Alar Iliac Screws Research Articles

Software-assisted preoperative planning of S1 Alar Iliac screws: a 3D morphometric and anatomical study.

S1 alar iliac (S1AI) trajectory has gained popularity as a salvage technique for revision surgeries and failed constructs in the lumbopelvic region. This study aims to investigate the morphometry of this new trajectory based on 3D models. The possible role of gender, ethnicity and view angle (surgeon's vs. radiologist's) was investigated. Computed tomography-driven virtual 3D models of spinopelvic region were created applying Materialize MIMICS software, and assessed for coronal and sagittal radiographic versus surgeon's view angles, and morphometry of the screw trajectory. Independent-samples t test was used to analyze the results. P value was set at < = 0.05. The Statistical Package for the Social Sciences Software (SPSS version 24.0) was used for the statistical analysis. A total of 164 3D models were simulated with a total 328 screws inserted satisfactorily within the S1AI trajectory. S1AI instrumentation was feasible in 96.48%. The mean radiological coronal angle was 50.619' ± 8.590' and the mean coronal angle for surgeons' perspective was 10.263' ± 5.860'. The mean radiological and surgeon's perspective sagittal angles were found to be 44.532' ± 6.424' and 31.164' ± 5.455', respectively. A statistically significant difference was found between anatomical and surgeon's perspective trajectories. Neither the pelvic laterality nor the gender influence the screw angles, length and diameter in radiological versus surgeon's view angles. Preoperative 3D modeling would be an invaluable adjunct to increase the accuracy of S1AI screw placement. Surgeon's perspective of the trajectory differs from standard CT sections and should be considered in preoperative planning.

Adding sacral anchors through an S1 alar screw and multirod construct as a strategy for lumbosacral junction augmentation: an in vitro comparison to S1 pedicle screws alone with sacroiliac fixation.

Achieving solid fusion of the lumbosacral junction continues to be a challenge in long-segment instrumentation to the sacrum. The purpose of this study was to test the condition of adding sacral anchors through an S1 alar screw (S1AS) and multirod construct relative to using S1 pedicle screws (S1PSs) alone with sacroiliac fixation in lumbosacral junction augmentation. Seven fresh-frozen human lumbar-pelvic spine cadaveric specimens were tested under nondestructive moments (7.5 Nm). The ranges of motion (ROMs) in extension, flexion, left and right lateral bending (LB), and axial rotation (AR) of instrumented segments (L3-S1); the lumbosacral region (L5-S1); and the adjacent segment (L2-3) were measured, and the axial construct stiffness (ACS) was recorded. The testing conditions were 1) intact; 2) bilateral pedicle screw (BPS) fixation at L3-S1 (S1PS alone); 3) BPS and unilateral S2 alar iliac screw (U-S2AIS) fixation; 4) BPS and unilateral S1AS (U-S1AS) fixation; 5) BPS and bilateral S2AIS (B-S2AIS) fixation; and 6) BPS and bilateral S1AS (B-S1AS) fixation. Accessory rods were used in testing conditions 3-6. In all directions, the ROMs of L5-S1 and L3-S1 were significantly reduced in B-S1AS and B-S2AIS conditions, compared with intact and S1PS alone. There was no significant difference in reduction of the ROMs of L5-S1 between B-S1ASs and B-S2AISs. Greater decreased ROMs of L3-S1 in extension and AR were detected with B-S2AISs than with B-S1ASs. Both B-S1ASs and B-S2AISs significantly increased the ACS compared with S1PSs alone. The ACS of B-S2AISs was significantly greater than that of B-S1ASs, but with greater increased ROMs of L2-3 in extension. Adding sacral anchors through S1ASs and a multirod construct was as effective as sacropelvic fixation in lumbosacral junction augmentation. The ACS was less than the sacropelvic fixation but with lower ROMs of the adjacent segment. The biomechanical effects of using S1ASs in the control of long-instrumented segments were moderate (better than S1PSs alone but worse than sacropelvic fixation). This strategy is appropriate for patients requiring advanced lumbosacral fixation, and the risk of sacroiliac joint violation can be avoided.

Effect of Sacropelvic Hardware on Axis and Center of Rotation of the Sacroiliac Joint: A Finite Element Study.

