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Introduction
  • A material with either osteoconductive, osteoinductive, and/or osteogenic properties
    • autografts
    • allografts
    • demineralized bone matrix (DBM)
    • synthetics
    • bone morphogenetic protein (BMP)
    • stem cells
  • Epidemiology
    • incidence
      • almost 1 million bone grafting procedures performed in US each year, with a growth of almost 13% per year 
  • Indications
    • assist in healing of fractures, delayed unions, or nonunions
    • assist in arthrodeses and spinal fusions
    • replace bone defects from trauma or tumor
  • Resorption rates
    • relative resorption rates of bone graft substitutes
      • fastest to slowest
        • calcium sulfate > tricalcium phosphate > hydroxyapatite 
  • Outcomes
    • allograft retrieval
      • retrieval studies are helpful in understanding the body's response to allografts
      • 5 years after implantation, allograft articular cartilage is completely acellular - no donor or recipient chondrocytes will be present 
Properties
  • Bone graft has aspects of one or more of these three properties
    • osteoconductive 
      • material acts as a structural framework for bone growth
        • demineralized bone matrices (DBMs)
      • the various three-dimensional makeups of the material dictate the conductive properties
    • osteoinductive 
      • material contains factors that stimulate bone growth and induction of stem cells down a bone-forming lineage
        • bone morphogenetic protein (BMP) is most common from the transforming growth factor beta (TGF-B) superfamily
    • osteogenic
      • material directly provides cells that will produce bone including primitive mesenchymal stem cells, osteoblasts, and osteocytes 
        • mesenchymal stem cells can potentially differentiate down any cell line
        • osteoprogenitor cells differentiate to osteoblasts and then osteocytes
      • cancellous bone has a greater ability than cortical bone to form new bone due to its larger surface area
      • autologous bone graft (fresh autograft and bone marrow aspirate) is the only bone graft material that contains live mensenchymal precursor cells
Antigenicity
  • Allograft is a composite material and therefore has many potential antigens (cell surface glycoproteins)
    • Class I and Class II antigens on graft are recognized by host T lymphocytes and elicit an immune response
    • immunogenic cells are marrow-based, endothelium, and retinacular-activating cells
      • bone marrow cells elicit the greatest immune response
      • extracellular matrix also acts as an antigen 
        • type I collagen stimulates both humoral and cell-mediated responses
        • noncollagenous matrix (proteoglycans, osteocalcin)
    • hydroxyapatite has not been shown to elicit an immune response
      • primary rejection is cell-mediated related to the major histocompatibility complex (MHC) incompatibility
Overview
 
Types of Bone Graft
Autograft
Cancellous - Less structural support
- Greater osteoconduction
- Rapid incorporation via creeping substitution
Cortical

- Slower incorporation due to need to remodel existing Haversion canals
- Interstitial lamellae preserved
- Provides more structural support
- 25% of massive grafts sustain insufficiency fractures

Vascularized bone graft - Technically challenging with quicker union and cell preservation
- Examples include: free fibula strut graft (peroneal artery), free iliac crest (deep circumflex iliac arteries), distal radius used for scaphoid fx (1-2 intercompartmental superretinacular artery branch of radial artery)
Allograft
Fresh - Highest risk of disease transmission and immunogenicity 
- BMP preserved and therefore osteoinductive
Fresh frozen - Less immunogenicity than fresh
- BMP preserved and therefore osteoinductive
Freeze dried (croutons)
- Least immunogenic
- Least structural integrity
- BMP depleted  (purely osteoconductive)
- Lowest likelihood of viral transmission
Demineralized Bone Matrix
Grafton DBM - Osteoinductive and osteoconductive
- Contains: collagen, bone morphogenetic proteins, transforming growth factor-beta, residual calcium
- Does NOT contain mesenchymal precursor cells
Synthetics
Silicate based grafts

 

Aluminum oxide Alumina ceramic bonds bind to bone in response to stress and strain

Calcium phosphate grafts

- Osteoconduction and osteointegration
- Biodegrade very slowly
- Highest compressive strength 
- Many prepared as ceramics (heated to fuse into crystals)
- Examples include: tricalcium phosphate, Norian (Synthes), hydroxyapatitie (tradename Collagraft by Zimmer)
Calcium sulfate

- Osteoconductive
- Quick resorption   
- Examples include: OsteoSet (Wright medical)

