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Archive for the ‘General surgical instruments’ Category

General surgical instruments.

 

If you can get your hands on old surgical instrument catalogues, they are a great reference aid, this one is from a company called Allan and Hanburys a company formed in the UK in 1715.

It has 651 pages of beautifully illustrated drawings of instruments and other medical items.

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It is difficult to say much about the maintenance of general surgical instruments, the reason is that the number of different instruments that you could have sent to you is huge, and many of them very specialised it would take books and books to describe how to look after them all even if I had the experience of them all, which I have not.
All that you can do is look at each instrument as you get it, firstly read what the complaint is, if there is no fault given ask the person who sent it, then if you have not seen the instrument before or are not sure about what the instrument does and how it does it, look at it closely and try to work out what it should do and how it does it, once again if you are not sure do not be afraid to ask the users, having done this, see why it isn’t doing it, this will lead you to the cause of the fault, all you have to do now is repair it.
When you think that you have completed the repair check it, take it back to the person who sent it and see if they are happy with it.
As I said at the start, one thing that is very handy to have in the workshop when you are doing this sort of repair is a surgical instrument catalogue, sometimes firms will send you one if you ask, otherwise you can often get old ones that are no longer required in the theatre.
With one of these catalogues you can find what an instrument is called, which is always good to know, it makes you more knowledgeable about the job.
Knowing what speciality the instrument is used for can sometimes help you to decide how it should work and therefore how to repair it.
Sometimes having a picture of the instrument in front of you will tell you a lot about how it should look when you have completed the repair.
Proper handling of instruments is of the utmost importance.
Mishandling causes damage to the cutting edges of cutting instruments so that it takes a lot of work to replace the sharp edge.
Cutting instruments that have a nick or dent in the cutting edge need a lot of metal removed to get rid of it, this will shorten the life span of the instrument as well as taking a long time.
Sharpening a cutting instrument usually requires the removal of metal from a bevelled surface.

In general terms you need not try to copy exactly the existing bevel on any instrument. It really is not that important.

Obviously you need to try to stay as close as you can to the original bevel.
It is difficult if not impossible to copy a hollow ground bevel on a long knife, and it can be difficult to copy many other bevels exactly, but it is not difficult to sharpen an edge.
Always make sure that the edge is in contact with the sharpening stone along the entire length of the cutting edge.

Serrated blades hold their cutting ability long after a straight edged blade will go dull, however they are much more difficult to sharpen. A flat stone or steel will grind off your serrations therefore use a tapered or cylindrical fine diamond steel or ceramic for this job. Each separate serration much be sharpened individually.

Serrated blades have a grind on one side of the blade. Only sharpen the grind side of the blade. Hold the sharpener at the angle that matches the original edge angle. Hold the knife with the edge away from you and the serrated side of the edge facing up. Set the tapered diamond sharpener in a serration so that you fill the indentation. Draw the sharpener towards the edge.

The goal in sharpening a serration is to maintain the ramp of the serration right to the edge. You do not want to create an edge bevel. Therefore we once again recommend the trusty felt pen trick. Paint the serration to be sharpened and follow your process. Evaluate if you are removing all the black. It should not take more than 5-8 strokes to resharpen if your angle was correct. Rotate or spin the sharpener as you go for the most even, consistent sharpening.

Recreating the “Initial Sharpness” on a serrated knife is difficult even if you use a tapered sharpener. But you can expect to get a “serviceable” edge. A serrated blade is more easily distorted through sharpening than a straight blade edge. So, don’t sharpen unless dull spots are truly visible.

Some specific repairs.

