I can confidently admit that I can recognize lameness in horses better than I could 3 weeks ago. Over a hundred horses have walked, jogged or circled around me since the start of my veterinary shadowing experience, and I think my assessment skills have improved immensely. I can also confidently say that while I’ve improved, I still have cases where I misidentified the lame leg or saw lameness in a horse that was completely sound. Identifying lameness involves subjective observation, experience and knowledge.
I sometimes wish experience could be put in a pill form, taken with a glass of water the night before you need it.
I’m lacking on the experience portion, and have been really working on improving my objective assessment skills…but, as an objective-based exam, there is inherently a wide variation for interpretation. There are some trainers that could school me on which leg a horse is “off” on all day long, because they’ve been watching horse locomotion for over 40 years…someday I’ll get there.
But the only thing experience and a pill have in common is that it’s just going to be one thing that I have to swallow and take in stride.
Recommended book for the equine shelf…
Aside from using the knowledge and experience from seasoned veterinarians, there are several great books that I frequently run to….
One of my most frequented books is a small, concise spiral bound injection book. I recommend this book to anyone who wants a reference when it comes to putting needles into a horse’s joint.
I was shown this book by a colleague, and was so enamored with it that I took pictures of all the pages and made myself a digital and printed version. Another gem I acquired outside of the vet school.
Continuing where I left off last time, part of the lameness examination involves diagnostic to identify the location of the origin of pain. This involves a process of elimination.
If flexion or lameness is obvious in a particular limb, the next step is to localize. Instead of taking an expensive series of radiographs of an entire limb, providing local perineural anesthetics (like 3 ml of carbocaine), can help determine where the source of the pain is.
This technique is shades of gray rather than black and white, because some regions of the limb are supplied by different nerves. If you block a nerve by injecting a numbing agent around it, then trot the horse and see improvement, the cause of the lameness is usually from structure that the “numbed” nerve supplies. Improvement of about 60-70% after blocking a nerve would be considered diagnostic for the pain source. So far, I’ve rarely seen an instance where a successful block eliminated 100% of the lameness. I figure this is due to compensatory pain or weakness in other structures secondary to the main problem.
There are a couple useful charts for quickly looking up which nerve supplies which structures. Another chart helps with proper preparation of sites prior to injection (needle size, whether to clip the fur or not). I have a list of the block locations such as PDN, high 4 point, low 4 point etc but even more useful than the table is a “flow chart” of the nerves, which I shared below. This helps with the systematic block-by-block procedure that you’ll typically do when trying to identify the source of the lameness.
You want to go as “downstream” along the nerve as possible, and then perform each block as you progress towards the horse’s body. Otherwise, performing a block at th elbow would numb the whole limb…and not be helpful in determining if the lameness is due to a sesamoiditis or navicular disease (although these would present differently and history would help you eliminate differentials)
Localizing the lameness then sets the stage for further diagnostics…radiographs, MRI, CT…pick your poison.
I know, I know. Relatively weak review on the lameness exam enigma…but it’s 4:30 am, and I’m exhausted. I’m ready for a quiet weekend.
But, I did want to share something amazing about my shadowing experience. Usually people hate commutes, and I commute an hour and 15 minutes one way…and I love every single mile of it.
Nothing like a quiet, scenic early morning drive to get your mind ready for all the stresses of the day.
This week, I stopped to snap a picture of the sunrise.