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Wear debris from taper junctions linked with adverse reactions in metal-on-metal hips
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Large diameter bearing metal-on-metal total hip arthroplasties with taper damage may lead to mechanical damage and secondary localized corrosion, causing an adverse immune response in patients, according to a study presented by David J. Langton, MRCS, at the British Orthopaedic Association and the Irish Orthopaedic Association Combined Meeting 2011.
“We have shown very high failure rates secondary to adverse reactions to metal debris in metal-on-metal total hip replacements [MoM THRs],” Langton said during his presentation. “Component size and position does not seem critical as we have previously reported with pure hip resurfacings.”
Adverse reactions
Langton and colleagues previously analyzed metal-on-metal components “from around the world,” according to the study abstract. They noticed that patients who underwent hip resurfacings experienced adverse reactions to metal debris (ARMD) due to deterioration of bearing surfaces. But, patients fitted with large diameter MoM hip replacements showed signs of ARMD in the presence of well-functioning bearing surfaces.
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The team conducted full volumetric wear analyses of bearing surfaces and taper junctions with a coordinate measuring machine, according to the study abstract. Retrieved components from 78 patients who had experienced ARMD were available to the investigators. These were a combination of hip resurfacings and large diameter THRs. The team classified large diameter MoM hip implants as having a diameter =36 mm. They characterized material composition using scanning electron microscopy.
Taper wear
The investigators found low bearing surface wear in 34 MoM total hips, according to the study abstract. The internal taper-junctions of the femoral components showed wear depths of up to 90 microns. Some showed total volumetric loss of greater than 10 mm3. Of the patients experiencing ARMD after THR, 65% exhibited metal ion levels “greater than the [Medicines and Healthcare Products Regulatory Agency] MHRA guidance figure” of 7 mg/L, according to the abstract. The researchers observed in the study that many commercial brands of devices, including cobalt chromium and titanium stems, showed taper damage that was of a consistent pattern and distribution.
Patients from whom retrieved explants were found to have severe taper damage were significantly more likely to suffer extensive tissue damage than those with failed resurfacing. The tissues of these patients who underwent THR were more likely to exhibit intense alval responses with lymphoid neogeneis and granuloma formation. The researchers warned that “wear debris from taper junctions appears to have a greater potential to stimulate adverse immune response,” according to the study abstract. – by Renee Blisard
Reference:
- Langton DJ, Ghandi J, Sidaginamale RP, et al. Failure of large diameter bearing metal-on-metal total hip arthroplasty due to taper wear. Presented at the British Orthopaedic Association and the Irish Orthopaedic Association Combined Meeting 2011. Sept. 13-19. Dublin.
- D.J. Langton, MRCS, can be reached at the Joint Replacement Unit, University Hospital of North Trees, Hardwick, Stockton-on-Tees; 01642 617617; email: djlangton22@doctors.org.uk.
- Disclosure: Langton has received payment for talks given at Depuy and Finsbury Orthopaedics conferences, received travel reimbursement from Depuy, Finsbury Orthopaedics, Smith & Nephew and Wright Medical, and is an unpaid consultant for Wright Medical.
The abstract presented by Langton et al presents an alternative failure mechanism for large diameter metal-on-metal (MoM) total hip arthroplasty (THA) other than wear at the bearing surface. This mechanism involves wear of the taper junction of the femoral stem, presumably from the increased forces transmitted to the taper/head junction from the large diameter metal articulation. This mechanism is certainly plausible if the bearing loses its fluid film lubrication after inactivity and then at start up the “dry” bearing may have increased friction and hence transmit increased torque to the taper junction. This mechanism would of course be design-dependent and may not be applicable to all large diameter MoM THA designs.
The breadth of implants tested is not clear from the abstract. It appears that in many of the hips that had an adverse local reaction to metal debris, the volumetric wear from the taper was quite small, yet the patients developed an adverse response. This raises the question as to whether the particles generated from the taper have a higher biologic activity than wear particles from the articulation or whether there is yet some other wear mechanism not yet delineated. Further research into this failure mechanism is warranted.
— Kirk Kindsfater, MD
Orthopaedic &
Spine Center of the Rockies Fort Collins, Colo.
Disclosure:
Kindsfater is a consultant to and receives research support from DePuy
Orthopedics.