Bone graft

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  • Because separation of body tissue from its blood supply results in cell death
    Depends on age sex health genetic predisposition
  • Pain – more bone removal SI joint destabilization
    Vascular – superior gluteal vessels close to sciatic notch
    Neurologic sciatic lateral cut nerve
  • TCP tricalcium phosphate
    BMA bone marrow aspirate
  • Wedges or threaded bone – function both as graft and fixation device
  • Destroys osteoinductive proteins
    Less representative of human tissue
  • Age sex health genetic predisposition
  • Enhanced bioavailability following demineralization
  • immunogenecity
  • Same elemental and stoichiometric properties
  • facilitate the migration of bone-forming cells, growth factors, and phagocytic cells into it, enhancing the process of new bone development and its resorption.
  • modulate physical properties of bone-filling agents and to deliver factors that stimulate bone formation
    facilitates handling and placement at the time of surgery
  • osteoblasts, adipose cells, chondroblasts, and fibroblasts
  • the number of progenitors available in a graft site can be increased by concentration
    subsequent use in transplantation, stem cells also can be cultured and expanded to many times their original number.
  • renewable and reliable source of osteogenic cells without the disadvantages of standard open-grafting techniques
  • Bone graft

    1. 1. Page 1 Bone Void Fillers : Bone And Bone substitutes Dr Sitanshu
    2. 2. Page 2 Introduction • 2nd most common graft • Gold standard – autogenous cancellous bone • Drawbacks – Morbidity Availability Operative time
    3. 3. Page 3 • Allograft – immune response disease transfer impaired osteoconductivity reduced mechanical property cost
    4. 4. Page 4 • 1st phase – 4 weeks – mainly from cells of graft • 2nd phase – host cells (endosteal cells, marrow cells, osteocytes)
    5. 5. Page 5 Role of cancellous bone • Scaffold where cells interact • Nutrition • Hematopoiesis, Myelogenesis, Platelet formation • Source of pluripotent osteoprogenitor stem cell • Local growth factors for differentiation • Same strength of cortical bone by 6-12 months
    6. 6. Page 6 General characteristics of successful bone graft Osteogenesis Osteoinduction Osteoconduction Good handling characteristic Non toxic Biomechanical property similar to cancellous bone
    7. 7. Page 7 Osteogenesis Process of bone formation through cellular osteoblastic activity which depends on the presence of osteoprogenitor stem cells.
    8. 8. Page 8 Osteoinduction Biologically mediated recruitment and differentiation of cell types essential for bone formation.
    9. 9. Page 9 Osteoconduction Apposition of growing bone to three dimensional surface of a suitable scaffold provided by the graft.
    10. 10. Page 10 Potential use of natural and synthetic grafts • Fusion – cervical fusion lumbar onlay graft lumbar interbody fusion arthrodesis • Bone void filler – collapsed vertebral body autograft donor site repair bony defects
    11. 11. Page 11 Autograft - Pros • Osteogenic • Osteoinductive • Osteoconductive • No disease transmission • No host rejection
    12. 12. Page 12 Autograft - Con • Viability is compromised • Quality is not constant • Second fascial incision
    13. 13. Page 13 Minor complications Superficial infection Seroma Hematoma Temporary sensory loss Transient pain
    14. 14. Page 14 Major complications • Infection • Prolonged wound drainage • Hernia • Deep hematoma • Need for reoperation • Pain > 6 months • Profound sensory loss • Heterotopic bone formation • Vascular injury • Neurologic injury • Scars • Subluxation • Gait disturbance • SI destabilization • Enterocutaneous fistula • Pelvic fracture
    15. 15. Page 15 • 3cm – distance from donor site and ASIS / PSIS • 3cm – maximum distance from dorsal ilium
    16. 16. Page 16 Factors which can’t be avoided • Increased operative time • Blood loss • Donor site – pain • Cosmetic defect
    17. 17. Page 17 Sites • Iliac crest (Anterior or posterior iliac crest) • Greater trochanter • Gerdy's tubercle • Distal part of the radius • Distal part of the tibia
    18. 18. Page 18 • Autogenous cancellous bone graft is an excellent choice for nonunions with <5 to 6 cm of bone loss and that do not require structural integrity from the graft. It can also be used to fill bone cysts or bone voids after reduction of depressed articular surfaces such as in a tibial plateau fracture. Stable internal or external fixation is also required, to provide the optimum environment for graft consolidation and successful fracture-healing.