Coralline hydroxyapatine - Calcium carbonate skeleton is converted to calcium phosphate via a thermoexchange process (Interpore)
Calcium carbonate - Chemically unaltered marine coral
- Osteoconductive
- Examples include: Biocora (Inoteb, france)
Bone Growth Factors
BMP
TGF-B
IGF-II
PDGF

see Rank-L and Bone Growth Factors topic

 
Autograft
  • Bone graft transferred from one body site to another in the same patient
  • Indications
    • gold standard
  • Properties
    • osteogenic, osteoinductive, and osteoconductive
    • least immunogenic 
    • cortical, cancellous, or corticocancellous
    • vascular or nonvascular
  • Donor sites
    • bone marrow aspirate
      • source of osteogenic mesenchymal precursor cells
      • iliac crest and vertebral body most common sites
      • variable number of cells depending on patient age
    • iliac crest is the most common site for autograft 
      • provides both cancellous and cortical graft
      • higher complication rate with anterior versus posterior harvesting 
      • 2% to 36% complication rate
        • blood loss and hematoma
        • injury to lateral femoral cutaneous or cluneal nerves
        • hernia formation
        • infection
        • fracture
        • cosmetic defect
        • chronic pain
    • fibula and ribs are most common sources of vascularized autografts
    • tibial metaphysis
Allograft
  • Bone graft obtained from a cadaver and inserted after processing
  • Most commonly used bone substitute
  • Properties
    • osteoconductive only due to lack of viable cells
      • the degree of osteoconduction available depends on the processing method (fresh, frozen, or freeze-dried) and type of graft (cortical or cancellous)
    • cortical, cancellous, corticocancellous, and osteoarticular (tumor surgery)
  • Osteoarticular allograft
    • immunogenic
    • preserved with glycerol or dimethyl sulfoxide (DMSO)
    • cryogenically preserved (few viable chondrocytes remain)
    • tissue-matched (syngeneic) grafts decrease immunogenicity
  • Processing methods
    • debridement of soft tissue, wash with ethanol (remove live cells), gamma irradiation (sterilization)
      • dose-dependent higher doses of irradiation kills bacteria and viruses but may impair biomechanical properties
    • fresh allograft
      • cleansing and processing removes cells and decreases the immune response improving incorporation
      • indications
        • rarely used due to disease transmission and immune response of recipient
    • frozen or freeze-dried
      • reduces immunogenicity while maintaining osteoconductive properties
      • reduces osteoinductive capabilities
      • shelf life
        • one year for fresh frozen stored at -20 degrees C
        • five years for fresh frozen stored at -70 degrees C
        • indefinite for freeze-dried
Demineralized bone matrix (DBM)
  • Acidic extraction of bone matrix from allograft 
    • removes the minerals and leaves the collagenous and noncollagenous structure and proteins
  • Properties
    • osteoconductive without structural support
    • minimally osteoinductive despite preservation of osteoinductive molecules
    • interproduct and interlot variability is common
Synthetics
  • Alternative to autografts and allografts
  • Various compositions available (see summary above)
  • Made in powder, pellet, or putty form
  • Properties
    • osteoconductive only 
  • Outcomes
    • Level I evidence shows that calcium-phosphate bone substitutes allow for bone defect filling, early rehabilitation, and prevention of articular subsidence in distal radius and tibial plateau fractures
Bone morphogenetic proteins (BMP)
  • Osteoinductive properties
    • stimulates undifferentiated perivascular mesenchymal cells to differentiate into osteoblasts through serine-threonine kinase receptors
  • rhBMP-2 and rhBMP-7 are FDA-approved for application in long bones and spine
  • Complications
    • under or overproduction of bone
    • inflammatory responses
    • early bone resorption
Reamer Aspirator Irrigator
  • Provides large volume of bone graft from intramedullary source  
    • femur (most common) 
    • tibia
  • Possible iatrogenic complications
    • femoral shaft fracture due to eccentric reaming
    • insertion site pain (hip abductors)
Graft Healing
 
 Stages of Graft Healing
Stage Characteristics
1. Inflammation Necrotic debris stimulates chemotaxis
2. Osteoblast differentiation Differentiates from mesenchymal precursor cells
3. Osteoinduction Stimulation of osteoblast and osteoclast function
4. Osteoconduction Bone forms around the new scaffold
5. Remodeling Continual process for years
 
