Metabolic diseases of bone

Question 1

what is osteoporosis?

Answer 1

Refers to increased porosity of skeleton due to loss of organic bone matrix and minerals.

Question 2

what are the effects of osteoporosis?

osteoporosis results in what?

Answer 2

• decreased bone mass and density.
• decreased thickness of cortical and trabecular** bone.

fractures

Question 3

the risk of osteoporosis is based on what?

Answer 3

Risk of OP is based on peak bone mass (30 years, based on genetics, diet, exercise) and the rate of bone loss that follows thereafter.

• after 30 you lose 1% bone mass each year
  
  • lost faster if there is no exercise with weights, poor diet or less estrogen

Question 4

what are the most common forms of osteoporosis?

Answer 4

senile

postmenopausal

Question 5

what is Postmenopausal osteoporosis?

Answer 5

it occurs secondary to estrogen deficiency

Question 6

what are the normal effects of estrogen on bone?

Answer 6

• Stimulates OPG production
• Decreases production of M-CSF
• Decreases response of osteoclasts to RANK ligand.

Question 7

what is the normal net result of estrogen on bone?

Answer 7

• Decreased formation of osteoclasts
• Decreased bone resorption

Question 8

if there is estrogen deficiency there will be what?

Answer 8

• ↑production of IL-1 and TNF by monocytes causing
  
  • Increased activity of RANK ligand and M-CSF
    
    • increase osteoclast activity = bone loss

Question 9

what are the clinical findings of osteoporosis?

Answer 9

• Bone pain
• Weight bearing bones predisposed to #
  
  • Compression fractures of vertebral bodies (most common)
  • Colles’ fracture of distal radius.
  • fracture of femoral neck.
• Loss of height and kyphosis

Question 10

what test can you use to diagnose osteoporosis?

Answer 10

Dual energy X ray absorptiometry (DEXA) - to evaluate bone density

Question 11

what measures can be taken to prevent postmenopausal osteoporosis?

Answer 11

• weight bearing exercises: walking, not swimming
• calcium, vitamin D supplements
• estrogen replacement therapy (currently not recommended)

Question 12

what is the treatment for osteoporosis?

Answer 12

Bisphosphonates: induce apoptosis of osteoclasts.

Calcitonin: inhibits osteoclasts

Question 13

how do you differentiate between osteomalacia and osteoporosis?

Answer 13

in osteoporosis, these are normal: Serum calcium, phosphate, PTH and alkaline phosphatase

Question 14

What is Osteitis Fibrosa Cystica?

what is another name for this?

Answer 14

The cause is increased PTH

primary hyperparathyroidism:

• Parathyroid adenoma  ↑ PTH
• Parathyroid hyperplasia  ↑ PTH

secondary hyperparathyroidism:

• prolonged hypocalcemia (renal failure) increased PTH

von Recklinghausen disease of bone

Question 15

what characterizes Osteitis Fibrosa Cystica?

Answer 15

Wide spread osteolytic lesions.

Deformity , microfractures

Secondary hemorrhages with formation of cysts.

Question 16

in Osteitis Fibrosa Cystica, what do you look for?

Answer 16

“Brown tumor” of bone characterized by: Cystic spaces lined by multinucleated osteoclasts, filled with fibrous tissue, and with brown discoloration resulting from hemorrhage.

Question 17

what is rickets?

Answer 17

Cause is vitamin D deficiency in children

Question 18

what is osteomalacia?

Answer 18

Cause is vitamin D deficiency in adults

Question 19

Rickets and osteomalacia have what findings in common?

Answer 19

• Decreased mineralization of newly formed bone.
• Usually caused by deficiency or abnormal metabolism of vitamin D.

Question 20

what is Renal osteodystrophy?

how does it happen?

Answer 20

Osteomalacia secondary to chronic renal disease.

Chronic renal failure causes: Hypocalcemia

• Due to lack of conversion of inactive vitamin D into active vit.D
• Hypocalcemia results in secondary hyperparathyroidism
• PTH secretion stimulates osteoclast activity

Question 21

what is Osteomyelitis?

what is the most common cause?

