Dual S2 Alar-Iliac Screw Technique With a Multirod Construct Across the Lumbosacral Junction: Obtaining Adequate Stability at the Lumbosacral Junction in Spinal Deformity Surgery

Incidence and Risk Factors of the Caudal Screw Loosening after Pelvic Fixation for Adult Spinal Deformity: A Systematic Review and Meta-analysis

The purpose of this study was to assess the factors affecting caudal screw loosening after spinopelvic fixation for adult patients with spinal deformity. This meta-analysis calculated the weighted mean difference (WMD) and odds ratio (OR) using Review Manager ver. 5.3 (RevMan; Cochrane, London, UK). The loosening group was older than the control group (WMD, 2.17; 95% confidence interval [CI], 0.48-3.87; p=0.01). The S2 alar-iliac (S2AI) could prevent the caudal screw from loosening (OR, 0.43; 95% CI, 0.20-0.94; p=0.03). However, gender distribution (p=0.36), the number of fusion segments (p=0.24), rod breakage (p=0.97), T-score (p=0.10), and proximal junctional kyphosis (p=0.75) demonstrated no difference. Preoperatively, only pelvic incidence (PI) in the loosening group was higher (WMD, 5.08; 95% CI, 2.71-7.45; p<0.01), while thoracic kyphosis (p=0.09), lumbar lordosis (LL) (p=0.69), pelvic tilt (PT) (p=0.31), pelvic incidence minus lumbar lordosis (PI-LL) (p=0.35), sagittal vertical axis (SVA) (p=0.27), and T1 pelvic angle (TPA) demonstrated no difference (p=0.10). PI-LL (WMD, 6.05; 95% CI, 0.96-11.14; p=0.02), PT (WMD, 4.12; 95% CI, 0.99-7.26; p=0.01), TPA (WMD, 4.72; 95% CI, 2.35-7.09; p<0.01), and SVA (WMD, 13.35; 95% CI, 2.83-3.87; p=0.001) were higher in the screw loosening group immediately postoperatively. However, TK (p=0.24) and LL (p=0.44) demonstrated no difference. TPA (WMD, 8.38; 95% CI, 3.30-13.47; p<0.01), PT (WMD, 6.01; 95% CI, 1.47-10.55; p=0.01), and SVA (WMD, 23.13; 95% CI, 12.06-34.21; p<0.01) were higher in the screw loosening group at the final follow-up. However, PI-LL (p=0.17) demonstrated no significant difference. Elderly individuals were more susceptible to the caudal screw loosening, and the S2AI screw might better reduce the caudal screw loosening rate than the iliac screws. The lumbar lordosis and sagittal alignment should be reconstructed properly to prevent the caudal screw from loosening. Measures to block sagittal alignment deterioration could also prevent the caudal screw from loosening.

The iliac kickstand screw: anatomic CT analysis of screw trajectory and osseous corridor for screw placement

INTRODUCTION

The 'kickstand screw-rod' technique has been recently described for correction of coronal malalignment. This technique utilizes powerful 'construct-to-ilium' distraction between a fixed multi-screw thoracic construct and the ilium, facilitated by a novel 'iliac kickstand screw'. The 'iliac kickstand screw' traverses a previously undescribed osseous corridor in the ilium.

OBJECTIVE

Using a radiographic CT study, the objective is to describe a large osseous corridor within the ilium to accommodate the novel iliac kickstand screw.

METHODS

50 consecutive patients with pelvic CTs at an academic medical center were queried. Simulated iliac kickstand screw trajectories for the left and right hemipelvis were analyzed with 3D visualization software. Maximal screw lengths and dimensions, and trajectories in the osseous corridor were measured.

RESULTS

50 patients' (31 female, 19 male) pelvic CTs were measured with a total of 100 simulated screws. The mean age was 52.4 years and BMI 28.1 ± 7.9. The average length is 119.7 ± 6.6 mm (range 98.7 - 135.3). The narrowest width (maximum potential screw diameter) is 17.8 ± 2.9 mm (coronal) and 20.8 ± 5.3 mm (sagittal). The starting point to the top of the iliac crest is 66.4 mm lateral to midline, and 15.9° caudal in the sagittal and 6.1° lateral in the coronal planes.

CONCLUSIONS

The novel iliac kickstand screw traverses a consistent and large osseous corridor within the ilium. The average simulated screw length is 119.7 mm and maximum potential diameter of 17.8 mm. Starting points relative to the iliac crest are identified.

