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

OBJECTIVE: The 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. METHODS: We 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. RESULTS: 74 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. CONCLUSIONS: Although 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.

Spine surgeon versus AI algorithm full-length radiographic measurements: a validation study of complex adult spinal deformity patients.

INTRODUCTION: Spinal measurements play an integral role in surgical planning for a variety of spine procedures. Full-length imaging eliminates distortions that can occur with stitched images. However, these images take radiologists significantly longer to read than conventional radiographs. Artificial intelligence (AI) image analysis software that can make such measurements quickly and reliably would be advantageous to surgeons, radiologists, and the entire health system. MATERIALS AND METHODS: Institutional Review Board approval was obtained for this study. Preoperative full-length standing anterior-posterior and lateral radiographs of patients that were previously measured by fellowship-trained spine surgeons at our institution were obtained. The measurements included lumbar lordosis (LL), greatest coronal Cobb angle (GCC), pelvic incidence (PI), coronal balance (CB), and T1-pelvic angle (T1PA). Inter-rater intra-class correlation (ICC) values were calculated based on an overlapping sample of 10 patients measured by surgeons. Full-length standing radiographs of an additional 100 patients were provided for AI software training. The AI algorithm then measured the radiographs and ICC values were calculated. RESULTS: ICC values for inter-rater reliability between surgeons were excellent and calculated to 0.97 for LL (95% CI 0.88-0.99), 0.78 (0.33-0.94) for GCC, 0.86 (0.55-0.96) for PI, 0.99 for CB (0.93-0.99), and 0.95 for T1PA (0.82-0.99). The algorithm computed the five selected parameters with ICC values between 0.70 and 0.94, indicating excellent reliability. Exemplary for the comparison of AI and surgeons, the ICC for LL was 0.88 (95% CI 0.83-0.92) and 0.93 for CB (0.90-0.95). GCC, PI, and T1PA could be determined with ICC values of 0.81 (0.69-0.87), 0.70 (0.60-0.78), and 0.94 (0.91-0.96) respectively. CONCLUSIONS: The AI algorithm presented here demonstrates excellent reliability for most of the parameters and good reliability for PI, with ICC values corresponding to measurements conducted by experienced surgeons. In future, it may facilitate the analysis of large data sets and aid physicians in diagnostics, pre-operative planning, and post-operative quality control.

Complications of the Use Allograft in 1- or 2-Level Anterior Cervical Discectomy and Fusion: A Systematic Review.

Study Design: Systematic literature reviewObjective: To critically analyze the literature and describe the complications associated with the use of allograft in 1- or 2- level anterior cervical discectomy and fusion (ACDF)Methods: A systematic search of PubMed/MEDLINE, EMBASE, and ClinicalTrials.gov databases was conducted for literature published between January 2000 and August 2020 reporting complications associated with the use of allograft in 1- or 2- level ACDF.Results: From 584 potentially relevant citations, 21 met the inclusion criteria (4 randomized controlled trials (RCT), 4 prospective, and 13 retrospective studies). The patient number varied between 26 and 463 in comparative studies (RCT and non-RCT) and between 29 and 345 in non-comparative studies. Fusion rate was reported in 14 studies and ranged between 68.5-100%. The most frequently reported complication was post-operative dysphagia or dysphonia, with incidences ranging between .5% and 14.4%. Revision surgery was the second most reported complication (14 studies) and ranged between 0% and 10.3%. Wound-related complications were reported in 6 studies and ranged between 0% and 22.8%.Conclusion: The overall reporting of complications was low with very few comparative studies. Reported complications with allografts are within the range of other osteobiologics and autografts and in most cases may not attributable to the use of osteobiologics and may be complications of the procedure itself. Comparative studies with a more robust methodology analyzing complications with allograft and other osteobiologics are needed to inform current practice with strong recommendations.

AO Spine Guideline for the Use of Osteobiologics (AOGO) in Anterior Cervical Discectomy and Fusion for Spinal Degenerative Cases.