Scissors.
Most problems you find with scissors are that people complain that they are blunt, most often you will find that all the problem is that the joint is loose, on a box joint pair you can carefully hammer the joint, I say carefully as if you do it too much you will over tighten it, with an x screw joint, try to tighten the screw till it feels right, then hammer over the thread protruding at the back, once again don’t get carried away with the hammer.
If you do find that you have over tightened the joint, get some liquid metal polish, or very fine grinding powder in oil and pour some onto the instrument at the joint and the work the joint to and for a while, this should free up the joint, make sure that you clean out the joint afterwards.
The two important surfaces of the scissors are the inner facial surface and the working bevel.
The intersection of these two surfaces forms the shearing edge.
The bevel on the outside is called the decorative bevel and as the name suggests is merely decoration.
Look at the cutting edges, and feel them, there should be a nice clean edge not rounded.
If you think that the edge is rounded you will have to take an oil stone and rub it nearly square, so that the thin edge is at an angle of between 2 and 5 degrees from a right angle with the long side of the blade, if you see what I mean. see Fig 1000 for a clearer idea of what I as saying.
This job can be done on a revolving grind stone, but take great care that you don’t overheat the blade, try to pass the blade across the stone in one movement so that you only get one good face and not lots of different angles on the blade.
Do it with a light touch otherwise you will grind too much off and shorten the life of the scissors.
When you have been using the grind stone you will notice that there is a burr on the inside of the blade, do not close up the blades till you have got rid of this otherwise you will score the inside face of the blades and you will then have a difficult job getting them to cut smoothly again.
Take a piece of tool steel, that is a piece of steel that is used as a lathe tool, and rub it carefully down the inside of each blade making sure that you keep it flat against the blade. Tool steel is the best for the job but a small sharpening stone will do if that’s all you have.
When you can feel that the burr has gone gently close up the scissors to check that they close smoothly.
Some scissors have serrations on the edges of the blades, these will be lost after the scissors have been re-ground.
Put them back on again, this is how it is done;
Hold the scissors in a vice with one of the blades open and the edge that you need the serration’s on facing upwards, take a 6-inch file and run it across the edge allowing the teeth of the file to find their own path, by doing this you will re-cut the serrations.
Before you try it on a pair of scissors practice on a scrapped off pair or an old piece of steel.
NOTE>>>>>>>It is important that you do not grind anything off the inside edge of a pair of scissors.
The other problem that you may come across is that after awhile the tips no longer meet because the blades have been sharpened so much.
There are two possible cures for this,

a. To file a little off the handles or near the joint or both, whichever is preventing the tips meeting.

b. The second often works well but there is a risk of breaking the scissors in doing it.
For this you need a vice and a medium sized screwdriver.
Open the scissors and put the shaft of the screwdriver between the handles of the scissors up near to the joint.
Open the vice so that the tips and the first inch or so will fit in,
now holding the scissors and the screwdriver in one hand and keeping them straight, close up the vice just a little.
This is where the scissors will snap at the joint if you put too much strain on the vice.
Work the vice by closing the jaws just enough until you feel the strain on the blades, open the vice to let off the strain then close the jaws a little further till you feel the strain, go on like this for a while taking out the scissors every now and again to check if the tips now meet.
TAKE CARE. tighten the jaws too much and you WILL break the scissors.
Make sure that there are no burrs left behind after you have finished. It may be that the blades are misaligned, but this is usually obvious when you look at them, this is VERY CAREFULLY put right by bending in a vice.
The steel on a good pair of scissors will be quite hard so being too heavy handed can snap the blade off.
If you have a polishing wheel it is nice to polish the instrument after a repair, it won’t make them work any better but they will look good.
The test for a good sharp pair of scissors is that they will cut wet tissue paper without tearing or an old surgical rubber glove.

Forceps.
There are a lot of different types of forceps, they are used for gripping, pulling, dissecting and many other things, it is important that they grip well along the whole length of the jaws, and that if they have serration’s on them that they are in good shape.
With the type that are held like a pair of scissors, a common complaint is that they are loose, tightening them is the same procedure as for tightening a pair of scissors.
Some forceps, and for that matter scissors, have tungsten carbide inserts in them to make them last longer, they shouldn’t (as scissors) need sharpening that often, but when you do you should use a green grit grinding wheel.
Remember one thing, tungsten carbide is very brittle, do not try to bend it as you would a steel instrument.
You are able to get new inserts from some places, but on the whole you will find this difficult, however if you do the old ones can be taken out with oxyacetylene heat, and the new ones silver brazed in.
The type of forceps that is held between the fingers, some of which are called dissecting forceps, some times come to you with the complaint that they are crossing over, what they mean is the tips slip across each other when the user tries to grip something, the reason for this is often that the surgeon or who ever is using them is either not holding them properly or that he is using a pair that is too small for the job, sometimes it is the fault of the instrument but you can quickly see this by bringing the two tips together, they should meet absolutely together and flat against each other, if one of the tips is twisted or is bent and not lined up correctly then they will cross over, careful bending with your fingers, with a pair of pliers or in a vice will cure that. If there is nothing wrong with the forceps, you have two options.

a. Tell the surgeon that there is nothing wrong with them, and give him a demonstration of how they should be used or advise him to use a different pair.

b. fit an anti-cross over pin.
On the whole plan B may be the easier, most surgeons do not take kindly to instruction from a technician, though skilfully and tactfully done you may get away with it.
Should you decide not to lecture the surgeon here is how to fit an anti-cross over pin.
This is a pin that you put inside one side of the forceps then goes through a hole in the other side and when the forceps are closed stops it crossing over.
a. Select a point on the forceps where the finger grips are, and at the mid-point put a small mark, this is where the pin will go.

b. Now find yourself a small round piece of stainless steel, about 10 mm. long and about 1 mm. in diameter.

c. File or grind a taper on to it but leave the end rounded, clean it up to get rid of all the grinding or file marks, and lastly polish it.

