Sacropelvic fixation: techniques and complications

[Risk factors analysis of coronal imbalance after posterior long-level fixation and transforaminal lumbar interbody fusion for degenerative lumbar scoliosis]

OBJECTIVE

To explore the risk factors of coronal imbalance after posterior long-level fixation and fusion for degenerative lumbar scoliosis.

METHODS

Retrospectivly analyzed the clinical records of 41 patients with degenerative lumbar scoliosis who had received posterior long-level fixation and fusion with selective transforaminal lumbar interbody fusion (TLIF) accompanied by Ponte osteotomy between August 2011 and July 2016. Patients were divided into imbalance group (group A, 11 cases) and balance group (group B, 30 cases) according to state of coronal imbalance measured at last follow-up. The radiographic parameters at preoperation and last follow-up were measured, and the variance of preoperative and last follow-up parameters were calculated. The radiographic parameters included coronal Cobb angle, coronal balance distance (CBD), apical vertebral translation (AVT), apical vertebral rotation (AVR), Cobb angle of lumbar sacral curve (LSC), and L 5 tilt angle (L 5TA). Univariate analysis was performed for the factors including gender, age, preoperative T value of bone mineral density, number of instrumented vertebra, upper and lower instrumented vertebra, segments of TLIF, decompression, and Ponte osteotomy, as well as the continuous variables of preoperative imaging parameters with significant difference were converted into two-category variables, obtained the influence factors of postoperative coronal imbalance. Multivariate logistic regression analysis was performed to verify the risk factors from the preliminary screened influence factors and the variance of imaging parameters with significant difference between the two groups.

RESULTS

The follow-up time of groups A and B was (3.76±1.02) years and (3.56±1.03) years respectively, there was no significant difference between the two groups ( t=0.547, P=0.587). The coronal Cobb angle, AVT, LSC Cobb angle, and L 5TA in group A were significantly higher than those in group B before operation ( P<0.05), and all the imaging parameters in group A were significantly higher than those in group B at last follow-up ( P<0.05). There was no significant difference between the two groups in parameters including the variance of coronal Cobb angle, AVT, and LSC Cobb angle before and after operation ( P>0.05), and there were significant differences between the two groups in parameters including the variance of CBD, L 5TA, and AVR ( P<0.05). Univariate analysis showed that preoperative L 5TA was the influencing factor of postoperative coronal imbalance ( P<0.05). Multivariate logistic regression analysis showed that preoperative L 5TA≥15° was an independent risk factor of postoperative coronal imbalance, and variance of pre- and post-operative AVR was a protective factor.

CONCLUSION

Preoperative L 5TA≥15° is an independent risk factor for coronal imbalance in patients with degenerative lumbar scoliosis after posterior long-level fixation and fusion.

Anatomic Trajectory for Iliac Screw Placement in Pediatric Scoliosis and Spondylolisthesis: An Alternative to S2-Alar Iliac Portal

STUDY DESIGN

Single-center retrospective study.

OBJECTIVE

To analyze two-year postoperative outcomes following spinopelvic fixation in pediatric patients using the anatomic trajectory (AT) portal for iliac screws.

SUMMARY

Iliac fixation is crucial in situations requiring fusion to sacrum. Challenges include complex anatomy, pelvic deformation, severe deformity, and previous surgery. The PSIS portal requires significant dissection, rod connectors, and complex bends. The SAI portal requires navigating the screw across the SI joint to the ilium. The anatomic trajectory (AT), first reported in 2009, is between the PSIS and SAI portal, without prominence, connectors, or complex bends.

METHODS

Fifty-four patients aged ≤18 years requiring instrumentation to the Ilium with minimum follow-up of two years (mean 44 months) were clinically and radiographically evaluated. Changes in coronal curve magnitude and pelvic obliquity were assessed using paired t test for patients with cerebral palsy. Spondylolisthesis reduction was assessed in patients with moderate- to high-grade spondylolisthesis (Meyerding grade 3 and 4).

RESULTS

A total of 108 iliac screws were inserted using AT portal in 54 patients. Twenty-eight neuromuscular and syndromic patients had an initial mean coronal curve of 85° corrected to 23° at two years (p < .001) and a pelvic obliquity of 22° corrected to 4° (p < .001). Twenty patients with moderate- to high-grade spondylolisthesis treated with reduction and interbody fixation improved significantly with respect to their slip angles (7° ± 14.7° to -7.9° ± 6.1°, p = .003). In the neuromuscular group, two surgical site infections occurred, two had implant fractures, and 12 had asymptomatic iliac screw loosening, none requiring revision. In the spondylolisthesis group, there were no neurologic complications and one had prominent screw requiring removal. Of 108 iliac screws, 2 rod connectors were employed.

CONCLUSION

Iliac screw insertion using the AT portal is a safe and effective method of pelvic fixation in pediatric patients with satisfactory radiographic correction and minimal complications.

LEVEL OF EVIDENCE

Level 4.

SACROPELVIC FIXATION USING ILIAC SCREWS: EVALUATION OF TECHNIQUE AND COMPLICATIONS

ABSTRACT Sacropelvic fixation arose from the need to protect the sacral instrumentation in long constructions, due to failures in the implant-bone interface and the treatment of diseases in which there is no possibilities of sacral fixation such as infections and tumors. Due to anatomic difficulties and the complex spinopelvic biomechanics several techniques were developed. The fixation with iliac screws has become according to multiple studies, a well-established technique that minimizes frequent complications such as pseudoarthrosis and implant failure. However, it has disadvantages such as iliac wing fracture and skin lesions due to the protrusion of materials. The present study aims to comprehensively review the literature on the technique taking into account relevant aspects to its better knowledge and application. Level of evidence III; Therapeutic Study.

Iliac screw versus S2 alar-iliac screw fixation in adults: a meta-analysis

OBJECTIVEIn a meta-analysis, the authors sought to compare outcomes after iliac screw (IS) versus S2 alar-iliac (S2AI) screw fixation in adult patients.METHODSA PubMed/MEDLINE database search was performed for studies comparing IS and S2AI screw fixation techniques in adults. Levels of evidence were assigned based on the North American Spine Society guidelines. Three outcomes were examined: 1) revision surgery rate secondary to mechanical failure or wound complications, 2) surgical site infection rate, and 3) screw prominence/pain. Data were pooled and outcomes compared between techniques. Absolute risk reductions (ARRs) were also calculated for outcome measures.RESULTSFive retrospective cohort studies (all level III evidence) were included in our analysis. A total of 323 adult patients were included-147 in the IS group (45.5%) and 176 in the S2AI group (54.5%). Overall, revision surgery due to mechanical failure or wound complications was needed in 66 of 323 patients (revision surgery rate 20.4%)-27.9% in the IS group and 14.2% in the S2AI group (13.7% ARR; p < 0.001). Four studies reported wound infections among 278 total patients, with an infection rate of 12.6% (35/278)-25.4% in the IS group and 2.6% in the S2AI group (22.8% ARR; p < 0.001). Three studies examined development of screw prominence/pain; combined, these studies reported screw prominence/pain in 21 of 215 cases (9.8%)-18.1% in the IS group and 1.8% in the S2AI group (16.3% ARR; p < 0.001).CONCLUSIONSS2AI screw fixation in adults has a significantly lower mechanical failure and complication rate than IS fixation based on the current best available evidence.

