Iliac Screw Technique Research Articles

Modified unilateral iliac screw fixation with partial reduction in the treatment of high-grade spondylolisthesis at L5/S1 in adult patients: introduction of key technique, report of clinical outcomes and analysis of spinopelvic parameters

BackgroundManagement of high-grade spondylolisthesis (HGS) remains challenging. Spinopelvic fixation such as iliac screw (IS) was developed to deal with HGS. However concerns regarding constructs prominence and increased infection-related revision surgery have complicated it’s use. We aim to introduce the modified iliac screw (IS) technique in treating high-grade L5/S1 spondylolisthesis and it’s clinical and radiological outcomes.MethodsPatients with L5/S1 HGS who underwent modified IS fixation were enrolled. Pre- and postsurgical upright full spine radiographs were obtained to analyze sagittal imbalance, spinopelvic parameters, pelvic incidence-lumbar lordosis mismatch (PI-LL), slip percentage, slip angle (SA), and lumbosacral angle (LSA). Visual analogue scale (VAS), Oswestry disability index (ODI) were evaluated pre- and postoperatively for clinical outcomes assessment. Estimated blood loss, operating time, perioperative complications and revision surgery were documented.ResultsFrom Jan 2018 to March 2020, 32 patients (15 males) with mean age of 58.66 ± 7.77 years were included. The mean follow-up period was 49 months. The mean operation duration was 171.67 ± 36.66 min. At the last follow-up: (1) the VAS and ODI score were significantly improved (p < 0.05), (2) PI increased by an average of 4.3°, the slip percent, SA and LSA were significantly improved (p < 0.05), (3) four patients (16.7%) with global sagittal imbalance recovered a good sagittal alignment, PI-LL within ± 10° was observed in all patients. One patient experienced wound infection. One patient underwent a revision surgery due to pseudoarthrosis at L5/S1.ConclusionThe modified IS technique is safe and effective in treating L5/S1 HGS. Sparing use of offset connector could reduce hardware prominence, leading to lower wound infection rate and less revision surgery. The long-term clinical affection of increased PI value is unknown.

Three different techniques for pelvic fixation in the management of neuromuscular scoliosis in nonambulatory spastic cerebral palsy: A comparative study of Galveston Rod, iliac screw, and sacroiliac screw.

This study aimed to compare the clinical and radiographic results of three different pelvic fixation techniques, i.e., Galveston Rod, Iliac Screw, and Sacroiliac Screw, in managing neuromuscular scoliosis in nonambulatory children with spastic cerebral palsy (CP). This retrospective study included nonambulatory children aged < 18 years with neuromuscular scoliosis secondary to CP, undergoing a spinal fusion and pelvic fixation by either Galveston rod, iliac screw, or sacroiliac screw techniques. The primary outcome variable was to determine the stability of the major curve angle and pelvic obliquity over timeline intervals for each pelvic fixation tech nique. The two radiographic parameters were measured at five timeline intervals and were compared to define stability among the groups. One hundred and one patients (54 females [53%]) with spastic nonambulatory CP met the inclusion criteria; the mean age at sur gery was 13.5±3.1 years. Mean follow-up intervals were first-year (12.9±1.5) and second-year (25.8±2.5). Forty-one patients had minimum five-year (81.5±23 months) postoperative follow-up. Groups were based on pelvic fixation techniques: 25 patients with the Galveston rod, 24 with the iliac screw, and 52 with the sacroiliac screw. Of the 41 patients with a minimum five-year follow-up, 10 had the Galveston rod, 11 had an iliac screw, and 20 had sacroiliac screw fixation. Gross Motor Function Classification System level, medical comorbidities, intra thecal baclofen pump, and vitamin D level were compared with each pelvic fixation technique (P > .05). Major curve angle parameters were measured at the five timelines as 70.5°±21.1°, 15.7°±13°, 15.7°±12°, 17.5°±12.7°, and 15.1°±9.6°, and pelvic obliquity as 14.8°±10.4°, 4.9°±4.2°, 5.7°±4.6°, 5°±4.4°, and 7.2°±4.4°, respectively. After the surgery, corrected major curve angle and pelvic obliquity showed no sta tistically significant difference between pelvic fixation techniques (P > .05) and remained stable over timeline intervals (P > .05). Fifteen patients had complications requiring additional surgery. The iliac screw group (nine patients) had the highest rate of complications. All three pelvic fixation techniques can provide equivalent correction for major curve angle and pelvic obliquity in managing neuromuscular scoliosis in nonambulatory CP children. Pelvic obliquity after surgery may remain stable regardless of pelvic fixation type. A higher rate of postoperative complication can be encountered with the iliac screw. Level III, Retrospective Study.

