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Study finds second generation metal-on-metal hip implants associated with adverse reactions
Two-thirds of cementless metal-on-metal total hip arthroplasty prostheses in cases with reoperation were positioned outside the safe zone.
Second-generation cementless metal-on-metal total hip arthroplasty prostheses showed signs of wear and some patients had adverse reaction to metal debris up to 15 years of follow-up, according to a study from Japanese investigators.
“The second-generation metal-on-metal (MoM) cementless total hip arthroplasty (THA) encountered adverse reactions to metal debris in two hips,” Keiji Haraguchi, MD, of Osaka General Medical Center, in Osaka, Japan, said at the EFORT Congress.
“The survival rate at 15 years was 94.9% with an endpoint of revision for aseptic loosening and 71.2% for reoperation [as the endpoint]. Prosthetic impingement caused by improper cup orientation was the critical factor for the longevity of the second-generation metal-on-metal total hip arthroplasty with a 28-mm head,” he said.
Metasul implants studied
Researchers retrospectively reviewed outcomes with the cementless Metasul (Zimmer; Warsaw, Ind., USA) MoM THA prosthesis in 87 patients operated on between 1997 and 2002. The surgeons did the surgeries with either the APR cup (Zimmer) or the Converge cup (Centerpulse; Austin, Texas, USA) and used 28-mm bearings in every patient, according to Haraguchi.
Images: Haraguchi K
There were 9 men and 42 women with an average age of 60 years in the follow-up study. Patients were followed up for 12.3 years, average. The latest follow-up occurred at 15 years in some patients.
Thirteen different surgeons performed the implantations using a posterolateral approach.
Survival rates and outcomes
Haraguchi and colleagues performed the Kaplan-Meier survivorship analysis using two primary endpoints: reoperation alone or revision for aseptic loosening (ASL). They found implant survivorship of 71.2% when the endpoint was reoperation. Survivorship was 94.9% with revision for ASL as the endpoint, according to Haraguchi. The researchers reported 67% of implants in revision cases were outside the safe zone.
Intraoperatively, 12 patients’ hips showed signs of stem neck notch formation, which meant that prosthetic impingement had occurred. Two patients developed adverse reactions to metal debris and all of those patients also had neck impingement.
The average Merle D’Aubigné and Postel hip scores improved from 8.5 points preoperatively to 16.3 points at the latest follow-up.
Two loose cups and seven cases of osteolysis were among the reasons for revision, other than ASL. Surgeons revised one of the loose cups and three of the hips that were diagnosed with osteolysis, based on the results.
“All other acetabular and femoral components were well-fixed at the latest follow-up,” Haraguchi said.
When investigators radiographically evaluated cup alignment, they found average inclination of 45.6° and average anteversion of 18.7°. They analyzed the reasons for reoperation by cup type and found for the APR cups it was due to liner dissociation from poor liner locking mechanisms. In the Converge cups, the reason for reoperation was due to pseudotumor formation and pain.
The number of surgeons who performed these THAs during the study’s 6-year period was a limitation, according to Haraguchi. Furthermore, “The target for cup orientation could not be controlled,” he said.
“There is little benefit for continued use of metal-on-metal bearings in total hip arthroplasty,” Haraguchi said. – by Renee Blisard Buddle
- Reference:
- Haraguchi K. Paper #13-3930. Presented at: EFORT Congress. June 5-8, 2013; Istanbul.
- For more information:
- Keiji Haraguchi, MD, can be reached at Osaka General Medical Center, Orthopaedic Surgery, 3-1-56 Bandai-Higashi Sumiyoshi-ku, 558-8558, Osaka, Japan; email: k-haraguchi@gh.opho.jp.
Disclosure: Haraguchi has no relevant financial disclosures.