Characterization of protein degradation in serum‐based lubricants during simulation wear testing of metal‐on‐metal hip prostheses

Abstract

A size exclusion high performance liquid chromatography (SEC-HPLC) method has been developed which is capable of separation and quantitation of bovine serum albumin (BSA) and bovine serum globulin (BSG) components of serum-based lubricant (SBL) solutions. This allowed characterization of the stability profiles of these proteins when acting as lubricants during hip wear simulation, and identification of wear-specific mechanisms of degradation. Using cobalt-chromium metal-on-metal (MOM) hip joints, it was observed that BSA remained stable for up to 3 days (215K cycles) of wear testing after which the protein degraded in a fairly linear fashion. BSG on the other hand, began to degrade immediately and in a linear fashion with a rate constant of 5% per day. Loss of both proteins occurred via the formation of high molecular weight aggregates which precipitated out of solution. No fragmentation of the polypeptide backbone of either protein was observed. Data obtained suggest that protein degradation was not due to microbial contamination, denaturation at the air-water interface, or frictional heating of articulating joint surfaces in these studies. We conclude that the primary source of protein degradation during MOM simulation testing occurs via high shear rates experienced by SBL solutions at articulating surfaces, possibly coupled with metal-protein interactions occurring as new and reactive metal surfaces are generated during wear testing. The development of this analytical methodology will allow new studies to clarify the role of SBL solutions in wear simulation studies and the interactions and lubricating properties of serum proteins with prosthetic surfaces other than MOM.

Acetabular Cups in 60 mm Metal-on-Metal Bearings Subjected to Dynamic Edge-Loading with 70° Peak-Inclination in 10-Million Cycle Simulator Study

“…It is well documented that protein contamination from serum lubricants can be a confounding problem in gravimetric wear assessments [61][62][63][64]. Our prior 5 Mc study revealed major contamination confounded the wear assessments [60].…”

“…This was an encouraging result but the 5 Mc wear study suffered from two limitations. Gravimetric wear assessment of the bearings was compromised due to transfer of proteinaceous debris from the lubricant [61,62]. This contamination appeared during "run-in" and "steady-state" wear phases.…”

Metal-on-metal total hip arthroplasty: is there still a role in 2016?

“…Since these components were designed to be less than a full hemisphere, cups placed with an abduction angle of 45°would behave as if they were in a more vertical position, leading to increased edge loading, wear, and circulating metal ion levels. Additionally, early components with narrow clearance on the perimeter can be deformed with impaction causing failure of fluid film lubrication and increased wear [16][17][18].…”

Silicon Nitride Bearings for Total Joint Arthroplasty

“…Protein adsorption onto bearing surfaces can be thermally or mechanically activated (i.e., frictional heating, pressure, or high shear) [114,115]. Their presence is often difficult to detect (<250 nm), but their effect in reducing wear has been extensively examined [45,62,[116][117][118][119][120][121][122][123][124][125].…”