STUDY DESIGN: Guideline. OBJECTIVES: To develop an international guideline (AOGO) about the use of osteobiologics in anterior cervical discectomy and fusion (ACDF) for treating degenerative spine conditions. METHODS: The guideline development process was guided by AO Spine Knowledge Forum Degenerative (KF Degen) and followed the Guideline International Network McMaster Guideline Development Checklist. The process involved 73 participants with expertise in degenerative spine diseases and surgery from 22 countries. Fifteen systematic reviews were conducted addressing respective key topics and evidence was collected. The methodologist compiled the evidence into GRADE Evidence-to-Decision frameworks. Guideline panel members judged the outcomes and other criteria and made the final recommendations through consensus. RESULTS: Five conditional recommendations were created. A conditional recommendation is about the use of allograft, autograft or a cage with an osteobiologic in primary ACDF surgery. Other conditional recommendations are about the use of osteobiologic for single- or multi-level ACDF, and for hybrid construct surgery. It is suggested that surgeons use other osteobiologics rather than human bone morphogenetic protein-2 (BMP-2) in common clinical situations. Surgeons are recommended to choose 1 graft over another or 1 osteobiologic over another primarily based on clinical situation, and the costs and availability of the materials. CONCLUSION: This AOGO guideline is the first to provide recommendations for the use of osteobiologics in ACDF. Despite the comprehensive searches for evidence, there were few studies completed with small sample sizes and primarily as case series with inherent risks of bias. Therefore, high-quality clinical evidence is demanded to improve the guideline.

Comparative Complications Associated With BMP Use In Patients Undergoing ACDF for Degenerative Spinal Conditions: Systematic Review and Meta-Analysis.

STUDY DESIGN: Systematic Review and Meta-Analysis. OBJECTIVES: To compare complication incidence in patients with or without the use of recombinant human Bone Morphogenic Protein-2 (BMP2) undergoing anterior cervical discectomy and fusion (ACDF) for degenerative conditions. METHODS: A systematic search of eight online databases was conducted using PRISMA guidelines. Inclusion criteria included English language studies with a minimum of 10 adult patients undergoing instrumented ACDF surgery for a degenerative spinal condition in which BMP2 was used in all patients or one of the treatment arms. Studies with patients undergoing circumferential fusions, with non-degenerative indications, or which did not report post-operative complication data were excluded. Patients with and without BMP2 were compared in terms of the incidence of dysphagia/dysphonia, anterior soft tissue complications (hematoma, seroma, infection, dysphagia/dysphonia), nonunion, medical complications, and new neurologic deficits. RESULTS: Of 1832 preliminary search results, 27 manuscripts were included. Meta-analysis revealed the relative risk of dysphagia or dysphonia (RR = 1.39, CI 95% 1.18 - 1.64, P = <.001), anterior soft tissue complications (RR = 1.43, CI 95% 1.25-1.64, P = <.001), and medical complications (RR = 1.32, CI 95% 1.06-1.66, P = .013) were statistically significant in the BMP2 group while the relative risk of non-union (RR = .5, CI 95% .23 - 1.13, P = .09) trended lower in the BMP2 group. Neurological deficit (RR = 1.06, CI 95% .82-1.37, P = .66), and additional medical complications (RR = 1.53, CI 95% .98-2.38, P = .06) were not found to be statistically different between the groups. CONCLUSIONS: This meta-analysis identified a high rate of arthrodesis when BMP2 was used in ACDF, but confirmed increased rates of dysphagia and anterior soft tissue complications. Surgeons may consider reserving BMP2 implementation for cases with a high risk of non-union, and should be aware of the risk of airway compromise.

Do the Choice of Fusion Construct With and Without Autograft Influence the Fusion and Complication Rates in Patients Undergoing 1 or 2-Level Anterior Cervical Discectomy and Fusion Surgery? A PRISMA-Compliant Network Meta-Analysis.

STUDY DESIGN: Network meta-analysis. OBJECTIVES: To compare the fusion outcome and complications of different 1 or 2-level anterior cervical decompression and fusion (ACDF) constructs performed with and without the application of autografts. METHODS: We performed an independent and duplicate search in electronic databases including PubMed, Embase, Web of Science, Cochrane, and Scopus for relevant articles published between 2000 and 2020. We included comparative studies reporting fusion rate and complications with and without the use of autografts in ACDF across 5 different fusion constructs. A network meta-analysis was performed in Stata, categorized based on the type of fusion constructs utilized. Fusion constructs were ranked based on p-score approach and surface under cumulative ranking curve (SUCRA) scores. The confidence of results from the analysis was appraised with Cochrane's CINeMA approach. RESULTS: A total of 2216 patients from 22-studies including 6 Randomized Controlled Trials (RCTs) and 16 non-RCTs were included in network analysis. The mean age of included patients was 49.3 (±3.62) years. Based on our meta-analysis, we could conclude that use of autograft in 1- or 2-level ACDF did not affect the fusion and mechanical implant-related complications. The final fusion and mechanical complication rates were also not significantly different across the different fusion constructs. The use of plated constructs was associated with a significant increase in post-ACDF dysphagia rates [OR 3.42; 95%CI (.01,2.45)], as compared to stand-alone constructs analysed. CONCLUSION: The choice of fusion constructs and use of autografts does not significantly affect the fusion and overall complication rates following 1 or 2-level ACDF surgery.

