Sacropelvic Fixation Research Articles

Historical Perspectives on the Evolution of Spino-Pelvic Fixation and its Implications on Clinical Care A Narrative Review.

Broad narrative review. To review and summarize the evolution of spinopelvic fixation (SPF) and its implications on clinical care. A thorough review of peer-reviewed literature was performed on the historical evolution of sacropelvic fixation techniques and their respective advantages and disadvantages. The sacropelvic junction has been a long-standing challenge due to a combination of anatomic idiosyncrasies and very high biomechanical forces. While first approaches of fusion were determinated by many material and surgical technique-related limitations, the modern idea of stabilization of the lumbosacral junction was largely initiated by the inclusion of the ilium into lumbosacral fusion. While there is a wide spectrum of indications for SPF the chosen technique remains is defined by the individual pathology and surgeons' preference. By a constant evolution of both instrumentation hardware and surgical technique better fusion rates paired with improved clinical results could be achieved.

Sacropelvic Fixation with Porous Fusion/Fixation Screws: A Technical Note and Retrospective Review

ObjectiveThe goal of this study was to analyze our initial experience using a novel porous fusion/fixation screw (PFFS) for pelvic fixation, and to determine our rate of screw malposition requiring intraoperative repositioning. MethodsWe reviewed 83 consecutive patients who underwent sacropelvic fixation with PFFS at our institution from 6/1/2022-6/30/2023 using intraoperative CT-based computer-assisted navigation (CAN) via an open posterior approach. Following PFFS insertion, intraoperative CT scans were obtained to assess screw positioning. Demographic data was collected, and operative reports and patient images were reviewed to determine what implants were used and if any PFFS required repositioning. Results74 patients (26M:48F) were included, and 57 (77.0%) had a prior sacroiliac joint or lumbar spine surgery. A stacked screw configuration was used in 62/74 cases (83.8%). A total of 235 PFFS were used and six (2.6%) were malpositioned. Of 88 cephalic screws placed in stacked configuration, 4 were malpositioned (4.5%); and 1/123 caudal screws were malpositioned (0.8%). One of 24 SAI screws placed in a stand-alone configuration was malpositioned (4.2%). Malpositions included four medial, one lateral, and one inferior; and all were revised intraoperatively without major sequela. ConclusionsAlthough PFFS are larger than traditional sacropelvic fixation screws, stacked SAI instrumentation can be done safely with CAN. We found a low malposition rate in our initial series of patients, the majority being the cephalad screw in a stacked configuration. This isn’t surprising, as these are placed after the caudal screws which reduces the available corridor size and increases the placement difficulty.

Effects of Minimally Invasive Lateral Lumbar Interbody Fusion with Accessory Rod Technique on Rod Fracture in Adult Spinal Deformity Surgery: Analysis of 239 Patients.

A retrospective study. To analyze factors associated with rod fracture (RF) in adult spinal deformity (ASD), and to assess whether the accessory rod (AR) technique can reduce RF occurrence in deformity correction in the setting of minimally invasive lateral lumbar interbody fusion (LLIF). Instrumentation failure is the most common reason for revision surgery in ASD. Several RF reduction methods have been introduced. However, there are insufficient studies on postoperative RF after deformity correction using minimally invasive LLIF. This study included 239 patients (average age 71.4y and a minimum 2-year follow-up) with ASD who underwent long-segment fusion from T10 to sacrum with sacropelvic fixation. Patients were classified into the non-RF group and the RF group. After logistic regression analysis of the risk factors for RF, subgroup analyses were performed: pedicle subtraction osteotomy (PSO) with two-rod (P2 group) versus PSO with two-rod and AR (P4 group), and LLIF with two-rod (L2 group) versus LLIF with two-rod and AR (L4 group). RF occurred in 50 patients (21%) at an average of 25 months. RF occurred more frequently in patients who underwent PSO than in those who underwent LLIF ( P =0.002), and the use of the AR technique was significantly higher in the non-RF group ( P <0.05).Following logistic regression analysis, preoperative PI-LL mismatch, PSO, and the AR technique were associated with RF. In subgroup analyses, RF incidence was 65% (24/37 cases) of the P2 group, 8% (4/51 cases) of the P4 group, and 21% (22/105 cases) of the L2 group. In the L4 group, there was no RF. Minimally invasive multilevel LLIF with the AR technique is capable of as much LL correction as conventional PSO and appears to be an effective method for reducing RF.