Answer 21

Refers to inflammation of bone and bone marrow.

due to infections by: Pyogenic (pus forming) bacteria

(Pyogenic Osteomyelitis)

Question 22

Pyogenic Osteomyelitis usually occurs in who?

what bacteria can cause osteomyelitis?

Answer 22

children and young adults

1. Staphylococcus aureus* (most common cause 90%)
2. N gonorrhoeae: sexually active young adults
3. Salmonella: sickle cell disease
4. Pseudomonas : IV drug abusers, diabetics and puncture of foot through rubber footwear.
5. Pasturella multocida: cat or dog bite
6. Mycobacterium tuberculosis : involves spine ( Pott’s disease)

Question 23

what is this?

Answer 23

osteomyelitis

Question 24

what are the 3 routes these organisms use to reach the bone in osteomyelitis?

Answer 24

1. Hematogenous spread (most common) (Seeding of bone after bacteremia)
2. Direct inoculation
3. Spread from an adjacent site of infection

Question 25

in osteomyelitis, what are the bones affected in Infant and children?

Answer 25

tibia, femur, humerus (long bones)

Question 26

in osteomyelitis, what are the bones affected in Infant and adults?

Answer 26

(small bones) - vertebrae, pelvic bones

Question 27

What region of the bone affected in adult osteomyelitis?

Answer 27

epiphysis

Question 28

what are the 2 morphologies of osteomyelitis?

Answer 28

1. acute osteomyelitis: * look for cell death and pus formation. * Pus may reach the Periosteum forming a **_subperiosteal abscess._** * **_​if abscess ruptures = fluid drained into sinus tract_** * ​​neutrophils kill bone cells 2. Chronic osteomyelitis: * characterized by replacement of acute inflammatory cells * A sleeve of new bone formation may surround the infected necrotic area = involucrum

Question 29

what are the clinical findings of osteomyelitis?

Answer 29

* Fever and severe pain over the affected area. * reluctance to use affected extremities. * Localized area of tenderness * Erythema * Swelling

Question 30

investigations will reveal in osteomyelitis these findings?

Answer 30

* Leukocytosis * Raised ESR

Question 31

what investigations can you order for osteomyelitis?

Answer 31

* X ray: * Early stage (10 days) - may be normal * Slow periosteal elevation * Lytic focus of bone destruction with surrounding sclerosis. * Radionuclide bone scan: * Blood cultures : usually positve * Bone biopsy

Question 32

what is a complication of osteomyelitis?

Answer 32

* Draining Sinus tract to the skin surface * Danger of **Squamous cell carcinoma** developing at orifice of sinus tract. * Extension of infection to adjacent joint * **leads to pyogenic arthritis.** * septicemia and infective endocarditis

Question 33

what is Tuberculous Osteomyelitis?

Answer 33

Occurs secondary to tuberculous infection located elsewhere. * Active tuberculosis of lung. * TB of GIT and lymphnodes * **Characteristically occurs in:** **Vertebrae (Pott’s spine or disease)**

Question 34

what are the clinical findings in Tuberculous Osteomyelitis?

Answer 34

* **Back pain** * **Stiffness,** * Deformity (kyphosis) , * **Neurological abnormalities** (Pott’s paraplegia) * **Fever, night sweats and weight loss.**

Question 35

what will you find in histology in tuberculous osteomyelitis?

Answer 35

Granulomas with caseous necrosis on histology.

Question 36

1. what is the most common organism causing osteomyelitis? 2. what is the most common organism causing osteomyelitis in patients with sickle cell? 3. what is the most common organism causing osteomyelitis in patients with IV drug abusers? 4. what is the most common organism causing osteomyelitis in patients with dog and cat bites? 5. what is the most common organism causing osteomyelitis in patients with nail puncture through rubber footwear?

Answer 36

1. Staphylococcus aureus 2. Salmonella paratyphi\* 3. pseudomonas. 4. Pasteurella multocida (a gram negative rod) 5. pseudomonas\*