Charnley-Kerboull Total Hip Replacement
Long Term Results
In Patients Younger Than 50
Results of a 30 years experience
L Kerboull, M Hamadouche, M Kerboull.
Long term results in patients under 50
• Reliability of THR outcome in young people is still being
debated
• The cemented metal/PE Kerboull system is now old and
someone could think that it is no more indicated for
young patients in the third millenium ?
• Results published in CORR Jan 2004
The series
•
•
•
•
•
•
287 THR performed from 1975 to 1990
Randomly sorted from a cohort of 2804 patients
Senior and junior surgeons
222 patients, 144 females and 78 males
Mean age : 40,1 y ( ± 8 y ; 15,5 - 50 y).
Mean weight : 63 kg (± 18,2 kg ; 37 – 116 kg)
180
300
160
140
250
120
200
100
80
60
40
115
172
20
150
100
50
0
Actif
Inactif
0
ASA 1
ASA 2
ASA 3
ASA 4
The series : preoperative diagnosis
120
100
80
60
40
20
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ip
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Previous surgery : 123 hips
Operative Technique
• Transtrochanteric approach
• Charnley-Kerboull standard implants
• Cup all poly
• CMW type 1, mixed in air
• Distal plug
• Acetabular reconstruction in 92 hips
Operative Technique : femoral implant
Implants Surface
design
Section
Neck Hips
diamete
r (mm)
MK I
Polished Quadrangular
13
139
CMK 2
Matt
Oval
13
51
MK III
Polished Quadrangular
10
27
CMK 3
Matt
10
70
Oval
Polished
166
Matt
121
Methods
• Merle d’Aubigné and Postel clinical
scoring system
• Cup : Charnley and Delee classification
• Stem : Gruen and Amstutz classification
•
•
•
•
Linear Wear : Chevrot and Kerboull M
Cystic osteolysis
Heterotopic ossifications
Statistical analysis
Methods : Modified Harris classification for
radiological loosening
Socket
Femoral Stem
Definite
loosening
Migration ≥ 3 mm and/or
3°
Complete radiolucent line
≥ 2 mm
Probable
loosening
Complete radiolucent line
< 2 mm
Subsidence ≥ 3 mm
Cement mantle fracture
Complete radiolucent line
≥ 2 mm
Radiolucent line in Zone I
≥ 2 mm
Complete radiolucent line
< 2 mm
Potential
loosening
Radiolucent line in 2
zones
Radiolucent line in 2
zones
Type
of
Loosening
Mean follow-up : 14,5 years
(± 5.1, 6m to 25 y)
Status
Mean follow-up
(years)
Number of hips
Reviewed
16,1 ± 4,6
210 ( 73,2%)
Died of
5,4 ± 3,1
unrelated causes
10 (3,5%)
Lost to follow-up 10,8 ± 5,1
42 (14,6%)
Revised
12,6 ± 6,1
25 (8,7%)
52 hips had a follow-up greater than 20 years
Complications
3 non unions of the trochanter 1%, 1 reoperated
2 Deep infections, 1 acute treated by articular debridment and
1 chronic revised.
3 dislocations, 1 revised 1%
1 hematoma reoperated
3 heterotopic ossification grade 4, 1 reoperated
3 palsies of the peroneal nerve
Clinical results : PMA score
postop
preop
60
250
50
200
40
150
30
100
20
10
50
0
0
0 2 4 6 8 10 12 14 16 18 20
Mean : 9,6
0 2 4 6 8 10 12 14 16 18 20
Mean : 17,4
83% of the hips rated excellent to very good
Radiological results : Cup loosening
No
loosening
Definite or Potential
probable loosening
loosening
Wear > 0,1 mm/y
Number of 238
hips
82,9%
15
5,2%
24
8,4%
Radiological results : cup wear
Mean femoral head penetration : 1,3 mm ± 1,5 mm (0 – 8 mm)
0,1mm/y
196 hips
91 hips
0.02 mm/y versus 0.28 mm/y
P < 0.0001
8 ans
Wear related factors
Normal versus abnormal wear
Factor
P value
Factor
P value
Age
0,7
Follow-up
0,5
Sexe ratio
0,2
Diagnosis
0,1
Activity
0,34
Cup position
0,8
Weight
0,9
Osteolysis
0,0001
Year of surgery
0,0001
Surgeon
0,5
1979 : 0,095 mm/an
1980 : 0,158 mm/an
Intrinsic properties of PE was the main related factor
These changes were due to manufacturing process variations
PE Quality is the main factor
Bilateral cases
17 y
18 y
Radiological results : Stem loosening
Number
of hips
No
loosening
Definite or Potential
probable loosening
loosening
271
95,1%
12
4,2%
4
0,7%
osteolysis
10 aseptic, 1 septic, 1 after a periprosthetic fracture
Radiological loosening : stem
Implants
design
Surface
Section
Aseptic
loosening
Hips
MK I
Polished
Quadrangular
1
139
CMK 2
Matte
Oval
2
51
MK III
Polished
Quadrangular
0
27
CMK 3
Matte
Oval
7
70
Matt vs Polished : p = 0,0001
Matt or polished surface ?
