VETisco supply a range of external fixation pins and useful instrumentation for when placing pins, such as a range of implant cutters.

There are no hard and fast rules as to pin selection and placement but there are general rules or at least minimum requirements that should be followed. These rules should decrease the likelihood of pin loosening and loss of fixator rigidity.
- More than one pin should be place at either side of the fracture site or into each fragment and ideally a minimum of three either side/into each fragment should be the aim. Also worth noting that pin loosening will inevitably happen but the more pins in a frame, the more that can be ‘lost’ due to loosening before the strength of the frame is affected.
- Pre-drilling is recommended for pin insertion. It is recommended to pre-drill with a smaller diameter drill and then insert the pin under low power or with a hand chuck. This will reduce bone damage by either mechanical or thermal necrosis and therefore decrease the risk of pin loosening. Flushing after pre-drilling or pin insertion can also help prevent thermal necrosis of the bone which occurs when the temperature of the bone has reached 56°C for 10 seconds.
- Use a tissue protector to prevent tissue damage when pre-drilling or inserting a pin.
- Each pin should be inserted through a separate skin incision being careful to avoid large muscle masses. This will help with incision/wound management and should decrease the risk of pin tract infections.
- The closer the connecting bar is placed to the bone, the better the frame strength. Studies have shown that doubling the distance of the bone to bar results in up to 25% loss in frame strength although patient comfort must be considered with proximity of bar placement.
- Obviously the larger the diameter and number of pins and bars used, the greater the strength of the frame. The maximum diameter of pins used should be no more than a third of the bone diameter they are being inserted into.z
Pin Selection
The weakest point of an External Fixator frame is the pin-bone interface so pin selection is very important. The following looks at the different types of pins and their advantages and disadvantages.
- Smooth Pins
Smooth pins are low cost and offer greater stiffness/strength than their threaded counterparts. However they offer minimal pull out resistance and therefore can cause premature pin loosening and subsequent frame failure. Perhaps most useful in simple fractures of a young patient where healing is more likely to ‘win the race’ before pin loosening. They also may be the only choice of pin in thinner bones, e.g. cat metatarsals/metacarpals.
- Negative Threaded Pins
Basically means the threaded portion of the pin has a smaller core then the shank of the rest of the pin. Being a threaded pin it offers increased pull out resistance but the point where the threaded section meets the remainder of the pin is a known weak point and it is important that the thread of these pins engage the far cortex to ensure this weak point is protected within the medullary cavity. However it is worth noting that failure of negative threaded pins is rare and almost all pins used in human medicine are negative threaded.
- Positive Threaded Pins
The threaded portion of the pin has a greater diameter than the shank of the remainder of the pin and studies have shown that they hold the greatest pull out resistance. However this point would still be debated by some. This makes them useful if the frame will remain in place for a prolonged period of time. Probably the most widely used pins in external fixation. Positive End Threaded pins to be used where the pin will only pass through one side of the skin and Positive Mid Threaded pins where the pin is secured on both sides of the limb.

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0.9/1.1/1.25/1.4mm Wire Storage/Dispenser
£75.60

These autoclavable, cylindrical storage tubes are made from stainless steel and have four separate i.....

1.5/1.6/1.8/2.0mm Wire Storage/Dispenser
£75.60

These autoclavable, cylindrical storage tubes are made from stainless steel and have four separate i.....

Bone Pin Storage Wrap
£34.00

Bone pin storage made from a strong material to hold the pins without them penetrating through. Ver.....

Implant Cutter to 2.0mm
£110.00

A selection of implant cutters to cut all types of implants but most commonly used to cut pins to th.....

Implant Cutter to 3.0mm
£211.00

A selection of implant cutters to cut all types of implants but most commonly used to cut pins to th.....

Implant Cutter With Detachable Handles - Cuts to 4.0mm
£319.00

A selection of implant cutters to cut all types of implants but most commonly used to cut pins to th.....

Implant Cutters - Close Cut
£182.00

A selection of implant cutters to cut all types of implants but most commonly used to cut pins to th.....

Jacobs Chuck with Handle & Key
£180.00

Jacobs Chuck with handle for manual insertion of any pins and wires up to 6mm. Chuck supplied with a.....

Jacobs-Type Chuck with Handle & Key
£130.00

Jacobs Chuck with handle for manual insertion of any pins and wires up to 6mm. Chuck supplied with a.....

Kirschner Wire Box 12 Sizes
£104.50

A simple autoclavable box which when opened reveals a storage rack with 8 holes to accept 6 differen.....

Kirschner Wire Box 6 Sizes
£88.00

A simple autoclavable box which when opened reveals a storage rack with 8 holes to accept 6 differen.....