OCS: bone injury and repair

Question 1

What are the components that make up bone?

Answer 1

Cells: osteoblasts (build), osteoclasts (remove), osteocyte Ground substance: calcium phosphate (rigidity and hardness), glycosaminoglycans, and hyaluronic acid Fibrous tissue network: collagen (resists tensile stress), elastin (makes bone resilient)

Question 2

Effects of aging on bone:

Answer 2

Osteoporosis: calcium related loss of mass and density can be caused by hormonal regulation being less efficient (calcitonin). Kidneys, GI tract, and endocrine system decrease in function thereby decrease calcium metabolism.

Question 3

Define: compound (open) fracture

Answer 3

sharp ends of bone protrude through skin, or some projectile penetrates the skin into fx site.

Question 4

Define: closed fx

Answer 4

skin remains intact

Question 5

Define: perforating fx (gunshot-bullet penetration)

Answer 5

fracture may involve loss of bone from the effect of high level energy at fracture site

Question 6

Define: depressed or fissure fracture

Answer 6

sharply localized blow depresses a segment of the cortical bone below the level of surrounding bone (eg Skull fracture)

Question 7

Define: greenstick fracture

Answer 7

fracture is on one side of the bone but does not tear the periosteum of the opposite side (occurs in children)

Question 8

Define: Spiral fx

Answer 8

caused by opposite rotatory forces pulling on the bone

Question 9

Define: oblique fx

Answer 9

fracture oriented at an angle >30 degrees

Question 10

Define: Transverse fx

Answer 10

fracture is oriented at a right angle to axis (straight across)

Question 11

Define: avulsion fx

Answer 11

may be produced by sudden muscle contraction and piece of bone is pulled off, can also occur from traction on a ligamentous or capsular attachment

Question 12

Define: comminuted fx

Answer 12

involves multiple fracture fragments

Question 13

Define: stress fx

Answer 13

results from stresses repeated with excessive frequency to a bone

Question 14

Define: Pathological fx

Answer 14

arises in abnormal or diseased bones (carcinoma, infection, osteoporosis)

Question 15

Discuss the stages of bone healing: stage 1

Answer 15

Stage 1 (inflammatory phase, granulation stage, fracture stage, or clot stage): clot formation (1wk) and then macrophages start to remove the clot as granulation tissue forms in place of the clot (2wks) ** no clot formation with stress fracture**

Question 16

Discuss the stages of bone healing: stage 2

Answer 16

Reparative phase or callous stage: Soft callous forms and the begins to mineralize into a hard callous. This stage takes 4-16 wks to complete.

Question 17

Discuss the stages of bone healing: stage 3

Answer 17

Remodeling or consolidation stage: callus is replaced by woven bone which then is replaced into lamellar bone, takes 1-4 yrs to complete

Question 18

Conditions that have a negative effect on bone healing:

Answer 18

Technical: infection, poor reduction, distraction, repeated gross motion of fracture fragments, loss of blood supply Biological: vascular injury, failure to mineralize callus, scar and fat tissue forms instead of the callus, inability to replace woven bone into lamellar bone (children with osteogensis imperfecta) Misc: poor nutrition, alcohol abuse, smoking

Question 19

Effect of smoking on bone healing:

Answer 19

decrease in callous formation, increase in nonuniouns, decreased strength. Smoking and nicotine delay revascularization, inhibt cellular proliferation and function. Decreased callous strength = increased risk of fracture.

Question 20

Effect of nutrition on bone healing:

Answer 20

Calcium important for bone mass. Decreased bioactivity of calcium from high-fat/high fiber diets, large doses of zinc/vitamin A, and high protein diets (increases urinary excretion of calcium)

Question 21

Wolff’s law and bone healing:

Answer 21

optimal stress is essential for bone strength during healing, lack of stress can decrease the strength

Question 22

Define: closed reduction

Answer 22

use of casting or traction

Question 23

Define: open reduction

Answer 23

surgical intervention using plates, screws, or other internal fixation devices

Question 24

Define: rigid external fixation

Answer 24

combination of closed and open reduction using percutaneous pins and external stabilizing bars