Risks & Complications 
  • Disease Transmission
    • hepatitis B
      • risk of hepatitis B disease transmission in musculoskeletal fresh-frozen allograft transplantation is 1 in 63,000
    • hepatitis C
      • risk of hepatitis C disease transmission in musculoskeletal fresh-frozen allograft transplantation is 1 in 100,000 
    • HIV
      • risk of transmission of HIV in fresh-frozen allograft bone is 1 in 1,000,000
    • allografts are tested for HIV, HBV, HCV, HTLV-1, and syphilis 
  • Serous wound drainage
    • calcium sulfate bone graft substitute associated with increased serous wound drainage 
 

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Questions (12)

(OBQ12.266) Which of the following graft materials has the least potential to elicit an immune response? Review Topic

QID:4626
1

Fresh irradiated corticocancellous bulk allograft

16%

(549/3489)

2

Fresh frozen fibular strut allograft

1%

(46/3489)

3

Fresh frozen Achilles tendon allograft

2%

(67/3489)

4

Fresh Achilles tendon allograft

2%

(65/3489)

5

Freeze dried cancellous bone chips

78%

(2732/3489)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

Of the options listed, freeze dried cancellous allograft has the least potential to elicit an immune response. Remember, all allograft tissue has more of an immune response generating capability than autograft tissue, which has the least of any of these materials.

All allograft materials carry immunogenic properties, which decrease as the material is processed via the various sterilizing, freezing, or drying process(es). As the processing increases, the mechanical characteristics of the graft tends to decrease.

Ahlmann et al. compared the complications associated with harvesting iliac crest bone graft from the anterior crest and posterior crest. They found the rates of both minor complications (p = 0.006) and all complications (p = 0.004) were significantly higher after the anterior harvest procedures than they were after the posterior procedures. They recommend that iliac crest bone graft be harvested posteriorly whenever possible.

Incorrect Answers:
Answer 1: Most bone and soft tissue allografts undergo irradiation to remove bacteria or other infectious agents, but this does not prevent an immune response in itself.
Answer 2: Fresh frozen allografts have more immunogenic potential than freeze dried, but less than fresh materials. Fresh allograft is not typically utilized, as the processing of allograft (bone or soft tissue) provides the safety of minimizing infectious disease transmission.
Answer 3: Fresh frozen allografts have more immunogenic potential than freeze dried, but less than fresh materials. Thus fresh Achilles tendon allograft has the highest immunogenicity.
Answer 4: Fresh Achilles tendon allograft will elicit the greatest immunogenic response.


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(OBQ11.48) Which of the following is true of both calcium phosphate and calcium sulfate? Review Topic

QID:3471
1

They have high resistance to shear forces

4%

(56/1258)

2

They have high resistance to torsional forces

2%

(27/1258)

3

They are contraindicated in spinal fusion

7%

(89/1258)

4

They provide a scaffold for bone progenitor cells

84%

(1056/1258)

5

They are not biocompatible with stainless steel orthopedic implants

2%

(21/1258)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

Calcium phosphate and sulfate materials are biocompatible materials that are widely used in orthopedic surgery. They have low tensile and shear stress properties. They serve as osteoconductive void-fillers that prevent the in-growth of soft tissue and provide a suitable environment for bone healing.

Khan et al reviewed the key features of optimal bone graft substitutes. They concluded that one of three essential elements are needed: (1) osteoinductive factors, (2) osteoconductive capabilities and (3) osteogenic stem cells.

Legros reviewed calcium-based bone substitutes, describing their origins, compositions and physical forms. He highlighted their ability to promote cellular function and reviewed the three-dimensional geometry which allows them to bond to BMPs and become osteoinductive agents.

Bucholz reviewed synthetic bone grafts in depth. Synthetic porous substitutes have numerous advantages over autografts and allografts including their unlimited supply, easy sterilization, and storage. The relative advantages and disadvantages of ceramic implants as well as the indications and clinical experience of several of the synthetic bone grafts is reviewed.

Incorrect answers:
Answer 1: Both have low resistance to shear forces.
Answer 2: Both have low resistance to torsional forces.
Answer 3: Both are used in spinal fusion.
Answer 5: Both are used with stainless steel and titanium implants as they are highly biocompatible.


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(OBQ11.267) A 20-year-old male is involved in motor vehicle collision and sustains a depressed tibial plateau fracture. When performing surgery, if calcium sulfate is used as the primary bone substitute void filler, an increase in which of the following outcomes may be expected as compared to autograft? Review Topic

QID:3690
1

Increased complications due to serous drainage

60%

(1262/2114)

2

Improved clinical outcomes as shown by more rapid time to healing

4%

(92/2114)

3

Improved clinical outcomes as shown by SF-36 scores

3%

(60/2114)

4

Increased complications due to autoimmune reactions and graft rejection

2%

(49/2114)

5

Equivalent complication rates and clinical outcomes

30%

(640/2114)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

Calcium sulfate bone graft substitute has demonstrated an increased rate of serous drainage at the surgical site. Evidence examining the use of calcium sulfate in the treatment of bone nonunions revealed a significant failure rate, suggesting that this material, used in isolation, is not optimal to promote union in that setting.

