Bone Substitutes and Cement

1. BONE SUBSTITUTES

2. Introduction
 Bone regeneration is an intricate process,well organised physiological process seen
in normal fracture healing.
 The process needs to be accelerated in situations like fracture healing,filling of
large bone gap,atrophic non unions due to trauma or ablative tumor surgery and
infection.
 Autologous bone graft is the gold standard to augment the impaired or insufficient
bone regeneration process however it is associated with morbidity and limitation
of stocks.

3.  A bone graft substitute can be defined as a synthetic, inorganic or biologically
organic combination which can be inserted for the treatment of a bone defect
instead of autogenous and allogenous bone.
 They are basically either osteoconductive , osteoinductive or osteogenesis
properties.
 More than 60 bone graft substitutes have been found fit for use(Kurein et all)

4. Bone substitutes
1. Natural bone based
2. Growth factor based
3. Cell based
4. Ceramic based
5. Polymer based

5. Bone graft
1. Autogenous
2. Allogenic
3. Heterogenous

6. Uses
 To fill cavities or defects resulting from cysts,tumors or other causes.
 To bridge joints and thereby provide arthrodesis.
 To bridge major defects or establish the continuity of long bones.
 To promote union or fill defects in delayed union,malunion,fresh fractures or
osteotomies.
 Cortical bone grafts are used for structural support

7. Autogenous cortical bone grafts
1. proximal third fibula(can replace distal third radius)
2. Middle third fibula along with peroneal artery and vein pedicle can be used in early
avascular necrosis of femur.

9. Autogenous cancellous grafts
 Large cancellous and corticocancellous grafts are obtained from anterior iliac crest
and posterior iliac crest.
 Small cancellous grafts can be taken from olecranon ,greater trochanter of
femur,femoral condyle,proximal tibial metaphysis,medial malleolus of tibia and
distal radius. A minimum of 2cm of subchondral bone must remain to avoid
collapse of articular surface.

10. Iliac crest bone graft
 If form and rigidity are unnecessary multiple chip grafts may be removed
 If more rigid bone graft is needed anterior or posterior third of crest is needed .
 For wedge grafts the cuts are made at right angle to the crest.

12. Complications
 Lateral femoral cutaneous and ilioinguinal nerve injury.
 Injury to superior gluteal vessels by retraction against the roof of aciatic notch
 Herniation of abdominal contents via graft site.
 Gait disturbances due to bone graft from posterior iliac region.

13. Other natural bone based grafts
1. Bone marrow aspirate from iliac crest(osteogenic and osteoinductive)
2. Allogenic bone grafts from other individuals or cadevers(osteoconductive and
osteoinductive)
3. Demineralised bone matrix(osteoconductive and inductive) - Acid ectracted bone
with growth factors,non collagenous proteins and collagen type 1.Available in form
of granules(CRONOS),chips,powder and paste.Used in non unions,delayed unions
and in expanding phase of aneurysmal bone cysts.

14. Growth Factor based substitutes
 Natural and recombinant growth factors used alone or in combination with other materials .
 Other materials include-transforming growth factor-beta
Platelet derived growth factor
Fibroblasts growth factor
Bone morphogenic proteins 2 in bone grafting,7 in nonunion

15. Cell based bone graft substitutes
1. Stem cells
2. Collagen
3. Gene-therapy.

16. Ceramic based substitutes
 Ceramics are synthetic scaffolds made from calcium phosphate which induce a
biological response similar to that of bone.
 Contains-Calcium phosphate (85%)(osteoconductive)Calcium
carbonate(10%),magnesium phosphate (1.5%) and calcium fluoride.
 Examples
1. Calcium hydroxyapetite
2. Tricalcium phosphate
3. Bioactive glass
4. Calcium sulphate
5. Injectable ceramic cements

17. Calcium hydroxyapatite and phosphate
 High degree of hardness
 Osteoconductive

18.  Calcium phosphate cement may be used in fracture repair of spine ,distal radius
metaphysis,tibial plateau and hip as it has high compressive strength and may
allow early weight bearing.
 Calium sulphate (osteoconductive) is completely resorbed as new bone forms and
remodels so used in bone cysts filling,benign bone lesions and cavitary or
segmental bone defects.
 Synthetic hydroxyapatite has slow in vivo resorption and brittleness
 Tricalcium phosphate(alpha and beta) is better molded than hydroxyapatite but it
is weaker.alpha-granules beta-injectable formulation
 Coralline hydroxyapatite (osteoinductive) comes based on the size of pores as Pro
Osteon 500 and 200mm.
 Bioactive glasses are used as spcer in iliac crest and vertebral prosthesis .

20. Thank you.