Comparative Clinical Efficacy and Safety of Sacral-2-Alar Iliac Screw Versus Iliac Screw in the Lumbosacral Reconstruction of Spondylodiscitis

This study aimed to evaluate the clinical efficacy and safety of S2-alar-iliac (S2AI) and iliac screw (IS) techniques in treating lumbosacral spondylodiscitis. Between January 2020 and January 2022, 28 patients suffering from lumbosacral spondylodiscitis underwent lumbosacral fixation and were divided into the IS group (14 patients) and the S2AI group (14 patients). Surgical details, demographic characteristics, preoperative and postoperative Oswestry Disability Index, visual analog scale, and complications were analyzed. Twenty-eight patients were included in this study, including 14 patients treated with IS and 14 patients treated with S2AI. The 2 groups were similar in sex, age, follow-up period, total drainage volume, hospitalization stay, and fusion time. (P>0.05) The estimated blood loss and surgical time of S2AI during surgery were significantly lower than those of IS. (P<0.05) The visual analog scale and Oswestry Disability Index scores significantly improved in both groups from preoperative to the last follow-up. Sacroiliac joint pain was found in both groups in the follow-up period, but the incidence was not significantly different (P=0.663). Compared with the IS approach, the incidence of symptomatic screw prominence was lower in the S2AI group, but the difference was not significant. (P=0.088). S2AI, as well as IS techniques, can achieve promising results for reconstructing lumbosacral stability in spondylodiscitis. In addition, the S2AI technique can also reduce surgical trauma and operation time.

Surgical strategy of lumbopelvic instrumentation in the treatment of lumbosacral tuberculosis: S2-alar-iliac screws vs iliac screws.

The objective of this study was to evaluate the feasibility and clinical outcomes of S2-alar-iliac (S2AI) and iliac screw (IS) techniques in the lumbopelvic reconstruction of lumbosacral tuberculosis patients. From January 2014 to August 2016, 26 patients with lumbosacral tuberculosis attending the 8th Medical Centre of Chinese PLA General Hospital were included in this retrospective study. The subjects were divided into two groups based on the lumbopelvic fixation type (16 patients in the S2AI group, 10 patients in the IS group). The operation time, blood loss, length of hospitalisation, erythrocyte sedimentation rate (ESR), C-reactive protein (CRP) level, visual analogue scale (VAS), Oswestry Disability Index (ODI), ambulatory status, and 36-Item Short-Form Health Survey (SF-36) scores of the patients in two groups were recorded and compared. In addition, surgical complications were collected and analysed. The operation time and intraoperative blood loss were significantly lower in the S2AI group than that in the IS group (P < .05). Compared with preoperative data, postoperative data showed significant improvement in ESR, CRP level, ODI scores, VAS scores, ambulatory status, and SF-36 (P < .05), but there was no significant difference in remission degree between the two groups. Compared with IS group, The S2AI group had significantly lower rates of symptomatic screw prominence (P < .05). Both the IS and S2AI fixation techniques can achieve satisfactory outcomes for the restoration of lumbosacral stability of lumbosacral tuberculosis. Furthermore, compared to the traditional IS fixation technique, the S2AI fixation technique can shorten operation time and reduce surgical trauma for the treatment of lumbosacral tuberculosis.