Beuerlein and Mckee reviewed the literature, showing that calcium sulfate is an effective void filler in metaphyseal defects after impacted fracture reduction (calcaneus, tibial plateau) or simple bone cysts. However, they report that calcium sulfate is associated with serous wound drainage especially when used at subcutaneous sites and in amounts greater than 20ml.

Ziran et al present a series of 41 patients undergoing bone grafting for atrophic/avascular nonunions with adjunctive calcium sulfate-demineralized bone matrix (Allomatrix). Of the 41 patients, 13 (32%) had drainage that necessitated surgical procedures and 14 (34%) developed a deep infection.


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(OBQ10.166) Which of the following osteoconductive bone graft substitutes resorbs faster than the rate at which bone growth occurs? Review Topic

QID:3259
1

Coralline hydroxyapatite

4%

(87/2207)

2

Collagen-based matrix with hydroxyapatitie coating

7%

(165/2207)

3

Calcium phosphate

13%

(287/2207)

4

Calcium sulfate

69%

(1525/2207)

5

Tricalcium phosphate

6%

(138/2207)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

Calcium sulfate has a compressive strength similar to cancellous bone but resorbs quickly.

The review article by Hak discusses that calcium sulfate resorbs faster than bone growth occurs and is resorbed in 4-12 weeks. Tricalcium phospate, coralline hydroxyapatite, and collagen-based matrices with hydroxyapatite coating have compressive strengths similar to cancellous bone and can take 6 months to 10 years to fully resorb. Calcium phosphate has a compressive strength 4-10 times greater than cancellous bone and resorption takes approximately 1 year.

The article by Frankenburg et al reports the results of 70 dogs undergoing an osteotomy with subsequent allograft or calcium phosphate filling and were then sacrificed at interval times over a 4-month period. The osteotomies filled with allograft reached approximately 100% of the strength of the control tibiae by four weeks, whereas the tibiae that had been treated with cement reached their maximum load to failure by eight weeks. Tha authors found trends (no statistical signficance) showing stiffness, displacement at maximum load, and energy to failure was greater with the allograft but conclude that calcium phosphate is well tolerated and may be useful in difficult fractures.


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(OBQ09.175) You are planning surgery on a 54-year-old female with the tibial plateau fracture seen in figures A and B. After reduction of the joint surface you plan to fill the void with a bone-graft substitute to prevent joint collapse. Which of the following bone-graft substitutes disappears most quickly in vivo? Review Topic

QID:2988
FIGURES:
1

Collagen-based matrices

14%

(122/901)

2

Calcium phosphate

16%

(145/901)

3

Calcium sulfate

64%

(580/901)

4

Synthetic calcium sulfate and tri-phosphate mixture

2%

(22/901)

5

Coraline hydroxyapatite

3%

(28/901)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

Calcium sulfate disappears in vivo quickly, usually within 4-12 weeks. Calcium phosphate and coraline hydroxyapatite are resorbed slowly, somewhere between 1-10 years, depending on the manufacturer. Synthetics that combine calcium sulfate and phosphate resorb quicker than calcium phosphate but slower than calcium sulfate. Collagen-based matrices show quick resorption of the collegen but slow resorption of their hydroxyapatite coating. Walsh et al. examined the in vivo response of calcium sulfate pellets alone or in combination with autogenous bone graft in a sheep model. They found excellent bone formation in defects filled with calcium sulfate pellets. Immunostaining for various cytokines (BMP-2, BMP-7, PDGF, or TGF-beta) showed elevated levels in the newly formed bone. They proposed that the local environment acidity was responsible for breakdown of the calcium sulfate. Watson evaluated 8 patients with comminuted tibial metaphyseal fractures treated with an injectable calcium sulfate. They found that bone regrowth was observed in all patients and the bone substitute almost completely resorbed by 3 months. Bucholz reviewed the biochemical, biomechanical, and longevity characteristics of the common bone substitutes.


