Pain Management Case of the Month: Quincy—Why Is This Surgery Patient Still Limping?

Quincy is a neutered male greyhound mix who was a rescue dog and is estimated to be about 18 months old. Six months after surgery on his left knee for a luxating patella, he’s still limping.

by Michael C. Petty, DVM, CCRT, CVPP, DAAPM

Signalment and History

Quincy is a neutered male greyhound mix who was a rescue dog and is estimated to be about 18 months old. Before his visit to my practice, he had surgery on his left knee for a luxating patella that had been causing him some pain and some gait abnormalities. Six weeks had passed since his surgery and Quincy was rarely putting any weight on the leg, despite every indication that the surgery was successful and that the leg seemed to be healing as expected. Quincy had previously been on tramadol and carprofen, but because no sign of pain or inflammation was seen in the affected knee, they had been discontinued.

Physical Examination

My physical exam of Quincy was unremarkable other than his lameness issue. Distant observation showed that Quincy carried his left hind leg while walking and would either hold it up or slightly toe-touch at rest. Upon palpation of the affected leg, there was excellent range of motion in the knee with no pain or crepitus evident. The patella was in a normal position with no luxation during manipulation. Myofascial examination of Quincy (discussion to follow) revealed many areas of taut bands and trigger points, especially in the left hind and right front legs. There was also severe pain on palpation of the left iliopsoas muscle.

Treatment and Outcome

Therapy involved mild sedation with hydromorphone and dexmedetomidine, followed by dry needling of the taut bands. Quincy had many trigger points in the sartorius m., rectus m., vastus mm. group, infraspinatus, and long head of the triceps. After his dry needling session and reversal of the hydromorphone and dexmedetomidine, Quincy walked out of the hospital using his left hind leg with much more confidence and consistency. Indeed, the owner said she felt he was putting his full weight on it.

Postoperative radiograph

Quincy being dry needled

Quincy after dry needling, walking on both hind legs

Myofascial Pain Syndrome (MPS)

MPS is a problem wherein a chronically worked group of muscles develops a permanent contracture, causing pain, poor joint mechanics, and reduced function of the affected muscles and the limb it serves. This comes about because whenever there is a minimal contracture of a muscle group, only a few muscle fibers are ever employed. These muscle fibers eventually become exhausted, yet each muscle is hardwired to only use that same set of muscle fibers whenever there is a minimal contraction. We have all experienced it ourselves: writer’s cramp is less common with the advent of word processors but was familiar to anyone writing longhand for any length of time.

With the use of keyboards, we are more likely to get MPS in our neck whenever we are not sitting properly at the computer. Another example is when you are doing a physical task like screwing in a light bulb; if you are holding the bulb over your head and you don’t get the thread started right away, your arm can become quickly exhausted despite the negligible weight of the bulb. This problem has been described as the Cinderella hypothesis because no matter how long or hard Cinderella works, none of her sisters (in this case muscle fibers) ever come to her aid. If the problem is temporary, like writing or typing, then the MPS can often resolve on its own. But if the problem is chronic, the MPS can be permanent unless there is intervention. In the case of Quincy, in the first weeks after surgery, it was much too painful to bear weight on his leg . . . but by the time the knee had healed, MPS had set in. Additionally, his contralateral leg also had trigger points as he tried to shift his weight from his left hind leg to his right front leg, overworking those muscle fibers as well.

When a muscle contracts, energy in the form of adenosine triphosphate (ATP) is needed for the actin and myosin to break their bonds and allow the muscle to relax. This is why rigor mortis sets in; as the body’s store of ATP is depleted after death, there is no mechanism to allow muscles to relax until there is decomposition of the tissue.

Medical treatment of MPS can involve several methods. Massage can bring blood (and ATP) into the constricted areas of muscle. Laser therapy can also increase blood flow and mitochondrial activity. Another therapy is called dry needling.

Within each of these contracted or taut bands of muscle is something called a trigger point that is situated in close association with the motor endplate. Putting an acupuncture needle into this trigger point will stimulate the motor endplate, sending a signal to the dorsal horn of the spinal cord, which in turn sends a signal back to the motor endplate, causing it to relax the muscle fibers. This treatment bypasses the need for increasing ATP and the results are instantaneous, as they were for Quincy. As such, it is often a preferred method of therapy for MPS.

For more information on myofascial pain, I recommend Myofascial Trigger Points by Jan Dommerholt and Peter Huijbregts or Myofascial Pain and Dysfunction: The Trigger Point Manual by Janet Travell and David Simons. Both of these are human texts but are applicable to our animal patients. If you are interested in learning more about massage therapy, I recommend Canine Medical Massage by Narda Robinson and Shelley Sheets.

Discussion

In my referral practice, I often see animals who are referred to me when surgical procedures do not produce the desired results. More often than not, the surgical procedure was performed correctly and the leg healed as expected, yet the animal either refuses to use the limb or does so poorly. Often, the surgeon is perplexed, the owner is distraught, and the animal is in pain. But a careful myofascial pain exam can reveal the presence of taut bands and trigger points, and a few sessions of dry needling can return the limb to normal function.

Mike Petty
Michael C. Petty, DVM, CCRT, CVPP, DAAPM, is in private practice in Canton, Michigan. He is a frequent national and international lecturer on topics related to pain management. Petty offers commentary on each Pain Case of the Month (and occasionally writes one himself). He was also a member of the task force for the 2015 AAHA/AAFP Pain Management Guidelines for Dogs and Cats.

 

Photo credits: Photos courtesy of Michael Petty

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