Sacropelvic Fixation for Adult Deformity Surgery Comparing Iliac Screw and Sacral 2 Alar-Iliac Screw Fixation: Systematic Review and Updated Meta-Analysis.

Two commonly used techniques for spinopelvic fixation in adult deformity surgery are iliac screw (IS) and sacral 2 alar-iliac screw (S2AI) fixations. In this article, we systematically meta-analyzed the complications of sacropelvic fixation for adult deformity surgery comparing IS and S2AI. The PubMed, Embase, Web of Science, and Cochrane clinical trial databases were systematically searched until March 29, 2023. The proportion of postoperative complications, including implant failure, revision, screw prominence, and wound complications after sacropelvic fixation, were pooled with a random-effects model. Subgroup analyses for the method of sacropelvic fixation were conducted. Ten studies with a total of 1,931 patients (IS, 925 patients; S2AI, 1,006 patients) were included. The pooled proportion of implant failure was not statistically different between the IS and S2AI groups (21.9% and 18.9%, respectively) (p = 0.59). However, revision was higher in the IS group (21.0%) than that in the S2AI group (8.5%) (p = 0.02). Additionally, screw prominence was higher in the IS group (9.6%) than that in the S2AI group (0.0%) (p < 0.01), and wound complication was also higher in the IS group (31.7%) than that in the S2AI group (3.9%) (p < 0.01). IS and S2AI fixations showed that both techniques had similar outcomes in terms of implant failure. However, S2AI was revealed to have better outcomes than IS in terms of revision, screw prominence, and wound complications.

Radiographic outcomes following surgical correction for lumbar degenerative kyphosis: the impact of supine pelvic tilt.

Lumbar degenerative kyphosis (LDK), a flexible deformity, is a common form of sagittal imbalance in Asian countries. Assessing a patient's spine prior to surgery by using positional radiographs is becoming more crucial in determining surgical planning to achieve favorable clinical and radiographic outcomes, especially in patients with flexible deformities. This study aims to identify radiographic characteristics of supine pelvic tilt (sPT) and its relation to mechanical failure (MF) following LDK correction. A single-center, single-surgeon retrospective analysis was performed in patients who underwent LDK correction with sacropelvic fixation between January 2014 and May 2019. Patients were grouped into pelvic match and mismatch groups according to the difference between postoperative pelvic tilt (PT) and sPT. Demographic, surgical, and radiographic parameters were compared. Chronological change of PT was assessed by comparing preoperative, supine, immediate postoperative, and final PT. Baseline demographics and sagittal alignments were similar between PT match (n = 25) and mismatch (n = 42) groups (p > 0.05). There was a significant difference in the rate of MF between PT match and mismatch groups (4% vs 31%, p = 0.021). Multivariable analysis demonstrated that after including control variables, PT mismatch was independently associated with the likelihood of MF development (OR 33.42, p = 0.04). sPT reflects postoperative PT changes; therefore, supine imaging may represent a tool that could be used for preoperative decision-making in patients with LDK or possibly those with flexible adult spinal deformity. PT mismatch > 10° or < 0° is a significant risk factor for MF following correction of LDK. Measurement of sPT would aid surgeons in optimal preoperative planning and in minimizing catastrophic MF following deformity correction surgery.

Stability and Instrumentation Stresses Among Sacropelvic Fixation Techniques With Novel Porous Fusion/Fixation Implants: A Finite Element Study.

Sacropelvic fixation is frequently combined with thoracolumbar instrumentation for correcting spinal deformities. This study aimed to characterize sacropelvic fixation techniques using novel porous fusion/fixation implants (PFFI). Three T10-pelvis finite element models were created: (1) pedicle screws and rods in T10-S1, PFFI bilaterally in S2 alar-iliac (S2AI) trajectory; (2) fixation in T10-S1, PFFI bilaterally in S2AI trajectory, triangular implants bilaterally above the PFFI in a sacro-alar-iliac trajectory (PFFI-IFSAI); and (3) fixation in T10-S1, PFFI bilaterally in S2AI trajectory, PFFI in sacro-alar-iliac trajectory stacked cephalad to those in S2AI position (2-PFFI). Models were loaded with pure moments of 7.5 Nm in flexion-extension, lateral bending, and axial rotation. Outputs were compared against 2 baseline models: (1) pedicle screws and rods in T10-S1 (PED), and (2) pedicle screws and rods in T10-S1, and S2AI screws. PFFI and S2AI resulted in similar L5-S1 motion; adding another PFFI per side (2-PFFI) further reduced this motion. Sacroiliac joint (SIJ) motion was also similar between PFFI and S2AI; PFFI-IFSAI and 2-PFFI demonstrated a further reduction in SIJ motion. Additionally, PFFI reduced max stresses on S1 pedicle screws and on implants in the S2AI position. The study shows that supplementing a long construct with PFFI increases the stability of the L5-S1 and SIJ and reduces stresses on the S1 pedicle screws and implants in the S2AI position. The findings suggest a reduced risk of pseudarthrosis at L5-S1 and screw breakage. Clinical studies may be performed to demonstrate applicability to patient outcomes. Not applicable (basic science study).

