Bone and musculoskeletal allografts

Bone and musculoskeletal allografts are human bone, tendon, ligament, cartilage, meniscus, and fascia recovered from deceased (and occasionally living) donors and transplanted into another person to repair, replace, or reconstruct skeletal and soft-tissue defects.[1][2] They are used widely in orthopedic, spine, sports-medicine, dental, podiatric, and reconstructive surgery, where they restore structure, fill bone voids, promote new bone formation, and replace torn ligaments or damaged joint surfaces.[1][3] Musculoskeletal tissue is the highest-volume category of human tissue allograft: U.S. tissue banks distribute on the order of one to two million bone and connective-tissue grafts each year, and the U.S. Food and Drug Administration (FDA) reports that millions of musculoskeletal allografts have been distributed for transplantation since federal oversight began in the 1990s (figures as of 2026-06).[1][4][2]

Allografts are distinguished from autografts (tissue taken from and returned to the same patient) and from synthetic or animal-derived bone-graft substitutes.[3][5] Their recovery, screening, processing, and distribution in the United States are regulated by the FDA under FDA regulation of human tissue (HCT/Ps) and are governed in practice by the standards of the American Association of Tissue Banks (AATB), with recovery typically performed by tissue bank organizations and, frequently, organ donation recovery programs.[6][2]

Graft forms

Musculoskeletal allografts are supplied in several physical and biological forms, selected according to the mechanical and biological demands of the procedure.[3][5]

| Form | Description | Typical uses | |------|-------------|--------------| | Structural / cortical | Dense load-bearing cortical bone (e.g., femoral rings, struts, wedges, whole-segment grafts) providing immediate mechanical strength | Spinal interbody fusion, large bone-defect reconstruction, revision arthroplasty, tumor reconstruction[3][5] | | Cancellous chips / morselized | Spongy trabecular bone in chip or particulate form; highly porous scaffold incorporated more rapidly than cortical bone | Bone-void filling, fracture nonunion, cavitary defects, fusion augmentation[5][7] | | Demineralized bone matrix (DBM) | Bone treated with acid to remove the mineral phase, exposing collagen and growth factors such as bone morphogenetic proteins (BMPs); supplied as powder, gel, putty, or strips | Bone-void filling, spinal fusion, dental and periodontal grafting[7][8] | | Osteochondral allograft | A plug or shell of articular (hyaline) cartilage with attached subchondral bone, often transplanted fresh to preserve cartilage cell viability | Repair of larger focal cartilage defects of the knee and other joints[9][3] | | Tendon / ligament grafts | Soft-tissue grafts such as bone-patellar tendon-bone, Achilles tendon, tibialis, semitendinosus, and gracilis | Anterior cruciate ligament (ACL) and other ligament reconstruction[10][3] | | Meniscal allograft | Whole or segmental meniscus from a size-matched donor | Meniscal allograft transplantation in the meniscus-deficient knee[9] | | Fascia / soft-tissue sheets | Processed fascia lata and similar connective-tissue sheets | Reconstructive, urogynecologic, and soft-tissue procedures[1][2] |

DBM is regulated as a medical device when combined with carriers and is valued for combining a conductive scaffold with retained inductive growth factors.[7][8]

Biological function

The performance of a bone graft is described by three properties.[5][7]

• Osteoconduction is the provision of a passive three-dimensional scaffold that supports the ingrowth of blood vessels and host bone-forming cells, followed by gradual resorption and replacement with new bone. Cancellous allograft is more rapidly and completely incorporated than dense cortical allograft because of its greater porosity.[5][7]
• Osteoinduction is the recruitment and differentiation of host mesenchymal stem cells into bone-forming cells, driven by signaling proteins such as BMPs. Demineralization exposes these proteins, so DBM is considered both osteoconductive and osteoinductive.[7][8]
• Osteogenesis is the formation of new bone directly by living cells contained within the graft itself. This requires viable transplanted cells.[5][7]

Because processing (cleaning, freezing, freeze-drying, and irradiation) removes or kills cellular components, most bone allografts contain no living cells and are therefore generally not osteogenic; they function primarily as osteoconductive scaffolds and, in the case of DBM, may also be osteoinductive.[5][7] By contrast, fresh osteochondral allografts are deliberately kept hypothermically and transplanted within a limited window specifically to preserve viable chondrocytes in the cartilage layer.[9][3] Autograft is the only graft that reliably provides all three properties together, which is the principal biological argument for its use.[5][7]