The sacroiliac joint (SIJ) transfers the load of the upper body to the lower extremities while allowing a variable physiological movement among individuals. The axis of rotation (AoR) and center of rotation (CoR) of the SIJ can be evaluated to analyze the stability of the SIJ, including when the sacrum is fixed. The purpose of this study was to determine how load intensity affects the SIJ for the intact model and to characterize how sacropelvic fixation performed with different techniques affects this joint. Five T10-pelvis models were used: (1) intact model; (2) pedicle screws and rods in T10-S1; (3)pedicle screws and rods in T10-S1, and bilateral S2 alar-iliac screws (S2AI); (4) pedicle screws and rods in T10-S1, bilateral S2AI screws, and triangular implants inserted bilaterally in a sacral alar-iliac trajectory ; and (5) pedicle screws and rods in T10-S1, bilateral S2AI screws, and 2 bilateral triangular implants inserted in a lateral trajectory. Outputs of these models under flexion-extension were compared: AoR and CoR of the SIJ at incremental steps from 0 to 7.5 Nm for the intact model and AoR and CoR of the SIJ for the instrumented models at 7.5 Nm. The intact model was validated against an in vivo study by comparing range of motion and displacement of the sacrum. Increasing the load intensity for the intact model led to an increase of the rotation of the sacrum but did not change the CoR. Comparison among the instrumented models showed that sacropelvic fixation techniques reduced the rotation of the sacrum and stabilized the SIJ, in particular with triangular implants. The study outcomes suggest that increasing load intensity increases the rotation of the sacrum but does not influence the CoR, and use of sacropelvic fixation increases the stability of the SIJ, especially when triangular implants are employed. The choice of the instrumentation strategy for sacropelvic fixation affects the stability of the construct in terms of both range of motion and axes of rotation, with direct consequences on the risk of failure and mobilization. Clinical studies should be performed to confirm these biomechanical findings.

Canadian Spine Society

# Abstract 57. Radiographic reporting in adolescent idiopathic scoliosis: Is there a discrepancy comparing radiologists’ reports and surgeons’ assessments? {#article-title-2} Cobb angle measurement is the standard method for quantification of scoliosis in adolescent idiopathic scoliosis (AIS),

Lumbar Fusion including Sacroiliac Joint Fixation Increases the Stress and Angular Motion at the Hip Joint: A Finite Element Study.

Adult spinal fusion surgery improves lumbar alignment and patient satisfaction. Adult spinal deformity surgery improves saggital balance not only lumbar lesion, but also at hip joint coverage. It was expected that hip joint coverage rate was improved and joint stress decreased. However, it was reported that adjacent joint disease at hip joint was induced by adult spinal fusion surgery including sacroiliac joint fixation on an X-ray study. The mechanism is still unclear. We aimed to investigate the association between lumbosacral fusion including sacroiliac joint fixation and contact stress of the hip joint. A 40-year-old woman with intact lumbar vertebrae underwent computed tomography. A three-dimensional nonlinear finite element model was constructed from the L4 vertebra to the femoral bone with triangular shell elements (thickness, 2 mm; size, 3 mm) for the cortical bone's outer surface and 2-mm (lumbar spine) or 3-mm (femoral bone) tetrahedral solid elements for the remaining bone. We constructed the following four models: a non-fusion model (NF), a L4-5 fusion model (L5F), a L4-S1 fusion model (S1F), and a L4-S2 alar iliac screw fixation model (S2F). A compressive load of 400 N was applied vertically to the L4 vertebra and a 10-Nm bending moment was additionally applied to the L4 vertebra to stimulate flexion, extension, left lateral bending, and axial rotation. Each model's hip joint's von Mises stress and angular motion were analyzed. The hip joint's angular motion in NF, L5F, S1F, and S2F gradually increased; the S2F model presented the greatest angular motion. The average and maximum contact stress of the hip joint was the highest in the S2F model. Thus, lumbosacral fusion surgery with sacroiliac joint fixation placed added stress on the hip joint. We propose that this was a consequence of adjacent joint spinopelvic fixation. Lumbar-to-pelvic fixation increases the angular motion and stress at the hip joint.

Radiological Evaluation of Pelvic Morphology for S2 Alar-Iliac Screw Insertion in the Japanese Samples: A Retrospective Cohort Study.

