WO2001024864A1

WO2001024864A1 - Medical cutting tool lubricant composition

Info

Publication number: WO2001024864A1
Application number: PCT/US2000/027698
Authority: WO
Inventors: R. Steven Marcus
Original assignee: Marcus R Steven
Priority date: 1999-10-04
Filing date: 2000-10-04
Publication date: 2001-04-12
Also published as: AU7998800A

Abstract

A lubricant composition comprising a fatty acid, or mixtures of fatty acids, a non-amine neutralizer, and an organic phosphate. The composition may optionally comprise a vegetable, mineral or animal oil or a synthetic ester. The lubricant is especially useful in surgical operations involving cutting, planing, or drilling bones or teeth for reducing pain and promoting quicker healing by reducing the cutting interface temperature due to friction heat produced during the operation. The lubricant is also useful in reducing pain after joint surgery involving bone or cartilage by the lubrication of the joint with the lubricant composition following the joint surgery by either leaving excess lubricant used in the joint during surgery or by injecting the lubricant into the joint after surgery. The composition is also useful for the lubrication of any object to be inserted into the body, such as a probe, catheter or gloved finger.

Description

MEDICAL CUTTING TOOL LUBRICANT COMPOSITION

FIELD OF THE INVENTION

The invention relates to a lubricant that is useful in certain medical procedures. Specifically, the invention relates to a lubricant useful in bone and tooth surgery in which drilling, cutting, planing, scraping, or other operations are performed on the bone or tooth; for topical or internal applications whenever probes, appliances, or other devices are inserted into the body; or with the lubrication of joints of the body following joint surgery.

BACKGROUND OF THE INVENTION Bone and tooth surgery requires that a cutting tool or a drill is used to change the shape of, or pierce the surface of, the bone or tooth. This process generates heat, which is destructive to the bone, tooth, or surrounding tissue. Typically, when the heat of the tool or the bone or tooth exceeds 50°C, damage to the tissue will occur. Furthermore, when heat is generated, pain increases for the patient and healing time increases. In the standard method, there is a degree of tool spalling that results in traces of metals being left in the patient's body.

Current practice is to cool the area being cut, shaped, or drilled, and to cool the tool itself, by flowing water or an isotonic saline solution over the tool and the body parts that come into contact with the tool. In some practices, the coolant is sent through a channel inside the tool or along flutes on the tool. The problem with this practice is that the water or saline solution does not adequately cool the tool and the parts being cut, shaped, or drilled.

Accordingly, there is a need to find a coolant solution that can provide improved cooling, reduce heat build-up and remove excessive heat through absorption, while being harmless to tissue and bodily fluids it contacts. The ideal coolant will have a surface tension considerably less than that of water or saline solutions, heat absorption nearly equal to that of water, and no adverse effects on body parts, body tissue, or body fluids.

A result of joint surgery, such as arthroscopy, is the pain caused by contact between bones and bones/cartilage in the first few days following the surgery. Currently, the only relief available is application of pain killers, either orally, intravenously, or by injection. Such pain killers often have serious side effects and can potentially be dangerous to the patient's health. Thus, there is a need for a way to relieve joint pain without the need for pharmaceutical pain killers while being harmless to the treated joints or to the body.

SUMMARY OF THE INVENTION

I have determined that increasing cooling is not a sufficient solution for preventing the harmful temperature levels. The appropriate solution to the problem is to reduce the production of heat, thereby allowing the coolant to adequately carry away the lower amount of heat that is produced. Thus, the ideal coolant will have a high degree of lubricity to reduce the friction of the tool, thereby reducing the amount of heat produced, and reduce, or eliminate, the spalling of the tool and consequent metallic residue to be left in the patient's body.

The present invention provides an improved coolant which is also a lubricant compositions that unexpectedly meet the above stringent requirements. Specifically, the present invention is directed to a multi-purpose lubricant composition, which is useful in surgical operations involved with cutting, planing, or drilling bones or teeth; with the lubrication of joints of the body following surgery; with the lubrication of any object to be inserted into the body; or for non- medical applications. In one aspect, the lubricant composition of this invention comprises a combination of a fatty acid or mixtures of fatty acids neutralized with a non-amine alkaline and complexed with an organic phosphate ester.

