11/20/2018 - Diagnosing Penn, Part 4 (Diagnosis)

**First, I want to thank everyone for their kind words and support. It really means a lot. I wish I had better news for how it all turns out, but I don't. Everything is detailed in this post. Part of why this series of posts was so drawn out is because I needed time to go through the almost 700 images from the MRI.**

Despite the bad circumstances, I am completely fascinated with the imaging from the MRI.

MRI day had finally arrived! Everything was going well until Penn absolutely refused to get on the trailer at o'dark hundred. My truck and trailer talk nicely to each other, but the borrowed truck was not speaking to my interior trailer lights. I parked the back of the trailer in a flood light hoping that would provide enough light, but Penn still tripped on the ramp, almost fell down, and then absolutely refused to get in. Mom ended up using her cell phone flashlight to light up the inside of the trailer, and then Penn happily walked on. Unfortunately, that blew the 15 min buffer window I had allowed for slow driving and we ended up leaving at 6 instead of 5:45.

Everything was smooth sailing for our drive to Morven Park, and we even arrived 10 min early! It took me all of those minutes to find someone who could direct us where to go. One of the vets from VEI met us there and helped me get Penn inside and unblanketed. She pulled his shoes (which was an oddly traumatizing event for me, the same sick sad feeling as when we pulled Mikey’s hind shoes when he was recovering in 2015), and then she put his neck catheter in.

I love that VEI’s vets are happy to talk to me and include me in what they’re doing. Doing something as simple as holding the horse so he doesn’t roll in fresh shavings with a neck catheter in was really nice and made me feel useful instead of banished. I was able to tag along for the whole pre-MRI work (but not the MRI itself, which is apparently super boring after the first 5 min, and it takes about 2.5 hours if the horse is good).

A system similar to what scanned Penn.
Check out the website (Hallmarq) that I found this image on for more info!

The standing MRI that Penn had done isn’t like a human MRI. He didn’t need to be knocked out, just heavily sedated so he didn’t move at all. It’s also not nearly as powerful- metal won’t go flying across the room. The only metal you need to remove is anything that will end up in the MRI’s field of view. We had to pull his shoes, and then the vet used x-rays to ensure we got all of the metal from the nails. Slivers won’t get pulled through the hoof, but they will create black spots that the machine can’t see through. It took about a half hour to get the slivers out of his hoof wall- only because the x-ray software wasn’t playing nice and the vet had to keep rebooting the computer between test images. Penn stood like a champ on the Plexiglas foot rest and didn’t move at all. He was just happy to get face rubs and attention.

After getting the metal out of his hooves, we took him back to the room where the equipment is located and they gave him some sedatives and said goodbye to me. They led him to the room with the MRI in it, and I went out to meet my mom and go find some breakfast!

We ended up touring Morven Park's grounds on our way to breakfast. I had only seen the barns and dressage rings, and I couldn't place where they built their new rings. We drove past the mansion, cross country course, soccer fields, before eventually ending up at the part I'm familiar with.

Uh, drool. I hope one day I get to go ride there! There's another area behind that mound that seems to be the same size.

We left Penn around 8:30 or 9 am I think, and the vet called me around 12:45 pm to say he was back in his stall and things had gone well. Penn had been very good for the left foot and left pastern, but had to pee during the right pastern. There was some clean up and they had to redo the right pastern before moving back down to the right foot. Basically, he had been a model patient and could go back to the vet office as soon as he was awake enough to travel.

So drugged, plus a muzzle. Diapers on both fronts since he doesn't have shoes.

It's a good thing we didn't plan on leaving the day of the MRI, Penn wasn't ready to go until almost 1:30 pm, and I was already tired by that point. We took Penn back to the vet office and settled in to wait for practice owner, Dr A Kent Allen, to be done with his clients and to read Penn's MRI.