Use of iliac screw associated with more correction of lumbar lordosis than S2-alar-iliac screw for adult spinal deformity

BackgroundTo date, there is a paucity of reports clarifying the change of spinopelvic parameters in patients with adult spinal deformity (ASD) who underwent long segment spinal fusion using iliac screw (IS) and S2-alar-iliac screw (S2AI) fixation.MethodsA retrospective review of consecutive patients who underwent deformity correction surgery for ASD between 2013 and 2017 was performed. Patients were divided into two groups based on whether IS or S2AI fixation was performed. All radiographic parameters were measured preoperatively, immediately postoperatively, and the last follow-up. Demographics, intraoperative and clinical data were analyzed between the two groups. Additionally, the cohort was subdivided according to the postoperative change in pelvic incidence (PI): subgroup (C) was defined as change in PI ≥5° and subgroup (NC) with change < 5°. In subgroup analyses, the 2 different types of postoperative change of PI were directly compared.ResultsA total of 142 patients met inclusion criteria: 111 who received IS and 31 received S2AI fixation. The IS group (65.6 ± 26°, 39.8 ± 13.8°) showed a significantly higher change in lumbar lordosis (LL) and upper lumbar lordosis (ULL) than the S2AI group (54.4 ± 17.9°, 30.3 ± 9.9°) (p < 0.05). In subgroup (C), PI significantly increased from 53° preoperatively to 59° postoperatively at least 50% of IS cohort, with a mean change of 5.8° (p < 0.05). The clinical outcomes at the last follow-up were significantly better in IS group than in S2AI group in terms of VAS scores for back and leg. The occurrence of sacroiliac joint pain and pelvic screw fracture were significantly greater in S2AI group than in IS group (25.8% vs 9%, p < 0.05) and (16.1% vs 3.6%, p < 0.05).ConclusionsCompared with the S2AI technique, the IS technique usable larger cantilever force demonstrated more correction of lumbar lordosis, and possible increase in pelvic incidence. Further study is warranted to clarify the clinical impaction of these results.

Spinal Fusion with Sacral Alar Iliac Pelvic Fixation in Severe Neuromuscular Scoliosis.

We demonstrate how to perform posterior spinal fusion with SAI pelvic fixation in a patient with cerebral palsy. In correcting the scoliosis, we utilize the segmental 3-dimensional technique, which includes compression, distraction, transverse approximation to 1 rod at a time, and derotation around 2 rods. We also demonstrate SAI pelvic fixation with identification of the screw starting point on the lateral-caudal border of the first sacral foramen and trajectory toward the anterior inferior iliac spine. Nonoperative alternatives include bracing, trunk support, contouring of sitting surfaces (such as wheelchairs), and physical therapy to slow curve progression during growth periods and delay the need for surgical treatment3,4. Decision-making is shared with the family following education about the risks and benefits. Families who are satisfied with the function of the child at baseline should not be persuaded into pursuing surgical treatment. Neuromuscular scoliosis can include difficulty sitting secondary to increased pelvic obliquity, along with poor trunk control and balance. Surgical intervention is considered in patients with curves exceeding approximately 50°, as these curves will often continue to progress even after maturity5. In patients with neuromuscular scoliosis, indications for pelvic fixation include pelvic obliquity of >15°, poor control of the trunk as indicated by lack of independent sitting or standing, and location of the apex of the curve in the lumbar spine. SAI screws are utilized as a low-profile option for pelvic fixation to avoid implant prominence and an increased risk of skin breakdown and infection, which are associated with traditional sacroiliac screws2,6. Miyanji et al. reported quality outcomes in patients with cerebral palsy and Gross Motor Function Classification Scores of ≥41. In that study, caregivers completed a validated disease-specific questionnaire grading the health-related quality of life of the patient preoperatively and at 1, 2, and 5 years postoperatively. Complication data were prospectively collected for each patient and preoperative outcome scores were compared at each of the postoperative time points. Survey scores at 1, 2, and 5 years postoperatively were significantly higher compared with baseline preoperative values.Sponseller et al. compared the 2-year postoperative radiographic parameters of 32 pediatric patients who underwent SAI fixation and 27 patients who underwent pelvic fixation with the sacroiliac technique2. Among patients who underwent SAI fixation, the mean correction of pelvic obliquity was 20° ± 11° (70% correction) and the mean Cobb angle 42° ± 25° (67%). Among patients who underwent pelvic fixation with the sacroiliac technique, those values were 10° ± 9° (50%) and 46° ± 16° (60%), respectively. SAI screws provided significantly better pelvic obliquity correction (p = 0.002) but no difference in Cobb correction or complications compared with other traditional techniques. Family discussion prior to surgical treatment is paramount.Perform preoperative neurologic examination7.Examine the cranium carefully for a ventriculoperitoneal shunt or prior cranial reconstruction prior to cranial traction.Transcranial neuromonitoring may be useful. Use descending neural motor evoked potentials when no signals from transcranial monitoring are obtained8.Sink the SAI screw until it lines up with the S1 screw. Bury the SAI screw so it is not prominent.Measure rods longer in order to ensure adequate length for compression and distraction in correction of the pelvic obliquity.Use a T-square to verify adequate spinopelvic alignment9.Postoperatively, the use of incisional vacuum-assisted closure can decrease soiling in these patients. SAI = Sacral alar iliacCP = Cerebral palsyAIS = Adolescent idiopathic scoliosisSMA = Spinal muscular atrophyIONM = Intraoperative neuromonitoringGMFCS = Gross Motor Functional Classification SystemDNMEP = Descending neural motor evoked potentialTXA = Tranexamic acidFFP = Fresh frozen plasmaASIS = Anterior superior iliac spineAIIS = Anterior inferior iliac spinePJK = Proximal junctional kyphosis.