In one of its compositional aspects, the present invention is directed to a lubricant composition wherein said lubricant contains at least about 1.0 percent organic phosphate esters by weight of the lubricant composition and at least about 0.025 percent by weight fatty acid, neutralized to at least about pH 7, preferably about 7.2 to about 7.4, with a non-amine alkaline.

In another aspect, the compositions of this invention can additionally comprise a water solvent and, further, a vegetable oil, a mineral oil, a synthetic ester, and/or an animal oil.

In one of its method aspects, the lubricant composition of the present invention is directed to the cutting edge of a medical tool or drill and provides wetting, lubrication, and cooling to the tool and the bone or tooth being shaped or cut.

In another of its method aspects, the lubricant composition of the present invention is applied directly to the bone, or the cartilage, or both, of a joint of the body following surgery to the joint, to reduce the pain caused by contact between bones and bones/cartilage following the surgery.

In another of its method aspects, the lubricant composition of the present invention is applied directly to a device or a probe to be inserted into the body. In another of its method aspects, the lubricant composition of the present invention is applied directly to a catheter tube to be inserted into the body. In one embodiment, the catheter is to be inserted into the urethra and into the bladder. In another embodiment, the catheter is to be inserted into a vein or an artery.

In yet a further of its method aspects, the lubricant composition of the present invention is applied directly to a gloved finger to be inserted into a body opening, for example when the fmger is to be inserted into a rectum for examining the prostrate gland. The lubricant composition may also be used as a sexual lubricant.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to the discovery of a lubricant composition useful in surgical processes involving the cutting, shaving, or drilling of bones and teeth. In another application, it is useful as a lubricant for appliances, probes, or other devices to be inserted into bodily orifices or otherwise into the body. In yet another application, it is useful as a lubricant to relieve the pain in joints resulting from surgery to the joint. In a further embodiment, it is useful in certain non-medical applications to the body, such as a sexual lubricant. Basically, the lubricant composition comprises a fatty acid or mixtures of fatty acids neutralized with non-amine alkaline or base and complexed with an organic phosphate ester. All components of the lubricant composition are chosen to have no adverse effects on body parts, body tissue, or body fluids and to be absorbable by the body.

The term "fatty acid" means a saturated or unsaturated fatty acid compound having the following formula R— COOH, where R is an alkyl group consisting of at least about 15 carbon atoms. Examples of such "fatty acids" include, but are not limited to, stearic acid, isostearic acid, oleic acid, isooleic acid, palmitic acid, isopalmitic acid, and mixtures thereof. Other fatty acids are useful in this component of the composition. The fatty acid used in the invention can consist of one fatty acid or a combination of fatty acids, and the term "fatty acid" as used herein encompasses one or more fatty acids.

The total amount of fatty acid generally employed in the lubricant composition is from about 0.025 weight percent to about 3.0 weight percent based on the total weight of the lubricant composition (including solvent). More preferably, the amount of the fatty acid component is between about 0.05 weight percent and about 2.0 weight percent based on the weight of the lubricant composition.