S2 alar-iliac screw (S2AIS) insertion for lumbosacral fixation is becoming a common procedure for deformity surgeries. However, studies that have reported the anatomy and morphometric features of the pelvis for S2AIS insertion in the Japanese samples are scarce. This study aimed to elucidate the morphometric features of the pelvis regarding S2AIS insertion in the Japanese samples. We used 60 computed tomography scans of the pelvis (30 men and 30 women). The entry point for the S2AIS was determined as 1-mm lateral and 1-mm distal to the S1 dorsal sacral foramen. We resliced the plane in which the pelvis was sectioned obliquely from this entry point to the anterior inferior iliac spine in the sagittal plane. We bilaterally placed the shortest and longest virtual S2AISs in this plane using a 4-mm margin. We analyzed the length, angle, and safety of the determined trajectory and compared these measurements according to sex and age. The median longest and shortest screw lengths were 108.1 and 103.3 mm, respectively. The median longest and shortest distances from the entry point to the sacroiliac joint were 31.2 and 28.2 mm, respectively. The median smallest and largest lateral angulations were 40.7° and 47.3°, respectively. The median angle range was 4.2°. The median caudal angulation was -2.8°. The median shortest and longest distances from the S2AISs to the acetabular roof were 23.5 and 27.4 mm, respectively. The median distance from the S2AISs to the sciatic notch was 23.1 mm. Assuming the insertion of screw with a diameter of 8 mm, S2AIS insertion was difficult in 32 of 120 (27%) screws because the dorsal cortex of the sacrum was damaged. Screw length and lateral angulation were similar to those in previous studies. Insertion difficulty occurred in 27% of screws.

In-Human Report of S2 Alar-Iliac Screw Placement Using Augmented Reality Assistance.

S2 alar-iliac (S2AI) screws provide spinopelvic fixation with the advantages of minimized dissection, easier rod contouring, and decreased symptomatic screw-head prominence. However, placement of S2AI screws may be challenging because of the anatomy of the lumbosacral junction. Augmented reality is a nascent technology that may enhance placement of S2AI screws. To report the first in-human placement of augmented reality (AR)-assisted S2 alar-iliac screws and evaluate the accuracy of screw placement. A retrospective review was performed of patients who underwent AR-assisted S2AI screw placement. All surgeries were performed by 2 neurosurgeons using an AR head-mounted display (Xvision, Augmedics). Screw accuracy was analyzed in a blinded fashion by an independent neuroradiologist using the cortical breach grading scale. Twelve patients underwent AR-assisted S2AI screw placement for a total of 23 screws. Indications for surgery included deformity, degenerative disease, and tumor. Twenty-two screws (95.6%) were accurate-defined as grade 0 or grade 1. Twenty-one screws (91.3%) were classified as grade 0, 1 screw (4.3%) was grade 1, and 1 screw (4.3%) was grade 3. All breaches were asymptomatic. AR-assisted S2AI screw placement had an overall accuracy rate of 95.6% (grade 0 and grade 1 screws) in a cohort of 12 patients and 23 screws. This compares favorably with freehand and robotic placement. 1,2 AR enables spine surgeons to both better visualize anatomy and accurately place spinal instrumentation. Future studies are warranted to research the learning curve and cost analysis of AR-assisted spine surgery.

Sacroiliac Joint Pain Should Be Suspected in Early Buttock and Groin Pain after Adult Spinal Deformity Surgery: An Observational Study.

Sacroiliac joint pain (SIJP) is one of the pathological conditions of adjacent segment disorders occurring after adult spinal deformity (ASD) surgery. This study aimed to test the hypothesis that even in ASD surgery using S2 alar-iliac (S2AI) screws, SIJP can develop much earlier than reported previously and can be rescued by ultrasound-guided sacroiliac joint block. Overall, 94 patients with ASD treated with long spinal fusion using S2AI screws were prospectively investigated for SIJP postoperatively, and the effect of ultrasound-guided sacroiliac joint block was evaluated. Additionally, the relationship between the symptomatic side of the SIJP and the surgical procedure; the preoperative and postoperative whole-spine sagittal and coronal alignment, lumbar pelvis sagittal plane alignment, and pelvic incidence-lumbar lordosis were retrospectively compared between the groups with and without SIJP. Eleven of 94 cases (11.7%) developed SIJP. The average onset was 12.0 (±6.2) days after surgery. The "one-finger test," "Gaenslen test," and "tenderness of the posterosuperior iliac spine" had high positivity rates for SIJP. Night pain occurred in 81.8% of patients and was one of the diagnostic features. There were no significant relationships between the symptomatic side of SIJP and the approach-side of lumbar interbody fusion, donor site of the iliac bone graft, or malposition of the S2AI screw. There were no significant differences in preoperative characteristics and radiological parameters between the SIJP-positive and -negative groups preoperatively, postoperatively, or in postoperative changes. Two of the 11 cases required the SIJ block four times, but all patients eventually achieved >70% pain relief with no recurrence. For good pain control and physical therapy, the fact that early buttock-groin pain after spinal fusion surgery has a 12% likelihood of being due to SIJP and can be relieved with the ultrasound-guided SIJ block is clinically important for diagnosis and pain management.

