How Does Wear Rate Compare in Well-functioning Total Hip and Knee Replacements? A Postmortem Polyethylene Liner...

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Wear Analysis

Background:

• Osteolysis is a significant concern in total hip replacements (THRs) and total knee replacements (TKRs), historically linked to polyethylene wear.
• While osteolysis is more prevalent in THRs, polyethylene wear in TKRs warrants further investigation, especially volumetric material loss in tibial inserts.

Purpose of the Study:

• To quantify and compare volumetric wear in autopsy-retrieved total knee replacement (TKR) tibial inserts and total hip replacement (THR) acetabular liners.
• To determine the wear rate ratio between TKR and THR components made from identical polyethylene materials.
• To analyze wear patterns exhibited by both TKR and THR components.

Main Methods:

• Comparison of 23 THR (Harris-Galante) and 20 TKR (Miller-Galante II) components retrieved postmortem.
• All components were manufactured from identical polyethylene formulations, with similar processes and gamma-in-air sterilization.
• Wear volume was measured using metrology, with an autonomous mathematical reconstruction method for tibial inserts.

Main Results:

• THR acetabular liners exhibited a wear rate of 38 mm³/year (47 mm³/year excluding low-activity patients).
• Normally wearing TKR tibial inserts showed a wear rate of 17 mm³/year.
• After adjusting for age, the TKR/THR wear rate ratio was 0.5, indicating lower wear in TKRs.

Conclusions:

• Excluding delamination, TKRs demonstrated lower articular wear rates compared to THRs in historical polyethylene components.
• The reduced wear rate in TKRs is consistent with the lower incidence of osteolysis observed in knee replacements versus hip replacements.