S2 Alar Screw Insertion Accuracy and Factors Associated With Screw Loosening and Lumbosacral Nonunion

OBJECTIVE

To investigate S2 alar screw (S2AS) accuracy and factors associated with S2AS loosening and lumbosacral nonunion.

METHODS

We retrospectively reviewed patients who underwent lumbosacral fusion surgery with S2AS addition under fluoroscopy. S2AS loosening and lumbosacral nonunion were analyzed using a 1-year postoperative computed tomography. S2AS insertion accuracy was originally classified as accurate, short, anterior perforation, lateral perforation, and sacroiliac joint (SIJ) deviation among lateral perforation. Clinical data including sex, age, body mass index, fused segments, fusion procedure, primary or revision surgery, Japanese Orthopedic Association scores and complications were collected. Factors associated with S2AS loosening and lumbosacral nonunion were analyzed.

RESULTS

A total of 37 patients (74 screws, age: 63.78 ± 13.57 years, female/male: 14/23 patients, body mass index: 23.11 ± 2.53, fused segments: 1-4 levels, revision: 38%) were included. S2AS loosening and lumbosacral nonunion were observed in 18 screws (13%) and 8 patients (22%) respectively. Only 35 screws (47%) were inserted accurately in our classification. Short, lateral perforation, and anterior perforation were observed in 14 screws (19%), 22 screws (30%), and 3 screws (4.1%). SIJ deviation was seen in 15 screws (20%) Factors associated with S2AS loosening were older age (P = 0.038), fusion levels (P = 0.011), and SIJ deviation (P < 0.001). S2AS loosening affects S1 pedicle screw (S1PS) loosening (P = 0.001). Furthermore, S2AS loosening is a risk factor for lumbosacral nonunion (P = 0.046).

CONCLUSIONS

S2AS insertion under fluoroscopy is inaccurate. S2AS loosening induces S1PS loosening and lumbosacral nonunion. Surgeons should avoid deviating to SIJ, especially in older patients and relatively longer fusion.

The effects of topping-off instrumentation on biomechanics of sacroiliac joint after lumbosacral fusion

BACKGROUND

Lumbar/lumbosacral fusion supplemented with topping-off devices has been proposed with the aim of avoiding adjacent segment degeneration proximal to the fusion construct. However, it remains unclear how the biomechanics of the sacroiliac joint (SIJ) are altered after topping-off surgery. The objective of this study was to investigate the biomechanical effects of topping-off instrumentation on SIJ after lumbosacral fusion.

METHODS

The validated finite element model of an intact lumbar spine-pelvis segment was modified to simulate L5-S1 interbody fusion fixed with a pedicle screw system. An interspinous spacer, Device for Intervertebral Assisted Motion (DIAM), was used as a topping-off device and placed between interspinous processes of the L4 and L5 segments. Range of motion (ROM), von-Mises stress distribution, and ligament strain at SIJ were compared between fusion (without DIAM) and topping-off (fusion with DIAM) models under moments of four physiological motions.

RESULTS

ROM at the left and right SIJs in the topping-off model was higher by 26.9% and 27.5% in flexion, 16.8% and 16.1% in extension, 18.8% and 15.8% in lateral bending, and 3.7% and 7.4% in axial rotation, respectively, compared to those in the fusion model. The predicted stress and strain data showed that under all physiological loads, the topping-off model exhibited higher stress and ligament strain at the SIJs than the fusion model.

CONCLUSIONS

Motion, stress, and ligament strain at SIJ increase when supplementing lumbosacral fusion with topping-off devices, suggesting that topping-off surgery may be associated with higher risks of SIJ degeneration and pain than fusion alone.

Lumbosacral fusion increases the risk of hip osteoarthritis

OBJECTIVE

There may be biomechanical changes in the adjacent hip joint after lumbosacral fusion. The literature has limited information on how these biomechanical changes may result in hip joint space.

MATERIAL

METHOD: Our retrospective study examined hip joint space narrowing in patients who underwent lumbosacral fusion between 2020 and 2022. In addition, spinopelvic parameters such as sacral slope, the sagittal vertical axis, pelvic incidence, lumbar lordosis, and pelvic tilt were compared in patients who underwent short-segment (up to three levels, S group) and long-segment (4 and higher levels, L group) fusions.

RESULTS

Our study found no significant relationship between spinopelvic parameters and joint space narrowing in the S and L groups. In addition, it was determined that there was more narrowing in the hip joint space in the long-segment group, and there was a positive correlation between the segment length and the narrowing in the hip joint space.

