Joint Resurfacing- Custom Fit Knee Systems …• Bone stock preservation desirable over...
Transcript of Joint Resurfacing- Custom Fit Knee Systems …• Bone stock preservation desirable over...
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Custom Fit Knee Systems
Can a Patient Specific Approach Make a
Difference?
Tom Minas MD MSBrigham and Women’s Hospital
Harvard Medical School
Boston MA USA
Disclosures
ConforMIS, Inc.
Stock options
Stocks
Royalties
Joint Resurfacing-Individualized prosthetic in the Young Arthritic
The clinical problemUni +Bi - compartmental OA
• Frequent wear pattern in young arthritics
• Symptoms present in both compartments + PF
• Bone stock preservation desirable over conventional TKR in 50 YO with end stage bicomp OA
• Incidence?
• Ahlback 66 YO cohort - 1966
Ahlback, S.: Osteoarthrosis of the knee: a radiographic
investigation. Acta Radiologica, Suppl 277: 7-72, 1968.
Standard Uni Implants-Femoral Fit
`AP Length
Courtesy Dr. W. Fitz, Brigham and Women’s Hospital, Boston
Medial maleLateral maleMedial femaleLateral femalePreservationZimmer High FlexBiomet OxfordS+N Oxinium
Medial male
Lateral male
Medial female
Lateral female
Preservation
Zimmer High Flex
Biomet Oxford
S+N Oxinium
Standard Uni ImplantsMedial Tibial Fit
Courtesy Dr. W. Fitz, Brigham and Women’s Hospital, Boston
ML Width
Standard Uni ImplantsLateral Tibial Fit
Courtesy Dr. W. Fitz, Brigham and Women’s Hospital, Boston
MLWidth
M/G Result Example
Incomplete Tibial CoveragePotential for Implant Subsidence & Failure
Incomplete Femoral Coverage
Limitations in Femoral and Tibial Component Alignment
Femoral Bone Cuts
Potential Notch Impingement, ACL Damage
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Technical Aspects of Lateral“Off the Shelf” Uni
Patient-Specific Image-Implant Technology
Patient Specific Resurfacing Concept
• Resurface the femur, preserve bone and ligaments
• Achieve superior fit / maximize coverage in every patient
• Restore natural function via anatomic design
• Use imaging data to “pre-navigate” instruments
– Simplifies sizing & placement challenges
– Disposable, one-time use
Partial Knee Resurfacing
iUni Unicompartmental
iDuo
Bicompartmental
Pre-Navigated InstrumentationiUni Case Study
52 YO male
Lateral iUni Case Study Medial i Uni 45 YO Female disabling B Knee OA
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Post op Medial iDuo Lateral i Duo 58 YO femalei Duo Patient
6 weeks post op , full ROM
iUni / iDuo Kit
Primary Benefits:
• Reduced steps, reduced trialing
• Reproducible technique via iJigs
• Simplified, integrated balancing
• Short learning curve
• Highly efficient OR management
Primary Drawbacks:
• Cartilage removal
OR Experience
iTotal Customized Knee
System
What has really changed in TKR since the 1980’s?
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Why iTotal?Although longterm implant survivorship is high..The Gap in Patient Satisfaction after Primary TKA
Percent of Patients Not Satisfied After Primary TKA
Symmetric CR “Off the Shelf” Implant
18 mm IC distance for Patella tracking in deep flexion
• Overhang on PCL• Uncovered MFC
Distal and Posterior Offset –Joint Surface
Distal Posterior
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Principles for surgical Technique for Symmetric Implants
• Create a symmetric rectangular extension and flexion gap from a trapezoidal assymmetric gap to accomodate the implant
• Release the tight sides and stuff the loose sides
• Use the epicondylar axis to orientate the implant and Whiteside’s line to confirm
• Ensure the tibial cut is parallel to the flexion gap at 90 degrees to have a balanced knee
• But will the implant geometry resemble the patients? or Mid-flexion instability?
• Mechanical Axis Alignment
• Patient‐Specific Fit
•Restoration of Articulating Geometry – (J Curves, medial and lateral joint lines and offsets)
•Restore ligaments to original state
• Bone Preservation
• Wear Optimized Design
iTotal Design Rationale
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Preservation of the Patient’s Natural ‘J’ Curves and therefore kinematics
The patients natural ‘J’ curves(medial, lateral and trochlear) drive the femoral component geometry
iTotal Design Features• Maximize Bone Coverage;
• No implant overhang• No undersizing
• 6 Faceted Cuts• Patient individualized for
maximum bone preservation• 40 % reduction in bone
resection in a patient matched design
iTotal Design Features
•Tibial Plateau;
• Dual insert balancing capability
• Sagittal insert geometry derived from the femoral component, with increased medial conformity to promote normal motion.
• Complete proximal tibialcoverage.
• Orientation rotated for proper sagital motion
AFTERBEFORE
Virtual Alignment_CT Guided Pre-operative
The patient’s deformity is ‘Virtually Realigned’ prior to the design process starting.Correction is to mechanical alignment.
• DePuy Sigma distal femoral thickness = 9mm
• This example which is a Sz #3 equivalent implant has a 6.5mm distal femoral cut
ConforMIS “Delivery Model”Efficient, Pre-Sterilized, Disposable
Single use kit delivered a few days
before surgery
One reusable
instrument tray
Surgical Technique
• Classic Gap balancing technique
• or Measured resection
• Preserves natural joint line more accurately than traditional TKR-distal and posterior offset
• Minimal soft tissue balancing is required
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iTotal Patient Specific Surgical Plan iView 2.0 Surgical Technique iTotalPre operative x-rays
Final ComponentsPost op xray OA Valgus Knee
Postop – for Valgus OA Experience to date- iTotal
Ease for staff
Jigs accurate
Trust trials and remove all overhanging osteophytes
Minimal soft tissue balancing
Excellent intraop stability with no midflexion laxity
Minimal blood loss
Discharge home day 1-2 post op
Excellent early patient satisfaction
Must still do aggressive rehab
iTotal – 21st Century Technology
• iTotal Custom implant- joint surface –”J” curve and ligament restoration
• Prenavigation for alignment and traditional orthogonal axes bone cuts - maintains established principles of knee replacement.
• iJigs- accurate customized , disposable individualized extramedullary instruments