growth factors such as BMP-2 and rhBMP-7 (OP-1, Stryker Biotech, Hopkinton, Mass) and demineralized bone matrix.
Osteoconductive factors: The ability of a porous material to provide a scaffold for new bone formation.
Osteoconductive materials (without significant osteoinductive properties) include ceramics such as coral-based hydroxyapatite graft substitutes, Norian skeletal repair system (Norian Corporation, Cupertino, Calif), and calcium sulfate pellets (Osteoset, Wright Medical Technology Inc., Arlington, Tenn).
Bone marrow has the potential of supplying osteoprogenitor cells but has little osteoinductive or osteoconductive properties. Correct Answer: Coral-based hydroxyapatite bone graft substitute

Grafting materials may include osteoconductive and/or osteoinductive properties and osteoprogenitor cells.
Cancellous bone and vascularized bone graft are the only materials that have significant osteoconductive, osteoinductive, and osteoprogenitor cells.
Several materials are mainly osteoinductive. Remember the definition of osteoinductive and osteoconductive properties: Osteoinductive factors: Molecules that have the capability of inducing osteoblastiCprecursors to differentiate into mature bone
forming cells.
Osteoinductive factors (without significant osteoconductive properties) include growth factors such as BMP-2 and rhBMP-7 (OP-1, Stryker Biotech, Hopkinton, Mass) and demineralized bone matrix.
Osteoconductive factors: The ability of a porous material to provide a scaffold for new bone formation.
Osteoconductive materials (without significant osteoinductive properties) include ceramics such as coral-based hydroxyapatite graft substitutes, Norian skeletal repair system (Norian Corporation, Cupertino, Calif), and calcium sulfate pellets (Osteoset, Wright Medical Technology Inc., Arlington, Tenn).
Bone marrow has the potential of supplying osteoprogenitor cells but has little osteoinductive or osteoconductive properties. Correct Answer: Recombinant bone morphogenetiCprotein-7 (rhBMP-7)

Gout is caused by the deposition of monosodium urate crystals in tissues, typically around joints. Common locations of gout include the great toe, heel, ankle, and knee. In approximately 50% of patients, the first affected location is the great toe. Gout commonly occurs inside a joint for two reasons - synovial fluid is a poorer solvent than plasma and lower temperatures (as in peripheral joints) favor crystallization.
Neutrophils ingest the crystals and release potent lysosomal enzymes. Punched lesions may be seen on radiographs in chroniCcases, and one can often see an overlying lip of cortex at the edge of the lesion.
Histologically, the tophi have several features: Acellular amorphous material
Macrophages
Foreign body giant cells
In this patient, the joint space is preserved on the plain radiographs. The biopsy specimen has the characteristiCfeatures of gout - acellular amorphous material, macrophages, and foreign body giant cells.

Gout is caused by the deposition of monosodium urate crystals in tissues, typically around joints. Common locations of gout include the great toe, heel, ankle, and knee. In approximately 50% of patients, the first affected location is the great toe. Gout commonly occurs inside a joint for two reasons - synovial fluid is a poorer solvent than plasma and lower temperatures (as in peripheral joints) favor crystallization.
Neutrophils ingest the crystals and release potent lysosomal enzymes. Punched lesions may be seen on radiographs in chroniCcases, and one can often see an overlying lip of cortex at the edge of the lesion.
Histologically, the tophi have several features: Acellular amorphous material
Macrophages
Foreign body giant cells
In this patient, the joint space is preserved on the plain radiographs. The biopsy specimen has the characteristiCfeatures of gout - acellular amorphous material, macrophages, and foreign body giant cells.
The treatment of gout includes nonsteroidal anti-inflammatory drugs and medications such as allopurinol and colchicines, which lower hyperuricemia.

Gout is caused by the deposition of monosodium urate crystals in tissues, typically around joints. Common locations of gout include the great toe, heel, ankle, and knee. In approximately 50% of patients, the first affected location is the great toe. Gout commonly occurs inside a joint for two reasons - synovial fluid is a poorer solvent than plasma and lower temperatures (as in peripheral joints) favor crystallization.
Neutrophils ingest the crystals and release potent lysosomal enzymes. Punched lesions may be seen on radiographs in chroniCcases, and one can often see an overlying lip of cortex at the edge of the lesion.
Histologically, the tophi have several features: Acellular amorphous material
Macrophages
Foreign body giant cells
In this patient, the joint space is preserved on the plain radiographs. The MRI scans show periarticular erosions. The biopsy specimen has the characteristiCfeatures of gout - acellular amorphous material, macrophages, and foreign body giant cells.

Gout is caused by the deposition of monosodium urate crystals in tissues, typically around joints. Common locations of gout include the great toe, heel, ankle, and knee. In approximately 50% of patients, the first affected location is the great toe. Gout commonly occurs inside a joint for two reasons - synovial fluid is a poorer solvent than plasma and lower temperatures (as in peripheral joints) favor crystallization.
Neutrophils ingest the crystals and release potent lysosomal enzymes. Punched lesions may be seen on radiographs in chroniCcases, and one can often see an overlying lip of cortex at the edge of the lesion.
Histologically, the tophi have several features: Acellular amorphous material
Macrophages
Foreign body giant cells
In this patient, the joint space is preserved on the plain radiographs. The biopsy specimen has the characteristiCfeatures of gout - acellular amorphous material, macrophages, and foreign body giant cells.
The treatment of gout includes nonsteroidal anti-inflammatory drugs and medications such as allopurinol and colchicines, which lower hyperuricemia.