CONCLUSION

After lumbosacral fusion, narrowing of the hip joint space was observed. Particularly patients with long-segment lumbosacral fusion should be followed closely regarding hip osteoarthritis risk.

Midline Lumbar Fusion Versus Posterior Lumbar Interbody Fusion Involving L5-S1 For Degenerative Lumbar Diseases: A Comparative Study

BACKGROUND

A retrospective cohort study to evaluate the efficacy and safety of midline lumbar fusion (MIDLF) for lumbosacral fusion compared to posterior lumbar interbody fusion (PLIF).

METHODS

Patients who had undergone posterior lumbosacral fusion surgery were divided into a MIDLF group (n = 37) and a PLIF group (n = 42). The follow-up time was at least 12 months. The operation data, recovery condition, complications, clinical outcomes, and status of implants and fusion were compared between the 2 groups.

RESULTS

The MIDLF group experienced significantly less blood loss, lower postoperative creatine kinase levels and total drainage volume, earlier time to ambulation, and less hospital stay times after surgery compared to the PLIF group (P < 0.05). The mean postoperative back pain visual analog scale scores in the MIDLF group were significantly lower than the PLIF group (P < 0.05). The improvement in Oswestry Disability Index scores during 3-month follow-up displayed a significant difference between the 2 groups (P < 0.05). The fusion rate tended to be higher in the MIDLF group; however, the difference was not significant (P > 0.05). There was no significant difference in respect to screw loosening and cage subsidence rate. There were 2 cases of complications both occurring in the PLIF group.

CONCLUSIONS

MIDLF is safe and effective for lumbosacral fusion and in line with the concept of enhanced recovery after surgery.

Percutaneous Sacroplasty for Symptomatic Sacral Pedicle Screw Loosening

Background

This study aimed to evaluate the efficacy of fluoroscopy-guided percutaneous sacroplasty in patients with sacral pedicle screws loosening after instrumented spinal fusion.

Methods

We retrospectively reviewed the medical records of 18 patients who underwent percutaneous sacroplasty to treat sacral pedicle screws loosening from January 2016 to December 2019. Imaging studies, visual analog scale (VAS), length of hospital stay, and complications were recorded. The clinical outcomes based on the Oswestry disability index (ODI) and the modified Brodsky's criteria (MBC) were also evaluated to determine the efficacy of percutaneous sacroplasty.

Results

All patients had undergone at least 1 year of follow-up in our institute (range, 12-24 months). The average VAS score was 5.6 (range, 4-7) before surgery and decreased to 1.7 (range, 1-3) at the final visit. All patients were discharged on the next day after surgery. No patients experienced complications, such as cement leakage, deep infection, or neurologic deterioration. All patients achieved good or excellent outcomes based on the MBC. The ODI scores improved from 51.8 preoperatively to 25.6 postoperatively.

Conclusion

Percutaneous sacroplasty was an effective treatment approach for relieving the patient's symptoms caused by sacral pedicle screws loosening and could be a valuable treatment alternative to extensive revision surgery.

Level of clinical evidence

IV.

Effects of anode position on pedicle screw testing during lumbosacral spinal fusion surgery

OF BACKGROUND DATA

Pedicle screws are commonly placed with lumbar/lumbosacral fusions. Triggered electromyography (tEMG), which employs the application of electrical current between the screw and a complementary anode to determine thresholds of conduction, may be utilized to confirm the safe placement of such implants. While previous research has established clinical thresholds associated with safe screw placement, there is variability in clinical practice of anode placement which could lead to unreliable measurements.

PURPOSE

To determine the variance in pedicle screw stimulation thresholds when using four unique anode locations (ipsilateral/contralateral and paraspinal/gluteal relative to tested pedicle screws).

STUDY DESIGN

Prospective cohort study. Tertiary medical center.

PATIENT SAMPLE

Twenty patients undergoing lumbar/lumbosacral fusion with pedicle screws using tEMG OUTCOME MEASURES: tEMG stimulation return values are used to assess varied anode locations and reproducibility based on anode placement.

METHODS

Measurements were assessed across node placement in ipsilateral/contralateral and paraspinal/gluteal locations relative to the screw being assessed. R² coefficients of correlation were determined, and variances were compared with F-tests.

RESULTS

A total of 94 lumbosacral pedicle screws from 20 patients were assessed. Repeatability was verified using two stimulations at each location for a subset of the screws with an R² of 0.96. Comparisons between the four anode locations demonstrated R² values ranging from 0.76 to 0.87. F-tests comparing thresholds between each anode site demonstrated all groups not to be statistically different.