Processing and sterilization

After recovery under aseptic conditions, musculoskeletal tissue is cleaned to remove blood, marrow, lipids, and cellular debris; shaped or machined into its final form; and preserved by deep freezing or freeze-drying (lyophilization).[6][11] Processing reduces but does not by itself guarantee elimination of microbial and viral contamination, and the steps chosen involve a tradeoff between sterility and the preservation of biological and mechanical properties.[11][12]

Terminal sterilization, where used, is most commonly performed with gamma irradiation or electron-beam (e-beam) irradiation. A dose near 25 kGy has historically been treated as a reference dose for sterilizing tissue grafts, but high doses degrade tissue: gamma radiation damages bone and tendon largely by cleaving the polypeptide chains of collagen, reducing strength and stiffness.[12][13] Studies have found bone-patellar tendon-bone grafts irradiated at 25 kGy to be significantly less stiff than non-irradiated controls, and some evidence suggests electron-beam treatment preserves biomechanical properties better than gamma irradiation at the same dose.[12][13] To limit this damage, many tissue banks use lower doses (for example, in the 5 to 15 kGy range) or rely on validated aseptic processing without terminal irradiation, accepting different sterility-assurance tradeoffs.[13][12] These choices mean that grafts intended chiefly for mechanical support and grafts intended to retain biological activity may be processed differently.[11][12]

Donor screening and FDA regulation

In the United States, bone and musculoskeletal allografts are human cells, tissues, and cellular and tissue-based products (HCT/Ps) regulated by the FDA under 21 CFR Part 1271.[6][14] The framework requires establishments that recover, process, store, or distribute tissue to register and list with the FDA; to make a documented donor-eligibility determination based on donor screening (medical and social history and physical assessment) and laboratory testing for relevant communicable-disease agents; and to follow Current Good Tissue Practice (CGTP), which mandates procedures and a quality program designed to prevent the introduction, transmission, or spread of communicable disease.[14][6] For conventional bone and connective-tissue allografts that are minimally manipulated and used for a homologous purpose, premarket licensure or approval is generally not required; oversight focuses on disease-transmission prevention.[14][6] Donor testing includes screening for agents such as HIV, hepatitis B and C, syphilis, and others, and donor-eligibility requirements apply to tissue recovered on or after May 25, 2005.[6][14] Further detail is given in FDA regulation of human tissue (HCT/Ps).

Disease transmission risk and historical incidents

The risk of disease transmission from properly screened, tested, and processed musculoskeletal allografts is low but not zero, and screening, testing, and processing have substantially reduced it over time.[1][11] Two clusters of events in the 1990s and early 2000s were central to tightening regulation and standards.

• Bacterial (clostridial) infections. Following the 2001 death of a 23-year-old man from Clostridium sordellii sepsis after receiving a contaminated allograft, the Centers for Disease Control and Prevention (CDC) investigated recovery, processing, and testing practices and identified a series of bacterial infections associated with musculoskeletal-tissue allografts, including cases caused by clostridia and cases linked to a single processor.[15][11] These events highlighted the dangers of inadequate disinfection of grafts distributed without terminal sterilization.[15][11]
• Viral transmission. Documented transmissions of HIV and hepatitis C virus (HCV) from tissue donors, including a widely reported 2002 case in which an antibody-negative (seronegative) donor transmitted HCV to multiple organ and tissue recipients before nucleic-acid testing was routine, demonstrated that antibody screening alone could miss recent infections.[16][11] In response, AATB added a requirement for nucleic-acid testing (NAT) for HIV and HCV in 2005, narrowing the window during which an infected donor could test negative.[11]

These incidents drove the modern combination of donor NAT, validated processing, and CGTP oversight that defines current practice.[11][14]

Autograft versus allograft

The clinical choice between autograft and allograft balances biological performance against morbidity, supply, and a small residual disease risk.[3][5]

| Consideration | Autograft | Allograft | |---------------|-----------|-----------| | Biological activity | Osteoconductive, osteoinductive, and osteogenic (contains living cells) | Osteoconductive; DBM may be osteoinductive; generally non-osteogenic after processing[5][7] | | Donor-site morbidity | Yes (pain, blood loss, infection, harvest-site complications) | None[3][5] | | Supply / quantity | Limited by what the patient can provide | Large and varied in size and shape[3][5] | | Operative time | Increased by harvest | Reduced (no harvest)[3][5] | | Disease transmission | Effectively none | Low but nonzero[1][11] | | Incorporation | Faster | Slower; depends on form and processing[5][7] |

