knee replacement in young patients

Dr.A.K.VenkatachalamMS Orth, DNB Orth, FRCS, M.Ch

OrthConsultant Orthopedic surgeon

Chennaiwww.kneeindia.com

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*< 65 years , Better is < 50 years of age.

*Life expectancy of > 20 years

*Family history of longevity

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*Numbers increasing in young patients < 55 years

Australian registry

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“If the historical growth trajectory of joint replacement surgeries continues, demand for primary THA and TKA among patients less than 65 years old was projected to exceed 50% of THA and TKA patients of all ages by 2011 and 2016, respectively.”

* Steven M. Kurtz PhD, Edmund Lau MS, Kevin Ong PhD, Ke Zhao MA, MS, Michael Kelly MD, Kevin J. Bozic MD, MBA Symposium: ABJS Carl T. Brighton Workshop on Health Policy Issues in Orthopaedic SurgeryVolume 467, Issue 10 / October , 2009

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Secondary osteoarthritis from

*Post traumatic arthritis

*Rheumatoid arthritis is the main cause

*Whereas in older patients, Primary OA is the leading cause.

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AGE( years)AGE( years) FAILURE RATESFAILURE RATES

< 65 years< 65 years 12%12%

65- 75 years65- 75 years 10%10%

> 75 years> 75 years 4%4%

*Against-

1)Total knees fail more often in young patients

FAILURE RATES AND AGE

Robertsson, Thesis Lund 2000 , Swedish arthroplasty registerwww.kneeindia.com 6

*than their older colleagues

*Wear is proportional to usage.

*Young patients walk on average upto 50% more than older patients.

*Usage leads to increased poly wear

*Poly wear leads to aseptic loosening

Patient agePatient age Average of Average of steps/yearsteps/year

< 60 years< 60 years 1200,001200,00

> 60 years> 60 years 800,00800,00

Age & activity after THR/TKR

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*Young people live longer.

*Young people survive their prosthesis.

*Older people die before prosthetic failure.

AGE(years)AGE(years) Expected to Expected to live furtherlive further

50 years50 years 32 years32 years

67 years67 years 18 years18 years

LIFE EXPECTANCY( WOMEN)

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*Previous three slides indicates that there is a higher risk of failure in young patients and they may require a revision within 10 years

*Surgeon knows this. He also knows that the revision will be technically a difficult operation than the primary. Result also will be inferior.

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He is unwilling to listen and wait.

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*severe pain and stiffness in the knee joint,

*Impaired quality of life,

*Failure of previous treatments of the painful hip / knee  joint.

*Specially suitable candidate is a young patient with severe impairment of both hip and knee joints eg- Poly arthritis like rheumatoid arthritis / sero-negative arthritis.

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*The OS can do a TKR with a prosthesis that wears out slowly.

*Use of materials, techniques, activity modification can lead to better implant survivorship.

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*Prolong prosthetic life, preserve bone while providing function.*Search for design, durability of counter-face, poly, technique, best fixation. *Education of patient about permissible activities of daily living and sport.*Explain possibility of a future revision.*Prevent late metastatic infection from a remote source.*Encourage treatment if the patient has fully understood all issues.

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*Baby Boomers

*Relatively healthy

*Wanting the best technology

*Are relatively dissatisfied with current outcomes

*Will out live current total knee technology

*The main contributor to knee replacement growth

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Patient expectations start rising concomitantly.

Internet savvyWant only broken part to be fixedAs small scar as possibleNo painWant to dance, participate in sportsWant alignment perfect, stability

*Surgical outcomes ≥ Expectations

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*Cycling

*Calisthenics

*Swimming

*Low-resistance rowing

*Skiing machines

*Walking & Hiking

*Low-resistance weightlifting

Knee society

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*Baseball *Basketball *Football *Hockey *Soccer *High-impact aerobics *Gymnastics *Jogging *Power lifting

Knee society

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Wear is an issue. Steps to reduce wear *Bearings- alternate bearings like oxidized zirconium, ceramic*Poly ethylene X3 poly, anti oxidants, thickness.*Cemented vs cementless fixation*Accuracy of component placement- ? Navigated surgery*Fixed vs mobile bearing components*Single radius vs multi radii designs.

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Wear in TKR’s

Patient

Polyethylene

DesignTechnique

Counter face

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*Change femoral counterface ( Oxidized zirconium, Ceramic)

*Change Poly insert

( XLPE)

*Change design*Mobile vs fixed bearing

*CR vs PS

*Single vs multiple radius curve

*Locking mechanism

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*X linked polyethylene seem to be advantageous at least from the hip side.

*Proved lowering of long term wear rates

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THR TKR

Contact stresses low High

Wear abrasive/ adhesive fatigue

Crack propagation Less important Important

Highly cross linked polyethylene is advantageous in the knee also.

