Minimally Invasive Orthopaedic Trauma by Gardner Michael J.;Siegel Jodi;

Author:Gardner, Michael J.;Siegel, Jodi; [Tornetta III, Paul; Gardner, Michael J.; Siegel, Jodi]
Language: eng
Format: epub
ISBN: 4625683
Publisher: Wolters Kluwer
Published: 2014-08-15T00:00:00+00:00

Retrograde insertion is particularly useful in parasymphyseal fractures. Often, displacement can be reduced without direct fragment manipulation. For ramus fractures associated with a lateral compressive force mechanism and resultant internal rotation deformity, simply reducing the internal rotation with a Schanz pin in one hemipelvis will grossly realign the ramus. When additional manipulation is necessary to align the medullary canal, a small incision can be made near midline, just superior to the symphysis to allow passage of a bone hook or joker elevator. This can be used along the posterior-superior aspect of the ramus to gently reduce the unstable fragment. Caution should be used when considering this technique, as fracture displacement and hematoma associated with pelvic ring disruptions frequently displace structures from their typical location. When feasible, blunt instruments are preferred to minimize risk to the bladder or vascular structures as they exit the pelvis just medial to the iliopectineal fascia. When the medial fragment is displaced, it may be able to be manipulated via the intramedullary drill once it has been used to get access to the parasymphyseal ramus. The 2.5-mm calibrated drill bit or the 2.8-mm guidewire are frequently too flexible to be used as manipulative instruments. The 3.5- or 4.5-mm drill are more stout and can be used to joystick the ramus into position, and allow temporary stabilization with a wire placed remote from planned screw position. Alternatively, it is occasionally helpful to overdrill the near medullary canal with a cannulated drill, use it to reduce the ramus, and then advance the guidewire by tapping through the drill into the far fragment. The drill can then be removed, the wire left in place, and the cannulated screw inserted over the guidewire. This technique requires that the patient anatomy can accommodate a large caliber cannulated screw.

There is considerable variability in the morphology of the anterior pelvis. Some rami are narrow, or tortuous, and will not accommodate safe screw insertion. Implants should be adjusted for patient anatomy. When a 6.5 mm or larger cannulated screw is not feasible, a 4.5- or 3.5-mm cortical screw can be used, as these screws will often flex and bend to pass the narrow, curved intraosseous, extra-articular corridor that exists between the symphysis and the lateral ilium.

Other patients have bony anatomy that will allow screw passage, but the necessary trajectory for retrograde insertion may not be anatomically possible. This can be due to several factors, including the relative extension or flexion of the pelvis in the body or large thighs. Antegrade insertion should be considered in these instances. It is helpful to be proficient at each technique, as it is not uncommon to use intramedullary stabilization bilaterally, and placing one screw retrograde, and the other antegrade can eliminate the need for routine c-arm repositioning to the opposite side of the bed, which risks compromising sterility. Repositioning is necessary because the c-arm arc interferes with the surgeon when obtaining the inlet view for antegrade insertion and when obtaining the obturator-outlet view for retrograde insertion, if the surgeon is on the same side of the table as the c-arm machine.

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