Iliac Screw Fixation Revisited: Improved Clinical and Radiologic Outcomes Using a Modified Iliac Screw Fixation Technique.

A retrospective study. To describe the modified iliac screw (mILS) technique and compare it to other spinopelvic fixation techniques in terms of wound healing complications, hardware prominence, and failure. The traditional entry point of an iliac screw often causes postoperative gluteal pain from the prominent screw head. The use of an offset connector also adds a point of weakness to the construct. By choosing a different screw entry point offset connectors can be avoided, and the screw head itself is less prominent, thereby reducing postoperative discomfort. A retrospective analysis was performed of adult patients undergoing lumbopelvic fixation (LPF) between January 2014 and June 2019. Patients were grouped into 1 of 3 groups based on the technique of pelvic fixation: S2 alar-iliac (S2AI) screw, traditional iliac screw (tILS), and mILS. The primary outcome parameter was the minimal distance from screw head to skin. Secondary outcome parameters were instrumentation loosening/failure, adjacent level fractures, pseudoarthrosis, and medial or lateral iliac screw perforation. A total of 190 patients undergoing LPF were included in the following 3 groups: mILS group (n=113), tILS group (n=40), and S2AI group (n=37). The mean minimal distance from screw head to skin in the mILS group was 31.3 mm compared with 23.7 mm in the tILS group (P<0.00199). No statistically significant differences were found when comparing the 3 groups with respect to complications. The mILS group did not show any cases of prominent instrumentation and had the lowest rate of instrumentation failure. The mILS technique is an acceptable alternative for LPF, offering the benefits of iliac screw fixation while avoiding offset connectors and screw prominence complications associated with tILS. Level III.

Iliac screw instrumentation to the pelvis in children with neuromuscular and syndromic scoliosis. No lateral connectors and respect sagittal balance.

One-center retrospective cohort study. Compared to the traditional iliac screw technique, the modified iliac screw technique has a lower rate of distal implant failure in the treatment of neuromuscular scoliosis patients with pelvic obliquity. However, the reasons for decreased failure with the modified iliac screw technique are controversial. (1) Is distal implant failure, as evident by implant breakage or disconnection, more likely to occur in patients receiving the traditional iliac screw technique (PSIS) compared to the modified S2AI (MODS2) technique? (2) After controlling for relevant confounding variables, are there other identifiable risk factors for distal implant failure? We identified patients who underwent pelvic screw fixation by three pediatric spine surgeons from January 2007 to July 2017. Based on the starting point of the iliac screws, patients were divided into two groups. Group 1 consisted of PSIS fixation with an offset connector. Group 2 consisted of modified S2AI fixation without an offset connector. Demographic, operative, and radiographic data were obtained. Cobb angle, lumbar lordosis, and pelvic obliquity were not significantly different between the two groups. Overall distal implant failure was 40/100 (40%) and significant between Group 1 PSIS 29/53 (55%) and Group 2 MODS2 11/47 (23%) (p = 0.002). No other complications were significant. Three risk factors were identified with implant failure: high pelvic incidence (17-fold increase, 95% confidence interval [CI] = 5.5 to 53.1, p < 0.001), high angle rod contour (3.8-fold increase, 95% CI = 1.2 to 11.9, p = 0.023), and use of an offset connector (3.2-fold increase, 95% CI = 1.0 to 10.3, p = 0.049). Failure did not correlate with the use of a cross-link, iliac screw diameter, or screw density. Revision surgery related to distal implant failure did not significantly differ between the two groups. Compared to the use of an offset connector with PSIS fixation, MODS2 fixation had a lower rate of implant failure. Sagittal balance parameters, namely pelvic incidence and angle of rod bend, were the major risk factors for implant failure. III.

