Respect the bones (Day -293)

Vet School Bones and Skeletons

Unfortunately today started badly with a me walking into a resus this morning, sadly the prognosis once an animals heart stops is very very poor. Even when we are able to get an animal back after their heart stops it is a low chance that the animal will leave the hospital alive.

However today is not about that – today is about something a lot more amazing. The bones of the body are probably one of the least understood yet most important parts of nature. There is a lot that can go wrong with bones and a lot of causes of diseases related to the bones.

Whilst there is well established procedures and techniques for dealing with things like fractures, and now even joint replacement. There is little to understanding the way bones grow.

We’ve got a new European Diplomat in Equine Surgery on staff at the vet school and today he gave a lecture looking at skeletal diseases in foals. Now when you consider that horses often have to grow to support 500kg of weight you realise just how important the skeleton is. However when growing, and in fact even during development within the womb bones develop sometimes in ways that will not be compatible with carrying that weight.

I know some of the equine surgical procedures, however I was amazed to learn that if done in the right place at the right time you can simply change the way a bone grows simply by sticking a needle into it. Whilst this is a crazy idea, it gets worse in that no one actually understands why it happens that way. Why does a needle stimulate bone to grow faster?

This is actually therapy used in foals when the leg is not straight to correct the angle the leg grows at because one side of the bone is growing faster than the other. And you would be right in thinking if we can speed up the growth on one side to fix the problem = what about slowing it down on the other side?

So to understand this you need to know that growing bones have two separate parts at every joint. There is the shaft of the bone which is the long bit, and at each end of this there is a separate part called the growth plate. Now the bone grows longer by growth between the shaft and the growth plate until the animal is mature and then these parts fuse together to form the normal end of the bone seen in adults.

Originally it was actually all about slowing down the growth on the side that grew too fast. Initially this was by using screws and wire to compress the growth plate. This worked however was not great to have things sticking out the side of the bone, so now is done using a single screw placed between the shaft of the bone and the growth plate.

Now doing this will slow down the speed of growth on that side of the bone – downside is that you need a second surgery to remove the screw. This is why it’s better to speed up growth of the other side.

This single lecture left me with so many questions… What else can we use to affect bone growth? Will laser affect it? Why does it speed up growth with needles? How do we know when this happens? Can this be used in animals other than horses?

Dehorning and holes into the skull…

Dehorning cows - a hole into the skull

Friday again, another morning spent on the farm working with the dairy herd in diseases of ruminants. With Easter so close a lot of people have travelled home and so today’s group is really small. Last time was reproduction work so today is orthopaedics and other surgery unrelated to the reproductive tract including today dehorning.

Cows are generally gentle loving animals, however their heads are one of their primary weapons, and with horns they are actually quite formidable. This endangers workers, plus also the other animals in the herd. Most of time the tissue that grows the horn is removed when they are calves so that the horns do not grow, however if there is a problem with this then the horn can still grow.

These horns are basically made keratin which is the same as your finger nails – however in cows after they reach about 2 months the horn “bud” attaches to the skull underneath and the sinus cavity inside the skull will expand into the horn as it grows. This is where the photo is from – it is the hole that is left after the horn has been removed looking into the frontal sinus.

The horn has a nerve going to it (the cornual nerve) which goes from behind the eye so before we do anything this is blocked by using procaine as a local anaesthesia which means that there is no feeling anywhere around the horn.

After the horn bud attaches to the skull at around 8 weeks only a vet is allowed to remove it – farmers can only remove the tip of the horn so that it is not sharp. Removing the tip however doesn’t remove the danger as it can cause significant bruising and damage to others. So at this stage it is still beneficial to remove the horn, this is done by a surgical wire saw and usually takes under a minute to do (the record here is apparently 17 seconds). Once the horn is removed any bleeding from the blood vessels is controlled by ligation and antibiotic spray applied to the site.

Unfortunately this is the only way to remove the horn, and there is not enough loose skin in this area to close over this so it is left open. It takes around 4 weeks for a scab to form over this opening – and then a further few weeks for it to form a proper scar.

This does not cause as many side effects as may be expected – having a patch over the hole with a bandage is generally not liked by cows and they tend to remove it within hours. And from the studies I have read having a patch does not reduce the healing time. The only recommendation here is to keep the cows that have been dehorned separate to the rest – this is good from a management point of view as it is easier to check that nothing is going on with them.

The rest of the morning went do checking on some patients post digit amputation. One of these had a large abscess higher up the leg which was removed. This lead to some bleeding and I was allowed to ligate the bleeding vessels here. Today was my first suturing ruminants and it was pretty different for me with how thick and tough the skin is so I was pleased to get the practice. However even after ligation of the main bleeding vessels there was still significant capillary bleeding and so we applied a tourniquet to the leg to reduce the blood flow and allow clot formation before we released the cow back to the herd.

We were pretty disgusting when we finished, however went straight into lectures for contagious disease… The joys of vet school.

The femoral head and neck ostectomy…

Vet student in surgery

I walked into surgery today not to fix an animal, but to stop that animal’s pain. Sometimes that is all that is possible, however personally I believe that no animal should suffer so this option is better than leaving the animal in pain.

This surgery is listed in the textbooks as a salvage procedure, a surgery of last resort when nothing else has worked or is possible. It is for the hip joint when there are such severe arthritic changes that it is just pure pain with every movement. The options with damage to this joint in mild cases is for pain management via medication, however when it gets to a severe stage the only option becomes total joint replacement.

Total hip joint replacement is an option that is very real within the UK, and within specialist referral veterinary hospitals a common procedure that takes place on a weekly basis. However this can be an expensive procedure, though if you do have pet insurance may be covered under this so it is worth checking if you have pet insurance.

When total joint replacement is not possible, then the only option when pain medication fails tends to be the femoral head and neck ostectomy. This is a surgery where the top part of the femur (the thigh bone) that forms the joint connection to the hip is removed. The movement of this bone against the socket in the hip is what usually causes the pain, so the removal of this part of the bone stops the movement and so stops the pain.

The muscles around this joint are pretty strong, and during the months after the surgery the space will be filled with new tissue and the surrounding muscles will develop more. However this surgery does mean that the animal will be permanently lame and have a limp. In some cases the leg may even appear a little shorter than the opposite leg, however there will be no pain, and the patients I have seen with this surgery have recovered well to become very active again.

This is also a different surgery in a different way, as after the surgery instead of restricting the animal to cage rest the animal should be lead walked straight away to help the development and strengthening of the muscles. The difference with patients that I have seen from before surgery and a week later has been remarkable. However I hope that one day total hip joint replacement will become affordable for every animal in every country.