S2 alar-iliac screw loosening as a preventive factor for hip joint osteoarthritis after adult spinal deformity surgery: a case-control study.

This study aimed to evaluate the progression of hip pathology and risk factors after ASD surgery. This case-control study enrolled 123 patients (246 hips); seven hips underwent hip arthroplasty were excluded. We measured the center-edge (CE) angle, joint space width (JSW), and Kellgren-Lawrence (KL) grade. We defined a CE angle˂25° as developmental dysplasia of the hip (DDH). We evaluated S2 alar-iliac (AI) screw loosening at final follow-up. The annual decrease in the JSW was 0.31mm up to 1year, and 0.13mm after 1year (p = 0.001). KL grade progression occurred in 24 hips (10.0%; group P), while no progression occurred in 215 (90.0%; group N) hips. Nonparametric analysis between groups P and N revealed that significant differences were observed in sex, DDH, KL grade, ratio of S2AI screw fixation at baseline, and ratio of S2AI screw loosening at final follow-up. Multiple logistic regression analysis revealed that DDH (p = 0.018, odds ratio (OR) = 3.0, 95%CI = 1.2-7.3), baseline KL grade (p < 0.0001, OR = 37.7, 95%CI = 7.0-203.2), and S2AI screw fixation (p = 0.035, OR = 3.4, 95%CI = 1.1-10.4) were significant factors. We performed sub-analysis to elucidate the relationship between screw loosening and hip osteoarthritis in 131 hips that underwent S2AI screw fixation. Non-loosening of the S2AI screw was a significant factor for KL grade progression (p < 0.0001, OR = 8.9, 95%CI = 3.0-26.4). This study identified the prevalence and risk factors for the progression of hip osteoarthritis after ASD surgery. Physicians need to pay attention to the hip joint pathology after ASD surgery.

Distal sacral nerve roots severed by a fragility fracture of the sacrum: a case report

BackgroundOwing to the aging population, fragility fractures of the pelvis are occurring more frequently. Fixation of the fracture and stabilization of the pelvic ring usually provide good clinical results. A case of distal sacral nerve roots severed by a fragility fracture of the sacrum is presented.Case presentationA 62-year-old Japanese woman with schizophrenia with low back pain, gait disorder, dysuria, and fecal incontinence presented to an emergency department, and plain X-rays showed no findings. She also complained of dysuria, and neurogenic bladder and cystitis were diagnosed. One month later, she was admitted to a psychiatric hospital for exacerbation of schizophrenia. In hospital, she had a urethral catheter inserted and spent 3 months in bed. She was referred to our orthopedic department because a gait disorder was discovered after her mental condition improved and she was permitted to walk. On examination, she could not walk and had decreased sensation from the buttocks to both posterior thighs and around the anus and perineum. Manual muscle testing of her lower limbs showed mild weakness of about 4 in bilateral flexor hallucis longus and gastrocnemius, and bilateral Achilles tendon reflexes were lost. Her anal sphincter did not contract, and urinary retention continued after urethral catheter removal. Imaging examinations showed an H-shaped sacral fracture consisting of a transverse fracture with displacement of the third sacral vertebra and vertical fractures of the bilateral sacral wings, with severe stenosis of the spinal canal at the site of the transverse fracture. The patient was diagnosed as having bladder and rectal dysfunction due to a displaced, unstable sacral fracture. First to third sacral laminectomy and alar–iliac fixation using percutaneous pedicle screws and sacral alar–iliac screws were then performed. The bilateral distal sacral nerve roots (S3, S4, S5) were completely severed at the second to third sacral levels, but bilateral second sacral nerve roots were not compressed from the bifurcation to the sacral foramen. Postoperatively, bladder and rectal dysfunction remained, but the low back pain was alleviated. Two weeks postoperatively, she could walk with a walker and was discharged. Three months after the operation, bone fusion of the fracture was observed.ConclusionsIn cases of bladder–rectal dysfunction with low back pain, the possibility of sacral fracture should be considered, and computed tomography, magnetic resonance imaging, and X-ray examinations should be performed. Even sacral fractures without displacement require attention because they can cause serious injury in the event of a nerve root being severed if not diagnosed early and given appropriate treatment.