Three Methods of Pelvic Fixation for Scoliosis in Children With Cerebral Palsy: Differences at 5-year Follow-Up

STUDY DESIGN

A retrospective review.

OBJECTIVE

The aim of this study was to assess correction of pelvic obliquity in children with cerebral palsy (CP) scoliosis postoperatively and 5 years after posterior spinal fusion with pelvic fixation using unit rods, sacral-alar-iliac (SAI) screws, or iliac screws.

SUMMARY OF BACKGROUND DATA

There are multiple options for pelvic fixation in children with scoliosis secondary to CP. The long-term differences in outcomes between these fixation methods are still unclear.

METHODS

A multicenter review identified records of 70 children with CP who underwent posterior spinal fusion for scoliosis using unit rods (n = 9), SAI screws (n = 19), or iliac screws (n = 42). Patients younger than 18 years with 5-year follow-up were included. Pelvic obliquity and major coronal curve measurements were compared using preoperative, (first erect) postoperative, and 5-year follow-up radiographs. Implant-related complications were noted. Alpha = 0.05.

RESULTS

For all groups, there was a significant difference between preoperative and postoperative pelvic obliquity that was maintained at 5 years. At 5-year follow-up, pelvic obliquity was significantly higher in the IS group (12°) compared with the unit rod group (4°, P = 0.001) and SAI screw group (6°) (P = 0.006). Implant-related complications were as follows: unit rod group, one patient (reoperation); SAI screw group, none; iliac screw group, six patients, including three cases of loss of connection between the rod and the iliac screw, two prominent screws, and one loose screw.

CONCLUSION

Correction of pelvic obliquity for children with CP-related scoliosis was achieved postoperatively using unit rods, SAI screws, and iliac screws. Implant-related complications and reoperations were most common in the iliac screw group. At 5-year follow-up, the iliac screw group had loss of major curve correction and less correction of pelvic obliquity than the unit rod and SAI screw groups.

LEVEL OF EVIDENCE

3.

TOMOGRAPHIC STUDY OF THE S2-ALAR-ILIAC SCREW TECHNIQUE IN BRAZILIAN WOMEN

ABSTRACT Objective: Lumbosacral fixation presents problems in its arthrodesis, mainly due to pseudoarthrosis. Iliac screws minimize this problem, however, they show problems in the operative wound. The S2-Alar-iliac (S2AI) screw presents a lower rate of these complications. The anatomical differences between the populations and the sexes analyzed in the literature justify the study of the S2AI screw technique in Brazilian women. Methods: A total of 14 adult female CT scans were analyzed by 4 evaluators. Results: The mean bone length was 131.8 mm, the largest bone diameter was 22.6 mm, and the smallest bone diameter was 22.6 mm. Conclusions: The data presented are compatible with the literature and may assist spine surgeons in choosing the best implant and surgical technique. Level of Evidence I; Diagnostic Studies — Investigating a Diagnostic Test (anatomical investigation).

EVALUATION OF THE RESULTS OF PELVIC FIXATION IN LONG LUMBOSACRAL INSTRUMENTATIONS IN ELDERLY PATIENTS

ABSTRACT Objective: Evaluate the initial results and the possible complications of the combination of pelvic fixation using iliac screws in long instrumentations of the lumbar spine in elderly patients. Methods: An analysis of 38 patients who underwent lumbar spine arthrodesis instrumentation with more than 3 levels, in which we included level L5-S1 and extended the fixation to the iliac crest. Radiological assessment of instrumentation through X-ray of the lumbar spine and pelvis, and computed tomography, to investigate the presence of radiological fusion. Clinical evaluation through a questionnaire of buttock pain including the visual analogue pain score (VAS). Complications related to pelvic instrumentation were investigated. Results: All patients had radiological fusion in the lumbosacral transition. A halo was found around the iliac screw on imaging studies in 31% of patients, but without related symptoms. The questionnaire of buttock pain found that 15% of patients had some low intensity buttock pain (VAS 1-2) and no need to or interest in removing the screws. There was infection at the surgical site in 2% of cases, hematoma in the buttocks in 5%, and vertebral body fracture in the cranial level instrumented in 7% of cases. Conclusions: Pelvic fixation through the iliac screws proved to be effective in protecting the S1 screws in long instrumentations including the L5-S1 level in elderly patients, allowing the radiological bone fusion. The overall results for pain were satisfactory, based on a questionnaire of buttock pain. There are no signs of overload or degeneration of the sacroiliac joints in the early years after surgery. Level of Evidence IV; Case series - therapeutic study.

The comparison of the results after spinal fusion with or without iliac screw insertion in the treatment of neuromuscular scoliosis

Introduction

Neuromuscular scoliosis leads to a wide range of spinal disorders which disturb the musculoskeletal system. The aim of this study is to compare the clinical and radiological results of posterior spinal fusion with and without extending the instrumentation to iliac bones in treatment of neuromuscular scoliosis.

Methods

Medical records and radiographies of 36 patients with neuromuscular scoliosis who underwent posterior instrumentation between 2011 and 2015 were reviewed. Age and body mass index at time of surgery, underlying diagnosis, gender, postoperative infection rates, perioperative and postoperative blood transfusion, duration of surgery, complication rates were identified for each patient retrospectively. SF-36 physical questionnaire was applied to all patients. Surgery was performed in each patient and included posterior spinal fusion with pedicle screws from the proximal thoracic spine (T2 or T3) to S1 (Group A) or extension of distal instrumentation to pelvis by bilateral iliac screws (Group B).

Results

A total of 23 patients in group A were compared with 13 patients in group B. Median age was 14 (9–38) years for group A and 16 (12–25) years for group B. Median follow-up period was 20 (12–66) months. Preoperative median Cobb angles were 66^° and 60^° and postoperative Cobb values were 33^° and 31^° in group A and B respectively. Median Cobb angle reduction was 40^° and 34^° for group A and B. We are able to see in this study that the usage of illiac screws do not increase implant failure and help achieve better functional results.

Conclusion

This study shows that the extention of instrumentation to the pelvis with illiac screws can be beneficial in terms of functional and complicational incidences.

Level of evidence: Level III, therapeutic study.

Radiographic and Clinical Outcomes From the Use of S2 Alar Screws in Surgery for Adult Spinal Deformity

STUDY DESIGN

Retrospective.

OBJECTIVES

To evaluate the efficacy of S2 alar screws in surgery for correction of adult spinal deformity (ASD).

