Bone Disorders

Osteomalacia is issue with the _______ of bone

quality

Osteomalacia

impaired mineralization of the bone matrix see a lack of calcium hydroxyapatite and therefore is too much osteoid matrix (organic portion of bone)

Osteomalacia most often due to?

vitamin D deficiency

In children most often see osteomalacia plus ___________

rickets

Rickets

disruption at the growth plate

Osteoporosis is issue with the ________ of bone

quantity

Osteoporosis

decreased bone mineral density (BMD)

Osteopenia

T-score of -1.0 and -2.5

Osteoporosis due to?

increase resorption of bone compared to production; which increases the risk of fractures

Vitamin D is a _____ soluble vitamins and acts as a ___________

fat; hormone

Overall vitamin D function

maintain adequate plasma levels of calcium and phosphate

Overall vitamin D function in turn supports:

metabolic function, bone mineralization, and neuromuscular transmission

Vitamin D is produced from __________

cholesterol

Vitamin D is first converted by the ________ then the _________

liver; kidney

What is the most active form of Vitamin D?

1,25(OH)2D (calcitriol)

Calcitriol stimulates the expression of __________

RANKL

RANKL

important regulator of osteoclasts and enhances the intestinal absorption of calcium and phosphorus

What hormone controls the level of calcium in the blood?

PTH

What is the main source of Vitamin D?

solar UVB radiation (also dietary)

What all is involved of vitamin D metabolism?

skin, liver, kidney, GI, and bone

1 alpha-hydroxlase

involved in the last step of metabolism to the calcitriol

3 different mechanism that regulate 1 alpha-hydroxlase

-hypocalcemia

-hypophosphatemia

-increased serum calcitriol

Hypocalcemia

increase PTH which increases 1 alpha-hydroxlase

Hypophosphatemia

directly increases 1 alpha-hydroxlase

Increased serum calcitriol

decreases 1 alpha-hydroxlase

Calcitriol has effects on calcium and phosphate homeostasis via:

-increasing abs from intestines

-increasing abs of calcium from kidneys (with wasting of phosphate)

-PTH regulation of calcium

-stimulates osteoblasts

PTH regulation of calcium

induces pre-osteoclasts to mature into osteoclasts, dissolve bone, releases calcium

PTH final levels with vitamin D deficiency

calcium levels normal with low phosphate levels

Most common cause of osteomalacia/rickets

dietary vitamin D combined with lack of sun exposure (in US see GI disease/postsurgical state)

Less common causes of osteomalacia/rickets

inadequate calcium intake and hypophosphatemia

Osteomalacia and Rickets leads to poorly mineralized bone which leads to susceptibility to?

stress related changes, stress fractures, and deformities

Rickets clinical signs

looser zones, frontal bossing, and bowed legs

T/F? Most people with mild/moderate vitamin D deficiency are asymptomatic

true

Osteoporosis general information

-decreased bone max (-2.5)

-bone fragility and increased risk of fracture

-age and gender dependent (postmenopausal women)

-localized disuse

Peak bone mass

20-30s

Bone mass is primarily dictated by?

genetic factors

Bone mass maintenance involves a balance of bone __________ and ______

production; loss

7 factors that involved in bone loss

-mentrual function (estrogen loss, activate osteoclasts)

-hormones

-aging (diminished osteoblast)

-reduced physical activity (weight-baring important)

-nutrition

-smoking

-chronic disease

What hormones if low can lead to osteoporosis and high?

testosterone/estrogen; cortisol

Aging osteoporosis called?

"senile"

Three primary causes of osteoporosis

-idopathic

-postmenopausal

-senile

__________ bone affected to a greater degree with osteoporosis

trabecular

_________ fractures for osteoporosis around 50, and _________ at 70

vertebra; hip

Ways to forsee a fracture coming?

