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tvpjournal.com | November/December 2015 | ToDay's VeTeriNary PracTice a PracTiTioNer's GuiDe To FracTure MaNaGeMeNT Peer reviewed 33 at each end; furthermore, the hourglass shape allows for increased vascularity of the diaphyseal medullary canal. In multiple studies, this newer, angle-stable ILN was shown to be stronger and result in faster healing compared with traditional ILNs (Figure 2). 1 Cautions Bolts are superior to screws, which are more likely to break due to a stress riser—a location in an object where stress is concentrated—between the head and neck of the screw. Earlier generation ILNs have also been shown to have a higher rate of breakage or bending compared to newer, angle-stable ILNs. 1 EXTERNAL SKELETAL FIXATION External skeletal fxation involves transcutaneous placement of threaded pins or wires into fracture fragments; these pins or wires are then stabilized externally with clamps and rods or epoxy. • Linear external fixators are created by using Orthopedic Hardware: Linear ESF Linear ESF confgurations can be classifed based on pin and rod placement, including the number of planes the pins pass through in space, and how many skin surfaces are penetrated (Table 3). ` Pins should be positive profile pins—those with threads rolled onto the core diameter of the pin, creating an inner diameter of the threaded region equal to the shaft diameter and eliminating a stress riser effect. ` Avoid negative profile pins—in which the thread is machine cut into the pin shaft creating an inner diameter of the threaded region smaller than the shaft diameter—due to their considerable weakness at the pin thread interface. ` Avoid smooth pins—those with no threads—which have considerably less holding power. If smooth pins must be used, they should be angled at least 70° to the bone to improve holding power. Table 3. Classifcation of ESF Confgurations TYPE CONSTRUCT HARDWARE DESCRIPTION Type Ia Unilateral uniplanar 1 connecting bar Half pins Least rigid construct available but sometimes appropriate for puppy greenstick fractures (Figure 3A) Type Ib Unilateral biplanar Increased stability relative to Type Ia due to additional pins across 2 planes ( Figure 3A) Type IIa Bilateral uniplanar 2 connecting bars IIa: Full pins IIb: Half & full pins At least 2 pins that pass fully through the bone, with connecting rod on each end (Figure 3B) Type IIb Bilateral uniplanar At least 2 pins passing fully through the bone, but not all pins penetrate the skin adjacent to the far (trans) cortex ( Figure 3B) Type III Bilateral biplanar 3 connecting bars Full pins Typically arranged in triangular formation, with connectors between 3 individual rods (Figure 3C); very rigid construct FIGURE 3. ESF classifcation: Differences between Types Ia and Ib (A) and Types IIa and IIb (B), and depiction of Type III (C). a b C