METHODS

We retrospectively reviewed the cases of 23 patients (mean follow-up: 18.5 months, minimum 12 months) who underwent corrective surgery for ASD using S2 alar screws as anchors for instrumentation of lower vertebrae. The background of the patients and their spinopelvic parameters (pelvic incidence [PI], pelvic tilt [PT], lumbar lordosis [LL], thoracic kyphosis [TK], sagittal vertical axis [SVA], and PI-LL) were evaluated.

RESULTS

LL was improved from 9.7 ± 20.5° and SVA from 141.0 ± 64.0 mm before surgery to 39.0 ± 9.6° and 51.7 ± 40.8 mm immediately after surgery, respectively, and 38.2 ± 12.7° and 70.5 ± 59.2 mm at final follow-up. In 13 patients without sufficient correction (postoperative PI-LL ≥10°), bone mineral density and postoperative LL were significantly less, and PI, PI-LL, and PT were significantly greater than in patients with postoperative PI-LL <10°, suggesting that these are risk factors for undercorrection. In 5 patients, SVA increased more than 40 mm during follow-up. Postoperative LL was significantly less (31.4° vs 41.0°) and postoperative PI-LL was significantly greater (21.6° vs 9.3°) in these patients, suggesting a PI-LL mismatch induces postoperative progression of global malalignment.

CONCLUSIONS

Use of S2 alar screws as anchors for instrumentation in ASD surgery should be restricted. Their use might be an option for patients with low PI, and without severe osteoporosis, in whom efficient surgical correction can be obtained.

Biomechanics of L5/S1 in Long Thoracolumbosacral Constructs: A Cadaveric Study

STUDY DESIGN

In vitro cadaveric biomechanical study.

OBJECTIVES

Despite numerous techniques employed to establish solid lumbosacral fixation, there are little biomechanical data correlating fixation methods at L5/S1 to thoracolumbosacral (TLS) construct length. We aimed to determine the optimal construct with the hypothesis that under physiological loads, lumbosacral constructs can be stabilized by L5/S1 anterior lumbar interbody fusion (ALIF) alone, without iliac screw fixation (ISF), and that TLS constructs would require ISF, with or without ALIF.

METHODS

By using a robot capable of motion in 6 axes, force-moment sensor, motion-tracking camera system and software, we simulated the spinal loading effects in flexion-extension, axial rotation, and lateral bending, and compared torques in different construct groups of T4-S1, T10-S1, and L2-S1. By conducting multidirectional flexibility testing we assessed the effects of constructs of various lengths on the L5/S1 segment.

RESULTS

L2-S1 constructs may be equivalently stabilized by L5/S1 ALIF alone without ISF. Longer TLS constructs exerted increasing motion at L5/S1, exhibiting trends in favor of ISF when extending to T10 and statistically improved fixation when extending to T4. Lastly, TLS constructs with ISF exhibited a statistically significant reduction in L5-S1 range of motion from the addition of ALIF when extending to T4-pelvis but not T10-pelvis.

CONCLUSIONS

We found that ALIF alone may sufficiently support the L2-S1 construct, reducing L5/S1 range of motion and transmitting loads instead to the sacropelvis. Furthermore, ALIF was found to add significant stability to the T4-pelvis construct when added to ISF. This difference was not significant for the T10-pelvis construct.

Effect of the screw type (S2-alar-iliac and iliac), screw length, and screw head angle on the risk of screw and adjacent bone failures after a spinopelvic fixation technique: A finite element analysis

PURPOSE

Spinopelvic fixations involving the S2-alar-iliac (S2AI) and iliac screws are commonly used in various spinal fusion surgeries. This study aimed to compare the biomechanical characteristics, specifically the risk of screw and adjacent bone failures of S2AI screw fixation with those of iliac screw fixation using a finite element analysis (FEA).

METHODS

A three-dimensional finite element (FE) model of a healthy spinopelvis was generated. The pedicle screws were placed on the L3-S1 with three different lengths of the S2AI and iliac screws (60 mm, 75 mm, and 90 mm). In particular, two types of the S2AI screw, 15°- and 30°-angled polyaxial screw, were adopted. Physiological loads, such as a combination of compression, torsion, and flexion/extension loads, were applied to the spinopelvic FE model, and the stress distribution as well as the maximum von Mises equivalent stress values were calculated.

RESULTS

For the iliac screw, the highest stress on the screw was observed with the 75-mm screw, rather than the 60-mm screw. The bones around the iliac screw indicated that the maximum equivalent stress decreased as the screw length increased. For the S2AI screw, the lowest stress was observed in the 90-mm screw length with a 30° head angle. The bones around the S2AI screw indicated that the lowest stress was observed in the 90-mm screw length and a 15° head angle.

CONCLUSIONS

It was found that the S2AI screw, rather than the iliac screw, reduced the risk of implant failure for the spinopelvic fixation technique, and the 90-mm screw length with a 15° head angle for the S2AI screw could be biomechanically advantageous.

The posterior superior iliac spine and sacral laminar slope: key anatomical landmarks for freehand S2-alar-iliac screw placement

OBJECTIVE

The S2-alar-iliac (S2AI) screw is an increasingly popular method for spinopelvic fixation. The technique of freehand S2AI screw placement has been recently described. The purpose of this study was to demonstrate, through a CT imaging study of patients with spinal deformity, that screw trajectories based on the posterior superior iliac spine (PSIS) and sacral laminar slope result in reliable freehand S2AI trajectories that traverse safely above the sciatic notch.

METHODS

Fifty consecutive patients (age ≥ 18 years) who underwent primary spinal deformity surgery were included in the study. Simulated S2AI screw trajectories were analyzed with 3D visualization software. The cephalocaudal coordinate for the starting point was 15 mm cephalad to the PSIS. The mediolateral coordinate for the starting point was in line with the lateral border of the dorsal foramina. The cephalocaudal screw trajectory was perpendicular to the sacral laminar slope. Screw trajectories, lengths, and distance above the sciatic notch were measured.

RESULTS

The mean sagittal screw angle (cephalocaudal angulation) was 44.0° ± 8.4° and the mean transverse angle (mediolateral angulation) was 37.3° ± 4.3°. The mean starting point was 5.9 ± 5.8 mm distal to the caudal border of the S1 foramen. The mean screw length was 99.9 ± 18.6 mm. Screw trajectories were on average 8.5 ± 4.3 mm above the sciatic notch. A total of 97 of 100 screws were placed above the sciatic notch. In patients with transitional lumbosacral anatomy, the starting point on the lumbarized/sacralized side was 3.4 mm higher than on the contralateral unaffected side.

CONCLUSIONS

The PSIS and sacral laminar slope are two important anatomical landmarks for freehand S2AI screw placement.