Does A Hinged Operating Table Facilitate Sagittal Correction in Transforaminal Lumbar Interbody Fusion With Smith-Peterson Osteotomy? A Radiographic Analysis.

BACKGROUND: Osteotomies allow the restoration of appropriate sagittal alignment; however, closure of osteotomies can be challenging. Typical closure involves compressing pedicle screw heads across the rods, potentially causing screw loosening and failure. Motorized hinged operating tables are often used to assist with controlled closure of osteotomies without manual compression, but there is no published research quantifying the amount of correction provided solely by changes in the table angle. QUESTION/PURPOSE: What is the incremental amount of correction achieved by change in the table angle versus instrumented manipulation during osteotomy closure in transforaminal lumbar interbody fusion (TLIF) with Smith-Petersen osteotomy? METHODS: Sixty-one patients undergoing Smith-Peterson osteotomy and bilateral TLIF using a motorized hinged table from October 2019 to March 2022 were prospectively enrolled. Two patients did not undergo surgery, two did not have table extension, and seven did not have data collected intraoperatively because of disruptions in research protocols owing to the coronavirus-19 pandemic. Fifty patients (24 male, 26 female) who underwent a total of 73 osteotomies were included in the final analysis. The mean ± standard deviation age was 61 ±11 years, and the mean BMI was 31 ± 6 kg/m2. Patients were positioned prone on the table and flexed to 10° for decompression, Smith-Petersen osteotomy, and TLIF. The table was then extended in 5° increments, and radiographs were taken until 10° of extension was achieved or the osteotomy was fully closed. Changes in segmental lordosis across the operative site for each 5° increment were measured to the nearest degree by two reviewers. Intraclass correlation coefficients for segmental lordosis measurements at each table angle change were calculated as 0.97 to 0.98, with all p values < 0.001, indicating excellent agreement. RESULTS: Table change from 10° to 5° yielded a mean segmental lordosis change of 1.9° ± 1.5° (73 osteotomies), 5° to 0° yielded a change of 1.3° ± 0.9° (73 osteotomies), 0° to -5° yielded a change of 1.3° ± 1.0° (69 osteotomies), and -5° to -10° yielded a change of 1.1° ± 1.3° (61 osteotomies). Rod placement and compression yielded a mean 1.8° ± 2.0° of additional segmental lordosis. CONCLUSION: Using a motorized hinged table facilitated an average of 5.6° of total segmental lordosis correction during controlled Smith-Peterson osteotomy closure without the need for cantilevering forces across spinal instrumentation. Surgeons can use this technique to reduce the compression forces needed to close osteotomies, which could eliminate a potential source of complications.Level of Evidence Level II, therapeutic study.

Chance Fracture Pattern Presenting in Proximal Junctional Failure.

INTRODUCTION: We present a case series of proximal junctional failure due to a Chance-type fracture. METHODS: This is a retrospective review of patients who developed proximal junctional kyphosis because of Chance-type proximal junctional failure after spinal fusion for adult spinal deformity. RESULTS: Fifteen patients were identified (4M:11F). The average age was 61.4 years (range, 39 to 77). The mean time to fracture identification was 25.4 days (range, 3 to 65). The average number of levels instrumented was 6.7 (range, 2 to 17). No patients had antecedent trauma before fracture onset. In 67% of cases with a lumbar upper instrumented vertebra (UIV), there was overcorrection of lumbar lordosis (LL) and/or lower LL. The five cases with a lower thoracic UIV had undergone notable correction of preoperative thoracolumbar junction kyphosis. 14 of 15 patients were treated with extension of fusion. Pedicle screws at the fracture level were salvaged by changing to an anatomic trajectory. CONCLUSION: Continued pain at 6 to 12 weeks with radiographs showing an increased proximal junctional angle and cephalocaudal pedicle widening at the UIV should raise suspicion for this unique fracture pattern. A CT scan is recommended. Low bone density, LL and/or lower LL overcorrection, and selection of lower thoracic UIV in the setting of notable thoracolumbar junction correction may contribute to fracture risk.