Clinical Effectiveness of S2-Alar Iliac Screws in Spinopelvic Fixation in Pediatric Neuromuscular Scoliosis: Systematic Literature Review.

Study Design:Systematic literature review.Objectives:To comprehensively review the S2-alar iliac (S2-AI) screw technique for pelvic fixation in pediatric neuromuscular scoliosis.Methods:Articles identified from the PubMed and EMBASE databases were reviewed for relevance and applicability, and the studies were summarized.Results:Eight articles met the inclusion criteria. A total of 277 pediatric patients underwent spinopelvic fixation using S2-AI fixation for neuromuscular scoliosis; the mean follow-up was 3 years (range = 0.75-6 years). Six articles had level III evidence (5 retrospective cohort studies, 1 observational study), and 2 articles had level IV evidence (case series). Wound complications occurred in 34 (12.2%) patients. Instrumentation complications occurred in 36 patients (13.0%), including lucency around the screw (6.5%), screw fracture (3.6%), disengaging of the set/screw or rod from the tulip head (2.8%), and screw displacement (0.7%). Three patients (1.1%) required reoperation for instrumentation failures. The overall reoperation rate—including 3 hardware replacements and 3 cases of L5-S1 pseudarthrosis—was 2.1%. The mean Cobb angle correction was 51.4°, and the mean pelvic obliquity correction was 14.8°; deformity correction was maintained at 3- and 5-year follow-ups. There were 10 (3.6%) cases of implant prominence/implant-related pain, 1 case of sacroiliac joint pain (resolved with longer screw placement), and no major neurological or vascular complications secondary to S2-AI screw placement.Conclusions:This review suggests that the use of S2-AI screws in pediatric neuromuscular scoliosis is efficacious with a reasonable safety profile and provides a useful technique for pelvic fixation in children with scoliosis.

Comparative tomographic study of the iliac screw and the S2-alar-iliac screw in children

OBJECTIVES:The recent advancements in spine fixation aid in the treatment of complex spinal pathologies. Both the iliac screw (IS) and the S2-alar-iliac (S2AI) screw provide adequate stability in the fixation of complex lumbosacral spine pathologies, leading to a significant increased rate of using these techniques in the daily practice of the spine surgeons. This study aims to analyze, describe, and compare the insertion and positioning parameters of the S2AI screw and IS techniques in children without spinal deformities.METHODS:An observational retrospective study was conducted at a university hospital in 2018, with 25 computed tomography (CT) images selected continuously. Mann-Whitney-Shapiro-Wilk tests were performed. The reliability of the data was assessed using the intraclass correlation. The data were stratified by age group only for Pearson’s correlation analysis.RESULTS:The mean age was 11.7 years (4.5 SD). The mean IS length was 106.63 mm (4.59 SD). The mean length of the S2AI screw was 104.13 mm (4.22 SD). The mean skin distance from the IS entry point was 28.13 mm (4.27 SD) and that for the S2AI screw was 39.96 mm (4.54 SD).CONCLUSIONS:Through CT, the S2AI screw trajectory was observed to have a greater bone thickness and skin distance than the IS. There was a linear correlation between age and screw length for both techniques. A similar relationship was observed between skin distance and age for the S2AI screw technique. In children, the S2AI screw technique presents advantages such as greater cutaneous coverage and implant thickness than the IS technique.

