1 Introduction top
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NOTE: This procedure should only be performed by highly trained surgeons.
Lumbo-sacral dissociation is caused by high energy and is commonly associated with other fractures as well as neurological deficit.
It is essentially a multiplanar sacral fracture with vertical components, which results in detachment of the lumbo-sacral spine from the pelvic ring.
This injury can be viewed as having two primary fracture "fragments":
- The upper central sacrum and remainder of the spine
- Lower and peripheral sacrum and the attached pelvis
The sacrum is the lowest part of the spine and the fracture has the characteristics of spinal fractures.
A multidisciplinary approach is highly advisable.
For the fixation, knowledge of both spinal and pelvis fixation techniques is necessary. In cases of neurological deficit, decompression of sacral nerve roots is mandatory.
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The fixation should ideally allow early mobilization; even for patients with neurological deficits.
In cases of large displacement, reduction is difficult and great care should be taken to avoid further damage to the neurological structures.
With minimal displacement in the absence of neurological deficit, fixation in situ is recommended.
Spino-pelvic fixation allows a complete exclusion of the fractured sacrum from weight bearing.
The essence of this procedure is to provide a rigid fixation to protect healing, allow rapid mobilization and avoid pseudoarthrosis.
Although some malunion can be accepted, care should be taken to avoid significant leg length discrepancy and spinal sagittal malalignment.
2 Introduction top
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This procedure is performed with the patient placed prone through a midline or paramidline approach.
3 Neural decompression top
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If open reduction and foraminotomy are required, after exposure is completed, identify and remove small bony fragments from the comminuted fracture zone. They may be located in the transforaminal region and may hinder fracture reduction.
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The complete fracture line has to be cleaned out and inspected.
Enhance the exposure by using a lamina (bone) spreader.
Extract fragments that may compromise the sacral nerve roots.
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Additional foraminal patency can be achieved with the use of Kerrison rongeurs or high speed rotational burr to expand the nerve root channel.
4 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.
A totally unstable sacral fracture is difficult to reduce anatomically without open technique. Thus, ISS can be used after anatomic open reduction.
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.
Preliminarily fix the anatomic reduction with pointed reduction forceps.
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The contralateral side is then addressed.
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Additional reduction techniques
If needed, insert Schanz screws into both posterior iliac crests as a reduction aid for better rotational reduction.
5 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.
6 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.
7 Iliac screw insertion top
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Iliac screws are inserted in either of the three potential locations
8 Insertion of the connection rod top
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It is important that the iliac screw heads and connecting rods 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 permanent rods to the appropriate length. Attach it to the screws per the hardware system.
This technique is most reliable when reduction has already been achieved and provisionally stabilized for example with iliosacral screws. Spinopelvic fixation is therefore primarily being used as neutralization construct.
However, additional contouring of the rod may be necessary to achieve indirect reduction. This might consist of both under and over bending.
The final rod is prepared and attached to the pedicle screws bilaterally.
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The construct should be further stabilized by the insertion of 1-2 transverse connectors at the level of the sacrum.
