Dartmouth Engineers Identify Primary Determinants of Artificial Knee Wear

Dec 16, 2021 | by Julie Bonette

Dartmouth engineers led one of the largest analyses of wear of the polyethylene tibial insert in artificial knees — a leading cause for revision surgeries. The analysis determined that greater patient age at implantation and female sex, as well as a polished tibial tray, highly cross-linked polyethylene, and constrained knee design, are factors which together reduce the tibial insert wear rate by nearly 40 percent.

The paper, "What factors drive polyethylene wear in total knee arthroplasty [TKA]," was recently published by The Bone & Joint Journal. The analysis was led by Dartmouth research engineers Barbara Currier and the late John Currier '79 Th'81, and Professor Doug Van Citters '99 Th'03 Th'06, associate professor of engineering. Mayo Clinic orthopedic surgeons Matthew P. Abdel and Daniel J. Berry '80 and University of New Hampshire at Manchester Adjunct Assistant Professor of Biotechnology Alexander Titus served as co-authors.

"Findings from this work give surgeons a context for assessing the appropriate TKA implant for their patients and industry a framework for future knee designs."

Professor Doug Van Citters '99 Th'03 Th'06

(l to r) The late John Currier '79 Th'81, Doug Van Citters '99 Th'03 Th'06, and Barbara Currier (photo by Doug Fraser)

The authors also hope their work will decrease the need for revision surgeries and reduce the associated significant cost burden on the healthcare system.

More than 3,500 total knee replacements that had experienced some level of failure were retrieved from more than 225 surgeons over a period of over 20 years for the study, which included five different designs from four manufacturers.

"Because knee implants of all designs and materials may be found in patients with a variety of demographic factors, it is difficult to isolate variables that might contribute to knee wear in the real-world setting," said Van Citters. "The Dartmouth Biomedical Engineering Center for Orthopaedics is one of few labs having sufficient retrieved specimens to make this sort of analysis possible."

The researchers estimated wear by measuring polyethylene thickness change and used linear regression statistical analyses to test the association of 12 different patient and design variables. Overall, each year of TKA implant use is associated with a 1.7 percent increase in wear rate. The authors also found that, when looking at the ages of patients at the time of surgery, a patient's wear rate would typically be about 7 percent less than those born a decade earlier. In addition, the wear rate for females was about 19 percent lower than males.

The authors also found that a higher body mass index (BMI) was not indicative of tibial insert wear.

The study did not examine patient activity level or implant alignment, which could also be significant factors associated with polyethylene wear.

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