The Charnley Kerboull hip system The Charnley Kerboull hip system Results of a 30 years experience Results of a 30 years experience in cemented fixation in cemented fixation L Kerboull, M Kerboull. L Kerboull, M Kerboull. Marcel Kerboull Institute Marcel Kerboull Institute Imk-forum.com Imk-forum.com
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The Charnley Kerboull hip system Results of a 30 years experience in cemented fixation L Kerboull, M Kerboull. Marcel Kerboull Institute Imk-forum.com.
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The Charnley Kerboull hip systemThe Charnley Kerboull hip system
Results of a 30 years experienceResults of a 30 years experience in cemented fixationin cemented fixation
L Kerboull, M Kerboull.L Kerboull, M Kerboull.
Marcel Kerboull InstituteMarcel Kerboull Institute
Imk-forum.comImk-forum.com
introductionintroduction
• basis of the mechanical principles of the basis of the mechanical principles of the cemented fixation cemented fixation
• Current ControversiesCurrent Controversies• Subsidence and collarSubsidence and collar• Surface finishSurface finish• Cementing technique and cement thicknessCementing technique and cement thickness• Classification of cemented stemClassification of cemented stem
• What must be a perfect cemented stem What must be a perfect cemented stem
• Clinical Results to support our theoryClinical Results to support our theory
The original charnley stem : the golden The original charnley stem : the golden standardstandard
8 % of stem debonding8 % of stem debonding– radiolucent line between cement radiolucent line between cement and stem in zone 1 of Amstutzand stem in zone 1 of Amstutz
– cement mantle crack cement mantle crack at the stem tip levelat the stem tip level
even so often asymptomatic, even so often asymptomatic, it was for us. it was for us. a failure of the primary stem fixationa failure of the primary stem fixation
Introduction : Current optionsIntroduction : Current options
• Modern Cementing technique and cement Modern Cementing technique and cement mantle minimal thickness were identified as mantle minimal thickness were identified as solutions to address the problem of femoral solutions to address the problem of femoral stem loosening.stem loosening.
• Our mechanical theory of the cemented fixation Our mechanical theory of the cemented fixation was initiated in 1972 and is very differentwas initiated in 1972 and is very different
Bone, cement and stem make Bone, cement and stem make a composite structurea composite structure- All mentioned materials have different E-Moduli- All mentioned materials have different E-Moduli
- Each of these materials had different strains under cyclic axial - Each of these materials had different strains under cyclic axial and torsional load that induce micromotion at the interfacesand torsional load that induce micromotion at the interfaces
- Micromotion primary occurs at the stem-cement interfaceMicromotion primary occurs at the stem-cement interface
- Micromotion can only be partially absorbed by cement Micromotion can only be partially absorbed by cement elasticityelasticity
- Micromotion is settled by the stem which is the stiffest Micromotion is settled by the stem which is the stiffest component component
MechanicalMechanical basis basis of stem cemented fixationof stem cemented fixation
The mechanical stability The mechanical stability
of this composite of this composite
Is depending on the mechanical properties Is depending on the mechanical properties and shape of the 3 componentsand shape of the 3 components
But the most rigid component will always But the most rigid component will always have the most positive or negative influencehave the most positive or negative influence
How to improve stem cemented fixationHow to improve stem cemented fixation
Improve mechanical properties of cement ?Improve mechanical properties of cement ?
« initial migration seems to be independent of « initial migration seems to be independent of the type of cement and of its viscosity »the type of cement and of its viscosity »
The influence of cement viscosity on early migration of The influence of cement viscosity on early migration of a tapered polished femoral stema tapered polished femoral stem
Glyn-Jones and collGlyn-Jones and collInt Orthop 2003 ; 27: 362-5Int Orthop 2003 ; 27: 362-5
In fact, cement was, is and will ever beIn fact, cement was, is and will ever be the weakest component of this composite the weakest component of this composite
structurestructure
How to improve stem cemented fixationHow to improve stem cemented fixation
We found the answer to this We found the answer to this questionquestionfrom the observation of our from the observation of our Charnley first casesCharnley first cases
Dysplastic femurDysplastic femurVery Thin cement Very Thin cement
Debonding 0 %Debonding 0 %
25 y
2 Thickening cement layer was not for 2 Thickening cement layer was not for us the best choiceus the best choice
• this observation suggested that a stem fitted to cortical this observation suggested that a stem fitted to cortical bone with a thin cement layer might improve the bone with a thin cement layer might improve the cemented fixationcemented fixation
• It was also evident that an undersized stem used to get a It was also evident that an undersized stem used to get a thick cement mantle was not the good solution to prevent thick cement mantle was not the good solution to prevent distal migration, because even thicker the cement was distal migration, because even thicker the cement was not enough resistant to face the stresses transmitted by not enough resistant to face the stresses transmitted by the stem.the stem.
