A novel approach to treating herniated disc problems in dogs has been developed in a major US veterinary hospital, and its developers say the procedure could be carried out at teaching hospitals and large private clinics anywhere. Yet, although the percutaneous laser disc ablation (PLDA) procedure has been carried out successfully at the veterinary hospital at Oklahoma State University’s Center for Veterinary Health Science since late 1993, it is apparently not being performed anywhere else in the world.
The interventional radiological procedure is designed to prevent the recurrence of disc herniation with subsequent spinal cord damage, and over 300 cases have been treated at OSU’s Veterinary Medical Teaching Hospital in the past 14 years, with very good results. The success rate is based on the rate of recurrence in the treated dogs.
“Our success rate is 96.6 percent,” says Dr. Robert Bahr, Associate Professor of Veterinary Radiology at the Department of Veterinary Clinical Sciences.
“Out of all the dogs treated since the project began in 1993 (some 325 dogs total), only nine (3.4 percent) have had repeat disc herniations.”
Disc herniation is generally treated with surgical procedures . However, the most commonly performed surgical procedure, disc fenestration, is more complicated and painful for the animal than PLDA, Bahr says.
Fenestration calls for the veterinarian to surgically open the dog’s back and isolate the intervertebral discs by dissecting the muscle away from the vertebrae.
Then, using a surgical instrument shaped like a hook, the disc material is scraped out of its anatomic location which prevents it from herniating in the future. This is tremendously painful for the dog because the back muscles are cut, usually bluntly to lessen bleeding, which causes a great deal of post-operative pain as well as two to three weeks of post-surgery rehabilitation.
The laser surgery is done by placing needles through the skin into the centers of seven different disc locations while the dog is under general anesthesia. The locations are based on the most common sites of thoracolumbar intervertebral disc disease as described in the veterinary literature. An x-ray is taken to ensure that each needle tip is precisely in the center of each treated disc. Then a Holmium:YAG laser fiber is put through the needle, into the center of the disc, and the laser energy turned on.
This laser surgical treatment liquefies the disc material, and scar tissue forms, which prevents the disc from herniating and injuring the spinal cord in the future.
Dr Bahr says that, of the various treatments available, laser disc ablation results in a lower rate of recurrence than the other methods of prevention. It is also much less painful for the animal, and recovery time is much shorter.
“Disc surgical fenestration is a very old procedure, dating back to the mid-to-late1960’s. It has been superceded by other, more helpfully decompressive surgical procedures such as laminectomy and hemilaminectomy which will truly treat an already herniated disc situation by decompressing the spinal cord and even allowing actual surgical removal of the offending herniated disc material.
“Some surgeons will, at that time, also incorporate a disc fenestration as an additional procedure since the dog is already opened up, so the damage to the muscles has already been done in any effort to treat the herniated disc.”
He explains that PLDA is indicated only for dogs that are experiencing “back pain.” It is not recommended for dogs with signs of spinal compression.
Dr Robert Bahr inserts the laser needles into a patient with a herniated disc
The procedure takes about an hour from start to finish which includes pre-operative diagnostic radiography to radiographically evaluate the thoracolumbar spine. “The nice thing about the PLDA is that there is no incision to suture or wounds to treat since it’s all done through needles,” he says.
Recovery from PLDA is much shorter than from surgery. “The dogs are up and walking around later that same day, usually without any deficits at all. The only way that we know that some of them are experiencing any pain is if we gently palpate over their backs in the area of the procedure. Some dogs are a little ‘ouchy’ on that first day and for a day or two afterwards.
“They are always sent home the day after the procedure with a prescription for NSAIDs to help relieve any pain that may be residual. Many owners say that they give the pills for two or three days and then discontinue the meds because they cannot see any evidence of pain as they interact with their dogs.”
Bahr says the comparative risks for both procedures are anaesthetic risk, damage to the spinal cord or nerve roots should they be nicked by either the surgical scalpel or the spinal needles, and post-operative infections.
“The relative risk of infection is much greater for the surgical disc fenestration since it takes longer and there is so much more tissue exposed to the air during the procedure, inviting microorganisms to enter the tissues. By contrast, the tiny invasion of the spinal needles, which are sterile, for the PLDA, carries a much lower risk of infection.