-previous fracture

-osteopenia (30-40% loss to see)

-DEXA

Stages of healing

1. impact

2. stage of inflammation

3. early reparative stage (soft callus)

4. late reparative stage (hard callus)

5. remodeling

Impact

-loss of bone intregrity

-periosteal stripping and hemorrhage

-hematoma allows for activation of osteoprogenitor cells

Chondroblasts form cartilage ___________

centrally

Osteoblasts proliferiaton at the __________

periphery

Simple (closed)

skin is intact

Compound (open)

communicates or communicated with the external environment (look for skin breaks; high risk of infection)

Displaced

not in alignment

Greenstick

partially through the bone (children)

Pathologic fractures

focally weakened, usually by tumor

Stress fracture cause

repetitive injury can lead to "acute" fracture

Overuse/fatigue

too much stress on normal bone

Insufficiency fracture

normal amount of stress on abnormal bone

Non-union of a fracture

inability to form solid bone across fracture (does not fully mature/ossify) or local causes (osteomyelitis/excessive motion)

Systemic causes of non-union

-diabetes

-malnutrition

-infection

-vascular insufficiency

OI

deficiency in production of normal type 1 collagen (most common inheirted disorder of connective tissue)

OI inheritance

autosomal dominant or sporadic mutation

OI clincial feature

too little bone; extreme skeletal fragility

There are ___ major subtypes of OI

4

DDX OI

child abuse

Other manifestations of OI

teeth, eye (blue sclera), ear, joint, and skin

Best imaging for AVN

MRI (plain film can be normal)

Common AVN sites (can occur anywhere though)

-femoral head (most common)

-Legg-Calve-Perthes (idopathic femoral head in children)

-proximal pole navicular (scaphoid)

-Kienbock disease (lunate)

-Kohlers (navicular bone in kids)

Pathogenesis of AVN

ischemia is the basic underlying cause

Causes/risk factors of AVN

-mechanical fracture

-mediations

-alcohol

-smoking

-SLE

-pregnancy

-thrombosis and embolism

-vessel injury

-idiopathic

Medication that can cause AVN

-corticosteroids

-bisphosphonates therapy (jaw)

AVN of femoral head

AVN is subcondronal initally then leads to secondary OA which causes a collapse

Osteochondritis dissecans

due to repetitive trauma or idiopathic; most commonly at the medial femoral condyle; can cause a loose body in the joint

If bone infarcts are in the medually cavity they are often ____________

asymptomatic

Osteomyelitis

inflammation of bone/marrow almost always secondary to infection

Pyrogenic osteomyelitis can be due to:

-hematogenous spread

-direct extension

-direct implantation

In adults pyrogenic osteomyelitis most commonly due to:

-diabetic infection of foot (most common)

-open fracture

-surgical procedure

Osteitis

inflammation of bone (non-infectious; lacks systemic symptoms)

What is the most common cause of osteomyelitis overall?

Staph A

Usually a ______ bacteria if spread hematogenously, and ______ if other routes of spread

single; multiple

What is teh most common cause of GU tract infection/IVDA

E coli, Pseudomonas, and Klebsiella

Sickle cell

salmonella infection

Stepping on a nail while wearing shoes

pseudomonas

What infections common in children?

group A and B strep, strep p, and kingella kingae

T/F? 10% of the time no organism can be found with osteomyelitis

false, 50%

Pathogenesis of osteomyelitis

staph A cells wall proteins bind to bone matrix components such as collagen, facilitating adherence (can see pus)

Pus can spread into the ________

periosteum

Dead bone forms ________

sequestrum

Sequestrum is surrounded by new bone called _________

involucrum (seen in chonic osteomyelitis)

Other signs of osteomyelitis

draining sinus and brodie abscess

If patients is less than 1 years old what can occur with osteomyelitis

spread to the joint space from physis, metaphysis, and epiphysis

In children what is more effected with osteomyelitis

metaphysis

In adults what is more effected with osteomyelitis

epiphyses and subchondral bone

Osteomyelitis is often dictated by?

osseous vascular circulation

Mycobacterial infection

more destructive and resistant to treatment (TB); may be present for years before DX

TB of spine

Pott Disease

Paget Disease

increased but disordered and structurally unsound bone mass

Paget caused by?

osteoclast dysfunction; caused by significant genetic component

3 stages of Paget

1. osteolytic

2. mixed osteolytic/osteoblastic

3. osteosclerotic burned out phase

Paget disease can affect any bone most likely?

bony pelvis, skull, long bone, and spine

Paget bone mass

increased overall but new bone is disordered, highly vascular (warmth of skin), and architecturally unsound

T/F? Paget disease is more often seen in African Americans

false