Effect of Different Types of Upper Instrumented Vertebrae Instruments on Proximal Junctional Kyphosis Following Adult Spinal Deformity Surgery: Pedicle Screw versus Transverse Process Hook

Study Design

Retrospective comparative study.

Purpose

To compare the incidence of proximal junctional kyphosis (PJK) between transverse process hooks (TPHs) and pedicle screws (PSs) at the upper instrumented vertebrae (UIV) following adult spinal deformity (ASD) surgery.

Overview of Literature

The choice of UIV implant type may be important for avoiding PJK; however, few comparative clinical studies have evaluated the incidence of PJK according to the type of UIV implant used in ASD surgery.

Methods

We retrospectively reviewed 39 consecutive patients with ASD (mean age, 67 years; mean follow-up period, 41 months) who underwent corrective surgery between 2009 and 2013. TPH was used in 17 patients and PS in 22 patients. PJK was defined as the presence of a UIV or UIV±1 fracture, or a change in the proximal junctional angle (PJA) of >20°. Data of patients with TPH and PS were compared.

Results

The TPH group had a PJK incidence of 17.6% compared with 27.3% in the PS group (p =0.47). In the TPH group, PJK was a result of UIV fracture in one patient, UIV−1 fracture in one patient, and ligamentous failure in one patient. In the PS group, six patients developed PJK because of UIV fracture. No differences in radiographic parameters were found between the two groups. After analyzing the PJA data in the patients with PJK, the changes in PJA were significantly higher in the PS group than in the TPH group (19.0°/5.0°, p =0.04).

Conclusions

Our results show that using TPH as a UIV implant may not prevent PJK; however, using TPH as the UIV anchor may prevent vertebral collapse if cases of UIV fracture. The increased risk of UIV fracture collapse in the PS group may be a result of a higher mechanical load on UIV when using PS.

Impact of Iliac Instrumentation on the Quality of Life of Patients With Adult Spine Deformity

STUDY DESIGN

Retrospective comparative analysis of data collected prospectively in an adult spine deformity (ASD) multicenter database.

OBJECTIVE

To evaluate the impact of the iliac screws on the quality of life of ASD patients compared with those instrumented above the pelvis (L5/S1/S2).

SUMMARY OF BACKGROUND DATA

The impact on patient's daily activities and functions, of immobilizing the sacroiliac joint with iliac screws for the treatment of ASD is still underexplored.

METHODS

Inclusion criteria were ASD patients with a long arthrodesis of at least eight levels and whose lowest instrumented vertebrae (LIV) were L5 or below. We analyzed the following preoperative and 2 years' follow-up variables: age, Cobb angle, coronal and sagittal alignment, number of instrumented levels, Oswestry Disability Index (ODI), Core Outcome Measures Index (COMI), Scoliosis Research Society-22 (SRS-22), and Short Form 36 (SF-36) questionnaires. Statistical analysis was performed with Mann-Whitney U test, and Wilcoxon test.

RESULTS

A total of 129 patients were included, and separated into two groups: "Iliac Yes," with the LIV at the Ilium (N = 104), and "iliac No," with the LIV at L5/S1/S2 (N = 25). Patients instrumented with Iliac screws were older (x = 66 vs. 56 yr, P = 0.008), and had lower Cobb magnitude (x = 31° vs. 45°, P = 0.019). No statistically significant differences were found in the health related quality of life (HRQOL) questionnaires prior to surgery or at 2-years' follow up. The "Iliac Yes" group significantly improved all radiographic and HRQOL scores parameters 2 years after surgery (P < 0.005). While the "Iliac No" group failed to significantly improve (coronal balance, sagittal vertical axis, SF-36 Physical functioning, SF-36 General health, and COMI) (P > 0.05) CONCLUSION.: ASD patients instrumented with iliac screws significantly improved all their HRQOL questionnaires 2 years after surgery. The 2 years' postoperative HRQOL scores were similar in both groups, regardless of the sacroiliac joint immobilization. Therefore, with the currently available tools, we cannot state that iliac instrumentation has a negative influence on patient's quality of life.

LEVEL OF EVIDENCE

4.

The use of three-column osteotomy in the treatment of rigid deformities of the adult spine

Objective

To analyze and characterize data about clinical outcome and complication rates in three-column osteotomies (3 CO) for treatment of rigid adult spine deformity (ASD).

Methods

Baseline and postoperative clinical outcomes, considering the Oswestry Disability Index (ODI) and Scoliosis Research Society-22 (SRS-22) questionnaires, radiographic parameters, and demographic data of patients who underwent 3 CO procedure for fixed ASD treatment were collected. Surgical characteristics and reports of perioperative complications were recorded, as well as those that occurred at a minimum follow-up of 12 months.

Results

Ten patients underwent 3 CO and had a minimum follow-up of 12 months (mean 24 months). The patients showed significantly improved health-related quality of life scores (ODI, SRS-22 total, function/activity, pain, and appearance). They also presented a significant improvement in all radiographic parameters considered in the study. Taking into account the surgical procedure, the operative time was significantly higher in patients with staged procedure than in patients with single-stage surgery (p = 0.003), with similar estimated blood loss and complication incidence. There were ten complications in six patients (60%), with a mean of 1.0 complication per patient.

Conclusions

Despite of the high complication rates, 3 CO was an effective technique, considering clinical and radiographic outcomes, to treat complex cases of rigid ASD in a sample of patients operated in a Brazilian spine center, with a minimum follow-up of 12 months.

Spinopelvic Fixation

Fixation at the lumbosacral junction continues to be a challenge for spine surgeons despite advances in spinal instrumentation techniques. The poor bone quality of the sacrum, the complex regional anatomy, and the tremendous biomechanical forces at the lumbosacral junction contribute to the high rates of instrumentation-related complications. Although many spinopelvic fixation techniques have been reported, only a few are still widely used because of the high complication rates associated with previous techniques. Spinopelvic fixation has numerous indications. Long-segment lumbar and thoracolumbar fusions to the sacrum are the most common scenarios in which instrumentation is extended to the pelvis. Surgeons performing complex spinal reconstruction should be familiar with the available techniques, including their potential risks and complications.

S-1 alar/iliac screw technique for spinopelvic fixation

Spinopelvic fixation provides an important anchor for long fusions in spinal deformity surgery, and it is also used in the treatment of other spine pathologies. Iliac screws are known to sometimes require reoperation due to pain resulting from hardware prominence and skin injury. S-2 alar/iliac (S2AI) screws do not often require removal, but they may provide inadequate fixation in select cases. In this paper the authors describe a technique for S-1 alar/iliac screws that may be used independently or as a supplement to S2AI screws. A preliminary biomechanical analysis and 2 clinical case examples are also provided.

