BONE GRAFTS AND BONE GRAFT SUBSTITUTES_124535.pptx

Bone grafts and bone grafts substitutes presentation applicable for surgical residents

1. BONE GRAFTS AND BONE GRAFT SUBSTITUTES DR EGBEWOLE

2. OUTLINE Introduction Indications Properties of bone graft Classification Bone graft incorporation Principles Bone graft substitutes Complications Future trends Conclusion

3. INTRODUCTION The human skeleton has a remarkable ability to regenerate itself after injury. Unfortunately, conditions for spontaneous bone healing are not always ideal despite adequate immobilization and internal fixations Modern bone grafts and bone substitutes attempt to facilitate and enhance the healing process when suboptimal conditions exist. The field of orthopaedic surgery has experienced unprecedented advancements with bone grafts and orthobiologics

4. INTRODUCTION Bone grafts are materials that assists and supports bone healing through its mechanical and/or biological properties Bone graft is defined as a piece of bone implanted in-between recipient’s bones so as to promote the healing of the bone as a result of their component properties(Nandi et al 2010) An autogenous bone graft was first used successfully in 1875 when Nussbaum harvested the ulna to correct skeletal defect.

5. INTRODUCTION Bone graft is the second most common graft surgery done Almost 1 million bone grafting procedures performed in the USA each year with a growth of almost 13% per year.

6. PROPERTIES OF BONE GRAFT OSTEOCONDUCTIVE; > Provides mechanical scaffold for new bone formation > Cancellous , cortical, substitutes OSTEOINDUCTIVE; > Provide factors that promotes differentiation of mesenchymal cells to form chondroblasts , osteoblasts and osteocytes. > Eg BMPs, GFs

7. PROPERTIES OF BONE GRAFTS OSTEOGENIC > Provides cells that are capable of in-vivo bone formation > Eg ; cancellous graft, bone marrow aspirate

8. INDICATIONS FOR STRUCTURAL STABILITY IN JOINT FUSION JOINT REPLACEMENTS FRACTURE HEALING ; > Acute; > Non-union; PSEUDOARTHROSIS BONE DEFECTS; in tumor or infections ESTABLISH LONG BONE CONTINUITY AID SCREW FIXATION IN OSTEOPOROTIC BONE

9. CLASSIFICATION BASED ON THE SOURCE ; Autograft Allograft Isograft Xenograft Bone Graft Substitute (BGS)

10. CLASSIFICATION BASED ON THE FORM ; Cortical Cancellous Corticocancellous Vascularised cortical

11. CLASSIFICATION Autograft ; - Gold standard , cheap - no immunogenecity nor disease transmission - limited harvest, donor site morbidity, ↑ OP time Osteogenic , osteoconductive and osteoinductive

12. CLASSIFICATION Autograft ; Cortical, cancellous , corticocancellous , vascularised Donor sites; iliac crest, fibula, ribs, tibia metaphysis, bone marrow aspirate Infections, chronic pain, hematoma, injury to neurovascular structures

13. CLASSIFICATION Autograft ; Cancellous bone autograft most common form of autologous bone graft High osteogenicity property Little structural support Incorporation by resorption and substitution Corticocancellous ; - Dual function- healing and support - Sources- Iliac crest and proximal tibia

14. CLASSIFICATION Autograft ; Cortical bone autograft Excellent structural integrity Limited osteogenic and osteoinductive potential Slower to incorporate Creeping substitution

15. CLASSIFICATION Autograft ; Vascularised bone autograft Theoretically, the ideal graft Requires preservation of its nutrient, metaphyseal or perforating vessels Osteocytes and osteoprogenitor cells preserved Incorporated by primary or secondary bone healing Free fibular strut grafts w ith peroneal artery, free iliac crest grafts with deep circumflex iliac artery branches

16. CLASSIFICATION Autograft ; Bone marrow aspirate autograft Less commonly employed osteoinductive No structural support Liquid form predisposes to seepage

