bone is composed of
minerals - Ca, P, Mg
Organic Matrix - type I collagen, proteoglycans, glycosaminoglycans
T/F there is separate venous drainage for cortex and medullary canal
true
osteoblasts
produce osteoid (unnmineralized bone matrix) on bone surface
osteocytes
osteoblasts that have been encased in mineral matrix
maintain bone matrix
osteoclasts
active in areas of bone remodeling
reside near bone surface
what are the 3 phases of bone healing
inflammation phase
repairative phase
remodeling phase
inflammatory phase
lasts about 2-3 weeks
death of osteocytes results in release of lysosomal enzymes
necrotic material at site of the fracture is source of inflammatory respose
repair phase
migration of osteoprogenitor cells - forms periosteal callus
angiogenesis - transient blood supply from surrounding soft tissue
deposition of Ca hydroxyapatite in matrix - callus mineralization
cartilage replaced by bone via endochondral ossification
remodeling phase
begins when fracture is bridged by callus
woven bone remodeled into lamellar bone via osteoclasts and osteoblasts
remodeling phase is directed by ______
stresses of weight bearing
types of bone healing
primary/direct
secondary/indirect
contact healing
primary bone healing
occurs with compression of bone ends under rigid fixation
no cartilaginous callus formed
gap healing
gap between fracture ends is < 1mm
granulation tissue at gap followed by transversely oriented lamellar bone
haversian remodeling occurs at ~ 3 weeks post stabilization
T/F primary bone healing outmoded in favor of secondary bone healing
True
exceptions: articular fractures and simple, stable fractures
secondary bone healing
fracture ends dont touch
micromotion at fracture promotes formation of callus
bone heals via mineralization of fibrocartilagenous callus into boney callus
biological osteosynthesis
secondary bone healing
fracture ends not compressed - protect surrounding soft tissue, protect blood supply
plates in bridging mode, external skeletal fixaition, interlocking nails
average fracture healing time
6-8 weeks
factors that affect bone healing
fracture configuration/severity
soft tissue damge
stability of repair
presence of infection
patient factors (age, weight, disposition, comorbities)
complience
what is required to assess bone healing
orthogonal radiographs
4 A's of evaluation
alignment
apposition
apparatus
activity
when does clinical union occur
when bone is strong enough that fixation is no longer necessary
what is a delayed union
healing is prolonged beyond normal expected time course
fracture lines remains evident with feathery/wooly ends
callus is visible but lacks appropriate mineralization
no sclerosis of bone ends
malunion
failure to re-establish normal function in face of healing
which malunions are the lease tolerated
roatation and lateral translation
viable nonunion
biologically active fracture with cartilage and fibrous tissue between fracture ends
nonviable nonunion
fracture ends are sclerotic with rounded bone edges and visible fracture gap (bone have blood supply)
dystrophic, necrotic, defect, atrophic
treatment options for delayed union
pre-emptive treatment is ideal - bone grafts, increased mechanical stiffness of implants, bone morphogenic protein
if delayed untion is anticipated - rechecks q 3-4 weeks
treatment options for non-union
rigid stabilization
removal of loose implants
encourage biologically active environment - graft, marrow, demineralized bone matrix, bone morphogenic proteins
remove non-viable bone
+/- amputation