[Value and limits of determining serum cobalt levels in patients with metal on metal articulating prostheses].
OBJECTIVE
The purpose of this study was to measure the serum cobalt levels and their correlation with clinical and radiological findings in patients with metal on metal hip articulating surfaces.


METHODS
Forty-one patients with metal on metal hip arthroplasty were reviewed retrospectively at mean follow-up of 12.9 months. Serum cobalt levels were determined for each patient by atomic absorption spectrometry at the maximal follow-up and were compared to a control group (19 patients). Two patients and one control subjects also performed exercise on a treadmill in order to appreciate the influence of physical activity on serum cobalt levels.


RESULTS
The metal on metal group presented higher serum cobalt levels than those of the control group (p < 0.0001). There was no correlation between serum cobalt and clinical and radiological findings at the exception of patient age (n = 40, r = 0.37). However, when the follow-up was greater than 18 months, mean serum cobalt was significantly higher compared to a follow-up less than 18 months. The physical exercise test led to a moderate elevation (around 10 p. 100) of cobalt in the two patients but not in the control subject.


CONCLUSIONS
The interpretation of an elevated cobalt serum level is difficult. Cobalt-containing drugs, other implants, excess of activity and diseases (renal failure) may influence serum cobalt level. In this study, the high serum cobalt levels seem not linked to a failure of the implant, mainly because of the short follow-up. They could rather be attributed to an increase of the patient activity beginning 18 months after the surgery. Because potential long-term cobalt toxicity and carcinogenicity is not well known, careful medical follow-up should be emphasized specially in young patients.
Gleizes
V
V
Service de Chirurgie Orthopédique, Traumatologique et Réparatrice de l'Appareil Locomoteur, CHU Pitié-Salpétrière, Université Paris VI.
Poupon
J
J
Lazennec
J Y
JY
Chamberlin
B
B
Saillant
G
G
D000328:Adult; D000367:Age Factors; D000368:Aged; D015982:Bias; D016022:Case-Control Studies; D002858:Chromium Alloys / Q000009:adverse effects*; D003035:Cobalt / Q000097:blood*; D015986:Confounding Factors, Epidemiologic; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure; D015203:Reproducibility of Results; D013054:Spectrophotometry, Atomic
D002858:Chromium Alloys; D003035:Cobalt
Intérêt et limite du dosage du cobalt sérique chez les patients porteurs d'une prothèse à couple métal-métal.