Clinicoradiological Outcomes and Complication Profiles of Bilateral Dual Sacral-Alar-Iliac Screws versus Bilateral Single Sacral-Alar-Iliac Screws in Patients with Spinal Deformity Who Underwent Grade 3 or 4 Spinal Osteotomies: A Retrospective Comparative Study

OBJECTIVE

To compare short-term clinical and radiological outcomes and complication profiles between bilateral dual sacral-2-alar-iliac (S2AI) screw and bilateral single S2AI screw fixation techniques in patients who underwent grade 3 or 4 spinal osteotomies.

METHODS

A retrospective review of 83 patients treated with bilateral dual S2AI screws and 32 patients treated with bilateral single S2AI screws was conducted between 2018 and 2020 with a minimum 1-year follow-up. Clinical and radiological outcomes of patients and incidence of perioperative complications, including rod breakage, screw dislodgment, proximal junctional kyphosis, proximal junctional failure, need for reoperation, and systemic adverse effects, were collected and statistically compared between the groups.

RESULTS

With a mean follow-up of 18.2 months, rod fracture (6.0% vs. 18.7%, P = 0.03), screw dislodgment (0 vs. 12.5%, P < 0.01), and S2AI screw loosening (1.2% vs. 18.7%, P < 0.01) were significantly lower in the dual S2AI screws group than in the single S2AI screws group. However, the reoperation rate was similar between the 2 groups (24.1% vs. 34.3%, P = 0.26). No significant differences in clinical and radiological outcomes as well as proximal junctional kyphosis (10.8% vs. 18.7%, P = 0.25) and proximal junctional failure (9.6% vs. 18.7%, P = 0.18) were identified between the 2 groups.

CONCLUSIONS

The dual S2AI screw fixation technique showed more advantages over the single S2AI screw fixation technique with reduced incidence of screw dislodgment, rod fractures, and sacral-alar-iliac screw loosening.

Strategies to Avoid Distal Junctional Pathology

Distal junctional pathology remains an unsolved issue in spine surgery. Distal junctional pathology can occur on a spectrum from asymptomatic radiographic finding to catastrophic distal construct failure. It is significant to address as postoperative sagittal balance has been shown to be correlated with patient-reported outcomes. Current literature and clinical experience suggest there are techniques that can be implemented regardless of setting to avoid distal junctional pathology. Much of the avoidant strategy relies on understanding the deformity pathology, selection of the lowest instrumented vertebra (LIV), health of the segments caudal to the LIV, and methods of fixation.

Incidence, mechanism, and protective strategies for 2-year pelvic fixation failure after adult spinal deformity surgery with a minimum six-level fusion

OBJECTIVE

The purpose of this study was to determine the incidence, mechanism, and potential protective strategies for pelvic fixation failure (PFF) within 2 years after adult spinal deformity (ASD) surgery.

METHODS

Data for ASD patients (age ≥ 18 years, minimum of six instrumented levels) with pelvic fixation (S2-alar-iliac [S2AI] and/or iliac screws) with a minimum 2-year follow-up were consecutively collected (2015-2019). Patients with prior pelvic fixation were excluded. PFF was defined as any revision to pelvic screws, which may include broken rods across the lumbosacral junction requiring revision to pelvic screws, pseudarthrosis across the lumbosacral junction requiring revision to pelvic screws, a broken or loose pelvic screw, or sacral/iliac fracture. Patient information including demographic data and health history (age, sex, BMI, smoking status, American Society of Anesthesiologists score, osteoporosis), operative (total instrumented levels [TIL], three-column osteotomy [3CO], interbody fusion), screw (iliac, S2AI, length, diameter), rod (diameter, kickstand), rod pattern (number crossing lumbopelvic junction, lowest instrumented vertebra [LIV] of accessory rod[s], lateral connectors, dual-headed screws), and pre- and postradiographic (lumbar lordosis, pelvic incidence, pelvic tilt, major Cobb angle, lumbosacral fractional curve, C7 coronal vertical axis [CVA], T1 pelvic angle, C7 sagittal vertical axis) parameters was collected. All rods across the lumbosacral junction were cobalt-chrome. All iliac and S2AI screws were closed-headed tulips. Both univariate and multivariate analyses were performed to determine risk factors for PFF.

