Elevated metal levels may better indicate pseudotumor after MoM THA than symptoms
DALLAS — Pseudotumor formation occurred in 52% of patients who underwent metal-on-metal total hip arthroplasty performed with two different designs of prostheses and later underwent metal artifact reduction sequence MRI or MARS MRI of the hip, a presenter said at the American Association of Hip and Knee Surgeons Annual Meeting.
“So overall prevalence and severity, over half of our patients had a pseudotumor and nearly 40% either had a type 2 or type 3 lesion,” Daniel E. Goltz, BS, said.
The 207 hips that underwent MARS MRI received an ASR THA prosthesis or a Pinnacle prosthesis with Ultamet liner (both DePuy) metal-on-metal (MoM) hip implant. The patients represented just the patients who had MARS MRI and had any pseudotumors graded among 178 patients with ASR prostheses and 788 patients with Pinnacle prostheses who were operated on between 2002 and 2013 and had a minimum 2-year follow-up and average 8-year follow-up.
Goltz and colleagues analyzed the factors associated with a pseudotumor and found those patients were significantly more likely to have higher cobalt levels, a higher cobalt-chrome ratio, a high-offset femoral stem and a larger size acetabular cup.
“Patients with thick-walled cystic or solid masses were more likely to be revised than those with thin-walled cystic masses (P < .001),” the investigators wrote in the study abstract.
In his presentation, Goltz said, “Interestingly, we found that symptoms may not be the best reliable indicator of whether or not a patient has a pseudotumor or its severity.”
The study definition of being symptomatic after MoM THA was pain, weakness or a limp, he noted.
“Sixty percent of our cohort actually ended up having symptoms,” Goltz said. However, among the asymptomatic patients, 47% had a pseudotumor, he said.
“It is our hope that this work will be able to guide all of you as clinicians as you make what may come to be a challenging decision in terms of which patients to revise and the timing for that revision,” Goltz said. – by Susan M. Rapp
Kleeman L, et al. Paper #39. Presented at: American Association of Hip and Knee Surgeons Annual Meeting; Nov. 2-5, 2017; Dallas.
Disclosure: Goltz reports no relevant financial disclosures.