Stand-alone anterior interbody fusion for substitution of iliac fixation in long spinal fixation constructs

INTRODUCTION

The use of distal sacral anchorage solely, in long spinal fusions, may lead to substantial complications. Extending the fixation down to the ilium and the addition of anterior column support are both used to facilitate construct stability and improve fusion rates. In the current study, we aimed to determine whether supplementation of long thoracolumbar fixation constructs with stand-alone anterior interbody fusion (ALIF) cage with embedded screws can eliminate the biomechanical need for iliac screws fixation biomechanically.

METHODS

Seven lumbopelvic human cadavers (L1-full pelvis) were used. All specimens were tested with the following fixation constructs: bilateral L1-S1, bilateral L1-S1 with unilateral iliac screw, and bilateral L1-S1 with bilateral iliac screw. The three constructs were tested with and without the addition of stand-alone ALIF cage. We evaluated the multidirectional rigidity and the axial S1 screw strain.

RESULTS

The addition of an ALIF cage solely did not affect rigidity and resulted in mixed S1 screw strain results. One iliac screw was superior to ALIF in rigidity and inferior in S1 screws strain. Bilateral iliac fixation produced similar rigidity and lower S1 screws strain than unilateral iliac fixation. When ALIF was combined with bilateral iliac screws, it resulted in equal rigidity and lower S1 screws strain.

CONCLUSION

Our results do not support stand-alone ALIF cage as a substitute for iliac fixation in in long posterior lumbosacral fusion. They do support the use of stand-alone ALIF for the supplementation of bilateral iliac fixation in long lumbosacral fusions.

Proper detailed parameters for S1 sacral alar iliac screw placement in the Chinese population, a 3D imaging study

Background

S1-AI technique may be used as a salvage technique in pelvic fixation of complex spinal deformity surgery. However, the proper detailed parameters in the Chinese population has not been analyzed before to instruct S1-AI screws placement and to ensure the safety of clinical application while the trajectory in pelvic changes significantly at each angle.

Results

The ideal S1AI screw trajectory could be obtained in 28 of 30 female patient images (93.3%) and in all of the male patient images (100%). The screws that have already been used clinically in S2AI pathways can be applied in S1AI fixations.

Conclusion

It is feasible to place S1AI screws in 93.3% of female Chinese adult patients and in all male Chinese patients. Preoperative CT reconstruction should be performed to evaluate proper trajectory parameters and to avoid anterior violation.

Subcrestal Iliac-Screw: A Technical Note Describing a Free Hand, In-line, Low Profile Iliac Screw Insertion Technique to Avoid Side-connector Use and Reduce Implant Complications

STUDY DESIGN

Case-series.

OBJECTIVE

To report our modified iliac-screw insertion technique and its clinical outcomes.

SUMMARY OF BACKGROUND DATA

Iliac-screws are one of the preferred methods for modern spinopelvic-fixation. However, the technique is not without complications, predominantly because of iliac-screw head prominence, leading to pain and revisions. Conventional iliac-screw entry point is sited superficially at the posterior-superior-iliac-spine (PSIS) contributing to screw-head prominence. We propose a more low-profile, subcrestal entry point that is more medial and inferior to the PSIS at the medial wall of the iliac crest, lying underneath the crest but above the sacroiliac joint. This position keeps the screw-head low profile and in-line with proximal instrumentation to ease rod engagement.

METHODS

Ten consecutive patients who underwent spinal deformity correction surgery using the modified iliac-screw entry point fixations were enrolled. Clinical, radiological, and surgical parameters were reviewed.

RESULTS

Five males and five females with average age of 66 years and average follow up of 29 months were reviewed. Mean preoperative Cobb angle and C7-SVA were 32.1° and 10.3 cm, respectively. Surgical indication was progressive deformity and neurogenic claudication in eight cases and fracture in two cases. Twenty noncannulated, polyaxial iliac-screws with median dimension of 7.5 x 75 mm were inserted free hand. Bilateral S1 screws were used in all except two cases. Only five out of 16 iliac-screws with concomitant S1 screws needed side-connectors. At the last follow up only one iliac-screw head was felt to be prominent but without pain in a Parkinson's patient. None of the 10 patients had cases of revision, breakages, or sacroiliac pain.

CONCLUSION

Subcrestal iliac-screw insertion is feasible, safe, and has the potential to reduce screw-head complications and avoid the use of side-connectors, lowering construct complexity and cost. The technique has the advantage of both the low-profile S2 alar iliac screw and the ease of free-hand insertion of the traditional iliac-screw.

LEVEL OF EVIDENCE

4.

S2 Alar Iliac Fixation in Long Segment Constructs, a Two- to Five-Year Follow-up

STUDY DESIGN

Retrospective review of patients having undergone S2 alar-iliac (S2AI) fixation for long fusions with a minimum two-year follow-up.

OBJECTIVES

To report on fusion rates, complications, technique-specific complications of patients having undergone S2AI fixation.

SUMMARY OF BACKGROUND DATA

Sacropelvic fixation continues to be a challenge when performing long fusions to the pelvis. S2AI screws have been found to provide solid biomechanical fixation and have been found to have good clinical results in short-term follow-up for pediatric and adult patients.

METHODS

Cases were retrospectively reviewed in patients who had placement of S2AI screws for long fusions with at least a two-year follow-up. Demographic data, complications, and reoperations were reviewed. Complications were broken into minor and major categories similar to previous series on pelvic fixation.

RESULTS

There were 86 cases identified. Minor and major complications occurred in 29% and 24% of patients, respectively, with the majority of minor complications being intraoperative dural tears. Revision surgery for all causes was performed in 23% of the cohort. Fusion rate at L5-S1 for patients without preoperative pseudarthrosis was 95.3%. Preoperative L5-S1 pseudoarthrosis was identified in 20 patients, 17 (95%) of these went onto fusion after one surgery. There was evidence of S2AI screw lucency in 10.4% of cases. However, the majority of these were asymptomatic.

CONCLUSIONS

Sacropelvic fixation using the S2AI technique provides safe, durable fixation with low rates of technique-specific complications and limited need for hardware removal. Complication rates in this series were similar to other series on long fusions to the pelvis. Additionally, fusion rates were high at L5-S1 for both patients with and without preoperative L5-S1 pseudarthrosis. It appears that the S2AI technique is a powerful option for patients with previous L5-S1 pseudarthrosis.

LEVEL OF EVIDENCE

Level III.

Freehand S2 Alar-Iliac Screw Placement Using K-Wire and Cannulated Screw : Technical Case Series

Objective

Among the various sacropelvic fixation methods, S2 alar-iliac (S2AI) screw fixation has several advantages compared to conventional iliac wing screw. However, the placement of S2AI screw still remains a challenge. The purpose of this study was to describe a novel technique of free hand S2AI screw insertion using a K-wire and cannulated screw, and to evaluate the accuracy of the technique.

Methods

S2AI screw was inserted by free hand technique in sixteen consecutive patients without any fluoroscopic guidance. The gearshift was advanced to make a pilot hole passing through the sacroiliac joint and directing the anterior inferior iliac spine. A K-wire was placed through the pilot hole. After introducing a cannulated tapper along with the K-wire, a cannulated S2AI screw was installed over the K-wire.

