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.


*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.


*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.


*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


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


*Cycling

*Calisthenics

*Swimming

*Low-resistance rowing

*Skiing machines

*Walking & Hiking

*Low-resistance weightlifting

Knee society


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

Knee society


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.


Wear in TKR’s

Patient

Polyethylene

DesignTechnique

Counter face


*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


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

*Proved lowering of long term wear rates


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.


*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


*Sequentially irradiated and annealed ( not melted polyethylene)

*Significant wear reduction

*No mechanical changes

*Same poly used for hips and knees


*Scratches are bad - Ideally try to eliminate


*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


*Femoral *Cobalt Chrome

* scratching is common

*From cement and poly

*Care to remove cement after TKR.


*Meet requirments for ideal TKR

*Smoother

*↓ Coefficient of friction

*More scratch resistant

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


*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)


*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


*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.


*Equivalent to Cobalt Chrome

*1000 pounds

*10 x 106 Cycles


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


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


*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.


*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.


*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.


*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


*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


*Skin incisions 4- 6 inches long.

*Midvastus, sub vastus, minimally invasive quad splitting.


*46 year old Indian housewife.

*Left gender specific high flex knee replacement


*Zero error Component placement

*Extra articular deformities- one stage replacement


*Patient specific instrumentation

*Requires MRI scan & Standing x rays

*Eliminates 23 steps from TKR.

*For distal femoral cut & proximal tibial cut.


Rheumatoid arthritis 38 year old patient


*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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knee replacement in young patients

Health & Medicine

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increased poly wear

older patients

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young patients failure

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