Conformis Patient Specific Custom Total Knee Replacement

Moby Parsons, MD
The Knee Hip and Shoulder Center
333 Borthwick Avenue, Suite 301
Portsmouth, NH 03801
Tel: (603) 431-5858
Fax: (603) 431-5818
www.orthopedicsnh.com
1

Conformis Patient-Specific Custom
Total Knee: Rationale, Design and Results
MK-02661-AF-3/13© COPYRIGHT 2013 ConforMIS, Inc.
One patient. One implant.

• Range of Motion
• Stability
• Fit
• Function
• Durability
• Longevity
What Patients Want

What Surgeons Want
Patient Satisfaction
Predictable Outcomes
Reproducible Outcomes
Few Complications

Current Results of Conventional Knee
Replacement
1 in 5 patients not
satisfied with results of
total knee replacement

Why iTotal?
1 in 5 Patients are Not Satisfied with the Results of Their TKA
11% 12%
15%
27%
25%
15%
19%
39%
0%
10%
20%
30%
40%
50%
Anderson
(1996)
Heck
(1998)
Hawker
(1998)
Bullens
(2001)
Noble
(2006)
Wylde
(2007)
Bourne
(2010)
Suda
(2010)
Percent of Patients Not Satisfied after TKA
6MK-02661-AF-3/13

Why iTotal?
The Next Challenge of TKA is to Close the Gap on Satisfaction and Pain
7
99% 97%
73% 69%
0%
20%
40%
60%
80%
100%
120%
Revision, excluding deep
infection
Revisions Revision and satisfaction
VAS< 80
Revision, lost to follow
up, pain VAS>20, and
Satisfaction VAS < 80
Success at 5 Years Using Different End Points1
1 Bullens PHJ et. al.; Patient Satisfaction After Total Knee Arthroplasty: A Comparison Between Subjective and Objective Outcome Assessments; J
Arthroplasty; 2001; Vol. 16; No. 6, pp. 740-747.
When patient satisfaction and residual pain are factored into the definition of a successful
TKA, the success rate of the procedure drops to ~70% at 5 years1

Traditional Knee Replacement
Functional Compromise
In a study of patients with TKR and an age matched control group, the TKR patients
reported difficulty performing a variety of activities compared to the control.1
1 Noble PC et al. Does Total Knee Replacement Restore Normal Knee Function?. Clin Orthop Relat Res. 2005;431:157-165.
8

Why iTotal?
Understanding Principle Drivers of Dissatisfaction
Early Implant Failure Residual Pain
Compromised
Function
• Leg alignment
• Poly wear
• Implant
engineering
• Component fit
• Internal rotation
of the femur/tibia
• Limited range of
motion & stiffness
• Knee instability
• Proprioception
Early failures only 1-2%,
but significant when
they occur
10-15% of TKA patients
have clinically significant
residual pain1,2
Dissatisfied patients
report that their knee
does not feel normal at
more than 2x the rate of
satisfied patients3
1 Brander VA et al. Predicting total knee replacement pain: A prospective, observational study. Clin Orthop Relat Res. 2003;416:27-36.
2 Katz JN et al. Association Between Severe Pain in the Early Months Following Total Knee Replacement and Functional Outcomes Over Five-Year
Follow-Up. World Congress of OA. Abstract 80.
3 Noble PC et al. Patient expectations affect satisfaction with total knee arthroplasty. Clin Orthop Relat Res. 2006;452:35-43.
9© COPYRIGHT 2013 ConforMIS, Inc.MK-02661-AF-3/13

Top 10 Reasons for Early Knee
Replacement Failure
1. Unrealistic expectation/secondary gain
2. Wound healing problems
3. Prolonged observation of draining
wounds
4. Component malrotation
5. Infection
6. Varus tibial component position
7. Failure to correct mechanical axis of leg
8. Patellar maltracking
9. Failure to balance the soft tissues
10. Operating too early
*5 reasons due to mechanical, technical or implant related issues

Off-the-shelf implants cannot
account for patient variability
• Form a graph of anatomy
measurements from
multiple knees
• Draw a trendline through
the datapoints
• Pick 8 points along that line
that represent average