Results

Thirty-three S2AI screws were placed in sixteen consecutive patients. Thirty-two screws were cannulated screws, and one screw was a conventional non-cannulated screw. Thirty out of 32 (93.8%) cannulated screws were accurately positioned, whereas two cannulated screws and one non-cannulated screw violated lateral cortex of the ilium.

Conclusion

The technique using K-wire and cannulated screw can provide accurate placement of free hand S2AI screw.

Obstructed spinopelvic fixation in the setting of a triangular titanium sacroiliac fusion implant: a case description

Achieving lumbosacral fusion through spinopelvic fixation is an important and challenging aspect of spinal deformity surgery. Numerous instrumentation techniques are available, with iliac screws and S2-alar-iliac (SRAI) screws being most commonly used today. However, the increasing popularity of minimally invasive sacroiliac (SI) fusion as a common procedure performed for SI joint pain presents a distinct challenge in complex adult deformity cases requiring iliac screw fixation. We report a case of a 71-year-old female with a longstanding history of spinal deformity status-post T11-L5 fusion and a subsequent right-sided SI joint fusion who presented with sagittal imbalance. The SI joint fusion implant obstructed the pathway for spinopelvic fixation. Spinopelvic fixation was achieved by burring a pathway through the SI joint implant. The increasing popularity of minimally invasive SI fusion as a common procedure performed for SI joint pain presents a distinct challenge in complex adult deformity cases requiring iliac screw fixation. This is the first report in the literature describing a technique for spinopelvic fixation in the setting of screw obstruction due to an instrumented SI joint.

Usefulness of Sacral Sublaminar Wire for Low Transverse Sacral Fractures: Two Cases' Report

Low transverse sacral fractures are rare, with only two published reports regarding their surgery. The complication associated with surgery for sacral fractures is the prominence of implants. In addition, screw fixation below S3 is impractical. We performed posterior sacral fixation using S2 alar iliac (S2AI) screws and sacral sublaminar wires for low transverse sacral fractures. Case 1 was 65-year-old male with an S2-3 transverse sacral fracture. We performed laminectomy (S2-3) and passed ultrahigh molecular weight polyethylene (UHMWPE) cables from laminectomy area to the third posterior sacral foramina. We inserted S2AI screws and connected rods. We also tightened the UHMWPE cables. The implants did not protrude into skin. One year after surgery, the sacral fracture healed without any displacement. Case 2 was a 42-year-old female with an S2 transverse sacral fracture. We performed laminectomy (S1-3) and passed UHMWPE cables from laminectomy area to the third and fourth posterior sacral foramina. We inserted S1 pedicular screws and S2AI screws and connected rods. We also tightened UHMWPE cables. The implants did not protrude into skin. One year after surgery, the sacral fracture healed without any displacement. We consider sacral sublaminar wires to be useful bone anchors in lower sacrum.

Comparison Between S2-Alar-Iliac Screw Fixation and Iliac Screw Fixation in Adult Deformity Surgery: Reoperation Rates and Spinopelvic Parameters

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The S2-alar-iliac (S2AI) technique has been described as an alternative method for pelvic fixation in place of iliac screws (ISs) in spinal deformity surgery. The objective of this study was to analyze the impact of S2AI screws on radiographical outcomes, including spinopelvic parameters.

METHODS

A retrospective review of 17 patients receiving ISs and 46 patients receiving S2AI screws for correction of adult spinal deformity between 2010 and 2015 with minimum 1-year follow-up was conducted. Patient data on postoperative complications, including reoperation rates and proximal junctional kyphosis (PJK), and radiographical parameters was collected and statistically analyzed.

RESULTS

With mean follow-up of 21.1 months, the overall reoperation rate was significantly lower in the S2AI group than in the IS group (21.7% vs 58.8%, P = .01), but the incidence of PJK was similar (32.6% vs 35.3%, P > .99). Moreover, the time to reoperation in the IS group was significantly shorter than in the S2AI group (P = .001), and the S2AI group trended toward a longer time to reoperation due to PJK (P = .08). There was a significantly higher change in pelvic incidence (PI) in the S2AI group (-6.0°) compared with the IS group (P = .001).

CONCLUSIONS

Compared with the IS technique, the S2AI technique demonstrated a lower rate of overall reoperation, a similar rate of PJK, longer time to reoperation, and possible reduction in PI. Future studies may be warranted to clarify the mechanism of these results and how they can be translated into improved patient care.

Adult spinal deformity treated with minimally invasive surgery. Description of surgical technique, radiological results and literature review

The prevalence of adult spinal deformity has been increasing exponentially over time. Surgery has been credited with good radiological and clinical results. The incidence of complications is high. MIS techniques provide good results with fewer complications. This is a retrospective study of 25 patients with an adult spinal deformity treated by MIS surgery, with a minimum follow-up of 6 months. Radiological improvement was SVA from 5 to 2cm, coronal Cobb angle from 31° to 6°, and lumbar lordosis from 18° to 38°. All of these parameters remained stable over time. We also present the complications that appeared in 4 patients (16%). Only one patient needed reoperation. We describe the technique used and review the references on the subject. We conclude that the MIS technique for treating adult spinal deformity has comparable results to those of the conventional techniques but with fewer complications.

Prevalence and Risk Factors of Iliac Screw Loosening After Adult Spinal Deformity Surgery

STUDY DESIGN

A retrospective study.

OBJECTIVE

We investigated the prevalence of iliac screw loosening and determined risk factors after adult spinal deformity surgery.

SUMMARY OF BACKGROUND DATA

Lumbosacral fixation is crucial to maintain optimal sagittal alignment. Iliac screws are commonly placed to provide protection for sacral pedicle screws. Radiolucent areas around the screws indicate fixation loss and pseudarthrosis.

METHODS

Seventy-two patients with adult spinal deformity (13 men, 59 women; mean age, 69.0 yr) who underwent spinal deformity surgeries using bilateral iliac screws with at least 2 years follow-up were studied. Iliac and S1 screw loosening were assessed by postoperative radiograph. The period of loosening appearance and the relations between loosening and the following items were investigated: (1) upper instrumented vertebra, (2) L5/S interbody fusion, (3) iliac screw placement, (4) spinopelvic parameters (T1 pelvic angle, sagittal vertical axis, pelvic tilt, pelvic incidence-lumbar lordosis [LL]). Oswestry Disability Index scores were obtained preoperatively and 2 years postoperatively.

RESULTS

Iliac and S1 screw loosening was found in 20 (27.8%) and 7 patients (9.7%), respectively. Iliac screw loosening appeared at 5.2 months (range, 3-12) on average. Compared with nonloosening, loosening had significantly higher upper thoracic fusion rates (above T6), lower L5/S interbody fusion rate, higher misplacement rate, and higher insufficient correction rate (PI-LL >10°). Oswestry Disability Index significantly improved in nonloosening, whereas no significant difference was observed in loosening. Multiple regression analysis showed that misplacement (odds ratio = 10.8) and insufficient correction (odds ratio = 7.5) affected loosening.