Sacroiliac joint fusion navigation: how accurate is pin placement?

OBJECTIVE: Sacroiliac joint (SIJ) fusion utilizing intraoperative navigation requires a standard reference frame, which is often placed using a percutaneous pin. Proper placement ensures the correct positioning of SIJ fusion implants. There is currently no grading scheme for evaluation of pin placement into the pelvis. The purpose of this study was to evaluate the occurrence of ideal percutaneous pin placement into the posterior ilium during navigated SIJ fusion. METHODS: After IRB approval was obtained, electronic medical records and intraoperative computed tomography images of patients who underwent navigated SIJ fusion by the senior author between October 2013 and January 2020 were reviewed. A pin placement grading scheme and the definition of "ideal" placement were developed by the authors and deemed acceptable by fellow attending surgeons. Six attending surgeons completed two rounds of pin placement grading, and statistical analysis was conducted. RESULTS: Of 90 eligible patients, 73.3% had ideal pin placement, 17.8% medial/lateral breach, and 8.9% complete miss. Male patients were 3.7 times more likely to have ideal placement than females (p < 0.05). There was no relationship between BMI, SIJ fusion laterality, or pin placement laterality and ideal placement. Interobserver reliability was 0.72 and 0.70 in the first and second rounds, respectively, and defined as "substantial agreement." Intraobserver reliability ranged from 0.74 (substantial agreement) to 0.92 (almost perfect agreement). CONCLUSIONS: Nonideal pin placement occurred in 26.7% of cases, but a true "miss" into the sacrum was rare. Ideal pin placement was more likely in males and was not associated with BMI, SIJ fusion laterality, or pin placement laterality. The grading scheme developed has high intraobserver and interobserver reliability, indicating that it is reproducible and can be used for future studies. When placing percutaneous pins, surgeons must be aware of factors that can decrease placement accuracy, regardless of location.

Odontoid Fracture as Proximal Junctional Failure in Patients With Multilevel Spine Fusions.

STUDY DESIGN: Retrospective study. OBJECTIVE: Proximal junctional failure (PJF) commonly occurs as a recognized potential outcome of fusion surgery. Here we describe a unique series of patients with multilevel spine fusion including the cervical spine, who developed PJF as an odontoid fracture. METHODS: We performed a single site retrospective review of patients with prior fusion that included a cervical component, who presented with an odontoid fracture between 2012 and 2019. Radiographic measurements included C2-C7 SVA, C2-C7 lordosis, T1 slope, Occiput-C2 angle, proximal junctional kyphosis, and cervical mismatch. Associated fractures, medical comorbidities, and treatments were determined via chart review after IRB approval. RESULTS: Nine patients met inclusion criteria. 5 reported trauma with subsequent onset of pain. All patients sustained a Type II odontoid fracture. 5 with associated C1/Jefferson fractures. In all patients, pre-injury Occiput-C2 angle was outside normative range; C2-C7 SVA was greater than 4 cm in 6 patients; T1-slope minus cervical lordosis was greater than 18.5 degrees in 6 patients. 7 patients were treated operatively with extension of fusion to C1 and 2 patients declined operative treatment. CONCLUSION: In this series of 9 patients with multilevel fusion with type II odontoid fractures, all patients demonstrated abnormal pre-fracture sagittal alignment parameters and a greater than normal association of C1 fractures was noted. Further study is needed to establish the role of poor sagittal alignment with compensatory occiput-C2 angulation as a predisposing factor for odontoid fracture as a proximal junctional failure mechanism.

Catastrophic acute failure of pelvic fixation in adult spinal deformity requiring revision surgery: a multicenter review of incidence, failure mechanisms, and risk factors.