Problems with Traditional Implants
• Conventional implants do not
address the variability in
femur and tibia sizes across
the population
• Each implant company differs
in how its generic sizes
address this anatomic
variability
• Some are way off the
spectrum which can lead to
problems with implant fit
12

Size Salad
Conventional implants have to allow multiple sizes to be
interchangeable to achieve proper fit.
This may have implications for performance of the implant

Poor Implant Sizing and Fit
• Poor implant fit can lead to
overhang of either the
femoral or tibial
component
• With traditional implants
up to 57% of patients have
overhang of one
component > 3mm
Overhang is painful
• 27% of persistent pain due to
femoral overhang

The Challenge of Fit
J Bone Joint Surg Am. 2010;92:1115-1121.

Curvature of the Femoral Component –
who is right?
• No consensus about
which femoral
curvature is better in
terms of range of
motion, stability and
strength
Studies have also shown that standard TKR geometry, including
single radius designs, alter knee kinematics.1
1 Bull AM, Kessler O, Alam M, et al. Changes in kinematics reflect the articular geometry after arthroplasty. Clin Orthop Relat Res. 2008;466(10):2491-9.

In Vivo Kinematics for Subjects Implanted
With Traditional Off-the Shelf TKA
Biomet VanguardZimmer NexGen Stryker Triathlon
• In a normal knee the femur rolls back on the tibia during
flexion
• These off-the-shelf knees demonstrate paradoxical
motion as the femur rolls forward instead
• This can lead to soft tissue stress and knee pain

Off-the-shelf tibial components force a compromise
between maximal tibial coverage and proper rotational
alignment.
Implants were internally rotated an average of 8.8°
Only 30% were aligned within ±5° of proper rotation
Traditional Knee Replacement:
Tibial Rotation vs. Coverage
1Martin S, Noble P. et al. Optimizing Tibial Coverage is Detrimental to Proper Rotational Alignment. AAHKS 2012: Poster #22

The Challenge of Tibial Rotation vs. Coverage
Off-the-shelf tibial components force a compromise between maximal tibial
coverage and proper rotational alignment. When optimized for coverage1:
• Implants were internally rotated an average of 8.8°
• Only 30% were aligned within ±5° of proper rotation
© COPYRIGHT 2013 19
1Martin S, Noble P. et al. Optimizing Tibial Coverage is Detrimental to Proper Rotational Alignment. AAHKS 2012: Poster #22
Maximal
Coverage,
Improper
Rotation
Proper Rotation,
Downsized to
Prevent
Overhang
Off-the-Shelf
Designs
MK-02661-AF-3/13

The Challenge of Component Rotation
• Patients with internal component rotation are 5x more likely to
experience anterior knee pain after TKA and have PF
complications
• Barrack RL, et al; Component rotation and anterior knee pain after total knee arthroplasty. Clinic Orthop and
Relat Res. 2001
• Berger RA, et al; Malrotation causing patellofemoral complications after total knee arthroplasty. Clinic
Orthop and Relat Res. 1998.
• Excessive internal tibial component rotation, in particular,
explains approximately half of all residual pain in TKA and can be
source of functional deficit
• Nicoll D, Rowley DI. Internal rotation error of the tibial component is a major cause of pain after total knee
replacement; J Bone Joint Surg [Br]; 2010;92(9):1238-40.
• Bedard M et. al.,. Internal Rotation of the Tibial Component is Frequent in Stiff Total Knee Arthroplasty. Clin
Orthop Relat Res. 2011
• Lützner J et al., Patients with no functional improvement after total knee arthroplasty show different
kinematics. International Orthop. 2012.

The Challenge of Component Rotation
J Bone Joint Surg BR. 2010;92-B:1238-44

Why do we need personalized solutions?
No two knees have the same size or shape or wear pattern

One Patient: One Implant
The Only Patient-Specific Custom Fit Total Knee

Conformis iTotal Design Rationale
• Patient-Specific Fit
• Patient-Specific Positioning
• Mechanical Axis Alignment
• Bone Preservation
• Wear Optimized Design
• Efficient Delivery Model