Square or rounded cross section ?
Mechanical basis
Fact:
- Bone, cement and stem form a composite
- All mentioned materials have different E-Moduli
Cortex:
PMMA:
WHN Stainless Steel
- All material deform differently under load
this leads to micro motions
12 - 18 Gpa
1.8 Gpa
250 Gpa
Why the polished stem became matt ?
•Initiation of stem loosening:
debonding of the cement to prosthesis interface
Improvement of the bond through a matt surface
But ………
With a Matt surface
Bone
– 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
While a polished surface
Bone
Allowes micro movements in the stem to cement viscoelastic
interface that protect the bone cement interface
Does a polished cimented stem always subside ?
Subsidence:
Unlike other stems the CMK is not designed to subside and does
not subside.
« The French paradox »: Langlais, Ling,
Kerboull, Sedel. JBJS Br, 2003.
Why ??
- We choose the stem which best fills the medullary canal
there is no space for the stem to subside.
- The collar decreases the distal force applied to ciment plug
- The stem does not get loose due to the cohesion forces acting
on the two polished (cement/stem) surfaces.
Round or Rectangular cross section ?
Stems are prone to relative rotation
when torque forces are applied
Rounder cross section
– Prevents hook stresses at the angle
– But Increased shear stresses at the interface
Rectangular cross section
– Might induce hook stresses
– Applies compressive stresses on the cement
Round vs Rectangular
a
M2
F1a
M1
M1
F1b
b
shear stress
compressive stress
cross section design ?
The cross section is very delicate:
Too round results in problems
Too edgy might result in problems
(increased hoop stresses)
Look for a compromise
Almost rectangular with smooth angles
What was the most deleterious change
Matt surface or rounded cross section
Ra 0.9 m (35  inch) MK 2 :
4 % at 15 Y.
Ra 1.7 m (67  inch) CMK 3 : 21 % at 10 Y.
Matt surface
Revisions : 25
Loosening or wear : 22
7 loosened stems
10 loosened cups
5 worn cups
Other : 3
1 septic
1 recurrent dislocation
1 femoral fracture
Suvival rate %
Survival rate : revision
1
,8
,6
,4
,2
0
20 years
85,4%
95% sup : 92,4 %
95% inf : 78,4 %
0
5
10
15
20
25
30
Follow-up years
Survival rate : cup loosening
age NS
Survival rate : stem loosening
age NS
Survival rate : stem loosening, surface finish
Suvival rate %
1
96,4%
88,5%
,8
,6
P= 0,0001
,4
matt
polished
,2
0
0
5
10
15
20
25
30
Follow-up years
Suvival rate %
Survival rate : wear dependant
1
Wear <= 0,1 94,8 %
,8
,6
Wear > 0,1 70,6 %
P = 0,002
,4
,2
0
0
5
10
15
20
25
30
Follow-up years
What we learnt at the end of this study
• The Kerboull cemented prosthesis could provide
satisfactory and durable results for 20 years in 85
% of patients younger than 50 years.
• So in our mind it remains a good solution,
specially for young patient when anatomic and
bony conditions are disturbed.
• PE wear, when higher than 0.1 mm/y, is the only
unsolved problem.
• PE wear is mainly influenced by PE intrinsic
qualities
• Surface of a cemented stem must be definitely
polished to protect cement and bone from
excessive stresses.
Do we need different implants for young people?
• When we change implant, we also experiment
new problems and our rate of failure increases
compared with our routine technique
• So we must change for a good reason
– Bearing surfaces : may be
– Type of fixation : definitely no , except if imposed by the
mechanical properties of the bearing surfaces
•
when using a new implant, If our operative
technique is reliable don’t change it, if possible
Conclusions
• Proven designs are not numerous
because a long time is necessary to
evaluate a hip prosthesis
• Before changing try to correct the
identified problems
• Fashion, experimental studies and
marketing features are not always our
best friends !
Thank you