Sacral Alar Iliac Screws Research Articles

Application of second sacral alar-iliac screw technique for reconstruction of spinopelvic stability

To summarize the current research progress of second sacral alar-iliac (S 2AI) screw technique for reconstruction of spinopelvic stability. The recent original literature concerning development, clinical applications, anatomy, imageology, and biomechanics of S 2AI screw technique in reconstruction of spinopelvic stability was reviewed and analyzed. As a common clinical strategy for the reconstruction of spinopelvic stability, S 2AI screws achieve satisfactory effectiveness of lumbosacral fixation without complications which were found during the application of traditional iliac screws technique. S 2AI screw technique is more difficult to place screws by hand because of its narrow screw trajectory. Although the S 2AI screws trajectory pass through 3 layers of bone cortex, the biomechanical cadaveric study demonstrate that no statistical difference in stiffness was found between the traditional iliac and S 2AI screw in a spinopelvic fixation model. S 2AI screw technique should be a safe and feasible method for reconstruction of spinopelvic stability in place of the traditional iliac screw technique.

Persistent Iliosacral Joint Syndrome following Instrumentation to the Sacropelvis in Patients with Adult Spinal Deformity.

Persistent sacroiliac joint syndrome (PSIJS) may complicate adult spinal deformity surgery (ASDS). This study assesses the relationship between clinical/morphometric parameters and PSIJS following ASDS including pelvic fixation and the therapeutic efficacy of secondary iliosacral fusion (ISF). Perioperative health-related quality of life (HRQOL) outcomes (Oswestry Disability Index, Short Form 12-item health survey, version 2 scores) at 6, 12, and 24 months, and radiographic studies were analyzed retrospectively in a cohort of 71 consecutive patients undergoing ASDS. PSIJS was confirmed in nine individuals (12.7%) by placebo-controlled dual sacroiliac joint (SIJ) blocks. The relationships between global and regional spinopelvic morphometry, PSIJS, and HRQOL outcomes were assessed by logistic regression and receiver operating characteristic curve (ROC) analysis. PSIJS, independently causing significantly reduced improvement in HRQOL scores (p < 0.001) 6 months postoperatively, warranted secondary ISF in nine patients (12.7%) within 12 months of index surgery, without evidence of progressive SIJ arthrosis, pseudarthrosis, or hardware issues. Eight of nine patients undergoing secondary ISF reported≥ 70% pain reduction at 24 months. Logistic regression/ROC analysis revealed a close association between PSIJS and nonharmonious postoperative L4-S1 fractional lordosis (p < 0.0001), pelvic incidence angle > 53 degrees, hip arthrosis, and preexistent advanced SIJ arthrosis (p < 0.01). PSIJS may negatively impact the clinical outcome of ASDS. Recurrent preoperative SIJ syndrome requiring interventional treatment, preexisting hip and SIJ arthrosis, insufficient restoration of L4-S1 fractional lordosis, and high pelvic incidence predispose to PSIJS. PSIJS may potentially be avoided by restoring physiologic lumbosacral geometry and S2 sacral alar-iliac screw fixation during index surgery. Secondary ISF appears to be effective in reducing pain and physical impairment due to PSIJS.

Optimal trajectory and insertion accuracy of sacral alar iliac screws

ObjectiveThe aim of this study was to analyse the optimal trajectories for sacral alar iliac screws (SAISs) in a Japanese patient population and the clinical assessment of insertion accuracies. MethodsThe ideal trajectories of SAISs, starting from 2 mm medial to the apex of the lateral sacral crest on the midline between S1 and S2 dorsal foramina, were measured in 80 consecutive spinal disease patients (40 males and 40 females; average age: 67.4 ± 8.1 years) using three-dimensional computed tomographic image software. Following these anatomic analyses, accuracies of 32 inserted SAISs in consecutive patients, who underwent long spinal posterior fusion, were investigated clinically. ResultsLateral angulations of optimal SAIS trajectories in males (left: 37.9; right: 37.7) were significantly larger than those than in females (left: 32.8; right: 32.4). Caudal SAIS angulations for females (left: 33.4; right: 33.9) were significantly larger than those in males (left: 27.5; right: 28.0). The 32 SAISs (100 mm long and 9 mm in diameter) assessed clinically were accurately inserted on optimal trajectories. ConclusionThe optimal trajectories of SAISs in a Japanese patient population are more lateral in males and more caudal in females. This study examines the clinical safety and accuracy of SAIS insertion on these optimal trajectories.