P18. Characterization of sacropelvic fixation using novel porous fusion/fixation implants in combination with thoracolumbar instrumentation

<h3>BACKGROUND CONTEXT</h3> Sacropelvic fixation is often used at the distal end of long constructs in adult deformity surgery in order to provide biomechanical support to the base of the constructs, with the aim of reducing complications such as pseudarthrosis of the L5-S1 joint and hardware failure or loosening. <h3>PURPOSE</h3> The objective of this study was to investigate configurations in which a porous fusion/fixation (PFF) implant was employed to enhance sacropelvic fixation. <h3>STUDY DESIGN/SETTING</h3> Finite element study. <h3>OUTCOME MEASURES</h3> The outputs analyzed in this comparison were: (a) range of motion (ROM) of L5-S1 and sacroiliac joint (SIJ) with respect to PED; (b) the maximal von Mises stresses in S1 pedicle screws; (c) the maximal von Mises stresses in either the S2 alar-iliac screws or in PFF implants in a S2 alar-iliac trajectory; (d) the maximal stresses in the posterior rods between the pedicle screws in L5 and S1 (ie, lumbosacral junction). <h3>METHODS</h3> Three instrumented T10-pelvis models were created from an intact validated model: (1) pedicle screws and rods in T10-S1, and PFF implants inserted bilaterally in a S2 alar-iliac trajectory (PFFI); (2) pedicle screws and rods in T10-S1, PFF implants inserted bilaterally in a S2 alar-iliac trajectory, and triangular implants inserted bilaterally above the PFFI in a sacro-alar-iliac trajectory (PFFI-IFSAI); and (3) pedicle screws and rods in T10-S1, PFF implants inserted bilaterally in a S2 alar-iliac trajectory, and PFF implants in a SAI trajectory stacked cephalad to those in the S2 alar-iliac position (2-PFFI). These configurations were compared against two baseline models: (1) pedicle screws and rods in T10-S1 (PED); and (2) pedicle screws and rods in T10-S1, and S2 alar-iliac screws (S2AI). All the instrumented models were used to simulate pure moments of 7.5 Nm to the upper endplate of the T10 vertebra in flexion, extension, left and right lateral bending, and left and right axial rotation. Double leg stance was simulated by fixing both acetabula of the models. <h3>RESULTS</h3> Sacropelvic fixation demonstrated a greater decrease in ROM of both L5-S1 and SIJ with respect PED. S2AI and PFFI had similar results in terms of L5-S1 and SIJ motion. PFFI-IFSAI did not affect the ROM between L5 and S1 but did reduce that of the SIJ. 2-PFFI further decreased L5-S1 motion and demonstrated a behavior similar to PFFI – IFSAI in terms of SIJ motion. S2AI fixation showed a slight increase of the stresses on S1 pedicle screws and on implants in the S2AI position with respect to PFFI. PFFI-IFSAI slightly decreased the stresses in S1 pedicle screws and on implants in the S2AI position with respect to PFFI. 2-PFFI significantly decreased the stresses on these implants (28-62 MPa for S1 pedicle screws and up to 66% for implants in the S2AI position) with respect to other configurations. In the posterior rods, the von Mises stresses were found to be highest when PFF implants were used with respect to S2AI, though all stresses were below those found in S1 pedicle screws in PED. <h3>CONCLUSIONS</h3> This study confirmed that sacropelvic fixation is able to reduce ROM at L5S1 and lower instrumentation stresses suggesting a reduced risk of pseudarthrosis at the joint and screw breakage, respectively. Moreover, outcomes suggest that PFF implants increase stability of the L5-S1 and SIJ, and reduce the risk of screw breakage. Clinical evaluation should be performed to confirm the applicability of results to patient outcomes. <h3>FDA DEVICE/DRUG STATUS</h3> iFuse Implant System (SI-BONE, Santa Clara, CA) (Approved for this indication), iFuse Bedrock Granite Implant System (SI-BONE, Santa Clara, CA) (Investigational/Not Approved).

Effect of pelvic fixation on ambulation in children with neuromuscular scoliosis.