CONCLUSION

The current study, a first-of-its-kind formal evaluation of anode location for pedicle screw tEMG testing, demonstrated very strong repeatability and strong correlation with different locations of anode placement. These results suggest that there is no need to change the side of the anode for testing of left versus right screws, further supporting that placing an anode electrode into gluteal muscle is sufficient and will avoid a sharp ground needle in the surgical field.

Treatment for sacral insufficiency fractures: A systematic review

Intro

Sacral insufficiency fractures after lumbosacral fusion continue to establish themselves as a rare complication after surgery. The diagnosis can often be missed due to inconclusive imaging and non-specific symptoms. In the literature, the treatment of sacral insufficiency fractures varies from non-operative and conservative management to surgical intervention with lumbopelvic fixation.

Methods

We performed a systematic review searching the PubMed database using sacral insufficiency fracture treatment after lumbosacral fusion and sacral insufficiency fracture after posterior spinal instrumentation as keywords.

Results

This search strategy identified 32 publications from the PubMed database for literature review. After evaluating the inclusion and exclusion criteria, a total of 17 articles were included in the review. 65% of sacral insufficiency fractures were managed surgically with 35% of patients proceeding with non-operative, conservative management only. Revision surgery always involved sacropelvic fixation which typically led to immediate resolution or reduction of symptoms, with the exception of 2 cases that did not receive adequate reduction of symptoms. Five cases reported failed non-operative management that subsequently responded to revision surgery.

Conclusion

Outcomes after non-operative management usually leads to symptom resolution; however has a slower symptom relief time as well as a higher chance of failed treatment. Operative outcomes, generally with a variation of sacropelvic fixation lead to immediate symptom resolution and very rarely failed treatment. Clinicians must always maintain a high index of suspicion of new onset lower back or sacral pain after lumbosacral surgery and order a CT scan to rule out a potential insufficiency fracture.

Objectives

The objective of this study was to review the literature to examine treatment options for sacral insufficiency fractures after lumbosacral fusion in order to improve clinical practice and management. This systematic review of the literature regarding treatment of sacral insufficiency fractures will assist clinicians in making the accurate diagnosis and devise a strategic treatment plan for patients with sacral insufficiency fractures after spinal instrumentation.

Early Medical Complications and Delayed Discharge after Spinopelvic Fusion: A Comparative Analysis of 887 NSQIP Cases from 2006 to 2016

Introduction

The effect of pelvic fixation on postoperative medical complications, blood transfusion, length of hospital stay, and discharge disposition is poorly understood. Determining factors that predispose patients to increased complications after spinopelvic fusion will help surgeons to plan these complex procedures and optimize patients preoperatively.

Methods

We conducted a retrospective cohort study using data from the ACS-NSQIP database between 2006 and 2016 of patients who underwent lumbar fusion with and without spinopelvic fixation. Data regarding demographics, complications, hospital stay, and discharge disposition were collected.

Results

A total of 57,417 (98.5%) cases of lumbar fusion without spinopelvic fixation (LF) and 887 (1.5%) cases of lumbar fusion with spinopelvic fixation (SPF) were analyzed. The transfusion rate in the SPF group was 59.3% vs 13% in the LF group (p < 0.001). The mean length of stay (LOS) and discharge to skilled nursing facility (SNF) were significantly different (LOS: SPF 6.5 days vs LF 3.5 days p < 0.001; SNF: SPF 21.3% vs LF 10.4% p < 0.001). After controlling for demographic differences, the overall complication rates were not significantly different between the groups (p = 0.531). The odds ratio for transfusion in the SPF group was 2.9 (p < 0.001). The odds ratio for increased LOS and increased care discharge disposition were elevated in the SPF group (LOS OR: 1.3, p < 0.012, Discharge disposition OR: 1.8, p < 0.001).

Conclusions

Patients who underwent SPF had increased complications, transfusion rate, LOS, and discharge to SNF or subacute rehab facilities as compared with patients who underwent LF. SPF remains an effective technique for achieving lumbosacral arthrodesis. Surgeons should consider the implications of the associated complication profile for SPF and the value of preoperative optimization in a select cohort of patients.

