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

The forearm contains the anterior, dorsal, and mobile wad. The following muscles are located in each compartment: Mobile wad
Brachioradialis
Extensor carpi radialis brevis
Extensor carpi radialis longus
Volar compartment
Flexor carpi ulnaris
Flexor digitorum profundus Flexor digitorum superficialis Palmaris longus
Flexor carpi radialis
Flexor pollicis longus

Of the four compartments, the deep posterior compartment is the most difficult to release. The surgeon must release the soleus muscle from the tibia to decompress the deep posterior compartment.
The tibialis posterior muscle often has its own fascial sheath in the deep posterior compartment. When a surgeon releases the deep posterior compartment, this fascial sheath (if present) should be released.

Of the four compartments, the deep posterior compartment is the most difficult to release. The surgeon must release the soleus muscle from the tibia to decompress the deep posterior compartment.
The tibialis posterior muscle often has its own fascial sheath in the deep posterior compartment. When a surgeon releases the deep posterior compartment, this fascial sheath (if present) should be released.

In a study by Heckman and colleagues, the level of the fracture site is the region with the highest tissue pressure. This was found to be true in all four components. The highest pressures are located in the anterior and deep posterior components.Correct Answer: Anterior and deep posterior

C ompartment syndromes occur in approximately 5% to 10% of tibia fractures. Patients with tibia fractures have the highest risk of all fracture patients.
Adult fracture patients at risk for compartment syndrome include (in descending order): Tibia shaft fractures
Femoral shaft fractures
Both bone forearm fractures
Distal radius fractures
C hildren with fractures who are at risk include (in descending order): Tibial shaft fractures
Supracondylar humerus fractures
Both bone forearm fractures

In a study by Heckman and colleagues, the level of the fracture site is the region with the highest tissue pressure. This was found to be true in all four components. The highest pressures are located in the anterior and deep posterior components.

Aside from performing a fasciotomy, little can be done for patients with a compartment syndrome. Hypothermia, systemic corticosteroids, and anticoagulation therapy may increase muscle tolerance to ischemia.
Steroids and anticoagulation are not reasonable options because there is an impaired blood supply to the muscle (ie, these agents cannot enter the muscle). Hypothermia can be used to gain some time if immediate fasciotomy cannot be performed.

C ompartment syndromes are difficult to diagnose. It is important to diagnosis compartment syndrome before irreversible muscle and nerve damage occurs.
Pain out of proportion to the injury and pain with passive stretch are the most important subjective and objective findings before a compartment syndrome has fully developed. Pain will subside after a prolonged period of ischemia. The muscle and nerves in the compartment are no longer viable, and the pain will diminish.

Normal resting muscle tissue pressure is between 0 mm Hg and 8 mm Hg. Remember, if one squeezes the muscle or pushes on it, then the compartment pressure increases.
Normal tissues have adequate tissue perfusion with increases in compartment pressure to within 10 mm Hg of the diastolic pressure. In damaged tissue (eg, tibia fracture), perfusion can be impaired when the diastolic pressure reaches within 20 mm Hg of the diastolic pressure.
One should remember that hypotensive patients with extremity injuries are prone to compartment syndromes. Correct Answer: 0 mm Hg to 8 mm Hg

Normal tissues have adequate tissue perfusion with increases in compartment pressure to within 10 mm Hg of the diastolic pressure. In damaged tissue (eg, tibia fracture), perfusion can be impaired when the diastolic pressure reaches within 20 mm Hg of the diastolic pressure.
One should remember that hypotensive patients with extremity injuries are prone to compartment syndromes. Correct Answer: 20

Loss of nerve electrical conduction begins after 2 hours of complete ischemia. Peripheral nerves can tolerate up to 4 hours of complete ischemia. A neurapraxic (loss of conduction capability) injury usually recovers. After 8 hours of complete ischemia, nerves cannot recover.
Patients will lose the sense of pain in a compartment with total ischemia after 2 to 8 hours because there is no conduction to the nerve. One can expect little recovery once this painless state has occurred.

Skeletal muscle tolerates periods of complete muscle ischemia for 3 to 4 hours without irreversible damage. Variable recovery occurs with ischemia for 6 to 8 hours. When the period of ischemia is more than 8 hours, there is irreversible muscle damage. After 8 hours, the muscle cells degenerate and, grossly, the muscle contracts as the muscle cells are replaced with scar tissue and contracture may result.
Remember to let a tourniquet down after 2 hours of ischemia. One does not want to enter the tolerance period of 3 to 4 hours. Correct Answer: 8 to 10 hours

