Proximal Suspensory Desmitis

  Overview

Proximal Suspensory Desmitis (PSD) has been increasingly diagnosed in recent years as a cause of hind limb lameness.  It is usually diagnosed based on gait analysis, perineural analgesia (local nerve block) of the deep branch of the lateral plantar nerve, and ultrasound of the proximal suspensory ligaments. PSD can be in one leg or both (bilateral). The proximal suspensory ligament is the top section of the suspensory ligament below the hock that is closer to the body than the low (distal) end!

The conventional recommended treatment options offer conservative treatment with a "large proportion of horses" having persistent or recurrent lameness, shock wave therapy with approximately 40% of horses returning to full athletic function or surgical treatment by neurectomy (cut the nerve) of the deep branch of the lateral plantar nerve and plantar fasciotomy (cut the soft tissue around the ligament to free it up) with approximately 70% of horses supposedly being able to return to full athletic function ... but for how long before the hock is crocked?.

The intensity of the work at the highest levels of competition is frequently blamed for the ocurrence of this condition. On the face of the above information many supposed top horses have had and are recommended to go down the surgical route.  This surgery renders the horse ineligible to compete at FEI level, BSJA and BE and is on a par with administering a banned substance in my opinion.  Unfortunately because the surgery is performed through a very small incision it is very difficult to tell if a horse has undergone this surgical intervention or indeed another similar de-nerving procedure elsewhere.  Due to the value of horses competing at this level and the difficulty in spotting if such a procedure has taken place I believe there are a significant number of owners and riders who have been encouraged to continue competing horses at FEI level in breach of the regulations.  Having gone down this road of deception it becomes impossible to openly declare it within a Vetting procedure due to the implications for the previous owner and rider and the value of the horse unless the new owner/rider is prepared to continue the deception. There are obviously implications for the veterinary surgeons involved who may or may not be aware of the horse's history in a sale situation.

Roger's Opinion

I find it interesting that the non-intervention option that obviously doesn't generate much income compared to treatment is only very vaguely stated as "not very successful".  No actual success figure is quoted to enable owners to make a fully informed decision as to how much better shock wave therapy or surgery may or may not be, or am I getting overly cynical?! No other options are suggested either!

I (and others) believe that in the vast majority of cases, PSD is not a primary condition in itself but is symptomatic of one or more other problems that alter the gait/posture and result in inflammation of the proximal suspensory ligaments.  From the ultrasound pictures there can be no doubt that there is indeed inflammation present. However the fact that approximately 30% of horses having had the neurectomy (so that they can no longer feel the inflamed suspensory ligaments) still remain lame suggests that not only is the seat of lameness elsewhere, but that the perineural nerve block resulted in a false positive return to soundness during the lameness case work-up.  On the wider stage this must question the efficacy of high leg nerve blocks.  Do horses that still feel pain but cannot feel a significant portion their lower leg from a nerve block appear to become sound due to movement based on central locomotor memory rather than what they feel? ie do they move in a sound manner because of how their brain remembers it should do because they lack sufficient sensory function to co-ordinate adequately whilst continuing to respond to remaining pain? This area needs research I think.

Coming back to the PSD itself I have been approached by a number of clients who decided to find another approach to the problem rather than go down the shockwave or surgical routes.  Invariably a primary cause of the secondary PSD has been found and successfully treated using conservative techniques.  This successful treatment by myself and others either together as a team or separately by focusing treatment outside the immediate suspensory ligament area would seem to vindicate our position that PSD is a secondary condition indicative of other problems.

But what of those horses who have gone sound and returned to full athletic performance having undergone surgery?  Well of course not all problems that alter gait are painful once the body compensates for that problem.  In fact the figures suggest that 70% of causes that feed into bilateral suspensory desmitis are not necessarily painful in themselves once the gait has altered.  However, the neurectomy and fasciotomy do not remove the underlying cause which will frequently manifest elsewhere over time and will inevitably lead to an exacerbation of the strain on the proximal suspensory ligaments that the horse can no longer feel.  I have heard it said that there is a very poor prognosis for a subsequent lameness in a horse that has had a neurectomy in the past.  The feedback I am hearing is that following neurectomy a significant number of horses subsequently go lame due to hock issues.  This would seem to indicate that the PSD is the warning of impending hock joint disease.  Where is the sense in removing the warning mechanism? It would also indicate that the primary problems I and others focus on when treating PSD will continue to cause postural and gait issues unless identified and treated and will frquently lead to hock issues.  This again confirms my position that PSD is a secondary symptom of a primary issue elsewhere.

It is not the role of a veterinary surgeon to perform a surgical procedure that falsely allows an individual horse to perform at a level that it cannot naturally sustain.  Neurectomies should only ever be performed as a salvage procedure to enable quality of life in a retirement situation when all other avenues have been exhausted.

If a significant number of top performance horses are having this problem it either means that

1. the individual horse is incapable of working at that level, or
2. the training/management of that horse is inappropriate or
3. we are asking too much of horses generally to expect them to perform at that level in which case vets should be highlighting this issue so that the FEI can alter tests and standards accordingly to find a different way of separating the stars from the also rans.