Paper #13 Sacral-Alar-Iliac Fixation in Early Onset Scoliosis

Sacral-alar-iliac (SAI) fixation is increasingly used for the treatment of scoliosis. This retrospective review of 24 patients with early onset scoliosis (EOS) compares the use of SAI screws to traditional methods of pelvic fixation. While SAI screws and traditional fixation methods effectively correct major curvature, only SAI screws were shown to correct pelvic obliquity with statistical significance in patients with EOS at a 2-year minimum follow-up. Additionally, SAI screws were shown to trend to more stable pelvic fixation.

Correction of Pelvic Obliquity After Spinopelvic Fixation in Children With Cerebral Palsy: A Comparison Study With Minimum Two-Year Follow-up

Study DesignSingle institution cohort data were collected prospectively and reviewed retrospectively. ObjectivesThis study aims to compare outcomes among three different instrumentation types: unit rod, iliac screws, and sacral alar iliac (SAI) screws in terms of pelvic obliquity correction in children with cerebral palsy (CP). Summary of Background DataThe optimal choice for spinopelvic fixation in CP scoliosis with pelvic obliquity is controversial. MethodsPatients with minimum 2 years' follow-up were divided into three groups according to instrumentation type and matched based on preoperative pelvic obliquity and coronal major curve magnitude. Radiographic measurements included horizontal pelvic obliquity angle (PO), spinopelvic angle (SPA), coronal and sagittal Cobb angles, and T1 pelvic angle. Procedures were performed in one pediatric institution between 2004 and 2012. All measurements were performed by a single independent reviewer who was not involved in the procedures. ResultsSeventy-seven patients (42 unit rod, 14 iliac screw, and 21 SAI screw) were included. Gender and age distribution was similar across all groups (56% males, 44% females, mean age 13.5 years). Mean follow-up was 3.6 years. Comparing pre- and postoperative measurements, there was a significant decrease (p < .05) in PO, SPA, and coronal major cob angle in all groups. No significant loss of correction occurred during follow-up. Postoperatively, TPA improved in all groups. Nonsymptomatic loosening was noted in 59% of unit rods, 57% of iliac screws, and 52% of SAI screws. One prominent iliac screw needed removal. One nonsymptomatic rod fracture, one infected pseudarthrosis, and one rod malposition occurred in unit rod group. ConclusionsThis study suggests that for correction of pelvic obliquity in cerebral palsy scoliosis, iliac and SAI screws were similar to the unit rod in comparative effectiveness and implant safety profile. Level of evidenceTherapeutic study, Level III.

Sacral Alar Iliac Fixation for Spine Deformity.

As the anatomy of the lumbosacral junction presents a unique challenge for the spine surgeon with regard to achieving a solid fusion, we describe the sacral alar iliac (SAI) technique, which can be used for the placement of pelvic anchors during posterior spinal arthrodesis. Position the patient prone on a radiolucent table. In approaching the starting point, perform limited dissection of the soft tissue between the S1 and S2 dorsal foramina, while taking care to minimize unnecessary dissection and blood loss. As the ideal screw pathway is one-third in the sacral ala and two-thirds in the ilium, start at the junction between the 1st and 2nd sacral segments, cross the sacroiliac joint, travel caudally toward the sciatic notch, cross between the inner and outer table of the ilium, and end close to the anterior inferior iliac spine cranial to the acetabular roof (Figs. 5-A and 5-B). In most children and adults, use screws with an outer diameter ≥9 mm, which are recommended to prevent screw breakage. Ensure that the SAI screws are in line with the remainder of the spinal anchors to allow for ease of rod insertion. Perform carefully layered wound closure per routine at the end of the case, with special attention to meticulous hemostasis. In a review of the cases of 32 pediatric patients treated with SAI fixation, Sponseller et al.27 reported a mean pelvic obliquity correction of 70% and a mean major coronal Cobb angle correction of 67%.

Rigid Instrumentation for Neuromuscular Scoliosis Improves Deformity Correction Without Increasing Complications.

