Page 445 - WSAVA2018
P. 445

R. Palmer1
1Colorado State University, Clinical Science, Fort Collins, USA
The primary goal of all fracture treatment is restoration of normal limb function and we must never lose this focus. Surgical repair of fractures can be performed with open reduction & fixation (ORF) or minimally invasive osteosynthesis (MIO). When properly performed on carefully selected patients, MIO can restore normal limb function, but often with faster bone healing times and with less perioperative patient morbidity than associated with ORF. Morbidity concerns such as postoperative swelling, pain and incisional complications can often
be reduced by virtue of the less aggressive surgical approaches.
Just as MIO has inherent advantages, it also has some disadvantages that must be respected in case selection. First, there is a significant learning curve associated with the development of these skills. Most veterinarians are accustomed to visualization of the fractured bone for implant insertion, implant contouring, and restoration of bony alignment, etc; MIO often requires more training and advance planning. The inability to directly visualize the entire bone may result in fracture mal-alignment in some instances, especially for those inexperienced in MIO. Similarly, the inability to fully visualize the affected bone may result insufficient fixation. Intraoperative imaging using a fluoroscopic imaging (C-arm) unit is tremendously helpful for most (but not all) MIO fracture treatments. Such imaging represents a significant additional hospital expense and a source of radiation exposure to the patient and hospital staff. Such imaging may be less essential for some external skeletal fixation applications.
Surgical fixation is indicated for SI luxation when one or more of the following clinical or radiographic signs are present: 1) significant instability and displacement of the hemi-pelvis, 2) neurologic deficits or pain attributable to the luxation or 3) obstruction/collapse of the pelvic canal. Surgical fixation can be achieved by open reduction
and internal fixation (ORIF) or minimally invasive osteosynthesis (MIO). ORF induces some morbidity associated with the surgical approach and traction for visualization of the articular surface of the sacral body.
Your Singapore, the Tropical Garden City
MIO for SI luxations utilizes percutaneous reduction and fixation that drastically reduces the patient morbidity associated with open surgical exposure and reduction. Studies by Bowlt, Shales and Langley-Hobbs have
also made it clear that the “safe corridor” for lag screw fixation is relatively small and that there is considerable anatomic variation between patients that can challenge or preclude accurate and secure fixation when ORF is employed. While intraoperative imagingisrequired for MIO of SI luxation, this imaging simplifies the surgical procedure and improves fixation accuracy. Accurate application of fixation implants is important due to the proximity of important neural and vascular structures and it ensures optimal fixation strength.
Tomlinson, et al nicely described the technique for
MIO of SI luxations under fluoroscopic guidance in
the dog. Patients are positioned in lateral recumbency upon the surgical table and this position is adjusted
until thefluoroscopic appearance of superimposition
of the transverse processes of the lumbar vertebrae and a distinct triangular shape of the sacral body confirms perfectlaterality. The luxation is reduced via percutaneous application of bone forceps on the ilial wing and/or ischium. Provisional fixation is achieved with a k-wire placed from the ilium into the sacral body using fluoroscopic guidance. Next, 1 or 2 screws are placed
in lag fashion using the same intraoperative imaging technique. Because of the need for such imaging, the surgery table should have a radiolucent surface and operating room personnel should adhere to appropriate radiation safety guidelines.
Interlocking nails (ILN) are specifically designed intramedullary devices with transverse cannulations that accept fixation bolts. The intramedullary nail imparts resistance to disruptive bending forces while the rigid interlock of the fixation bolts within the nail cannulations on each side of the fracture or osteotomy imparts stability against axial compression and rotational forces. Since these nail cannulations cannot be visualized after the
nail is placed within the intramedullary canal, a specific aiming guide system is part of the instrumentation set
to ensure accurate placement of the fixation bolts.
With technical training and acquired expertise, the nail and fixation bolts can often be placed percutaneously without disruptive of the fracture zone. Recent advances in veterinary ILN devices offer enhanced fixation
strength imparted by angle-stable fixation bolts (i-LocÒ, BioMedtrix, Whippany, NJ). Normograde insertion of ILN is the only option for MINO. MINO is an option for many highly comminuted (non-reducible) femoral, humeral and tibial fractures. Preoperative planning typically includes orthogonal radiographs of the intact contralateral bone using magnification calibration and templating methods to determine the optimal nail diameter and length.

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