There is an easy solution in that the FEI could require all veterinary surgeons performing this procedure to register the fact both for previously completed surgeries and in the future.  Those who have set out to deliberately cheat or aid in cheating be they vets, owners or riders would be discovered and horses would be safeguarded as is our veterinary and moral responsibility.  It isn't rocket science to work out this solution but the FEI have yet to bring it into force.  Of course there is nothing to prevent a procedure not being reported, but at present the vets who are performing these FEI-banned procedures on FEI-competing horses and ponies can claim that they informed the owners so that they cease to have any liability.  If the vets were to have the legal responsibility to inform the FEI there would be no excuse if a horse is discovered to have competed illegally and these vets would be found out. I suspect the threat and risk of being found out would be sufficient to significantly reduce the incidence of this procedure.

Presumably Equine Insurers are not being informed either or being asked to pay out on FEI-banned procedures for FEI competing horses in which case they will have to decide what their position on this matter should be and bring appropriate pressure to bear. How many horses, having had an FEI-banned procedure that has not been declared have subsequently been paid out on for loss of use? This defrauds the insurance companies and increases the premiums for others.

If you have a horse that has been diagnosed with this condition I would recommend a more conservative approach to ascertain the reason behind why the suspensory ligaments are inflamed.  By treating/correcting any other issue(s) that are treatable you will have a horse that is sound and far less likely to go lame in the future.  You will also be able to compete at FEI level if you so wish with a clear conscience.  If the reason for the proximal suspensory desmitis is conformational and/or untreatable it is better to find this out before you breed from them or push the horse harder in work which will inevitably create further health issues that could at worst have repercussions on the rider.

Update - July 2008

Since writing the above piece I have been approached on more than one occasion by owners who have had hind limbs scanned with a clear result for the suspensory ligaments.  The vets involved however have decided to ignore the clear scan and have carried on treating for PSD regardless.  This is outrageous - why perform a scan if the result is to be ignored, and why offer expensive treatment to an area that has been shown to be clear on investigation??  Do not be fooled by this approach or allow your horse to undergo unnecessary treatment.  If your horse is insured you are wasting your treatment allowance and risking unnecessary exclusions that might prove important in the future.

I have also heard the disturbing story of a horse that was denerved for a different issue so that the foot no longer had sensory innervation.  This horse subsequently got a foot abscess which it couldn't feel and so was not investigated. Unfortunately, the abscess only became apparent when the horse stepped out of it's hoof one day and had to be shot.  The only saving grace is that the horse couldn't feel this horrific ocurrence.  This is a sobering reminder as to why medicine shouldn't always do something that can be done.

Update - August 2008

Just when I thought I'd heard all there is to hear that's bad about the denerving operation for PSD, I get an email from someone who has been recommended to have this surgery done on their 4 year old.  Such a young horse is not fully developed and should NEVER be considered for such a dramatic and irreversible procedure.  There are likely to be many more factors in a young horse that can feed into the proximal suspensory ligament area.  These could range from developmental growth spurts, teeth issues, farriery issues and inappropriate training techniques etc all of which will be variable, changing and easily sorted on an ongoing basis until the horse has fully matured physically and mentally.  Do not be bullied into such drastic surgery for a procedure that should only ever, if at all, be a last resort salvage operation for an old horse.

Update - August 2009

I've seen 4 horses and ponies over the last couple of months diagnosed with PSD. All were being encouraged to have surgery.  One vet lost a client for refusing to refer a horse to me or for anything other than surgery.  Luckily for the horse (already competing at FEI level!) the owner refused, sacked the vet and got me to have a look.  There was little wrong with the horse other than a slightly rotated pelvis and questionable saddle causing a sore back.

Question: How many are having irreversible de-nerving surgery (that is banned for a reason) as a result of minor problems that are easily sorted? 

Answer: All of them. Don't become one of that sad statistic.

Update - December 2010

Another year has passed and the number of enquiries from distraught owners regarding horses recommended for surgery and euthanasia doesn't appear to be slowing down.  Every horse I've seen during 2010 has revealed reasons why the PSD has occurred that can be relatively easily sorted. 

It has been brought to my attention that some other vets are undermining my views and work on the basis that I'm somehow not an equine vet or that I'm a cowboy!!  Well I am a vet and most of my work is with horses. If that doesn't make me an equine vet then I'm happy not be labelled as one! I'm not into labels anyway! Frankly, in those circumstances I'm sure you'd rather get the correct treatment for a horse by a non-equine vet who thinks outside the proverbial box than be given the wrong treatment by an equine vet who's stuck in the wrong box! As for me being a cowboy it's not me who's advising owners to have their horse shot.  I'd accept that label if I am and if someone else is fixing all my reject cases for a fraction of the cost I charge. All my work comes through recommendation by word of mouth. If I don't get results nobody would recommend me. 

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About Roger

Vaccination

Proximal Suspensory Desmitis

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"I owe it to treating PSD holistically"

Karen Simpson

Horse & Hound 27 Oct 2011

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"When we bought him we were told he cannot show jump. Since you treated him for PSD he has been successfully jumping!!"

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"When we brought him home after staying with you for treatment for PSD he went out in the field and did the best extended trot I've ever seen him do!"

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September 2010

"Thank you for sorting Whoop! He did his first competition since his PSD problems. 2nd, 1st, 2nd against the para team horses. He was fabulous! Thanks so much!"

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Read a testimonial from one satisfied client following treatment.

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November 2011

"Hi, just a quick e-mail to say thanks to you and Bob for the work you did sorting my horse out, attached to this message is a photo from today of him doing his first dressage test in over 4 years, you know the horse that Sue Dyson told me should be put down as he would never stay 'paddock sound'. Just thought you might be interested to see!!!"

M.H. Sussex

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