BACKGROUNDThe effect of posterior spinal fusion (PSF) incorporating the pelvis on an ambulatory patient’s ability to mobilize after the fusion is not well understood. AIMTo see whether a posterior spinal fusion with pelvic fixation using iliac or sacral alar iliac screws in ambulatory neuromuscular scoliosis (NMS) patients influences postoperative ambulatory ability.METHODSA retrospective review of all patients with NMS that underwent PSF with fixation incorporating the pelvis between January 1, 2012 and February 29, 2019. A total of 118 patients were eligible, including 11 ambulatory patients. The primary outcome was the maintenance of ambulatory status postoperatively. Secondary outcomes included postoperative curve magnitude, pelvic obliquity, and complications, comprising infections, instrumentation failure, and any unplanned returns to the operative room.RESULTSThe ambulatory function was maintained in all 11 ambulatory NMS patients. One patient had an improvement in functional status with equipment-free ambulation postoperatively. An average postoperative follow-up was 19 mo. The overall complication rate was 19.4% (n = 23) with no significant differences between the groups in infection (P = 0.365), hardware failure (P = 0.505), and reoperation rate (P = 1.0). Ambulatory status did not affect complication rate (P = 0.967).CONCLUSIONSpinal fusion to the pelvis in ambulatory patients with NMS provides effective deformity correction without the reduction in ambulatory capabilities.

Clinical utility of minimally invasive posterior internal fixation within the pelvic ring using S2 alar iliac screws for unstable pelvic ring fracture

IntroductionPosterior internal fixation for unstable pelvic ring fractures is often associated with complications, including pelvic hemorrhage and gluteal necrosis. Pelvic ring fixation using the S2 alar iliac screw (SAIS) without fixation of the lumbosacral vertebrae may have potential as a novel, minimally invasive technique for treating unstable pelvic ring fractures. The present study compared clinical outcomes in patients who underwent SAIS fixation within the pelvic ring with a historical control group of patients who underwent conventional trans-iliac plate fixation for the treatment of unstable pelvic ring fractures. Materials and methodsThirty-two patients diagnosed with unstable pelvic fractures with sacral fracture or sacroiliac joint fracture dislocation were retrospectively evaluated. Eight consecutive patients underwent trans-iliac plate fixation from April 2012 to March 2015, and 24 consecutive patients underwent SAIS fixation from April 2015 to February 2020. Rates of soft tissue complications, intraoperative blood loss, and intraoperative blood transfusion volume were compared in these two groups. ResultsMean intraoperative blood loss was significantly lower in patients who underwent SAIS fixation than in those who underwent trans-iliac plate fixation (141.0 ml vs 315.0 ml; P = 0.027), although there were no between-group differences in intraoperative blood transfusion volume (0.0 ml vs 140 ml; P = 0.105), incidence rate of soft tissue complications (4.2% vs 0%; P = 1.000), and operation time (88.5 min vs 93.0 min; P = 0.862). Bone healing was confirmed in all patients who underwent SAIS fixation without dislocation of the fracture site, whereas one patient who underwent trans-iliac plate fixation experienced a dislocation of the fracture site during follow-up (0% vs 12.5%; P = 0.250). ConclusionsSAIS fixation reduces intraoperative blood loss and ensures bone healing without major complications, including dislocation of the fracture site. SAIS fixation may therefore be an alternative, minimally invasive method of treating unstable pelvic fractures.

Navigation-assisted resection of tumoral calcinosis of the lumbosacral spine: illustrative case

BACKGROUNDTumoral calcinosis is an uncommon disease resulting from dystrophic calcium phosphate crystal deposition, with only 7% of cases involving the spine, and it may diagnostically mimic neoplasms.OBSERVATIONSIn this case, a 54-year-old woman with history of systemic scleroderma presented with 10 months of progressive left lumbosacral pain. Imaging revealed an expansile, 4 × 7-cm, well-circumscribed mass in the lumbosacral spine with L5–S1 neuroforaminal compression. Because intractable pain and computed tomography (CT)-guided needle biopsy did not entirely rule out malignancy, operative management was pursued. The patient underwent L4–S2 laminectomies, left L5–S1 facetectomy, L5 and S1 pediculectomies, and en bloc resection, performed under stereotactic CT-guided intraoperative navigation. Subsequently, instrumented fusion was performed with L4 and L5 pedicle screws and S2 alar-iliac screws. Pathological examination was consistent with tumoral calcinosis, with multiple nodules of amorphous basophilic granular calcified material lined by histiocytes. There was no evidence of recurrence or neurological deficits at 5-month follow-up.LESSONSBecause spinal tumoral calcinosis may mimic neoplasms on imaging or gross intraoperative appearance, awareness of this clinical entity is essential for any spine surgeon. A review of all case reports of lumbosacral tumoral calcinosis (n = 14 from 1952 to 2016) was additionally performed. The case featured in this report presents the first known case of navigation-assisted resection of lumbosacral tumoral calcinosis.

