[Translated article] Evolution of chromium and cobalt serum levels after the use of a modular neck stem in primary total hip arthroplasty.

INTRODUCTION AND OBJECTIVES

Modular neck primary stems were introduced with the theoretical advantage of restoring the hip anatomy more precisely. However, the presence of a second junction has been associated with increased corrosion and release of metal debris. The objective of our study is to quantify of chromium and cobalt serum values, and to analyse their temporal evolution during five years.

MATERIAL AND METHODS

We present a prospective series of 61 patients who underwent primary total hip arthroplasty by implantation of the H MAX-M® stem (Limacorporate, San Daniele, Italy). Serum chromium and cobalt determinations were performed at six months, two years and five years.

RESULTS

Our series shows a progressive elevation in chromium levels with a significant difference between chromium values at six months (0.35±0.18) and five years (0.52±0.36), p=.01. Regarding cobalt, a statistically significant elevation is observed between six months and two years and a subsequent stabilisation of values between two and five years, with a cobalt mean at six months (1.17±0.8) significantly lower than at two (2.63±1.76) and five years (2.84±2.1), p=.001.

CONCLUSION

Elevated serum cobalt levels have been observed in patients who underwent modular neck stem implantation. The results obtained in this study have limited the use of stems with a modular neck in our clinical practice.