Tapering Our Focus to the Causes and Correction of Metallosis in Primary Total Hip Arthroplasty: Commentary on an article by Brett R. Levine, MD, MS, et al.: “Ten-Year Outcome of Serum Metal Ion Levels After Primary Total Hip Arthroplasty. A Concise...

第一作者：Kevin L. Garvin

2013-04-09 点击量：671 　　我要说

Tapering Our Focus to the Causes and Correction of Metallosis in Primary Total Hip Arthroplasty: Commentary on an article by Brett R. Levine, MD, MS, et al.: “Ten-Year Outcome of Serum Metal Ion Levels After Primary Total Hip Arthroplasty. A Concise Follow-up of a Previous Report”

Serum metal ion levels associated with primary total hip arthroplasty is a topic of appreciable interest and concern to orthopaedic surgeons. Metal ion levels are elevated in virtually all patients with a total hip implant, but the significance of the elevated metal ions is unclear. Additionally, high serum concentrations of metal ions do not directly correlate with an adverse local tissue response or other adverse response by the host. Patients evaluated in the current investigation had elevated metal ion levels, which the authors believe, and most researchers concur, are primarily associated with corrosion at the femoral head-neck junction. The same group of investigators has recently reported on adverse local tissue response after total hip arthroplasty as a result of metallosis originating from corrosion at the femoral head-neck junction in ten patients who had a metal-on-polyethylene articulation. The serum cobalt levels were particularly high in this group of patients and were significantly higher than those seen in the asymptomatic group. These adverse local tissue reactions can occur, but the frequency of this problem is exceptionally low; in this series, the ten patients represented only 1.8% of all of the revisions at the authors’ institution, which is a high-volume revision practice that is well attuned to the diagnoses.

The strengths of the current investigation are numerous, including the length of follow-up of a relatively large number of patients evaluated prospectively by means of measurement of serum cobalt, chromium, and titanium levels throughout the ten years in which the patients were studied. It is interesting to note that the cobalt and chromium levels rose steadily until peaking at the seventh or eighth year after surgery, whereas the titanium levels rose rapidly and peaked at year three before steadily declining. The length of time from surgery until the cobalt and chromium levels peaked correlated with the timing for revision hip surgery, as nine of the ten hips were revised before year seven and the last one (8.9 years) was revised just after that time period. The manuscript also raises several important questions that are directly relevant to metallosis. Is there a consequence to chronic elevated metal ions in the serum of patients with total hip implants? Can a taper or trunnion and femoral head be engineered to lessen or even eliminate corrosion and subsequent metallosis? Finally, what unique individual patient circumstances or presumed immunologic responses result in the adverse tissue reaction of some but not other patients and can we positively alter the host response?

The investigation has few weaknesses, but critics may raise concern about the number of patients followed. Of the seventy-five patients, metal ion levels were available for only forty patients (53%). The patients were not lost to follow-up but could not be included in the follow-up because of other factors clearly delineated by the authors. Additional limitations of the study are the number of patients who consented to the investigation and the few variables in the stem and taper design. It is possible that other stem and taper designs may yield either higher or lower serum concentrations of metal ions.

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