Direct Iliac Screw vs Sacral-2-Alar-Iliac Screws Technique for Sacropelvic Fixation: Technical Nuances and a Review of the Literature.

Sacropelvic (SP) fixation is the immobilization of the sacroiliac joint to attain lumbosacral fusion and prevent distal spinal junctional failure. SP fixation is indicated in numerous spinal conditions (eg, scoliosis, multilevel spondylolisthesis, spinal/sacral trauma, tumors, or infections). Many SP fixation techniques have been described in the literature. Currently, the most used surgical techniques for SP fixation are direct iliac screws and sacral-2-alar-iliac screws. There is currently no consensus in the literature on which technique carries more favorable clinical outcomes. In this review, we aim to assess the available data on each technique and discuss their respective advantages and disadvantages. We will also present our experience with a modification of direct iliac screws using a subcrestal approach and outline the future prospects of SP fixation.

Biomechanical evaluation of multiple pelvic screws and multirod construct for the augmentation of lumbosacral junction in long spinal fusion surgery.

Background: Posterior long spinal fusion was the common procedure for adult spinal deformity (ASD). Although the application of sacropelvic fixation (SPF), the incidence of pseudoarthrosis and implant failure is still high in long spinal fusion extending to lumbosacral junction (LSJ). To address these mechanical complications, advanced SPF technique by multiple pelvic screws or multirod construct has been recommended. This was the first study to compare the biomechanical performance of combining multiple pelvic screws and multirod construct to other advanced SPF constructs for the augmentation of LSJ in long spinal fusion surgery through finite element (FE) analysis. Methods: An intact lumbopelvic FE model based on computed tomography images of a healthy adult male volunteer was constructed and validated. The intact model was modified to develop five instrumented models, all of which had bilateral pedicle screw (PS) fixation from L1 to S1 with posterior lumbar interbody fusion and different SPF constructs, including No-SPF, bilateral single S2-alar-iliac (S2AI) screw and single rod (SS-SR), bilateral multiple S2AI screws and single rod (MS-SR), bilateral single S2AI screw and multiple rods (SS-MR), and bilateral multiple S2AI screws and multiple rods (MS-MR). The range of motion (ROM) and stress on instrumentation, cages, sacrum, and S1 superior endplate (SEP) in flexion (FL), extension (EX), lateral bending (LB), and axial rotation (AR) were compared among models. Results: Compared with intact model and No-SPF, the ROM of global lumbopelvis, LSJ, and sacroiliac joint (SIJ) was decreased in SS-SR, MS-SR, SS-MR, and MS-MR in all directions. Compared with SS-SR, the ROM of global lumbopelvis and LSJ of MS-SR, SS-MR, and MS-MR further decreased, while the ROM of SIJ was only decreased in MS-SR and MS-MR. The stress on instrumentation, cages, S1-SEP, and sacrum decreased in SS-SR, compared with no-SPF. Compared with SS-SR, the stress in EX and AR further decreased in SS-MR and MS-SR. The most significantly decreased ROM and stress were observed in MS-MR. Conclusion: Both multiple pelvic screws and multirod construct could increase the mechanical stability of LSJ and reduce stress on instrumentation, cages, S1-SEP, and sacrum. The MS-MR construct was the most adequate to reduce the risk of lumbosacral pseudarthrosis, implant failure, and sacrum fracture. This study may provide surgeons with important evidence for the application of MS-MR construct in the clinical settings.

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.

