title: Metal ion levels in patients with a lumbar metal-on-metal total disc replacement: should we be concerned?
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.
authors.affiliation: Department of Orthopaedics, Rijnstate Hospital, Postbox 9555, 6800 TA Arnhem, The Netherlands.
authors.forename: P
authors.initials: P
authors.lastname: Bisseling
authors.forename: D J
authors.initials: DJ
authors.lastname: Zeilstra
authors.forename: A M
authors.initials: AM
authors.lastname: Hol
authors.forename: J L C
authors.initials: JL
authors.lastname: van Susante
mesh_terms: D000328:Adult; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects; D002857:Chromium / Q000097:blood*; D003035:Cobalt / Q000097:blood*; D017586:Diskectomy; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007403:Intervertebral Disc / Q000601:surgery*; D055959:Intervertebral Disc Degeneration / Q000601:surgery*; D007595:Joint Prosthesis; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D019736:Prostheses and Implants; D019919:Prosthesis Implantation / Q000009:adverse effects; D016059:Range of Motion, Articular; D055815:Young Adult
chemical_list: D002857:Chromium; D003035:Cobalt