I assist guided verilast knee replacement

transcript

E mail-drvenkat@kneeindia.com

I-Assist guided Verilast Knee replacement

Durable knee replacement for young patients

Dr.A.K.VenkatachalamFRCS, M.Ch Orth, DNB Orth, MS Orth

www.kneeindia.com

Patient details• Ms. PM from Gujarat• 32 years • Suffering from Avascular necrosis

of Right knee• Had consulted several surgeons

elsewhere.• Had advanced damage to the

knee with bone loss from the lower end of the thigh bone

• Was unable to walk without support for few preceding years.

• Underwent I Assist guided Verilast Knee replacement in September 2014.

Key concepts in this presentation

• I –Assist • Verilast knee– What is it? How does it reduce

wear?• How I-Assist and Verilast combine to lower

wear and increase durability in young patients?

1. What is the I-Assist?

• It is a Personalized guidance system designed to assist the surgeon in positioning a total knee arthroplasty implant components intra operatively.

• It uses surgical instruments and position sensors to determine alignment axes in relation to anatomical landmarks

• To thus precisely position alignment instruments & implant components relative to these axes.

I Assist components – 4 pods initially, now only 2 pods.

What is inside it?

• It consists of 4 half palm sized pods with electronic apps like

• Wi-Fi found in smart phones. • Gyroscope found in air planes. • The electronic sensors inside calculate the

alignment. The blinking lights on the display face indicate the correct position.

• Red light means improper position and Green light means proper position.

How does it work?

• It is inserted into the bones of the knee joint itself.

How does it work?

• After connecting it to the knee the surgeon moves the femur (thigh bone) in 13 different positions and the tibia ( leg bone) in 4 positions.

• It calculates the position by the electronic devices inside it.• The surgeon makes fine adjustments so that red lights turn to green. • Blinking green lights indicate zero percent error. • The surgeon can proceed to cut the bone confident that his

cuts will be perfectly aligned. • He can then finally place the implant components in the

correct alignment achieved and validated in the previous steps.

Advantages

• It guides the surgeon to get perfectly aligned cuts intra operatively.

• It gives zero error cuts and again validates it in the next step.

• Thus the surgeon gets the right fit during the surgery itself.• This ensures that the implant components are positioned

perfectly in correct alignment. • Surgeon focusses his eyes in the operating field itself and

not take his eyes away.• It thus saves time.

What does it differ from?

• Patient specific instrumentation• Computer assisted knee replacement

Alignment in Knee replacement• It is one of the factors that

ensures long life of the implant.

• A proper alignment means the implant is perpendicular to the ground.

• Mal aligned knee replacements tend to wear out sooner than normal.

• Even experienced surgeons can make errors in placement of the components.

Mal-aligned car tyre

Wear on the inside

Properly aligned Knee replacementsImplant is perpendicular to the ground

Why do young patients need a knee replacement ?

• Rheumatoid arthritis (common) • Post traumatic arthritis (common in India and

developing countries• Avascular necrosis (rare)

Less than 65 years 12 %

65 – 75 years 10 %

75 years 4 %

Total knees fail more often in young patients

Age and failure rates

Robertsson, Thesis Lund 2000 , Swedish arthroplasty registerE mail-drvenkat@kneeindia.com

Why ? Young patients wear away their total joints more

• than their older colleagues• Wear is proportional to

usage.• Young patients walk on

average up to 50% more than older patients.

• Usage leads to increased poly wear

• Poly wear leads to aseptic loosening

Patient age Average of steps/year

< 60 years 1200,00

> 60 years 800,00

Age & activity after THR/TKR

Problems of knee replacement in young

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

• We also know that the Redo operation will be technically a difficult operation than the primary. Result also will be inferior.

How to prolong the life of a knee replacement in a young patient ?

• The surgeon can do a TKR with a prosthesis that wears out slowly.

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

Prosthetic life prolongation

Wear is an issue. Steps to reduce wear • Bearings- alternate bearings like oxidized zirconium.

• Poly ethylene – X LP poly, anti oxidants, thickness.• Accuracy of component placement- ? Navigated

surgery

Options for change

• Change femoral counter-face ( Oxidized zirconium instead of routine Cobalt Chrome )

• Change Poly insert ( XLPE)

Combination is known as Verilast knee.

Oxidised Zirconium

• Meets requirements for ideal TKR• Smoother• ↓ Coefficient of friction• More scratch resistant• Less wear against both conventional and

highly cross linked poly ethylene.

What is it?• 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

500oCOxygenDiffusion

Oxygen Enriched Metal

Metal Substrate

Oxidized Zirconium properties• 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.

Wear properties of Oxidized zirconium

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

Oxidized Zirconium- Best of both worlds (Ceramic & Metal)

• 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.

Verilast Knee

Verilast CR knee

• Femoral component made of Oxidized Zirconium

• Plastic insert made of Cross linked poly ethylene (XLPE)

• Cruciate retaining or CR knee removes less bone than other knee.

Verilast knee has the potential to last 35 years

• Potential has to be harnessed by perfect alignment.

I Assist + Verilast knee

• Gives perfect alignment during surgery itself.

• Alignment along with durable materials like Zirconium and Cross linked poly-etheylene increases life of a knee replacement to 35 years.

• No need for future revision surgery in young patients.

What is innovative in my procedure?

• Earlier Verilast knee was implanted with an earlier smart tool called “ Visionaire” patient specific instruments from the same company.

• Patient specific instruments manufacturing take time.• Technique is operator dependent.• Also used with Computer navigation – Surgeon has to keep shifting

his gaze from the operating field to the computer and back.

• This is the first time that it is used with a user friendly I –Assist smart tool.

• I-Assist and Verilast belong to different companies.• This is the first time that high end products from different companies

have been combined to hopefully give a high end durable product.

Thank you

I assist guided verilast knee replacement

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