Sacroiliac joint syndrome after lumbosacral fusion

INTRODUCTION

One-third of low back pain cases are due to the sacroiliac (SI) joint. The incidence increases after lumbosacral fusion. A positive Fortin Finger Test points to the SI joint being the origin of the pain; however, clinical examination and imaging are not specific and minimally contributory. The gold standard is a test injection of local anesthetic. More than 70% reduction in pain after this injection confirms the SI joint is the cause of the pain. The aim of this study was to evaluate the decrease in pain on a Numerical Rating Scale (NRS) after intra-articular injection into the SI joint. We hypothesised that intra-articular SI injection will significantly reduce SI pain after lumbosacral fusion.

METHODS

All patients with pain (NRS>7/10) suspected of being caused by SI joint syndrome 1 year after lumbosacral fusion with positive Fortin test were included. Patients with lumbar or hip pathologies or inflammatory disease of the SI joint were excluded. Each patient underwent a 2D-guided injection of local anesthetic into the SI joint. If this failed, a second 2D-guided injection was done; if this also failed, a third 3D-guided injection was done. Reduction of pain on the NRS by>70% in the first 2 days after the injection confirmed the diagnosis. Whether the injection was intra-articular or not, it was recorded. Ninety-four patients with a mean age of 57 years were included, of which 70% were women.

RESULTS

Of the 94 patients, 85 had less pain (90%) after one of the three injections. The mean NRS was 8.6/10 (7-10) before the injection and 1.7/10 after the injection (0-3) (p=0.0001). Of the 146 2D-guided injections, 41% were effective and 61% were intra-articular. Of the 34 3D-guided injections, 73% were effective and 100% were intra-articular.

DISCUSSION

This study found a significant decrease in SI joint-related pain after intra-articular injection into the SI joint in patients who still had pain after lumbosacral fusion. If this injection is non-contributive when CT-guided under local anesthesia, it can be repeated under general anesthesia with 3D O-arm guidance. This diagnostic strategy allowed us to confirm that pain originates in the SI joint after lumbosacral fusion in 9 of 10 patients.

CONCLUSION

If the first two CT-guided SI joint injections fail, 3D surgical navigation is an alternative means of doing the injection that helps to significantly reduce SI joint-related pain after lumbosacral fusion.

LEVEL OF EVIDENCE

IV, retrospective study.

Risk Factors for Loosening of S2 Alar Iliac Screw: Surgical Outcomes of Adult Spinal Deformity

Study Design

Retrospective study.

Purpose

To determine the risk factors for S2 alar iliac (S2AI) screw loosening and its association with lumbosacral fusion in patients with adult spinal deformity (ASD).

Overview of Literature

S2AI screws have been widely used for ASD surgery in recent years. However, no studies have analyzed the risk factors for loosening of S2AI screws and its association with lumbosacral fusion.

Methods

Cases of 50 patients with ASD who underwent long spinal fusion (>9 levels) with S2AI screws were retrospectively reviewed. Loosening of S2AI screws and S1 pedicle screws and bone fusion at the level of L5–S1 at 2 years after surgery were investigated using computed tomography. In addition, risk factors for loosening of S2AI screws were determined in patients with ASD.

Results

At 2 years after surgery, 33 cases (66%) of S2AI screw loosening and six cases (12%) of S1 pedicle screw loosening were observed. In 40 of 47 cases (85%), bone fusion at L5–S1 was found. Pseudarthrosis at L5–S1 was not significantly associated with S2AI screw loosening (19.3% vs. 6.3%, p=0.23), but significantly higher in patients with S1 screw loosening (83.3% vs. 4.9%, p<0.001). On multivariate logistic regression analyses, high upper instrumented vertebra (UIV) level (T5 or above) (odds ratio [OR], 4.4; 95% confidence interval [CI], 1.0–18.6; p=0.045) and obesity (OR, 11.4; 95% CI, 1.2–107.2; p=0.033) were independent risk factors for S2AI screw loosening.

Conclusions

High UIV level (T5 or above) and obesity were independent risk factors for S2AI screw loosening in patients with lumbosacral fixation in surgery for ASD. The incidence of lumbosacral fusion is associated with S1 screw loosening, but not S2AI screw loosening.

The sacral screw placement depending on morphological and anatomical peculiarities

PURPOSE

Various pathologies of the lumbosacral junction require fusion of the L5/S1 segment. However, pseudarthroses, which often come along with sacral screw loosening, are problematic. The aim of the present investigation was to elaborate the morphological features of the L5/S1 segment to define a so-called "safe zone" for bi- or tricortical screw placement without risking a damage of the iliac vessels.

METHODS

A total of one hundred computed tomographies of the pelvis were included in this investigation. On axial and sagittal slices, pedicle morphologies, the prevertebral position of the iliac vessels, the spinal canal and the area with the largest bone density were analyzed.