OBJECTIVE: There are few prior reports of acute pelvic instrumentation failure in spinal deformity surgery. The objective of this study was to determine if a previously identified mechanism and rate of pelvic fixation failure were present across multiple institutions, and to determine risk factors for these types of failures. METHODS: Thirteen academic medical centers performed a retrospective review of 18 months of consecutive adult spinal fusions extending 3 or more levels, which included new pelvic screws at the time of surgery. Acute pelvic fixation failure was defined as occurring within 6 months of the index surgery and requiring surgical revision. RESULTS: Failure occurred in 37 (5%) of 779 cases and consisted of either slippage of the rods or displacement of the set screws from the screw tulip head (17 cases), screw shaft fracture (9 cases), screw loosening (9 cases), and/or resultant kyphotic fracture of the sacrum (6 cases). Revision strategies involved new pelvic fixation and/or multiple rod constructs. Six patients (16%) who underwent revision with fewer than 4 rods to the pelvis sustained a second acute failure, but no secondary failures occurred when at least 4 rods were used. In the univariate analysis, the magnitude of surgical correction was higher in the failure cohort (higher preoperative T1-pelvic angle [T1PA], presence of a 3-column osteotomy; p < 0.05). Uncorrected postoperative deformity increased failure risk (pelvic incidence-lumbar lordosis mismatch > 10°, higher postoperative T1PA; p < 0.05). Use of pelvic screws less than 8.5 mm in diameter also increased the likelihood of failure (p < 0.05). In the multivariate analysis, a larger preoperative global deformity as measured by T1PA was associated with failure, male patients were more likely to experience failure than female patients, and there was a strong association with implant manufacturer (p < 0.05). Anterior column support with an L5-S1 interbody fusion was protective against failure (p < 0.05). CONCLUSIONS: Acute catastrophic failures involved large-magnitude surgical corrections and likely resulted from high mechanical strain on the pelvic instrumentation. Patients with large corrections may benefit from anterior structural support placed at the most caudal motion segment and multiple rods connecting to more than 2 pelvic fixation points. If failure occurs, salvage with a minimum of 4 rods and 4 pelvic fixation points can be successful.

Bilateral open sacroiliac joint fusion during adult spinal deformity surgery using triangular titanium implants: technique description and presentation of 21 cases.

OBJECTIVE: Pelvic fixation enhances long constructs during deformity surgery. Subsequent loosening of iliac screws and pain at the pelvis occur in as many as 29% of patients. Concomitant sacroiliac (SI) fusion may prevent potential pain and failure. The objective of this study was to describe a novel surgical technique and a single institution's experience using bilateral SI fusion during adult deformity surgery with S2-alar-iliac (S2AI) screws and triangular titanium rods (TTRs) placed with navigation. METHODS: The authors reviewed open SI joint fusions with TTR performed between August 2019 and March 2020. All patients underwent lumbosacral fusion through a midline approach and bilateral S2AI pelvic fixation in the caudal teardrop, followed by TTR placement just proximal and cephalad to the S2AI screws using intraoperative CT imaging guidance. RESULTS: Twenty-one patients were identified who received 42 TTRs, ranging in size from 7.0 × 65 mm to 7.0 × 90 mm. Three TTRs (7%) were malpositioned intraoperatively, and each was successfully repositioned during index surgery without negative sequelae. All breaches occurred in a medial and cephalad direction into the pelvis. Incremental operative time for adding TTR averaged 8 minutes and 33 seconds per implant. CONCLUSIONS: Image-guided open SI joint fusion with TTR during lumbosacral fusion is technically feasible. The bony corridor for implant placement is narrower cephalad, and implants tend to deviate medially into the pelvis. Detection of malpositioned implant is aided with intraoperative CT, but this can be salvaged. A prospective randomized clinical trial is underway that will better inform the impact of this technique on patient outcomes.

Acute failure of S2-alar-iliac screw pelvic fixation in adult spinal deformity: novel failure mechanism, case series, and review of the literature.

