Safe Zones for Spinopelvic Screws in Patients With Lumbosacral Transitional Vertebra.

STUDY DESIGN: Retrospective matched-pair analysis. OBJECTIVES: Lumbosacral transitional vertebrae (LSTV) have a reported prevalence of 4-36% in the population. The safe zones for screw placement for spinopelvic fusion in adult spinal deformity surgery for patients with LSTV have not been described in the literature. Our study aimed to assess the safety of S1-pedicle screw (S1PS), S2-alar screw (S2AS), S2-alar-iliac screw (S2AIS), and iliac screw (IS) placement in patients with LSTV. METHODS: Out of the 819 examined patients, 49 patients with LSTV were included in our retrospective analysis with a matched pair control group. We used the 3-dimensional planning tool mediCAD for screw placement of S1PS, S2AS, S2AIS, IS with different angles, length and diameters. RESULTS: We evaluated a total of 10 192 screw trajectories. No serious complications occurred due to the trajectories used for S1PS. LSTV increased the risk of vessel injury for S2AS trajectories (P = .001) but not for S2AIS (P = .526). Besides the presence of an LSTV, the screw trajectory had a major influence on the frequency of serious complications. CONCLUSIONS: Sacral anchoring of long spinal constructions using S1PS, S2AS, S2AIS and IS is also possible in the presence of LSTV. For S2AS the trajectory with 30° lateral and caudal angulation of 10° showed the least vascular injuries and the least sacro-iliac-joint violations in patients with LSTV. S2AIS trajectories with 40° lateral and 0° sagittal angulation reduced the risk of serious complications in our patients collective with LSTV.

Minimally Invasive "Crab-Shaped Fixation" for Treating Patients with Fragility Fractures of the Pelvis.

INTRODUCTION: In the aging society, fragility fracture of the pelvis (FFP) has become a problem. Although strong and minimally invasive fixation is required in FFP surgery, reports on relevant surgical results are scarce. Crab-shaped fixation (CSF) is a spinopelvic fixation that involves reconstruction of the posterior pelvic ring using spinal instrumentation. This study aimed to evaluate the walking ability and perioperative complications of patients who underwent CSF for FFP. METHODS: We included patients diagnosed with unstable FFPs, including sacral fracture, who required hospitalization. Demographic data, such as age, sex, bone mineral density, and Rommens classification, were evaluated. Surgical findings included estimated blood loss, operation time, and perioperative complications. The improvement in postoperative walking ability was evaluated based on the length of the postoperative period before the initiation of walker training and whether walking aids were required at 6 months post-surgery, compared with those who received conservative treatment for FFP. RESULTS: Our study included 6 cases that received CSF and 16 cases that received conservative treatment, in which all were females and presented with sacral fractures. The average age of the surgical patients, the operation time, and the estimated blood loss were 79.5±14.7 years, 180.7±28.7 min, and 124.2±29.4 mL, respectively. The average length of the postoperative period prior to the initiation of walker training was 10.8±12.3 days, which was significantly shorter than that of conservative treatment. With regard to perioperative complications, poor reduction of fracture dislocation was observed in one case as well as surgical site infection in another case, but the walking ability improved in all cases. CONCLUSIONS: We evaluated the results of the posterior pelvic ring reconstruction with CSF for patients with vertically unstable FFPs, including sacral fractures. CSF is minimally invasive and would be useful as it allowed walker training during the early postoperative period, which improved patients' walking ability even during the in situ pelvic ring reconstruction.

Pull-out strength evaluation of cement augmented iliac screws in osteoporotic spino-pelvic fixation.

INTRODUCTION: Spino-pelvic fixation has been widely accepted for surgical treatment of sacral tumor, scoliosis surgery and pelvic fractures. Cement augmentation of screws is an option to improve implant stability in osteoporotic bone quality. Aim of the present study is to compare iliac screw fixation without cement fixation and two cement application options in a biomechanical testing. HYPOTHESIS: Cement augmentation of iliac screws leads to superior pull-out strength. MATERIAL AND METHODS: Thirty female and osteoporotic human iliac bones were used. Three operation treatment groups were generated: Screw fixation (cannulated screws) without cement augmentation [Operation treatment (OT) A], screw fixation with cement augmentation before screw placement (cannulated screws) (OT B) and screw fixation with perforated screws and cement augmentation after screw placement (OTC). Pull-out tests were performed with a rate of 6mm/min. A load versus displacement curve was generated. Maximum pull-out force (N) was measured in the load-displacement curve. RESULTS: Paired group 1 (OT A vs. OT B): Screw fixation without cement augmentation: 592.6N±335.07 and screw fixation with cement augmentation before screw placement: 996N±287.43 (p=0.0042). Paired group 2 (OT A vs. OT C): screw fixation without cement augmentation: 716.2N±385.86 and fenestrated screw fixation with cement augmentation after screw placement: 1324.88N±398.76 (p=0.0489). Paired group 3 (OT B vs. OT C): Screw fixation with cement augmentation before screw placement: 1077.2±486.66 and fenestrated screw fixation with cement augmentation after screw placement: 1298.2N±726.19 (p=0.3286). DISCUSSION: Regarding iliac screw fixation for spino-pelvic ostesynthesis in osteoporotic bone, cement augmentation is significantly superior to solid iliac screw fixation respecting pull-out-strength. Nevertheless, further biomechanical studies are needed to verify these findings. LEVEL OF EVIDENCE: Not applicable; biomechanical cadaver study.

