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Shota Tamagawa, Takatoshi Okuda, Hidetoshi Nojiri, Tatsuya Sato, Rei Momomura, Yukoh Ohara, Takeshi Hara, and Muneaki Ishijima

, 28 , 29 which is not practical for use as a reference to prevent iatrogenic L5 nerve root injury when inserting the sacral screws under intraoperative fluoroscopy due to differences in patients’ body sizes. To our knowledge, there have been no previously published reports that investigated the running angles of the L5 nerve root in the pelvis. Anatomical knowledge of the L5 nerve root in the pelvis is essential for safe and effective placement of the sacral screw. This cadaveric study aimed to investigate the course of the L5 nerve root in the pelvis and to

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Laura Bloom, S. Shelby Burks, and Allan D. Levi

presacral and posterior drainage. Case Report A 61-year-old man, a nonsmoker with a medical history of hypertension and asthma, originally presented with intractable low-back pain and leg pain on the right side in an L-4 distribution. Admission CT and MRI scans revealed an L3–S1 spondylosis with multilevel lateral recess stenosis. The patient underwent laminectomies from L-3 to S-1, with bilateral facetectomies and foraminotomies from L-3 to S-1. Pedicle screws were placed bilaterally from L-3 to S-1 with bicortical sacral screws ( Fig. 1A ). Local bone

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Joseph C. Hsieh, Doniel Drazin, Alexander O. Firempong, Robert Pashman, J. Patrick Johnson, and Terrence T. Kim

revision screws, 29 were considered good, 3 (8.3%) fair, and 4 (11.1%) poor. Revision sacral screws had the highest rate of poor placement (0% primary vs 11.1% revision, p = 0.107). Each of the screws categorized as fair and poor in revision cases were due to longer length rather than sidewall breach. Rates of good pelvic screws trended toward better in primary than in revision cases, but were not significantly different (87.5% primary vs 72.2% revision, p = 0.393). Each of the fair pelvic screws (27.8% revision vs 12.5% primary) was classified as fair due to medial

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Edward C. Benzel and Perry A. Ball

predominantly cancellous bone. Furthermore, the quality and quantity of surface area of contact between the implant and the bone is often suboptimum, especially at screw—bone junctures. Cutout and loss of deformity correction are the causes of failed pedicle screw constructs if short segment fixation is used for these injuries. The moment arm can be lengthened caudally for fixation by incorporating the S-2 dorsal neuroforamina and the S-1 lamina. However, sacral screw fixation below S-1 is tenuous, at best. It is in this context that dorsosacral anatomical relationships

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Martin James Wood and Richard John Mannion

series were from 1 screw that was positioned inferiorly at L-5, partly within the L-5 nerve root foramen but without nerve stimulation electrophysiologically or clinically, and the 2 overly long sacral screws, 1 of which caused lumbosacral trunk impingement. This patient with lumbosacral trunk injury underwent surgery early in our series and the sacral screw trajectory was too straight, in addition to the screws being too long. This therefore resulted in perforation of the anterior sacral cortex at the promontory–ala junction, with impingement on the lumbosacral trunk

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Jakub Godzik, Bernardo de Andrada Pereira, Anna G. U. Sawa, Jennifer N. Lehrman, Randall J. Hlubek, Brian P. Kelly, and Jay D. Turner

strain gauges (EA-06-031CE-350, Vishay Micro-Measurements) were fitted to the sacral screws near the screw heads, evenly spaced circumferentially and positioned in line with the long axis of the screws. The gauges were calibrated on each screw before implantation to determine strain versus screw bending moment associations. 19 The posterior rods were fixed with two uniaxial strain gauges (EA-06-031CE-350) midway between L4–5 and L5–S1 ( Fig. 2A–D ) facing the posterior aspect of the rod and measuring the strain along the longitudinal axis of the rod. The accessory rod