17. CLASSIFICATION Allograft ; - No donor site morbidity, large amount available - Disease transmission - Immunogenic - Slow incorporation Bone harvested from human cadavers and processed

18. CLASSIFICATION Allograft ; Osteoconductive and osteoinductive Lack viable cells so not osteogenic About 200,000 cases done in the US High costs Infections Fresh, frozen or freeze-dried

19. CLASSIFICATION Allograft ; Cancellous allograft Form of small cuboid chips or croutons Used to pack osseous defects such as in THR associated retroacetabular osteolysis Little mechanical strength Osteoconductive Devoid of cells for osteogenesis

20. CLASSIFICATION Allograft ; Cortical allograft provide rigid support Commonly employed in spine procedures as they have resistance to compressive strength

21. CLASSIFICATION Allograft ; Demineralized bone matrix Acidic extraction of bone matrix from allograft Form of highly processed allograft consisting of collagens, non-collagenous proteins, BMPs and other growth factors Osteoinductive and osteoconductive Popular adjunct in spinal fusion procedures

22. CLASSIFICATION Xenograft ; - Harvested from one specie and implanted into a different specie - Sources; cow, pig - Highly immunogenic, hence abandoned

23. BONE GRAFT INCORPORATION Process of envelopment and interdigitation of donor bone tissue with new bone deposited at the recipient site Five stages

24. BONE GRAFT INCORPORATION 5 STAGES; > Haematoma formation > Inflammation > Re/Neo- vascularisation > Focal osteoclastic resorption > Osteoblastic new bone formation

25. GRAFT INCORPORATION VASCULARIZED GRAFTS ; Incorporation is similar to fracture healing. ALLOGENIC CANCELLOUS GRAFTS ; Incorporation similar to cancellous autograft , but with a more marked inflammatory phase. Less predictable, incomplete incorporation ALLOGENIC CORTICAL GRAFTS ; Similar to autogenous cortical graft, but slower and less overall ingrowth. Immunogenic destruction may occur

26. PRINCIPLES; Preoperative History Physical examination Investigation Indication met Type of graft needed Counseling and informed consent

27. PRINCIPLES; Intraoperative Anaesthesia , positioning; appropriate Antibiotics prophylaxis Graft site skin prep and draping Graft harvest precautions; ASIS, PSIS, down to bone, change gloves Recipient site/bed preparation Morselisation vs. Block Keep graft moist. Donor site haemostasis Stabilisation of the graft implanted

28. PRINCIPLES; Postoperative Pain management Monitor bleeding. Change dressing as needed Wound care Management of donor site morbidities Monitoring of graft incorporation

29. ALLOGRAFT PROCESSING/BONE BANKING Donor selection and consent Donor screening; > Medical and behavioural history > Blood tests (Hepatitis B and C, HIV, Syphilis, Rhesus) Exclusion criteria; > Infection (HIV, Hepatitis B and C) > Malignancy > Systemic disorders; rheumatoid arthritis, autoimmune disease, long-term steroid > Diseases of unknown origin; Alzheimer’s, Creutzfeldt-Jakob, Multiple sclerosis

30. ALLOGRAFT PROCESSING Allografts harvesting and processing Techniques include; > Physical debridement > Pulse lavage or ultrasonification > Ethanol treatment > Antibiotic soak > Sterilization

31. ALLOGRAFT PRESERVATION Preservation techniques include; > Fresh; Immunogenic 2 years > Fresh-frozen at -70 degrees centigrade for 5 years, -20 degrees for 1 year -- Freeze dried; indefinite

32. BONE GRAFT SUBSTITUTES Materials that mimic the properties and functions of bone graft in aiding bone healing Relatively inert and easily bond with living tissues Alternative to BGs, no donor site morbidity Absence or infection or viral transmission Used singly, composite &/or in combination with autograft (BG extensor/expander & BG potentiator )

33. BONE GRAFT SUBSTITUTES Powder, pellet, putty form or coatings on implants like hydroxyapatite-coated joint prosthesis Osteoconductive mainly Can be mixed with antibiotics