    19. 19. Page 19 Autogenous cortical graft • Fibula • Ribs • Iliac crest
    20. 20. Page 20 • With or without vascular pedicle • Osteoconduction + Osteogenesis • Non vascularized grafts become weaker in 6 weeks – resorption, revascularization • Vascularized – stronger – remodelling similar to normal bone • But by 6-12 months – no difference • Fixation required
    21. 21. Page 21 • Advantage • Defects > 5-6cm • Immediate structural support • Disadvantage • Subjective sense of weakness and instability • Big toe weakness • Need for reoperation at donor site
    22. 22. Page 22 Osteoconductive matrices • No osteogenic or osteoinductive property • Greater source availability • Elimination of second operative site • Tricalcium phosphate (alpha, beta) • Hydroxyapatite • Injectable calcium phosphate cement
    23. 23. Page 23 Graft Material Osteogenesis Osteoinduction Osteoconduction Autograft 2* 2 2 Allograft 0 1 2 Xenograft 0 0 2 α-TCP 0 0 1 β-TCP (porous) 0 0 2 Hydroxyapatite 0 0 1 Injectable calcium phosphate cement (e.g., Norian SRS†) 0 0 1 BMA 3 2 0 β-TCP plus BMA 3 2 2 DBM 0 2 1 Collagen 0 0 2 BMP 0 3 0 Hyaluronic acid 0 0 0 Bioactive glasses 0 0 1 Degradable polymer 0 0 1 Porous metals 0 0 1
    24. 24. Page 24 Allograft • Surge in popularity – increased availability donor screening and tissue processing for safety new forms has increased versatility
    25. 25. Page 25 • Machine tooling to shape structural allograft • Reduction of procurement morbidity • Potential for immediate structural support • Reasonable success (60-90%)
    26. 26. Page 26 Allograft - ConA • Results inferior to autograft • Vary in initial bone quality • Expensive • Disease transmission • Immunogenic reaction
    27. 27. Page 27 • Processing – its disadvantage • Slower resorption • Not completely replaced by new bone • Reduced structural integrity • Poor results in lumbar fusion
    28. 28. Page 28 • Donor to donor variation • Low grade inflammatory reaction
    29. 29. Page 29 • Animal studies – correlation between histocompatibility difference and allograft failure • Reaction specific to donor antigen • CD8+ reaction
    30. 30. Page 30 • Fresh frozen • Retain BMP • Strong • Better incorporation • Immunogenic • Disease transmission • Freeze dried • No BMP • Weak • Weaker • Least immunogenic • No documented disease transmission
    31. 31. Page 31 Demineralized bone matrix • Allograft bone that has had the inorganic mineral removed, leaving behind the organic collagen matrix • More osteoinductive properties • DBM + glycerol carrier – commonly used • Available data – more as bone graft extender, not substitute
    32. 32. Page 32 • Revascularizes quickly
    33. 33. Page 33 Factors affecting DBM product • Processing • Time of demineralization • Final particle size • Terminal sterilization • Carrier • Donor viability
    34. 34. Page 34 Carrier for DBM • Glycerol • Thermogelling chitosan • Hyaluronic acid • Recombinant BMP • Albumin • Carboxymethyl cellulose
    35. 35. Page 35 Disadvantage • Difficulty in handling • Tendency to migrate from graft site • Lack of stability • Transmit disease
    36. 36. Page 36 Xenograft • From animals • Impractical for clinical use on a wide scale • Removal of protein and fat – processing • Removes osteoinductive proteins • Kiel bone, Oswestry, Bio Oss
    37. 37. Page 37 Ceramics • Stable compounds of metals with oxygen or other anions • Non injectable ceramics – according to resorbing power • Injectable ceramics
    38. 38. Page 38 Non injectable ceramics • Osteoconductive • Hydroxyapatite, Tricalcium phosphate, Calcium sulphate dihydrate • High quality synthetic material with no biologic hazards
    39. 39. Page 39 • Alternative or as an addition to either cancellous autograft or allograft or as a cancellous bone void filler or bone graft extender or in sites where compression is the dominant mode of mechanical loading • Safe and effective substitute for iliac graft autograft • Cost