CONCLUSION

Iliac screw loosening indicated instability of the lumbosacral junction, resulting in sagittal malalignment and poor outcomes. Accurate screw insertion and restoration of optimal LL were necessary to prevent complications.

LEVEL OF EVIDENCE

4.

Analysis of Risk Factors for Major Complications Following Elective Posterior Lumbar Fusion

STUDY DESIGN

Retrospective study of prospectively collected data.

OBJECTIVE

To identify risk factors for the development of any major complication after elective posterior lumbar fusion (PLF).

SUMMARY OF BACKGROUND DATA

PLF is one of the most performed fusion techniques with utilization rates increasing by 356% between 1993 and 2001. Surgical and anesthetic advances have made the option of surgery more accessible for elderly patients with a larger comorbidity burden. Identifying risk factors for the development of major complications after elective PLF is important for patient risk stratification and patient safety efforts.

METHODS

The 2011 to 2014 American College of Surgeon's National Surgical Quality Improvement Program database was queried using Current Procedural Terminology codes 22612, 22630, and 22633. Patients were divided into two cohorts based on the development of any major complication. Bivariate and multivariate logistic regression analyses were employed to identify predictors for the development of ≥ 1, ≥ 2, and ≥ 3 major complications.

RESULTS

A total of 7761 patients met the inclusion criteria for the study of which, 2055 (26.5%) patients developed one major complication, 249 (3.2%) patients developed two major complications, and 151 (1.9%) patients developed three major complications. The most common complication was intra/postoperative red blood cell transfusion (23.2%). Three multivariate logistic regression models were employed to identify factors associated with ≥ 1, ≥ 2, and ≥ 3 major complications. Patient variables present across all three models were osteotomy, pelvic fixation, operation time ≥4 hours, bleeding disorder, and American Society of Anesthesiology Class ≥ 3.

CONCLUSION

Several risk factors were identified for the development of major complications after elective PLF. Identification of these factors can improve the selection of appropriate surgical candidates, patient risk stratification, and patient postoperative safety.

LEVEL OF EVIDENCE

3.

Optimization of technique for insertion of implants at the supra-acetabular corridor in pelvis and acetabular surgery

The technique for application of implants at the sciatic buttress has been well described in the pelvic and acetabular fracture reconstruction literature. We described a new use of the inlet–obturator oblique view for the identification of the anterior inferior iliac spine, which is the entry point of implants, and we provide a detailed fluoroscopic and radiographic description of this view. A small series of 15 patients who underwent an application of an anterior inferior pelvic external (supra-acetabular) fixator via this technique is presented. We consider the use of the obturator oblique for the identification of the entry point unnecessary, and we advocate for the use of only the inlet–obturator oblique and iliac oblique views when implants are applied to the sciatic buttress.

Analysis of the s2 alar-iliac screw as compared with the traditional iliac screw: does it increase stability with sacroiliac fixation of the spine?

BACKGROUND CONTEXT

Arthrodesis of the lumbosacral junction continues to be a challenge in pediatric and adult spinal deformity surgery.

PURPOSE

To evaluate the biomechanical rigidity of two types of lumbosacral fixation. Our hypothesis was that the use of S2 alar-iliac (S2AI) fixation will result in statistically similar biomechanical fixation as compared with use of an iliac screw with a 95% confidence interval.

STUDY SETTING

Controlled biomechanical laboratory METHODS: Ten human cadaveric lumbosacral specimens were separated into two test groups: (1) S2AI (n=5) and (2) iliac screw (n=5). S2AI and iliac screws were placed according to current clinical practice techniques. Specimens were mounted in an unconstrained dual leg stance configuration for testing in flexion, extension, lateral bending, and axial rotation. These loads were induced by moving the offset loading arm 10 mm in the respective direction from the point of neutral motion with displacement control up to a 10 N-m moment, except axial rotation which used a 4 N-m moment. Optical tracking was used to monitor motion of the vertebra, pelvis, and fixation instrumentation during testing. Specimens were tested in intact and instrumented states. The stiffness values between S2AI and iliac screw configurations were compared.

DISCLOSURE

The present study received external research support (>$50,000 -<$75,000) from Stryker Spine (Allendale, NJ, USA).

RESULTS

There was a consistent trend of increased construct stiffness for all S2AI samples compared with the iliac screw group. However, none of the groups tested reached statistical significance for a 95% confidence interval.

CONCLUSIONS

S2AI screws are just as stable as iliac screws with biomechanical testing in flexion, extension, rotation, lateral bending, and axial rotation. Given the similarities of biomechanical testing to human movements, these findings support S2AI screws as a viable option for lumbosacral fixation.

Accuracy of Iliac Screws Insertion in Adult Spinal Deformity Surgery: Relationship Between Misplacement and the Iliac Morphologies

STUDY DESIGN

Retrospective study.

OBJECTIVE

To investigate the accuracy of freehand iliac screw insertion and to determine how this can be performed safely.

BACKGROUND AND METHODS

Seventy-seven adult scoliosis patients with an average age of 70.1 years who underwent spinal deformity surgery with spinopelvic fixation using bilateral iliac screws were enrolled. Penetration of the iliac table was assessed using postoperative computed tomography. Screw penetration of the iliac table or screw insertion from the sacroiliac joint was considered misplacement. Screw positioning was classified as the screw being in the proper position (group C), the screw penetrating the outer table (group O), and the screw penetrating the inner table (group I). The iliac opening angle and the distance between the posterior superior iliac spines (PSISs) were measured using preoperative computed tomography. The angle between the sacral slope and the iliac screw, termed as the sagittal screw angle, was measured using postoperative lateral lumbar radiography.

RESULTS

Of the 154 iliac screws in 77 patients, 14 screws in 12 patients penetrated the outer table and 12 screws in 11 patients penetrated the inner table. The total proportion of misplacement was 18.8%, although there were no major complications. With regard to iliac morphology, the iliac opening angle was 24.2±4.3 degrees and the distance between the PSISs was 90.6±7.7 mm. The distance between the PSISs correlated negatively with the iliac opening angle. The iliac opening angle was smaller in group O than in group C (P<0.05). The sagittal screw angle in group I was smaller than that in group C (P<0.01).

CONCLUSIONS

Screw penetration of the outer iliac table possibly occurred in patients with a narrow iliac opening angle. Screw penetration of the inner table occurred when the screw was inserted more cranially than the sacral slope. Therefore, the iliac screw should be inserted approximately parallel to the sacral slope.

