News from Garner Equine

This month we want to discuss something we all eventually have problems with ...lameness. Whether acute, chronic, or chronic- progressive, and no matter what discipline you practice, sooner or later you will find your horse lame.

Let's start with the diagnostic lameness exam and an explanation of the process we go through to pinpoint the exact cause of lameness and provide us with specific therapeutic options. In later installments, we will discuss certain more common causes of lameness and their treatments. (Start putting together a list of things you would like to see

covered in the future!)

The initial steps in our lameness exam are to determine which limb/limbs are involved, and to piece together a history that includes, but is not limited to, the onset, duration, severity and response to rest or treatment of the lameness our client is concerned with (the client complaint). Most often, the client complaint is simply a somewhat vague performance-related problem, ie. "quit stopping" , "trouble on second barrel", "won't pick up the left lead", etc. While discussing the important aspects of the history we will generally be physically going over the horse, visually and manually, limb to limb, the "laying of the hands".

After the hoof tester exam, palpating tendons, ligaments, joint capsules, and passive flexion of all joints, looking for any indications of inflammation and/or pain, we will move on to the gait evaluation and stress tests. (Obvious lameness issues may be diagnosed already with any of the above steps).

Gait evaluation is performed, usually at a trot, on a firm even surface, straight and in circles, keeping notes on different responses of the horse to changing conditions. Sometimes, we move to softer footing, with a rider on in order to replicate conditions in which the complaint occurs. Joint stress tests, or flexion tests, are performed in order to localize pain to certain areas so that we may perform diagnostic anesthesia on these joints/ regions. During this process many clients are surprised to learn that not only is their horse sore or lame in several limbs or regions of one limb, but it is often NOT where they suspected it would be. This is the main reason this topic was chosen, to help clients develop confidence and understanding in the diagnostic process.

Once areas of interest are established, we move on to diagnostic anesthesia, joint and/or nerve blocks. This is the application of local anesthetics to specific areas- once a region is deadened, or "blocked", if the horse becomes sound or the stress tests no longer cause an exacerbation of the lameness, then we have correctly identified the region or structure that the lameness originates from. Generally speaking, nerve blocks, when performed at certain pre-determined levels of the equine limb, can pinpoint the cause of lameness to within a 3"-6" portion of the leg, to include both intra-articular (joint) and extra-articular (soft tissue) structures of that region. Joint blocks, or intra-articular anesthesia, generally diagnose only that pain that comes directly from inside the joint in question. Therefore, we use nerve blocks to arrive in the vicinity, and joint or specific anatomic blocks to navigate to a more precise location. This can be repeated, if necessary, for multiple limbs or multiple points per limb, as the case dictates. We can then move on to the imaging stage of the diagnosis.

Depending on which anatomic structures we suspect, we usually start with either radiography or ultrasonography. While there is a lot of common ground covered by these two imaging modalities, generally speaking radiographs are best for bone and joint imaging, while ultrasound works best to visualize tendons, ligaments, and other supportive soft tissues. Another modality we are using on an increasing basis is Magnetic Resonance Imaging. MRI is more sensitive in many aspects than both radiography and ultrasonography, and presents an extremely detailed 3-D image of any area it is applied to. It has several drawbacks, however. The first drawback is two-fold: we need to specify very precisely the area to be scanned, and the MR tunnel also has severe limitations as to which part of the horse will actually fit inside to be scanned. The second drawback is that MRI will identify any anatomic abnormalities in a scanned region, but will not always tell us which ones are actually causing the problem. So, back to diagnostic anesthesia, huh? So much for the wonders of technology! Seriously, this is a powerful diagnostic aid when employed with local anesthesia and within its limitations. Probably the one with the most future potential of them all.

OK, this has probably diagnosed about 90% of the lameness that we will routinely deal with, but there are a few cases where we are left hanging without a diagnosis. What about that jumper with a quirky hind end that acts up every once in a while? We've attempted to block him out several times all the way up through the hip joint and have never been successful. Here is where Nuclear Scintigraphy comes in handy. Commonly called a "bone scan", this is a process that helps us to localize a lameness based on the principle that inflamed areas uptake increased amounts of radioactive marker, which is injected into the body and then measured at different locations. The "hotspot" marks the spot! Because of the expense, it is usually not substituted for diagnostic anesthesia, but performs much the same function in cases where nerve and joint blocks are of limited or no use.

Then, there is the 3 year old futurity prospect who couldn't hold his stops. We've localized the pain to his right stifle, and he blocks sound to intra-articular anesthesia in that joint, but when radiographed, there are no signs of bone or joint disease. We know where the problem lies, so nuclear scintigraphy is of no real use to us and the stifle is too high up the leg to fit in the MRI tunnel. He has been injected several times, but the lameness either always persists or returns very shorty after therapy. What do we do for him? The most invasive diagnostic imaging..... arthroscopic surgery. We put him under general anesthesia and actually look in the joint. While more invasive and more expensive, it gives us an actual view of what is going on, and the opportunity to physically correct it since we are already inside the joint. Arthroscopy is not necessarily the first tool we reach for, but it is often the one that will give us the best answer.

So, there is a look at some of what we have in our diagnostic tool kit, and the process by which we answer you when you ask "My horse was off a half second in his pattern last weekend. What do you think it might be, Doc?"