THE FUTURE OF TOTAL KNEE REPLACEMENT
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THE FUTURE OF TOTAL KNEE REPLACEMENT
History of total knee replacement
Total knee replacement was invented
• to cure pain of arthritic knees• restore stability and motion
History of total knee replacement
TKR followed two different approaches
Anatomic approach vs functional approach(preserving soft tissues (sacrificing soft tissues) and knee physiology)
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History of total knee replacement
The anatomic approach
Polycentric knee (Gunston 1970)
History of total knee replacement
The anatomic approach
Bi-lateral uni-compartmental components are difficult to align well and difficult to fix to bone
Patello-femoral arthritis must be treated - patellar flange on femoral component - patellar component
History of total knee replacement
Functional approach : hinge arthroplasty
Waldius Judet Shiers Young Guepar
History of total knee replacement
Functional approach : hinge arthroplasty
Absence or substantial restriction of axial or varus-valgus rotation is detrimental to fixation Rotational forces will be conducted to the bone-prosthesis interface and loosening is more likely to occur
Free anatomic motion is needed to preserve fixation !!!
History of total knee replacement
Free anatomical motion in fixed bearing knee replacement systems is possible only when the articulating surfaces are not congruent
• Polyethylene wear became an important failure mechanism of total knee prostheses, due to
- high contact stress on - small contact areas
The problem of fixed bearing knee prostheses
minimal constraint against displacement results in small contact areas and high contact stresses > increased risk of polyethylene articulation damage.
The LCS Story 1977-2007
History of mobile bearing total knee arthroplasty
The solution of the industry
was compromise: creating more conformity between components still allowing varus-valgus rotation and some axial rotation
For many total knee systems this situation still exists today!
History of mobile bearing total knee arthroplasty
Mobile bearings
> large contact areas > low contact stress > minimal wear
> free anatomical motion > minimal constraint forces > minimal loosening
> results better ?> surgery more difficult ?
Total knee arthroplasty today
Swedish Knee Arthroplasty Register
Total knee arthroplasty today
Swedish Knee Arthroplasty Register
TKA has been very succesful ?
1% of all knee prostheses are failing every year !
(Robertson, Swedish Knee Arthroplasty Register,1999)
Total knee arthroplasty today
“Why are total knee arthroplasties failing today?” Peter F. Sharkey, MD; William J. Hozack, MD; Richard H. Rothman, MD,
PhD; Shani Shastri, MD; Sidney M. Jacoby, BA. CORR Nov 2002:7-14
Total knee arthroplasty today
“Current etiologies and modes of failure in total knee arthroplasty revision”
Kevin J. Mulhall, Hassan M. Ghomrawi, Sean Scully, John J. Callighan,
Khaled J. SalehClinical Orthopaedics and Related Research 446, pg 45-50, 2006
Total knee arthroplasty today
Modes of failure
Surgical insufficiency is the most common cause for early failure of an arthroplasty
Wear of polyethylene is the most important reason for failure after 5 years
Instability has become an important reason
Total knee arthroplasty today
Computer assisted surgery (CAS) and Minimally invasive surgery (MIS)
are they bringing us any improvement or are we performing a lot of wishful thinking ?
Total knee arthroplasty today
What do we want ?
• knees without pain• good passive and dynamic stability• knees with anatomic motion• knees with an better overall function
Total knee arthroplasty today
How can we achieve improvement ?
• with today’s surgery ?• with today’s prostheses ?
Total knee arthroplasty today
Total knee arthroplasty today
Do we want a rotating platform + posterior stabilisation ?
Total knee arthroplasty today
Do we want to retain the cruciate ligaments, replace just what is needed ?
1: Mechanical axisThe AP Femoral cuts are also made
at right angles to the mechanical axis
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