RESULTS

Of 253 patients (mean age 58.9 years, mean TIL 13.6, 3CO 15.8%, L5-S1 interbody 74.7%, mean pelvic screw diameter/length 8.6/87 mm), the 2-year failure rate was 4.3% (n = 11). The mechanisms of failure included broken rods across the lumbosacral junction (n = 4), pseudarthrosis across the lumbosacral junction requiring revision to pelvic screws (n = 3), broken pelvic screw (n = 1), loose pelvic screw (n = 1), sacral/iliac fracture (n = 1), and painful/prominent pelvic screw (n = 1). A higher number of rods crossing the lumbopelvic junction (mean 3.8 no failure vs 2.9 failure, p = 0.009) and accessory rod LIV to S2/ilium (no failure 54.2% vs failure 18.2%, p = 0.003) were protective for failure. Multivariate analysis demonstrated that accessory rod LIV to S2/ilium versus S1 (OR 0.2, p = 0.004) and number of rods crossing the lumbar to pelvis (OR 0.15, p = 0.002) were protective, while worse postoperative CVA (OR 1.5, p = 0.028) was an independent risk factor for failure.

CONCLUSIONS

The 2-year PFF rate was low relative to what is reported in the literature, despite patients undergoing long fusion constructs for ASD. The number of rods crossing the lumbopelvic junction and accessory rod LIV to S2/ilium relative to S1 alone likely increase construct stiffness. Residual postoperative coronal malalignment should be avoided to reduce PFF.

Rescue Pelvic Fixation in a Patient with Sacral-2-Alar-Iliac and Triangular Sacroiliac Joint Fusion (Bedrock) Instrumentation

The purpose of this report is to demonstrate the creation of a 4-rod lumbosacral construct, when "stacked" sacral-2-alar-iliac (S2AI) screws are not possible due to a concurrent treatment of sacroiliitis with a posterior approach sacroiliac joint fusion device. This technique uses a combined S2AI and subcrestal iliac approach to achieve the 4-rod lumbosacral construct, while simultaneously biomechanically supporting the S2AI screws and treating the sacroiliitis.

How common is acute pelvic fixation failure after adult spine surgery? A single-center study of 358 patients

OBJECTIVE

There is a paucity of literature on pelvic fixation failure after adult spine surgery in the early postoperative period. The purpose of this study was to determine the incidence of acute pelvic fixation failure in a large single-center study and to describe the lessons learned.

METHODS

The authors performed a retrospective review of adult (≥ 18 years old) patients who underwent spinal fusion with pelvic fixation (iliac, S2-alar-iliac [S2AI] screws) at a single academic medical center between 2015 and 2020. All patients had a minimum of 3 instrumented levels. The minimum follow-up was 6 months after the index spine surgery. Patients with prior pelvic fixation were excluded. Acute pelvic fixation failure was defined as revision of the pelvic screws within 6 months of the primary surgery. Patient demographics and operative, radiographic, and rod/screw parameters were collected. All rods were cobalt-chrome. All iliac and S2AI screws were closed-headed screws.

RESULTS

In 358 patients, the mean age was 59.5 ± 13.6 years, and 64.0% (n = 229) were female. The mean number of instrumented levels was 11.5 ± 5.5, and 79.1% (n = 283) had ≥ 6 levels fused. Three-column osteotomies were performed in 14.2% (n = 51) of patients, and 74.6% (n = 267) had an L5-S1 interbody fusion. The mean diameter/length of pelvic screws was 8.5/86.6 mm. The mean number of pelvic screws was 2.2 ± 0.5, the mean rod diameter was 6.0 ± 0 mm, and 78.5% (n = 281) had > 2 rods crossing the lumbopelvic junction. Accessory rods extended to S1 (32.7%, n = 117) or S2/ilium (45.8%, n = 164). Acute pelvic fixation failure occurred in 1 patient (0.3%); this individual had a broken S2AI screw near the head-neck junction. This 76-year-old woman with degenerative lumbar scoliosis and chronic lumbosacral zone 1 fracture nonunion had undergone posterior instrumented fusion from T10 to pelvis with bilateral S2AI screws (8.5 × 90 mm); i.e., transforaminal lumbar interbody fusion L4-S1. The patient had persistent left buttock pain postoperatively, with radiographically confirmed breakage of the left S2AI screw 68 days after surgery. Revision included instrumentation removal at L2-pelvis and a total of 4 pelvic screws.

