Max's "Drawer Motion"

Little Max is a lucky dog. He and his buddy, Ewoki, get to go on walks and to the dog park all the time with their human and have a wonderful time doing that. This weekend, though, he over did it and came up lame on a hind leg-ouch! He was holding his leg up, not wanting to put any weight on it at all yesterday. He is a bit better today, touching his toes to the ground, but you can see that he is off his game a bit and so his owner brought him in to see us.

Do you remember reading about Charlie and his hind leg lameness on New Year's Eve? I said that when dogs are lame in the hind end, there are numerous things that could be wrong-anything from a thorn in the paw (wouldn't it be nice if they all were that simple?) to hip dysplasia (an inherited condition where the hip joint never formed correctly, resulting in a progressive, painful degenerative condition.) But there is one problem that is so common that we tend to say all hind leg lame dogs have this until proven otherwise. The problem is called ACL or CCL rupture-anterior (or cranial) cruciate ligament rupture or tear.

The ACL's "job" is to connect the top bone (femur) and bottom bone (tiba) and to stabilize the motion of the joint, keeping it from moving in abnormal ways. We know a knee joint should flex back and forth, but if the ligament is injured, the joint may have what we call "drawer" motion; the lower tibia will move forward as if you are pulling a drawer out of a desk or dresser. Drawer motion is abnormal and when it is present during an exam (done under sedation or anesthesia due to the pain of manipulation and because the strong muscles of the leg will hold the joint together in an awake animal) confirms the diagnosis of ACL rupture. Max had definite drawer motion in his affected stifle and no abnormal motion at all in his good leg. We then took radiographs during his sedation so we could see if there was any other problem like fractures or even neoplasia (cancer) that would affect the outcome of repair and recovery.

Once damage to the ACL was confirmed, we had to talk about repair-that meant surgery. For bigger dogs like Charlie, a trip to the surgery specialist is warranted to have a procedure called a TPLO or tibial plateau leveling osteotomy (see why we call it a TPLO?) Max only weighs about 13 pounds, so he could be a candidate for a different surgery, one we do at our hospital routinely, called a lateral imbrication procedure. In this surgery, heavy suture material, almost like fishing line, is laced along the side or sides of the stifle joint and mimics the function of the cruciate ligaments, stabilizing the motion of the joint. There should be no drawer motion remaining after these lateral imbrication sutures are placed. It is a good procedure, costs significantly less than a TPLO, and should have Max back to good weight bearing in a month or so.

We did get some x-rays of Max's stifle and saw a little piece of bone in the center of the joint. This is common in ACL ruptures as bone can come off from the point of attachment of the ligament and the joint surface. The radiologist will review the films, but the diagnosis is clear.

Max and his owner will go visit the veterinary surgery specialist for a consultation and get their recommendation for the repair of his injury. At his age (10 years) this is less likly to be a conformational issue and more a primary injury-I doubt he will have his opposite leg affected but since he is putting almost all his weight on that opposite leg, it is vulnerable to that possibility. He will be rested and put on anti-inflammatory and pain relief medications before and after his surgery. I said at the start that he is a lucky dog and I really believe that. He has a wonderful owner who is willing to take care of him, he has a good buddy, Ewoki, who watches out for him. And he has a great personality, seeming to realize that his veterinary team is trying to help him feel better-it sure makes us love our jobs all the more and want us to go out of our way to do what he and his owner need. In this case it means closing that "drawer."

Peace,
DrReneigh