• Mechanical Axis Alignment
• Patient-Specific Fit & Positioning
• Restoration of Articulating Geometry
• Bone Preservation
• Wear Optimized Design
• Efficient Delivery Model
iTotal Design Rationale

iAlignTM Alignment Approach for Jigs & Implants
Designed to Neutral Mechanical Axis
• Virtual alignment to mechanical
axis using anatomic landmarks
 Center of Hip
 Center of Femur
 Center of Tibia
 Center of Ankle
• Tibial Rotational Alignment
 CT used to set to the
anatomic tibial axis
Virtual Alignment to Mechanical
Axis in Coronal Plane
Hip
Knee
Ankle

Respect Patient’s Condylar Geometry
iShapeTM Sagittal ‘J’ Curves
Studies have also shown that standard TKR geometry, including single radius designs, alter knee
kinematics.1 With iTotal, the patient’s anatomic ‘J’ curves, corrected for deformity, provide the basis
for the implant design.
Patient’s natural articulating
geometry extracted from 3D
femoral anatomy
Curves are corrected for deformity
and then used as the basis for
femoral implant design
27
1 Bull AM, Kessler O, Alam M, et al. Changes in kinematics reflect the articular geometry after arthroplasty. Clin Orthop Relat Res. 2008;466(10):2491-9.
© COPYRIGHT 2013 ConforMIS, Inc.MK-02661-AF-3/13

Restores Normal Kinematics
Studies have shown that the natural Flexion-Extension Axis (FEA) and the Transepicondylar
Axis (TEA) are not the same and differ an average of 4.6 degrees1
iTotal respects each patient’s native condylar geometry, allowing the knee to rotate about
its natural axis
1 Eckhoff D et al. Difference Between the Epicondylar and Cylindrical Axis of the Knee. Clin Orthop Relat Res. 2007; Aug(461) 238-244.
28© COPYRIGHT 2013 ConforMIS, Inc.
TEA
FEA
TEA
FEA
MK-02661-AF-3/13

Condylar Offset and Joint Line
Approximating a patient’s medial and lateral ‘J’ curves naturally retains their condylar offset with keeps the
joint line at the correct position
Joint line movement has been shown to alter kinematics and lead to mid-flexion instability2.
11Poilvache et al. Rotational Landmarks and Sizing of the Distal Femur in Total Knee Arthroplasty. Clin Orthop Relat Res 1996, 331, pp 35-46.
2 Martin J, Whiteside L. The Influence of Joint Line Position on Knee Stability After Condylar Knee Arthroplasty. Clin Orthop Relat Res 1990, 259, pp 146-
156.
Distal Offset
Posterior Offset

Restore Patient’s Geometry
Restores Normal Kinematics and Stability
1 Patil, et al; Patient-Specific Implants and Cutting Guides Better Approximate Natural Kinematics than Standard Total Knee Arthroplasty. ORS Annual
Meeting 2013, Vol.38. Abstract # 0965.
In a study comparing iTotal G2 to an off-the-shelf TKR, iTotal G2
• More closely replicated each patient’s normal femoral rollback throughout ROM. 1
• Resulted in knee stability that was closer to the normal knee.1
MK-02661-AF-3/13

Symmetric total knee designs force compromises between complete coverage and overhang.
Variations in anatomy make it virtually impossible to fit in all areas of the femur.
Personalized Position, Shape & Fit
Patient matched, anatomic femur to avoid sizing compromises
An iTotal femoral component has an
image based, patient specific design
that follows the anatomy
The personalized fit helps take surgeons
out of the sizing compromises typical in
traditional TKA

Patient matched, anatomic femur to avoid sizing compromises
Personalized fit can help avoid soft tissue issues such as (e.g., popliteus tendon “popping”),
which traditionally would require releases to correct1
1 Barnes, C.L., Scott, R.D.; Popliteus Tendon Dysfunction Following Total Knee Arthroplasty; J Arthroplasty; 1995; Vol. 10; No. 4, pp. 543-545.