RESULTS

Beginning from the entry point of S1-srews iliac vessels were located at an average angle of 7° convergence, the spinal canal at 38°. Bone density was significantly higher centrally with a mean value of 276 Hounsfield Units compared to the area of the Ala ossis sacri. The largest intraosseous screw length could be achieved at an angle of 25°. The average pedicle width was 20 mm and the pedicle height 13 mm.

CONCLUSIONS

A "safe-zone" for bicortical screw placement at S1 with regard to the course of the iliac vessels could be defined between 7° and 38° convergence. Regarding the area offering the largest bone density and the maximal possible screw length, a convergence of 25° is recommended at S1 to reduce the incidence of screw loosening. Screw diameter, as a further influence factor on screw holding, is limited by pedicle height not pedicle width.

Sacral Endplate Penetrating Screw for Lumbosacral Fixation: A Cadaveric Biomechanical Study

BACKGROUND

Cortical bone trajectory is a relatively new alternative for instrumentation of the lumbar spine. When performing lumbosacral instrumentation, a novel S1 endplate penetrating screw (EPS) has been recently shown to have higher insertional torque than the traditional trajectory screw, but the biomechanical properties of this new trajectory are yet to be verified with the cadaveric studies.

OBJECTIVE

To evaluate 2 screw trajectories in sacra using cyclic loading and pullout tests, and to determine whether bone quality had different effects on the 2 trajectories.

METHODS

Nine cadaveric sacra were used, 5 of which had normal bone mineral density (BMD) and 4 were osteoporotic. Each side of the sacra was randomly assigned to either EPS trajectory or S1-alar screw (S1AS) trajectory. Each screw then underwent cyclic loading followed by pullout force measurement. A mixed-design 2 way ANOVA test was used to detect differences between the groups.

RESULTS

The EPS group had less relative rotation at the bone-screw interface during cyclic loading than the S1AS group (P = .016) regardless of bone quality. The pullout force following the cyclic loading was significantly higher in the EPS group (2349 ± 838 N) than the S1AS group (917 ± 909 N) in normal bone (P < .0001). The difference was more pronounced in osteoporotic bone with the EPS (1075 ± 216 N) compared to the S1AS (365 ± 422 N; P < .0001).

CONCLUSION

The S1 EPS trajectory is significantly more stable against loosening and has a higher pullout force compared to the S1AS trajectory. The difference between the 2 trajectories is more pronounced in osteoporotic bone.

Incidence, diagnosis and management of sacroiliitis after spinal surgery: a systematic review of the literature

The sacroiliac joint (SIJ) is a possible source of persistent or new onset pain after lumbar or lumbosacral fusion. The aim of this paper is to systematically review and analyze the available literature related to the incidence, diagnosis and management of sacroiliitis after spinal arthrodesis. The authors independently screened the titles and abstracts of all articles identified concerning sacroiliac joint pain after lumbar or lumbosacral fusion, to assess their suitability to the research focus. The average incidence of sacroiliitis after lumbar or lumbosacral arthrodesis was found to be 37 ± 28.48 (range 6-75), increasing directly to the number of fused segments involved, especially when the sacrum is included. The most accurate evaluation is the image-guided injection of anesthetic solutions in the joint. Surgery treatment may be considered when conservative therapy fails, with open surgery or with minimally invasive SIJ fusion. Although the risk of developing SIJ degeneration is unclear, the results indicate that pain and degeneration of SIJ develop more often in patients undergoing lumbosacral fusion regardless of the number of melting segments. The treatment of sacroiliitis appears to be independent of his etiology, with or without previous instrumentation on several levels.

Percutaneous and open iliac screw safety and accuracy using a tactile technique with adjunctive anteroposterior fluoroscopy

BACKGROUND CONTEXT

All currently described percutaneous iliac screw placement methods are entirely dependent on fluoroscopy.

PURPOSE

The purpose of this study was to determine the safety and the accuracy of percutaneous and open iliac screw placement using a primarily tactile technique with adjunctive anteroposterior (AP) fluoroscopy.

STUDY DESIGN/CONTEXT

All patients who underwent open and percutaneous iliac screw placement over a 5-year period were identified. Charts were reviewed to assess for any instances of neurologic or vascular injury associated with iliac screw placement. Screw accuracy was judged with postoperative computed tomography (CT) scans.

PATIENT SAMPLE

A total of 133 patients were identified who underwent open or percutaneous iliac screw placement. Computed tomography scans were available for 57 patients, and all of these patients were included in the study, with a total of 115 iliac screws.

