[Reliability of porous coating metal-backed cups: advantages and adverse effect of a posterior elevated rim polyethylene liner].
OBJECTIVE
We analyzed primary implantation of the Duraloc cup associated with a self-locking Muller stem at 9.6 +/- 1.6 years (8.6-11.4). Because of its particular 3/5 semi-spherical shape, the Duraloc cup has been associated with a high rate of dislocation. The objective of this study was to evaluate the efficacy of an anti-dislocation posterior elevated rim polyethylene liner on long-term dislocation rate and wear.


METHODS
The series included 89 arthroplasties implanted between 1991 and 1993 in 82 patients, mean age 56.8 +/- 12.6 years (17.2-87). The Postel-Merle-d'Aubligné (PMA) score and subjective evaluation with a visual analog scale were used for the clinical assessment. Changes in the bone-cup interface, cup migration, and polyethylene wear were assessed radiographically.


RESULTS
At last follow-up, the PMA function score was 16.2 +/- 1.9 points (10-18) (81% good, very good and excellent results). The postoperative x-rays showed a low incidence of lucent lines and osteolysis, respectively 8% and 4%. Mean annual linear polyethylene wear was 0.11 +/- 0.066 mm (0.03-0.57) and only 4% of the cups showed wear greater than 0.2 mm/year. Wear was correlated with the presence of acetabular osteolysis and high activity level. Two cups migrated (3-4 cm medialization). Three cups were revised, one for deep infection, one for recurrent dislocation, and one for dislocation associated with major wear. The rate of dislocation was 2.2% (two cases). Overall survival was 97.3% at 9.6 years (95%CI 0.93-1.0).


CONCLUSIONS
Compared with other series in the literature using this implant, the presence of a posterior elevated rim polyethylene liner reduced the rate of instability and did not increase wear. The Duraloc cup is recognized as a reliable implant exhibiting excellent osteointegration and a low rate of migration. The presence of a posterior rim is associated with a lower rate of dislocation and does not increase wear. It can thus be proposed for primary implantation. The posterosuperior position for the liner is recommended.
Girard
J
J
Service d'Orthopédie C, Clinique d'Orthopedie Pierre Decoulx, Hôpital Roger Salengro, CHRU, 59037 Lille Cedex. j_girard_lille@yahoo.fr
Laffargue
P
P
Decoulx
J
J
Migaud
H
H
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D005500:Follow-Up Studies; D006617:Hip Dislocation / Q000209:etiology / Q000517:prevention & control*; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D020959:Polyethylene; D011474:Prosthesis Design / Q000009:adverse effects; D011475:Prosthesis Failure
D020959:Polyethylene