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(OBQ06.150) Which of the following bone graft substitutes has the fastest resorption characteristics? Review Topic

QID:336
1

Calcium sulfate

79%

(1309/1651)

2

Tricalcium phosphate

10%

(166/1651)

3

Hydroxyapatite

5%

(90/1651)

4

Fibular allograft

1%

(17/1651)

5

Cortical iliac crest autograft

4%

(62/1651)

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

Of the three bone graft substitutes listed (calcium sulfate, tricalcium phosphate, and hydroxyapatite), calcium sulfate has the fastest resorption characteristics. Fibular allograft and cortical iliac crest autograft are not considered bone graft substitutes.

Calcium sulfate, tricalcium phosphate, and hydroxyapatite are all "osteoconductive" bone graft substitutes, meaning that these implants provide a surface and structure that facilitates the attachment, migration, proliferation, differentiation and survival of osteogenic stem and progenitor cells. Each has different chemical, macro- and microstructural properties. Calcium sulfate (plaster of Paris) is a low-molecular weight soluble compound that must be implanted adjacent to viable periosteum to work. It is reabsorbed by a process of dissolution over a period of 5-7 weeks.

Jamali, et al., found that calcium sulphate was completely reabsorbed by 6 weeks. Tricalcium phosphate has compressive strength similar to cancellous bone, but is brittle and weak under tension and shear. It undergoes reabsorbtion via dissolution and fragmentation over 6-18 months; unfortunately less bone volume is produced than tricalcium phosphate absorbed. For this reason, it is used clinically as an adjunct with other less absorbable substitutes.

Moore et al discuss that hydroxyapatite forms the principle mineral content of bone. Synthetically, it is available in ceramic and non-ceramic forms as porous or solid, blocks or granules. HA has good compressive strength, but is weak in tension and shear and brittle making it fracture-prone in shock loading. Ceramic HA preparations are resistant to absorption in vivo, which occurs at 1-2% per year. Non-ceramic HA is more readily absorbed.


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(OBQ06.176) Iliac crest cancellous bone graft can be harvested from either the anterior or posterior aspect of the pelvis. When comparing these two locations, harvesting from the anterior iliac crest has which of the following? Review Topic

QID:362
1

Less severe postoperative pain at the surgical site

10%

(94/939)

2

Decreased postoperative gait abnormalities

14%

(136/939)

3

Increased complication rates as compared to posterior harvesting

56%

(527/939)

4

Decreased postoperative pain duration

8%

(73/939)

5

Increased cancellous bone graft density

11%

(105/939)

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

Autologous bone is used to help promote bone healing in fractures and to provide structural support for reconstructive surgery, and can be harvested from the iliac crest, femur, or other areas. The results of autologous bone grafting are more predictable than the use of xenografts, cadaveric allografts, or synthetic bone substitutes because autologous bone grafts provide osteoinductive and osteoconductive properties, are not immunogenic, and are usually well incorporated into the graft site.

Arrington et al reviewed 414 consecutive iliac crest harvest procedures and reported a 10% rate of minor complications and 5.8% of major complications (deep infection, nerve injuries, herniation, fractures, hematomas). They note that with proper surgical technique, the incidence of the complications can be minimized.

Ahlmann et al compared the morbidity related to the harvest of anterior iliac crest bone graft with that related to the harvest of posterior iliac crest bone graft and to determine differences in functional outcome. The rates of both minor complications (p = 0.006) and all complications (p = 0.004) were significantly higher after the anterior harvest procedures than they were after the posterior procedures. The postoperative pain at the donor site was significantly more severe (p = 0.0016) and of significantly greater duration (p = 0.0017) after the anterior harvests.


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(OBQ06.261) What is the approximate risk of transmission of HIV in fresh-frozen allograft bone? Review Topic

QID:272
1

1 in 10,000,000

13%

(49/370)

2

1 in 1,000,000

78%

(290/370)

3

1 in 100,000

7%

(25/370)

4

1 in 50,000

1%

(3/370)

5

1 in 10,000

1%

(2/370)

Select Answer to see Preferred Response

PREFERRED RESPONSE 2

Hepatitis C & B, HIV, TB, and other bacterial infections have been recognized as important transmissible diseases in tissue and organ transplants. Retrospective studies, beginning in 1992, have demonstrated the ability of bone allografts from donors infected with these pathogens to seroconvert recipients and ultimately transmit the disease.

The risk of viral transmission associated with blood properly screened for Hepatitis C is 1 in 100,000. Risk of transmission in Hepatitis B is 1 in 63,000, HIV is between 1 in 650,000 to 1 in 1,000,000 for blood transmission and allograft transmission rates are estimated by the blood transmission rates.