Accuracy and Feasibility of Bedrock Configuration Utilizing Mazor X Navigation System

<h3>Research Objectives</h3> To prove accuracy and feasibility of utilizing navigation for implantation of S2AI screws and triangular titanium rods in the bedrock configuration during open sacro-pelvic fixation in multilevel spinal fusion for adult spinal deformity. <h3>Design</h3> Retrospective chart review. <h3>Setting</h3> Single center, ambulatory care. <h3>Participants</h3> 18 adult multilevel spinal deformity patients. <h3>Interventions</h3> Reviewed consecutive cases where bilateral S2AI and TTRs were placed in an open approach from 10/2019-9/2020. Patients had preop CT scan for implant planning utilizing Mazor X. S2AI screws were planned into the caudal pelvic teardrop with TTRs placed 1cm proximal and cephalad. <h3>Main Outcome Measures</h3> Preop implant trajectory vs. postop implant placement. <h3>Results</h3> There was no significant difference for the caudal angle in the sagittal plane between pre- and post-operative TTRs and S2AI screws (31.33° ± 3.87° vs. 30.27° ± 3.40°, P = 0.24 and 39.34° ± 2.67° vs 39.32° ± 2.92°, P = 0.98, respectively). For the horizontal angle in the coronal plane there were no significant differences between the pre- and post-operative measurements for the TTRs placed on either the left or right side (38.44° ± 2.49° vs. 40.28° ± 2.88°, P = 0.09 and 40.03° ± 2.45° vs. 38.83° ± 1.85°, P = 0.23; respectively) or for the S2AI screws (36.92° ± 2.76° vs. 38.65° ± 3.19°, P = 0.15 and 39.06° ± 2.35° vs. 38.48° ± 2.24°, P = 0.62; respectively). There were no intraoperative complications and no implants had to be re-positioned. <h3>Conclusions</h3> Placing concomitant bilateral S2AI screws and TTRs in an open approach during multilevel deformity surgery is both feasible and accurate using the Mazor X navigation system. <h3>Author(s) Disclosures</h3> None.

High-Demand Spinal Deformity With Multi-Rod Constructs and Porous Fusion/Fixation Implants: A Finite Element Study.

Basic science (finite element analysis). Pedicle subtraction osteotomy (PSO) at L5 is an effective treatment for sagittal imbalance, especially in select cases of patients showing kyphosis with the apex at L4-L5 but has been scarcely investigated. The aim of this study was to simulate various "high-demand" instrumentation approaches, including varying numbers of rods and sacropelvic implants, for the stabilization of a PSO at L5. A finite element model of T10-pelvis was modified to simulate posterior fixation with pedicle screws and rods from T10 to S1, alone or in combination with an L5 PSO. Five additional configurations were then created by employing rods and novel porous fusion/fixation implants across the sacroiliac joints, in varying numbers. All models were loaded using pure moments of 7.5Nm in flexion-extension, lateral bending, and axial rotation. The osteotomy resulted in a general increase in motion and stresses in posterior rods and S1 pedicle screws. When the number of rods was varied, three- and four-rod configurations were effective in limiting the maximal rod stresses; values approached those of posterior fixation with no osteotomy. Maximum stresses in the accessory rods were similar to or less than those observed in the primary rods. Multiple sacropelvic implants were effective in reducing range of motion, particularly of the SIJ. Multi-rod constructs and sacropelvic fixation generally reduced maximal implant stresses and motion in comparison with standard posterior fixation, suggesting a reduced risk of rod breakage and increased joint stability, respectively, when a high-demand construct is utilized for the correction of sagittal imbalance.

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

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

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).

Is L5/S1 interbody fusion necessary in long-segment surgery for adult degenerative scoliosis? A systematic review and meta-analysis.