Clinical outcomes of S2 Alar-Iliac screw technique in the treatment of severe spinal sagittal imbalance: a retrospective 2-year follow-up study

&lt;p class="abstract"&gt;&lt;strong&gt;Background: &lt;/strong&gt;The treatment of adult spinal deformity (ASD) remains a significant challenge, especially in elderly patients. This study aimed to evaluate the outcomes of the S2AI screw technique in the treatment of severe spinal sagittal imbalance with a minimum 2-year follow-up.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Methods: &lt;/strong&gt;From January 2015 to December 2018, 23 patients with severe degenerative thoracolumbar kyphosis who underwent placement of S2AI screws for long segment fusion were retrospectively reviewed. Patients were divided into group A (no mechanical complications, 13 cases) and group B (with mechanical complications, 10 cases) according to the occurrence of mechanical complications at the last follow-up. Radiographic parameters were compared between groups preoperatively, 1 month postoperatively and at the last follow-up. Risk factors for mechanical complications were analyzed.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Results:&lt;/strong&gt; The incidence of mechanical complications was 43.5% and the revision rate was 17.4%. At 1 month postoperatively, sagittal correction was better in group A than in group B (p&amp;lt;0.05). The area under the curve for predicting mechanical complications of sacral slope (SS), lumbar lordosis (LL), PI (pelvic incidence)-LL at 1 month postoperatively were 0.762 (p=0.035), 0.896 (p=0.001) and 0.754 (p=0.041) respectively and the best cut-off values were 24.1°, 32.8°and 12.0°. The sagittal correction of both groups was partially lost at the last follow-up.&lt;/p&gt;&lt;p class="abstract"&gt;&lt;strong&gt;Conclusions:&lt;/strong&gt; A high incidence of mechanical complications was observed in long-segment corrective surgery with the S2AI screw technique for severe spinal sagittal imbalance. Inadequate sagittal correction is a risk factor for the development of mechanical complications.&lt;/p&gt;&lt;p class="abstract"&gt; &lt;/p&gt;

A Computed Tomography-Based Assessment of the Anatomical Parameters Concerning S2-Alar Iliac Screw Insertion Using "Safe Trajectory Method" in Indian Population.

A retrospective computed tomography (CT)-based radiological analysis. To obtain CT-based morphometric data for the S2 alar iliac (S2AI) screw in the Indian population presenting to School of Medical Sciences and Research, Greater Noida, we used the concept of "safe trajectory" by Pontes and his colleagues in a recent study. Although previous CT-based morphometric studies on the S2AI screw have been published for a variety of ethnic groups, morphometric data specifically for the Indian population are scarce. We used the three-dimensional multiplanar reformatting software to conduct a retrospective CT analysis of 112 consecutive patients who met our exclusion criteria for various abdominal and pelvic pathologies. CT imaging planes were rotated between the S1 and S2 foramen until they matched the ideal S2AI screw trajectory, which was represented by the longest and widest iliac osseous channel observed in the axial CT section. Following the concept of a safe trajectory, S2AI screw morphometric parameters were measured on both sides of the pelvis using corresponding axial and sagittal CT images. In the sagittal and transverse planes on both sides of the pelvis, females had significantly higher screw trajectory angulation than males (p<0.001). On both sides of the pelvis, males had significantly greater iliac width, maximum screw trajectory length, and intrascrotal length than females (p<0.001). On both sides of the pelvis, the S2AI screw entry point in females was significantly deeper than in males from the skin margin (p<0.001). Based on our methodology, we discovered that the S2AI screw trajectory is significantly more caudal and lateral in females, the maximum screw length is sufficient for use in clinical practice regardless of gender, and that 8.5 mm or even larger screw diameters are feasible in the majority of the Indian population.

Innovation of Surgical Techniques for Screw Fixation in Patients with Osteoporotic Spine.

Osteoporosis is a common disease in elderly populations and is a major public health problem worldwide. It is not uncommon for spine surgeons to perform spinal instrumented fusion surgeries for osteoporotic patients. However, in patients with severe osteoporosis, instrumented fusion may result in screw loosening, implant failure or nonunion because of a poor bone quality and decreased pedicle screw stability as well as increased graft subsidence risk. In addition, revision surgeries to correct failed instrumentation are becoming increasingly common in patients with osteoporosis. Therefore, techniques to enhance the fixation of pedicle screws are required in spinal surgeries for osteoporotic patients. To date, various instrumentation methods, such as a supplemental hook, sublaminar taping and sacral alar iliac screws, and modified screwing techniques have been available for reinforcing pedicle screw fixation. In addition, several materials, including polymethylmethacrylate and hydroxyapatite stick/granules, for insertion into prepared screw holes, can be used to enhance screw fixation. Many biomechanical tests support the effectiveness of these augmentation methods. We herein review the current therapeutic strategies for screw fixation and augmentation methods in the surgical treatment of patients with an osteoporotic spine.