OUTCOME MEASURES

Radiographic measurements were performed, consisting of the distance of the iliac screw to the sciatic notch on postoperative radiographs and CT scans. Computed tomography scans were used to determine iliac screw accuracy.

METHODS

Charts were reviewed to assess for any neurologic or vascular injuries related to screw placement. The distance of the iliac screw to the sciatic notch was measured and compared on AP radiography and CT scans. Computed tomography scans were assessed for any screw violation of the iliac cortex or the sciatic notch. The accuracy of open iliac screw placement was compared with minimally invasive percutaneous placement.

RESULTS

There were no neurologic or vascular injuries related to screw placement in the 133 patients. Computed tomography scans were available for 115 iliac screws, with 3 cortical breaches, all by less than 2 mm. All 112 other screws were accurately intraosseous. There was a strong correlation between the iliac screw to the sciatic notch distance when measured by CT scan compared with AP radiography (r=0.9), thus validating the accuracy of AP fluoroscopy in guiding iliac screw placement with respect to the sciatic notch. Iliac screw accuracy was equal with the open and percutaneous insertion techniques.

CONCLUSIONS

The described surgical technique represents a safe and reliable surgical option for iliac screw placement. Intraoperative AP fluoroscopy accurately reflects the distance of the iliac screw to the sciatic notch. Percutaneous iliac screws placed with this technique are as accurate as open iliac screws.

Using spinopelvic parameters to estimate residual lumbar lordosis assuming previous lumbosacral fusion-a study of normative values

BACKGROUND CONTEXT

Pelvic incidence (PI)=pelvic tilt (PT)+sacral slope (SS) is an established trigonometric equation which can be expanded from studying the fixed pelvis with the spine to a fixed spinopelvic complex with the remnant spine, in scenarios of spinopelvic fusion or ankylosis. For a fixed spinopelvic complex, we propose the equation termed: lumbar incidence (LI)=lumbar tilt (LT)+lumbar slope (LS).

PURPOSE

This study aimed to establish reference values for LI, LT, and LS at each lumbar vertebral level, and to show how LI can be used to determine residual lumbar lordosis (rLL).

STUDY DESIGN

This is a cross-sectional study of prospectively collected data, conducted at a single academic tertiary health-care center.

PATIENT SAMPLE

The study included 53 healthy patients aged 19-35 with first episode mechanical low back pain for a period of <3 months. Patients with previous spinal intervention, those with known or suspected spinal pathologies, and those who were pregnant, were excluded.

OUTCOME MEASURES

Radiological measurements of LI, LT, LS, and rLL.

METHODS

All patients had full-body lateral standing radiographs obtained via a slot scanner. Basic global and regional radiographic parameters, spinopelvic parameters, and the aforementioned new parameters were measured. LI was correlated with rLL at each level by plotting LI against rLL on scatter plots and drawing lines-of-best-fit through the datapoints.

RESULTS

The mean value of L5I was 22.82°, L4I was 6.52°, L3I was -0.92°, L2I was -5.56°, and L1I was -5.95°. LI turns negative at L3, LS turns negative at the L3/L4 apex, and LT remains positive throughout the lumbar spine. We found that the relationship of LI with its corresponding rLL follows a parabolic trend. Thus, rLL can be determined from the linear equations of the tangents to the parabolic lumbar spine. We propose the LI-rLL method for determining rLL as the LI recalibrates via spinopelvic compensation post instrumentation, and thus the predicted rLL will be based on this new equilibrium, promoting restoration of harmonized lordosis. The rLL-to-LI ratio is a simplified, but less accurate, method of deriving rLL from LI.

CONCLUSIONS

This study demonstrates the extended use of PI=PT+SS proposed as LI=LT+LS. These new spinopelvic reference values help us better understand the position of each vertebra relative to the hip. In situations when lumbar vertebrae are fused or ankylosed to the sacrum to form a single spinopelvic complex, LI can be used to determine rLL, to preserve spinal harmony within the limits of compensated body balance.

S2-AI screw placement with the aide of electronic conductivity device monitoring: a retrospective analysis

STUDY DESIGN

A retrospective analysis of two consecutive patients who underwent a novel surgical technique.

