Guest Article
by David Dycus, DVM, MS, CCRP, Diplomate, American College of Veterinary Surgeons – Small Animal
Orthopedic Staff Surgeon, Veterinary Orthopedic and Sports Medicine Group (VOSM)
Co-Founder/Co-Director, Veterinary Sports Medicine and Rehabilitation Institute (VSMRI)
Distinguishing between orthopedic and neurological symptoms
A common presentation to the veterinarian is a patient with an abnormal gait. However, the challenge is often trying to determine if the patient suffers from an orthopedic problem, neurologic problem, or possibly both. Given that both the musculoskeletal and nervous systems contribute to gait it can be difficult to differentiate, not to mention that many of the orthopedic problems can occur bilaterally.
To begin the process of deciding the cause of the patient’s clinical signs, a thorough history can be very helpful. In your patient history, make sure you capture:
- The duration of clinical signs
- The timeline of occurrence
- The progression of clinical signs
- If the patient is able to go up or downstairs
- Are they willing to jump up or jump off objects
- Do they appear stiffer after heavy play and warm out of the stiffness, or are the clinical signs present consistently?
- For example, many patients with an orthopedic problem will tend to be stiff in the mornings, and after heavy play, but will in some cases warm out of the stiffness. Alternatively, in patients with neurologic problems, the clinical signs will remain or even worsen with activity.
What to look for in a gait analysis
Gait evaluation is critical, but even before evaluating the gait, pay attention to how the dog rises from laying down as some orthopedic problems will only be noticeable upon rising and the first few steps.
Have the owner or a technician walk the dog towards you, away from you, and watch from the sides. In addition, evaluation of the gait at the walk or trot is important. In dogs with orthopedic issues, the trot is usually more important for identifying a lameness; while for neurologic patients, a slower gait is usually needed to identify deficits.
During the gait analysis, dogs with orthopedic issues will usually exhibit a shorter stride to the gait on the affected limb(s); while this is not true for neurologic patients. For cats, allow free roaming in the examination room. Pay particular attention to the mentation and curiosity of the cat. A trick that can be used with the cat is to put the cat on an examination table and the cat carrier on the floor. Most cats should readily want to jump off the examination table into their carrier to seek safety. An indication of joint pain can be a cat that hesitates or refuses to jump off the examination table. In addition, the way a cat lands can provide evidence on what hurts. Most cats will have a soft elegant landing. Cats will painful elbows will have a more harsh landing as they are trying to get the hind limbs to the ground as quickly as possible to unload the elbows.
Conduct neurological and orthopedic exams
Following the gait evaluation, both a neurologic and orthopedic examination should be completed. It is best to always approach the examination in the same way. For me, I will begin at the toes and work my way proximally, trying to examine the affected limb last with the patient standing. When focusing on the toes, especially the hind limbs, I will check for a roughening of the dorsal part of the nails. This suggests there is toe dragging or catching commonly seen in patients with neurologic problems. However, it should be noted that dragging or catching the toenails when walking is not pathognomonic for a neurologic condition. Certain breeds such as German Shepherds have a lower carriage of the hind limbs. This, in addition to severe hip dysplasia, can result in catching the toenails at the walk.
After palpation of the nails, I will then check conscious proprioception by flipping the hind paw over. In the normal patient, the paw should immediately be corrected. Patients with neurologic problems will often have a delay in proprioception. Complicating matters is that if a patient suffers from an orthopedic problem, they could be off-loading the limb and create the appearance of delayed proprioception by not putting appropriate weight on the limb. In these situations, I will have my technician lightly push the dog towards me to force weight onto the affected limb. Lack of proprioception does not fully rule out a neurologic problem either. Dogs with lumbosacral changes may have normal proprioception. After checking for proprioception deficits I will then perform a hopping exercise with the patients to further check for neurologic deficits.