Minimally invasive spinopelvic "crab-shaped fixation" for unstable pelvic ring fractures: technical note and 16 case series.

BACKGROUND: Unstable sacral fractures are high-energy injuries and comprise polytrauma. Internal fixation to enable withstanding vertical loads is required to get up early from the bed after an unstable sacral fracture. We developed a new minimally invasive surgical (MIS) procedure for unstable pelvic ring fractures and reported it in Japanese in 2010. We presented our minimally invasive surgical technique of crab-shaped fixation for the treatment of unstable pelvic ring fractures and report on its short-term outcomes. METHODS: Sixteen patients with unstable pelvic ring fractures (AO types C1, 2, and 3) were treated using crab-shaped fixation. All procedures were performed with the patient in the prone position through 5-cm skin incisions created bilaterally at the level of the posterior superior iliac spine. Four iliac screws were inserted and connected with two rods under the fascia. Percutaneous pedicle screws were inserted at L5 or L4 and connected to the iliac rod using offset connectors. Fracture reduction was then performed. RESULTS: The average surgical time was 158 min (range, 117-230 min), with an intraoperative bleeding volume of 299 ml (range, 80-480 ml). Thirty-three pedicle screws and 64 iliac screws were implanted with no instance of malpositioning or perforation. A surgical site infection developed in 2 of the 16 cases. Both were deep methicillin-resistant Staphylococcus aureus infections, with the removal of the distal implants required in only one of these cases. Bony union was achieved in all patients, and all vertical displacements reduced by 7.0 mm, on average (range, 5.4-9.0 mm), to < 10 cm. Correction was retained in all cases. CONCLUSIONS: Crab-shaped fixation provides a feasible MIS approach for spinopelvic fixation, which allows good reduction of the vertical displacement of unstable pelvic ring fractures and bony union.

Fluoroscopy only for the placement of long iliac screws: A study on 14 patients.

BACKGROUND: Iliac screw placement is challenging due to the particular anatomy of the ilium. Most series have reported the use of relatively short (≤90 mm in length) screws despite a long iliac buttress, which has an average length of 129 mm in females and 141 mm in males. This study describes a series of 14 patients who underwent placement of long iliac screws (≥100 mm in length) as part of a spinopelvic fusion utilizing fluoroscopy alone. METHODS: All patients who received at least one long iliac screw were included in this study. Placement accuracy, the average distance from the screw tip to the anterior inferior iliac spine (AIIS), neurovascular injuries, acetabulum and/or sciatic notch violations, and screw prominence were all measured. RESULTS: Fourteen patients received 38 iliac screws, with 31 screws being ≥100 mm in length. The accuracy rate was 87.1% (27/31) for the long iliac screws. The average shortest distance from the iliac screw tip to the AIIS was 15.5 mm for the right-sided and 17.1 mm for the left-sided ilia. There were no neurovascular injuries, acetabulum, or sciatic notch violations, and no screws loosened or fractured. Of interest, only one patient required off-set connectors to link the rods to the iliac screws. CONCLUSIONS: Placement of long iliac screws under intraoperative fluoroscopy only was shown to be feasible, with a high accuracy rate and few complications, in this series of patients.

Spino-Pelvic Fixation in Unstable Sacral Fracture: A Case Report

A 22-year-old female patient visited the emergency room (ER) after a pedestrian traffic accident in a drunken state. An examination at the ER revealed fractures at the right side of the sacral ala, sacral foramina, left anterior acetabulum, right inferior ramus, and right superior articular process of S1. She underwent spino-pelvic fixation and iliosacral (IS) screw fixation. One year later, bone union was completed and implant removal was performed and the treatment was completed without complications. The authors recommend spino-pelvic fixation and IS screw fixation for unstable sacral fractures as one of the excellent methods for obtaining posterior stability of the pelvis among the various treatments of unstable sacral fractures.