« initial migration seems to be independent of the thickness « initial migration seems to be independent of the thickness of the cement mantle »of the cement mantle »
Influence of cement viscosity and cement mantle thickness Influence of cement viscosity and cement mantle thickness on migration of the Exceter total hip prosthesison migration of the Exceter total hip prosthesis
How to improve stem cemented fixationHow to improve stem cemented fixation
1.1. Improve mechanical properties of cement Improve mechanical properties of cement 2.2. Increase cement layer thicknessIncrease cement layer thickness3.3. Improve cementing technique Improve cementing technique 4.4. Modify stem design to decrease stresses Modify stem design to decrease stresses
supported by cement supported by cement 5.5. Improve bone-cement interfaceImprove bone-cement interface6.6. Look for a secondary fixation through a Look for a secondary fixation through a
distal migration : subsidencedistal migration : subsidence7.7. Increase link between stem and cement Increase link between stem and cement
Bone is twin : cortice and cancellousBone is twin : cortice and cancellous
Does cancellous bone is able to carry the load ?Does cancellous bone is able to carry the load ?NO : Ebramzabeh E and coll : the cement mantle in total hip arthroplasty : NO : Ebramzabeh E and coll : the cement mantle in total hip arthroplasty :
analysis of long term radiographic resultsanalysis of long term radiographic resultsJBJS 1994 76-A,77-87JBJS 1994 76-A,77-87
Effect of aging: Effect of aging: lowering of mechnical properties of cancellous bonelowering of mechnical properties of cancellous bone
Are Interdigitations between cement and cancellous bone necessary ?Are Interdigitations between cement and cancellous bone necessary ?
Yes if you use a force loaded stem that submit the cement to high tensile Yes if you use a force loaded stem that submit the cement to high tensile stressstress
No, if cement is only submitted to a low level of compressive stresses by a No, if cement is only submitted to a low level of compressive stresses by a canal filling stem cemented line to linecanal filling stem cemented line to line
• Further under loading and aging cancellous bone Further under loading and aging cancellous bone undergoes compression and becomes unevenundergoes compression and becomes uneven
• In this situation, the cement mantle is subjected In this situation, the cement mantle is subjected to bending and tensile stresses and will crack.to bending and tensile stresses and will crack.
• So, removing the cancellous in the superomedial So, removing the cancellous in the superomedial part of the metaphysis and in the distal canal part of the metaphysis and in the distal canal gives the cement an even and rigid base and gives the cement an even and rigid base and prevents its crack under bending stressprevents its crack under bending stress
supported by cement supported by cement 6.6. Look for a secondary fixation through a Look for a secondary fixation through a
distal migration : subsidencedistal migration : subsidence7.7. Increase link between stem and cement Increase link between stem and cement
through a rough surfacethrough a rough surface
Solutions :Solutions :
Mechanical basis of the stem debondingMechanical basis of the stem debonding
High bending stresses in the supero medial High bending stresses in the supero medial part part break the cement mantlebreak the cement mantle
This ruptureThis rupturewidenswidens the proximal part the proximal part of the cement mantleof the cement mantledecreasesdecreases the shear stresses the shear stresses along the stemalong the stemincreasesincreases the vertical force on the distal cement the vertical force on the distal cement which breakes under tensile stress which breakes under tensile stress and finally and finally allowedallowed varus tilt varus tilt and subsidence of the stem and subsidence of the stem
Because it was for us the most logical way:Because it was for us the most logical way:
to decrease the level of stress within and at to decrease the level of stress within and at the cement stem and cement bone the cement stem and cement bone interfaces interfaces
to only subject the cement mantle to to only subject the cement mantle to compressive stressescompressive stresses
and consequently avoid the problems of and consequently avoid the problems of the cement layer thickness and resistancethe cement layer thickness and resistance
Three main modifications of the stem Three main modifications of the stem designdesignresulted in the MK 1resulted in the MK 1
1.1. Opening the stem-neck angle to Opening the stem-neck angle to 130° instead of 125°130° instead of 125°
2.2. widening the proximal part of the widening the proximal part of the stemstem
3.3. Increasing the range of sizesIncreasing the range of sizes
5 Modify stem design5 Modify stem design
CCD angle & equal neck length
Geometrical dependence of CCD and cement mantle pressure
