Metal ion levels in patients with a lumbar metal-on-metal total disc replacement

Abstract

The purpose of this study was to evaluate whether concerns about the release of metal ions in metal-on-metal total hip replacements (THR) should be extended to patients with metal-bearing total disc replacements (TDR). Cobalt and chromium levels in whole blood and serum were measured in ten patients with a single-level TDR after a mean follow-up of 34.5 months (13 to 61) using inductively-coupled plasma mass spectrometry. These metal ion levels were compared with pre-operative control levels in 81 patients and with metal ion levels 12 months after metal-on-metal THR (n = 21) and resurfacing hip replacement (n = 36). Flexion-extension radiographs were used to verify movement of the TDR. Cobalt levels in whole blood and serum were significantly lower in the TDR group than in either the THR (p = 0.007) or the resurfacing group (p < 0.001). Both chromium levels were also significantly lower after TDR versus hip resurfacing (p < 0.001), whereas compared with THR this difference was only significant for serum levels (p = 0.008). All metal ion levels in the THR and resurfacing groups were significantly higher than in the control group (p < 0.001). In the TDR group only cobalt in whole blood appeared to be significantly higher (p < 0.001). The median range of movement of the TDR was 15.5° (10° to 22°). These results suggest that there is minimal cause for concern about high metal ion concentrations after TDR, as the levels appear to be only moderately elevated. However, spinal surgeons using a metal-on-metal TDR should still be aware of concerns expressed in the hip replacement literature about toxicity from elevated metal ion levels, and inform their patients appropriately.

Metal Ion Concentrations in Body Fluids after Implantation of Hip Replacements with Metal-on-Metal Bearing – Systematic Review of Clinical and Epidemiological Studies

“…One important result of our systematic review is that the maximum serum Co-levels were consistently higher at all postoperative assessments in patients who received MoM LH-THA [13], [48], [49], [51], [52], [53], [54], [55] and HRA [6], [7], [13], [45], [46], [47], [48], [49], [50], [53], [55], [56], [57], [58], [59], [60] compared to patients who received MoM SH-THA [45], [46], [50], [52], [56], [59], [60], [61], [62], [63], [64], [65], [66], [67] (Table 8). …”

Prospective study on serum metal levels in patients with metal-on-metal lumbar disc arthroplasty

“…Bisseling et al [33] reported lower serum metal levels for a retrospective study of ten patients with a single-level LDA at one postoperative time point averaging 34.5 months (13-61 months). Both Zeh et al and Bisseling et al reported on the same device studied in the present series with either one or two time periods postoperatively, unlike the present series in which each patient was studied preoperatively and followed longitudinally with serial metal ion levels obtained at 3, 6, 12, 24, and 36 months postoperatively.…”

Wear in metal-on-metal total disc arthroplasty

“…As it is a fairly new technology, there is no joint registry for it and there are very few published clinical studies and retrieval studies on metal-on-metal disc arthroplasty. A few studies have raised the possibility of issues with metal wear debris from disc arthroplasty, [30][31][32] but it is too early to determine whether the problems may be of the scale seen with some designs of metal-on-metal hip arthroplasty. 33,34 Conclusion Wear of a metal-on-metal model TDA, with a ball radius of 10 mm and radial clearance between ball and socket of 0.015 mm, occurred in two stages.…”