Adult Orthopaedics

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Stress Strain Curves--Bone vs Steel:

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Bone composition:

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*Type I Collagen
*Mineral: Hydroxyappatite

*Cells
Osteoblasts
Osteoclasts
Osteocytes
Marrow cells

*Wolff’s law--bone remodeling

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bone anatomy terminology:

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cellular organization of normal bone:

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Types of bone:

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Woven vs Lamellar Bone:

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left- woven bone
right- lamellar bone

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right: osteon
left: macro view

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Osteon with Osteocytes

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Trabecular Bone (Cancellous or spongy bone)

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Type I Collagen:

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type 1 collagen

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hydroxyapatite:

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important!
ion reservoir

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OI:

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Osteogenesis imperfecta (fragile bone disease)

Mutation in Type I collagen gene

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-osteoblasts on left (normal)
-right: mitos and RER synthesizing osteoid in OBs

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left: osteoclasts
right: lysosymes with acid phosphatase eats away bone in bone remodeling

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*Bone Remodelling--Cutting cone
*OBs and OCs working together

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Bone Remodelling--Wolff’s Law:

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Osteopetrosis:

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Nonfunctional or absent osteoclasts

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Osteopetrosis
*erlenmeyer flask shape in middle pic
*treat with bone marrow transplant to replace OCs

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Giant Cell Tumor--Benign bone tumor
*overactive OCs; treat with "bone cement"

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Metastatic Disease in bone:

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"PT Barnum Loves Kids"--Prostate, Thyroid, Breast, Lung, Kidney are most common cancers.

*overactive OCs

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cancer that has metastasized to bone

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cancer that has metastasized to bone.

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pathophysiology of bone destruction in metastatic disease:

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-overactive OCs
-treat with bisphosphanates and other osteoclast treatments

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Treatment for diseases of osteoclasts:

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*Bisphosphonates
*Antibodies against RANK ligand
*Calcitonin

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osteoporosis vs. osteomalacia:

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osteoporosis= less bone mass
osteomalacia- same mass, lack of calcium

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Osteomalacia:

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Unable to mineralize osteoid
Widened osteoid seams seen histologically
vit D and Ca metabolism are involved, too

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summary of vit d metabolism:

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summary of Ca++ metabolism:

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Bone Mass vs Age:

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Osteoporosis:

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*Normal bone
*But, decreased bone mass (-2.5 SD)

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Bone mass determinants:

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*Genetics
*Age, Sex
*Diet
*Exercise
*Tobacco, caffeine
*Drugs (renal reabsorption, skin, liver, seizure meds, steroids)
*Endocrinologic disorders: diabetes, hypothyroisism, hyperparathyroidism, testosterone deficiency, estrogen deficiency
*Cancer: myeloma, diffuse metastatic disease

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Treatment for Diseases of Osteoblasts--Osteoporosis:

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*Anabolic Agents (stimulate osteoblasts)
-Hormone replacement therapy (HRT): Testosterone, estrogen
-FORTEO (teriparatide) recombinant human parathyroid hormone (1-34),

*Anti-catabolic (inhibit osteoclasts)
-Bisphosphonates
-Calcitonin

*Vit D, Calcium

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Diseases of osteoblasts:

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Osteoporosis
Bone forming tumors

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Angiogram of bone--highly vascularized

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blood supply of femoral head:

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*medial circumflex femoral a is main supply
*can get torn in injury

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hip injuries
right--dislocation; sequelae can be blood supply problems like AVN (~15% of pts get it)

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AVASCULAR NECROSIS (AVN)
right- subchondral fracture (dead bone beneath bone surface)

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AVN. ON MRI.

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AVN-Subchondral fracture

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AVN.
-dead bone in bottom left
-above dead bone, note appositional bone (new bone) being formed. Note OBs lined up.

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Etiology of AVN:

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*Idiopathic
*Alcohol
*Steroids
*Clotting disorder, Sickle Cell, Gaucher’s disease
*Post-traumatic: dislocation, fracture
*Pregnancy
*Pediatric: Slipped capital femoral epiphysis (SCFE), Perthes disease

*Decompression sickness
*Gout, Diabetes

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Geriatric hip fractures:

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*Epidemiology
-300,000/yr incidence decreasing
-75% female
-90% > 50 y.o.
45% femoral neck
45% intertrochanteric
10% subtrochanteric
-20% 1 year mortality
-Cost: billions

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Treatment of geriatric patient with a displaced femoral neck fracture:

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*Bone density
*Metabolic evaluation
-CBC, Vit D, Ca, Phos, TSH
*Risk factor assessment
*Nutrition consult
*Fall prevention
*Vit D, Ca, bisphosphonate
*Surgical reconstruction of hip:
-Internal fixation
-arthroplasty

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SURGICAL REPAIR OF FEMORAL NECK (intracapsular) FRACTURES

L: internal fixation (do if blood vessels not torn)
R: hemiarthroplasty (must do if blood vessels are torn)

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Intertrochanteric hip fracture:

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*Extracapsular
*Cancellous bone 6 weeks healing
*Compression hip screw or intramedullary rod

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#2: internal fixation of intertrochanteric fx
2-4 all show repairs of intertrochanteric fxs

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Subtrochanteric hip fractures:

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High forces
Cortical bone 3-4 months healing time
Intramedullary fixation (rod)

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Repairs of Subtrochanteric hip fractures

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Problems with fracture healing

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*Nonunion 1% --> bone grafts, additional operations
*Fracture stability
*Blood supply
*Nutrition
*Bone apposition
*Infection
*Bad luck