Ceramics are inorganic, solid materials used in orthopaedics due to their strength and biocompatibility. They are classified as bio-inert, bioactive, or bioresorbable. Alumina and zirconia are commonly used bio-inert ceramics. Hydroxyapatite is a bioactive ceramic used for coatings. Ceramic properties depend on grain size and porosity, and they are stronger with smaller grain size and less porosity. Processing involves compacting ceramic powder and sintering to form the final piece. Ceramics are used for articulating surfaces like ball heads due to their hardness, smoothness and wear resistance.

1. Ceramics in Orthopaedics

2. Introduction
Biomaterials : Natural or synthetic substance, capable of being
tolerated permanently or temporarily by the body.
Ceramics :
These are synthesised, inorganic, solid, crystalline, materials resulting
from ionic bonding of a metallic ion or from bonding of an inter-
metallic and a non-metallic ion (usually oxygen)
No free electrons lead to strong and stable bond as compared to
metals which have free electrons leading to weaker bonds.
Properties of ceramic depend on grain size and porosity.
Strength in inversely proportional to grain size and porosity.

3. Types of Ceramics
Classified into :
Bio-inert ceramics
Bio-active ceramics
Bio-resorbable ceramics
Oxides : Alumina (Al2O3), Lime (CaO), Zerconia (ZrO2)
• Carbides : Tungsten carbide, Titanium carbide
• Borides : TiB2
• Silicides

4. Bio-inert Ceramics
• Incorporated in the bone with pattern of contact osteogenesis.
Examples: Alumina(Al2O3) ceramic and Zerconia
ceramic(ZrO2).
Alumina ceramics contain hexagonal crystals.
Zerconia ceramics have 3 forms – cubic, tetragonal and monoclinic
– transformation takes place under various changes in
temperature, chemical – mechanical stress and humidity.
Chemical stabilisers ( Yttrium oxide, Cerium oxide)are added to
form partially stable zerconia .

5. • Alumina is chemically more stable while partially stabilized
zerconia is mechanially stronger than Alumina.
• Both have much better wear resistant characteristic compared
to stainless steel or cobalt-chromium alloy.
• Alumina is used to fabricate ceramic on ceramic hip prosthesis
(femoral heads and acitabular cups) where as PSZ is used to
fabricate ceramic on polyethylene hip prosthesis(has a high
flexural modulus compared to alumina).
• (Tendency of a material to resist bending)

6. Bio-Active ceramics
• Characteristic of osteo-conduction
• Capability of chemical bonding with living bone – bonding
osteogenesis.
• Examples : Bioglass
Apatite and Wollastonite containing glass ceramics
Synthetic Hydroxy-apatite
Bending strength of Hydroxy-apatite is lower than the cortical
bone – hence it cannot be used to fabricate weight bearing
implants, instead used for coating and filling bone defects.
Using AW-CG vertebral prosthesis, iliac crest prosthesis,
intervertebral spacers, laminoplasty sapcers are fabricated.

7. Processing of Ceramic
CERAMIC POWDER
(compaction)
GREEN CERAMIC
MOLDED IN DESIRED PART
(thermal treatment)
SINTERED CERAMIC
(machining and polishing)
FINAL PIECE

8. Tribology
• It is the science and engineering of of interacting surfaces.
• Goal: To use a very hard, very smooth surface and bio-compatible
material to minimize wear.
• Ceramics heads – resistant to scratching.
•
• Improved wetability (ability of liquid to maintain contact with the
solid surface) – improves lubrication.
• Ceramic on ceramic articulations are very smooth , roughness is in
nanometer range .
•
• To achieve improved tribology – there should not be any mismatch
between the femoral head (ball) and the acetabular liner – results
in equatorial laoding around the rim of articulation or polar loading
at the apex of articulation.
• Both the types result in increased pressure and decreased
lubrication – leading to increased wear of prosthesis.

9. • Ceramic on ceramic articulations can exhibit squeak – an
audible high pitched noise during motion.
• Poor component positioning can increase edge loading which
lead to stripe wear in an area near a loaded edge.

10. Advantages of ceramic
• Can be used in patients allergic to metal
components.
• 15% of patients are allergic to Nickel,
component of metal bearing surface.

11. Recent Advances
• Recently, oxidised zirconia (OXINIUM) on polyehtylene has been
introduced especially for total hip arthroplasty.
• In total knee arthroplasty Cobalt-Chromium prosthesis is surface
treated with ceramic zerconium (Oxinium). Provides advantage of
superior compressive and shear strength of Zerconium along with
the tensile strength of Co-Cr.
• Titanium Nitride (non-oxide ceramic) – used for coating steel and
titanium products, including cutting surfaces of screws and drill bits.
• The ceramic coating is applied by physical vapour deposition onto
the surface of metals – imparts a hard surface coating several
microns thick – Gold like appearance.
•

13. • Calcium Phosphates :
• As structural implants – used as composite material with
polymers such as poly-L-lactic –acid (PLLA)
• As surface coatings – used in combination with metallic
implants – increase osteo-integration.
• Hydroxiapatite is a clear crystalline powder used in composite
with PLLA polymer for bone screws and a spray coating on hip
stems.

14. • Beta-Tricalcium-Phosphate :
Beta crystalline form of Ca3PO4.
Advantage : Gradually resorbs unlike hydroxyapatite.
Calcium sulphate :
Used as bone graft substitute
Used as a carrier for antibiotics – resorbs in the body.
Silicon Nitride :
Used as ceramic interbody spacer for spinal fusion and is being
developed as a potential bearing surface for hip arthroplasty.

15. Pyrolytic Carbon:
Fabricated by heat treatment.
Hard and very bio-compatible surface.
Carbon on carbon bearing surface.
Used in arthroplasty of the MCP and IP joints in patients with
rheumatoid arthritis.

16. •Thank You