The plain radiographs show a destructive lesion in the wrist in the distal radius and at the scaphotrapezial joint. The joint spaces are preserved. The histology shows the features of gout: acellular amorphous tissue, macrophages, and giant cells.
Gout is caused by the deposition of monosodium urate crystals in tissues typically around joints. Common locations include the great toe, heel, ankle, and knee. In approximately 50% of patients, the first attack is in the great toe. Gout commonly occurs inside a joint for two reasons:
The synovial fluid is a poorer solvent than plasma
Lower temperatures (as in peripheral joints) favor crystallization
Neutrophils ingest the crystals and then release potent lysosomal enzymes. Punched lesions may be seen on radiographs in chroniCcases. One can often see an overlying lip of cortex at the edge of the lesion.
Histologically, the tophi have several features: Acellular amorphous material
Macrophages
Foreign body giant cells

The plain radiographs show a destructive lesion in the wrist in the distal radius and at the scaphotrapezial joint. The joint spaces are preserved. The histology shows the features of gout: acellular amorphous tissue, macrophages, and giant cells.
Gout is caused by the deposition of monosodium urate crystals in tissues typically around joints. Common locations include the great toe, heel, ankle, and knee. In approximately 50% of patients, the first attack is in the great toe. Gout commonly occurs inside a joint for two reasons:
The synovial fluid is a poorer solvent than plasma
Lower temperatures (as in peripheral joints) favor crystallization
Neutrophils ingest the crystals and then release potent lysosomal enzymes. Histologically, the tophi have several features: Acellular amorphous material
Macrophages
Foreign body giant cells
The first line of treatment is nonsteroidal anti-inflammatory medications. Correct Answer: Nonsteroidal anti-inflammatory medications

Gout is caused by the deposition of monosodium urate crystals in tissues typically around joints. Common locations include the great toe, heel, ankle, and knee. In approximately 50% of patients, the first attack is in the great toe. Gout commonly occurs inside a joint for two reasons:
The synovial fluid is a poorer solvent than plasma
Lower temperatures (as in peripheral joints) favor crystallization
One should remember the following:
Gout is much more common in males (ratio of 20:1). An inability to excrete uriCacid is the primary cause.
Gout is very common in transplant patients taking cyclosporine. Serum uriCacid level is often normal in an acute attack.
Joint space is usually preserved on plain radiographs (early disease). Correct Answer: Gout is very common in heart transplant patients on cyclosporine.

The anteroposterior and lateral radiographs show thinned cortices and a gentle S-shaped curve of the tibia. The overall alignment of the tibia, as well as the physes, is normal. These are the radiographiCfeatures of osteogenesis imperfecta.
Child abuse, osteomalacia (rickets), osteopetrosis, and leukemia must be distinguished from osteogenesis imperfecta. In child abuse, multiple fractures are at different stages of healing. Osteomalacia has widened physes and osteopetrosis has marked bone sclerosis and absence of a medullary cavity. Patients with leukemia have lytiCdestructive lesions.
In osteogenesis imperfecta, the genetiCdefect involves type I collagen. Type I collagen is made up of two alpha-1 chains and one alpha-2 chain in a triple helix. Glycine is the smallest amino acid and is crucial for coiling of the triple helix. Mutations in the
glycine chain lead to severe forms of osteogenesis imperfecta.
One should also remember the Silence classification:
Type Inheritance Sclera Severity
I AD Blue Mild form, normal teeth
II AR Blue Lethal form, die early
III AR Normal Severe, progressively deforming
IV AD Normal Moderately severe
Biphosphonate therapy can be used to slow bone remodeling and increase bone mass. Correct Answer: Osteogenesis imperfecta

The anteroposterior and lateral radiographs show thinned cortices and a gentle S-shaped curve of the tibia. The overall alignment of the tibia, as well as the physes, is normal. These are the radiographiCfeatures of osteogenesis imperfecta.
In osteogenesis imperfecta, the genetiCdefect involves type I collagen. Type I collagen is made up of two alpha-1 chains and one alpha-2 chain in a triple helix. Glycine is the smallest amino acid and is crucial for coiling of the triple helix. Mutations in the
glycine chain lead to severe forms of osteogenesis imperfecta. One should also remember the Silence classification:
Type Inheritance Sclera Severity
I AD Blue Mild form, normal teeth
II AR Blue Lethal form, die early
III AR Normal Severe, progressively deforming
IV AD Normal Moderately severe
Biphosphonate therapy can be used to slow bone remodeling and increase bone mass. With regard to the incorrect choices:
FGF receptor 3 is associated with achondroplasia. Fibrillin is associated with Marfan's syndrome.
Type II collagen is associated with spondyloepiphyseal dsyplasia.
Cartilage oligomeriCmatrix protein is associated with pseudoachondroplasia. Correct Answer: Type I collagen

The anteroposterior and lateral radiographs show thinned cortices and a gentle S-shaped curve of the tibia. The overall alignment of the tibia, as well as the physes, is normal. These are the radiographiCfeatures of osteogenesis imperfecta.
In osteogenesis imperfecta, the genetiCdefect involves type I collagen. Type I collagen is made up of two alpha-1 chains and one alpha-2 chain in a triple helix. Glycine is the smallest amino acid and is crucial for coiling of the triple helix. Mutations in the
glycine chain lead to severe forms of osteogenesis imperfecta. One should also remember the Silence classification:
Type Inheritance Sclera Severity
I AD Blue Mild form, normal teeth
II AR Blue Lethal form, die early
III AR Normal Severe, progressively deforming
IV AD Normal Moderately severe
Biphosphonate therapy can be used to slow bone remodeling and increase bone mass. Correct Answer: Diphosphonate therapy

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