OBJECTIVE: Pelvic fixation with S2-alar-iliac (S2AI) screws is an established technique in adult deformity surgery. The authors' objective was to report the incidence and risk factors for an underreported acute failure mechanism of S2AI screws. METHODS: The authors retrospectively reviewed a consecutive series of ambulatory adults with fusions extending 3 or more levels, and which included S2AI screws. Acute failure of S2AI screws was defined as occurring within 6 months of the index surgery and requiring surgical revision. RESULTS: Failure occurred in 6 of 125 patients (5%) and consisted of either slippage of the rods or displacement of the set screws from the S2AI tulip head, with resultant kyphotic fracture. All failures occurred within 6 weeks postoperatively. Revision with a minimum of 4 rods connecting to 4 pelvic fixation points was successful. Two of 3 (66%) patients whose revision had less fixation sustained a second failure. Patients who experienced failure were younger (56.5 years vs 65 years, p = 0.03). The magnitude of surgical correction was higher in the failure cohort (number of levels fused, change in lumbar lordosis, change in T1-pelvic angle, and change in coronal C7 vertical axis, each p < 0.05). In the multivariate analysis, younger patient age and change in lumbar lordosis were independently associated with increased failure risk (p < 0.05 for each). There was a trend toward the presence of a transitional S1-2 disc being a risk factor (OR 8.8, 95% CI 0.93-82.6). Failure incidence was the same across implant manufacturers (p = 0.3). CONCLUSIONS: All failures involved large-magnitude correction and resulted from stresses that exceeded the failure loads of the set plugs in the S2AI tulip, with resultant rod displacement and kyphotic fractures. Patients with large corrections may benefit from 4 total S2AI screws at the time of the index surgery, particularly if a transitional segment is present. Salvage with a minimum of 4 rods and 4 pelvic fixation points can be successful.

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 fixation1-3. 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 strain5-7. Although pelvic instrumentation has been utilized to increase construct stiffness and fusion rates, pelvic fixation failure is frequently reported8,9. 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 studies12-14, 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 alone15-17 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 findings18,19. 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.

Is the Implant in Bone? The Accuracy of CT and Fluoroscopic Imaging for Detecting Malpositioned Pelvic Screw and SI Fusion Implants.

BACKGROUND: Spine fusions to the pelvis have been associated with increased strain to the sacroiliac joint (SI) and possibly continued postoperative low back pain. To minimize this, concomitant SI joint fusion at the time of lumbopelvic fixation has been advocated. This requires concomitant placement of sacral alar iliac screws (S2AI) for lumbopelvic fixation and triangular titanium rods (TTR) for the SI joint fusion. Traditionally, surgeons have mostly relied on fluoroscopic images to confirm final implant position and patient safety after pelvic instrumentation, although computer tomography (CT) has also been used. METHODS: We wanted to know which imaging modality, if any, was superior in helping to identify malpositioned implants during concomitant lumbopelvic fixation and SI joint fusion. We instrumented pelvic sawbones models with S2AI screws, TTR's, or both in the correct anatomic positions or malpositioned variants that led to known cortical breaches. Pelvic models were then imaged with fluoroscopy and CT, and the images assessed by blinded reviewers (spine surgeons and a musculoskeletal radiologist) for the presence of cortical breaches, the identity of the breached implant, and its direction. The responses of the blinded reviewers were then compared to the known position of the implants and Kappa coefficient calculated to determine agreement. RESULTS: We found that thorough evaluation of implant position with multiple fluoroscopic views (kappa 0.641) or CT imaging (kappa 0.906) allowed reviewers to assess implant position, identity, and breach direction. CONCLUSION: These findings suggest that intraoperative CT imaging allows surgeons to make the best decision regarding implant position prior to leaving the operating room, thus potentially improving patient safety and unplanned returns to the operating room.Level of Evidence: V.

Radiographic Factors Affecting Lordosis Correction After Transforaminal Lumbar Interbody Fusion With Unilateral Facetectomy.

BACKGROUND: The study design was a retrospective cohort study. The objective was to identify preoperative (preop) radiographic features that are associated with increased lordosis correction after transforaminal lumbar interbody fusion (TLIF). METHODS: We retrospectively reviewed a single surgeon series of TLIF performed at L4-5 since 2010. The surgical technique involved unilateral facetectomy and insertion of a banana-type cage. A total of 107 cases were available with plain radiographs, and 62 with a preop computed tomography (CT) scan. We compared segmental lordosis correction between the preop and 6-week postoperative radiographs. Patients were divided into groups of those with or without more than 5° lordosis correction. Radiographic features were then compared, and a multivariate analysis was performed. RESULTS: The mean lordosis correction of the entire cohort was 2.5° (range = -9° to 16°). The percentage of patients with a vacuum disc on the preop CT (40% vs 10%, P = 0.01) was higher in the group with greater than 5° lordosis correction, whereas the mean preop segmental lordosis (14.3° vs 18.6°) and the preop segmental disc angle (6.4° vs 8.4°) were both lower (P < 0.05 for each). The percentage of patients with a Meyerding grade of 2 or higher (28% vs 16%) trended higher but was not significant (P = 0.1). There was no significant difference in the mean body mass index, patient age, preop lumbar lordosis, or disc space height. CONCLUSIONS: Patients with a preop vacuum disc sign on CT scan or those with a more kyphotic disc space on preop radiographs were more likely to achieve lordosis correction. This information may be useful in preop planning. LEVEL OF EVIDENCE: 4. CLINICAL RELEVANCE: Unilateral TLIF is likely to be neutral or kyphogenic in patients with a segmental disc angle that is neutral or lordotic pre-operatively, but is likely to increase segmental lordosis in patients with a disc angle that is kyphotic pre-oepratively.