Neurovascular Relations in Modified Iliac Screws and Traditional Iliac Screw: Anatomic Study

This study describes a modified iliac screw technique and compares it with the traditional iliac screw in regard to neurovascular structures at risk. Few studies have detailed the insertion point's surrounding anatomy and its relationship to vulnerable neurovascular structures when this modified technique is used. Therefore we describe our modified iliac screw entry and trajectory and detail the surrounding anatomy and neurovascular structures at risk with this technique in comparison with the "gold standard" trajectory. The traditional iliac screw (TS) and modified iliac screw (MS) were placed into 12 fresh-frozen adult cadavers (3 female, 9 male). We measured the screw-to-supragluteal artery, vein, and nerve (SGANV) bundle and screw-to-sciatic notch distances. Further, we dissected the medial cortical border of the iliac screw to identify its final position with respect to the surrounding anatomy. No medial or lateral cortical breaches were visualized after screw placement. The MS was 18.31 mm from the greater sciatic foramen compared with 18.65 mm with the TS. The smallest distance from the MS to the greater sciatic foramen was 13.9 mm compared with 14.8 mm with the TS, an insignificant difference. The SGANV bundle-to-MS distance was 20.6 mm, and SGANV bundle-to-TS distance was 20.77 mm, again an insignificant difference. Using the modified iliac screw technique does not change the intraosseous pathway (and thus bone purchase) with respect to the distance between the screw and neurovascular structures at risk.

Comparative tomographic study of the S2-alar-iliac screw versus the iliac screw

AimsIliac screws and S2-alar-iliac screws provide adequate mechanical stability for the fixation of lumbosacral spine pathologies, which has led to a significant increase in the use of these techniques in the routine practice of spine surgeons. However, studies on the ideal technical positioning for both techniques are limited.Study designThis is an observational, retrospective, analytical descriptive study.ObjectiveTo analyze, describe and compare the insertion and positioning parameters of the S2-alar-iliac and iliac screw techniques in adult patients without spinal deformities.MethodsThe present study comprises a retrospective analysis of lumbosacral computed tomography images selected continuously in 2016 from 25 patients at a university hospital. Mann–Whitney–Shapiro–Wilk tests were performed. Data reliability was assessed using intraclass correlation.ResultsThe mean length of the iliac screw was greater than that of the S2-alar-iliac screw, and the S2-alar-iliac screw sat 20.5 mm deeper than the iliac screw. The mean of the greatest bone thickness for the iliac screw was 20.72 mm; that of the S2-alar-iliac screw was 23.24 mm. The mean distance from the iliac screw entry point to the skin was 32.46 mm, and the mean distance from the S2-alar-iliac screw entry point to the skin was 52.87 mm.ConclusionThe trajectory of the S2-alar-iliac screws studied via computed tomography was greater in terms of bone thickness and deeper relative to the skin compared with the iliac screws. The S2-alar-iliac technique may have desirable clinical advantages in terms of the diameter of the screws and reduced protrusion when used in adults.Graphical abstractThese slides can be retrieved from Electronic supplementary material.

Friday, September 28, 2018 10:30 AM–12:00 PM abstracts: deformity: technical factors: 170. Comparison of three lumbopelvic fixation techniques in long fusion to the sacrum in osteoporotic adult spinal deformity patients (>60 years): clinical and radiological outcomes

BACKGROUND CONTEXT Iliac screw techniques provide additional biomechanical stabilization to S1 in long fusion to the sacrum. Recently S2 Alar iliac screw (S2AI) fixation became more popular than traditional iliac screw (TIS) (entry point posterior superior iliac spine), and distal iliac screw (DIS) (entry point posterior inferior iliac spine) due to the lower implant profile and need for less extensive soft tissue dissection. S2AI fixes the sacroiliac (SI) joint differently from TIS and DIS. PURPOSE This study aimed to compare the clinical and radiologic outcomes between TIS, DIS and S2AI fixation in osteoporotic adult spinal deformity patients. STUDY DESIGN/SETTING Retrospective. PATIENT SAMPLE A total of 158 adult spinal deformity patients. OUTCOME MEASURES ODI questionnaire was evaluated for clinical outcome. METHODS A total of 158 (103f, 55m) adult spinal deformity patients pts who underwent long fusion to the sacrum with three different iliac screw techniques (TIS, DIS, S2AI) were reviewed. Radiologic parameters were compared between preop and f/up standing x-rays. Hospital charts and f/up CT scans were used to compare the screw lengths, diameters, and implant related complications including S1 and iliac screw loosening, rod breakage, sacroiliac joint dissociation (SID), surgical site infections (SSI) and hematoma. ODI scores were compared for clinical assessment. RESULTS A total of 54 patients had TIS, 51 patients had DIS, 53 patients had S2AI fixation. Mean ages were 67, 71, 68; mean f/up was 54.2 (24–174) months, respectively. Iliac screw lengths were 85mm, 90mm, 105mm; diameters were 9.0mm, 8.5mm, 9.5mm for TIS, DIS, S2AI, respectively. There were seven patients (12.9%) in TIS, six patients (11.7%) in DIS & three patients (5.6%) in S2AI with implant related complications. One patient (1.8%) in TIS and one patient (1.9%) in DIS group showed SID (TIS=1, DIS=1, S2AI=0). Postop hematoma was detected in 14 patients (8.8%) (TIS=4, DIS=7, S2AI=3) and SSI developed in two patients (1.2%) (TIS=1, DIS=1, S2AI=0). ODI scores improved in all groups. CONCLUSIONS All techniques provided sufficient stability for lumbosacral fusion in adult spinal deformity patients. S2 Alar iliac screw technique showed lower implant related complication rates when compared to both iliac screw techniques. Traditional iliac screwand Distal iliac screw had higher rates of hematoma and surgical site infections due to extensive soft tissue dissection compared to S2 Alar iliac screw. S2 Alar iliac screw does not lead to sacroiliac joint dissociation as it provides stability by fixing the sacroiliac joint.

