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Page 1
Bone Void Fillers : Bone And Bone substitutes
Dr Sitanshu
Page 2
Introduction
• 2nd most common graft• Gold standard – autogenous
cancellous bone• Drawbacks – Morbidity Availability Operative time
Page 3
• Allograft – immune response disease transfer impaired
osteoconductivity reduced mechanical
property cost
Page 4
• 1st phase – 4 weeks – mainly from cells of graft
• 2nd phase – host cells (endosteal cells, marrow cells, osteocytes)
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
Page 6
General characteristics of successful bone graft
Osteogenesis
Osteoinduction
Osteoconduction
Good handling characteristic
Non toxic
Biomechanical property similar to cancellous bone
Page 7
Osteogenesis
Process of bone formation through cellular osteoblastic activity which depends on the
presence of osteoprogenitor stem cells.
Page 8
Osteoinduction
Biologically mediated recruitment and differentiation of cell types essential for
bone formation.
Page 9
Osteoconduction
Apposition of growing bone to three dimensional surface of a suitable scaffold
provided by the graft.
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
Page 11
Autograft - Pros
• Osteogenic
• Osteoinductive
• Osteoconductive
• No disease transmission
• No host rejection
Page 12
Autograft - Con
• Viability is compromised
• Quality is not constant
• Second fascial incision
Page 13
Minor complications
Superficial infection
Seroma
Hematoma
Temporary sensory loss
Transient pain
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
Page 15
• 3cm – distance from donor site and ASIS / PSIS
• 3cm – maximum distance from dorsal ilium
Page 16
Factors which can’t be avoided
• Increased operative time
• Blood loss
• Donor site – pain
• Cosmetic defect
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
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.
Page 19
Autogenous cortical graft
• Fibula
• Ribs
• Iliac crest
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
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
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
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
Page 24
Allograft
• Surge in popularity – increased availability
donor screening and tissue processing for safety
new forms has increased versatility
Page 25
• Machine tooling to shape structural allograft
• Reduction of procurement morbidity
• Potential for immediate structural support
• Reasonable success (60-90%)
Page 26
Allograft - ConA
• Results inferior to autograft
• Vary in initial bone quality
• Expensive
• Disease transmission
• Immunogenic reaction
Page 27
• Processing – its disadvantage
• Slower resorption
• Not completely replaced by new bone
• Reduced structural integrity
• Poor results in lumbar fusion
Page 28
• Donor to donor variation
• Low grade inflammatory reaction
Page 29
• Animal studies – correlation between histocompatibility difference and allograft failure
• Reaction specific to donor antigen
• CD8+ reaction
Page 30
• Fresh frozen• Retain BMP• Strong• Better incorporation• Immunogenic• Disease transmission
• Freeze dried• No BMP• Weak• Weaker• Least immunogenic• No documented
disease transmission
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
Page 32
• Revascularizes quickly
Page 33
Factors affecting DBM product
• Processing
• Time of demineralization
• Final particle size
• Terminal sterilization
• Carrier
• Donor viability
Page 34
Carrier for DBM
• Glycerol
• Thermogelling chitosan
• Hyaluronic acid
• Recombinant BMP
• Albumin
• Carboxymethyl cellulose
Page 35
Disadvantage
• Difficulty in handling
• Tendency to migrate from graft site
• Lack of stability
• Transmit disease
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
Page 37
Ceramics
• Stable compounds of metals with oxygen or other anions
• Non injectable ceramics – according to resorbing power
• Injectable ceramics
Page 38
Non injectable ceramics
• Osteoconductive
• Hydroxyapatite, Tricalcium phosphate, Calcium sulphate dihydrate
• High quality synthetic material with no biologic hazards
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
Page 40
Page 41
Rapidly resorbing ceramics
• Tricalcium phosphate (alpha 1200 degrees, beta at 800 degrees) – 39% Ca, 20% P
• Calcium sulfate
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
Page 43
• Calcium sulfate - Osteoconductive but its rapid resorption rate creates doubt about its ability to maintain a three-dimensional framework to support Osteogenesis
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
Page 45
Slow resorbing ceramic
• Hydroxyapatite
• Bone incorporation – pore size and pore interconnectivity
• Drawback - slow resorption, brittle
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
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
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
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
Page 50
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
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
Page 53
• Availability and the relative safety of its harvest
• Harvested by aspiration from patients, with limited dilution by peripheral blood
• Concentration
• Culture
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
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
Page 56
Page 57
BMP and synthetic composite
• BMP 2, BMP 7 (rhOP 1)
• Carrier to maintain optimum regional concentration
• Hydroxyapatite
• DBM
• Hyaluronic acid
• Collagen