We moved my research rabbits to a secret secure research facility in the middle of nowhere. Then one of them died suddenly today while I was checking on her. After secondary euthanasia methods, I had to drive her dead body back to our main lab.
Poor bunny. Sad sad sad. When we have to sac all of them, I will be Very Sad.
What I learned today
On Friday, I talked about pelvic ex-fix techniques. One downside of using these for definitive management is that the patient has to walk around with some metal sticking out of their pelvis. Pin tract infection, pin loosening, and patient dissatisfaction may follow.
Today, we’re discussing a subcutaneous form of ex-fix known as a “pelvic bridge.”
I want to point out that there is another type of subcutaneous anterior pelvic internal fixator called an “INFIX” (OTA video). It looks like this:
Similar, but not quite the same.
Both are used to treat unstable pelvic ring injuries. Both can definitively manage certain fracture patterns and promote early mobilization. Both should be supported with posterior fixation.
If you want to read more about the history and who described each of these techniques, this is a funny dramatic Letter to the Editor that clarifies that story.
Anyway, back to the pelvic bridge.
Pelvic Bridge Technique
Position:
Supine on radiolucent table. Elevate sacrum with midline bolster if planning iliosacral screws posteriorly. C-arm perpendicular to table.
Approach:
Make a 5 cm incision starting at the ASIS and extending posteriorly
Dissect to the external oblique fascia and then expose the iliac crest
Make a 6-8 cm midline Pfannenstiel incision over the pubic symphysis
Dissect to the rectus abdominis fascia
Vertically incise the linea alba
Locate the pubic symphysis and tubercles
Create a subcutaneous tunnel superficial to the inguinal ligament using a periosteal or Cobb elevator
Instrumentation:
The authors use an off-label occipital cervical plate-rod construct from the Synthes spinal fusion system (4.0-mm diameter rod), Synthes Synapse system polyaxial screws (4.5 mm), and cross-links.
Contour the rod to match the iliac crest (see image). Create a ~60-degree bend to parallel the symphysis.
Photo of the hardware in place on a dissected cadaver (normally, there would still be skin and subcutaneous tissue overlying it):
The rod is inserted lateral to medial, taking care not to compress the inguinal ligament. Provisional screws can be placed at the iliac crest.
Reduction:
Options include simple manual reduction, Schanz pins used as joysticks, or a distal femoral traction pin, depending on the fracture pattern. The Schanz pins can go in the crest, posterior to the plate, or in the supra-acetabular corridor.
Fixation:
Insert a large fragment titanium screw into the plate at the iliac crest — similar to an ex-fix but “not as posterior in the gluteus medius tubercle”
Fluoro views (oblique and 15-degree external rollover from an outlet position) can be used to help assess placement
Insert 4.5-mm polyaxial pedicle screws into the pubic tubercle, similar to the trajectory used for pubic symphysis plating. Lock to the rod with a locking cap.
If a bilateral construct is needed, repeat the steps for rod placement and passage. Each rod needs at least 1 polyaxial screw into the contralateral pubic tubercle.
Finally, insert additional iliac crest screws (2 screws is typically enough but more can be used if needed)
And that’s it. If you made it to the end, congrats Keenan. I know you’re the only one who likes pelvic fractures this much.
Sources
Cole PA and Dugarte AJ. “The Pelvic Bridge” in Harborview Illustrated Tips and Tricks in Fracture Surgery 2nd Edition
Chaus, G. W. & Weaver, M. J. Anterior Subcutaneous Internal Fixation of the Pelvis: Placement of the INFIX. Operative Techniques Orthop25, 262–269 (2015).
Vaidya, R. Fixation of Anterior Pelvic Ring Injuries. Journal of the American Academy of Orthopaedic Surgeons: July 1, 2020 - Volume 28 - Issue 13 - p e550-e551. doi: 10.5435/JAAOS-D-19-00777