Femoral Head Ostectomy and Mercy


Dr Mc Blog

June 3, 2015
She named her “Mercy”, a nod towards her future as an elementary school mascot. She was a cute little black and white ball of fluff, guaranteed part Border Collie. Part what else wasn’t mentioned. A bright puppy, Mercy suffered no fools. People wielding needles were not popular with her (picture a grown veterinarian trying to explain how vaccinations are lifesaving to a tiny puppy throwing a tantrum. Score : Puppy 1/ vet 0). By the time she’d been through all her puppy visits and spayed Mercy had had it! She began to stalk me when she saw me, sounding the alarm far and wide to all who’d listen. If I ignored her and walked away she’d bounce after me, stiff legged and barking in staccato yaps. If I turned to her she’d stop and lower her head to graciously allow me to pet her – but growled under her breath the entire time. Mercy is not good advertising for me.

Mercy takes her school duties seriously, snuggling up with children who need a friend and a furry hug while they find their way through problems. Mercy doesn’t choose sides on the playground. She has been known to dress up in ridiculous costumes for a rally or fundraiser. Most of all, Mercy can be depended upon to dispose of unwanted lunch items without tattling.

The dog has it made.

So I was a little surprised to find her in my office early one Monday morning. At a family picnic over the weekend she had joined in some doggie games and got rolled. She came up limping in back and hadn’t used the leg since, though bravely she didn’t cry. Her big brown eyes followed me quietly. After a gentle exam I recommended we start with a set of x-rays taken under sedation, so she wouldn’t feel further pain during the necessary manipulation to get good pictures of her bones.

We discovered that Mercy had dislocated her hip. The head or ball of the upper thigh bone is cupped inside a socket, called the acetabulum, of the hip. It swivels securely here, held in place by the depth of the socket and one very strong ligament.   This ball-and-socket joint allows tremendous range of motion and is very difficult to separate. Usually only blunt trauma, like hit-by-car can create a strong shearing force that breaks the ligament, yet not the bones. Mercy had not had a severe accident, but the clue to the underlying cause for her leg to succumb to a lesser injury was there on the x-ray : Mercy’s hip socket was flat, not deeply cupped. It had been so much easier for a quick blow to snap the ligament since the whole set-up was already relatively unstable. Once knocked out of place the strong thigh muscles kept the leg pulled forward.

Mercy was already under anesthesia for the x-rays, so after notifying the owner of her diagnosis we manipulated the head of her femur or thigh bone back into place. This is called a “closed” reduction of a dislocated leg (as opposed to an “open” or surgical reduction).The procedure went smoothly, probably for the wrong reasons : it was easier to pop back in place because it was more of a slide over the flattened edges of the acetabulum than a real “pop” into place. We bandaged her leg in an old fashioned sling and sent her home. On re-check 2 weeks later we found, not surprisingly, that her femur had slipped back out of place and we moved on to a salvage surgery called a femoral head ostectomy – translated backwards it means “to cut off the head of the femur”. It sounds awful and I’m surprised more people don’t faint when confronted with this description. The ligament cannot be repaired or replaced. Left alone, the ball part of the bone will grind into the pelvic bones, creating severe pain. However, remove the ball, leaving an unconnected “stick” of thigh bone but with all muscles attached and the leg will align where it should and a strong band of scar tissue called a “false joint” will form over time. Small dogs and cats will often have 100% recovery, larger dogs may exhibit a small sway to their gait. Mercy was walking on her injured leg before the sutures came out.

It’s been a couple of years now and I suspect most people have forgotten she ever had the injury. A testament to the benefits of orthopedic surgery, Mercy walks and trots just fine. (Mercy does not deign to run. A dog of her stature has no need to comport herself in such common fashion. My suggestion that a few too many corn dogs might be slowing her down was rejected with disbelief. Shame on me!).

Though Mercy continues to energetically terrorize me whenever we meet, I have one small revenge. As she has grown, it’s become obvious that very little of a Border Collie’s genes are included in her genetic makeup. In fact, while she was routing me one day I was reminded of a scene straight out of the Wizard of Oz, where a little dog of similar build bit the leg of a neighbor lady (soon to become the Wicked Witch of the West) and started that whole journey through the tornado…… I now call her “Toto” and darned if she doesn’t come running up to me for a long pet, growling the entire time. We have reached a mutual understanding and I am content.

Christine B. McFadden, DVM
Valley Animal Hospital, Merced

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