Skeletal muscle tolerates periods of complete muscle ischemia for 3 to 4 hours without irreversible damage. Variable recovery occurs with ischemia for 6 to 8 hours. When the period of ischemia is more than 8 hours, there is irreversible muscle damage. After 8 hours, the muscle cells degenerate and, grossly, the muscle contracts as the muscle cells are replaced with scar tissue and contracture may result.
Remember to let a tourniquet down after 2 hours of ischemia. One does not want to enter the tolerance period of 3 to 4 hours. Correct Answer: 3 to 4 hours

Locking plates have become a popular, effective method of stabilizing metaphyseal/epiphyseal fractures with comminution and short articular fragments.
Important biomechanical features of locking plates include1 :
Locked screws can function as individual blade plates in the distal fragment.
Locking plates can effectively serve as bridge plates, providing excellent fixation in short distal articular fragments. C ompression of the plate against the bone is less than that of conventional plating, resulting in less devascularization of the underlying cortex.
There is no toggling between the locked screws and the plate.
The pullout strength of a locked unicortical screw is approximately 60% of a standard bicortical screw. Locking plates are similar biomechanically to an external fixator.
Moment arms are less because the plate is closer to the bone's neutral axis than the connecting bar of the external fixator.

Locking plates have become a popular and effective method of stabilizing metaphyseal/epiphyseal fractures with comminution and short articular fragments.
Important biomechanical features of locking plates include:
locked screws can function as individual blade plates in the distal fragment locking plates can effective serve as bridge plates
excellent fixation in short distal articular fragments
compression of the plate against the bone is less than that of conventional plating less devascularization of the underlying cortex
there is no toggling between the locked screws and the plate
pullout strength of a locked unicortical screw is approximately 60% a standard bicortical screw
locking plates are similar biomechanically to an external fixator moment arms are less because the plate is closer to the bone's neutral axis than the connecting bar of the external fixator

Hemophilia A is transmitted by a sex-linked recessive inheritance pattern. Important points to remember:
Hemophilia A (classic hemophilia) Factor VIII deficiency
Sex-linked recessive trait
Incidence - 1/5000 live male births
25% of cases are sporadic (no family history) Hemophilia B (C hristmas disease)
Factor IX deficiency
Sex-linked recessive trait
Incidence - 1/30,000 live male births

Hemosiderin deposition leads to synovial hypertrophy, bone erosions, recurrent bleeding, and eventual destruction of the articular surfaces and arthrofibrosis.
Synovial A cells (surface layer phagocytic cells) ingest hemosiderin
Mixed inflammatory cell population
Lymphocytes Plasma cells Histiocytes
Leads to bone erosion from the thickened synovium

The âbystander effectâ is the death of neighbor untargeted tumor cells during cell-targeted suicide, whereby HSV thymine kinase gene targeted cells commit suicide by absorbing gancyclovir, a prodrug that is turned intracellularly into a toxic metabolite by the targeting gene through phosphorylation.Correct Answer: The death of neighbor untargeted tumor cells during cell-targeted suicide.

The defect in cleidocranial dysplasia involves C bfa1.
C bfa1 is a transcription factor (coded by the C bfa1 gene) that is necessary and sufficient for differentiation of cells into osteoblasts and facilitates chondrocyte differentiation during enchondral bone formation.
The other responses refer to:
Metaphyseal chondrodysplasia (Schmid type): Type X collagen Osteopetrosis: C arbonic anhydrase type II, proton pump Metaphyseal epiphyseal dysplasia: C artilage oligomeric protein Marfan's syndrome: Fibrillin

Achondroplasia is caused by a defect in FGF-3 receptor, resulting in an inhibition of chondrocyte proliferation in the proliferative zone of the physis. One possible theory is that this mutation results in a receptor that is active even without binding of the fibroblast growth factor ligand, thereby causing an overactive receptor. This is a gain of function mutation (Dietz).
The other responses refer to:
Metaphyseal chondrodysplasia (Schmid type): Type X collagen
Diastrophic dysplasia: Sulfate transporter gene Osteogenesis imperfecta: Type I collagen (C ol 1A1, 1A2) Marfanâs syndrome: Fibrillin

Pseudohypoparathyroidism (PHP) (Albright Hereditary Osteodystrophy [AHO]) - end organ insensitivity; in AHO, germline mutation that leads to loss of function of Galpha S (GNAS1); causes end-organ resistance to PTH (Zaleske).
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
3/. Other features
The other responses refer to:
Metaphyseal chondrodysplasia (Schmid type): Type X collagen
Diastrophic dysplasia: Sulfate transporter gene
Gaucher's disease: Beta glucosidase
Osteopetrosis: C arbonic anhydrase type II, proton pump

The defective gene (located on chromosome 15) in Marfan's syndrome encodes for fibrillin. Fibrillin is a structural component of elastin and contains microfibrils (Dietz).
Features of Marfan's syndrome include: Long, thin limbs (dolichostenomelia)
Pectus excavatum, carinatum
Scoliosis
High and narrow palate
Ectopia lentis
Dilation of the ascending aorta
Dural ectasia
The other responses refer to:
Achondroplasia: FGF-3 receptor
Diastrophic dysplasia: Sulfate transporter gene
C leidocranial dysplasia: C bfa1
Osteopetrosis: C arbonic anhydrase type II, proton pump

