What is osteoporosis?
Reduction in trabecular bone mass leading to porous bone --> increased risk of fracture
What are the most common forms of osteoporosis?
Senile and postmenopausal
What is the pathogenesis of osteoporosis?
For post-menopausal, all these things are a result of decreased Estrogen
There is also a decrease in OPG that causes the increased osteoclast activity (due to dec regulation)
What does osteoporosis look like microscopically?
Normal bone (left) has thick trabeculae
Osteoporotic bone (right) has thinnned trabeculae
Describe estrogen's influence on bone? What cytokines are involved?
Estrogen increases osteoblast activity, decreases osteoclast activity
IL-1, IL-6, TNF modulate osteoclastogenesis (osteoclast differentiation, activation, life span, and function)
Estrogen inhibits secretions of these cytokines
What is the most common fracture in people with osteoporosis?
Proximal femoral fractures --> associated with high mortality rate
Gupta notes contradict. Other sources say vertebral fractures more common
What is osteomyelitis?
Infection of the bone, typically in children --> Most commonly bacterial
What does acute osteomyelitis look like microscopically?
Neutrophils for dayz all up in the bone
What are the symptoms and causes (3 patterns) of osteomyelitis?
Bone pain with signs of systemic infection
Caused by direct innoculation (bone trauma), contiguous spread (cellulitis), or hematogenous spread
What are the bacteria (6) associated with osteomyelitis and populations most commonly seen in?
Staph aureus --> most common cause (90%)
Nisseria gonorrhoeae --> sexually active young adults
Pasteurella --> Dog/cat bites
Salmonella (encapuslated) --> Sickle cell disease
Pseudomonas --> DM and IV drug abusers, step on nail
TB --> usually invovles vertebrae (Pott's disease)
What does osteomyelitis look like on X-ray
Lytic focus (sequestrum) surrounded by sclerosis (involcrum) on X-ray
What lab value will be very elevated in osteomyelitis?
ESR > 100mm/hr
Can also be seen in temporal arteritis and polymyalgia rheumatica
What is osteonecrosis/avascular necrosis?
Necrosis of bone and bone marrow due to ischemia
What are the causes of osteonecrosis?
2) Long-term steroid use
3) Sickle cell --> dactylitis
4) Alcohol abuse
5) Decompression sickness --> N2 emboli lodge in bones (Caisson disease)
What does osteonecrosis look like grossly?
Wedge shaped pale area of necrosis in bone
What does osteonecrosis look like microscopically in sickle cell?
Diffusely congested, hemorrhagic marrow during sickle cell crisis
What is Pagets disease of bone?
Imbalance between osteoclast and osteoblast activity --> osteoclasts are overactive
What is the bone localization of Pagets disease?
Localizes to one or more bones --> does not involve entire skeleton
What is the epidemiology of Pagets disease?
Usually pts in their 60s
If pt >40 and has isolated elevated AlkPhos, suspect Pagets
Familial link to chromosome 18
What are the three stages of Pagets disease?
2) Mixed osteoblastic-osteoclastic
What are the clinical features of Pagets disease?
1) Bone pain --> microfractures
2) Increased hat size --> skull is common site
3) Hearing loss --> Impingement on cranial nerve
4) Lion-like facies --> involvement of facial bones
5) Isolated elevated AlkPhos
What is seen on biopsy with Pagets disease?
Mosaic pattern of lamellar bone --> lots of pieces but none are fused
What is osteomalacia(adults)/Rickets(kids)?
Inadequate mineralization of bone due to low VitD ("kids need the D" - Jared Fogle) --> leads to weak bones and fracture
What lab findings are there in osteomalacia/Rickets?
1) Decreased serum calcium
2) Decreased serum phosphate
3) Increased PTH
4) Increased AlkPhos
What is the microscopic appearance of osteomalcia?
Surfaces of bony trabeculae (black) are covered by a layer of unmineralized osteoid (dark pink) --> van Kossa stain turns calcified tissue black
What are the clinical features of Rickets?
1) Pigeon-breast deformity --> inward bending ribs with anteriorly displaced sternum
2) Frontal bossing --> osteoid deposition on the skull
3) Rachitic rosary --> osteoid deposition at costochondral joints
4) Bowing of the legs
What is hyperparathyroidism?
Overactivity of parathyroid glands producing excess PTH
What are the causes of primary and secondary hyperparathyroidism?
Primary --> Hyperplasia or tumor of parathyroid glands
Secondary --> Prolonged hypocalcemia leading to lots of PTH
How does hyperparathyroidism effect bone?
Excess PTH detected by osteoblasts --> activate osteoclasts and bone is resorbed causing cyst-like brown tumors in bone
What does hyperparathyroidism look like microscopically in bone?
Brown tumors show fibroblasts mixed with osteoclasts and numerous activated osteoclasts (large, dark pink multinuclated cells) at the edge of trabecula
What is the bone disease associated with hyperparathyroidism called?
Osteitis fibrosa cystica - von Recklinghausen disease of bone
What is renal osteodystrophy?
Term to collectively describe skeletal changes associated with chronic renal disease – kidney fails to convert Vitamin D to active form
What is the pathogenesis of renal osteodystrophy?
Decreased VitD leads to reduced Ca2+ absoprtion from intestines --> hypocalcemia causes increased PTH and increased bone resportion
What is a bone fracture (don't fuck this up)?
A break in the continuity of bone
What are the types of fracture?
1) Closed (simple) --> doesn't penetrate skin
2) Open (compound) --> penetrates skin
3) Displaced --> separated in non-anatomic position
4) Pathologic --> bones fracture due to pathologic process (osteoporosis)
5) Spiral --> fracture from torque (child abuse)
If a patient has a compound fracture, what should you do before closing the wound?
Washout and give antibiotics to prevent infection
If a patient has a displaced fracture, what must you do before it can heal?
Must reduce the fracture back to anatomical position
What is a stress (hairline) fracture?
Fracture caused by repeated stress on a bone --> often weight bearing bones
What typically causes a scaphoid fracture?
Falling on an outstretched hand --> pain in the anatomical snuffbox
What is the necessary treatment in scaphoid fracture?
Splint the patient to prevent avascular necrosis
What causes a basillar skull fracture and how does it present?
Secondary to trauma
Presents as periorbital ecchymoses, mastoid ecchymoses, CSF leaking thorugh ears or nose (metallic, salty taste)
What fractures in children are suspected for non-accidental trauma?
1) Rib fracture
2) Spiral fractures (except Toddler's fracture of distal tibia)
3) Multiple fractures of different ages
4) Shaken baby syndrome causing subdural hematoma and retinal hemorrhage
What happens immediately after a bone fracture?
Hematoma fills fracture gap and surroudning area of bone-injury to provide framework --> allows platelets and inflammatory cells to do their part
One week after a fracture, what is happening?
1) New osteoprogenitor cells
2) Granulation tissue containing vessels and fibroblasts
3) Hematoma is removed
What happens 2-3 weeks after a fracture?
Early callus formation --> cannot support weight
What is the final stage of healing after a fracture?
Bony callus mineralizes so controlled weight bearing can be tolerated
What are some complications of a fracture?
1) Fat emboli
2) DVT and PE
3) Compartment syndrome --> Five Ps: Pain, Pallor, Paresthesias, Pulselessness, Paralysis