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Lubricant for wear testing of joint replacements and associated materials

a joint replacement and lubricant technology, applied in the direction of biochemistry apparatus and processes, enzymes, additives, etc., can solve the problems of affecting the wear and tear of joints, and each of the serum protein constituents is likely to have a unique effect on wear and tear,

Inactive Publication Date: 2008-09-04
BRANDT JAN M +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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.

Method used

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  • Lubricant for wear testing of joint replacements and associated materials
  • Lubricant for wear testing of joint replacements and associated materials
  • Lubricant for wear testing of joint replacements and associated materials

Examples

Experimental program
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Effect test

example 1

Serum Protein Concentration and Protein Constituent Fractions Vary Depending on the Lubricant

[0072]The ratio of albumin / globulin in serum lubricant at the start of a wear test has been used as an indicator of wear in several hip simulator studies (Wang et al (2004) J. Biomed. Mater. Res. 68B(1):45-52), however, determination of clinically relevant fractions of specific serum proteins, including α-1, α-2, β, and γ-globulins, in wear simulator testing has not been evaluated, nor has the relevance of these protein fractions in wear simulator testing.

[0073]Twenty patients were selected to participate in the present study: ten male and ten female patients, with a mean age of 64.7 years (range, 60-70 years), undergoing surgery for primary total knee arthroplasty (Table 1). Patients who had previously received any knee injections for pain relief (i.e. Cortisone (a steroid hormone) or Synvisc® HYLAN G-F 20 (Genzyme, Cambridge, Mass.)), or patients with rheumatoid arthritis (RA) or other inf...

example 2

Osmolality and Trace Element Concentrations Vary Depending on the Serum Lubricant and Dilution Medium

[0079]Osmolality is a direct measure of the ionic strength of a solution and is a regarded as a systemic, patient specific value (Baumgarten et al. (1985) J. Bone Joint Surg. Am. 67(9):1336-1339). Individual calf sera samples were diluted either with DW or PBS. The choice of dilutive media was suggested to affect solution osmolality given that osmolality has been shown to affect the thermal stability of proteins in solution (Giancola et al. (1997) Int. J. Biol. Macromol. 20(3):193-204) and, thus, might also affect the protein degradation and the PE wear rate in simulator wear testing.

[0080]In the present study, an osmometer (Osmometer 5520, Wescor, Logan, Utah) was used to determine the osmolality of the SF, different serum lubricants and their dilutive media. The osmometer determined the osmolality following the freezing-point depression test strategy at atmospheric pressure. This s...

example 3

Role of Bacterial Growth on Wear Testing

[0084]A six million cycles wear tests was performed on the knee simulator (AMTI, Waltham, Mass.) with AMK implant (FIG. 7) components (Table 4) (DePuy Orthopaedics, Warsaw, Ind.). There calf serum lubricants were used: BCS lubricant (BCS+DW+SA), NCS lubricant (NCS+DW+SA), and ACS lubricant (ACS+DW+SA).

TABLE 4Test protocol from 0-6 Mc.LubricantMcL implantsR implants0-3BCS + DW + SABCS + DW + SA  3-4.5ACS + DW + SANCS + DW + SA4.5-6  BCS + DW + SABCS + DW + SABCS = bovine calf serum;DW = distilled water;SA = sodium azide;ACS = alpha calf serum;NCS = newborn calf serum.

[0085]The wear rates obtained from the testing with the BCS lubricant, NCS lubricant, and ACS lubricant indicated that the fractions of serum proteins in the lubricant had a significant effect on wear rate (FIG. 8). The serum lubricants were found to have wear varying rates where BCS lubricant >NCS lubricant >ACS lubricant.

[0086]Electrophoresis data obtained for serum lubricant sam...

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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...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C10M125/24
CPCA61K35/16C12Y304/21073C12N9/6462
Inventor BRANDT, JAN-MCHARRON, KORY D.ZHAO, LINMEDLEY, JOHN B.MACDONALD, STEVEN J.
Owner BRANDT JAN M
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