What are the components that make up bone?
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)
Effects of aging on bone:
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.
Define: compound (open) fracture
sharp ends of bone protrude through skin, or some projectile penetrates the skin into fx site.
Define: closed fx
skin remains intact
Define: perforating fx (gunshot-bullet penetration)
fracture may involve loss of bone from the effect of high level energy at fracture site
Define: depressed or fissure fracture
sharply localized blow depresses a segment of the cortical bone below the level of surrounding bone (eg Skull fracture)
Define: greenstick fracture
fracture is on one side of the bone but does not tear the periosteum of the opposite side (occurs in children)
Define: Spiral fx
caused by opposite rotatory forces pulling on the bone
Define: oblique fx
fracture oriented at an angle >30 degrees
Define: Transverse fx
fracture is oriented at a right angle to axis (straight across)
Define: avulsion fx
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
Define: comminuted fx
involves multiple fracture fragments
Define: stress fx
results from stresses repeated with excessive frequency to a bone
Define: Pathological fx
arises in abnormal or diseased bones (carcinoma, infection, osteoporosis)
Discuss the stages of bone healing: stage 1
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**
Discuss the stages of bone healing: stage 2
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.
Discuss the stages of bone healing: stage 3
Remodeling or consolidation stage: callus is replaced by woven bone which then is replaced into lamellar bone, takes 1-4 yrs to complete
Conditions that have a negative effect on bone healing:
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
Effect of smoking on bone healing:
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.
Effect of nutrition on bone healing:
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)
Wolff's law and bone healing:
optimal stress is essential for bone strength during healing, lack of stress can decrease the strength
Define: closed reduction
use of casting or traction
Define: open reduction
surgical intervention using plates, screws, or other internal fixation devices
Define: rigid external fixation
combination of closed and open reduction using percutaneous pins and external stabilizing bars
Advantages of closed reduction:
No surgery, reduction of fx, shorter hospital stay (except traction)
Advantages and disadvantages of open reduction:
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
How does rigid fixation affect bone healing?
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.
What effects can internal fixation have on bone healing?
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.
List advantages of WB'ing activities after sustaining a fracture?
enhanced rehab (improved ROM), shorter hospital stay, and less overall post fracture morbidity
What is a Salter Harris fracture?
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.
Describe a radiological sign of a fracture of the radial head/neck:
Fat-pad signs show evidence of an effusion of the elbow. They are sensitive and absence can rule out a fracture.
What is the most common fx overlooked in the adult population?
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.
Role of ultrasound in tx of acute fx:
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.
What effect does bioelectric stimulation have on fracture healing?
convert fibrous connective tissue to bone, possible by stimulating mechanical stress.
Effect of NSAIDs on bone healing?
No well-defined answer, long term use may reduce normal bone healing
What are stress fx, and how do they occur?
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.
Signs of healing for stress fractures?
Resolution of tenderness with palpation and radiographic healing - bone sclerosis
What is the best imaging for detecting stress fractures?
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.
What is bone transplantation and why is it used?
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.
Treatments for nonunions?
Autogenous bone grafting with fixation, vascularized bone grafting, allo and autografts with PRP, bone morphogenic proteins BMP-2
Growth factor role: BMP
induces metaplasia of undifferentiated perivascular mesenchymal cells into osteoblasts
Growth factor role: PDGF
platelet derived growth factor is chemotactir for inflammatory cells at the fx site
Growth factor role: TGF-Beta
transforming growth factor-beta stimulates production of type II collagen and proteoglycans at the fx callus
Growth factor role: IGF II
insulin-like growth factor II stimulates type I collagen production and cellular proliferation