Comparative Study of S2-Alar-Iliac Screw Trajectories between Males and Females Using Three-Dimensional Computed Tomography Analysis: The True Lateral Angulation of the S2-Alar-Iliac Screw in the Axial Plane.

The S2 alar-iliac screw (S2AIS) is commonly used for long spinal fusion as a rigid distal foundation in spinal deformity surgeries, and it is also used in percutaneous sacropelvic fixation for providing an in-line connection to the proximal spinal constructs without using offset connectors. Although the pelvic shape is different between males and females, reports on S2AIS trajectories according to gender have been scarce in the literature. In this paper, S2AIS trajectories are compared between males and females using pelvic three-dimensional computed tomography (3D-CT) in a normal Japanese population. After resetting the caudal angulation in CT-imaging plane manipulation, the angulation of S2AIS was more lateral in the axial plane and more horizontal in the coronal plane in females. Mean distances from the midline to starting points of S2AIS tended to be shorter in females, whereas mean distances from the midline to the posterior superior iliac spine was significantly longer in females. We also found that there were positive correlations between the patients’ height and the maximal lengths of S2AISs, and the patients’ height and minimal areas of S2AIS pathways. Our results are useful not only for conventional open spinal surgery, but also for minimally invasive spine surgery.

Sacro-pelvic Anthropometry in the Portuguese Population and Its Implication for Screw Placement in Spinal Surgery: A Single Centre Retrospective Analysis.

Objective The aim of this study was to assess the sacropelvic anthropometry in the Portuguese population, through the study of pelvic computed tomography (CT) scans. Methods Pelvic CT scans of 40 individuals were analyzed, and the length and angle measurements were performed according to predefined screw trajectories of S1 anterior (S1A), anterolateral (S1AL) and anteromedial (S1AM), S2 anterolateral (S2AL) and anteromedial (S2AM), S2 alar iliac (S2AI), iliac, and sacroiliac (SI) screws. Comparisons between genders were also performed. Results The S1A screw trajectory mean length was 30.80 mm. The S1AL mean length and lateral angle were 36.48 mm and 33.13°, respectively, and the S1AM's were 46.23 mm and 33.21°. The S2AL mean length was 28.66 mm and lateral angle was 26.52°, and the S2AM length and angle were 29.99 mm and 33.61°, respectively. The S2 alar-iliac screw trajectory mean length, lateral, and caudal angles were 125.84 mm, 36.78°, and 28.66°, respectively. The iliac screw trajectory mean length, lateral, and caudal angles were 136.73 mm, 23,86° and 24.01°, respectively. The sacroiliac screw trajectory length was 75.50 mm. The length of the screws was longer in men than in women, except for the S1A and SI screws, for which no difference was found between genders. Conclusion This study describes sacropelvic anatomical specifications. These defined morphometric details should be taken into consideration during surgical procedures.

Biomechanical investigation of S2 alar-iliac screw and S1 pedicle screw fixation in the treatment of Denis type II sacral fractures.

Although S2 alar-iliac screw technique has been widely used in spinal surgery, its applicability to pelvic fractures is largely unknown. This study aimed to evaluate the biomechanical stability of S2 alar-iliac screw and S1 pedicle screw fixation in the treatment of Denis II sacral fractures. Twenty-eight artificial pelvic fracture models were treated with unilateral lumbopelvic fixation, sacroiliac screw fixation, S2 alar-iliac screw and S1 pedicle screw fixation, and S2 alar-iliac screw and contralateral S1 pedicle screw fixation (Groups 1-4, respectively; N = 7 per group). Each model was cyclically tested under increasing axial compression. Optical motion-tracking was used to assess relative displacement and gap angle, and the number of failure cycles. Relative displacement was significantly smaller in Group 3 than in Groups 1 (p = 0.004) and 4 (p < 0.001) but not significantly different between Groups 3 and 2 (p = 0.290). The gap angle in Group 3 was significantly smaller than that in Group 1 (p = 0.009) on the sagittal plane but significantly larger than that in Group 4 (p = 0.006) on the horizontal plane. A number of failure cycles was significantly higher in Group 3 than in Groups 1 (p = 0.002) and 4 (p = 0.004) but not significantly different between Groups 3 and 2 (p = 0.910). From a biomechanical perspective, S2 alar-iliac screw and S1 pedicle screw fixation can provide good stability in the treatment of Denis II sacral fractures.