It has been found that the pH of the composition may be adjusted to the desirable range with the addition of a neutralizing amount of non-amine alkalines such as hydroxides of potassium or sodium, or carbonates of potassium or sodium. The term "neutralizing amount" means that amount of a non-amine alkaline employed in the lubricant that is sufficient to adjust the pH of the lubricant to a level appropriate for medical use in contact with body tissues, bone or teeth, and preferably to cause the pH of the lubricant to be at least about 7. Most appropriately, the amount of alkaline in the composition will range from about 0.5 weight percent to about 2.0 weight percent of the total lubricant composition (including solvent), and preferably the amount of alkaline will be that amount necessary to arrive at a final composition pH of 7.2 to 7.4. The alkaline can be a combination of alkalines. In a preferred composition, the alkaline used is sodium bicarbonate, NaHCO₃. It further has been found that phosphate esters act synergistically with the non-amine neutralized fatty acids to yield increased lubrication properties of the composition. The term "phosphate esters" means a surfactant comprising a diester or monoester having at least one phosphate group. In general, the phosphate ester has the formula OP(OR)₃ where R may represent an aryl or alkyl group. The phosphate esters useful in the compositions of this invention can be organic esters of phosphinic or phosphonic acids or can be phosphoric esters of glycerols, glycols, and the like. More preferably, the phosphate ester is Phosfac^* HR 719 or Phosfac^® RA 600 (Rhone-Poulenc, Cranbury, NJ).

The "effective complexing amount" of phosphate esters in the lubricant composition will be that amount that gives increased lubrication properties to the composition, preferably the lubrication properties suitable for medical uses as set forth herein. The effective complexing amount is generally from about 1.0 weight percent to about 5.0 weight percent based on the total weight of the lubricant composition (including solvent). Preferably, the amount of phosphate esters will be from about 3.0 weight percent to about 4.0 weight percent, and more preferably will be about 4.0 weight percent based on the total weight of the lubricant composition.

It has further been found that an appropriate solvent for the lubricant composition can be tap water, de-ionized water, or distilled water, which for medical use will be sterile. The effective amount of solvent in the lubricant is generally from about 70 weight percent to about 98 weight percent based on the total weight of the final lubricant composition. Preferably, the amount of solvent will be from about 91 weight percent to about 98 weight percent of the total lubricant, and most preferably between 94 and 98 weight percent. It has further been found that the addition of vegetable oils or derivatives thereof to the lubricant composition of this invention further improves the boundary layer lubrication properties of the lubricant composition. The term "vegetable oils" refers to, for example, but is not limited to, jojoba bean oil, soya bean oil, castor bean oil, corn oil, palm oil, rapeseed oil, and the like, as well as derivatives thereof. The vegetable oils are chosen to be compatible with the lubricant composition of this invention. A presently preferred vegetable oil is castor oil. The amount of vegetable oil in the lubricant composition is preferably from about 0.005 weight percent to about 2.0 weight percent based on the total weight of the lubricant composition (including solvent). Preferably, the amount of vegetable oil will be from about 0.05 weight percent to about 0.5 weight percent, and more preferably is 0.08 weight percent of the composition.

It has further been found that the addition of hydrogen peroxide, H₂O₂, is useful in the final adjustment of pH, and it is known to act as a bactericide, further enhancing the medical value of the lubricant. Further, the hydrogen peroxide acts as a stabilizer in the composition to extend its useful shelf life. The amount of hydrogen peroxide in the lubricant is preferably between about 6 parts per million ("ppm") and about 60 ppm of the total composition (including solvent). Preferably, the amount of hydrogen peroxide will be from about 6 to about 24 ppm, and more preferably about 18 ppm.

The lubricant composition of the invention may also contain one or more other useful additives, such as anti-foam agents, emulsifiers, surfactants, preservatives, viscosity adjusters and the like. The lubricant composition may also contain mineral oil, synthetic esters, or animal oils. The viscosity of the neat or diluted lubricant composition of this invention can be adjusted by conventional additives, which are suitable for medical use, to provide the viscosity appropriate for the particular application at hand. For example, use of the lubricant composition in a bone or tooth drilling tool would preferably be of low viscosity and high lubricity for pumping through the drill tool. In contrast, use of the lubricant composition for sexual use or on a device or gloved finger inserted into a body cavity, would preferably be of a high viscosity and high lubricity so a coating of the lubricant composition would remain as applied to a surface until used. In some applications a gel form of the lubricant composition of this invention would be preferred.

The lubricant composition can be modified so as to match the total alkalinity of a particular bodily fluid, if desired. Typically, the total alkalinity can be adjusted with sodium bicarbonate, sodium chloride, or other carbonates, or chlorides. In like manner, the osmotic pressure of the composition can be varied, if necessary, by methods known in the art. These adjustments do not change the lubricant value of the lubricant composition.

