bearing surfaces

DR. SIDHARTH YADAVDEPT. OF ORTHOPAEDICSNKPSIMS

Carnochan (1840) was the first surgeon, who thought that hip joint could also be replaced artificially.

A wooden block was installed between the damaged ends of a hip joint in New York by Carnochan.

Dr Marius N Smith-Petersen introduced the mould arthroplasty (1925).

The original design was ball-shaped hollow hemisphere of glass which could fit over the ball of the hip joint.

The objective was to stimulate cartilage regeneration on both sides of the moulded glass joint.

He used a reactive synovial like membrane.

The glass could not withstand the stresses of walking and quickly failed.

This led to use of other materials, such as Viscaloid (a celluloid derivative, 1925), Pyrex (1933), Bakelite (1939), and later that year, an alloy of Cobalt-Chromium is called Vitallium (1936).

This Vitallium material was very strong and resistant to corrosion, and continued to be employed in various prostheses since that time.

In 1938 PHILIP WILIE performed the first total joint replacement. He used stainless steel.

In 1950, SEVEN KIAER used dental scrylic cement in orthopaedics by using it to bind a plastic proesthesis to bone.

In 1951, McKEE & WATESON- FARRAR used thompson type femoral component & a metal acetabular cup. Both were of chrome cobalt alloy.

In 1962 UHMWPE was introduced.

In 1967 MULLER introduced FIRST GENERATION METAL ON METAL ARTHROPLASTY.

In 1970, Pierre Boutin was the first to introduce a ceramic-on-ceramic hip arthroplasty

• Ball and socket joint

• Femoral head or ball is at the end of thighbone or femur.

• Socket or acetabulum holds the ball.

Acetabular component - consists of two components

Cup - usually made of titanium

Liner - can be medical grade plastic, metal or ceramic

Cup

Liner

The femoral component (stem and neck portion), is made of metal.

Femoral head is made either of metal or ceramic.

Stem is shaped to fit into the bone and support the new joint.

Neck

Stem

Head

• Range of Motion• Stability• Wear resistance• Lifestyle• Gender• Age• Weight• Severity of Osteoarthritis disease

Patients may have: Young and active lifestyle Rheumatoid arthritis Osteoarthritis Post-traumatic arthritis Collagen disorders Avascular necrosis Non-union of femoral fractures

Inappropriate for patients who recently or currently have: Joint sepsis (infection) Insufficient bone stock Marked atrophy (weakness) Upper femur deformity Skeletal immaturity

The bearing is the union of the ball and socket.

Bearings are made from a variety of commercially available materials.

• Metal-on-Polyethylene (poly)– “traditional” bearing– Poly cup with a metal ball

• Metal-on-Metal– All metal ball and cup

• Ceramic-on-Polyethylene (poly)– Poly cup with a ceramic ball

• Ceramic-on-Ceramic– Ceramic cup and ball

Poly acts as a cushion for the joint

Shell made of titanium alloy

Cup made of medical grade cross-linked polyethylene

Long clinical history since 1963

All bearing surfaces wear with time

Cross Linked Polyethylene exhibits 86% wear reduction vs. traditional polyethylene in mechanical tests

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Wea

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Wear Rates: Crosslinked vs. Traditional PolyWear Rates: Crosslinked vs. Traditional Poly

Traditional Polyethylene

Cross Linked Polyethylene from

DePuy

Ball and liner made of high-standard, surgical-grade cobalt chromium alloys

Available since 1960s

Wear rates up to 100 times less than metal-on-poly bearings in mechanical tests

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Traditional Polyethylene Ultamet Metal on Metal Articulation from DePuy

Wear Rate: Metal vs. PolyethyleneWear Rate: Metal vs. Polyethylene

Increased ion concentration in patients.

Cobalt is associated with various cardiac ,neurological & endocrine symptoms.

Long term exposure can cause cancer.

Hypersensitivity

One patient has been found with chromium & cobalt in CSF.

Alumina ceramics was introduced as a bearing surface in 1971 as an alternative to metal on poly.

Since then many advances has been made in ceramics :-

- Alumina that was introduced in 1970 (1st generation ) had low density & a very coarse micro structure.

- SECOND GENERATION (1980’s) :- had reduced microstructure & grain size.

- THIRD GENERATION (1990’s) :- had improved mechenical strength , more reduced microstructure grain size & manufactured by HOT ISOSTATIC PRESSURING.

- FOURTH GENERATION ( 2000’s) :- new alumina matrix composite.

Hardness Hydrophilic Inertness Resistant to scratch High biocompatibility

These characteristic’s make less wear than metal.

At equal partical levels alumina is less toxic then metal.

Types :- - Alumina (Al2O3) - Zirconia ( ZrO2 )

fracture toughness of ZIRCONIA is twice then alumina.

A new compound matrix composite was developed & early results have shown hopeful in both COC & COP in laboratory.

Cup made of cross-linked poly

Ball made of Delta Ceramic Composite

zirconia aluminum ceramic

Highly Cross Linked Polyethylene exhibits 86% wear reduction over standard poly liners in mechanical test

Delta Ceramic Ball resistant to chipping or cracking 97% tougher than traditional

alumina ceramics in mechanical tests

Smoother femoral ball decreases wear potential

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Delta Conventional Alumina Ceramics

Fracture toughness: Delta

vs. Alumina

Ball and cup made of alumina ceramic

Shorter clinical history

Not toxic to the body

Ceramic femoral heads offer:

Excellent compatibility within the body

Good mechanical performance

Very hard and scratch-resistant

Chemical and temperature stability

100-200 times less wear rate than other materials in mechanical tests

Resistance to deformation and surface scratching

Less particle debris around joint available to get into the body

OONISHI & COWORKER’S reported head penetration for ceramic & metal:-

- Alumina :- 0.1 mm/yr.- Metal :- 0.25mm/yr.

SCHULLER MART reported :-- 0.03mm/yr for alumina- 0.10 mm/yr for metal ( after 9-11 yr of

follow up)

Brittle Low fracture toughness Squeaking noice heard with activity.

Received 15 November 2005; revised 12 July 2006; accepted 13 July 2006Published online 13 October 2006 in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jbm.b.30691