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Pitching a tent in the knee It’s often said that orthopaedics is like carpentry and this is true in many cases. However, I’ve also found in the past that knowledge of other disciplines is also helpful. When I was a child I was very lucky to have the world’s best dad. I know most people think this but I have to defend the title for mine obviously. I was a complete tom boy and dad let me do everything with him to do with DIY and ‘men’s jobs’. This list of jobs included pitching the tent when we went camping, which was most holidays when we were little. Dad, as I guess most dads are, is very particular about tent pitching and over the years I have observed numerous arguments break out among couples on camp sites over this meticulous, and often disastrous, procedure. However, dad has imbued in me the exact techniques that must never be strayed from. All of this stood me in good stead when I met Monty, a six-month-old Jack Russell terrier. Insanely cute and intensely aware of it, he was the sort of puppy that had everyone cooing the minute he walked, well, hobbled, through the door. He had been out tearing about in the garden and had come back in lame on one of his back legs. It wasn’t immediately obvious on examination what had happened, partly because he was also very wiggly but mostly because with such a small leg it turned out to be very difficult to decide exactly what bit was painful. I decided we would have to have him in and sedate him for a better look and feel and, very likely, an x-ray. To the uninitiated, x-rays of puppies’ skeletons can be very alarming and the first time you see one as a green vet student you look in horror at what appear to be fractures all over the place. The reason for this is the presence of growth plates. These are totally normal in young animals’ bones and do exactly what they say on the tin. Growth plates are the areas in bones from which the bones grow. Cells are laid down and then gradually ossify or turn into bone. Because of the unossified nature of the cells within the plate itself it does not show up on an x-ray like normal bone and appears as a black line- just like a fracture. This can make it very difficult to spot true fractures because the plates can be very misleading. However, in young dogs these areas are also fairly common places to get fractures because they are a line of weakness in a growing bone. In Monty’s case this turned out to be the case. He had what we call an avulsion fracture. This is where a piece of bone is pulled away from where it should be by the force of the pull of a group of muscles. X-rays showed that Monty had an avulsion of his tibial crest. This is the knobbly (in my case), pointy bit at the front of your knee at the top of your shin bone and it has a lot to deal with. The quadriceps muscle group on the front of the thigh is one of the strongest muscles of the body. It travels over the knee with the tendon in which the knee cap sits and attaches to the tibial crest. The whole force of this muscle pulling on that piece of bone is what straightens the leg. You can imagine the forces this point is under. In a growing dog there is a growth plate that effectively separates the little triangle of the tibial crest from the rest of the shin and Monty’s exuberance had pinged it very neatly off into thin air. This is where my knowledge of the forces used in pitching a tent came in. We basically had to put a tent peg in Monty’s knee. Imagine the tendon and the knee cap are your tent and the quadriceps muscle is a force ten gale. You need a good, strong peg and a solid guy rope to keep your tent firmly on the ground. An orthopaedic pin is put squarely through the tibial crest into the shin bone or tibia. A hole is drilled through the tibia a little lower down and a piece of wire called a tension band wire is placed through the hole as an anchor and fastened securely over the tent peg pin. This outfit seats the crest firmly back in place and allows the growth plate to heal, very nicely in Monty’s case, I’m glad to say. Growth plate fractures in many cases like this can heal very well because the line of the fracture simply turns into bone as it would do normally. However, they can also cause problems in some cases because the growth plates can seal too soon. If these affect the plates which are producing the length of a long bone like the radius or the tibia you can end up with one leg being shorter than the other and requiring further surgical intervention. Happily for Monty, the length of his little legs were in no danger of being affected by his avulsion and after a few weeks the little tinker was back to enjoying his naughty adolescence as all puppies should.
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