M1 M2
M1 < M2
Force in the superomedial partis higher with a flater CCD angledue to bigger offset
Stem CCD angle and cement loadingStem CCD angle and cement loading
5 Modify stem design5 Modify stem design
Opening the stem neck angle to 130°Opening the stem neck angle to 130°
to decrease the pressure on the supero medial and to decrease the pressure on the supero medial and infero lateral part of the cement mantleinfero lateral part of the cement mantle
• CCD angle
125° 130°
CharnleyCharnley KerboullKerboull
5 Modify stem design5 Modify stem design
Widening and thickeningWidening and thickening the stem proximal part the stem proximal part
to give it a double tapered shapeto give it a double tapered shape
with a cross-section sufficently decreasingwith a cross-section sufficently decreasing
(taper angle > 5°) (taper angle > 5°)
so thatso that
5 Modify stem design5 Modify stem design
Widening and thickeningWidening and thickening the stem proximal part the stem proximal part
–the shear stresses the shear stresses along the stem along the stem
would be would be progressively progressively transformed transformed
into their pressure into their pressure componentscomponents
–and the vertical distal and the vertical distal force force
would be would be dramatically reduceddramatically reduced
5 Modify stem design5 Modify stem design
5 modify the stem design: A large range 5 modify the stem design: A large range of sizesof sizes
1 to reconstruct a normal architecture in every case 1 to reconstruct a normal architecture in every case (limb length and abductor muscles off-set).(limb length and abductor muscles off-set).
2 to get a self alignment of the stem with the 2 to get a self alignment of the stem with the femoral diaphysis axisfemoral diaphysis axis
5 modify the stem design: A large range 5 modify the stem design: A large range of sizesof sizes
“ in our study, line to line stem without distal centralizer were better aligned than undersized stems fitted with a centralizer”
T Scheerlinck and collCT analysis of defects of the cement mantleAnd alignment of the stemJBJS 88 B,1 19-25
A large range of sizesA large range of sizes
Symmetrical anatomy
33 to have between to have between stem and femoral canalstem and femoral canalthe best fitthe best fit
to reduce load transmitted to reduce load transmitted to ciment layer to ciment layer
5 modify the stem design: A large range 5 modify the stem design: A large range of sizesof sizes
Under these conditionsUnder these conditions
Cement mantle, cement bone Cement mantle, cement bone interface are no longer subjected interface are no longer subjected to shear stresses to shear stresses
and micromotion is reduced to a and micromotion is reduced to a level tolerated by creep of cementlevel tolerated by creep of cement
With this canal filling stem, the With this canal filling stem, the double tapered shape is acting to double tapered shape is acting to decrease the stresses on the decrease the stresses on the cement, but with an undersized cement, but with an undersized stem the distal force increases and stem the distal force increases and the stem subsidesthe stem subsides
How to choose the appropriate size regarding to the canal filling concept
• According to the preoperative planning
• Not the largest one that will impose to ream the cortices but
• The first size that get– self alignment– primary stability
Ant. Post.Ant. Post.
Relatively thick > 2 Relatively thick > 2 mmmm
Med. Lat. Med. Lat.
Thin or very thin < 1 Thin or very thin < 1 mmmm
How is the cement mantle thickness How is the cement mantle thickness around a CMK stemaround a CMK stem
unevenunevenBut never incompleteBut never incomplete
T Scheerlinck and collCT analysis of defects of the cement mantleAnd alignment of the stemJBJS 88 B,1 19-25
Uneven cement mantle but never incompleteUneven cement mantle but never incomplete
And protected of overloading by the stem designAnd protected of overloading by the stem design
How to improve stem cemented fixationHow to improve stem cemented fixation
supported by cement supported by cement 6.6. Look for a secondary fixation through a Look for a secondary fixation through a
distal migration : subsidencedistal migration : subsidence7.7. Increase link between stem and cement Increase link between stem and cement
through a rough surfacethrough a rough surface
Solutions :Solutions :
How to improve the cemented stem How to improve the cemented stem fixation ?fixation ?
• If you consider subsidence as a positive event to lock the fixation of the stem in the cement mantle you will try to favourize it but you will need to reinforce the cement to lower the distal migration
• If you consider subsidence as a primary failure of the initial fixation you will try to protect cement of over loading to prevent distal migration and to protect the ciment the only possibility you have is to work on the stem design
Subsidence and collar ?Subsidence and collar ?
