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Anterior penetration of an iliosacral screw through the sacral ala would most likely lead to weakness of which of the following movements?
Great toe dorsiflexion
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Penetration of an iliosacral screw through the sacral ala would injure the ipsilateral L5 nerve root (great toe dorsiflexion). This can be avoided with proper understanding of the sacral anatomy as well as iliosacral screw starting points. The three required views for placement of this screw are: lateral sacral, pelvic inlet, and pelvic outlet.
The referenced study by Ziran et al is an excellent review of fluoroscopic evaluation of screw placement. They reported that the anterior border of the S1 body is best seen with overlap of the S1 and S2 anterior cortex while the superior aspect of the S1 foramen is best seen with overlap of the S2 foramen on the superior pubic ramus.
The referenced study by Routt et al reviewed 177 patients with pelvic ring injuries treated with these screws and found that quality triplanar imaging decreased intraoperative and postoperative complications. They also recommend supplemental fixation of iliosacral screws with posterior plating in noncompliant patients.
Routt ML Jr, Simonian PT, Mills WJ.
J Orthop Trauma. 1997 Nov;11(8):584-9. PMID: 9415865 (Link to Abstract)
Routt, JOT 1997
Ziran BH, Wasan AD, Marks DM, Olson SA, Chapman MW
J Trauma. 2007 Feb;62(2):347-56; discussion 356. PMID: 17297324 (Link to Abstract)
Ziran, JTACS 2007
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Average 4.0 of 24 Ratings
If a percutaneous iliosacral screw is placed too anteriorly, and the screw exits anterior to the sacral ala before re-entering the sacral body, what will be the most likely finding postoperatively?
Lack of ankle dorsiflexion
Lack of ankle plantarflexion
Lack of knee extension
Loss of bowel and/or bladder control
Lack of great toe extension
This question is a simple review of anatomy and nerve innervation. The L5 root is at risk with an "in-out-in" screw, as described in the question, as the nerve root is just anterior to the sacral ala as it enters the true pelvis. L5 is primarily evaluated by extensor hallucis longus function. L4 is tested with tibialis anterior function and S1 by gastroc-soleus function (ankle plantarflexion).
Average 4.0 of 30 Ratings
A 39-year-old male is thrown from his motorcycle into a fast-food restaurant and sustains a closed pelvic ring injury. During placement of percutaneous iliosacral screws, the outlet radiograph in Figure A is obtained. What purpose does this view serve?
Evaluation of possible injury to L5 nerve root
Evaluation of anterior-posterior position of screw(s)
Best visualization of sagittal curvature of sacral ala
Best visualization of spinal canal
Best visualization of sacral neural foramina
Figure A shows an intraoperative outlet view, which provides the best visualization of the neural foramina (and possible screw placement into these foramina). This view provides information regarding cephalad-caudad placement of the screw, whereas the inlet view provides information regarding the anterior-posterior position of the screw. The lateral sacral view provides information regarding the sagittal curvature of the sacral ala and gives information regarding possible iatrogenic L5 nerve injury as it goes over the sacral ala.
The referenced article by Routt et al is a review article regarding the safety and techniques of percutaneous pelvic ring fixation.
Routt ML, Nork SE, Mills WJ
Clin. Orthop. Relat. Res.. 2000 Jun;(375):15-29. PMID: 10853150 (Link to Abstract)
Routt, CORR 2000
Average 3.0 of 30 Ratings
A 32-year-old female sustains the injury shown in Video A. The right-sided pelvic injury is best classified as which of the following?
Lateral compression 1
Lateral compression 2
Anterior-posterior compression 2
Anterior-posterior compression 3
The injury shown in Video V reveals a right sided posterior ilium fracture, which is known as a crescent fracture. The presence of a crescent fracture is consistent with a lateral compression type 2 injury; this differentiates this from a type I injury. The ipsilateral anterior sacrum has a small impaction injury anteriorly while the contralateral SI joint has a minor amount of anterior sacral impaction indicative of a lateral compression type I injury.
The reference by Burgess et al is the primary source of the mechanism classification of pelvic ring injuries. Overall blood replacement averaged 5.9 units (lateral compression, 3.6 units; anteroposterior compression, 14.8 units; vertical shear, 9.2 units; combined mechanical, 8.5 units). Overall mortality was 8.6% (lateral compression, 7.0%; anteroposterior, 20.0%, vertical shear, 0%; combined mechanical, 18.0%).
1: The presence of a crescent fracture means this is at least a LC-2 injury. The left-sided fracture pattern is consistent with an LC-1 pattern.
3: A vertical shear fracture pattern would exhibit some vertical displacement and does not typically exhibit the crescent fragment.
4: The fracture pattern does not match an anterior-posterior compression pattern.
5: The fracture pattern does not match an anterior-posterior compression pattern.
Burgess AR, Eastridge BJ, Young JW, Ellison TS, Ellison PS, Poka A, Bathon GH, Brumback RJ
J Trauma. 1990 Jul;30(7):848-56. PMID: 2381002 (Link to Abstract)
Burgess, ICL 1990
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