CONCLUSIONS

The acute pelvic fixation failure rate was exceedingly low in adult spine surgery. This rate may be the result of multiple factors including the preference for multirod (> 2), closed-headed pelvic screw constructs in which large-diameter long screws are used. Increasing the number of rods and screws at the lumbopelvic junction may be important factors to consider, especially for patients with high risk for nonunion.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Multiple Points of Pelvic Fixation: Stacked S2-Alar-Iliac Screws (S2AI) or Concurrent S2AI and Open Sacroiliac Joint Fusion with Triangular Titanium Rod

Sacropelvic fixation is a continually evolving technique in the treatment of adult spinal deformity. The 2 most widely utilized techniques are iliac screw fixation and S2-alar-iliac (S2AI) screw fixation^1-3. The use of these techniques at the base of long fusion constructs, with the goal of providing a solid base to maintain surgical correction, has improved fusion rates and decreased rates of revision⁴.

Description

The procedure is performed with the patient under general anesthesia in the prone position and with use of 3D computer navigation based on intraoperative cone-beam computed tomography (CT) imaging. A standard open posterior approach with a midline incision and subperiosteal exposure of the proximal spine and sacrum is performed. Standard S2AI screw placement is performed. The S2AI starting point is on the dorsal sacrum 2 to 3 mm above the S2 foramen, aiming as caudal as possible in the teardrop. A navigated awl is utilized to establish the screw trajectory, passing through the sacrum, across the sacroiliac (SI) joint, and into the ilium. The track is serially tapped with use of navigated taps, 6.5 mm followed by 9.5 mm, under power. The screw is then placed under power with use of a navigated screwdriver.Proper placement of the caudal implant is vital as it allows for ample room for subsequent instrumentation. The additional point of pelvic fixation can be an S2AI screw or a triangular titanium rod (TTR). This additional implant is placed cephalad to the trajectory of the S2AI screw. A starting point 2 to 3 mm proximal to the S2AI screw tulip head on the sacral ala provides enough clearance and also helps to keep the implant low enough in the teardrop that it is likely to stay within bone. More proximal starting points should be avoided as they will result in a cephalad breach.For procedures with an additional point of pelvic fixation, the cephalad S2AI screw can be placed using the previously described method. For placement of the TTR, the starting point is marked with a burr. A navigated drill guide is utilized to first pass a drill bit to create a pilot hole, followed by a guide pin proximal to the S2AI screw in the teardrop. Drilling the tip of the guide pin into the distal, lateral iliac cortex prevents pin backout during the subsequent steps. A cannulated drill is then passed over the guide pin, traveling from the sacral ala and breaching the SI joint into the pelvis. A navigated broach is then utilized to create a track for the implant. The flat side of the triangular broach is turned toward the S2AI screw in order to help the implant sit as close as possible to the screw and to allow the implant to be as low as possible in the teardrop. The navigation system is utilized to choose the maximum possible implant length. The TTR is then passed over the guide pin and impacted to the appropriate depth. Multiplanar post-placement fluoroscopic images and an additional intraoperative CT scan of the pelvis are obtained to verify instrumentation position.

Alternatives

The use of spinopelvic fixation in long constructs is widely accepted, and various techniques have been described in the past¹. Alternatives to stacked S2AI screws or S2AI with TTR for SI joint fusion include traditional iliac screw fixation with offset connectors, modified iliac fixation, sacral fixation alone, and single S2AI screw fixation.

Rationale

The lumbosacral junction is the foundation of long spinal constructs and is known to be a point of high mechanical strain^5-7. Although pelvic instrumentation has been utilized to increase construct stiffness and fusion rates, pelvic fixation failure is frequently reported^8,9. At our institution, we identified a 5% acute pelvic fixation failure rate over an 18-month period¹⁰. In a subsequent multicenter retrospective series, a similar 5% acute pelvic fixation failure rate was also reported¹¹. In response to these findings, our institution changed its pelvic fixation strategies to incorporate multiple points of pelvic fixation. From our experience, utilization of multiple pelvic fixation points has decreased acute failure. In addition to preventing instrumentation failure, S2AI screws are lower-profile, which decreases the complication of implant prominence associated with traditional iliac screws. S2AI screw heads are also more in line with the pedicle screw heads, which decreases the need for excessive rod bending and connectors.The use of the techniques has been described in case reports and imaging studies^12-14, but until now has not been visually represented. Here, we provide technical and visual presentation of the placement of stacked S2AI screws or open SI joint fusion with a TTR above an S2AI screw.