In Vivo Kinematics for Subjects Implanted With
Either a Traditional or Personalized TKA
Biomet VanguardZimmer NexGen Stryker Triathlon
By matching condylar geometry, Conformis leads to more normal
femoral roll back compared to off-the-shelf designs

• 44% of off-the-shelf knees
demonstrated paradoxical anterior
slide during flexion
• 91% of Conformis patient-specific
implants replicated normal knee
motion

6 Cut Design to Maximize Bone Preservation
Comparison to standard total knee systems
Medium Size Femoral Implant Thickness
(Measurements
in mm)
Size
A-P
Length
Distal
Medial
Distal
Lateral
Posterior
Medial
Posterior
Lateral
ZMH NexGen E 62 9 9 9.3 9.3
J&J PFC Sigma 3 61 9 9 8 8
SNN Legion 5 62 9.5 9.5 9.3 9.3
SYK Triathlon PS 4 62 8.5 8.5 8.5 8.5
SNN Journey 5 62 9.5 7.0 9.5 7.4
Average for Sample - 61.8 9.1 8.6 8.9 8.5
Average for
ConforMIS Sample*
- 62.0 6.9 6.8 5.8 5.8
Delta (Standard vs.
ConforMIS)
-2.2 -1.8 -3.1 -2.7
• 28% volumetric
bone preservation
advantage for
iTotal
36
ConforMIS data on file.
*sample size is average of 5 representative designs matched for AP length.
© COPYRIGHT 2013 ConforMIS, Inc.MK-02661-AF-3/13

Designed for proper rotation and fit to avoid known causes of pain
Rotational Alignment
Center of baseplate set to the center of the medial and lateral
condyles, shown to be a reliable method of tibial component
rotation1,2
1 Cobb JP; The Anatomical Tibial Axis – Reliable Rotational Orientation in Knee Replacement; J Bone Joint Surg [Br]; 2008;90-B:1032-8.
2 Lützner et al.: Rotational alignment of the tibial component in total knee arthroplasty is better at the medial third of tibial tuberosity than at the medial border. BMC
Musculoskeletal Disorders, 2010 11:57.
3 Chau R, et. al.,; Tibial component overhang following unicompartmental knee replacement - does it matter?; Knee; 2009; V16:pp. 310-313.
Patient-Specific Shape & Fit
Implant profile is then matched to cortical rim, with slight
relief to allow +/- 5º intra-operative adjustment without
implant overhang, a potential source of pain.3

Femur Matched Offset Polys
High contact area, low contact stress with low constraint
• Patient-specific fit for each
condyle maximizes size of
contact surface
• Coronal radius on the
femur and poly designed
for high congruency
• Broad coronal radius
allows for high contact
area, without high
constraint

Engineered for Low Contact Stress
Contact Area vs. Fixed and Mobile Bearing Designs
1 ConforMIS test data on file. TD-2638
2 DePuy Orthopedics, Inc. marketing literature. Data for Sigma fixed bearing is at 15° flexion as 0° flexion was not reported.
3 Tibial Plateau Surface Stress in TKA: A Factor in Clinical Failure. Postak et al. Orthopaedic Research Laboratories. The Mount Sinai Medical Center
Contact area (mm2) At Varying Degrees of Flexion
436
271
337
270
116 123
671
242
189
0
100
200
300
400
500
600
700
800
0° Flexion 60° Flexion 90° Flexion
iTotal G2
Sigma (Fixed Bearing)
LCS (Mobile Bearing)
2
3
1
Due to its broad coronal radius and coverage, iTotal offers contact area throughout the
range of motion that is competitive with mobile bearing, in a fixed bearing design.
2

Intercondylar notch width
driven by patient anatomy
rather than need to
accommodate upsizing and
downsizing
Wide coronal geometry for
high conformity to poly with
low constraint
Lowered lateral
trochlea to
decompress soft
tissue
High conformity dome
Patello-Femoral joint
Engineered Design Features
Wear optimization and engineered function
Extended trochlear groove
to guide patella in deep
flexion

Patient imaging study
at validated center
3D Image processing Implant & iJig® design
& manufacture
One package
delivered for
Surgery
Implant Request Form
(IRF) submitted
ConforMIS “Delivery Model”
A Model for a More Efficient Joint Replacement System
6 Week Delivery Time
Implant & iJig®
design &
manufacture
MK-02661-AF-3/13

ConforMIS “Delivery Model”
Efficient, Pre-Sterilized, Disposable
Single use kit
delivered a few
days before
surgery
One reusable
instrument tray
iTotal G2 instrument
set and implants
provided for use in
the OR

