High metal-ion levels, persistent pain cited as indications for revision of MoM hips
Elevated metal-ion levels, loose cups either radiographically or clinically and psychological changes are among the indications orthopedic surgeons need to consider for the revision of metal-on-metal hip articulations, according to a presenter at a recent meeting.
“You do not have to worry much about the patient who has ions below 10 [parts per billion], no clinical symptoms and a good X-ray,” Lawrence D. Dorr, MD, said during his presentation. “If you have an X-ray that has evidence of radiolucent lines around the entire cup, then you have a patient who you have to worry about — with or without symptoms. They could get progressive loosening. You need to follow them at a 6-month interval.”
Dorr said elevated metal-ion levels, especially cobalt, mean increased wear so local osteolysis and bone destruction are risk factors with increased follow-up. For patients with metal-ion levels greater than 10 parts per billion (ppb) and clinical symptoms, he said surgeons need to decide whether to revise the patient’s metal-on-metal (MoM) hip.
“If you do not have the situation where they have frank clinical symptoms and they have high ions on their tests, but you have a patient with psychological changes or you have patients with symptoms of cobalt poisoning, then that is also an indication for revision,” Dorr said.
For patients younger than 75 years with metal-ion levels at 25 ppb or greater, he recommended surgeons talk with the patients to decide whether to revise. For patients older than 75 years, he said he will wait to see if patients develop any symptoms of metal problems or cobalt poisoning.
Patients with clinical symptoms, such as persistent start-up troubles or unrelenting pain with any activity, have loosening and are among those indicated for revision. In addition, soft tissue masses in the groin or anterior hip are other indications for revision of MoM articulations. Cognitive changes, such as memory loss and psychomotor retardation, also indicate revision. Dorr advised surgeons to question patients about shortness of breath, as cobalt poisoning will cause cardiac symptoms.
“The most important [cobalt poisoning symptom] that occurs most commonly is heart symptoms, so you need to question a patient if they have increased shortness of breath,” Dorr said. “If they do, they need to be seen by a cardiologist because cobalt poisoning most commonly causes the cardiac symptoms.”
According to Dorr, the most common causes MoM failures have been caused by adverse local tissue responses due to MoM debris in the hip, including aseptic lymphocyte-dominated vasculitis-associated lesions, pseudotumor and osteolysis. With the number of complications associated with MoM hips, Dorr recommends a closer look at new techniques before administering.
“It is important in the future that we think a little harder because we jump into new techniques quickly because this particular technology had us high as a 45% usage rate in the United States before all of the complications started,” Dorr said. – by Kristine Houck, MA, ELS, and Casey Tingle
Dorr LD. Paper #41. Presented at: Current Concepts in Joint Replacement Winter Meeting; Dec. 10-13, 2014; Orlando, Fla.
For more information:
Lawrence D. Dorr, MD, can be reached at the Dorr Arthritis Institute, Keck Hospital of USC, Department of Orthopedics, 1520 San Pablo St, Suite 2000, Los Angeles, CA 90033; email: firstname.lastname@example.org
Disclosure: Dorr reports no relevant financial disclosures.