Expected Outcomes

Pelvic fixation provides increased construct stiffness compared with sacral fixation alone^15-17 and has shown better rates of fusion⁴. However, failure rates of up to 35%^8,9 have been reported, and our own institution identified a 5% acute pelvic fixation failure rate¹⁰. In response to this, the multiple pelvic fixation strategy (stacked S2AI screws or S2AI and TTR for SI joint fusion) has been more widely utilized. In our experience utilizing multiple points of pelvic fixation, we have noticed a decreased rate of pelvic fixation failure and are in the process of reporting these findings^18,19.

Important Tips

The initial trajectory of the caudal S2AI screw needs to be as low as possible within the teardrop, just proximal to the sciatic notch.The starting point for the cephalad implant should be 2 to 3 mm proximal to the S2AI screw tulip head. This placement provides enough clearance and helps to contain the implant in bone.More proximal starting points may result in cephalad breach of the TTR.The use of a reverse-threaded Kirschner wire helps to prevent pin backout while drilling and broaching for TTR placement.If malpositioning of the TTR is found on imaging, removal and redirection is technically feasible.

Acronyms and Abbreviations

S2AI = S2-alar-iliacTTR = triangular titanium rodCT = computed tomographyAP = anteroposteriorOR = operating roomSI = sacroiliacDRMAS = dual rod multi-axial screwK-wire = Kirschner wireDVT = deep vein thrombosisPE = pulmonary embolism.

RCC (reinforced criss-cross construct): an easy and effective multi-rod thoraco-lumbar posterior reconstruction technique

STUDY DESIGN

Surgical technical note and literature review.

OBJECTIVES

To describe a technique that uses 4 rod constructs in cases of complex thoracolumbar spinal deformity correction or revision surgeries based on the hybrid use of two different types of purchase points by a staggered pedicle screw fixation. It utilizes two rods on either side of the spine using a lateral and medial entry point of pedicle screws in the vertebral body.

METHODS

Pedicle screws using extra-pedicular technique are more converging screws and are inserted alternately in the vertebral body and connected by rods. The left-out alternate vertebral bodies are fixed by a relatively straighter pedicle entry screw and connected to each other by a separate rod. So, two trajectories are independently used for a four-rod construct. This reconstruction has been named RCC (reinforced criss-cross construct). The screws in the index case were placed by free hand method, but we have increasingly utilized navigation guidance for placement of screws in recent times.

RESULTS

We present a surgical technical note in a patient with human immunodeficiency virus infection and acquired immune deficiency syndrome (HIV-AIDS). He was diagnosed to have multi-drug-resistant (MDR) tuberculous spondylodiscitis, complicated with Immune reconstitution inflammatory syndrome (IRIS) and implant failure resulting in kyphosis and thoracic myelopathy. RCC with pharmacological management achieved healing and union, which was maintained at 4 years follow-up. Our method of four-rod construct provides a strong and lasting construct in the management of spinal deformities and three-column osteotomies. It provides good structural support to the spine till bony union is achieved.

CONCLUSION

Hybrid multi-rod construct like RCC provides a rigid mechanical support to the instrumentation and reduces the chances of rod failure especially in complex thoraco-lumbar spinal deformity correction surgeries.

The Utilization of Dual Second Sacral Alar-Iliac Screws for Spinopelvic Fixation in Patients with Severe Kyphoscoliosis

OBJECTIVES

As a new pelvic fixation technique, the dual S2AI screws fixation technique could provide highly stable distal strength, and have wide clinical prospect in the correction of severe kyphoscoliosis. However, the ideal trajectory parameters, indications and clinical outcomes of this technique have not been reported so far. This study aimed to determine the anatomical parameters of dual S2AI screws in the normal Chinese adult population, investigating the indications of this technique and evaluating the feasibility and clinical outcomes.

