Podiatry Surgical Instrument Manufacture
Steel Surgical Instruments
There are over 400 types of stainless steel. Stainless steel is an alloy and is man-made.
Most surgical instruments are made from 4/20 (four twenty) grade stainless, its salient characteristics are its 14% chromium content which gives it its “stainless” properties. 4/20 is magnetic, due to its iron content which can of course rust.
A process called passivation (a nitric acid mix) is used to etch away the surface iron molecules, until the chromium molecules arrive at the surface. This ultra thin layer of chromium prevents moisture coming into contact with the iron molecules – prevents surface rusting – this is also why you should not engrave instruments. This would break the passivated layer, therefore causing rusting at the engraving site.
4/20- steel is also capable of “self-healing”. Where the passivated surface is damaged, rusting occurs until the chromium molecules are exposed. Joints are more likely to produce rust deposits since the joint action wears away the passivated layers especially if not lubricated. The passivation treatment is also less likely to deeply penetrate the joint crevasses.
By adding more chromium we can increase the resistance to rust and staining. However higher chromium content stainless such as 3/16 (three one six) is much softer and is useless for cutting edges. (You can demonstrate the inability of the tubegauze applicator to return when bent). 3/16 also has little or no memory
Due to its softness. 3/16 has a chromium content of 22% and is non-magnetic.
Equally, we can use less chromium to achieve greater hardness. 4/20 can be hardened to around 45-48 Rockwell C. We use a 6% chromium steel to make orthotic scissors (CH70) which have to cut tough plastics and polypropylene. These can reach over 55 Rockwell C, but do not autoclave them, or leave them wet. They have some resistance, but not enough chromium molecules to cover the surface.
Surgical Instrument Forging
There are 3 methods: Hot forging, Cold forging and casting.
Cold forging is good for plastic handled kitchen scissors where the blades are usually 2 to 2.5mm thick. Anything thicker than this and monumental force needs to be applied. A nipper handle would need 250-300 tons of force applied to cold steel, but only 20-30 tons in hot steel. Apart from the energy wastage, cold forging sets up minute stress fractures when used on thicker sections of steel. These are impossible to passivate and can harbour dirt and bacteria.
Generally, cold forging is a poor alternative for surgical instruments and is not used. Cold forging is however, good for softer steels (3/16) in making and pressing gallipots, bowls etc.
Casting, again, is not generally used in that the molecular structure tends to be brittle, and damage can occur by dropping onto a hard surface (a floor!) casting does have one great advantage, its very accurate and very repeatable. For example, the orthotic scissors with “self-tightening” alignment joints are cast because this accuracy is needed.
So, its about selecting the correct steel, the correct hardness and the right forging process.
Standards and Validation of Instruments
Everything so far is wrapped up in British Standards No 5194 Sections 1-4 entitled “Surgical Instruments”.
Be aware of laboratory instruments which might look the same, but do not need these standards as laboratory instruments are not designed for use on humans. They are generally made of low grade stainless (6% chromium) and are unpassivated.
Many German companies CE mark as a manicure item, they are not CE marked as Class I medical devices, and in theory should not be offered as such. It is worth checking CE classification. (This is relevant to some chiropody/podiatry instruments – they are CE marked as cosmetic/manicure items).
For the past five years it has been mandatory for all surgical instrument companies to provide a validated cleaning process. That is to say, a written procedure which has been microbiologically tested to prove it works, and also a detailed risk analysis on comparative instruments. (ie it is acceptable to validate a 5” Spencer Wells and claim similarity to a 7” Spencer Wells).
Any company which cannot do this cannot claim a device is CE marked as a Class I Medical Device. It is a requirement of a Class I medical device. All podiatry instruments are Class I Medical Devices.
It is also worth noting that it is illegal to buy, sell or even give or receive free of charge a non CE marked product, or an incorrectly labelled CE marked product.
Podiatry Managers tend to assume that companies offering products are aware of the myriad of legislation and conform to it. They are wrong to assume.
PaSA, the NHS Purchasing and Supply Agency operates some rigorous qualifications before awarding companies a PaSA registration number. To our knowledge there are only two companies on PaSA for reusable surgical instruments within the known podiatry sector.
Conversion to Sterile Services Departments (SSDs)
If you consider that instrument companies selling a “reusable instrument “ have to validate a cleaning and autoclaving process to prove ''the instrument is “reusable”, then clearly the same problem arises in the clinic .You have to prove your washers, autoclaves and “trained operatives”, your whole process, is up to the task. Inevitably, converting to SSDs is the easier option. The SSDs already have this validation, and are experts. Podiatrists are experts in feet, not decontamination.
There are problems to SSD conversion. It is a fact that staff generally do not like it, mainly because of standardisation. They can no longer reach for their favourite nipper, blacks file, probe .
Heads of Podiatry Services must not underestimate the rapid increase in Repetitive Strain Injury (RSI) that will occur, probably blamed on the new instruments.
There are historical parallels. In the 1970’s, operating theatres abandoned their Little Sisters for SSDs. The surgeons hated it, but they never went back to the Little Sisters. Similarly, syringes and needles are no longer reprocessed at all, or scalpels. In this instance, disposables took over.
Cost
Podiatrists spend a lot of time selecting instruments, especially nippers and blacks files. Interestingly, if you used a pair of nippers on 10 patients a day for 210 working days in a year, and you paid £20.00 for them (Average nipper cost), it works out at 3 pence per patient. Remember, a disposable scalpel blade costs around 7.5 pence each. It costs from £1.80 - £5.50 to process this 3 pence nipper via an SSD. Its probably, costing a podiatry department more to use a trained podiatrist to process an instrument in the clinic.
Bailey Instruments Limited is a member of the Association of British Healthcare Industries (ABHI), and sit on the Surgical Instruments Special Interest Committee.
