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Speaker: Large metal-on-metal bearings counterweighed by associated risks

Issue: Issue 6 2011

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Ajay Malviya

DUBLIN — Research in the increased metal ions found in patients with large metal-on-metal bearings with cemented stems for primary total hip replacement continues to evolve, according a presentation at the British Orthopaedic Association and the Irish Orthopaedic Association Combined Meeting 2011, here.

“The benefits of large metal-on-metal replacement are evident regarding satisfaction and dislocation, but they are counterwighed by the associated risks of adverse reactions to metal debris,” Ajay Malviya, MD, said.

Malviya and his team conducted a randomized controlled trial of 100 patients to compare cemented stem behavior with a large head metal-on-metal bearing versus 28-mm metal-on-polyethylene bearings. Fifty patients with an average age of 64 years and BMI of 29.04 were randomized to each arm of the study. Outcome measures included Harris Hip Scores, WOMAC, SF-36, Hip Dysfunction and Osteoarthritis Outcome Score, patient satisfaction preoperatively, and postoperatively at 3, 12 and 24 months. Whole blood metal ion levels were assessed at 1 year.

Malviya reported that there was no difference in femoral stem subsidence, Harris Hip Scores, WOMAC and SF-6 scores between the groups at 2 years. Two revisions were perfromed both groups – both for dislocation in the metal-on-polyethylene group and for a pseudotumor and periprosthetic fracture in the metal-on-metal group.

He said the metal-on-metal group reported higher patient satisfaction. However, the metal-on-metal group had a 20% higher and the metal-on-polyethylene group showed a 3.4% higher metal ion level above the Medicines and Healthcare Products Regulatory Agency action level of 7 µg/L.

Reference:

• Ramaskandhan J, Malviya A, Bowman R, et al. Randomised controlled trial of primary total hip replacement comparing cemented stem beahvior between large metal on metal and conventional metal on polyethylene bearing surfaces. Paper #1. Presented at the British Orthopaedic Association and the Irish Orthopaedic Association Combined Meeting 2011. Sept. 13-16. Dublin.

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