Case: External fixation rather than a cast to stabilise a pup’s tibial fracture
12th October 2018
Dressings / casts / splints often seem like a really good, economic, minimally invasive and simple way to immobilise fractures, but there are some issues relating to casts or splints that make them less than ideal:
No dressing / splint / cast is ever going to fix an injury as rigidly as a rigid metallic fixation construct, whether that be a plate, fixator etc. The small movements that are still allowed within a dressing / splint / cast will have consequences:
There will be more discomfort because of movement at the injury site.
Inadequate immobilisation may lead to less satisfactory healing or healing failure. Movement at a fracture site may well stop bone union from occurring and may result in much larger bone callus forming.
For a dressing to work to immobilise a fracture, the joint above and below the injury must be immobilised. This means that injuries near or above the elbow or the stifle simply can’t be effectively immobilised with a dressing.
Even for injuries below the elbow and stifle, the immobilisation of adjacent joints by a dressing / splint / cast can lead to adverse consequences – joints don’t “like” to be immobilised and loss of range of motion and muscle loss often accompanies dressings / splints/casts that are maintained for significant lengths of time.
Fractures are usually painful, and to get effective dressing / splint / cast changes done, repeated sedation or even anaesthetics may be required. This can significantly increase costs and also the impact on the patient.
In growing dogs, the limb can outgrow the dressing in a matter of days, and frequent dressing changes are required.
Sores can develop under dressings, especially over pressure points like the ankle. Sometimes the way the dressing is put on can make these sores more likely, but all vets and nurses who put on dressings on regularly will get the odd dressing related sore. These sores usually clear up really well once the dressing is removed, but if the dressing has failed to solve the problem and a “plan B” of internal fixation is required, it is far from ideal to be creating surgical wounds through inflamed skin. The risk of infection developing after the revision surgery would then be significantly increased.
If dressings get wet or slip they make things worse, not better:
Wet dressings lead to skin sores (imagine what a baby’s bottom would look like if it was left in the same wet nappy for a day …)
Slipped dressings are now no longer protecting the injury, and in fact are effectively lengthening the limb, increasing the forces acting on the injury.
A four month old pup suffered a broken tibia around a farm. There were no soft tissue wounds and the fracture was a “green-stick” injury, meaning that the ends of the bones weren’t significantly displaced., The fracture could have done well in a cast or a splint, but the owners decided that they preferred the idea of an external fixator:
Rigid fixation, giving a “near certain” chance of excellent bone healing
No joint immobilisation
No repeat dressing changes / sedations required
Application of the external fixator under a single general anesthetic. Because the fracture wasn’t displaced we didn’t need to make a surgical approach to realign the bits of the broken bone. So the external fixator application was done “closed” in this case. This meant that there was no surgical wound.
Removal of the fixator can usually be done under sedation in all but the most fractious of patients.