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Sacrum and Sacral Fractures

- See:
     - Posterior Pelvic Injury:
     - Sacroiliac Fracture Dislocations:
     - Sacral Stress Fractures:

- Anatomy of Sacrum:

- Classification:
    - zone I:
           - frx across sacral ala can cause L5 nerve root impingement;
           - about 6% of these patients will have neurological injuries;
           - ref: Direct anterior decompression of L4 and L5 nerve root in sacral fractures using the pararectus approach: a technical note.

    - zone II:
           - frx thru neuroforamina can cause unilateral sacral anesthesia;
           - frx involving the neural foramina require operative debridement of frx fragments prior to reduction and fixation
                      (through posterior approch);
           - ref: Zone 2 sacral fractures managed with partially-threaded screws result in low risk of neurologic injury
    - zone III
           - frx thru body of sacrum can cause highest incidence of injury to cauda equina and result in neurogenic bladder;
           - about 56% of these patients will show neurological injuries
           - ref: Functional outcomes of Denis zone III sacral fractures treated nonoperatively.
    - misc:
           - transverse fractures;
           - U shaped fractures:
                 - results from axial loading;
                 - radiographs:
                       - bilateral transforaminal sacral fractures and irregularities, L5 transverse process frx;
                       - paradoxic inlet view: on standard AP view, the upper sacrum appears as inlet view;
                 - ref: Percutaneous stabilization of U-shaped sacral fracture using iliosacral screws: technique and early results

- Associated Injuries:
    - if the sacral fracture is impacted w/ no verticle displacement, it may represent a LC fracture (therefore look for
             anterior pelvic injury);
    - w/ vertical displacement, the sacral frx may represent a Malgaine frx equivolent;


- Physical Exam:
    - displacement in vertical plane is diagnosed by applying one hand to pelvic iliac crest and using other to apply traction to leg which
           should cause displacement in vertical plane;

- Radiology: (see outlet view);
    - sacral arcuate lines:
           - will help delineate anatomy of frx of upper sacrum;
           - sacral arcuate lines are composed of inferior surfaces of costal elements that form roofs of anterior sacral canals (foramina) &
                    neural grooves;
           - arcuate lines are easily visible on AP view of pelvis & are symmetrical;
           - asymmetry or discontinuity of sacral arcuate lines may be caused by uncomplicated sacral fracture ;
           - disorganized or marked disruption of sacral arcuate lines is indicative of comminuted sacral fracture;

- CT scan:

                  - ref: Pelvic X-ray misses out on detecting sacral fractures in the elderly - Importance of CT imaging in blunt pelvic trauma.  

- Determine Frx Stability:
      - stable fracture includes impacted vertical fracture of sacrum, nondisplaced fracture of posterior sacroiliac complex; or subtle
            fracture of upper sacrum as seen by asymmetry of sacral arcuate lines;
      - unstable frx, is characterized by frx diastasis of more than 0.5 to 1 cm, along w/ an unstable anterior injury;
      - the other question, however, is the amount of healing potential;
            - if a type I fracture reduces w/ traction, then the unstable frx would be expected to become sticky in about 4 weeks and would
                       expect complete healing in 3 months; 
      - references:
            - OTA highlight paper predicting future displacement of nonoperatively managed lateral compression sacral fractures: can it be done?
            - Nonoperative immediate weightbearing of minimally displaced lateral compression sacral fractures does not result in displacement.
            - Conservative management of transverse fractures of the sacrum with neurological features. A report of four cases.
            - Bilateral Sacral Ala Fractures Are Strongly Associated With Lumbopelvic Instability

- Surgical Approach to Fractures of the Sacrum:
    - patient is in the prone position on a flouro table;
    - similar surgical approach used for posterior approach to the SI joint
    - posteror incision is made;
    - additional vertical incision is made on opposite side;
    - sacral nerve roots & frx site are visualized by placing laminar spreader at frx site or between the two superior ilac crests;
    - decompression:
           - decompression of sacral foramina (laminectomy) is helpful for patients w/ neurologic impingment;
    - reduction:
           - sacral frx reduction is usually achieved w/ pointed reduction forceps.
           - forceps should span from spinous processes of sacrum to iliac crests;
           - assess reduction by visualization of posterior sacral lamina & palpation of the fracture through the greater sciatic notch;
           - sacral nerve roots are palpated after the reduction to be certain that they have not been entrapped;
    - fixation:
           - obtained w/ one or two screws into S1 vertebral body placed from lateral surface of the iliac wing; (similar to
                  SI joint dislocation);
                  - using flouroscopy, insert long 6.5 mm cannulated lag screws engage frx from the iliac wing to the body of S1;
           - with transforaminal fractures, use fully threaded screw to avoid compression of the sacral neural foramina
           - it may be possible to place a thin malleable plate placed across posterior sacrum from ilium to ilium as a tension band just
                  above greater sciatic notch;
    - Sacroiliac Joint Fixation - Posterior screw fixation:
           - it is important to note that malreduction of transforaminal sacral fractures will substantially decrease the space
                    available for iliosacral screws;
           - surgeon should make all efforts to reduce transforminal fractures to within 1 cm of being anatomic;
           - references:
                    - The effect of sacral malreduction on safe placement of iliosacral screws. Reilly et al. (15th Meeting of OTA  1999). 
                    - Small bowel obstruction from entrapment in a sacral fracture stabilized with iliosacral screws: case report and review of the literature.
                    - The incidence of and factors affecting iliosacral screw loosening in pelvic ring injury.

   - 4.5 mm reconstruction plate: (Albert, et al (1993));
          - indicated for posterior pelvic fractures as well as sacral fractures;
          - reconstruction plate is placed along dorsum of the sacral and through the posterior iliac spines (transiliac plate fixation);
          - patient is placed in the prone position;
          - two incisions are made over the PSIS which are perpendicular to the iliac wings, and one vertical incision is made over
                  base of the S1 spinous process;
                  - dissections are caarried down to the bony surfaces;
          - predrill the PSIS to assist w/ reconstruction plate insertion;
                  - use the 4.5 drill to make 2-3 drill holes 1 cm lateral to the PSIS;
          - an appropriately sized 4.5 mm reconstruction plate is chiseled thru the iliac spine, passed along the dorsum of the sacrum
                  to the opposite PSIS;
          - recon plate is appropriately contoured;
          - plate is fixed to the iliac wings using 6.5 mm cancellous screws, w/ two screws inserted into each ilac wing;
          - reference:
                 - Posterior Pelvic Fixation Using a Transiliac 4.5 mm Recon Plate: a clinical and biomechanical study

Sacral fractures: an important problem. Retrospective analysis of 236 cases.

Transverse fractures of the sacrum. A report of six cases.

Occult sacral fractures in osteopenic patients.

The effect of sacral fracture malreduction on the safe placement of iliosacral screws.

Triangular osteosynthesis of vertically unstable sacrum fractures: a new concept allowing early weight-bearing.

Surgical Anatomy of the Sacrum

Sacral Fractures: Current Strategies in Diagnosis and Management

Open Reduction Internal Fixation of Displaced Sacral Fractures: Technique and Results 

Can Lumbopelvic Fixation Salvage Unstable Complex Sacral Fractures?