One of his afternoon clients was GP Trainer with 3 of the horses from her barn, so I got to talk to her for a little bit. She was the voice of reason that I did not want to hear, but I needed to hear. She said that maybe my time with him is up- he is a wonderful creature but served his purpose for me (my bronze) and it's time to find him another job. She told me to do what's best for him, but do not go overboard and do everything both reasonable and unreasonable. Basically, weigh the treatment against how well it works and how much it costs. Come up with a limit of what we'll spend to fix him, and stick to it. She said every now and then she gets emails from clients about older schoolmaster type horses that their owners want to free lease to keep them exercised or to get them off their checkbooks. She could help me get set up with one of those to continue my education. She did apologize for "being an emotionless bitch about it" (her words, haha), but she's absolutely right and that is the voice I need to have on my side. I didn't have it when I bought him. I don't regret buying him, but I believe some of his issues were glossed over or ignored because Mikey had just died and the thinking was "Oh, Jan found a horse she likes, just approve him!"

Anyway...

It took quite a while to get the results back, but that's fine. Dr Allen was very thorough and there's no rushing it. It was well after their closing hours by the time he came to talk about it, but he spent the time with me to make sure I understood what was wrong and pointed everything out on the MRI images, which I've shared below. (I may have gotten the images wrong, or pointed to the wrong place, sorry! I had to find them myself after the fact and it took me a very long time. I am 95% sure of everything though.)

Penn has moderate tears in two collateral ligaments- one in each front hoof, both next to the coffin bone. The medial on the RF and the lateral on the LF, so the left side of each front foot.

PC: http://www.backpunch.com/the-navicular-apparatus/
The arrows are a bit difficult to see, but it's the forward-most green ligament.

To understand all that's wrong with his feet, you need this too. I pulled this image from Google, then added the P1, P2, P3 to it. I didn't know the names of these or the order or anything before any of Penn's issues this year, so I'll list a couple things for anyone who is unsure:
P1: Long pastern bone
P2: Short pastern bone
P3: Coffin bone, pedal bone

In addition to the torn collateral ligaments, his navicular area is a bit messy in both fronts, enough that it bothered the vet quite a bit. He was also concerned about the coffin joint in both fronts. It's just easier to do a screenshot of the MRI findings and diagnosis that Dr Allen gave me:

From my very non-vet perspective, it sounds like Penn should be a cripple for life.
I wonder how many 'sound' horses have some of these issues?

For help reading the following MRI images, look in these places:
     http://www.hallmarq.net/equine/veterinarians
     http://casemed.case.edu/clerkships/neurology/web%20neurorad/mri%20basics.htm
     https://www.chirogeek.com/MRI%20READING/mriReading.html#Axial_Images

I found it helpful to know how each type of sequencing displays the different tissues, and some other basics. Austen found the bottom two articles, the second of which was quick to point out that the label L in the MRI images does not mean lateral, it means left. The images are flipped- what's on the right is actually on the left side of the scanned area. I'm not sure what the F, FP, FA, P, PF and all the other orientation letters mean, but knowing what foot and which side is left makes all the difference. Basically, throw out your medial and lateral references that we've been using! We're looking at the left side of each foot, not lateral (outside) of the foot.

I was able to find most of the issues in the vet notes, so let's go through everything one by one. There were 684 images in 40 different MRI series. Every image is a cross section of the hoof using different highlighting techniques. Series names start with T1, T2, and STIR, which are some scientific way of describing the way the machine scans (for a better description, see those links above!). Each of these highlight the structures in different ways to better see what's going on in there

Some basic structure in the T1W 3D FRO pass from wherever FA is, in Penn's front left hoof. As you progress through the immediate images in this sequence, the P2 comes more into view. Remember, this is a cross section. This happens to be a mostly vertical cross section that is square with the front/back of the hoof.

Of course the first image series called "T2 W FSE SAG" (coffin joint effusion, scar tissue in navicular bursa, navicular bursa effusion) that the vet saw something is the one series I couldn't pinpoint exactly.

The next is the big one. The tears to the collateral ligaments in series "T2 W FSE TRA". There were 3 series done like this, each from different angles: P, PF, and FP. I'm 99% sure that P is "flat", aka completely horizontal. The other two have some upward angle to them, which is why the top pair of images below look funny. The bottom of the image is the frog, cut on a forward angle.

The red arrows point to the torn ligaments. They're cloudy. The right ones are more pronounced and therefore more severe.
The green arrows point to the good ligaments, they show as black empty space.
The last thing these images show is the laminar thickening of the lateral wall in the right hoof (the right side of the right hoof). It took me a long time to identify this one, and I think I've got it right. I was only able to somewhat identify it because I put the right and left images side by side.