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.

Biomechanical characterization of three iliac screw fixation techniques: A finite element study

We aim to characterize the biomechanical properties of a modified iliac screw fixation method compared with the classic iliac screw fixation and the S2 alar iliac screw (S2AI) fixation using a FEM.A three-dimensional, non-linear FEM of lumbosacral spine and pelvis (L1-pelvis) was modified to simulate 3 different iliac screw fixations based on posterior screw fusion. The peak von Mises stress (PVMS) values of the iliac screws in the 3 different iliac screw fixations were recorded in during flexion/extension/axial rotation/lateral bending. The interaction stress which arose between the screw head and the shaft of iliac screws, was also measured for each case.The PVMS values of the 3 different iliac screw fixation techniques were lower than the fatigue strength levels under physiological loadings. PVMS of iliac screws was observed in the screw shaft for S2AI, in the screw neck for the modified iliac screw technique, and in the offset connectors of the classic iliac screw technique. The interaction between the screw head and the neck was compressed in modified iliac screw fixation technique. On the other hand, distraction force was observed in the S2AI technique between the screw head and the screw shaft.This FEM study supports our previous clinical results, which found that the modified iliac screw fixation technique can be an effective alternative sacropelvic fixation technique comparable to the classic iliac screw and the S2AI technique.

Minimally invasive dual iliac screw, dual rod fixation in a rare case of pathological sacral fracture from a paraganglionoma: a technique description.

The management of lumbosacral neoplastic disease can be demanding, often requiring complex reconstruction. In the context of extensive sacral involvement, the risk of iliac screw breakage is greater. Few studies advocate the use of dual iliac screw techniques to reduce implant failure. In this report, the authors have described the first case of percutaneous dual iliac screw, dual rod insertion as part of a minimally invasive spinopelvic stabilization in a patient with a sacral fracture from a paraganglionoma. The patient underwent percutaneous L-2 to ilium fixation. A dual iliac screw, dual rod construct was used for stabilizing the left lumbopelvic junction. At the 1-year follow-up, the patient remained asymptomatic, with radiographs showing no signs of instrumentation failure. Minimally invasive dual iliac screw, dual rod fixation is a viable option in cases in which additional stability is required due to extensive neoplastic disease or active individuals have increased functional demands. Short-term results in this report are encouraging; however, more research is warranted to establish the procedure's long-term safety.

Perpendicular Iliac Screw Placement for Reinforcement of Spinopelvic Stabilization.

Iliac fixation is indicated to provide spinopelvic stabilization in select cases of long segment thoracolumbar spine fusion, spinal osteotomy/realignment, trauma, and instability caused by tumor or infection. Traditional iliac fixation with iliac screws or S2 alar/iliac (S2AI) screws may provide inadequate fixation in select clinical scenarios, such as severely compromised bone quality or spinopelvic dissociation. The purpose of this article is to describe the perpendicular iliac screw technique with ipsilateral iliac crest screw plus S2AI fixation. The technique may be applied for select individuals in cases of 3-column osteotomy in the lower lumbar spine, spinopelvic dissociation (caused by trauma, neoplasm, or Charcot arthropathy), and failure of previous iliac fixation and when anatomic constraints limit standard iliac screw or S2AI screw placement. [Orthopedics. 2016; 39(6):e1209-e1212.].

