Ion release in patients with metal-on-metal hip bearings in total joint replacement: a comparison with metal-on-polyethylene bearings.
Polyethylene (PE) wear has been shown to be a problem in long-term joint replacement using metal-on-PE bearing. The use of metallic heads articulating with metallic cups could solve this problem: success will be enhanced if wear and corrosion of the articulating surfaces are maintained at a low level. New models with metal-on-metal bearing have been proposed, to be used mainly for young subjects: such coupling seems to have a reduced release, but it is unclear yet if the medium-term corrosion rate is really negligible or, on the contrary, it is significantly higher than in the metal-on-PE bearing. Aim of our study was the comparison of ion release in the serum of two groups of patients who had the same type of stable cementless prosthesis, but different bearing: twenty-six patients with metal-on-metal (Group A) and fifteen patients with metal-on-PE bearing (Group B) were examined. The follow-up was 14-38 months for group A and 18-34 months for group B. The serum concentration of chromium (Cr), cobalt (Co) and molybdenum (Mo) was measured. Twenty-two patients before surgery were used for comparison (Group C). The reference values were obtained from a population of twenty-two healthy subjects (Group D). Our findings indicate that metal-on-metal bearings produce a significantly higher systemic release of cobalt and chromium (ng/ml) when compared with levels found in metal-on-PE, pre-surgery and reference groups. Such a high release should induce to improve the bearing materials or, at least, to study the biologic fate of metal ions and consequently their long-term effects. In such a way a risk-to-benefit ratio for the patient could be established.
Savarino
L
L
Laboratorio di Fisiopatologia degli Impianti Ortopedici, Istituti Ortopedici Rizzoli, Bologna, Italy. lucia.savarino@ior.it
Granchi
D
D
Ciapetti
G
G
Cenni
E
E
Nardi Pantoli
A
A
Rotini
R
R
Veronesi
C A
CA
Baldini
N
N
Giunti
A
A
D000328:Adult; D000368:Aged; D019644:Arthroplasty, Replacement, Hip; D002857:Chromium / Q000097:blood; D003035:Cobalt / Q000097:blood; D003343:Corrosion; D019544:Equipment Failure Analysis; D005260:Female; D005500:Follow-Up Studies; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008422:Materials Testing; D008670:Metals / Q000097:blood*; D008875:Middle Aged; D008982:Molybdenum / Q000097:blood; D011095:Polyethylenes / Q000378:metabolism*; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013223:Statistics as Topic; D013499:Surface Properties
D008670:Metals; D011095:Polyethylenes; D002857:Chromium; D003035:Cobalt; D008982:Molybdenum