OBJECTIVE

A report of a novel surgical technique utilizing an electronic conductivity device guidance to aide placement of S2-Alar-Iliac (S2-AI) instrumentation. Electronic conductivity guidance for instrumentation of the thoracolumbar spine is an accepted means of improving intraoperative accuracy. Although commercially available for percutaneous techniques, there is a paucity of literature regarding its use. Percutaneous implantation of S2-AI screws has been previously described as another technique surgeons can avail, primarily employing fluoroscopy as a means of intraoperative feedback. We describe a novel technique that utilizes electronic conductivity as an added feedback measure to increase accuracy of percutaneous S2-AI fixation.

METHODS

Two patients were treated by the senior author (FAS) who underwent surgery employing S2-AI fixation utilizing an electronic conductivity device (Pediguard cannulated probe, Spineguard, Paris, France). The surgical technique, case illustrations, and radiographic outcomes are discussed.

RESULTS

Stable and accurate fixation was attained in both patients. There were no peri-operative complications related to hardware placement.

CONCLUSION

To the authors' knowledge, this is the first reported literature combining S2-AI screws with electronic conductivity for immediate intraoperative feedback. This technique has the opportunity to provide surgeons with increased accuracy for placement of S2-AI screws while improving overall radiation safety. This feedback can be particularly helpful when surgeons are learning new techniques such as placement of S2AI screws.

Reduction and fusion in high-grade L5-S1 spondylolisthesis by a single posterior approach. Results in 50 patients

INTRODUCTION

Treatment strategies in high-grade L5-S1 spondylolisthesis are controversial. Reduction of slippage, correction of lumbosacral kyphosis and the necessity of a complementary anterior approach are debated in the literature. The present study reports clinical and radiological outcome for reduction and instrumented fusion on a single posterior approach.

MATERIAL AND METHOD

A retrospective study included all consecutive adolescent and young adult patients operated on by a single surgeon (D.C.) for high-grade (Meyerding 3-4-5) L5-S1 spondylolisthesis. The technique consisted in reduction of lumbosacral kyphosis and posterolateral fusion on a single posterior approach without resection of the sacral dome or complementary anterior approach. Only cases of adult ptosis required impacted tibial interbody graft. Clinical complications, radiologic lumbopelvic results and sagittal balance were analyzed at last follow-up.

RESULTS

Fifty patients, with a mean age at surgery of 21±11 years, were followed up for a mean 5.5±4.6 years. Mean lumbosacral angle was reduced by 25° (from 76° to 101°; P<0.05), and mean listhesis grade by >50% (from 75% to 23%; P<0.0001), without correction loss at last follow-up. C7 sagittal offset was corrected (from 8° to 4°; P<0.05), with harmonization of lumbar (from 57° to 64°; P<0.001) and thoracic curvature (from 37° to 44°; P=0.1). Seventeen patients (34%) showed postoperative radicular deficit, without sequelae at last follow-up. There were no cauda equina lesions. Bone fusion was achieved in 42 patients (84%), in the same surgical step. After revision by complementary interbody graft, there was no residual non-union.

CONCLUSION

Surgery on a single posterior approach gave reliable results in high-grade spondylolisthesis in adolescents and young adults. The technique is not however, free of risk (transient neurologic deficit and non-union), and patients should be forewarned. Complementary interbody graft can be reserved to adult ptosis with incomplete reduction of lumbosacral kyphosis and to revision surgery for non-union.

LEVEL OF EVIDENCE

IV, retrospective study.

Successful salvage surgery for failed transforaminal lumbosacral interbody fusion using the anterior transperitoneal approach

Transforaminal lumbar interbody fusion (TLIF) is a popular posterior spinal fusion technique, but sometimes require salvage surgery when implant failure occurs, which involves possible neural damage due to postoperative adhesion. The current report deals with successful anterior transperitoneal salvage surgery for failed L5‐S TLIF with less neural invasiveness.

Surgical treatment of sacral fractures following lumbosacral arthrodesis: Case report and literature review

Sacral fractures following posterior lumbosacral fusion are an uncommon complication. Only a few case series and case reports have been published so far. This article presents a case of totally displaced sacral fracture following posterior L4-S1 fusion in a 65-year-old patient with a 15-year history of corticosteroid use who underwent open reduction and internal fixation using iliac screws. The patient was followed for 2 years. A thorough review of the literature was conducted using the Medline database between 1994 and 2014. Immediately after the revision surgery, the patient’s pain in the buttock and left leg resolved significantly. The patient was followed for 2 years. The weakness in the left lower extremity improved gradually from 3/5 to 5/5. In conclusion, the incidence of postoperative sacral fractures could have been underestimated, because most of these fractures are not visible on a plain radiograph. Computed tomography has been proved to be able to detect most such fractures and should probably be performed routinely when patients complain of renewed buttock pain within 3 mo after lumbosacral fusion. The majority of the patients responded well to conservative treatments, and extending the fusion construct to the iliac wings using iliac screws may be needed when there is concurrent fracture displacement, sagittal imbalance, neurologic symptoms, or painful nonunion.

