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tvpjournal.com | November/December 2015 | ToDay's VeTeriNary PracTice a PracTiTioNer's GuiDe To FracTure MaNaGeMeNT Peer reviewed 31 INTRAMEDULLARY PIN WITH CERCLAGE WIRE IM pin (and/or K-wire) and cerclage wire is probably one of the more common fracture fxation methods used in general practice. While cerclage wires are typically considered a method of ancillary fxation commonly used with IM pins, they can also be used with ESFs, ILNs, and bone plates. Indications IM pins resist bending loads well, but are poor at resisting rotational forces. For this reason, cerclage wires should always be added to IM pin fxation to help counteract axial and rotational forces. Cerclage wires also provide interfragmentary compression without damaging the blood supply or interfering with healing (unless they become loose). IM pins and cerclage wire fxation is limited to long oblique fractures and spiral fractures of the femur, tibia (Figure 1), and humerus. Benefts Versus Risks Advantages of IM pin and cerclage wire fxation include: • Maintenance of axial alignment • Resistance to bending loads and rotational forces • Less cost for clients • Ease of placement. Disadvantages include: • Requirement for open fracture stabilization • Failure of IM pins used alone without cerclage wire • Limited control of axial loads • Pin migration or implant failure. Technique When using IM pins and cerclage wire fxation (see Orthopedic Hardware: IM Pin & Cerclage Wire, page 32): 1. Place IM pins into the medullary cavity of long bones (femur, tibia, or humerus) with either a drill or Jacobs chuck. 2. Insert the pin in either a normograde or retrograde fashion to avoid joint surfaces. 3. With this method of fxation, the IM pin should fll approximately 70% of the medullary cavity 1 : Measure the size of the canal on radiographs and select a pin that is 70% of the cavity or, alternatively, gauge size during surgery if the canal is exposed. 4. Use a minimum of 2 cerclage wires and place them: » Approximately 1 cm apart » At least 0.5 cm from the beginning and end of the fracture line » Perpendicular to the bone shaft. 5. The cerclage wires must be tight to provide adequate interfragmentary compression. Cautions When attempting IM pin and cerclage wire fxation of the tibia: • Avoid the proximal articular surface and potential damage to the insertion of the cranial cruciate ligament; cerclage wire is also difficult to use around the tibia due to its triangular shape, which prevents placing appropriately tight cerclage. FIGURE 1. Example of IM pin and cerclage wire for fxation of a long oblique tibial fracture in an immature dog. Table 2. Selection of an Internal Fixation Technique TECHNIQUE INDICATIONS Intramedullary pin + cerclage wire • Long oblique fractures • Spiral fractures of femur, tibia, and humerus Interlocking nails Fractures in which: • The bone cannot be reconstructed (eg, comminuted fractures) • Limited bone length is available proximally or distally • Very rigid repairs are required that counteract all forces and are entirely load bearing External skeletal fxators Open contaminated fractures in which: • The open wound requires wound therapy and bandage changes • Concern exists that placing implants, such as plates or IM pins, may lead to infection, osteomyelitis and, eventually, explantation Bone plates & screws Any fracture in which there is enough bone length proximal and distal to the fracture to allow placement of 3 screws in each fragment, engaging a minimum of 6 cortices