BONE BANK
- gold standard is still autogenous bone graft – use of preserved allogenic bone graft is still controversial
- still advantages of allogenic over autogenic is
- no donor site morbidity, blood loss
- unlimited volume of graft
- from any bone – better structural property
- can be processed in variety of structural forms
- bone bank system : to provide on demand grafts which is sterile, non immunogenic, retaining biological and biochemical properties
Donor screening
- donors : cadavers or live donors
- screened for infectious diseases, malignancy, autoimmune diseases, major systemic illness
- death d/t unknown cause avoided
- ideal donor : healthy adult <55 yrs
Procurement of tissue
- cadaveric tissue : within 24 hrs of death
- live donors who under go surgical procedures or amputation
Tissue processing
- procedure
- screening
- placed in saline at 600C for 3 hrs
- bone pieces washed free of blood and marrow using jet lavage
- placed in 70% ethanol – to remove fat
- terminal sterilization with gamma radiation or ethylene oxide
- freeze dried for storage
- stored in -800C
- kept in polyethylene sleeve
- issued after all sterility test and culture report negative
- fresh frozen bone stronger and better structural graft than freeze dried bone
Chance of disease transmission
- HIV transmission is a concern
- screening mandatory
- preferable to do a second test to take care of window period
- removal of blood, freeze drying, ethanol, irradiation : all make risk to nil
Immunogenicity of bone allograft
- no tissue typing needed : removal of blood, freeze drying, irradiation
Uses of allograft
- segmental defects
- tumor defects
- osteotomy wedges
- revision THR and TKR
- spinal fusion
Dis adv
- time and source needed for screening, processing, distribution
- donor to donor variation in quality
- risk of bacterial or viral infections
- cost
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