fracture healing = specialized type of wound healing with bone regeneration
incidence of delayed healing in USA = 5 to 10%
Causes
inadequate immobilization
distraction
repeated manipulations
excessive early motion
excessive periosteal stripping
other soft tissue damage
contamination/infection
anatomical structure e.g. NOF, scaphoid, talus
2 aspects
biological interventions
mechanical interventions
Biological enhancement
Local approaches
stimulate bone healing = osteogenic, osteoconductive, osteoinductive methods
Osteogenic methods
autogenous bone graft (Macewen 1881)
allograft
autogenous bone marrow graft
haematoma forms around graft
release of bio-active materials
necrosis of graft & an inflammatory response, development of a fibro-vascular stroma with host derived blood vessels & osteogenic precursor cells
graft is penetrated by osteoclasts - graft resorption
a few cells from the graft may survive but main function is osteoconductive properties + osteoinduction d/t factors which stimulate the local inflammatory response with # healing
cancellous graft allows more rapid revascularization & leads to better incorporation than cortical bone
bone of endochondral origin eg. tibia have > rate of revascularization compared to bone of membranous origin eg. iliac blade but must be securely fixed
once the graft is adherent to the host bed, fixation plays no further role
concern with allograft - infection, blood borne disease, histocompatibility.
bone marrow - contains osteogenic precursors
marrow derived mesenchymal cells in the future
Osteoconductive methods
supports the ingrowth of vascular tissue & osteogenic cells
Ca based ceramics - HA (marine coral), tricalcium phosphate
Ca-collagen grafts
bio-active glass
synthetic polymers - inorganic Ca & phosphate paste which is injected into the # site & hardens
Osteoinductive methods
process that supports formation of osteoprogenitor cells with the capacity for new bone formation
can get bone formation at extra-skeletal sites
BMP (bone morphogenic proteins)
fibroblast growth factors
platelet derived growth factor
transforming growth factor-beta
the above are growth factors
these are cytokines which modulate & regulate fracture healing
Systemic approaches
humoral factors
#’s heal faster & with more callus in head injuries
prostaglandins
anabolic effect, esp PGE2
effect blocked by indocid ie. anti-prostaglandin
circulating osteogenic substances
Mechanical enhancement
Rx of a fresh # may differ from the Rx of a non-union
# healing is retarded by over-distraction or instability
controlled micromotion or controlled rythmic distraction may enhance # healing
in general, motion at a # site will cause formation of callus: hypermotion = hypertrophic non union
Effects of weight bearing
Sarmiento - improved # healing
Some report no difference in healing with weight bearing
early stability improves blood flow, intra-medullary reaming + a tight fitting nail decreases blood flow
electrical stimulation - most research has been with non-unions, may be beneficial
electromagnetic stimulation - useful in delayed union