In practice, allografts are favored when large or specifically shaped grafts are needed, when avoiding a second surgical site is important, or when ligament or osteochondral tissue is required, while autograft remains a reference standard where maximal biological activity is the priority.[3][5]

Ethics, consent, and accreditation

Recovery of musculoskeletal tissue from deceased donors depends on authorization, given by the donor before death (for example, through a donor registry) or by the legal next of kin, under the same consent and donation framework that governs organ donation.[1][2] Ethical practice requires informed authorization, respect for the donor and family, and transparency that recovered tissue may be processed by both nonprofit and for-profit entities and distributed for a range of surgical uses.[2][6]

The American Association of Tissue Banks (AATB) is the principal voluntary accrediting body for U.S. tissue banks. It sets consensus standards for donor screening, recovery, processing, and distribution, accredits member banks, and reports that AATB-accredited banks distribute the large majority of musculoskeletal tissue used in the United States.[6][2] AATB standards (such as the 2005 NAT requirement) have at times preceded or exceeded federal minimums, and AATB accreditation is widely used by surgeons and hospitals as a marker of tissue safety alongside FDA registration.[11][6]

See also

• Tissue bank
• FDA regulation of human tissue (HCT/Ps)
• Organ donation

References

• American Academy of Orthopaedic Surgeons (AAOS), OrthoInfo. "Bone and Tissue Transplantation." https://orthoinfo.aaos.org/en/treatment/bone-and-tissue-transplantation
• American Association of Tissue Banks (AATB). "What is Tissue Donation / About Tissue Banking." https://www.aatb.org/
• AAOS Information Statement. "Use of Musculoskeletal Tissue Allografts." https://www.aaos.org/globalassets/about/bylaws-library/information-statements/1011-use-of-musculoskeletal-tissue-allografts.pdf
• U.S. Food and Drug Administration. "Tissue & Tissue Products." https://www.fda.gov/vaccines-blood-biologics/tissue-tissue-products
• Roberts TT, Rosenbaum AJ. "Bone grafts, bone substitutes and orthobiologics: The bridging of nonunion." (osteoconduction/osteoinduction/osteogenesis overview); see also StatPearls "Bone Grafting." https://www.ncbi.nlm.nih.gov/books/NBK553092/
• U.S. Food and Drug Administration. "Regulation of Human Cells, Tissues, and Cellular and Tissue-Based Products (HCT/Ps) - Small Entity Compliance Guide." https://www.fda.gov/regulatory-information/search-fda-guidance-documents/regulation-human-cells-tissues-and-cellular-and-tissue-based-products-hctps-small-entity-compliance
• Sohn HS, Oh JK. "Review of bone graft and bone substitutes with an emphasis on fracture surgeries." Biomater Res. PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC6819172/
• Gruskin E, et al. "Demineralized bone matrix in bone repair: History and use." (DBM osteoinductivity / BMP exposure). https://pmc.ncbi.nlm.nih.gov/articles/PMC6819172/
• Sherman SL, et al. "The use of osteochondral allografts in the management of cartilage defects." PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC3535086/
• "Infections in Anterior Cruciate Ligament Reconstruction / allografts in ACL reconstruction." PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC3806177/
• Vangsness CT, et al. "Allograft Tissue Safety and Technology." PMC. https://pmc.ncbi.nlm.nih.gov/articles/PMC7151900/
• Hoburg A, et al. "High-dose electron beam sterilization of soft-tissue grafts maintains significantly improved biomechanical properties compared to standard gamma treatment." Cell Tissue Bank. https://link.springer.com/article/10.1007/s10561-014-9461-x
• Nguyen H, et al. "Reducing the radiation sterilization dose improves mechanical and biological quality while retaining sterility assurance levels of bone allografts." Bone / ScienceDirect. https://www.sciencedirect.com/science/article/abs/pii/S8756328213002986
• eCFR. "21 CFR Part 1271 - Human Cells, Tissues, and Cellular and Tissue-Based Products" (Subpart C donor eligibility; Subpart D Current Good Tissue Practice). https://www.ecfr.gov/current/title-21/chapter-I/subchapter-L/part-1271
• Kainer MA, et al. "Clostridium Infections Associated with Musculoskeletal-Tissue Allografts." N Engl J Med 2004;350:2564-2571. https://www.nejm.org/doi/full/10.1056/NEJMoa023222
• Tugwell BD, et al. "Transmission of Hepatitis C Virus to Several Organ and Tissue Recipients from an Antibody-Negative Donor." Ann Intern Med 2005;143:648-654. https://www.acpjournals.org/doi/10.7326/0003-4819-143-9-200511010-00008