Taper Material Loss in Total Hip Replacements: Is It Affected by Joint Friction?

Area of Science:

• Orthopedic biomechanics
• Biomaterials science
• Implant retrieval analysis

Background:

• Modular joint replacements, particularly metal-on-metal hip implants, can generate metal debris and corrosion products from taper junctions, contributing to implant failure.
• Understanding the factors influencing taper wear and corrosion is crucial for enhancing the longevity and performance of joint replacement implants.

Purpose of the Study:

• To investigate the relationship between taper material loss and joint frictional moments in retrieved metal-on-metal hip implants.
• To identify factors correlating with taper wear, including friction, articular wear, head diameter, head-cup clearance, and duration of implantation.

Main Methods:

• Analysis of 85 retrieved large-diameter metal-on-metal hip implant head-and-cup pairs.
• Quantification of head taper material loss and articular surface wear using metrology.
• Measurement of joint frictional moments during simulated gait in a biomechanical model.

Main Results:

• Peak frictional moments ranged from 9.1 to 26.3 Nm (average 17.3 ± 2.7 Nm).
• Head taper material loss (0.04–25.57 mm3) was generally lower than articular wear (0.80–351.75 mm3).
• Taper material loss showed a significant positive correlation with time in vivo (R = 0.34, p < 0.01) but no significant correlation with frictional moments or head-cup clearance.

Conclusions:

• Head taper wear volumes were typically less than articular surface wear volumes.
• No statistical correlation was found between taper wear and frictional moments in the studied implants.
• High friction at the taper interface does not appear to be a primary driver of material loss, despite potential for high bending moments.