Is Subsidence a normal event ?Is Subsidence a normal event ? - probably - probably No forNo for the CMK which the CMK which is not designed to subside is not designed to subside
and does not subside.and does not subside.
« The French paradox »: Langlais, Ling, Kerboull, « The French paradox »: Langlais, Ling, Kerboull, Sedel. JBJS Br, 2003. Sedel. JBJS Br, 2003.
Why ??Why ?? - We choose the stem which best fills the medullary canal - We choose the stem which best fills the medullary canal there is no space for the stem to subside.there is no space for the stem to subside.- The stem does not subside due to the cohesion forces acting on - The stem does not subside due to the cohesion forces acting on
the two polished (cement/stem) surfaces and micromotion the two polished (cement/stem) surfaces and micromotion stays under its cement fracture levelstays under its cement fracture level
The collarThe collar may decrease the distal force applied to ciment plugmay decrease the distal force applied to ciment plugdoes not prevent migration if it occursdoes not prevent migration if it occursjust an intraoperative reference to set leg lengthjust an intraoperative reference to set leg length
Does CMK subsides ?Does CMK subsides ?
Long-Term Migration Using EBRA-FCA of Stems Cemented Line-to-Line According to the "French Paradox" PrinciplesHamadouche, Moussa; Kerboull Luc; Kerboull, MarcelORS 2008
The EBRA-FCA software is a validated method designed to assess migration of afemoral component through comparable pairs of radiographs. Accuracy has been reported to be better than ± 1.5 mm (95% percentile), with a specificity of100% and a sensitivity of 78% for the detection of migration of more than 1.0 mm, usingRSA as the gold standard
Does CMK subsides ?Does CMK subsides ?
Materials and Methods: In 1988 and 1989, 164 primary THA in 155 patients by the two seniors of us. mean age 63.8 ± 11.6 years. Polished CMK
Results: 73 patients (77 hips) still alive F.U 17.3 ± 0.8 years (15-18 years), 8 patients (8 hips revised for high polyethylene wear 66 patients (69hips) deceased8 patients (10 hips) lost to follow-up.
1689 radiographs (mean 10.3 per hip) were digitized. 263 (15.6%) excludedNo migration curve obtained for 22 of the 164 femoral components (13.4%).
Mean subsidence of the entire series was 0.63 ± 0.49 mm Using a 1.5 mm threshold for subsidence, 4 of the 142 stems have migrated. Using a threshold of 2 mm for subsidence, none of the 142 stems have migrated.
Does CMK subsides ? NODoes CMK subsides ? NO
this study demonstrates
that contrary to other cemented femoral components that have also provided excellent survival in the long term but frequently associated with stem subsidence,
The CMK Stem, a highly polished double tapered femoral component with a quadrangular cross-section and a collar, filling the medullary canal, and cemented with a simple technique
does not subside up to 18-year follow-up.
What is Subsidence ?What is Subsidence ?
Subsidence below 2 mm may be probably absorbed by cement creeping and contributes to lock the stem but overloads the cement
Subsidence over 2 mm always induces a fracture of the cement mantle and is a loosening that may be tolerated
Because distal migration without varus tilt is often well clinically tolerated that might explain the good survival of taper-slip stem if only revision is considered as a failure.
How to improve stem cemented fixationHow to improve stem cemented fixation
supported by cement supported by cement 6.6. Look for a secondary fixation through a Look for a secondary fixation through a
distal migration : subsidencedistal migration : subsidence7.7. Increase link between stem and cement Increase link between stem and cement
through a rough surface : surface finishthrough a rough surface : surface finish
Solutions :Solutions :
Why the polished stem became matt ?Why the polished stem became matt ?
•Initiation of stem loosening: Initiation of stem loosening:
debonding of the cement to prosthesis interfacedebonding of the cement to prosthesis interface
Improvement of the bond through a matt surfaceImprovement of the bond through a matt surface
Composite beam conceptComposite beam concept
11
Why the polished stem became matt ?Why the polished stem became matt ?