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Bryan W. Cunningham, Paul D. Sponseller, Ashley A. Murgatroyd, Jun Kikkawa, and P. Justin Tortolani

throughout the testing procedures. Specimen Reconstruction: Construct Testing Sequence Following preparation, the 21 lumbopelvic specimens were randomized into the 3 treatment groups: S1–2 sacral screws (n = 7), S1–sacral alar iliac screws (n = 7), and S1–iliac screws (n = 7). Multidirectional flexibility testing was performed on the intact, prefatigue, and postfatigue reconstruction conditions, and the S1–iliac screw group was evaluated with both unilateral and bilateral iliac fixation to assess the kinematic differences of one versus two iliac screws. Transpedicular

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Rajiv Saigal, Darryl Lau, Rishi Wadhwa, Hai Le, Morsi Khashan, Sigurd Berven, Dean Chou, and Praveen V. Mummaneni

Object

Long-segment spinal instrumentation ending at the sacrum places substantial biomechanical stress on sacral screws. Iliac (pelvic) screws relieve some of this stress by supplementing the caudal fixation. It remains an open question whether there is any clinically significant difference in sacropelvic fixation with bilateral versus unilateral iliac screws. The primary purpose of this study was to compare clinical and radiographic complications in the use of bilateral versus unilateral iliac screw fixation.

Methods

The authors retrospectively reviewed 102 consecutive spinal fixation cases that extended to the pelvis at a single institution (University of California, San Francisco) in the period from 2005 to 2012 performed by the senior authors. Charts were reviewed for the following complications: reoperation, L5–S1 pseudarthrosis, sacral insufficiency fracture, hardware prominence, iliac screw loosening, and infection. The t-test, Pearson chi-square test, and Fisher exact test were used to determine statistical significance.

Results

The mean follow-up was 31 months. Thirty cases were excluded: 12 for inadequate follow-up, 15 for lack of L5–S1 interbody fusion, and 3 for preoperative osteomyelitis. The mean age among the 72 remaining cases was 62 years (range 39–79 years). Forty-six patients underwent unilateral and 26 bilateral iliac screw fixation. Forty-one percent (n = 19) of the unilateral cases and 50% (n = 13) of the bilateral cases were treated with reoperation (p = 0.48). In addition, 13% (n = 6) of the unilateral and 19% (n = 5) of the bilateral cases developed L5–S1 pseudarthrosis (p = 0.51). There were no sacral insufficiency fractures. Thirteen percent (n = 6) of the unilateral and 7.7% (n = 2) of the bilateral cases developed postoperative infection (p = 0.70).

Conclusions

In a retrospective single-institution study, single versus dual pelvic screws led to comparable rates of reoperation, iliac screw removal, postoperative infection, pseudarthrosis, and sacral insufficiency fractures. For spinopelvic fixation, placing bilateral (vs unilateral) pelvic screws produced no added clinical benefit in most cases.

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Neurosurgical Focus FOC 1092-0684 American Association of Neurological Surgeons 10.3171/2016.4.FOC-LSRSabstracts 2016.4.FOC-LSRSABSTRACTS Abstracts RF Paper 21. Lumbopelvic Fixation Provides Better Fixation Than One Trans-Sacral Screw in Complex Sacral Fractures Ehsan Jazini , MD 1 , Noelle Klocke , MS 2 , Oliver Tannous , MD 1 , Tristan Weir , BS 1 , Herman Johal , MD, PhD 1 , Daniel Gelb , MD 1 , Jascone Nascone , MD 1 , Robert O'Toole , Md 1 , Brandon Bucklen

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Keitaro Matsukawa, Yoshiyuki Yato, Takashi Kato, Hideaki Imabayashi, Takashi Asazuma, and Koichi Nemoto

sacrum, which mainly consists of cancellous bone. 5 , 15 , 21 To obtain more rigid fixation, screws can be placed bicortically, with purchase into the anterior cortex or the sacral promontory (tricortically), 11 , 25 but there is still the potential risk of neurovascular injuries anteriorly. 6 , 7 , 15 To overcome these disadvantages, a more rigid, safe, and well-balanced sacral pedicle screw trajectory is needed for combination with the CBT screws. In this study, we introduce a novel sacral screw trajectory, which maximizes engagement with denser bone by the screws