There is no consensus regarding the best surgical strategy at the lumbosacral junction (LSJ) in long constructs for adult spinal deformity (ASD). The use of interbody fusion (IF) has been advocated to increase fusion rates, with additional pelvic fixation (PF) typically recommended. The actual benefit of IF even when extending to the pelvis, however, has not been vigorously analyzed. The goal of this work was to better understand the role of IF, specifically with respect to arthrodesis, when extending long constructs to the ilium. A systematic review of the PubMed and Cochrane databases was performed to identify the relevant studies in English, addressing the management of LSJ in long constructs (defined as ≥ 5 levels) in ASD. The search terms used were as follows: "Lumbosacral Junction," "Long Constructs," "Long Fusion to the Sacrum," "Sacropelvic Fixation," "Interbody Fusion," and "Iliac Screw." The authors excluded technical notes, case reports, literature reviews, and cadaveric studies; pediatric populations; pathologies different from ASD; studies not using conventional techniques; and studies focused only on alignment of different levels. The PRISMA protocol was used. The authors found 12 retrospective clinical studies with a total of 1216 patients who were sorted into 3 different categories: group 1, using PF or not (n = 6); group 2, using PF with or without IF (n = 5); and group 3, from 1 study comparing anterior lumbar interbody fusion versus transforaminal lumbar interbody fusion. Five studies in group 1 and 4 in group 2 had pseudarthrosis rate as primary outcome and were selected for a quantitative analysis. Forest plots were used to display the risk ratio, and funnel plots were used to look at the risk of publication bias. The summary risk ratios were 0.36 (0.23-0.57, p < 0.001) and 1.03 (0.54-1.96, p = 0.94) for the PF and IF, respectively; there is a protective effect of overall pseudarthrosis for using PF in long constructs for ASD surgeries, but not for using IF. The long-held contention that L5/S1 IF is always advantageous in long-construct deformity surgery is not supported by the current literature. Based on the findings from this systematic review and meta-analysis, PF with or without additional L5/S1 interbody grafting demonstrates similar overall construct pseudarthrosis rates. The added risk and costs associated with IF, therefore, should be more closely considered on a case-by-case basis.

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.

The relationship between S1 screw loosening and postoperative outcome in patients with degenerative lumbar scoliosis

BackgroundWhen choosing S1 as the lowest level of instrumentation, there are many complications may come out such as S1 screw loosening. Facing this problem, there has been various techniques for the protection of S1 screw including sacropelvic fixation, bicortical or tricortical insertion of S1 screw.ObjectiveThis study aimed to explore the risk factors for the S1 screw loosening, then to demonstrate the relationship between S1 screw loosening and postoperative outcome for patients with degenerative lumbar scoliosis (DLS).MethodsPatients who underwent lumbosacral fixation for DLS were evaluated retrospectively. They were divided into two groups according to the S1 pedicle screw at the follow-up. Age, gender, bone mineral density, body mass index, history of smoking, the number of instrumented levels, comorbidities, complications and radiological parameters were collected. We established logistic regression analysis to determine independent risk factors for S1 screw loosening and multiple linear regression to identify whether S1 screw loosening would influence postoperative clinical outcome.ResultsS1 screw loosening rate was up to 41.0% (32/78). Patients were older in the S1 screw loosening group than those in the control group (P < 0.05). Compared with the control group, the rate of osteoporosis was higher in screw loosening group than that in the control group (P < 0.05). Older age and osteoporosis were independent risk factors for S1 screw loosening (P < 0.05). In the screw loosening group, the rate of hypertension was higher than that in the control group (P < 0.05). The relationship of S1 screw loosening and ODI was not significant in the multiple linear regression (P > 0.05). The clinical outcome was similar in the S1 screw loosening group and control group (P > 0.05).ConclusionOlder age and osteoporosis are independent risk factors for the S1 screw loosening. Patients with complication of S1 screw loosening are not always along with worse clinical outcome. We should consider potential benefit, complications and medical cost when choosing the lowest instrumented vertebrae for patients with DLS.

Ball Tip Technique for S2AI Screw Placement in Sacropelvic Fixation: A Comparative Study with Conventional Freehand Technique.

ObjectiveTo evaluate the efficiency of the ball tip technique for S2AI screw placement and introduce this technique.MethodsSixty‐three patients who underwent pelvic fixation with S2AI screws were retrospectively reviewed. They were 29 males and 34 females with an average age of 59.6 ± 12.5 years. Among these patients, 35 patients (14 males and 21 females with an average age of 58.8 ± 11.3 years) received ball tip technique and 28 patients (15 males and 13 females with an average age of 63.7 ± 12.6 years) received conventional freehand technique. Ball tip technique was used in ball tip technique group. After a pedicle probe just penetrated the sacroiliac joint, a ball‐tipped probe consisting of a ball shaped metal tip with a flexible shaft was malleted to make a guide track within ilium. This ball‐tipped probe could bend automatically away from the cortex and forward through the cancellous bone when the tip met the cortical lamina of ilium, which can avoid penetration. After repeating the procedures, a guide hole was gradually formed. S2AI screw was inserted along the guide hole after tapping. In the conventional freehand group, S2AI screw was placed according to the conventional method. Postoperative computed tomography (CT) was used to assess the accuracy of screws. The time cost of screw insertion and screw‐related complications were recorded. Independent t‐test was used to compare the time cost between ball tip group and conventional freehand group. A chi‐square test was used to compare the accuracies of the ball tip group with the conventional group.ResultsThere were 35 patients (70 S2AI screws) in ball tip group and 28 patients (56 S2AI screws) in conventional freehand group. No screw‐related complication occurred in all patients. Time costs were 9.8 ± 4.5 mins in ball tip group and 20.2.0 + 8.6 mins in conventional freehand group, respectively (P < 0.05). Four screws penetrated iliac cortex in the ball tip group vs 10 screws in conventional freehand group (5.7% vs 17.9%) (P < 0.05).ConclusionsThe ball tip technique enhances the accuracy of screw placement and has less time cost compared with conventional freehand technique.