Question 25

Advantages of closed reduction:

Answer 25

No surgery, reduction of fx, shorter hospital stay (except traction)

Question 26

Advantages and disadvantages of open reduction:

Answer 26

Advantage: prescise, early mobilization of joints, immediate stability with earlier return to full function Disadvantage: increased opportunity for infection, longer hospital stay, may require second procedure to remove metal devices

Question 27

How does rigid fixation affect bone healing? ## Footnote

Answer 27

There is no stimulus for the production of the external callus from the periosteum or internal callus (secondary bone healing). Instead Primary bone healing occurs directly between the cortex of the two fragments.

Question 28

What effects can internal fixation have on bone healing? ## Footnote

Answer 28

Improper placement or tightening of plates, screws, nut, or bolts may cause bone reabsorption because local stress concentration or decreased vascular perfusion. Plates that are too rigid may cause bone atrophy secondary to bone not percieving compressive forces. Secondary inflammatory response can lead to weakening of the bone and if the plate is left in stress in the plate bone interface can occur.

Question 29

List advantages of WB'ing activities after sustaining a fracture?

Answer 29

enhanced rehab (improved ROM), shorter hospital stay, and less overall post fracture morbidity

Question 30

What is a Salter Harris fracture?

Answer 30

This is a fracture of the epiphyseal (growth plate) which can be hard to detect on x-ray. This type of fracture can result in a growth disturbance.

Question 31

Describe a radiological sign of a fracture of the radial head/neck:

Answer 31

Fat-pad signs show evidence of an effusion of the elbow. They are sensitive and absence can rule out a fracture.

Question 32

What is the most common fx overlooked in the adult population?

Answer 32

Scaphoid fx, secondary to the wrist of avascular neucrosis with a scaphoid fx most physicians will elect to immobilze and tx as if all wrist injuries are a fx.

Question 33

Role of ultrasound in tx of acute fx:

Answer 33

Ultrasound may stimulate healing of nonunions with low intensity (.1-.5). May work by increasing the mechanical properties of the healing fracture callus by stimulating earlier synthesis of extracellular matrix proteins in cartilage.

Question 34

What effect does bioelectric stimulation have on fracture healing?

Answer 34

convert fibrous connective tissue to bone, possible by stimulating mechanical stress.

Question 35

Effect of NSAIDs on bone healing?

Answer 35

No well-defined answer, long term use may reduce normal bone healing

Question 36

What are stress fx, and how do they occur?

Answer 36

Response to sudden increase in physical activity of several weeks duration. May result from form or training error. Microscopic fractures that do not heal from day to day which progress to macroscopic bone failure. May present with pain with walking or running.

Question 37

Signs of healing for stress fractures?

Answer 37

Resolution of tenderness with palpation and radiographic healing - bone sclerosis

Question 38

What is the best imaging for detecting stress fractures?

Answer 38

MRI is considered the best; bone scans can show bone uptake as early as 72 hours but the disadvantage to a bone scan (radionucleotide) is high levels of radiation despite its accuracy; x-rays can be normal for up to 3-4 wks.

Question 39

What is bone transplantation and why is it used?

Answer 39

An aggressive surgical technique where diseased bone is excised and a caderveric allograft is transplanted. Used for bone tumors mainly in the femur. Prone to complications: refracture, infection, nonunion, and resorption of graft.

Question 40

Treatments for nonunions?

Answer 40

Autogenous bone grafting with fixation, vascularized bone grafting, allo and autografts with PRP, bone morphogenic proteins BMP-2

Question 41

Growth factor role: BMP

Answer 41

induces metaplasia of undifferentiated perivascular mesenchymal cells into osteoblasts

Question 42

Growth factor role: PDGF

Answer 42

platelet derived growth factor is chemotactir for inflammatory cells at the fx site

Question 43

Growth factor role: TGF-Beta

Answer 43

transforming growth factor-beta stimulates production of type II collagen and proteoglycans at the fx callus

Question 44

Growth factor role: IGF II

Answer 44

insulin-like growth factor II stimulates type I collagen production and cellular proliferation