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Today's VeTerinary PracTice | november/december 2015 | tvpjournal.com a PracTiTioner's Guide To FracTure ManaGeMenT Peer reviewed 36 • As the screw is tightened, it effectively draws the far fragment toward the near fragment, applying compression across the fracture gap. • For example, to place a 3.5-mm lag screw, the cis cortex is drilled with a 3.5-mm drill bit, while the trans cortex is drilled with a 2.5-mm drill bit. IN SUMMARY Read the complete A Practitioner's Guide to Fracture Management series at tvpjournal.com: • Part 1: Diagnosing Fractures & Choosing a Fixation Technique (July/August 2015) • Part 2: Selection of Fixation Technique & External Coaptation (September/October 2015). ESF = external skeletal fxator; ILN = interlocking nail; IM = intramedullary References 1. Johnston SA, von Pfeil DJF, Dejardin LM, et al. Internal fracture fxation. In Tobias KM, Johnston SA (eds): Veterinary Surgery, Small Animal, 1st ed. Philadelphia: Elsevier, 2012. 2. Harasen G. Orthopedic hardware and equipment for the beginner: Part 1. Pins and wires. Can Vet J 2011; 52(9):1025-1026. 3. Martinez SA, DeCamp CE. External skeletal fxation. In Tobias KM, Johnston SA. Veterinary Surgery, Small Animal , 1st ed. Philadelphia: Elsevier, 2012. Orthopedic Hardware: Bone Plates & Screws Screws used to secure bone plates may be traditional or self-tapping, and are typically: ` Cortical screws for diaphyseal bone: Designed to engage cortical bone, with smaller pitch and less depth of the thread ` Cancellous screws for metaphyseal bone: Designed to engage metaphyseal or epiphyseal bone, with larger outer diameter, deeper thread, and larger pitch. Several plate types exist, including: ` Traditional plates, such as the dynamic compression plate and limited contact dynamic compression plate ` Locking plates, such as PAX plates (securos .com), ALPS plates (Kyon.ch), Synthes LCP (us.synthesvet.com), and string of pearls plates (orthomedinc.com) as well as others. With traditional plates, screws hold the plate in close contact with the bone, creating friction between the bone plate and bone and securing the construct. The axial load through the bone actually creates a shearing force at the screw– bone interface. Therefore, to minimize screw and plate failure, it is important that the plate be well contoured and ftted to the bone, with no soft tissue between the plate and bone. With locking plates, the screw heads thread into the plates, creating a locked fxed-angle system that behaves more like an ESF and does not require friction between the bone and plate. In addition, the axial force through the bone creates a compressive force at the screw–bone interface. In theory, locking plates create a stronger and stiffer construct compared with traditional plates 1 and potentially reduce the number of cortices needed for engagement to create an acceptable stable construct, eliminating the need to engage the trans cortex. However, if possible, bicortical screws should always be placed to: ` Increase strength of the construct ` Decrease likelihood for screw back out ` Resolve need for perfect plate contouring and removal of soft tissue. Other specialized plates exist for use in specifc anatomic regions, such as T-shaped plates for the proximal tibia or distal radius, L-shaped plates for the distal femur, and curved plates designed specifcally for acetabular fractures. M EREDITH K APLER Meredith Kapler, DVM, is a small animal surgical resident at North Carolina State University. She instructs veterinary students, and has presented at the Veterinary Orthopedic Society Conference and contributed to research articles and a book chapter. She received her DVM from University of Tennessee, completed a small animal internship at Virginia–Maryland Regional College of Veterinary Medicine, and completed an orthopedic research fellowship at University of Tennessee. Upon completing her residency, she will work as a staff surgeon at Veterinary Specialty Hospital of the Carolinas. D AVID D YCUS David Dycus, DVM, MS, Diplomate ACVS (Small Animal), is a staff orthopedic surgeon at the Veterinary Orthopedic & Sports Medicine Group (VOSM) just outside Washington, D.C. He has presented at national meetings and has lectured second- through fourth- year veterinary students. He has published an array of research articles and a book chapter. Dr. Dycus received his DVM from Mississippi State University, completed a rotating internship at Auburn University, and completed an MS and small animal surgical residency at Mississippi State University.