Surgeon Preference for Radiologist Interpretation of Deformity Radiographs-A Survey of Lumbar Spine Research Society Membership.

BACKGROUND: The radiologist interpretation of scoliosis films is non-standardized, with some practitioners providing detailed measurements of the deformity whereas others defer the interpretation of the deformity to the ordering surgeon. For radiologists, the standard of care is not clear, and this creates confusion in terms of how much interpretation is required. However, detailed radiologist reports sometimes conflict with the surgeon's interpretation, which can create confusion for patients who receive the reports, or in extreme cases can lead to insurance denials. Thus, the purpose of this study was to help establish a standard for interpretation of these films by surveying the ordering surgeons and documenting expert opinion about the amount and type of radiologist interpretation that is requested. METHODS: We designed a SurveyMonkey survey which aimed to look at standard practice for radiologist dictation of scoliosis radiographs. Twelve questions were sent to Lumbar Spine Research Society membership via email with a description of the study. One follow-up email was also sent to non-responders. RESULTS: The rate of completed surveys was 46 out of 185 Lumbar Spine Research Society members (25%). Thirty-seven respondents (80%) worked in academic institutions, 33 were orthopedists (71%), and 13 were neurosurgeons (28%). Fifty percent reported that radiologists' level of detail in dictations was inconsistent at their institution. Detailed numeric reporting was rare (6.5%). When the radiologist did provide numeric measurements, surgeons reported that they often differed from the surgeon's own measurements, with only 4% reporting that the measurements "rarely" differed from the surgeon's; 49% reported that the radiologist's measurements that differed from the surgeon's had led to insurance denials for their patients. The majority of respondents (70%) did not want the radiologist to provide detailed numeric measurements of the deformity, and 91% reported that the radiologist's measurements had no impact on their clinical decision making. CONCLUSIONS: Detailed deformity measurements are time consuming for the radiologist, and would seem to have low clinical utility for the responding surgeons in this survey, with significant potential for discrepancies in interpretation to lead to insurance denials. LEVEL OF EVIDENCE: IV.

The effectiveness of a free-standing lead-shield in reducing spine surgeon radiation exposure during intraoperative 3-dimensional imaging.