“There is also the much greater risk of permanent muscle damage and resultant scar tissue formation by the much more invasive surgical disc fenestration procedure than there is for the small amount of damage caused by the insertion of 22 gauge needles through the muscles into the disc themselves.”
Certain breeds of dogs are more likely to require some form of treatment to prevent future recurrence of degenerative disc disease with disc herniation. These include Dachshund, Shih Tzu, Lhasa Apso, Pomeranian, Miniature Schnauzer, Miniature and Toy Poodle, Yorkshire Terrier and Cocker Spaniel, among other small breeds of dogs.
Large breed dogs can also be affected, but the disease is slower to develop and has a somewhat different pathophysiology, Bahr says. “The small breed type having a faster onset and potentially more explosive herniation of disc material, which can do much more damage to the spinal cord and its nerves than does the type of disc disease in larger dog.
“In larger breeds it may cause less severe spinal cord damage and is also less likely to recur. So, when large breeds get it, the onset is often more gradual, and the consequences are not so severe and so potentially devastating.”
“The small breed form of the disease fairly commonly results in some degree of dystrophic mineralisation of the disc itself, but that, in itself, does not necessarily cause the disc to herniate,” he says. “Aggravating factors may include the body conformation of some small breeds, such as the Dachshund, as well as the more hyperactive behavior of many small breeds. No one really knows for sure.”
The Veterinary Teaching Hospital at the CVHS treats two to five disc cases each week and sees patients from Oklahoma and the surrounding states of the south-central and mid-west to the east coast of the US. OSU veterinarians have also used the procedure to treat patients from as far away as Idaho and Oregon. The procedure costs approximately $US1,500 inclusive.
Bahr is at a loss as to why percutaneous laser ablation has not been picked up by other veterinary hospitals in the US. Research on the procedure has been published twice, in the Journal of the American Veterinary Medical Association. He and his colleagues have also made oral presentations of abstracts at the annual scientific meetings of the American College of Veterinary Radiology and the International Veterinary Radiology Association.
He says that while any licensed veterinarian in the US could legally do the procedure, “this is most definitely not any easy technique to learn.
“It has a rather long and steep learning curve as it takes much experience in placing the needles into the centres of the disc while trying to negotiate around the protruding ribs, in the case of the thoracic region, and the transverse spinous processes, in the case of the lumbar region. The ribs are definitely worse, and the degree to which they cause a problem varies greatly from dog to dog and also between breeds.
“It is often quite difficult to manouevre the needle around the rib and into the correct spot, resulting in significant bending of the needle. I would say that it took me probably 4-6 months to learn the procedure well enough that I felt fairly confident in performing it.”
He also stresses that as PLDA is a radiological intervention, it should be performed by radiologist. “Radiologists are trained in interpreting and viewing two-dimensional radiographic images to a much greater degree of ability than are surgeons, and we have the training that it takes to manipulate needles and small catheters into certain anatomic areas using fluoroscopic and ultrasound guidance.”
Bahr says that given the expensive equipment required, the steep learning curve and the need to perform the procedure reasonably frequently in order to stay competent, it would be unlikely that a “normal” busy practice of 3-4 partners would have the time, expertise or financial underpinnings to undertake this procedure as a routine addition to what they offer their clients.
However, he also doesn’t think PLDA should be confined to teaching hospitals. “We have many very fine specialty private practices in the USA, some with 25-30 practicing veterinarians, most of whom are specialists. They see an enormous caseload of referral cases, many of which would qualify for and benefit from this procedure. If they have a veterinary radiologist as a part of their team, I don’t see why they couldn’t incorporate this procedure into what they offer their clientele, especially if they are already doing laser surgeries anyway.
“As long as the hospital has the facilities, personnel, and equipment, they wouldn’t even necessarily have to have their own on-site, resident veterinary radiologist. Such a radiologist with the proper credentials and training could visit such a hospital once a month and do their batched cases.”
For more information on percutaneous laser disc ablation surgery, visit Oklahoma State University’s Center for Veterinary Health Science.