To help everyone figure out what they're looking at, here are two image series in GIF format. I put those anatomy pictures up above because you can see the coffin and short pastern bones from a variety of angles, as well as the "pedal" look of the coffin in the P series.

T2W FSE TRA series, PF
As you get closer to the toe, you can see the holes in the coffin bone. I assume those are for blood supply.

T2W FSE TRA series, P
Think of this series as dropping down the leg in horizontal cross sections.
I think this series is fascinating because of image 9, the coffin bone looking like the winged pedal bone, and images 10 and 11, the sole and frog.

Next is the navicular bone edema, in series "STIR FSE SAG". This is a series where water shows up as bright white.

The red circle shows the excess fluid around the navicular bone.

These two series also have a completely fascinating shot of the blood vessels in the bursa on the edges of this cross section of the foot:

The last series that had notable issues was the T1 W 3D ISO series of the left hoof. It showed marginal fractures of the navicular bone on the lateral side (the outside, which is the left side in this case).

It is very hard to see. I had to compare this series in the right foot to make sure I was seeing the correct thing. The arrow points to a thin black line in the lateral part of the navicular bone. That is a fracture.

Because MRIs are fascinating, I took the time to assemble these images and put them into short videos. The following two videos are 112 cross sections of each front hoof, the T1W 3D ISO series, shot from the FA direction.

I do wonder how many "sound" horses are running around with the same hoof issues as Penn (not including the torn collateral ligaments), and whether they actively bother the horse. I know navicular bone damage is kind of common, but what about the laminar thickening? I know we'll never have a good idea, MRIs are not cheap and you don't do them just for funsies.

As fun as it is to look through the images and delve into finding the problem areas, it all comes down to what does it all mean?

Well, it most likely means Penn's competitive career is over, as well as any secondary career he might have had being a schoolmaster. At best, he'll probably be able to W/T/C both directions, with no lateral movements.

The navicular area issues are secondary to the collateral ligament injuries. If left to their own devices, Dr Allen gave the collateral ligaments up to a 30% chance of healing to a point where Penn is sound again. He said this is the kind of injury where you can turn the horse out in a field for 12 months, and the horse will come back in just as lame as it was turned out. Poor blood supply to the hoof means collateral ligament tears as deep as the coffin don't heal well, if they heal at all.

There are things we can do to help, which we did elect to do, that increase his odds of soundness to 40-60%. I'm not sure whether those odds are for return to full work soundness, or return to WTC soundness. I have a feeling they're WTC soundness and the full work soundness is much lower. Lateral movements are most likely out of the question, as well as most hills or other uneven terrain. The collateral ligaments are fairly inflexible and stabilize the lateral flexion of the joints. Penn flails quite a bit as he moves, stressing the inside of the leg the most (note the RF, where the CL is torn on the inside, is the worse of the two tears). He could re-injure them just moving around because of how he moves; there's no need to add lateral movements and more lateral stress to the mix.

So how did this happen? And when? The vets agree that the collateral ligament tears are relatively new (probably in the last few months). The way the nerve blocks went at his visits throughout the summer, he didn't have these issues at the start, middle or end of summer. They most likely happened sometime in September or October. We didn't do nerve blocks at our appointment at the start of October, but his soundness at that appointment was very similar to his soundness at the November recheck.

He could have bounced the wrong way in turnout. He started being more active as he felt better. Our footing changed from dry yet very rainy summer to mucky, muddy fall. Maybe he slipped. I'm an extremely cautious driver when I have the trailer, but it could have happened in there if Penn compensated too hard or the wrong way, or I did something wrong driving and tossed him around. It isn't due to his poor conformation- he tore the left side of both fronts. Something actively happened to him to make that happen. I'm sure his conformation didn't help matters- the whole of his foot is a mess so it was probably already compromised and ripe for injury. I'll never know what happened exactly to end my horse's career, and that's quite sad.

Who knew this tiny amount of lameness, that could be reasoned away as muscle weakness or just simply being unbalanced, is actually two torn collateral ligaments in the front hooves? I certainly won't look at slight off moments the same again.

Link to YouTube

I'll go over the treatments offered and the treatments we did in my next post, as well as his rehab plan. This post has gone on for long enough I think.