Fulcrum - what does this mean?

I want to write a post about the hoof's fulcrum - a term I have struggled with and still don't quite get even after my most recent hoof workshop. I want to put it into layman's terms to cement it in my mind. Hopefully I 'get it'

Google defines 'fulcrum' as:

ful·crumNoun/ˈfo͝olkrəm/

1. The point on which a lever rests or is supported.

 

So my little brain translates that as the middle of the see-saw - the point of which the see saw levers around.

How on earth does this apply to the horse's limb? (Other than when a horse steps on a big rock!).

"Fulcrum represents the relationship of the ground weight bearing foot surface with the weight bearing axis of the limb" - The Barefoot Blacksmith advanced trimming workshop booklet.


The lower limb needs to be able to absorb impact - the pastern flexes to absorb force (along with a host of other shock absorbing features in the leg). This can look quite scary - have you ever taken photos of your horse at the gallop?
 

Here you can see the down force through the pastern, absorbing the impact of the stride.

There needs to be the facility to absorb impact. However, the leg still needs to minimise the lever effect of the hoof being in front of the rest of the limb.

Red = weight bearing axis of the limb. Pink = weight bearing foot surface. Blue = pastern angle.

The weight bearing foot surface (pink) needs to be as close to the weight bearing axis of the limb (red) as possible - preferably underneath it. Above is Allie with a fairly fresh trim (maybe a week old). You can see that the red line bisects her heels, but that the weight bearing foot surface (pink) doesn't quite come close enough. Below is a photo of Allie when she is way over due for a trim (maybe at 5 or 6 weeks?). You can see that the pink line has moved forwards to the point where it is coming nowhere near the red line. The weight bearing foot surface has grown forwards so much that it has taken her out of balance.

 

 

 

Here is the full photo of the above - see how being out of balance just gives her lower fore limb a weak look? See how the pastern/hoof angle is broken forward, and how the lever forces are working against her?

Compare to this photo with a fairly fresh trim. The lower limb in front looks far more stable.

So where is the 'fulcrum'? How do I find it? What can I do with that information once I do find it?

The fulcrum can be found normally by drawing a line across the sole of the hoof at the widest point.

Easy peasy, if you have hooves that are near perfect.

Red = fulcrum. Pink lines show the edges of the weight bearing foot surface. Blue line shows that the fulcrum should be in the centre of the hoof, bisecting it in two. Half of the foot in front, half behind. Voila!

Then there are the special feet.

WTF is the fulcrum?

The widest part of this horse's foot seems to be just forward of the centre of the hoof, closer to the apex of the frog - but that can't be right as I know this horse's toe is way too long. Other landmarks are where the bars end there is often a little crack like line on either side of the frog. This can point to the fulcrum. In Archie's foot above (the special one) I can see where the fulcrum should be - the bottom red line. Where I think the fulcrum probably is, is closer to the middle red line. The top red line is another 'widest' point on this foot. This is where it gets confusing.

In a deformed foot finding the fulcrum can help you envision where the foot is meant to be. When you know where you want it to go, you can trim to encourage it.

Pink = weight bearing foot surface. Red = fulcrum. Orange is where the toe should be, relative to the fulcrum.

Ok, I think I need to digest this for a while. And I need to stop drawing lines on photos. This is getting ridiculous.

Advanced Trimming Clinic 26.08.11

I am EXHAUSTED! I took both my mares to the Barefoot Blacksmith advanced clinic today and I think I slept about 3 minutes last night as I was so nervous about hauling my skatty mares over an hour away in peak hour traffic but I shouldn't have worried, they were perfect.

For now, I'm just going to post some notes I took on my iPhone. I might write some more later once I recover from this god awful headache.


Hoof advanced notes

High level performance horses - shod vs bare - safety for rider vs what is best for hoof.

Hoof balance = biomechanical neutrality - PEDAL BONE. Normal rotation 3-5 degrees. Needs to be some rotation to allow for vertical loading. Quarter scoop for high impact. Absolute ground parallel is NOT SOUND. no where to give in back part of the foot. Hinds slightly steeper than fronts - powerhouse. For correct movement. Very important for soundness.
Sole is the landmark for pedal bone. No bone in back part of foot, totally plastic, open to deformity. Hard ground and soft ground heel length different. Capsule angle matches Pastern angle.