Use of S2-Alar-iliac Screws Associated With Less Complications Than Iliac Screws in Adult Lumbosacropelvic Fixation.

Retrospective comparative study. To compare clinical and radiographic outcomes between the S2-alar-iliac (S2AI) and the iliac screw (IS) techniques in the adult population and clarify the clinical strength of S2AI screws. S2AI screws have been described as an alternative method for lumbosacropelvic fixation in place of ISs. The S2AI technique has several advantages with lower prominence, increased ability to directly connect to proximal instrumentation, less extensive dissection of tissue, and enhanced biomechanical strength over the IS technique. However, the clinical significance of these advantages remains unclear. A single-center retrospective review of patients who underwent lumbosacropelvic fixation yielded 25 IS group patients and 65 S2AI group patients. Baseline demographic information, postoperative complications, pain and functional outcomes, and screw-related outcomes were collected. The S2AI group had lower rates of reoperation (8.8% vs. 48.0%, P < 0.001), surgical site infection (SSI) (1.5% vs. 44.0%, P < 0.001), wound dehiscence (1.5% vs. 36.0%, P < 0.001), and symptomatic screw prominence (0.0% vs. 12.0%, P = 0.02) than the IS group, whereas rates of L5-S1 pseudarthrosis, proximal junctional failure, and sacroiliac joint pain were similar in both groups. Statistically significant pain relief and functional recovery were achieved in both groups without any significant intergroup differences. On multivariate analyses, age [odds ratio (OR) = 0.91, P = 0.004] and S2AI instrumentation (OR = 0.08, P < 0.001) were protective of reoperation, whereas diabetes mellitus (OR = 10.9, P = 0.03) and preoperative diagnosis of tumor (OR = 12.3, P = 0.04) were associated with SSI, and S2AI instrumentation (OR = 0.09, P < 0.001) was protective of SSI. The use of the S2AI technique over the IS technique was an independent predictor of preventing reoperation and SSI, while achieving similar clinical and functional outcomes. 4.

S2-Alar-Iliac Screws are Associated with Lower Rate of Symptomatic Screw Prominence than Iliac Screws: Radiographic Analysis of Minimal Distance from Screw Head to Skin

In sacropelvic fixation, the iliac screw technique offers biomechanically strong constructs, but its disadvantages include screw prominence, wound dehiscence, and postoperative pain secondary to the high profile nature. To overcome this drawback, S2-alar-iliac (S2AI) screws were developed as an alternative technique for sacropelvic fixation. This study aimed to compare the S2AI screw technique with the iliac screw technique in terms of postoperative symptomatic screw prominence. A retrospective review of the records of sacropelvic fusion procedures performed at a single institution between October 2010 and January 2015 identified 32 patients with 72 iliac screws and 68 patients with 148 S2AI screws, and clinical and radiographic data were collected. If a patient had wound dehiscence and/or tenderness in the buttock immediately overlying a pelvic screw head postoperatively, it was defined as symptomatic screw prominence. The minimal distance from screw head to skin (MDSS) on postoperative computed tomography scans was measured for each patient to clarify the relationship between symptomatic screw prominence and MDSS. Mean follow-up period was 22.0 months. There was significantly more symptomatic pelvic screw prominence in the iliac screw group (11.1% vs. 1.4%, P= 0.002). MDSS ≤23 mm was the strongest predictor of symptomatic pelvic screw prominence, which yielded sensitivity of 100%, specificity of 94.1%, positive predictive value of 47.6%, and negative predictive value of 100%. The use of the S2AI screw technique resulted in a reduced rate of symptomatic screw prominence. MDSS ≤23 mm was the strongest predictor of symptomatic screw prominence.

A Comparison of Early Clinical and Radiographic Complications of Iliac Screw Fixation versus S2 Alar Iliac (S2AI) Fixation in the Adult and Pediatric Populations

Study Design:Retrospective chart review.Objective:To compare short-term clinical and radiographic complications between iliac screw (IS) and S2 alar-iliac (S2AI) screw fixation techniques in the adult and pediatric populations.Summary of Background Data:Pelvic fixation with lumbosacral implants is i