    40. 40. Page 40
    41. 41. Page 41 Rapidly resorbing ceramics • Tricalcium phosphate (alpha 1200 degrees, beta at 800 degrees) – 39% Ca, 20% P • Calcium sulfate
    42. 42. Page 42 • Calcium phosphate – calcium phosphate rich microenvironments that stimulate osteoclastic resorption and then osteoblastic new bone formation, resulting in new bone formation • Pore size - less porous formulations resorb before complete bone ingrowth
    43. 43. Page 43 • Calcium sulfate - Osteoconductive but its rapid resorption rate creates doubt about its ability to maintain a three-dimensional framework to support Osteogenesis
    44. 44. Page 44 Intermediate resorbing ceramic • Beta tricalcium phosphate - In the process of being resorbed, it can enrich the local environment with osteogenic substrates that, in turn, can be used by activated osteoblasts • Broad range of pore size (<1µm to 1000µm) • Sponge-like interconnected microporosity endowed with excellent wicking and hydrophilic properties
    45. 45. Page 45 Slow resorbing ceramic • Hydroxyapatite • Bone incorporation – pore size and pore interconnectivity • Drawback - slow resorption, brittle
    46. 46. Page 46 Injectable ceramics • Calcium phosphate cement - paste of inorganic calcium and phosphate that hardens in situ with a low exothermic temperature • Slowly transforms into bone over 3 to 4 years • Adjunct to fixation in both femoral neck and intertrochanteric hip fractures
    47. 47. Page 47 • Drawbacks – 1. slow resorption 2. low porosity 3. high cost 4. extravasation 5. intra articular extension 6. increased washout 7. low shear resistance
    48. 48. Page 48 Collagen • Animal-derived collagen with synthetic calcium phosphate • Putty-like consistency • Can be used as bone graft extenders to increase the volume of bone graft into a defect when a sufficient volume of autograft is not readily available
    49. 49. Page 49 Non biologic Osteoconductive substrates 1. absolute control of the final structure 2. no immunogenicity 3. excellent biocompatibility Degradable polymers - polylactides Bioactive glasses Porous metals - tantalum
    50. 50. Page 50
    51. 51. Page 51 Composite graft • Any combination of materials that includes both an osteoconductive matrix and an osteogenic or osteoinductive material 1.Bone marrow aspirate 2.Osteoblastic progenitor stem cell 3.Blood 4.Platelet rich plasma 5.Growth factors
    52. 52. Page 52 Bone marrow aspirate background • Osteoblast progenitor cells – 1.periosteum of long bones 2.the peritrabecular connective tissue 3.the bone marrow • All the critical cellular components that contribute to bone growth present • Fibroblast, undifferentiated cells • Animal research suggests that precursor cells in bone marrow proliferate and differentiate after transplantation
    53. 53. Page 53 • Availability and the relative safety of its harvest • Harvested by aspiration from patients, with limited dilution by peripheral blood • Concentration • Culture
    54. 54. Page 54 Bone composite • Used successfully to stimulate healing in tibial fractures • Osteogenic potential was maintained as the cells were expanded in culture • Facilitated greater bone formation and fusion success rates • Xenograft bone and other bone substitutes could be rendered osteogenic
    55. 55. Page 55 Synthetic composite • Addition of BMA was essential for tricalcium phosphate and hydroxyapatite to achieve results comparable to those obtained with cancellous bone at 24 weeks • β-TCP/BMA composite may be superior even to autograft, which suffers from anoxic cell death in the center of the graft because of the absence of vascularization
    56. 56. Page 56
    57. 57. Page 57 BMP and synthetic composite • BMP 2, BMP 7 (rhOP 1) • Carrier to maintain optimum regional concentration • Hydroxyapatite • DBM • Hyaluronic acid • Collagen

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