Free Hand Insertion Technique of S2 Sacral Alar-Iliac Screws for Spino-Pelvic Fixation: Technical Note, Acadaveric Study.

A rigid spino-pelvic fixation to anchor long constructs is crucial to maintain the stability of long fusion in spinal deformity surgery. Besides obtaining immediate stability and proper biomechanical strength of constructs, the S2 alar-iliac (S2AI) screws have some more advantages. Four Korean fresh-frozen human cadavers were procured. Free hand S2AI screw placement is performed using anatomic landmarks. The starting point of the S2AI screw is located at the midpoint between the S1 and S2 foramen and 2 mm medial to the lateral sacral crest. Gearshift was advanced from the desired starting point toward the sacro-iliac joint directing approximately 20° angulation caudally in sagittal plane and 30° angulation horizontally in the coronal plane connecting the posterior superior iliac spine (PSIS). We made a S2AI screw trajectory through the cancellous channel using the gearshift. We measured caudal angle in the sagittal plane and horizontal angle in the coronal plane. A total of eight S2AI screws were inserted in four cadavers. All screws inserted into the iliac crest were evaluated by C-arm and naked eye examination by two spine surgeons. Among 8 S2AI screws, all screws were accurately placed (100%). The average caudal angle in the sagittal plane was 17.3±5.4°. The average horizontal angle in the coronal plane connecting the PSIS was 32.0±1.8°. The placement of S2AI screws using the free hand technique without any radiographic guidance appears to an acceptable method of insertion without more radiation or time consuming.

Free Hand Insertion Technique of S2 Sacral Alar-Iliac Screws for Spino-Pelvic Fixation: Technical Note, Acadaveric Study

A rigid spino-pelvic fixation to anchor long constructs is crucial to maintain the stability of long fusion in spinal deformity surgery. Besides obtaining immediate stability and proper biomechanical strength of constructs, the S2 alar-iliac (S2AI) screws have some more advantages. Four Korean fresh-frozen human cadavers were procured. Free hand S2AI screw placement is performed using anatomic landmarks. The starting point of the S2AI screw is located at the midpoint between the S1 and S2 foramen and 2 mm medial to the lateral sacral crest. Gearshift was advanced from the desired starting point toward the sacro-iliac joint directing approximately 20degrees angulation caudally in sagittal plane and 30degrees angulation horizontally in the coronal plane connecting the posterior superior iliac spine (PSIS). We made a S2AI screw trajectory through the cancellous channel using the gearshift. We measured caudal angle in the sagittal plane and horizontal angle in the coronal plane. A total of eight S2AI screws were inserted in four cadavers. All screws inserted into the iliac crest were evaluated by C-arm and naked eye examination by two spine surgeons. Among 8 S2AI screws, all screws were accurately placed (100%). The average caudal angle in the sagittal plane was 17.3+/-5.4degrees. The average horizontal angle in the coronal plane connecting the PSIS was 32.0+/-1.8degrees. The placement of S2AI screws using the free hand technique without any radiographic guidance appears to an acceptable method of insertion without more radiation or time consuming.

Treatment of Unstable Sacral Fractures Related to Spino-Pelvic Dissociations

PURPOSE: To evaluate the outcomes of surgical treatment modality in unstable sacral fractures combined with spinal and pelvic ring injury depending on the presence of spino-pelvic dissociations. MATERIALS AND METHODS: The subjects were 16 patients, with unstable sacral fractures combined with spinal and pelvic ring injuries, were operated from July 2004 to January 2011. The patients were divided into 2 groups depending on the presence of spino-pelvic dissociations: those with dissociations were group 1, and those without dissociations were group 2. Group 1 was treated with spino-pelvic fixations using iliac screw, while group 2 was treated with percutaneous iliosacral screw fixations. The availability of the radiological bony union with its application periods, and clinical results using visual analogue scale (VAS) and oswestry disability index (ODI) were evaluated, retrospectively. RESULTS: Out of 16 patients, 8 patients in group 1 were treated with spino-pelvic fixation using iliac screw, and 8 patients in group 2 were treated with percutaneous iliosacral screw fixation. The mean bony union period was 17.4 weeks in group 1, and 19.6 weeks in group 2. The Mean VAS and ODI scores on the last follow-up were 2.5 points and 15.6 points in group 1, 2 points and 18.8 points in group 2, respectively. Both groups had favorable clinical results at the last follow-up. CONCLUSION: For surgical treatments of unstable sacral fractures, spino-pelvic fixation using iliac screws is advised for cases with combined spino-pelvic dissociation, while percutaneous iliosacral screw fixation is advised for cases without combined dissociation.