Continued Professional Development Dissection Day 28 June 2008 atendees

Continued Professional Development Dissection Day 28 June 2008 atendees

The main speaker on this occasion was Mark Johnson, a Leicestershire based farrier with a particular interest in haemodynamics, who undertook a dissection of a horses foreleg from the knee down.

He started by inviting the twenty attendees to step up and take a good look at the limb he had selected at random for the demonstration. It was immediately obvious that the subject displayed medial lateral imbalance with one heel clearly higher than the other.

Mark has undertaken a large number of similar dissections and said he sees lots of asymetical injury due to lateral imbalance and outlined the importance of correct placing of the breakover point (effectively the ball of the horses foot) to assist preservation of the digital cushion, vital for limb support and correct function right from the moment of birth. Stimulation is the key to this preservation and a bad start in any equine will lead to compensation and eventually injury. Any twist in a limb will have ramifications of soft tissue injury. He stressed the importance of the back third of the foot, likening a good digital cushion to a 'six pack' and a bad one to a beer belly, which struck a note with some of those present! Mark put forward the theory that a horse that is toe landing may be trying to avoid pressure and pain at the back of the foot.

As the dissection got underway it was immediately clear just how devastating the results of such imbalance are on the internal structures of the horses foot and leg:

The first stage was to remove the back of the heels, which clearly displayed loss of blood flow (de-vascularisation) of the digital cushion, although some function remained around the edges. He then cut through the junction of the wall and sole and it was immediately obvious how much more blood supply there was at the same depth on the functional side of the foot.

De-vascularisation of the digital cushion

De-vascularisation of the digital cushion

When the sole was removed a dramatic lack of thickness was obvious on the non-functioning side.

Lack of thickness on the non-functioning side

Lack of thickness on the non-functioning side

The most interesting and shocking effect of the imbalance was displayed when the outer wall was removed, revealing a clear half-moon shaped keratoma at the tip of the toe, a corresponding indentation in the pedal bone and distinct strangulation of the coronary band.

Half-moon shaped keratoma at the tip of the toe

Half-moon shaped keratoma at the tip of the toe

The second half of the process saw the skinning of the limb to reveal the stay apparatus. By applying tension to the superficial and deep digital flexor tendons Mark was able to clearly demonstrate how each affects the movement of the foot.

Large amounts of trauma to the fetlock were apparent, especially a long tear in the deep digital flexor tendon which veered off to the damaged side and very possibly due to the twist in the limb.

Fetlock Trauma

Fetlock Trauma

He then moved on to show the check ligament, which again showed signs of trauma. Mark explained how the imbalance in this particular horse was such that it would not have been able to get its feet under its withers as the toes were too long, and therefore would not have been able to lock out the check ligament. This would have resulted in the horse not being able to sleep properly, having difficulty standing and moving, which would ultimately have affected the breathing and digestion. The check ligament acts like a fuse, and often "blows" before too much damage is done to the deep digital flexor tendon.

Further investigation showed lots of legions and adhesions at the base of the deep digital flexor tendon, and cutting through the navicular bursar revealed pockets of inflammation around the navicular bone.

There was also damage to the lower branches of the suspensory ligament, which is often seen more prominent on one side when there is a lateral imbalance, and sesamoiditis as well as ossified lateral cartidges! On closer inspection, Emma Mitchell of Lingfield vets also suspected the horse had suffered from growth plate issues at a young age.

We are sure that all those attending extend a huge thank you to Mark for taking the time out of his busy schedule to give us what was a fascinating demonstration into the results of a condition which is seen all too often and is preventable given correct foot balancing when trimming and shoeing.

Clive Meers Rainger RSS Bll CNBF CLS