Use of Inlet-Obturator Oblique View (Leeds View) for Placement of Posterior Wall Screws in Acetabular Fracture Surgery

Posterior wall (PW) fractures are the most common fractures requiring surgical fixation in acetabular surgery. Extra-articular screw placement must be confirmed intraoperatively. Herein we describe the use of the inlet and obturator oblique view (the Leeds view) for screw placement in elementary PW and in associated both-column with PW fractures. We highlight our steps to ensure accurate placement in a small series of patients.

Traumatic dislocation of the S1 polyaxial pedicle screw head: a case report

Polyaxial screw head dislocation in the absence of a manufacture defect is extremely rare and represents a biomechanical overload of the screw, leading to early failure. A 58-year-old gentleman underwent instrumented fusion using polyaxial pedicle screws-titanium rod construct with interbody cage for spondylolytic spondylolisthesis at the L5/S1 level. He attempted to bend forward ten days after the surgery which resulted in a dislocation of the right S1 polyaxial screw head from the screw shank with recurrence of symptoms. He underwent revision surgery uneventfully. This case highlights the need to pay particular attention to the strength of fixation and the amount of release to avoid such a complication.

Strain in Posterior Instrumentation Resulted by Different Combinations of Posterior and Anterior Devices for Long Spine Fusion Constructs

STUDY DESIGN

Clinically related experimental study.

OBJECTIVE

Evaluation of strain in posterior low lumbar and spinopelvic instrumentation for multilevel fusion resulting from the impact of such mechanical factors as physiologic motion, different combinations of posterior and anterior instrumentation, and different techniques of interbody device implantation.

SUMMARY OF BACKGROUND DATA

Currently different combinations of posterior and anterior instrumentation as well as surgical techniques are used for multilevel lumbar fusion. Their impact on risk of device failure has not been well studied. Strain is a well-known predictor of metal fatigue and breakage measurable in experimental conditions.

METHODS

Twelve human lumbar spine cadaveric specimens were tested. Following surgical methods of lumbar pedicle screw fixation (L2-S1) with and without spinopelvic fixation by iliac bolt (SFIB) were experimentally modeled: posterior (PLF); transforaminal (TLIF); and a combination of posterior and anterior interbody instrumentation (ALIF+PLF) with and without anterior supplemental fixation by anterior plate or diverging screws through an integrated plate. Strain was defined at the S1 screws, L5-S1 segment of posterior rods, and iliac bolt connectors; measurement was performed during flexion, extension, and axial rotation in physiological range of motion and applied force.

RESULTS

The highest strain was observed in the S1 screws and iliac bolt connectors specifically during rotation. The S1 screw strain was lower in ALIF+PLF during sagittal motion but not rotation. Supplemental anterior fixation in ALIF+PLF diminished the S1 strain during extension. Strain in the posterior rods was higher after TLIF and PLF and was increased by SFIB; this strain was lowest after ALIF+PLF, as supplemental anterior fixation diminished the strain during extension, in particular, cages with anterior screws more than anterior plate. Strain in the iliac bolt connectors was mainly determined by direction of motion.

CONCLUSIONS

Different devices modify strain in low posterior instrumentation, which is higher after transforaminal and posterior techniques, specifically with spinopelvic fixation.

LEVEL OF EVIDENCE

N/A.

Perpendicular Iliac Screw Placement for Reinforcement of Spinopelvic Stabilization

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

Robotic-guided sacro-pelvic fixation using S2 alar-iliac screws: feasibility and accuracy

PURPOSE

To review our experience with robotic guided S2-alar iliac (S2AI) screw placement.

METHODS

We retrospectively reviewed patients who underwent S2AI fixation with robotic guidance. Screw placement and deviation from the preoperative plan were assessed by fusing preoperative CT (with the planned S2AI screws) to postoperative CT. The software's measurement tool was used to compare the planned vs. actual screw placements in axial and lateral views, at entry point to the S2 pedicle and at a 30 mm depth at the screws' mid-shaft, in a resolution of 0.1 mm. Medical charts were reviewed for technical issues and intra-operative complications.

RESULTS

35 S2AI screws were reviewed in 18 patients. The patients' mean age was 60 years. No intra-operative complications that related to the placement of S2AI screws were reported and robotic guidance was successful in all 35 screws. Post-operative CT scans showed that all trajectories were accurate. No violations of the iliac cortex or breaches of the anterior sacrum were noted. At the entry point, the screw deviated from the pre-operative plan by 3.0 ± 2.2 mm in the axial plane and 1.8 ± 1.6 mm in the lateral plane. At 30 mm depth, the screw deviated from the pre-operative plan by 2.1 ± 1.3 mm in the axial plane and 1.2 ± 1.1 mm in the lateral plane.

CONCLUSIONS

Robotic guided S2AI screw placement is feasible and accurate. No screw malpositions or complications that related to the placement of S2AI screws occurred in this series. Larger studies are needed to assess the long-term clinical outcomes of robotic guided sacral-pelvic fixation.

Matched-pair cohort study of 1-year patient-reported outcomes following pelvic fixation

BACKGROUND CONTEXT

Pelvic fixation improves fusion and stability for thoracolumbar constructs that extend across the L5-S1 junction. No patient-reported outcomes have been published to evaluate patients' functional outcomes following these procedures compared with pelvis-sparing procedures.

PURPOSE

The goal of this study is to identify the effect of pelvic fixation on both objective and patient-reported outcomes.

STUDY DESIGN/SETTING

This was a retrospective, matched cohort study.

PATIENT SAMPLE

The sample comprised adult patients undergoing spine surgery at our institution who had complete 1-year postoperative follow-up.

OUTCOME MEASURES

Patient-reported outcome instruments (Oswestry Disability Index [ODI], Short-Form 12-item survey, and EuroQol-5D) and objective measures (length of hospital stay, discharge disposition, postoperative complications, and readmission rates) were considered.

METHODS

We identified patients in our outcomes registry undergoing instrumented spinal fusion involving the pelvis between October 2010 and May 2014 who had 1-year follow-up data. Nearest-neighbor 1:1 matched controls were identified using propensity scoring from the cohort of patients undergoing any spinal procedure which extended caudally to the lumbar spine or sacrum. Objective and patient-reported outcomes were compared between cases and controls.

RESULTS

There were 44 patients who underwent spinal procedures involving the pelvis and had 1-year follow-up data. An equal number of controls were identified and had similar baseline demographic and clinical characteristics. No significant differences were found among operative variables or objective complication rates. Patients undergoing pelvic fixation had moderately greater improvement at 3 months as measured by ODI, but this difference was not present at 1 year. Other patient-reported outcome measures were equivocal between groups.

CONCLUSIONS

This matched cohort study demonstrates that inclusion of the pelvis in spinal hardware constructs is not associated with increased complications and may slightly improve patient disability at 1 year. Given that pelvic fixation may reduce L5-S1 breakdown and improve biomechanics, surgeons should more readily include the pelvis in instrumented fusion procedures.