Retrospective chart and radiographic review. To evaluate spinopelvic fixation technical advancements for the treatment of neuromuscular scoliosis. Implants for vertebral and pelvic fixation have evolved without data demonstrating the benefit for neuromuscular scoliosis. The aim of this study was to evaluate this evolution in terms of deformity correction, complications, and implant cost. Patients treated with posterior spinal fusion to the pelvis for neuromuscular scoliosis with minimum 1-year follow-up from 1998 to 2012 were reviewed. Constructs were defined as nonrigid (>50% sublaminar wire fixation with Galveston or iliac screw pelvic fixation) and rigid (≥50% pedicle screw fixation with iliac or sacral alar iliac screw pelvic fixation). Eighty patients were identified: cerebral palsy (55%), myelomeningocele (16%), syndrome (8%), muscular dystrophy (15%), or other neuromuscular disorders (6%). A total of 95% were nonambulatory. Mean follow-up was 3.9 years (range 1-12 years). Construct types were 23 nonrigid and 57 rigid. Estimated construct cost was greater in the rigid group at $15,488 as compared with $3128 in the nonrigid group despite the lower anchor density in the rigid construct group (1.38 vs. 1.80, P < 0.001). Open anterior releases were more frequently performed in the nonrigid group (13/23 vs. 5/57, P < 0.001). Deformity correction at final follow-up was significantly greater for both Cobb angle and pelvic obliquity in the rigid group. The rates of wound infection, wound dehiscence, implant prominence, and mechanical failure of the fixation were not significantly different. The pseudarthrosis rate requiring revision surgery was 22% in nonrigid group and 5% in the rigid group (P = 0.026). Advances in spinopelvic fixation have resulted in improved deformity correction with lower rates of pseudarthrosis and a decreased need for anterior release. This study demonstrates the benefits of modern spinopelvic fixation techniques.

Combined S-1 and S-2 sacral alar-iliac screws as a salvage technique for pelvic fixation after pseudarthrosis and lumbosacropelvic instability

Lumbosacropelvic pseudarthrosis after long spinal fusions for treatment of adult degenerative scoliosis remains a challenging condition. Moreover, although pelvic fixation with iliac screws is widely used in deformity surgery to provide a biomechanically strong distal anchor for long thoracolumbar constructs, there are very few options available after failed pelvic fixation with iliac screws. The authors conducted a retrospective review of the surgical charts and imaging findings of patients subjected to revision surgery for lumbosacropelvic pseudarthrosis from August 2011 to August 2012. This review identified 5 patients in whom a salvage technique combining both S-1 and S-2 sacral alar-iliac (SAI) screws had been performed. In this technical note, the authors present a detailed anatomical discussion and an appraisal of the sequential intraoperative steps of this new technique involving a combination of S-1 and S-2 SAI screws. The discussion is illustrated with a surgical case in which this technique was used to treat a patient with pseudarthrosis that had developed after fixation with classic iliac screws. In conclusion, although S-2 SAI screws have previously been reported as an interesting alternative to classic iliac wing screws, this report is the first on the use of combined S-1 and S-2 SAI screws for pelvic fixation as a salvage technique for lumbosacropelvic instability. According to the reported experience, this technique provides a biomechanically robust construct for definitive pelvic fixation during revision surgeries in the challenging scenarios of pseudarthrosis and instability of the lumbosacropelvic region.

Posterior second sacral alar iliac screw insertion: anatomic study in a Chinese population