A presently preferred embodiment of the lubricant composition of this invention is: solvent (preferably water), about 94.75 wt%; a fatty acid or fatty acid mixture, about 0.10 wt% ; a non-amine alkaline (preferably sodium bicarbonate), about 1.00 wt%; a phosphate ester, about 4.00 wt%; hydrogen peroxide (3 % solution), about 0.06 wt%; and castor oil complex, about 0.08 wt% .

The lubricant composition may be applied neat, or it may be diluted in sterile water and applied to the cutting tool, drill, probe, catheter, appliance, or other device by flooding, spraying, or dipping the device. Following surgery on joints or bones, some or all of the residual lubricant may be left in the body to lubricate the joints, bones, and cartilage or can be injected after surgery for the same purpose. In addition, the lubricant composition may be injected into joints for lubrication of cartilage and bone surfaces to delay or prevent the necessity of surgery or other treatment. For such applications, the viscosity may be adjusted as required, and the lubricant composition of this invention may be formulated with a less soluble or insoluble carrier to provide increased residence time in a joint into which it is injected. The lubricant can be easily removed from a device or surface with any mild alkali or water wash.

In order to further illustrate the present invention and advantages thereof, the following specific examples are given, it being understood that the same are intended only as illustrative and in nowise limitative of the composition and method inventions disclosed herein.

EXAMPLE 1: DRAWBEAD TEST OF LUBRICANTS

The laboratory process selected for these tests is known as a Drawbead Tester, described in ASTM D-4173-82. This is a device for evaluating the relative lubricity of fluids for machining applications. While it is primarily used in metalworking applications, it is a valid comparison of fluids used to cut, drill, or machine any hard surface. The device measures the pull strength required to pull a standard metal strip through a labyrinth created by three overlapping half-round dies. The dies are clamped together under controlled pressure with a constant force, usually 400 to 1500 pounds.

For these tests, 400 pounds was selected because the lubricity of saline solution is so poor that the strips were pulled apart at higher hold-down pressures. Two strips were pulled through for each test. Prior to the first pull-through, both the strip and the dies were coated with the substance to be tested. Prior to the second pull-through, only the strip was coated. The second reading was selected as the comparative measurement since it in part measures the effect of residual matter left on the dies, and it is more comparable to the experience of longer- duration machining. The test strips were cold-rolled steel with a thickness of 0.0325 inches. Prior to testing, the thickness of each strip was measured, with a rejection tolerance of 0.001 inches. Each strip was sanded on the edges to prevent any burr interference with the test reading. The strip is pulled through the dies with a pulling force of up to 10,000 pounds and for a distance of about 6 inches. The test deforms the strip into a "roller coaster" pattern.

All samples were run in duplicate or triplicate, and the average pull strength was compared. The less pull strength required, the better the lubrication value of the product. A difference of 1.0 is considered significant in these tests. The strips were also examined for scoring, stretching, or tearing. The following results were found:

Results of Drawbead Tests

Product 1^st Pull 2^nd Pull Av . Pull Comments

Isotonic Saline 14.39 15.47 14.930 loud squeal solution

Lubricant 11.90 12.39 12.145 smoc silent composition The lubricant composition was of the following formula:

Component Weight Percent distilled water 94.75 wt% sodium bicarbonate 1.00 fatty acid: isoteric 0.10 castor oil complex 0.08 phosphate ester: RA-600 4.00 hydrogen peroxide, 3 % 0.06

EXAMPLE 2: SURFACE TENSION

The surface tension of a liquid is one indication of the ability of a liquid to wet a surface with which it comes into contact. In cutting operations, low surface tension liquids more rapidly coat the surface to be cut and the cutting edge of the tool employed. Therefore, lower surface tension lubricants are more desirable than higher surface tension lubricants or cutting coolants.