34. BGSs; AVAILABLE OPTIONS Calcium phosphate Calcium sulfate Collagen based matrices Hydroxyapatite Bone Morphogenic Proteins(BMP) Osteoinductive proteins; BMPs, GFs

35. QUALITIES OF AN IDEAL BGSs Biocompatible Osteogenic Osteoinductive Osteoconductive Porosity Bioabsorbable Does not transmit or aggravate infection Sterilizable Readily available and easy to use Cost effective

36. CLASSIFICATION OF BGSs

37. BGSs; AVAILABLE OPTIONS contd CALCIUM PHOSPHATE Family of calcium salt compounds > Bulk; High compressive strength. Degrade slowly. eg Tricalcium phosphate > Injectable; Used to fill bone voids. Eg Norian SRS

38. BGSs; AVAILABLE OPTIONS contd CALCIUM CARBONATES; Eg Biocora CALCIUM SULPHATE; Eg Osteoset Relatively inexpensive Widely available synthetic bone substitute Most rapidly absorbed

39. BGSs; AVAILABLE OPTIONS SILICON-BASED; Used as delivery systems for osteo -conductive compounds. Eg Bioactive glasses, glassionomer cement SYNTHETIC POLYMERS; Eg polylactic acid, polyglycolic acid. Disadvantage of production of acidic degradation products. CERAMIC COMPOSITES; Eg Collagraft . Composite of hydroxyapatite, tricalcium phosphate and collagen used as a bone expander mixed with autologous bone marrow

40. BGSs; AVAILABLE OPTIONS contd HYDROXYAPATITE; > Defect filler. Delayed degradation. Eg ProOsteon COLLAGEN; > Used as a nonstructural carrier for BMPs, DBMs, or other graft materials GROWTH FACTORS; > TGF-beta, FGF, PDGF

41. BGSs; AVAILABLE OPTIONS conts BONE MORPHOGENIC PROTEINS; > BMP-2, 3 and -7 are the most important > Requires a carrier; allograft, DBM, Collagen, cement POROUS METALS; > Eg Tantallium , titanium alloy, etc > Used to fill porous surfaced of prosthesis

42. COMPLICATIONS Bleeding Nerve injury Vascular injury Pathological fracture Hernia Urethral injury ASIS avulsion Pelvic instability Disease transmission

43. FUTURE/CURRENT TRENDS BONE TISSUE ENGINEERING > For unlimited source of autogenous bone tissue 3D PRINTING; > Allows the production of custom-made implants unique to a patient’s bone defect GENE THERAPY > To transfer genetic encoding information to the target site and induce bone healing

44. FUTURE/CURRENT TRENDS Bone growth factors require carriers to deliver them at site of bone formation, most effective carrier matrix are being sort Combination of autograft with other bone graft substitutes to provide a cocktail of complementary substances Research underway to test efficacy of adding collagen, GFs and MSCs to synthetics which may bestow osteinductive and osteogenic properties to these materials

45. CONCLUSION Bone grafts and bone substitutes are the cornerstone of many orthopaedic procedures, hence the need for every Orthopaedist to be conversant with it and the guiding principles Good knowledge of the options and proper patient selection is important for satisfactory outcomes.

46. REFERENCES National library of medicine, organogenesis 2012 Oct 1;8(4): 114-124. Apley’s system of orthopaedics and fractures, 9 th edition Chapman’s orthopaedic surgery, 3 rd edition Frederick M, Azar JH, Beaty S, Terry C. ( eds ). Campbell’s operative orthopaedics . 13 th edition. Elsevier. Philadelphia. 2017 Miller MD, Thompson SR. Miller’s review of orthopaedics . 8 th edition. Elsevier. Philadelphia. 2020 Arnaout F, Kapoor S, Eltanboly AE. ( eds ). Concise orthopaedic notes www.thelancet.com www.orthobullets.com

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