I-Assist guided Verilast Knee
Durable knee replacement for young patients
FRCS, M.Ch Orth, DNB Orth, MS Orth
• Ms. PM from Gujarat
• 32 years
• Suffering from Avascular
necrosis of Right knee
• Had consulted several
• 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
• Underwent I Assist guided
Verilast Knee replacement in
Key concepts in this presentation
• I –Assist
• Verilast knee– What is it? How does it reduce
• How I-Assist and Verilast combine to lower
wear and increase durability in young
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
• It uses surgical instruments and position sensors
to determine alignment axes in relation to
• 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
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
• It guides the surgeon to get perfectly aligned cuts intra
• It gives zero error cuts and again validates it in the next
• Thus the surgeon gets the right fit during the surgery
• 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
• 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
Mal-aligned car tyre
Wear on the inside
Properly aligned Knee replacements
Implant is perpendicular to the ground
Why do young patients need a knee
• Rheumatoid arthritis (common)
• Post traumatic arthritis (common in India and
• 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 firstname.lastname@example.org
Young patients wear away their total joints more
• than their older colleagues
• Wear is proportional to
• Young patients walk on
average up to 50% more
than older patients.
• Usage leads to increased
• Poly wear leads to aseptic
Patient age Average of
< 60 years 1200,00
> 60 years 800,00
Age & activity after THR/TKR
Problems of knee replacement in
• 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
Prosthetic life prolongation
Wear is an issue. Steps to reduce wear
• Bearings- alternate bearings like oxidized
• Poly ethylene – X LP poly, anti oxidants, thickness.
• Accuracy of component placement- ? Navigated
Options for change
• Change femoral
instead of routine
Cobalt Chrome )
• Change Poly insert
Combination is known as
• Meets requirements for ideal TKR
• ↓ 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
Oxygen Enriched Metal
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
wear by upto 89% in an
when compared to
Oxidized Zirconium- Best of both worlds
(Ceramic & Metal)
• Strength of Cobalt chrome
• Low coefficient and scratch resistance of
• Non brittle as the ceramic layer is part of the
• Decrease wear is the main advantage.4900
less volumetric wear.
• 160 times smoother.
Verilast CR knee
• Femoral component made of Oxidized
• Plastic insert made of Cross linked poly
• Cruciate retaining or CR knee removes less
bone than other knee.
Verilast knee has the potential to last
• Potential has to be harnessed by perfect
I Assist + Verilast knee
• Gives perfect alignment
during surgery itself.
• Alignment along with
durable materials like
Zirconium and Cross
increases life of a knee
replacement to 35 years.
• No need for future
revision surgery in young
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
• 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