METHODS

Fifteen males and 15 females with normal pelvis underwent a pelvic CT scan to determine ideal dual S2AI screws trajectories. Sagittal angle (SA), transverse angle (TA), maximal length (ML), sacral length, and skin distance were measured. Subsequently, we retrospectively reviewed the data of 16 patients (seven males and nine females) who underwent dual S2AI screw fixation and 23 patients who underwent single S2AI screw fixation between January 2014 and December 2019. Preoperative, postoperative, and latest follow-up measurements of Cobb angle, coronal balance (CB), spinal pelvic obliquity (SPO), and regional kyphosis (RK) were obtained. The mean follow-up time was 16.7 ± 7.1 months (range: 12-30 months). Independent t-test was used to determine the difference in the analysis of the trajectories. The paired sample non-parametric Wilcoxon test was performed to assess the changes in radiographic parameters between different time points and different groups.

RESULTS

For both male and females, the proximal S2AI screws had significantly higher TA and ML, but a lower SA than distal screws. Females showed significantly more caudal (SA: 25.03° ± 2.32° vs. 29.82° ± 2.47°, t = 7.742, P < 0.001) trajectories of distal screw. Additionally, ML in the females were significantly shorter than that in males (106.81 mm ± 6.79 mm vs. 101.63 mm ± 6.55 mm, t = 3.007, P = 0.003, 124.41 mm ± 7.57 mm vs. 116.23 mm ± 7.03 mm, t = 4.337, P < 0.001). Eight had unilateral and eight had bilateral dual S2AI screw placement. Respectively, both the single S2AI and dual S2AI groups showed significant postoperative improvement of Cobb angle, RK angle and SPO angle. In patients with dual S2AI screws fixation, two patients found that screws loosening occurred in one of dual screws at 1-year follow-up, and in patients with single S2AI screws fixation, six patients found screw loosing as well as two patients found screw breakage at 1-year follow-up. None of all patients had any prominent loss of correction.

CONCLUSION

The ideal trajectory of dual S2AI screw could be well established. The dual S2AI screw fixation technique is feasible in patients with severe kyphoscoliosis, and provides satisfactory correction of deformity with few postoperative complications.

Clinical, Radiographic, and Genetic Analyses in a Population-Based Cohort of Adult Spinal Deformity in the Older Population

OBJECTIVE

This study aimed to identify the sagittal parameters associated with health-related quality of life and genetic variations that increase the risk of adult spinal deformity (ASD) onset in the older population.

METHODS

We recruited 120 participants who had a sagittal vertical axis > 50 mm in a sagittal imbalance study. Sagittal radiographic parameters, cross-sectional area, and intramuscular fatty infiltration using the Goutallier classification in the paraspinal lumbar muscles were evaluated. Functional scales included the self-reported Oswestry Disability Index (ODI), 36-item Short Form Health Survey (SF-36), and visual analogue scales (VAS) for back and leg pain. We performed whole-exome sequencing and an exome-wide association study using the 100 control subjects and 63 individuals with severe phenotypes of sagittal imbalance.

RESULTS

Pelvic incidence minus lumbar lordosis (PI-LL) mismatch was negatively associated with the SF-36 and positively correlated with ODI and VAS for back and leg pain. PI-LL was related to the quality and size of the paraspinal muscles, especially the multifidus muscle. We identified common individual variants that reached exome-wide significance using single-variant analysis. The most significant single-nucleotide polymorphism was rs78773460, situated in an exon of the SVIL gene (odds ratio, 9.61; p = 1.15 × 10-9).

CONCLUSION

Older age, higher body mass index, and a more significant PI-LL mismatch were associated with unfavorable results on functional scales. We found a genetic variation in the SVIL gene, which has been associated with the integrity of the cytoskeleton and the development of skeletal muscles, in severe ASD phenotypes. Our results help to elucidate the pathogenesis of ASD.

Comparative Study of Bilateral Dual Sacral-Alar-Iliac Screws versus Bilateral Single Sacral-Alar-Iliac Screw for Adult Spine Deformities

OBJECTIVE

To evaluate the feasibility of O-arm navigation of bilateral dual sacral-alar-iliac (SAI) screws compared with conventional bilateral single SAI and S1 pedicle screws for pelvic anchors in cases of adult spinal deformity.

METHODS

This retrospective, comparative study included 39 patients who underwent corrective fusion using SAI screws from T10 to the pelvis. Patients were divided into 2 groups according to the number of SAI screws placed during adult spinal deformity surgery: single SAI screw (group S, 17 cases) and dual SAI screws (group D, 22 cases). The incidence of rod breakage, proximal junctional kyphosis, screw loosening, reoperation, and global alignment in each group was estimated. Postoperative patient-reported outcomes were measured using the Oswestry Disability Index, Japanese Orthopaedic Association Back Pain Evaluation Questionnaire, and visual analog scale.