To provide radiographic parameters for optimal placement of posterior second sacral alar iliac (S2AI) screw for instrumentation and fusion of scoliosis to the second sacral level in a Chinese population. S2AI screw trajectories were mapped on three-dimensional computed tomography (3DCT) reconstructions of 60 normal adult pelvises. 1 mm inferior and 1 mm lateral to the S1 dorsal foramen were chosen as the entry point, and ideal S2AI screw trajectories were explored by rotating and cutting the 3D pelvis, ensuring that the trajectories were of maximum length and width. The directions and depth of these determined trajectories were then measured. The ideal S2AI screw trajectories could be found in each pelvis. The left and right screw trajectory parameters for males were shown as follows: angulation was L 29.15 ± 8.60° vs. R 29.96 ± 8.28° (p = 0.286) caudally in the sagittal plane and L 36.49 ± 3.14° vs. R 37.16 ± 3.14° (p = 0.165) laterally in the transverse plane. The maximal and intrasacral lengths of trajectory were L 121.25 ± 8.33 vs. R 120.63 ± 7.54 mm (p = 0.460) and L 26.20 ± 3.31 vs. R 26.92 ± 4.76 mm (p = 0.268). The entry point was L 28.87 ± 3.33 vs. R 29.79 ± 3.55 mm (p = 0.186) lateral to the second sacral midline, and L 44.14 ± 11.87 vs. R 43.89 ± 12.53 mm (p = 0.687) underneath the skin. The trajectories for females were more caudal (L: 34.50 ± 6.56° vs. 29.15 ± 8.60°, p = 0.009; R: 35.72 ± 7.53° vs. 29.96 ± 8.28°, p = 0.007) in the sagittal plane, but the lateral angulation in the transverse plane showed no difference between genders (p > 0.05). The female iliac medullar cavities were obviously narrower than those of males (L: 14.76 ± 2.46 vs. 16.98 ± 3.52, p = 0.006; R: 14.94 ± 2.60 vs. 17.00 ± 2.81, p = 0.005). Although the average maximal length of trajectories for females were about 5 mm shorter than those of males, intrasacral length were equal to those of males. Furthermore, both the distance from entry point to the S2 midline and skin in the transverse plane showed no difference between genders. The feasibility to insert S2AI screws to the sacrum and ilium in an Asian population along with the ideal entry angle and length of trajectory were identified for clinical practice.

Innovative Techniques in Pediatric Deformity: Use of Temporary Internal Distraction and the Sacral Alar Iliac Technique in the Pediatric Population

Indications for, and clinical results of, temporary internal distraction for large rigid spinal deformity curves are reviewed. Use of this technique in 20 patients resulted in 54% initial correction and 79% final correction. One-third of the patients had temporary neuromonitoring changes. Use of low profile pelvic fixation with sacral alar-iliac screws from the sacral ala is described in 88 neuromuscular and syndromic patients. Pelvic obliquity was corrected to a mean of 5°. Eight of 176 screws showed lucency of >2 mm. Breakage did not occur in screws >8 mm. These techniques can aid in correction of severe deformity in children and adolescents.

Low Profile Pelvic Fixation With the Sacral Alar Iliac Technique in the Pediatric Population Improves Results at Two-Year Minimum Follow-up

Retrospective review. Anchor stability and prominence are problems with pelvic fixation in pediatric spinal deformity surgery. We compared the new sacral alar iliac (SAI) fixation technique (with a starting point in the sacral ala and in-line anchors deep under the midline muscle flap) with other methods of screw fixation. Iliac anchors have been shown to provide the best form of pelvic fixation. A trajectory from the posterior sacral surface to the iliac wings has recently been described. To our knowledge, no clinical series has compared this method of pelvic fixation in children to others. Of 32 consecutive pediatric patients who underwent SAI fixation, 2 died and 26 returned for follow-up (>2 years). Mean age at surgery was 14 years. Average screw size was 67 mm long and 7 to 9 mm in diameter. Clinical examinations, radiographs, and computed tomography scans were analyzed. Outcomes included pain over the implants, screw placement, implant prominence, radiographic lucency, need for revision, and infection. SAI patients were compared with 27 previous patients who had pelvic fixation via other screw techniques. For SAI fixation, correction of pelvic obliquity and Cobb angles were 20° ± 11° (70%) and 42° ± 25° (67%), respectively. For other pelvic fixation methods, those values were 10° ± 9° (50%), and 46° ± 16° (60%), respectively. Compared with other screws, SAI screws provided significantly better pelvic obliquity correction (P = 0.002) but no difference in Cobb correction. There were 2 lucencies adjacent to screws in both groups. Computed tomography scans of 18 SAI patients showed no intrapelvic protrusion, but 1 screw extended laterally (<5 mm). One early SAI patient required revision with larger screws, which relieved pain; there was 1 revision in the comparison group. SAI patients had no deep infections, implant prominence, late skin breakdown, or anchor migration; traditional patients had 3 deep infections (P = 0.09) and 3 instances of implant prominence, skin breakdown, or anchor migration. SAI pelvic fixation produces better correction of pelvic obliquity than do previous techniques. Radiographic and clinical anchor stability is satisfactory at 2-year follow-up.