Four proteins that regulate osteoclast activation have been discovered:
1/. RANK binds to a receptor on osteoclast precursor cells and positively effects their final differentiation into osteoclasts.
2/. Osteoprotegerin is a soluble decoy receptor that resembles RANK and inhibits osteoclasts.
3/. Tumor necrosis factor-related activation induced cytokine (TRANC E)
4/. Osteoclast differentiation factor
Note:
C bfa1 is a transcription factor (coded by the C bfa1 gene) that is necessary and sufficient for differentiation of cells into osteoblasts and facilitates chondrocyte differentiation during enchondral bone formation.

Four proteins that regulate osteoclast activation have been discovered:
1/. RANK binds to a receptor on osteoclast precursor cells and positively effects their final differentiation into osteoclasts.
2/. Osteoprotegerin is a soluble decoy receptor that resembles RANK and inhibits osteoclasts.
3/. Tumor necrosis factor-related activation induced cytokine (TRANC E)
4/. Osteoclast differentiation factor
Note:
C bfa1 is a transcription factor (coded by the C bfa1 gene) that is necessary and sufficient for differentiation of cells into osteoblasts and facilitates chondrocyte differentiation during enchondral bone formation.

C ore binding factor alpha 1 (C bfa1) and its gene (Cbfa1) have been described as anabolic regulators of bone. C bfa1 is a transcription factor and is responsible for the differentiation of precursor cells into osteoblasts. It also enhances differentiation of chondrocytes during enchondral bone formation. When there is deficiency of C bfa1, there can be abnormal bone development as in cleidocranial dysplasia.

The human genome is composed of 30,000 unique genes. Each gene is composed of a promotor or regulator region, and a transcriptional or coding region. Regulatory proteins or transcription factors bind to the promoter region of the gene to signal the beginning of transcription of the DNA into RNA or repress the expression of the gene. The coding region contains both introns and exons. Exon sequences of the gene directly code for the proteins, and the introns are spacers. The intron sequences are enzymatically removed from the newly transcribed messenger RNA by a splicing mechanism.

The human genome is composed of 30,000 unique genes. Each gene is composed of a promotor or regulator region, and a transcriptional or coding region. Regulatory proteins or transcription factors bind to the promoter region of the gene to signal the beginning of transcription of the DNA into RNA or repress the expression of the gene. The coding region contains both introns and exons. Exon sequences of the gene directly code for the proteins, and the introns are spacers. The intron sequences are enzymatically removed from the newly transcribed messenger RNA by a splicing mechanism.

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-dominant conditions:
Achondroplasia Spondyloepiphyseal dysplasia Multiple epiphyseal dysplasia Marfan's syndrome
Ehlers-Danlos syndrome Osteogenesis imperfecta (I, IV) Multiple hereditary exostosis Polydactyly

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-dominant conditions: Achondroplasia
Spondyloepiphyseal dysplasia
Multiple epiphyseal dysplasia
Marfan's syndrome Ehlers-Danlos syndrome Osteogenesis imperfecta (I, IV) Multiple hereditary exostosis Polydactyly

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-dominant conditions: Achondroplasia
Spondyloepiphyseal dysplasia
Multiple epiphyseal dysplasia
Marfan's syndrome
Ehlers-Danlos syndrome Osteogenesis imperfecta (I, IV) Multiple hereditary exostosis Polydactyly

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-dominant conditions: Achondroplasia
Spondyloepiphyseal dysplasia
Multiple epiphyseal dysplasia
Marfan's syndrome Ehlers-Danlos syndrome Osteogenesis imperfecta (I, IV) Multiple hereditary exostosis Polydactyly

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-dominant conditions: Achondroplasia
Spondyloepiphyseal dysplasia
Multiple epiphyseal dysplasia
Marfan's syndrome Ehlers-Danlos syndrome Osteogenesis imperfecta (I, IV) Multiple hereditary exostosis Polydactyly

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-recessive conditions: Sickle cell disease
Osteogenesis imperfecta (Types II, III)
Hypophosphatasia Homocystinuria Gaucher's disease

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-recessive conditions:
Sickle cell disease
Osteogenesis imperfecta (Types II, III) Hypophosphatasia
Homocystinuria
Gaucher's disease

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-recessive conditions: Sickle cell disease
Osteogenesis imperfecta (Types II, III)
Hypophosphatasia Homocystinuria Gaucher's disease