RESULTS

The incidence of SAI screw loosening was significantly lower in group D than in group S (23% vs. 65%, P = 0.011). The rod breakage incidence was 0% and 12% in groups D and S, respectively (P = 0.17). There were no significant differences in the postoperative global alignment and clinical outcomes between the 2 groups.

CONCLUSIONS

Dual SAI screws were associated with a significantly reduced incidence of screw loosening compared with single SAI screws. The bilateral dual SAI screws technique for pelvic anchors is feasible for the treatment of patients with adult spinal deformity.

Correction of a severe coronal malalignment in adult spinal deformity using the "kickstand rod" technique as primary surgery

Objective

Adult spinal deformity (ASD) is a growing healthcare issue due to the aging population. A satisfying spine balance in both sagittal and coronal planes is achieved through surgery. Only few studies about the coronal alignment correction with the kickstand rod were reported in the literature, until now. The aim of the present study was to describe clinical and radiological outcomes of the Kickstand rod (KR) technique in a series of ASD patients with severe coronal malalignment after 1 year of follow-up.

Material and methods

Six patients affected by ASD with severe CM who underwent surgery between 2018 and 2019 were retrospectively analyzed. The mean follow up was 14 months. All patients had posterior-only approach with long pelvic-thoracic fixation according to the Kickstand rod technique.

Results

Postoperative alignment and pain numerical rating scale scores significantly improved. No instrumentation complications occurred. A coronal alignment improvement from a mean of 163 mm preoperatively to a mean of 32 mm postoperatively was observed.

Conclusion

KR technique appears to be a safe and efficient way for coronal and sagittal imbalance correction in ASD patients. Although technically demanding, by using this technique good and stable radiological and functional outcomes are achieved especially in selected patients.

International Society for the Advancement of Spine Surgery Policy 2020 Update-Minimally Invasive Surgical Sacroiliac Joint Fusion (for Chronic Sacroiliac Joint Pain): Coverage Indications, Limitations, and Medical Necessity

The index 2014 International Society for the Advancement of Spine Surgery Policy Statement-Minimally Invasive Surgical Sacroiliac Joint Fusion-was generated out of necessity to provide an International Classification of Diseases, Ninth Revision (ICD-9)-based background and emphasize tools to ensure correct diagnosis. A timely ICD-10-based 2016 update provided a granular threshold selection with improved level of evidence and a more robust and relevant database (Appendix Table A1). As procedures and treatment options have evolved, this 2020 update reviews and analyzes the expanding evidence base and provides guidance relating to differences between the lateral and dorsal surgical procedures for minimally invasive surgical sacroiliac joint fusion.

The "Kickstand Rod" Technique for Coronal Imbalance in Patients With Spinal Deformity: A Case Report With Review of Literature

Coronal imbalance is a type of spinal deformity with deviation from midline in the coronal plane. It is challenging to correct even in the hands of experienced spine surgeons. Many conventional techniques lead to unsuccessful results or complications. However, the incorporation of “kickstand rod” (KR) instrumentation is now understood to provide a more supported coronal correction and improve spinal deformities. Sometimes it can be used to provide additional spinal support in instances where spinal fusion has already occurred. The KR is placed from a posterior approach along the lateral spine from lumbar spine to ilium and exerts distraction forces that counteract misaligned spinal segments. Our objective is to present a clinical case example with a brief review of literature. Herein, we present a case of a 62-year-old male with the development of significant coronal imbalance following his posterior lumbosacral instrumentation and fusion 11 years prior to presentation. KR supplementation to his hardware improved his functional outcome significantly. Further, we provide a literature review of the surgical characteristics, indications, and functional outcomes of KR instrumentation. A term search of “kickstand rod” was performed in PubMed, and relevant English language publications were included. The literature search yielded only six publications. A total of 45 patients across three studies were assessed. A mean postoperative coronal balance magnitude of 26.83 mm was calculated compared to the preoperative coronal magnitude of 64.16 mm. Results also showed only four cases of intraoperative or postoperative complications. Moreover, the presented case reported successful KR implementation without any intraoperative complications. KR instrumentation is a safe and effective technique for coronal imbalance correction. The results show favorable outcomes in terms of coronal adjustment and low complication rates. Nevertheless, we caution the fact that further studies are warranted with long-term follow-ups.