I View Patient-Specific Surgical Plan:
Customized surgical plan for each case

iView Patient-Specific Surgical Plan

iTotal – True Patient Specific Fit and Shape

Clinical Data Reinforces Anecdotal Experience
• Increased patient satisfaction
• Improved kinematics
• Better function

• Overall OR time
• iTotal lower by 16 mins
(p=0.028)
• Ligament releases
• iTotal 5.7% vs. Triathlon 20%
• Length of stay
• iTotal - 1.6 days shorter
(p=0.003)
• Post-op recovery
• iTotal – faster recovery (see
graph)
• Blood hemoglobin
• iTotal – lower drop in
hemoglobin
Comparison of Hospital Metrics and Patient
Reported Outcomes for Patients with Customized,
Individually Made vs. Conventional TKA
Results – OR Time, Ligament Releases, LOS
5.2*
6.2* 6.3*6.9
8.1
8.7
0
1
2
3
4
5
6
7
8
9
10
Level Walking Stairs Flexion to 90
degrees
AverageTime(Days)
iTotal CR
Triathlon
* Statistically significant.

83*
94.3*
73.7 74.2
0
10
20
30
40
50
60
70
80
90
100
KOOS (%) Satisfaction (%)
iTotal CR
Triathlon
* Statistically significant.
Comparison of Hospital Metrics and Patient
Reported Outcomes for Patients with Customized,
Individually Made vs. Conventional TKA
Results – Patient Outcomes

• More iTotal patients with excellent objective scores
• More OTS patients with poor objective scores
84.34%
10.84%
2.41% 2.41%
Objective KSS - iTotal
Excellent Good Fair Poor
80.62%
11.63%
1.55% 6.20%
Objective KSS - OTS
Excellent Good Fair Poor
Odds ratio to have excellent/good
Objective KSS score: 1.7x greater CIM
vs. OTS
Odds ratio to have poor Objective KSS
score: 2.6x greater OTS vs. CIM
Multicenter Analysis of Patient Outcomes and Functional Tests for Patients
with Customized, Individually Made or Off-the-Shelf TKR
Results – Objective Metrics (KSS)

4 hours after right total knee
replacement
Same Day Surgery Total Knee Replacement
Conformis is part of a rapid
recovery paradigm
 Better patient education
 Patient preparation and optimization
 Advanced pain management
 Improved anesthesia techniques
 Less invasive surgery
 Patient-specific implants
 Early mobilization and range of motion
 Advanced discharge planning

Partial Knee Replacement P A R T I A L K N E E
I M P L A N T O P T I O N S
• 20-40% of all TKRs are performed on
people who could have been treated
with a partial knee replacement
• Patients tend to prefer UKA to TKA
– Preserves the ACL and PCL
– Preserves more bone and cartilage
– Less invasive surgery, less blood
loss
– Smaller incision
– Faster recovery

Unicompartmental Knee
Replacement iUni® G2
P A R T I A L K N E E
I M P L A N T O P T I O N S
The only patient-specific
unicompartmental knee replacement
• Designed to treat medial or lateral
tibiofemoral osteoarthritis
• Provides a customized fit specific to your
knee
• Designed to mimic the natural shape of
your knee to help retain more of your
natural function
• Allows for a less traumatic procedure and
fewer bone cuts to preserve more of your
natural knee for future treatment, if
necessary

Conformis vs Makoplasty
Makoplasty
 Still uses ”off-the-shelf”
implant
 Extra holes drilled in
bone for trackers
 Takes longer than
conventional surgery
Conformis
 Patient-specific implant
 No additional holes in
bone
 Faster and more efficient
work-flow

To Summarize
• Still too many off-the-shelf TKR patients dissatisfied
• Clinical studies support what I’ve seen in my practice
• Increased patient satisfaction
• Normal knee kinematics
• Better function

Thank You
For more information visit
www.conformis.com
www.orthopedicsnh.com

Conformis Patient Specific Custom Total Knee Replacement

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Similar to Conformis Patient Specific Custom Total Knee Replacement

Similar to Conformis Patient Specific Custom Total Knee Replacement (20)

More from Moby Parsons

More from Moby Parsons (9)

Recently uploaded

Recently uploaded (20)

Conformis Patient Specific Custom Total Knee Replacement