DIAG IM3 - Page 83

Tel +44 0845114 130258 9596 8530info@vetinst.com info@vetinst.com Dental Equipment & Instrumentation Internal Fixation15 3 Implant Selection Limited Contact Compression Plates We are often asked which plate is most suitable for a particular case. Selecting an implant of suitable strength and stiffness is vital. Too weak and an implant will fail, and too stiff an implant may delay bone healing. Templating is an essential part of the selection process and helps to guide implant selection. There may be more than one suitable plate option. When more than one plate might suit an application, one implant style may be preferable to others. There are a number of different reasons why this might be so; often the final decision will come down to individual surgeon preference, experience, and what equipment the surgeon has available. Because of their undercuts, these plates undergo a more complex manufacturing process than regular plates, making them more expensive. However, with the resultant reduced bone contact, they cause less periosteal vascular damage than regular plates, in theory facilitating more rapid bone healing. The undercuts also allow the plates to be contoured evenly, and make failure over a hole less likely. Limited contact plates can be used to create compression in the same way as dynamic compression plates. It is important that the plate chosen is sufficiently stiff and strong for its intended purpose, but not so stiff as to stress protect the bone potentially contributing to osteopenia or non-union. Stiff implants can also create significant stress risers at the end of the implant that can cause bone fracture. Here we describe a range of plates available and their differences; on the opposite page is a guide to selecting an appropriate plate for a specific fracture scenario. Locking Plates Round Hole Our stacked-hole locking design can be used with locking screws or non-locking screws. No other locking system so far tested and published, outperforms ours. Locking screws have a larger core diameter than standard non-locking cortical screws, so are stronger and stiffer than cortical screws. Locking plates have a number of advantages, i.e. excellent bone holding characteristics in poor quality bone. The plate is not compressed onto the bone therefore associated periosteal damage is avoided, accurate plate contouring is not essential, and mono-cortical screws can be used as they are angle stable Where compression cannot be achieved, round holes provide a more stable screw/plate interface than compression holes. Round holes can be spaced closer together than compression holes, which can be very useful when working with small fragments. Biological Healing Plates (BHPs) Cuttable Plates When fractures cannot be re-constructed, compression holes are unnecessary, and round holes are more stable. BHPs have a solid and stiff mid-section, designed to bridge a non-reconstructed fracture in bridging mode. Available in 1.0mm to 3.5mm sizes, the versatility of these plates lies in their close hole spacing and they can be cut to length intra-op. They are not as stiff or as strong as compression plates of the equivalent size so they are often used in conjunction with other fixation methods e.g. in combination with IM pinning, double plating including stacked plating, edge-loaded, or where elastic osteogenesis is considered advantageous. Compression/ Dynamic Compression Plates (DCPs) Cuttable Malleable Plates The dynamic compression plate has been the standard setting implant for human and veterinary orthopaedics for decades. It continues to be our most popular plate style. The design of the plate holes allows for a large range of screw insertion angles compared to round holes. Fracture compression permits primary bone healing with minimum callus. Placing a screw at the end of a plate hole furthest from the fracture will compress the fractured bone ends together as the screw is tightened. Compression plates can also be used in neutralisation and bridging modes. Care needs to be taken in bridging mode as the plate is subject to greater bending forces that can cause premature failure. Less stiff and less strong than the cuttable plates, but easy to contour in multiple directions and with close hole spacing that makes them very adaptable for non-load-bearing situations. Typically these plates would be used as neutralisation plates where the surface anatomy of the bone makes it challenging to accurately contour a regular plate e.g. the humeral condyle or the pelvis. Relatively weak plates that should only be used on small bones or in conjunction with other fixation devices. ASYM® Plates Reconstruction Plates Plate design, combining the established principles of round hole and compression plates. These are more adaptable than symmetrical compression plates and particularly suit a fracture or osteotomy scenario where one fragment is significantly smaller than the other. The round holes provide greater screw stability in the smaller fragment whilst compression can still be applied from the longer segment. Easy to contour in multiple directions, these are both stronger and stiffer than the cuttable malleable plates, but less strong and stiff than compression plates. Typically these plates are used as neutralisation plates where the surface anatomy of the bone is challenging to accurately contour a regular plate over e.g. the humeral condyle or the pelvis. 67