BACKGROUND: CONTEXT Intraoperative three-dimensional (3D) computed tomography (CT) imaging has become increasingly popular in spine surgery. Previous spine surgeon radiation exposure research has focused largely on procedures using fluoroscopy, however, few studies have been performed on the subject since the introduction of the 3D imaging systems. As a result, concerns have re-emerged over surgeon radiation exposure and the effectiveness of operating room (OR) protocols for decreasing workplace radiation. Current radiation safety guidelines require surgeons wear full body protective lead while any type of radiation is being administered during surgery. As a result, local institutions do not allow for the use of free-standing lead shields for sole radiation protection in the operating room. However, there is no data available to demonstrate whether the additional personal lead is required, or if in fact the lead shield alone is sufficient. PURPOSE: This study investigated the effectiveness of a free-standing lead shield in reducing spine surgeon radiation exposure in the operating room during intraoperative imaging. STUDY DESIGN/SETTING: A prospective clinical research study at a large, tertiary care center. PATIENT SAMPLE: Twenty-seven patients undergoing instrumented spinal procedures between June and August 2019. OUTCOME MEASURES: Fluoroscopy time, total fluoroscopy dose delivered, 3D dose delivered, total 3D spins, number of HD spins, number of standard spins, number of fluoroscopic images, number of spine levels operated on, patient size setting, shield distance from patient, radiation dose in front of shield, radiation dose behind shield. METHODS: Twenty-seven instrumented spinal procedures using the O-Arm Imaging System (Medtronic, Minneapolis, MN) were observed to determine radiation exposure to a spine surgeon standing behind a lead shield in the OR. Two thermoluminescent dosimeters were used to measure scatter radiation in front of and behind lead shields. Both fluoroscopy and intraoperative CT based radiation exposure was recorded. The dosimeter readings were compared to determine the degree of radiation attenuation by the lead shield. Regression analysis of the exposure values from behind the shield, shield distance from the patient, and radiation dose delivered by the imaging system was utilized to estimate the number of cases required to surpass annual exposure limits. Case numbers were calculated for the highest "worst case" and "average case" exposure values. The safe annual occupation exposure limit determined by the National Council on Radiation Protection is five roentgen equivalent man (rem) or 50,000 microsieverts (µSv). RESULTS: Average surgeon radiation exposure per case was 0.694 µSv (SD: 0.501, Range: 0.105-2.167) behind the lead shield compared to 14.577 µSv (SD: 9.864, Range: 2.185-44.492) in front of the lead shield. The average radiation dose reduction by the lead shield was 13.962 µSv (SD: 9.49, Range: 2.08-42.72) per case, which is equivalent to an average of 95.65% (SD: 1.71) radiation attenuation by lead shielding. If surgeons stand behind lead shields in the OR, the annual number of 3D image-guided spinal procedures required to surpass exposure limits is 15,479 and 67,060 based on "worst case" and "average case" analyses, respectively. CONCLUSIONS: Our study demonstrates standing behind intraoperative lead shields is very effective at decreasing radiation exposure to surgeons. Additionally, surgeon radiation doses behind lead shielding fall far below annual exposure limits. Surgeons should not need additional protective equipment when a lead shield is used.

Minimally Invasive Sacroiliac Joint Fusion: The Current Evidence.

BACKGROUND: Fusion of the sacroiliac (SI) joint as a treatment for low back pain remains controversial. The purpose of this manuscript is to review the current literature and clinical outcomes of SI joint fusion surgery. METHODS: We conducted a literature review and included studies with the term "sacroiliac joint fusion" that had at least 12 months of clinical follow-up, reported on minimally invasive techniques, and included patient-reported outcome measures. RESULTS: Two approach types (dorsal and lateral) and numerous different implant manufacturers were identified. Most studies included level 4 data, with a small number of level 2 prospective cohort studies and 2 prospective level 1 studies. Every reviewed study reported clinical benefit in terms of improved pain scores or improvement in validated disability measures. Complication rates were low. CONCLUSIONS: Minimally invasive SI joint fusion provides clinically significant improvement in pain scores and disability in most patients, across multiple studies and implant manufacturers. LEVEL OF EVIDENCE: 5. CLINICAL RELEVANCE: Emerging evidence in support of SI joint fusion indicates that clinicians should examine the SI joint and include SI joint pain in their differential diagnosis for low back pain patients.

The Deformity TLIF: Bilateral Facetectomy and Osteotomy Closure with a Hinged Table.

Background: Increasing emphasis has been placed on segmental lordosis correction, even in short segment constructs. However, the majority of reports on TLIF indicate that lordosis correction is modest at best. TLIF with bilateral facetecomy has been described with better lordosis correction, but is usually performed with the spine in extension throughout the case. This report presents a new technique for lordosis correction during TLIF with the use of bilateral facetectomy and osteotomy closure using a mechanically hinged operative table. Methods: A 78-year-old male presented with claudicatory back and leg pain due to foraminal stenosis and spondylolisthesis at L4-5 and L5-S1, and was operated on with bilateral facetectomies and TLIF while positioned on a motorized-hinged table, which started in flexion for the decompression and was brought into extension at the end of the case for osteotomy closure. Results: Segmental lordosis from L4-S1 increased from 15° pre-operatively to 42° postoperatively. Conclusions: A comparison of pre- and post-operative lateral radiographs showed 27° segmental lordosis correction, and intra-operative fluoroscopy showed correlation between extension of the table and segmental lordosis correction. Bilateral facetectomy and TLIF allows for segmental lordosis correction. Use of the hinged table allowed for ideal positioning during the decompression and controlled osteotomy closure with close correlation between table position and segmental alignment.Level of Evidence: V.