Causes of hind limb lameness
Cranial cruciate ligament (CrCL) pathology is a very common cause of hind limb lameness and given the degenerative nature, there is a high likelihood of bilateral disease. In addition, chronic CrCL pathology will result in osteoarthritis. It may be easy to get confused watching dogs with bilateral chronic CrCL tears walk and mistake it for a neurologic problem. Or in very acute cases, the dog may not be able to walk and it is thought they are down neurologically. When evaluating the stifles, pay particular attention for peri-articular fibrosis (“medial buttress”) to indicate chronicity along with a reduction or discomfort on the range of motion. Checking for tibial thrust and cranial drawer in both extension and flexion is needed to determine if there is CrCL pathology. However, chronic tears, especially partial tears, can be challenging to identify instability. Checking for pain on hyperextension is another test that can be used to determine CrCL pathology.
Hip dysplasia is another common cause of hind limb lameness that ultimately leads to osteoarthritis. Given that it is a developmental orthopedic condition; patients are commonly affected bilaterally. In the young dog with hip laxity, there may be a “hip sway”, lack of exercise, or reluctance to want to walk, making one think a neurologic problem. Hip palpation in the immature patient may reveal discomfort on hip extension or a reduction in hip extension; however, hip flexion should be normal. An Ortolani test to mimic laxity can be completed.
In the mature patient with hip osteoarthritis, there may be a reluctance to exercise, stiffness when rising, or reluctance to rising making one think of lumbosacral issues. Dogs with hip osteoarthritis will typically have normal flexion (unless severe) but will have a significantly reduced range of motion and discomfort in extension. Some patients will have both hip osteoarthritis and lower back issues.
To help differentiate, I will palpate the lower back by placing pressure on the lumbosacral region. I should be able to apply firm downward pressure with no pain response and the patient should not collapse or begin to sit. If this is normal, I will then firmly palpate just medial to the ilial wing at the lumbosacral junction on both the left and right side to help rule out lateralized lower back pain that can cause a unilateral lameness or off-loading. Raising the tail upward can also incite a pain response in patients with lower back problems. If I suspect a neurologic problem affecting the hind limbs, I will check for reflexes; however, it is important to remember that in patients with chronic orthopedic issues and osteoarthritis some reflexes may be diminished such as the patellar reflex.
Identifying front limb issues
The front limbs tend to be a bit easier to distinguish. Many patients with neurologic problems of the front limbs will also have the hind limbs affected. However, it is important to remember that a cervical lesion (such as intervertebral disk disease) or an axillary lesion (such as a peripheral nerve sheath tumor) can cause a unilateral front limb lameness. With every orthopedic examination, I make sure to palpate the cervical region to check for pain as well as check the cervical range of motion. Patients with axillary lesions will sometimes be painful on deep palpation; however, severe muscle loss (particularly of the triceps) is commonly associated with peripheral nerve sheath tumors.
Diagnostics are a must when trying to decide between an orthopedic or neurologic problem. For a hind limb lameness, I would recommend taking orthogonal views of both stifles (to include the hocks), and pelvis. This will help to determine effusion in the stifles (raising the concern for CrCL pathology) or effusion in multiple joints suggestive of a polyarthropathy. The hips can be evaluated for laxity as well as osteoarthritis; in addition, the lumbosacral region can be evaluated for degenerative changes, spondylosis, etc. Lastly, bony tumors can be ruled out.
For the front limb, I typically recommend six views. Orthogonal views of both elbows (including the carpi) and laterals of both shoulders. If the patient will tolerate it, a VD view of the shoulders can be included. Outside of elbow osteoarthritis, front limb radiographs largely tend to be normal. However, pay particular attention to the soft tissues especially of the shoulder region for differences in muscle mass. For neurologic concerns of the front limbs, I will also take cervical radiographs. Unfortunately for most neurological issues and some orthopedic issues advanced imaging such as CT, MRI, or ultrasound may be needed.
SUMMARY
Deciding on an orthopedic problem versus a neurologic problem is not always easy. Don’t underestimate a thorough history as well as an in-depth gait assessment and methodical orthopedic and neurologic examination. In a general sense, orthopedic issues tend to improve with exercise as the patient is warmed up and doesn’t exhibit proprioception or reflex deficits.