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*Behaves differently in clean and abraded environments

*Wear increases in abraded environment with cobalt chrome for both polys

*Hence highly cross linked poly may not be the best material in the altered environment -10

0

10

20

30

40

50

60

Clean Abraded

CoCr/CPE

CoCr/XPE

Wear rate mm3/MC

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*Sequentially irradiated and annealed ( not melted polyethylene)

*Significant wear reduction

*No mechanical changes

*Same poly used for hips and knees

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*Scratches are bad - Ideally try to eliminate

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*Conventional cobalt chrome is used for femoral and titanium or highly polished cobalt chrome used for tibial base plate. Polishing of tibial tray reduces back side wear.

*Pure Ceramics

*Oxidized zirconium

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*Femoral *Cobalt Chrome

* scratching is common

*From cement and poly

*Care to remove cement after TKR.

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*Meet requirments for ideal TKR

*Smoother

*↓ Coefficient of friction

*More scratch resistant

*Less wear against both conventional and highly cross linked poly ethylene.

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*Polyethylene wear performance of oxidized zirconium and cobalt chromium knee components under abrasive conditions

* ( Ries MD, Salehi A, Widding.K, Hunter G.,JBJS ( Am) 2002)

Oxidized Zirconium femoral components reduce polyethylene wear in a knee wear simulator.

( Ezzel KA, Hermida JC,Colwell CW Jr,D’Lima DD, CORR, Nov 2004)

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*Zirconium- metallic element

*Zirconia- ceramic

*Zr-2.5 Nb Metallic alloy

*Super heating zirconium to 500+°C in Oxygen presence

*Surface transformation into zirconia ( ceramic oxide)

*Chemically bonded ceramic oxide surface 5μ thick Ceramic Oxide

Original Surface

Air

500oCOxygenDiffusion

Oxygen Enriched Metal

Metal Substrate

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*It is a metal component*Thin layer of ceramic like material that is part

of its innate structure. This is not a coating. *Ceramic oxide is 5 μ thick*Biocompatibility is excellent, matches titanium*Very low coefficient of friction vs Cobalt

chrome.*Extremely abrasion resistant. *Hard like ceramic*Equivalent strength properties to Cobalt

chrome.*Adverse to chipping that can occur at insertion

and over time.*Lack of Nickel allergy.

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*Equivalent to Cobalt Chrome

*1000 pounds

*10 x 106 Cycles

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*Oxdized zirconium produces fewer PE particles when compared to Cobalt chromium

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*Oxidized zirconium reduces volumetric wear by upto 89% in an abraded environment when compared to Cobalt Chrome

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*Strength of Cobalt chrome

*Low coefficient and scratch resistance of ceramic

*Non brittle as the ceramic layer is part of the innate structure.

*Decrease wear is the main advantage.4900 less volumetric wear.

*160 times smoother.

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*Many variables*Articular congruity*CR vs PS*Fixed vs mobile bearing*Single radius vs multi radii*Locking mechanism

*All have in- vitro/theoretical evidence of benefits.

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*Cemented TKR is the gold standard at present*However Cement constitutes a third body

wear.*Best fixation is biologic with bone ingrowth

into prosthesis.*Examples of hips – Uncemented hips are

standard in young patients. *Cementation leads to extra operative time*Part results of poor cemenless fixation stem

from metal backed patellas.*Cementless fixation will be the preferred

method in future.

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*16 knees from 2007 to 2009 in patients ≤55 years*Cobalt chromium femoral components in 8 and Oxidized zirconium in 8 knees.*CR- 6 knees, PS- 10 *Diagnoses- Post traumatic arthritis-2 Rheumatoid arthritis- 6 Osteoarthritis- 8

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*Knee scores improved in all.

*Range of movement from 95 degrees to 140 degrees.

*No loosening

*1 patient with bilateral TKR has anterior knee pain, had patellar component revision

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*Skin incisions 4- 6 inches long.

*Midvastus, sub vastus, minimally invasive quad splitting.

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*46 year old Indian housewife.

*Left gender specific high flex knee replacement

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*Zero error Component placement

*Extra articular deformities- one stage replacement

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*Patient specific instrumentation

*Requires MRI scan & Standing x rays

*Eliminates 23 steps from TKR.

*For distal femoral cut & proximal tibial cut.

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Rheumatoid arthritis 38 year old patient

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*Durable materials like Oxidized zirconium, cross linked poly, highly polished tibial base plate

*Single radius femoral prosthesis

*Computer assisted knee replacement

*Patient specific instrumentation( custom fit surgery)

*Minimally invasive approaches

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E mail- drvenkat@kneeindia.com

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