Vet360 Vet360 Volume 4 Issue 5 | Page 14

Article sponsored by Petcam ® SURGERY tem and their parts are interchangeable within their own systems. The clamps should always be placed with the clamp adjacent to the skin to limit the distance from the bone to the connecting bar. The more one increas- es the distance between skin surface and clamp, the longer the working length of the pin the higher the rate of pin loosening and implant failure. Acrylic systems are available but the bond between pin and connecting bar is not as strong or reliable as the two above-mentioned systems. Acrylic does give the advantage of being very flexible where the pins are placed and can be useful for hard to repair bones like the mandible. The most commonly used com- mercially available system is the Acrylx® from Imex. One can make a acrylic side bar from hoof acrylic and an old anaesthetic breathing tube cut to size. Connecting Bars Connecting bars are the main buttress or support of the bone while the fracture heals (figure 4). In the ex- ample of a ESF placed on the leg, they transfer the weight of the patient through the leg, through the pins, down the connecting bars and back into the foot. Bars need to be lightweight but strong enough to support the forces transferred through them for the size of the animal. Bars are made from a variety of materials, the most common being carbon fibre, stainless steel and titanium alloys. Figure 3. Circular ring fixator for a growth deformity vet360 vet360 Issue 05 | OCTOBER 2017 | 14 • • • Carbon fibre has the advantage of being radiolu- cent and allows visualisation of the fracture during healing. It is very light and in large constructs can be useful to increase mobility of the patient. How- ever they are prone to wear and tear and will need to be replaced more often. Stainless steel is heavier that carbon fibre and is radio-opaque which can impair visualisation of the fracture during healing. The advantage is they are more resistant to wear and are cheaper that carbon fibre. Titanium alloys are light, strong but more expen- sive than both carbon fibre and stainless steel. As the number of bars increase in the construct the rigidity of the construct increases. Placing cross bars further increases the stability of the construct. Can Fixators be Applied Anywhere? Yes. The reality is that they can be used in any bone anywhere in the body. There are however certain bones which they work better for. The general rule is that bones with less soft tissue coverage tolerate ESF better. They have less pin loosening and have less pin-tract complications, most commonly pin tract dis- charge. This is due less soft tissue between bone and skin rubbing on the pin and hence less reaction. Generally the tibia, radius and ulna, metatarsus and metacarpus tolerate ESF very well (Figure 5). Surpris- ingly the humerus tolerates the method well and is Figure 4. Type III ESF with crossbars