CTBS Processing Techniques 4 — Questions and Answers
Question 1: Which type of bone graft has both osteogenic AND osteoinductive AND osteoconductive properties?
- Demineralized bone matrix (DBM)
- Freeze-dried cortical allograft
- Fresh autograft (Correct answer)
- Synthetic hydroxyapatite scaffold
Correct answer: Fresh autograft
Fresh autograft is the only graft type possessing all three bone healing properties: osteogenic (viable cells), osteoinductive (BMPs), and osteoconductive (scaffold), making it the gold standard.
Question 2: In tissue bank processing, what is the purpose of performing a 'gram stain' during microbiological testing?
- To differentiate between Gram-positive and Gram-negative bacteria for early contamination detection (Correct answer)
- To identify fungal contamination in bone marrow aspirates
- To quantify total colony forming units per gram of tissue
- To detect mycobacterial contamination requiring acid-fast staining
Correct answer: To differentiate between Gram-positive and Gram-negative bacteria for early contamination detection
Gram staining rapidly differentiates Gram-positive from Gram-negative bacteria based on cell wall composition, providing early indication of bacterial contamination during processing.
Question 3: What is the primary concern with using high-dose gamma irradiation (> 25 kGy) to sterilize cortical bone allografts?
- Increased risk of prion transmission due to protein denaturation
- Significant reduction in compressive and torsional mechanical strength (Correct answer)
- Destruction of osteoinductive proteins rendering DBM ineffective
- Excessive heat generation causing protein coagulation in the bone
Correct answer: Significant reduction in compressive and torsional mechanical strength
High-dose gamma irradiation causes significant free radical-mediated damage to collagen cross-links, substantially reducing the compressive strength, fatigue resistance, and torsional properties of cortical bone.
Question 4: During processing of amniotic membrane allografts, which property must be preserved to maintain its clinical utility as a wound cover?
- Cellular viability of amniocytes and fibroblasts
- Intact basement membrane and collagen matrix with growth factors (Correct answer)
- High calcium content for structural rigidity
- Intact blood vessel network for revascularization
Correct answer: Intact basement membrane and collagen matrix with growth factors
The intact basement membrane and collagen matrix containing growth factors (EGF, FGF, TGF-β) are essential for the amniotic membrane's anti-inflammatory, anti-scarring, and wound healing properties.
Question 5: What does the term 'terminal sterilization' mean in tissue processing?
- Sterilization performed at the end of the donor's recovery procedure
- Sterilization applied to the final packaged product after all processing steps (Correct answer)
- The final antibiotic rinse step before lyophilization
- Sterilization of instruments used during tissue processing
Correct answer: Sterilization applied to the final packaged product after all processing steps
Terminal sterilization refers to the application of a sterilization process (e.g., gamma irradiation, electron beam) to the tissue in its final, sealed packaging after all other processing steps are complete.
Question 6: Which processing parameter is most critical to monitor and control during the cryopreservation of vascular allografts?
- pH of the nutrient culture medium during incubation
- Cooling rate during controlled-rate freezing (Correct answer)
- Osmolarity of the final packaging solution
- UV light exposure time during decontamination
Correct answer: Cooling rate during controlled-rate freezing
Controlled cooling rate during cryopreservation is critical to minimize intracellular ice crystal formation, which would damage endothelial cell membranes and compromise graft viability.
Question 7: What is the purpose of the 'secondary packaging' in tissue allograft processing?
- To provide direct contact with the tissue and maintain sterility of the graft surface
- To provide an additional barrier against contamination and allow for labeling (Correct answer)
- To contain the cryoprotectant solution in contact with the tissue
- To serve as the terminal sterilization container for radiation processing
Correct answer: To provide an additional barrier against contamination and allow for labeling
Secondary packaging provides an additional contamination barrier, structural protection, and serves as the surface for required labeling information while the primary package directly contacts the tissue.
CTBS Processing Techniques 4
Which type of bone graft has both osteogenic AND osteoinductive AND osteoconductive properties?