Sunday, August 21, 2011

Early markers of nephrotoxicity in patients with metal-on-metal hip arthroplasty.

I am returning  to the medical literature which has been published in the last 2 months as the focus of this blog has been on other issues in the past 8 weeks or so.  This week I will review the new medical literature that has surfaced around the hip replacement.

Just as a reminder/ Metal on metal hips should not be placed in patients with compromised Kidney function....Recall in prior posts, I asked the question:  What does compromised/impaired Kidney function mean?  Does it mean low creatinine levels?  Does it mean one Kidney?   Both? 

This article is relates to the testing involved in identifying  systemic issues  the metal ions may have on the kidney, a topic I have discussed in previous posts.

Metal ions are cleared in the kidney which is why this is a topic of discussion.

Clin Orthop Relat Res. 2011 Jun;469(6):1651-9.

Corradi M, Daniel J, Ziaee H, Alinovi R, Mutti A, McMinn DJ.

Source

Nephrology and Health Sciences, University of Parma, Parma, Italy.

Abstract

BACKGROUND:

Metal ions released from arthroplasty devices are largely cleared in urine, leading to high exposure in renal tissues. Validated early markers of renal damage are routinely used to monitor workers in heavy metal industries, and renal risk can be quantified in these industries. It is unclear if the ion levels in patients with metal-on-metal hips are sufficient to cause renal damage.

QUESTION:

Does metal-on-metal (MOM) bearing use over a 10-year period lead to elevation of early renal markers compared with the levels expected in subjects with no metal exposure?

METHODS:

We retrospectively reviewed 31 patients who underwent MOM hip resurfacings 10 years earlier. Whole blood specimens were collected for metal ion analysis, serum for creatinine estimation, and urine for timed metal ion output and renal markers. The renal marker levels of 30 age- and gender-matched subjects with no metal exposure and no known renal problems or diabetes mellitus were used as controls for renal markers.

RESULTS:

Median serum creatinine level in the MOM group was 1.1 mg/dL (interquartile range, 1.0-1.2 mg/dL) and median creatinine clearance was 79.2 mL/min. In this cohort, the number of patients with markers of renal damage above the reference range was comparable to the controls. None of the renal markers were associated with metal levels.

CONCLUSION:

The absence of elevation of renal markers in this cohort 10 years after MOM bearing implantation is reassuring. However, we believe surveillance through further longer-term, large-scale controlled trials are needed to monitor this arthroplasty-induced low-intensity (but long-term) trace element exposure to rule out potential nephrotoxicity.

[ I totally agree with their conclusion in light of the Stanford study that was published back in April of this year.  Recall the April 11th post on the study by the Stanford researchers?]  Here is that summary:

Department of Orthopedic Surgery, Stanford University, Stanford, California.

Abstract


Metal-metal total hip arthroplasty (THA) is contraindicated in patients with impaired renal function due to increased metal ion output relative to other bearings and renal excretion of metal ions. Although one can avoid a metal-metal THA in a patient with renal disease, a patient may be destined to develop renal disease later in life. In this study, we sought to determine the incidence of newly diagnosed renal disease in the 9 years after THA. Using the Department of Veterans Affairs national database, we identified 1709 patients who had a primary THA in 2000 without preexisting renal disease. We found the 9-year risk of developing chronic renal disease after primary THA to be 14% and severe or end-stage renal disease to be 6%.

[my comments.  What I like about the Parma Italy study above is that they are seeking early signs of systemic issues assocaited with hip replacement.  There are not a lot of medical people out there really looking at the early testing for any systemic issues.  Ditto for the carcingogenic issues.  If you want tests done, you have to advocate for yourself.  It is highly doubtful that an orthopedic surgeon is going to initiate such such tests to look at early  systemic effects of the hip.  Yes, they will order tests to determine the  metal levels and the infection levels but that is about the extent of the testing.  There is not a lot published on this topic which is why I spend so much time on it.

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