Surface tension of a liquid may be measured with various devices and methods. The method of choice in this experiment is the method outlined in Findlay's Practical Physical Chemistry, 8th Edition, pp. 94-97, 1959, Longsman's. This states that when a liquid wets a capillary tube, the liquid will rise in the tube. The height of the rise is dependent on the tube diameter and the surface tension of the liquid. Formulas are given to calculate for the surface tension in dynes/cm, with corrections for acceleration due to gravity and for altitude.

In the surface tension tests described above, the following results were calculated from the experiments. The lubricant composition was the same as that tested in Example 1. Material Tested Surface Tension (dynes/cm) distilled water 64.3 tap water 59.7 isotonic saline solution 66.8 lubricant composition 29.2

While the invention has been described in terms of various preferred embodiments, the skilled artisan will appreciate that various modifications, substitutions, omissions and changes may be made without departing from the scope thereof. Accordingly, it is intended that the scope of the present invention be limited solely by the scope of the following claims, including equivalents thereof.

Claims

1. A lubricant composition comprising a fatty acid, a neutralizing amount of a non-amine alkaline, and an effective complexing amount of a phosphate ester.

2. The lubricant composition according to claim 1 wherein the fatty acid component of the composition comprises stearic acid, isostearic acid, oleic acid, isooleic acid, palmitic acid, or isopalmitic acid.

3. The lubricant composition according to claim 1 wherein the fatty acid component is in the amount of about 0.025 to about 3.0 weight percent based on the total weight of the composition.

4. The lubricant composition according to claim 1 wherein the phosphate ester component comprises the formula OP(OR)₃ where R comprises an aryl or alkyl group.

5. The lubricant composition according to claim 1 wherein the phosphate ester component is in the amount of about 1 to about 5 weight percent based on the total weight of the composition.

6. The lubricant composition according to claim 1 wherein the non-amine alkaline component comprises sodium bicarbonate.

7. The lubricant composition according to claim 1 further comprising an aqueous solvent.

8. The lubricant composition according to claim 1 further comprising a vegetable oil, mineral oil, a synthetic ester, or an animal oil.

9. The lubricant composition according to claim 7 further comprising a vegetable oil, a mineral oil, a synthetic ester, or an animal oil.

10. A lubricant composition comprising the following components:

Component Weight Percent solvent about 94.75 non-amine alkaline about 1.00 fatty acid about 0.10 castor oil complex about 0.08 phosphate ester about 4.00 hydrogen peroxide, 3 % about 0.06

11. The lubricant composition according to claim 10 wherein the solvent comprises water.

12. The lubricant composition according to claim 10 wherein the non-amine alkaline component comprises sodium bicarbonate.

13. A method of shaping or cutting a bone or tooth, the method comprising directing a lubricant composition to the cutting edge of a tool or drill prior to or during the shaping or cutting operation to provide wetting, lubrication, or cooling to the tool or drill and to the bone or tooth being shaped or cut; the lubricant composition comprising a fatty acid, a neutralizing amount of a non-amine alkaline, and an effective complexing amount of a phosphate ester.

14. A method for treating a tool or a drill for shaping or cutting a bone or a tooth, the method comprising directing a lubricant composition to the cutting edge of the tool or drill; the lubricant composition comprising a fatty acid, a neutralizing amount of a non-amine alkaline, and an effective complexing amount of a phosphate ester.

15. A method of reducing pain caused by joint surgery, the method comprising applying a lubricant composition directly to the bone, or to the cartilage, or both, of a joint of the body following surgery to the joint; the lubricant composition comprising a fatty acid, a neutralizing amount of a non-amine alkaline, and an effective complexing amount of a phosphate ester.

16. A method for treating a device or a probe to be inserted into the body, the method comprising applying a lubricant composition to the device or probe; the lubricant composition comprising a fatty acid, a neutralizing amount of a non- amine alkaline, and an effective complexing amount of a phosphate ester.

17. The method according to claim 16 wherein the device or probe is a catheter.

18. The method according to claim 16 wherein the device or probe is a gloved finger.