Beckie’s Expert Interview
Mark Murrell--Navicular Disease
I have been lucky enough to ask Mark Murrell, a specialist in Lameness, his view point on Navicular Disease.
So Mark tell me a bit about yourself .
My full title is Mark Murrell MA VetMB MRCVS. I’m currently training to be certified in equine orthopaedic surgery under Dr David Platt BVSc PhD CVR DO FRCVS, a consultant orthopaedic specialist. We’re based at the Anvil Equine Veterinary Clinic, Bar Lane, Copsale, Horsham, West Sussex. 07767 318481
I generally have no life and work too hard! But do enjoy orthopaedics (lameness) enormously.
In simple terms what is Navicular Disease/Syndrome? Is there a difference between the two?
Yes, it’s very important to understand the two terms.
Navicular Disease is a degenerative disorder of the navicular bone caused by a number of factors including:
Shape of the navicular bone
Type, age, and breed of horse
Previous use
And Foot balance
It’s characterised by specific changes to the navicular bone seen on MRI scans and/or X-rays.
Navicular Syndrome is an out of date term to refer to any horse that has pain isolated to the heels, but does not respond to corrective shoeing and rest, with or without changes to the navicular bone on X-rays. With the advent of MRI, many of these horses are being diagnosed with true Navicular Disease, or with ligament or tendon disorders in the foot. These are most commonly tears in either the collateral ligaments of the coffin joint or the deep digital flexor tendon (DDFT)--this is the major tendon in the foot. Causes again include the type, age and breed of the horse, previous use, and foot balance.
Distinction is very important. The two conditions are treated and shod totally differently. The difference in treatment has led to many horses with “Navicular Syndrome” being treated wrongly, and therefore not responding, leading to the term striking fear into the hearts of horse owners, just as mention of other nightmare diseases like strangles does. Only since the advent of MRI have veterinary surgeons been able to differentiate between true Navicular Disease and other causes of what was “Navicular Syndrome”.
What signs would horse owners be able to see if there was a problem?
All horses with either true Navicular Disease or other causes of heel pain present similarly. They usually have mild or moderate (but occasionally severe) lameness of both front feet. Usually one foot is worse than the other. The lameness may appear to 'swap' legs and is often worse when the ground is hard. Affected feet may be 'boxy' with deep frog clefts prone to developing thrush. Other signs include a toe first landing, a short pottery gait and a reluctance to go forward. Physiotherapists often report tightness in the 'strap' muscles and through the shoulders. However many of these symptoms are not unique to Navicular Disease or other causes of heel pain.
Are there ways that Navicular Disease can be avoided?
Avoiding Navicular Disease is a case of good farriery. Some horses will develop Navicular Disease whatever you do, but its progression can be significantly slowed, possibly even arrested by good farriery!
What treatments are available for horses that have been diagnosed with Navicular Disease?
Other than good farriery, treatments also include controlled exercise, anti-inflammatories (i.e. bute), drugs like Navilox, used initially for its purported affect on blood flow to the region, and more recently drugs called the biphosphonates, which alter the turnover of bone in the area.
It’s important to understand that complete rest is counter-productive for the treatment of Navicular Disease. In contrast ligament and tendon strains in the foot do require complete rest, and not controlled exercise.
Because Navicular Disease is a degenerative disorder, long term control is required unless it is caught early before serious damage is done to the navicular bone. In those cases good control may be maintained with good farriery alone.
As a summary Mark, what key points would you like readers to take away from this?
Firstly, that Navicular Syndrome is an out of date term.
Second, differentiation of the causes of heel pain is very important to ensure the correct treatment.
And finally, early diagnosis is the key to successful treatment, and may require MRI scans.
Thanks very much Mark for your time and knowledge--it’s been really valuable .