In an animal as young and rapidly growing as Spencer it was expected that the fracture should be virtually healed. Younger dogs and cats (less than 1 year-old) have the ability to heal bone injuries very rapidly – commonly between 4 to 6 weeks. Conversely, older pets tend to heal much slower and usually require more rigid fixation and may need 8 to 12 weeks (or longer in some cases) of fixation in order to heal a fracture.

Spencer was a much bigger boy when he returned 5 weeks later. He was back to his old chipper self – wanting to run, jump, and play. Radiographs were taken to assess his tibia. Figure 1 shows Spencer’s tibia from the front. As you can see from the photo, the fracture line is no longer visible. At the bottom aspect of the bone it is easy to see how much bone growth has occurred by noting that the IM pin is no longer reaching the end of the bone. Also, at the top of the bone it appears that the bone has grown over the top of the pin. This is simply an illusion created by the contour of the bone because the pin is actually sitting in front of and to the side the bone. If you notice in Figure 2 the pin is emerging from the top of the tibia.

Bone growth or lengthening of the bone occurs at the ends of the bone. Growth centers are located on each end of the bone (Fig. 3). The growth centers are known as growth plates or medically as the physis. These plates close or form solid bone as the animal ages usually before one year of age.

The bump or “swollen” area around the cerclage wire is mature callus (Fig 1 & 2). This is a build-up of new bone that heals the fracture – this type of healing is referred to as osteosynthesis or bridging osteosynthesis. Although it looks a little odd it is a very good sign. This type of bone healing occurs when there is very little disruption of the fracture and surrounding tissues during surgery. Callus can become exuberant if the fracture is not stable enough during the healing period or if significant disruption occurs during surgery. On the other hand, if the implants are overly large or stiff then minimal callus forms and in some cases the bone around the implants can even become demineralized.

However, all is well with Spencer. Spencer’s tibial fracture has a clinical union! Yahoo! Spencer is cured!! Look out world Spencer will soon be on the loose again. The next step was to remove the pin. Spencer was scheduled for surgery and the pin was removed from a small incision at the top of tibia. Implant removal is not always necessary and in some cases even contraindicated. However, with a healthy young growing cat such as Spencer it was deemed appropriate to remove the pin.

Spencer’s tibial fracture treatments are complete. He is home with his pals once again creating havoc as all little boys should. Again, we wish Spencer well and thank him for allowing us the use of his case.

Figure 3