Sacroiliac (SI) screw fixation represents an effective method to stabilise pelvic injuries. However, to date neither reliable radiological landmarks nor effective anatomical classifications of the sacrum exist. This study investigates the influence of variability in sacral shape on secure transverse SI-screw positioning. Furthermore, consistent correlations of these anatomical conditions are analysed with respect to standard planar pelvic views.
For shape analysis, 80 human computed tomography data sets were segmented with the software Amira 4.2 to obtain 3D reconstructions. We identified anatomical conditions (ACs) according to the extent of the effect on the bony screw pathway. Subsequently, the pelvis was spatially aligned using representative bone protuberances in order to create standard Matta projections. In each view, the ACs were described in terms of distance from bone landmarks.
Three-dimensional shape analysis revealed the height of the pedicular isthmus (PH) as the limiting variable for secure screw insertion. The lateral and outlet views allowed an orthogonal projection of PH. In the lateral view, the ratio of the lateral sacral triangle framed by the S1 body height and width showed a high correlation to PH (p= 0.0001). A boundary ratio of 1.5 represented a reliable variable to determine whether or not a screw can be inserted (positive predictive value: 97%). In the outlet view, the distance between the S1 endplate and the SI joint top level (EJ) strongly correlated with PH (p= 0.0001). With EJ ≤ 0 mm, screw insertion was possible in all cases (100%).
SI-screw insertion requires a well-planned procedure. Orientation of the sacral pedicle is of extreme relevance. A narrow sacroiliac channel and high sacral shape variability limit secure screw placement. However, no determining parameters exist, allowing accurate prediction of secure screw insertion based on X-rays or fluoroscopy.
The lateral sacral triangle in the lateral view represents a simple and accurate preoperative method of support for the surgeon's decision to undertake this procedure. No additional technical effort is necessary. A boundary ratio of 1.5 predicts a sufficient bone stock for at least one 7.3 mm screw. Furthermore, the evaluation of the outlet projection can be used to assess the safety of the operation. Basically, a preoperative lateral pelvic image should be mandatory.
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- CT guided percutaneous fixation of sacroiliac fractures in trauma patients.J Trauma. 2001; 51: 1117-1121
- Safe placement of S1 and S2 iliosacral screws: the “vestibule” concept.J Orthop Trauma. 2000; 14: 264-269
- The accuracy of computer-assisted percutaneous iliosacral screw placement.Clin Orthop Relat Res. 2007; 463: 179-186
- Transsacral versus modified pelvic landmarks for percutaneous iliosacral screw placement—a computed tomographic analysis and cadaveric study.Am J Orthop. 2000; 29: 16-21
- Evaluation of the upper sacrum by three-dimensional computed tomography.Am J Orthop. 1999; 28: 578-582
- Morphologic considerations of the first sacral pedicle for iliosacral screw placement.Spine. 1997; 22: 841-846
- Measurement of optimal pelvic tilt angle for iliosacral screw fixation using 3-D CT scan (Poster).in: 8th EFORT congress Florence, Italy. 2007
- Internal fixation of pelvic ring fractures.Clin Orthop Relat Res. 1989; : 83-97
- Bony sacroiliac corridor: a virtual volume model for the accurate insertion of transarticular screws.Unfallchirurg. 2008; 111: 19-26
- Minimally invasive fixation of a sacral bilateral fracture with lumbopelvic dissociation.Unfallchirurg. 2009; 112: 590-595
- S2 iliosacral screw fixation for disruptions of the posterior pelvic ring: a report of 49 cases.J Orthop Trauma. 2006; 20: 378-383
- Cross-sectional geometry of the sacral ala for safe insertion of iliosacral lag screws: a computed tomography model.J Orthop Trauma. 2000; 14: 31-35
- The effect of sacral fracture malreduction on the safe placement of iliosacral screws.J Orthop Trauma. 2003; 17: 88-94
- Early results of percutaneous iliosacral screws placed with the patient in the supine position.J Orthop Trauma. 1995; 9: 207-214
- Radiographic recognition of the sacral alar slope for optimal placement of iliosacral screws: a cadaveric and clinical study.J Orthop Trauma. 1996; 10: 171-177
- Iliosacral screw fixation: early complications of the percutaneous technique.J Orthop Trauma. 1997; 11: 584-589
- Computer-assisted versus conventional surgery for insertion of 96 cannulated iliosacral screws in patients with postpartum pelvic pain.J Trauma. 2004; 57: 1299-1302
- Neurological damage in pelvic injuries: a continuous prospective series of 50 pelvic injuries treated with an iliosacral lag screw.Rev Chir Orthop Reparatrice Appar Mot. 2004; 90: 122-131
- Percutaneous sacroiliac lag screw fixation of the posterior pelvic ring: increasing safety by standardization of visualization and insertion technique.Unfallchirurg. 2007; 110: 669-674
- Fluoroscopic positioning of sacroiliac screws in 88 patients.J Trauma. 2002; 53: 44-48
- Trans iliac–sacral–iliac bar stabilisation to treat bilateral lesions of the sacro-iliac joint or sacrum: anatomical considerations and clinical experience.Injury. 2001; 32: 587-592
- Electromyography monitoring for percutaneous placement of iliosacral screws.J Orthop Trauma. 2000; 14: 245-254
- The projection of the lateral sacral mass on the outer table of the posterior ilium.Spine. 1996; 21: 790-794
- Morphometric evaluation of the first sacral vertebra and the projection of its pedicle on the posterior aspect of the sacrum.Spine. 1995; 20: 936-940
Accepted: March 15, 2010
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