Ingen bildrubrik

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7 YEARS EXPERIENCES WITH HIGHLY CROSS-LINKED PE
Two Randomized studies using radiostereometry
Johan Kärrholm, Georgios Digas, Peter
Herberts, Per-Erik Johansson, Jonas Thanner
Department of Orthopaedics, Sahlgrenska
Hospital, Gotheburg University, SE-431 80
Mölndal, Sweden. Division of Orthopaedics,
General Hospital of Xanthi Greece
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highly cross-linked polyethylene

• - First trial dates back to the 70-ties
• In general practice since for about 10 years
• Low wear rates up to 5-7 years

Oonishi and Kadoya 2000
Bragdon et al 2007, Digas et al 2003, 2004,
2007 Dorr et al 2007 Engh et al 2006 Röhrl et al
2007.
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Present studies - both randomized
control or study
dec. 1998 cemented cup, unilateral operation
oct. 2000 polyliners in uncemented cups,
bilateral operation
control study

• highly cross-linked vs. standard irradiated
  polyethylene

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control or study
Cemented study

• 30 male, 30 female 61 hips
• 55 years (median, range35-70)
• 49 primary arthrosis
• 12 sec. Arthrosis (non inflammatory)

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Cups made of compression molded GUR 1050
DURASULTM highly crosslinked PE - study group

• - Heated (1250) in air
• - Irradiated at 1250C - absorbed dose 9,5 Mrad
• - Melt - annealed at 1500
• - EtO sterilized

Muratoglu and Harris ORS 1999
SULENETM - control group
- Gamma irradiated 2,5-4,0 Mrad
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Study design
Randomized trial Cemented arthroplasty

• Weber cup (Sulzer)
• Spectron stem (Smith Nephew)
• cobalt-chromium head (Ø 28 mm)

Ra 2.8mm


Ra 0.7mm
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Methods
Radiostereometry (RSA) Bone mineral density
(DEXA) Conventional radiography Harris Hip
Score Activity rating
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Radiostereometry
Supine Postop, 3, 6 months, 1, 2, 3, 5, 7
years Standing 3, 6 months, 1, 2, 3, 5, 7 years
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Cemented study at 7 years
57 attended 1 revised at 5.5 (and one at 8 yrs)
(loose stems) 1 declined (not revised) 2
deceased with implants in situ
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Cemented study
RSA results up to 7 years head penetration
proximal
3D
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Cemented study
Proximal penetration up to 7 yrs (mean, SE 7 yrs
plt0.0001)
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3-5 5-7
p lt 0.001
p 0.008
5-7 years wear in both groups but sign.
difference 3 - 5 yrs vs. 5 - 7 yrs only in
control group (0.04 vs 0.5) (Wilcoxon
signed rank test)
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Cemented study
Proximal penetration 3 m. - 7 yrs (mean SE 7
yrs plt0,001)
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p lt 0.001
p 0.3
increase of wear only in control group 5 - 7
years (Wilcoxon signed rank test)
- but 10 missing observations.
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Cemented study
Total (3D) penetration up to 7 yrs (mean SE 7
yrs plt0.0001)
p lt 0.0001
p 0.011
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2 revisions
Revised at 5.5 yrs Revised at 8 yrs (stem and
cup) (stem)
RSA data
Prox wear 0.09 mm (Durasul) 0,02
mm (Durasul) Prox cup mig. 0.34 mm
-0.05 mm Stem subsidence 6.6 mm
4.4 mm
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Cemented study
Proximal-Distal migration mean SE, 7 yrs p0,8
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Cemented study
Harris hip score1
Mann-Whitney test pgt0.1
difference preop - 7 yrs
total 7 yrs
95
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Durasul
63-100
22-77
97
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Control
61-100
12-81
1median values
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Hybrid study
control
study side side

• 32 patients, 64 hips
• 20 female, 12 male
• median age 48 years (29 - 70)
• median weight 75 kg (51 - 97)
• 17 bilat prim. OA, 15 bilat sec. OA

patients
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Liners made of GUR 1050
LONGEVITYTM highly crosslinked PE

• electron beam irradiation - 10 MRad at room
• temperature
• melt-annealed at 150º
• gas plasma sterilized

CONTROLS
- Gamma irradiated at 2,5 Mrad in inert
atmosphere
differs from Durasul
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STUDY DESIGN
Hybrid arthroplasty

• Trilogy cup (Zimmer)
• Spectron stem (Smith Nephew)
• 28 mm cobalt-chromium head

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STUDY DESIGN

• bilateral one - stage procedure
• most painful side - randomized
• least painful side - different polyethylene

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METHODS
radiostereometry (RSA) radiography
bone mineral density (DEXA)
Harris hip score, MACTAR, SF 36



activity rating

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Radiostereometry
Supine Postop, 3, 6 months, 1, 2, 3, 5, 7
years Standing 3, 6 months, 1, 2, 3, 5, 7 years
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Hybrid study at 7 years

• 26 attended (52 hips)
• 3 delayed (not revised)
• 2 declined (not revised)
• deceased with implants in situ

25 /20 (supine/standing) cases with bilat.
successful RSA
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Hybrid study
RSA results head penetration
proximal
3D
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Hybrid study
Proximal penetration mean SE 7 yrs plt0.00001
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3-5 5-7
p lt 0.00004
p 0.002
5-7 years wear in both groups but sign.
difference 3 - 5 yrs vs. 5 - 7 yrs only in
control group (0.005 vs 0.5) (Wilcoxon
signed rank test)
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Hybrid study
Total (3D) penetration Mean SE 7 yrs plt0.00001
p lt 0.0001
p 0.06
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Hybrid study
Proximal penetration mean SE 7 yrs plt0.00003
p 0.03
p 0.8
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RESULTS - RSA Cup migration
supine examinations
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Hybrid study
Proximal cup migration mean SE 7 yrs p0.3
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Hip Score and pain scores 7 yrs and 0 to 7 yrs.,
median, range
Hip Score 100 88-100 diff 0 7 yrs 57 31 - 83
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Conclusions after 7 years

• highly x-linked reduced head penetration
• with 55-80
• there was no consistent influence on cup
• migration

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Conclusion
Lossening of a cemented rough stem had no
measureable effect on wear (2 cases) of highly
x-linked cemented cups
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Conclusion

• this quality of highly cross-linked poly
• not resistant to wear/creep
• past 3 years - no certain evidence for
• accelerated wear/creep

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CONCLUSION

• The crosslinked materials studied
• has hitherto worked well.
• They should be
• continuously studied for another decade
• used as judiciously as we learnt from
• previous experiences with polyethylene.

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• Thank You

• thank you!