FULCRUM - relaShionship between the foots centre of gravityand the limbs centre of gravity. Limb gravity behind foots gravity (lines). Half foot infront of centre of gravity. 

MEDIAL LATERAL BALANCE
Horses don't have straight legs. Symmetrical is not sound. Movement brings legs closertot the midline. HORSES LAND LATERAL (outside) SIDE OF HOOF FIRST SLIGHTLY. this is normal. Medial side is steeper, takes most of the forces on landing. Guiding landmark is the sole plane for front of foot, but frog is best anatomical guide to balance the back of the foot. Hind feet when resting lateral side of hoof on ground is loaded and medial mostly unloaded. Balance according to frog. 

GRAZING STANCE
Front legs all over the place. Horses are meant to be browsing off low shrubs, NOT the ground. Have to spread their feet wider to reach grass. Habitual grazing patterns need to be taken into account.

The best balanced feet are on the horse that moves the most!

The direction of the frog is where the pedal bone points.

1.5 cm sole thickness minimal for hack size horse. 

Bullnose = top much toe on!! Negative pedal bone angle leads to bull nosing.

Club foot - be carefull with how you take away heel - instead concentrate on bringing back breakover - the toe. Match the dorsal wall (front of the foot) to the pedal bone. Laser tips on a club foot works well to help soundness. Grazing stance unloads the club foot and tightens up the flexor tendon. Tight flexor tendon = pulling on the back of the pedal bone which leads to club foot.

Keep the toe backed up on the hinds.

PIGEON TOES
lands opposite - medial side first I.e. Lateral side takes the brunt of the force. Leads to ring bone and side bone. Medial side is built to take more force but not the lateral side. 

Dealing with lat/med balance. Concentrate on the lateral side keeping it short on fronts. Opposite on the hinds.

Toe first landings lead eventually to navicular. :(



That's it! TTFN!

Archie 6.08.11

Archie's previous trim.

Third Archie trim - he was one week overdue because I had a bad injury to my finger two days before he was due where the pad of my left ring finger was ripped off by a broken broom handle. Stupid injury. It has only prevented me from doing the things I love (i.e. trim and ride) but I still have to go to work and pack the dish washer.

So, Archie (and Remy and Bertha) were late. Harumph.

Archie was suffering from thrush again poor thing. Apparently he has not been sore this time though. He went out on a trail ride sans boots and was fine. I would still recommend booting up for every ride though at this stage.

Near fore

This was the last hoof I trimmed - I was pooped, and I know you are not supposed to sit on a crate to trim and that it is very dangerous, but I just wasn't strong enough. He was a total raging beast about being trimmed too.

rawr

See what happens when you don't trim for three weeks? You loose it.


ANYWAY

 Moving on... as always, pre trim on left, post on right, click to enlarge.

Thrushy crumbly yucky sole. HEAPS of flappy frog on all four, harbouring thrush. Central sulcus widening. Black hole from old abcess getting smaller. Should be gone next trim.

Big bevel, quarter scoop, bring breakover at toe back, heels lowered but not by much due to weak frogs.

Sorry about the angle difference. Heels no lower than the frog (i.e. frogs in passive contact with ground when hoof weigh bearing). Central sulcus still deep, but opening.

Heel comparison to set up trim. They look weaker sadly.

Near hind

Weird massive bars popped up, but flicked out very easily. The question is, did they pop put just due to thrush or did the foot really not need them anymore? They will grow back if they were needed. Removed crappy thrushy flaky sole and frog, then bevel all around.

Didn't take the heels down too much. Needs more sole depth.

Mainly heel and wall height removed from this angle.

Comparison to set up trim - a very different foot! The outside (left in the pic) bar is larger in both pics. Maybe to give support due to his many issue from his injury?

It is midnight now, I shall update with the other two feet's pictures soon. :)