Manufacturer request to facilitate productionManufacturer request to facilitate production
22
Matt stem (CMK3)Vecteur Orthopédique
Polished stem (MKIII)Stryker Howmedica
Ra = 3m Ra = 0.4m
Ovalcross-section
Quadrangularcross-section
Stem Radiological loosening
Polished stems: 1 hip (revised)
related to PE socket wear
Matt stems:16 hips (9 revised)
3 related to PE socket
13 debonding at the bone cement interface
associated to femoral osteolysis
Matte stems loosening (CMK3)
1y 3y 5y
Matte stems loosening (CMK3)
0
20
40
60
80
100
0 2 4 6 8 10 12 14
Follow-up (Years)
% n
ot lo
osen
ed Polished stems
Matte stems
Femoral stems survival with radiologic loosening as the end-point
97.3%97.3%
78.9%78.9%
Log-rank test, p < 0.001
Significant lower survival for matt stems
Similar observations made with other stems designs:
- Exeter stem: Howie et al., JBJS Br, 1998
40 matt VS 40 polished stems, Minimum 9 year-FU
4 matt stems loosened, 0 polished stem
- Iowa Stem: Collis et al., JBJS Am, 2002
122 grit-blasted VS 122 polished stems, mean 5,8
year-FU
6 gritt-blasted stems loosened, 0 polished stem
DISCUSSION
Surface finish change Surface finish change
cross section change ?cross section change ?
What was our main mistakeWhat was our main mistake
VSVS
do not forget Micromotiondo not forget Micromotion
Fact:- Bone, cement and stem form a composite
- All mentioned materials have different E-ModuliCortex: 12 - 18 GpaPMMA: 1.8 GpaWHN Stainless Steel 250 Gpa
- As all material deform differently As all material deform differently under loadunder load
micromotion, settled by the stem, micromotion, settled by the stem, occursoccurs
SO ……… SO ………
With a Matt surface – No relative movement between stem and cement
possible
– Micromotions result in localy debonded areas at the bone cement interface which create an abrasive medium that induce osteolisys
Bon
e
PM
MA
Ste
m
While a polished surface (associated with a While a polished surface (associated with a good design)good design)
micro movements occurs at the stem-cement viscoelastic micro movements occurs at the stem-cement viscoelastic interface and the bone-cement interface is protectedinterface and the bone-cement interface is protected
Bon
e
PM
MA
Ste
m
- An increased cement-
prosthesis bond
- increases shear stresses at the
cement-bone interface
- and finally induces loosening
at the bone-cement interface
We conclude that
Round or Rectangular cross Round or Rectangular cross section ?section ?
Fact : Fact : Stems are prone to relative rotation Stems are prone to relative rotation when torque forces are appliedwhen torque forces are applied
Round vs Rectangular : peak stressesRound vs Rectangular : peak stresses
Long term results : elderly patientsLong term results : elderly patients
Charnley Kerboull stem aseptic femoral loosening200hips mean age 65 years old
Charnley Kerboull Charnley Kerboull stemstem aseptic femoral looseningaseptic femoral loosening200200hips mean hips mean age 65 age 65 years oldyears old
70%70%
80%80%
90%90%
100%100%
00 55 1010 1515 2020
98%98%
CharnleyCharnley rate : 74%rate : 74%
polishpolish
RCO, 1995RCO, 1995
Long term results : patients < 40 years oldLong term results : patients < 40 years old
European Journal of Orthopaedic Surgery and TraumatologyEuropean Journal of Orthopaedic Surgery and Traumatology1996, 6, 241-2461996, 6, 241-246
Long term results : Long term results : CDHCDH
Journal of ArthroplastyJournal of Arthroplasty2001, 16, N°82001, 16, N°8
Charnley vs CMKCharnley vs CMK
30 Y14 Y
Longterm featuresLongterm features
No cement under the tip
Dysplastic stems and acetabular Dysplastic stems and acetabular reconstructionreconstruction
20 years
Results of the next generations of CMKResults of the next generations of CMK
Long term results in patients under 50Long term results in patients under 50CORR, 418, Jan 2004CORR, 418, Jan 2004riesries
• 287 THR performed from 1975 to 1990287 THR performed from 1975 to 1990• Randomly sorted from a cohort of 2804 patientsRandomly sorted from a cohort of 2804 patients• Senior and junior surgeonsSenior and junior surgeons• 222 patients, 144 females and 78 males222 patients, 144 females and 78 males• MeanMean age : 40,1 y ( ± 8 y ; 15,5 - 50 y). age : 40,1 y ( ± 8 y ; 15,5 - 50 y).• Mean weight : 63 kg (Mean weight : 63 kg (± 18,2 kg ; 37 – 116 kg) ± 18,2 kg ; 37 – 116 kg)
0
20
40
60
80
100
120
StatusStatus Mean follow-up Mean follow-up (years)(years)