In this paper I am going to discuss my thoughts on orthopaedics and biomechanics. When we have a close look at the makeup of the hoof and its internal structures you will find that the outer hoof capsule is the main component that has the ability to change its shape, and therefore its alignment on the end of the limb. It is also the main component that the internal structures are supported from, mainly by the internal sensitive laminae.

The laminae form the connection between the hoof capsule and the distal phalanx with the digital cushion wedged in between the back half of the distal phalanx and the frog to aid in the expansion process of the hoof and absorbing the concussion of the hoof contacting with the ground. So it is paramount that these parts along with the cartilage and collateral ligaments are healthy and in correct structural alignment or they cannot perform their individual tasks.

The hoof is a very vascular system with many of the main components having their own supply of blood from arteries such as the:

• digital artery
• terminal Arch
• coronary artery
• distal phalangeal artery
• circumflex artery
• digital cushion artery
• along with branches and other small vessels off them.

If the orthopaedics of the hoof are out then the blood supply into the hoof is either compromised or changed completely. This is to say that the blood can not reach its target, and in some cases the corium of the sole and dorsal wall is deprived of blood flow and then this causes the horse pain. I believe this could also be the start of pedal osteitis as the blood flow to the distal phalanx is changed and the bone tissue begins to decay.

So the hoof needs its correct blood supply to remain healthy and maintain its correct consistency.

It is my belief that when the hoof is orthopaedically compromised the foot becomes very painful, as the blood vessels are trapped between the bones and internal tissue of the foot. As the body believes it is under attack, it sends in white blood cells to clean up the system and this engorges some parts of the hoof with blood.But as the problem is not rectified and the foot becomes so painful due to blood not reaching the targeted areas and /or that the body reduces the pain by limiting the amount of blood flow to the foot by diverting blood away through the AVA shunts.This compromised blood flow deprives the hoof tissue of much needed blood flow and the tissues begin to break down.

When the tissue in the foot begins to break down they become cartelised and cannot allow for correct blood flow or expansion and shock absorption to take place, thus the horse changes its orthopaedic stance once more. It is the reason that with a painful foot the horse changes its orthopaedic stance as to lessen the amount of pressure it places on its feet. This change of stance then changes the biomechanics and blood flow of the hoof and the upper body alignment changes as a result.

With the hoof not having correct expansion and blood flow the hoof begins to contract thus forcing the digital phalanx to move upwards and the hoof capsule becomes misaligned with it.This then places stress on all the internal parts of the foot such as the Distal cartilage (between P2 and P3 starts to tear at its insertion on the bone, digital cushion becomes cartelised and cannot perform its role, the distal cartilage places pressure on the bilateral branches of the digital artery), the sensitive laminae stretch as they try to maintain alignment, blood flow is also compromised and the end result is that the hoof capsule moves forward away from P3 and this is the start of the hoof breaking down.

With the sensitive laminae breaking down the hoof capsule moves forward and then acts as a mechanical lever placing more pressure on the heel area and corium of the sole restricting blood flow. So with the digital cushion already under pressure and with little blood flow it changes the tissue structures and starts to expand out the back of the foot giving us bulging heels.If we add to the equation a medial lateral imbalance then the hoof capsule gains more leverage on the high side. So the end result is that the hoof capsule moves around distal phalanx causing untold pressure on the internal structures of the foot as well as rotating the limb involved changing its flight action and placing the muscular - skeletal alignment under pressure.

Once the hoof capsule is misaligned with distal phalanx the bars of the foot are placed under enormous amount of pressure and through incorrect hoof biomechanics they become contracted internally.

With a contracted bar I have noticed two things:

1.That a large amount of bar tissue inside the feet only force the digital cushion upwards thus placing pressure on the deep flexor tendon and bursar.Then this forces a misalignment of distal sesamoid bone causing pain.

2.With contracted bars they cannot allow for expansion of the hoof due to the rigid state that they are in and this restricts blood flow.

So now with a hoof that is badly compromised it cannot do its job and the hoof problems along with upper body problems become worse until the horse is reluctant to move or carry weight.

So over the past 10 or more years of carrying out autopsies on feet I realised that we had to look at the pathology of the hoof to give us that insight as to what is healthy and what is not.

When trimming a foot I always keep this in mind when deciding how that individual foot should be trimmed.I look at things like:

• hoof shape and alignment
• coronet band alignment and swelling
• hoof tissue
• sole tissue
• white line colour, size and texture
• frog shape, size and texture
• digital cushion
• distal cartilage
• hoof wall and heels
• collateral ligaments of distal sesamoid insertion on P1
• each limb and its alignment as well as the flight action
• upper body changes
• bruising

This is what I call trimming to the hoof pathology and I believe it is the way to ensure correct orthopaedic stance of the horse along with correct biomechanics and in return correct muscular- skeletal alignment.