Ten-Year Outcome of Serum Metal Ion Levels After Primary Total Hip Arthroplasty

Abstract

We previously reported on the metal ion concentrations of cobalt, chromium, and titanium that were found in the serum of patients three years after they had undergone primary total hip arthroplasty as compared with the concentrations found in the serum of control patients who did not have an implant. This study is a concise update on the serum metal levels found in a cohort of these patients ten years after the time of hip implantation. Of the original seventy-five subjects, metal ion levels were available for forty patients (53%). Ten patients (hybrid group) had received a hybrid total hip replacement that consisted of a modular cobalt-alloy femoral stem with a cobalt-alloy femoral head that had been inserted with cement and a titanium acetabular socket that had been inserted without cement. Nine patients (cobalt-chromium [CoCr] group) had received an implant with an extensively porous-coated modular cobalt-alloy femoral stem and femoral head along with a titanium acetabular socket; the femoral and acetabular components had each been inserted without cement. Eight patients (titanium group) had undergone insertion of a proximally porous-coated modular titanium-alloy femoral stem with a cobaltalloy femoral head and a titanium acetabular socket; the femoral and acetabular components had each been inserted without cement. Thirteen patients (control group) from the original control group of patients who had not received an implant served as control subjects. Serum metal levels were measured with use of high-resolution sector field inductively coupled plasma mass spectrometry. The hybrid total hip arthroplasty group had mean cobalt levels that were 3.2 times higher at 120 months than they were at baseline, and the cobalt levels in that group were significantly higher than those in the titanium total hip arthroplasty group at thirty-six, sixty, eighty-four, ninety-six, and 120 months (p < 0.01). The hybrid group had mean chromium levels that were 3.9 times higher at 120 months than they were at baseline, and the CoCr total hip arthroplasty group had chromium levels that were 3.6 times higher at 120 months than they were at baseline. The serum titanium levels were higher in the titanium group at all follow-up time intervals as compared with the levels in all other groups, and the level in the titanium group at 120 months was eighteen times higher than it was at baseline (p < 0.01). Patients with well-functioning primary metal-on-polyethylene total hip replacements had elevated serum metal levels for as many as ten years postoperatively. Furthermore, metal release at the modular femoral head-neck junctions, rather than passive dissolution from porous ingrowth surfaces, was likely the dominant source of serum cobalt and chromium.continued

Early Corrosion-Related Failure of the Rejuvenate Modular Total Hip Replacement

“…Therefore, metal ion levels have been used as a surrogate marker of corrosion wear at the articulating surface or modular junction 38 , which may continue to increase for years after surgery 39 . However, interpretation of serum metal ion levels is controversial, and a universal safe zone has not been established.…”

A High Prevalence of Corrosion at the Head–Neck Taper with Contemporary Zimmer Non-Cemented Femoral Hip Components

“…Although there is no agreed cut-off for Co serum ion level known to be pathological, we used a Co of 1.6 ng/mL, based on the lowest inclusion level in the description of this phenomenon in a cohort of patients after contemporary THA [1]. This is reasonable based on long-term data on well-functioning hip arthroplasties, where Co levels are less than 0.8 ng/mL at up to ten years post-operatively [3].…”

Can Metal Levels be Measured at a Community Laboratory?

“…Currently metal levels represent one data point in a complex patient-specific decision making process for the care of patients with MOM hips [1]. Recently the focus has been on the relationship between metal levels and the presence of pseudotumors or the need for reoperation [23,29,30]. However, longterm concerns about chronic exposure to elevated metal levels remain.…”

“…Patient blood samples were collected at specific follow up intervals including 1, 2, 3, and 5 years post-op. All measurements were made using Inductively Coupled Plasma Mass Spectrometry (ICPMS) which is currently recognized as the preferred method for metal level measurement [20][21][22][23]. The detection limits at this laboratory were 0.03 μg/L for cobalt and 0.01 μg/L for chromium.…”