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DOS Kongressen 2017 ·
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POLYETHYLENE WEAR OF A DUAL-MOBILITY ARTICU-
LATION IN TOTAL TRAPEZIOMETACARPAL ARTHRO-
PLASTY
Maiken Stilling, Lene Dremstrup, Lone Kirkeby, Torben Bæk Hansen
Department of Orthopaedics, University Clinic for Hand, Hip and Knee Surgery,
Holstebro;
Background:
Dual-mobility (DM) articulation provides good stability in tra-
peziometacarpal (TMC) arthroplasty but the thin polyethylene (PE) liner raises
concern about possible wear issues.
Purpose / Aim of Study:
To evaluate cup fixation and PE wear of a press-fit
conical DM cup.
Materials and Methods:
A case-study of the first 111 consecutive patients
(111 hands, 89 females) with Eaton stage 2-4 osteoarthritis (June 2013-May
2015). Moovis Elektra 9mm conical press-fit cup with UHMWPE DM liner and
5mm CoCr metacarpal head was used. Model-based radiostereometry (RSA)
was used to measure cup fixation and PE wear. Cup subsidence was evaluated
in the length axis of the cup. Polyethylene wear was measured as head/neck
migration with respect to cup model feature points. Double RSA examinations
were obtained for precision (95% agreement limits). RSA and PROMs were
evaluated at baseline, 3 months, 1 and 2 years.
Findings / Results:
Patients were mean 58 years (range 42-76). Precision
was 0.15 mm. Cup subsidence was 0.02 mm (SD 0.35) at 2 years. Total cup
translation (TT) at 2 years was mean 0.46 (SD 0.48) mm, and increased from
3 months to 2 years (p=0.01). At 2 years 13 cups (15%) had migrated more
than 1mm TT (p=0.00), but no cups were revised. 3 trapeziums fractured intra-
operatively and 2 patients had intraprosthetic dislocation of the dual-mobility
liner. Clinical function improved (p=0.000) by VAS_rest 3 (SD 3), VAS_activ-
ity 5 (SD3), and qDASH 31 (SD 20). Bedding-in of the PE liner was 0.15mm
(SD 0.16) until 3 months (p=0.001). PE wear was 0.06mm (0.17mm) from
3 months until 2 years (p=0.002), and 0.003mm (SD 0.13) between 1 and 2
years.
Conclusions:
At 2 years followup Moovis Elektra cup fixation was acceptable
for most implants (85%) and clinical improvements significant. There was bed-
ding-in of the PE liner until 3 months, but after 1 year PE wear was small.
No conflicts of interest reported
79.