Lubricant for wear testing of joint replacements and associated materials

Abstract

The present invention relates to an artificial synovial fluid composition that mimics the tribological properties of human, osteoarthritic synovial fluid (SF) for the main purpose of in vitro wear testing. There is described an artificial synovial fluid composition comprising: a) a mammalian serum having i) a total protein concentration of from about 10 to about 45 g / L; ii) an albumin fraction of from about 55% to about 80% w / w %; iii) an α-1 globulin fraction of from about 3% to about 6% w / w %; iv) an α-2 globulin fraction of from about 5% to about 10% w / w %; v) a β-globulin fraction of from about 3% to about 20% w / w %; vi) a γ-globulin fraction of from about 5% to about 20% w / w %; vii) a calcium (Ca) concentration of from about 0.1 mmol / L to about 3 mmol / L; viii) a magnesium (Mg) concentration of from about 0.05 mmol / L to about 0.8 mmol / L; ix) an inorganic phosphate (P) concentration of from about 0.1 mmol / L to about 1.5 mmol / L; x) an iron (Fe) concentration of from about 0.001 mmol / L to about 0.1 mmol / L; xi) a peptide concentration at a 2,000 Da molecular weight cut-off of from about 0.005 g / L to about 10 g / L; xii) a maximal transition midpoint temperature, Tm-cp-max, of from about 330 K to about 350 K at a concentration molality of from about 0.005 to about 0.15 mmol / L measured at a scan rate of from about 20 K / hour to about 100 K / hour; xiii) a total enthalpy change, ΔH, of from about 650 kJ mol−1 to about 1200 kJ mol−1 at a set concentration molality of 0.05 mmol / l measured at a scan rate of 60 K / hour; xiv) a total entropy change, ΔS, of from about 1.5 kJ mol−1 K−1 to about 4 kJ mol−1 K−1 at a concentration molality of from about 0.005 mmol / l to about 0.15 mmol / l and a scan rate from about 20 K / hour to 100 K / hour; wherein the ratio of albumin to total globulin (α-1 globulin+α-2 globulin+β-globulin+γ-globulin fractions) in solution is from about 1.5 to about 3; b) a buffer for maintaining a solution osmolality of from about 200 mmol / kg to about 400 mmol / kg; c) hyaluronic acid (HA) at a concentration of from about 0.1 g / L to about 6 g / L; d) hyaluronic acid (HA) with a molecular weight of from 1 MDa to 4 MDa; and e) a pH level of about 7 to about 8.

Description

RELATED APPLICATIONS[0001]This application claims the benefit of U.S. Provisional Application No. 60 / 899,894 filed Feb. 7, 2007 and U.S. Provisional Application No. 61 / 006,102 filed Dec. 19, 2007, each of which are incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates to an artificial synovial fluid composition that mimics the tribological properties of human, osteoarthritic synovial fluid (SF) for the main purpose of in vitro wear testing. More specifically, the invention relates to a composition having specified total serum protein concentration, specific fractions of serum protein constituents, peptide concentration, level of osmolality (an indicator of the ionic strength of a solution), hyaluronic acid (HA) concentration and antimicrobial agents to simulate synovial fluid wear properties in a tribological analysis of an artificial joint in a sterile environment.BACKGROUND OF THE INVENTION[0003]Artificial joints are typically subjected to simu...

AI Technical Summary

Problems solved by technology

Wear particles in vivo can initiate periprosthetic osteolysis, a serious complication in joint replacement arthroplasty that makes expensive revision surgery necessary.

Unfortunately, they vary between wear test laboratories.

By not specifying the calf serum type, the standards avoid giving specific fractions of the protein constituents and each of these serum protein constituents is likely to have a unique effect on wear.

The wear process may damage the proteins and, thus, initiate unfolding, precipitation and shear of the proteins (FIG. 1).

In particular, heat accumulation at the interface of the artificial joint articulation may facilitate the protein degradation and increase the PE wear rate (Liao et al.

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