The Technique for Performing Posterior Vertebral Column Resection with En-Bloc Fixation/Reduction in Adult Spine Deformity Surgery.

All surgeries are performed with the patient in the prone position under continuous neuromonitoring. The posterior approach to the spine and spinal instrumentation are performed in a standard fashion3. The S2-alar-iliac technique is utilized for sacropelvic fixation when indicated4. A minimum of 6 fixation points above and 6 below the level of resection are obtained, resulting in 2 instrumented blocs proximally and distally. A wide decompressive laminectomy with foraminotomies is then performed at the resection level, allowing for visualization of the spinal cord and exiting nerve roots. In the thoracic spine, disarticulating 3 to 4 cm of the medial rib at the resection level allows for better visualization and accessibility. Temporary fixation is then obtained by a unilateral rod spanning the osteotomy site. Focus is then directed toward the inferior and superior articular facets and pedicle, which are resected in a piecemeal manner from lateral to medial. Care must be taken to avoid damaging nearby nerve roots, especially at the inferomedial aspect of the pedicle. Cancellous bone removal from the vertebral body is then performed in a piecemeal manner through a lateral extra-cavitary approach from each side. This step necessitates transferring temporary fixation to the contralateral side in order to ensure adequate resection bilaterally. Posterior cortex is then resected. The anterior dura is carefully freed of any ligament or bone. Resection of the discs above and below the resection level is then performed, and the end plates are prepared for arthrodesis. The next step is to measure the defect. The sizing of the cages must be kept in line with the desired degree of correction, preventing overlengthening of the spinal column and subsequent stretching of the spinal cord. An en-bloc reduction-fixation across the osteotomy site is performed with use of intercalary connecting rods in order to achieve the desired correction. In situ benders at this stage may be utilized to manipulate the intercalary rods in order to widen the resection space anteriorly. The rods will subsequently be replaced. This technique minimizes stress on the junctional segments through load distribution across the various fixation points in the proximal and distal blocs. Finally, after decortication of the posterior elements, the bone graft is placed prior to layered closure in the standard manner. Alternative treatments to the pVCR include a standard pedicle-subtraction osteotomy. A standard pedicle-subtraction osteotomy offers a substantial amount of correction; however, correction is limited to the sagittal plane because the wedge osteotomy is hinged on the anterior cortex. This limitation makes the pVCR a better candidate for patients with severe biplanar deformities. pVCR is a complicated and technically challenging procedure that offers substantial correction in the coronal and sagittal planes for patients with rigid spinal deformities. It has also been shown to significantly improve patient quality of life5 Complication rates, however, are reportedly as high as 25% among older patients with poor physiologic reserve, with postoperative risks including medical complications, neurological deficiencies, surgery-related complications and others6. Previous studies have demonstrated improved outcomes with increasing surgeon experience2. Medial rib resection in the thoracic spine allows easy access to the lateral vertebral column.En-bloc fixation-reduction minimizes fixation failure above and below the level of resection and provides a rigid foundation during the correction maneuver.Ensure that the anterior column is disconnected all the way across in order to avoid excessive shortening of the spinal cord and the potential neurologic sequelae.Complete resection of the posterior cortex and scar tissue anterior to the dural sac is required prior to the correction maneuver.Ensure an adequate number of fixation points above and below the resection level.

Letter: Sacroplasty Augmentation of Instrumented Pelvic Reconstruction After High Sacrectomy: A Technical Case Report.

Letter: Sacroplasty Augmentation of Instrumented Pelvic Reconstruction After High Sacrectomy: A Technical Case Report.