1 Introduction top
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Triangular osteosynthesis is a subcategory of spinopelvic fixation. It combines
- lumbo-pelvic fixation ((usually unilateral) from the pedicle of L5 to the ipsilateral posterior ilium, and
- transverse sacral alar fracture fixation (iliosacral screw/s, sacral plate, etc.)
This technique offers mechanically better fixation for highly unstable, vertical shear sacral alar fractures. The lumbo-pelvic fixation, applied after reduction of the pelvic ring injury, helps prevent recurrent vertical displacement of the unstable hemipelvis.
As a result, early mobilization of the patient may be achieved, with avoidance of late deformity. However, prominent hardware, impaired healing, nerve root injury, and need for hardware removal are potential concerns. Improved techniques may reduce complication rates, especially reduction and fixation of the sacral fracture, with preliminary neural decompression, before applying distraction to the lumbo-sacral instrumentation.
For illustration purposes, we show here only the spinopelvic fixation which follows the IS screw insertion. Typically iliosacral screw fixation precedes spinopelvic fixation because of the tight anatomical constraints to iliosacral screw placement.
2 Reduction top
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ISS fixation requires an essentially anatomically reduced sacral fracture. Significant residual displacement renders this procedure unsafe.
Displacement may make it impossible to accomplish ISS fixation without causing nerve root injury or resulting in an extraosseous screw that threatens adjacent neurovascular structures.
If displacement remains significant after closed reduction, open reduction should be considered.
The typical displacements are cranial and posterior together with sagittal plane rotation.
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Preliminary fixation
Once the fracture edges have been debrided, the primary reduction maneuver typically involves the use of two pointed reduction forceps (Weber clamps).
These span from the spinous process to the lateral ilium and are used to incrementally obtain a step by step reduction by alternating translation and clamping.
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Additional reduction techniques
Preliminarily fix the anatomic reduction with pointed reduction forceps.
If needed, insert Schanz screws into both posterior iliac crests as a reduction aid for better rotational reduction.
3 Insertion of the IS screws top
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Before beginning an ISS screw fixation procedure, appropriate preoperative planning for screw type and location needs to be completed.
Following reduction, the IS screw is inserted.
4 Insertion of the pedicle screws top
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Pedicle screws are inserted bilaterally in L5 and connected with the rod. If there is concern regarding fixation to L5, then more cranial fixation levels can be added.
5 Insertion of iliac screw top
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Iliac screws are inserted in either of the three potential locations
6 Insertion of the connection rod top
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It is important that the iliac screw head and connecting rod lie flush to the bone. Avoiding prominent hardware prevents soft tissue irritation.
With a sacral entry point for the iliac screw there is less concern with screw prominence compared to iliac starting points.
Cut the rod to the appropriate length. Attach it to the screw per the hardware system.
