Page 446 - WSAVA2018
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 25-28 September, 2018 | Singapore
MINIMALLY INVASIVE PLATE OSTEOSYNTHESIS (MIPO)
MIPO is the application of bone plates, often in bridging fashion, without performing an open surgical approach to the fracture. MIPO is often used for highly comminuted (‘non-reducible’) diaphyseal fractures as anatomic reduction is not the goal for such fractures. Instead, “functional reduction” is the goal; also called “spatial alignment”, it restores bone length and proper alignment in the frontal, sagittal and transverse planes. Indirect reduction techniques are used to obtain this spatial alignment without opening fracture zone.
Preoperative planning for MIPO, as with MINO,
typically requires orthogonal radiographs of the intact contralateral bone using magnification calibration and templating methods to determine the optimal plate width and length. Plates that span the full bone length are often used for MIPO to reduce fixation stress; longer plates with a limited number of screws at the ends of the plate are able to sustain greater loads to failure than shorter plates in which all holes are filled with screws. Plates
are usually pre-contoured to the approximate bony contours by fitting to the bone surface on size-matched radiographs. As it is difficult to estimate the twisting contours of the bony surface from a 2-dimensional radiograph, fitting to size-matched skeleton can be very helpful. The precontoured plate is then sterilized and is ready for use at surgery.
Standard bone plates utilize screw fixation to pull the bone firmly against the underneath surface of the bone plate. Fixation, then, relies upon the strength of screw purchase and its ability to generate friction between
the bone and the bone plate. Thus, conventional bone plating requires excellent screw purchase and precise anatomic contouring of the bone plate. Many locking plate/screw systems have been introduced to the veterinary market in recent years. In brief, these systems utilize a rigid interlock between the screw and bone plate. This interaction between the fixation element (screws) and bridging element (plate) resembles the mechanical principles of an external skeletal fixator in which fixation pins are rigidly linked to the connecting rod. Thus, many have referred to locking bone plates/ screw systems as “internal fixators”, especially when used for bridging fixation. One advantage to locking plate/screw systems (compared to conventional plating) is that these plates do not require precise anatomic contouring (much like the connecting rod of external fixators is not contoured to the bone). Many of the MIPO implant systems and techniques were, consciously or not, developed to ascribe to internal fixation the many inherent advantages of external fixators.
MIO VIA EXTERNAL SKELETAL FIXATION
External skeletal fixation (ESF), though historically associated with high patient morbidity, was revolutionized by the development of advanced
devices and surgical techniques in veterinary medicine. This resurgence of interest and innovation began in
the 1990’s and continues today. Current generation techniques and instrumentation permit user-friendly application of simpler, yet mechanically robust fixation frames. This concurrent optimization of methodology and instrumentation, which fostered a profound reduction
in patient morbidity, revealed the inherent versatility and biological advantages of the system. Modern ESF includes linear, circular and hybrid external fixator devices. Linear ESF utilizes fixation pins and connecting rods, whereas circular ESF typically uses fine wires tensioned between clamps on rings placed around
the limb. Hybrid ESF has become very popular for stabilization of juxta-articular fractures and osteotomies; the linear portion of the frame is secured to the longer bone segment while the fine-tensioned wires placed on a single ring are used for fixation of the short, juxta- articular bone segment.
Modern ESF is a very versatile system that is well suited to the ideals of MIO. It provides variable angle, locked fixation that can be applied with minimal/no disruption of the fracture zone. Rigid bilateral or multi-planar frames are relatively simple to apply in instances of nonload-sharing fixation of non-reducible fractures and simple, timely, progressive frame disassembly allows for gradual shift of loading from the fixation device to the healing bone. Understanding and strict adherence to the principles of ESF are essential in order to
reduce complications and fully realize the advantages inherent to the system. Annual courses that provide comprehensive training opportunities are available in the US and elsewhere (www.imexvet.com).
Helpful Resources:
Techniques in External Skeletal Fixation – I, VideoVet 2017, www.videovet.org
Surgical Approaches of the Canine Pelvic Limb – I; VideoVet 2017, www.videovet.org
Surgical Approaches of the Canine Thoracic Limb – I; VideoVet 2017, www.videovet.org
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43RD WORLD SMALL ANIMAL VETERINARY ASSOCIATION CONGRESS AND 9TH FASAVA CONGRESS













































































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