Structural defects are usually transmitted by an autosomal-dominant pattern. In contrast, with metabolic or enzyme deficiencies, the condition is usually transmitted in an autosomal-recessive pattern.
Remember the major autosomal-recessive conditions: Sickle cell disease
Osteogenesis imperfecta (Types II, III)
Hypophosphatasia Homocystinuria Gaucher's disease

C ommon inheritance patterns that should be known for examinations:
Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive
Achondroplasia Sickle cell Hypophosphatemic rickets Hemophilia (A, B)
SED (congenital) OI (II, III) Duchennes muscular dystrophy
MED Hypophosphatasia Hunters syndrome
Marfanâs syndrome Homocystinuria SED (tarda)
Ehlers-Danlos syndrome Gaucherâs disease Beckerâs muscular dystrophy
Abbreviations: OI (I,IV)=Osteogenesis imperfecta, SED=Spondyloepiphyseal dysplasia, MED=Multiple epiphyseal dysplasia, MHE=Multiple hereditary exostosis

C ommon inheritance patterns are shown in the Table below:
Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive
Achondroplasia Sickle cell Hypophosphatemic rickets Hemophilia (A, B)
SED (congenital) OI (II, III) Duchennes muscular dystrophy
MED Hypophosphatasia Hunters syndrome
Marfanâs syndrome Homocystinuria SED (tarda)
Ehlers-Danlos syndrome Gaucherâs disease Beckerâs muscular dystrophy
Abbreviations: OI (I,IV)=Osteogenesis imperfecta, SED=Spondyloepiphyseal dysplasia, MED=Multiple epiphyseal dysplasia, MHE=Multiple hereditary exostosis

C ommon inheritance patterns that should be known for examinations:
Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive
Achondroplasia Sickle cell Hypophosphatemic rickets Hemophilia (A, B)
SED (congenital) OI (II, III) Duchennes muscular dystrophy
MED Hypophosphatasia Hunters syndrome
Marfanâs syndrome Homocystinuria SED (tarda)
Ehlers-Danlos syndrome Gaucherâs disease Beckerâs muscular dystrophy
Abbreviations: OI (I,IV)=Osteogenesis imperfecta, SED=Spondyloepiphyseal dysplasia, MED=Multiple epiphyseal dysplasia, MHE=Multiple hereditary exostosis

C ommon inheritance patterns that should be known for examinations:
Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive
Achondroplasia Sickle cell Hypophosphatemic rickets Hemophilia (A, B)
SED (congenital) OI (II, III) Duchennes muscular dystrophy
MED Hypophosphatasia Hunters syndrome
Marfanâs syndrome Homocystinuria SED (tarda)
Ehlers-Danlos syndrome Gaucherâs disease Beckerâs muscular dystrophy
Abbreviations: OI (I,IV)=Osteogenesis imperfecta, SED=Spondyloepiphyseal dysplasia, MED=Multiple epiphyseal dysplasia, MHE=Multiple hereditary exostosis

There is only one condition that must be remembered for examinations that is transmitted through an X-linked dominant pattern - hypophosphatemic rickets.
Remember: the conditions which are x-linked recessive
Hemophilia A, B - X-linked recessive
Duchennes muscular dystrophy - X-linked recessive Achondroplasia - Autosomal dominant Hypophosphatasia - Autosomal recessive

Achondroplasia has an autosomal-dominant pattern of inheritance. Structural problems are usually transmitted via autosomal- dominant pattern.
If an affected individual is married to an unaffected person, then the chance of transmission to the children is 50%. The other conditions have the following transmission pattern:
Hemophilia A, B - X-linked recessive
Duchennes muscular dystrophy - X-linked recessive Achondroplasia - Autosomal dominant Hypophosphatasia - Autosomal recessive

For autosomal dominant, if one parent is a heterozygote and the other is normal, then the risk of transmission is to 50% of the offspring. Because of the dominance of the allele, heterozygotes manifest the condition.
For autosomal recessive, parents are usually not affected because they are heterozygotes. The risk of transmission is to 25% of the offspring. The children must have both recessive alleles to be affected.

For autosomal dominant, if one parent is a heterozygote and the other is normal, then the risk of transmission is to 50% of the offspring. Because of the dominance of the allele, heterozygotes manifest the condition.
For autosomal recessive, parents are usually not affected because they are heterozygotes. The risk of transmission is to 25% of the offspring. The children must have both recessive alleles to be affected.
Because only one parent contains the gene, none of the children will be affected, although 25% of the children will carry the recessive gene.

For autosomal dominant, if one parent is a heterozygote and the other is normal, then the risk of transmission is to 50% of the offspring. Because of the dominance of the allele, heterozygotes manifest the condition.
For autosomal recessive, parents are usually not affected because they are heterozygotes. The risk of transmission is to 25% of the offspring. The children must have both recessive alleles to be affected.
Because only one parent contains the gene, none of the children will be affected, although 25% of the children will carry the recessive gene.