d. Drill a hole at the previously selected point that is just large enough so that the pin will be a good tight fit in it. Countersink the hole on the outside.

e. Tap the pin into place, make it long enough so that when the forceps are closed the pin will just go through the other side. The tapered end of the pin should be on the inside.

f. When you are happy with the length, cut off the excess and file it flush with the body of the forceps.
If you have the equipment you should now silver braze the pin in to place on the outside so that the braze flow neatly into the countersink you made earlier. It is quite important that you do this, even if your pin is a very tight fit there is the risk that it could fall out inside a patient, surgeons are not very keen on this as it means that they should open the patient up again and look for it.

g. Now drill the hole in the other side of the forceps so that the pin will go through it when it is closed up. Remove any sharp edges and polish the whole instrument.

h. Test the operation of your new pin, make sure that it does not bind in the hole if it does your hole is either not quite in the right place or not quite large enough.

i. Make sure that the pin is not sticking out to far and is not sharp.
The surgeon will not be pleased if your new pin punctures his gloves during the operations.
Instruments such as forceps some times crack at the joints, for there is a good deal of strain at this point, the complaint will be that they are not holding, it is possible to silver solder them at the crack if you are very careful, the trouble is that the soldered joint is never really strong and might crack again at the wrong moment, so unless you HAVE to its better not to try and do it.

Chisels.
You can see a dull edge on a chisel. If you hold an instrument with light shining directly upon it and then rotate it slightly with the edge towards you, a dull edge will reflect light but a sharp one will not.
You want to remove any dullness or roundness from the cutting edge of the instrument.
This should be done by removing the least amount of metal without overheating the metal and loosing its temper.
Orthopaedic chisels, unlike carpentry chisels, are made of a very soft steel and will need sharpening quite frequently.
This is done with a normal stone of the kind that a carpenter would use.
There are two bevels or angles on a chisel, the first is the main one that you can see this is called the ground angle and should be about 25 degrees, or some say it should have a length of 2.5 times the thickness of the chisel.
The second angle is called the honed angle and should be about 30 degrees,

The ground angle can be done on a revolving grindstone and should only occasionally need re-doing. The honed angle is done on an oilstone to give you the razor sharp edge, I like to do this on a black Arkansas stone then you get a really good edge. How and when to re-grind.
When a blade becomes chipped or curved from a lot of use you will have to re-grind it; that is the blade is squared up and the angle of 25 degrees put back on to it.
First check with a square or by eye that the cutting edge is at right angles to the sides. If it is not or if it is chipped grind it square either on the power grinder or on an oilstone, do it very gently so as not to grind too much away.
To restore the ground angle of 25 degrees, rest the chisel on tool rest and touch it gently on the wheel.
Do not let the blade over heat-keep it cool by frequently dipping it in water, and if you hold it with your finger near the end you will feel it getting hot.
If the edge turns blue then it is to hot and will have lost its temper, grind that part off and start again because you will never get a good edge on it.
If you do all this on an oilstone then you will avoid the problem of over heating.
Check that the length of the ground edge is 2.5 times the thickness of the chisel.
Continue this until you are right down to the end of the chisel, and there is the smallest amount of square showing on the end, and of an even thickness all the way along. Try to make this square part left on the end as small as possible without loosing it altogether.
You are now ready to put on the final honed bevel of 30 degrees onto the chisel.
Oil your stone, then hold the blade at about 30 degrees to the stone, then draw it back towards you in one smooth movement, keeping the pressure even. Look at the end and you should see a neat 30 degree bevel, test the edge on your thumb, you may have to rub the back of the chisel, if you do you MUST keep it absolutely flat to the stone.
You may have to repeat this once or twice to get it really sharp but with practice once should be enough.
The above text applies to the ordinary flat chisel, you will come across the gouge, that is a chisel with a rounded blade. These are more difficult to sharpen.
First of all you need a small round stone, that is one which is of a smaller diameter than the gouge, and the ordinary flat sharpening stone.
Start by making sure that the end of the gouge is square to the length, once you have got this right you can start to sharpen it.
Start with a little oil on the large flat stone, then begin to move the chisel in a figure of eight motion, rolling the chisel to and fro across its width, keeping the chisel at the same angle as the bevel that is already on it, it is rather difficult to describe but there is a drawing, fig 99, that might make things a little easier to understand.
Continue to do this till the chisel is sharp, the bevel on a gouge is much steeper than an ordinary chisel and as a result you will probably not get it quite as sharp.
Use the round stone, with a little oil on it, to make sure that the inside curve of the gouge is quite flat, but the stone MUST be kept absolutely flat against the gouge on no account must you put any angle on it.
When you have got you chisel or gouge sharp, give it a good polish on a powered buffing wheel, do not polish the very end that you have just made razor sharp as you will probably blunt it, not that polishing it will make it any sharper but it does look good.