In a current concepts review, Tomford reviews the current literature regarding disease transmission in musculoskeletal allografts. Currently two cases of HIV transmission have been documented in the United States. Current molecular biological efforts towards identification of potential infectious agents in allografts have shown promise in the early identification and prevention of disease transmission.


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(OBQ06.273) Which of the following bone graft material contains live mesenchymal osteoblastic precursor cells? Review Topic

QID:284
1

Fresh-frozen allograft bone

2%

(10/437)

2

Recombinant bone morphogenic protein

4%

(17/437)

3

Demineralized bone matrix

0%

(1/437)

4

Autologous iliac crest marrow aspirate

91%

(399/437)

5

Calcium phosphate putty

1%

(5/437)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

Demineralized bone matrix is obtained from allograft bone using a process of acid extraction which yields a product containing much of the collagen and non-collagenous protein components of bone including BMP.

Demineralized bone matrix contains collagen, BMP, TGF-beta, residual Ca, but NOT mesenchymal precursor cells. Live precursor cells are removed from allograft during processing. Calcium phosphate cement does not contain living cells. The only bone graft material that contain these live precursor cells are those containing autologous marrow-fresh autograft or bone marrow aspirate (answer 4).


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Question COMMENTS (1)

(OBQ05.62) Which of the following groups correctly identifies serologic tests that are required by the American Association of Tissue Banks (AATB) for musculoskeletal tissue allografts? Review Topic

QID:948
1

Cytomegalovirus, Hepatitis A, Hepatitis B, Hepatitis C, HIV, Syphillis

13%

(36/282)

2

Cytomegalovirus, Hepatitis A, Hepatitis B, Hepatitis C, HIV

24%

(69/282)

3

Hepatitis A, Hepatitis B, Hepatitis C, HIV, Syphillis

5%

(15/282)

4

Hepatitis B, Hepatitis C, HIV, Syphillis

37%

(105/282)

5

Hepatitis B, Hepatitis C, HIV

20%

(57/282)

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

The American Association of Tissue Banks performs screening testing on all allografts in addition to screening patients medical history. Specific tests include: HIV, HBV, HCV, HTLV-I/II, and Syphilis (see www.aatb.org for more info on screening process).

Neither Cytomegalovirus (CMV) nor Hepatitis A is routinely tested for in the American Association of Tissue Banks for musculoskeletal tissue.


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(OBQ05.147) You are considering using a frozen allograft distal femoral condyle in your reconstruction of a massive giant-cell tumor of the knee. In counseling your patient regarding the risks of allografts, you explain that 5 years after transplantation, what percentage of donor chondrocytes will be present and viable in the allograft? Review Topic

QID:1033
1

1-5%

13%

(54/422)

2

6-20%

13%

(54/422)

3

21-50%

12%

(50/422)

4

greater than 50%

7%

(31/422)

5

None, by 5 years the allograft cartilage will be completely acellular

55%

(230/422)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

By 5 years, the allograft cartilage will be completely acellular, so there will be no residual donor chondrocytes.

Enneking et al. conducted both radiographic and histologic studies of sixteen massive retrieved human allografts four to sixty-five months after implantation. Analysis of the articular cartilage revealed no evidence that any chondrocytes had survived, even when the graft had been cryoprotected before it was preserved by freezing.


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Average 2.0 of 21 Ratings

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(OBQ04.274) Which of the following substances is most osteoinductive? Review Topic

QID:1379
1

Calcium phosphate

3%

(38/1343)

2

Hydroxyapatite

4%

(51/1343)

3

Xenograft collagen sheet

3%

(43/1343)

4

Cancellous allograft

2%

(28/1343)

5

Cancellous autograft

88%

(1183/1343)

Select Answer to see Preferred Response

PREFERRED RESPONSE 5

An ideal bone-graft substitute must provide scaffolding for osteoconduction as well as progenitor cells and growth factors for osteoinduction. Furthermore, the bone graft must be able to integrate with the host. Autogenous bone graft contains osteoblasts, endosteal osteoprogenitor cells capable of synthesizing new bone, and a structural matrix that acts as a scaffold, making it the gold standard for bone grafting. BMP-2 is a commonly utilized adjunct for grafting, and is inherently osteoinductive.

The referenced article by Buckwalter et al is a review on the biology of bone grafting which nicely defines the various osteoinductive and osteoconductive properties of the various bone graft options.


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