Is Modular Dual Mobility Viable for Young Patients?

New research from Rush University Medical Center, Chicago, Illinois and Washington University Orthopedics, Barnes Jewish Hospital in St. Louis, Missouri has examined the issue of using modular dual mobility (DM) prostheses in young, active patients.

The study, “Is a modular dual mobility acetabulum a viable option for the young, active total hip arthroplasty patient?” appears in the March 31, 2019 edition of The Bone and Joint Journal.

Denis Nam, M.D., M.Sc., associate professor of orthopedic surgery at Rush and study co-author explained to OTW the purpose behind this new study. “The use of modular dual mobility prostheses has increased in popularity, especially in patients deemed to be at higher risk of instability. However, little data is present assessing their performance in younger, more active patients.”

“Concerns regarding the potential for corrosion between the cobalt-chromium liner and titanium acetabular component have been reported, thus we analyzed whole blood metal ion levels in these patients from preoperatively to 1- and 2-years postoperatively.”

The researchers undertook a prospective study of patients between 18 and 65 years of age, with a body mass index (BMI) < 35 kg/m² and a University of California at Los Angeles (UCLA) activity score > 6, all of whom received a modular cobalt-chromium acetabular liner, highly crosslinked polyethylene mobile bearing, and cementless titanium femoral stem for their primary THA [total hip arthroplasty].

According to Dr. Nam, “The most important finding was that overall, this prostheses combination is performing well at 2-years postoperatively in our small cohort of patients. However, it is important to note that 5 patients at 1-year postoperatively had a whole blood cobalt level above the reference range, and 4 patients at 2-years postoperatively had a whole blood cobalt level above the reference range.”

“Of these four patients, 3 had an inner ceramic femoral head and thus the presumed source of cobalt is from the modular, acetabular liner. However, at 2-years postoperatively, the maximum cobalt level was 0.94 ug/L which was actually less than was seen at 1-year postoperatively. Continued surveillance is mandatory to evaluate this bearing combination both for potential corrosion and wear performance moving forward.”

“This study certainly has its limitations and larger, prospective cohorts are necessary to corroborate these results. However, this study demonstrates that use of a modular, dual mobility prosthesis and cementless, tapered femoral stem has shown encouraging results even in a younger, active cohort of patients. Thus, our results justify both continued surveillance of this cohort and also future studies examining its performance in larger cohorts of patients.”

“In our opinion, this study shows encouraging results of a specific modular, dual mobility implant. However, it is important for surgeons to recognize the limitations of our investigation and that this is only a small cohort of patients at short follow-up. We would recommend further, prospective investigations demonstrating excellent long-term outcomes before recommending its widespread use in a younger, active population of patients.”