Retractors.
These are instruments used to hold parts of the body open so that the surgeon can work inside without obstruction.
Quite often they will have a ratchet on them so that they can be opened to a set position and will remain open and holding till the surgeon has finished, now because when people operate the ratchet they allow the spring-loaded lock to drag across the teeth of the ratchet, the teeth become blunt and this allows the retractor to close at the wrong moment, this closing of the retractor at the wrong moment is guaranteed to make the surgeon cross, quite rightly so because it could cause him to do something that he didn’t want to.
When this has happened you will be sent the instrument along with a note saying that it’s not holding.
What you have to do is to very carefully re-sharpen the teeth of both the fixed ratchet and the spring-loaded one.
Sometimes you can undo a thumbscrew and dismantle it all, if you can then do this as it makes the sharpening so much easier.
Put the main part of the instrument in a vice that is fitted with soft jaws so that you do not damage the instrument, take a fine needle file and very carefully file the teeth till they look good, do not take too much off.
Remove it from the vice and fit the free part of the ratchet in its place. File this in this same way, once again file very carefully and do not take too much off, this is because the teeth have to be able to mesh together correctly when re-fitted, obviously if one side has huge teeth and the other fine delicate ones the ratchet will never work as it should.
Once you are happy with the teeth on both sides, re-assemble the instrument and test it.
There is one other reason why the ratchet won’t hold other than having worn teeth, and that is because the leaf spring that tensions the free half of the ratchet is loose, missing or broken.
If it is loose then tighten the screw, if this doesn’t help remove the leaf, put it in the vice and gently bend it, this should do the trick.
If the leaf is broken or missing, you will have to replace it with another one, the chances are that you may have difficulty in buying a suitable piece off stainless steel of the right thickness and size, if you can then you can make one, if not look around for an old instrument with the same sort of spring, one that has been scrapped off and use that.

Surgical Saws.
The surgical saw, just like a carpenters saw, will need re-sharpening from time to time, this is how to do it.
To do it you will need a triangular file, a small fine one, two pieces of long flat wood and a vice, you may also need a saw set more of this later.
If you are not sure of the angle of your triangular file or you do not have one but only a flat file then do each side separately to get the angle between the teeth, as described below.
If you have the correct file it will be made at an angle of 30 degrees, this is the angle that there should be between the teeth.
Before you start look at the teeth of the saw closely, look to see if they are all the same height, look at the angle to which they have been sharpened, look to see if any teeth are missing and lastly look to see if the teeth are set. This last item, the set, can be seen by looking down on to the saw with the teeth facing you, if they are set you will see the first tooth bent over a little one way, the next tooth bent the other way and so on down the length of the saw, the angle that they are bent over to depends upon the size of the saw.
Some saws, particularly small ones often have no set.

The object is to file the teeth to the correct angle and to a sharp point.
To sharpen a saw proceed as follows;

a. Support the saw in a vice with the wood strip on each side, it must be held firmly along its whole length.
You will have to shape the wood so that it fits around the handle.
Leave the teeth just sticking up from the wood.

b. If the height of the teeth are all different, test this by putting a straight edge along the teeth, to saw will have to be `topped’, that is all the teeth made the same height.
If teeth are missing there is nothing that you can do.
Take a file and carefully file the teeth so that they are all the same height. Take as little metal off as you can.

c. Look at the teeth very closely and decide on the angle that you are going to file to.
For a carpenters rip saw, the file is held horizontally and at right angles to the length of the blade, for a cross-cut, tenon or dovetail saw the file is held horizontally and at about 60 degrees to the length of the blade.
Start filing from the handle end on the first tooth that is bent away from you.
Use the original sharpening angle as a guide and stroke the tooth two or three times with the file.
The tooth is sharp when it gleams right up to the point.
Move on to the next tooth but one, that is miss a tooth.
Continue along the length of the blade sharpening every tooth that is set away from you.
Reverse the saw and repeat the process on the other teeth.
Stop filing as soon as the tooth is sharp, otherwise you will take too much metal off.

d. The next stage is setting the teeth, this you will not have to do if the saw was not set to start with.
For this you will need a tool called a saw set, they look a little like a pair of pliers, with an adjustment that sets the anvil and a setting pin that moves with the handle.
The adjustment is made according to how many teeth per inch the saw has.
If you do not have a saw set and cannot buy one you will have to do it another way.
This is something that I have never had to do so I’m inventing it as I go along.

e. Fix the saw higher up in the wooden blocks than you had it before.
If you have the set, adjust it to the number of teeth per inch or some may be graduated in teeth per millimetre.
Set every alternate tooth, then reverse the saw and do the others.
The saw set is used like a pair of pliers, fitting over the tooth which is to be set, and squeezing the handles.

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