CATGUTSterile surgical catgut consists of a strand prepared from collagen derived from healthy mammals after purification and sterilization.

Source:Most widely used source for preparation of catgut is submucosa of small intestine of sheeps and lambs to lesser extent from serosa layer of cattle.

F actors to be considered in manufacture of catgut:Diameter of intestine should not be more than 18mm.Intestine of animals should not have scar tissue.Younger the animal, smaller should be the intestine and less likely to be affected by the food.A number of manufactures of catgut use only 1st 8mm of intestine measured from duodenum.Such intestine are called Ligature casings or Runners.

Procedure of removal of intestine from animals:

Gut is removed by gut pullers

Cleaned to remove fecal matter

Inspected,measured and then preserved either in frozen state or salted state.

As intestine is most vulnerable to bacterial attack and

decomposition, the steps involved in the removal of gut in

slaughter house with precaution such that bacterial contamination is at its minimum.

Layers of intestine:There are 4 layers if gut (i,e:) tunica serosa,tunica musculosa,tunica submucosa and tunica mucosa.Of all these layers,tunica submucosa is suitable for preparation of the catgut.

Steps involved in manufacturing of catgut from the intestine:

1. Thawing 2. Splitting3. Cleaning of mucosa4. Spinning5. Polishing6. Guaging7. Sterilization8. Standardisation

Thawing:The first step in manufacturing of catgut is to soak ligature casing in water to thaw or to remove the salt and prepare them for splitting.

Splitting:Splitting or cutting is carried out by inserting the curved horn of cutting tool into the end of casing and pulling the runner over the cutting blades.Horns are used to identify the rough side of the intestine.Rough side and smooth side of intestine are kept apart throughout the process as they behave in differnt case physically and chemically.

Cleaning of mucosa:

This step is used to remove mucosa,muscle and any remaining serosa layers after the splitting step.This step is usually done by treating with alkaline solutions.When the ribbons are judged satisfactorily cleaned,they are cut to a predetermined length, assembled in multiple ribbons of same time and mounted on to string loops on either side.

Spinning:The apparatus selected for spinng is based on manufacturer’s choiceNumber of hooks on the machine to which the string loops are attached varies from 2 to 20.Spinning is done sometimes from both ends and takes place in immersed water and alkaline solution.Spinning is highly skilled operation-

Multiple of ribbons which are over spurn will tend to lack elasticity and will curl when they dry.

If they are underspun,elasticity will be too great and tensile strength will be reduced.

Angle of ply to the horizontal is the guide whether the string has been properly prepared or not. After spinning, catgut is mounted on drying frames and conditions on drying time and humidity being carefully controlled.The resulting strand of dried catgut is known as ‘RAW CATGUT’

Polishing:Aim of this step in manufacturing is-Strands of catgut will vary only slightly in diameter and need a light manner of polishing.Polishing of catgut is done by 2 methods:

1. Rotating the springs while a carriage baring an abrasive paper moves to and fro along the length.

2. By using a pair of grinding wheels and settling the wheels to the required distance apart.

These methods should be careful that the piles of strand will not damage with consequent loss in tensile strength.

Guaging:Checking the diameter of catgut is done by the guage of dial reading time. This machine gives the details of press or foot and weight loading.As the diameter of catgut will vary with relative humidity of the atmosphere, the diameter of catgut is measured at a relative humidity of 60-80% and at a temperature of 16-21oc.Normal guages of catgut used vary from finest size 1 in opthalmic work to the thickest size 7 which is occasionally used for specialist surgery.

Sterilization:Mammalian intestine in the living animal is normally relatively free of micro organisms but immediately after the death,grown of micro organism proceeds at a rapid rate.Even though the conditions of slaughter house are carefully controlled to avoid bacterial contamination,the intestine inavitably carry large bacterial population.Freezing or salting of the material inhibits further growth but doesnot kill these organisms.Streptococcus faecalis and E.coli are commonly found in the intestine but are suseptable to sterilization process.Apart from these organism spores of other organisms such as Clostidium and Bacillus anthrax contamination will be there

Spores can revert back if the conditions are favourable. Difficulty in sterilization is exacerbated by the structure of

catgut i.e, where the ribbons twisted together will carry

contamination throughout the cross section.As a result micro organisms are located in the center and are insulated. Keeping these trouble in the aspect of microbial contamination of catgut,sterilization of catgut is necessary and should be done by different ways such as chemical,heat and radiation.

Sterilization of Catgut:The aim of sterilisation of catgut is to sterilize catgut without damage in physical characteristics such as tensile strength and absorbability.The sterilization should interfere as little as possible with inherent structural advantages of collagen is a strong,flexible and elastic fibre that will be absorbing by the body in a surgical acceptable manner.

Chemical Sterilization:The chemical used in the sterilization must be sporicidal.Most of the organic and inorganic compounds are not sporicidal and the available sporicidal agents are very few.The sporicidal chemical agents used for sterilization of catgut are:

o Formaldehydeo H2o2o Hypochlorideo Gluteraldehydeo Ethyl iodideo Methyl bromideo Iodineo Ethyl oxide ando Beta-propiolactone.

Immersion of standard catgut length wound on framer and reels in standard solution of I2,KI,KIO3.

Procedure:Catgut must absorb 12% of its own weight of iodide.After this,the catgut is transferred from the solution and excess iodine is removed by sterile solvent containing a bacteristatic.Sterile strands are then transferred to their final container to which sterile fluid (95 % iso propyl alchol) is added when the containers are sealed.

Ethyl Oxide Sterilization:Ethyl oxide is explosive gas and is usually mixed with carbondioxide and freon.The factors to be controlled during ethylene oxide sterilization are:The process is usually monitered with spore stripes of Bacillus subtilis var.nigar.Care must be taken to limit residual ethyl oxide in the catgut.Aseptic procedure must be followed for filling and sealing step to the final container.

Formaldehyde Sterilization: Although formaldehyde can destroy anthrax spores,it has several disadvantages such as –

1. Catgut will be more hardened and so its absorbtion is delayed.

2. Tensile strength of catgut is reduced.3. The sterility achieved is not complete.

H202 Sterilization:H202 can effectively sterilize catgut but result in poor quality.Sometimes it has been used to improve the colour of the catgut by treating collagen in ribbon form before spilling.

Solution of Sodium and Pottasium hypochloride:These solutions are sporicidal in acid solutions.

Disadvantages of Hypochlorides:Catgut sterilized by hypochloride solution is not suitable because:

o Penetrating power is very poor.o Catgut is underly swollen.o Catgut of poor tensile strength.

Gluteraldehyde:This solution is active in Na2Hco3 buffered solutions.It can retain its sporicidal activity for about 2 weeks only.

Iodide:It is only suitable chemical for large scale sterilization of catgut.