Healing- primary intention

The aim of stitches after a surgery is to allow the wound to heal by primary or first intention. I promise that was written in English. Keep reading for the explanation of what this means. We have not been having too much fun here at Primal Paws. We have two very excitable, high drive Kelpies who are on strict rest after their recent desexing procedure. We chose to primarily limit them to a small 3.5x3.5meter room with short toilet breaks, and to crate them when we can't supervise them. This was to balance allowing them to move and weight bear naturally to limit de-conditioning due to confinement while minimising the pressures placed on the wound site. This balancing act is important to facilitate quick and strong healing of the abdominal wound and limit the risk of complications.

So why is keeping them quiet so important?

All wounds go through an initial stage of inflammation regardless of how they occur, through a surgical cut, bite or scratch. What happens after this determines how quickly the area will heal. This stage will continue until all contaminants are removed. As you can imagine a surgical cut will have the shortest and smallest inflammatory reaction. Inflammation is not the enemy, however if it is excessive, or lasts for a prolonged period of time it can lead to a chronic, slow or non-healing wound.

The stitches placed in the different layers of the abdomen are designed to bring each layer into close contact with its matching counterpart on the other side. This allows the tissues to connect without the need to fill in the gaps which logically takes much longer. For the first three days the stitches provide all the strength holding the wound together.

Epithelial cells that cover the surface of the skin can begin migrating to form a weak connection across the wound. They can travel 0.4-1mm/day which is why sutures holding the cut surface in close contact with like tissues is so much faster than an open wound.

Cells will be moving into the area, laying down a base for skin cells to cover the wound area. Concurrently, new blood supply will be established to provide nourishment to the area. The collagen fibres that these cells produce provide the area with the first significant strength holding structure to bridge the gap by the body. The fibres are not organised and not as strong as the fibres that are typically found in normal skin. This area is still prone to damage if significant forces are placed on the area, which could return the wound to a primarily inflammatory state, delaying healing.

This disorganised matrix of fibres continues to be created for the next 2-4 weeks. It is between the first and second week there is the greatest increase in strength from 0 up to 20% of the original tissue strength. It takes a further 4-6 weeks before it reaches 50% of the tissue strength it had prior to surgery.

Finally the body can focus on replacing this disorganised matrix to a more regular, organised matrix of fibres which can take up to a year to reach a maximum final strength of 80% of the original skin.

In a nutshell we need to keep animals quiet after surgery to allow the least amount of disruption to the wound site to allow the body to get on with its job. Constant explosive movements disrupt the disorganised matrix and the epithelial cells, slowing down the process.

In Jem's case she had a cyst removed from her neck. The high degree of movement on the neck slowed the healing process as the disorganised matrix kept being disturbed.  Unfortunately a few good (sneaky) scratches opened up her wound within minutes of taking out the stitches. We decided to let it heal by second intention - which of course will be another blog for another day!

Dr Jaime Jackson