Posterior surgery in high-grade spondylolisthesis

INTRODUCTION

High-grade L5-S1 spondylolisthesis alters sagittal spinopelvic balance, which can cause low back pain and progressive neurologic disorder. The present study assessed spondylolisthesis reduction and maintenance over time with L4-S1 versus L5-S1 fusion using a lever-arm system and posterior fusion combined with lumbosacral graft.

MATERIALS AND METHODS

Forty patients were operated on for symptomatic high-grade spondylolisthesis, 34 of whom had full pre- and post-operative radiological analysis, with a mean follow-up of 5.4years. There were 9 L5-S1 and 25 L4-S1 instrumentations. Analysis of spinopelvic and slipping parameters and the evolution of segmental lordosis compared results between L5-S1 and L4-S1 instrumentation.

RESULTS

Mean Taillard spondylolisthesis index decreased from 64% to 37% (P=0.0001). Overall sagittal spinopelvic balance was not significantly changed. Overall L1-S1 and segmental L4-L5 lordosis were not affected by instrumentation. Mean L5-S1 segmental lordosis increased from 11° to 18°. There was loss of reduction from 19° to 14° with L5-S1 instrumentation, in contrast to maintained reduction with L4-S1 instrumentation (P=0.006).

CONCLUSION

The lever-arm system provided anterior-posterior reduction of spondylolisthesis and corrected slippage. Postoperative change in overall sagittal spinopelvic balance was slight and constant. Posterior L4-S1 fusion provided better long-term control of L5-S1 lordosis reduction than the shorter L5-S1 fusion. Retrospective study of level IV.

Description of a transosseous approach to the L5-S1 disc and 2 clinical case reports

BACKGROUND

The lumbosacral disc with the adjacent iliac crest and its relationships to neurologic, visceral, and vascular structures is difficult to approach with cannula-based retractor systems. Previous, less invasive approaches have been described to access this space. Anterior, presacral, and transforaminal approaches each have approach-related complications that have prevented their widespread adoption. A laterally based approach to this disc between the exiting L5 nerve root and traversing S1 nerve root would theoretically eliminate visceral and vascular complications but would necessarily course through the adjacent iliac crest. Our objective was to determine the feasibility of placing an interbody device into the L5-S1 disc space through a lateral transosseous approach.

METHODS

Six transosseous pathways were created from the iliac crest, laterally through the sacral ala, and entering the L5-S1 intervertebral disc space (3 cadavers). The positions of the portals in relation to the local anatomy were evaluated anatomically and with computed tomographic sagittal, coronal, and axial planes. We measured the lengths, heights, and widths of the pathways; distance between the L5 and S1 nerve roots; endplate diameters; and angles necessary to access the space. In addition, 2 clinical cases using the transosseous pathway are presented.

RESULTS

Computed tomographic scans and anatomic evaluations showed that there was an average 22-mm distance between the L5 and S1 nerve roots available to enter the L5-S1 disc space. The mean length of the pathway was 69 mm, and the mean height was 27 mm. The mean angle of the approach was 45° off the posterior-anterior axis, and there was a 25° upward angle from true lateral in the frontal plane.

CONCLUSIONS

A lateral, transosseous approach to the L5-S1 disc space for placing an interbody device is feasible. A closed cannula-based technique may offer reduced approach-related complications. Further studies will be required to determine the reproducibility and utility of this pathway.

A mid-term follow-up result of spinopelvic fixation using iliac screws for lumbosacral fusion

OBJECTIVE

Iliac screw fixation has been used to prevent premature loosening of sacral fixation and to provide more rigid fixation of the sacropelvic unit. We describe our technique for iliac screw placement and review our experience with this technique.

METHODS

Thirteen consecutive patients who underwent spinopelvic fixation using iliac screws were enrolled. The indications for spinopelvic fixation included long segment fusions for spinal deformity and post-operative flat-back syndrome, symptomatic pseudoarthrosis of previous lumbosacral fusions, high-grade lumbosacral spondylolisthesis, lumbosacral tumors, and sacral fractures. Radiographic outcomes were assessed using plain radiographs, and computed tomographic scans. Clinical outcomes were assessed using the Oswestry Disability Index (ODI) and questionnaire about buttock pain.

RESULTS

The median follow-up period was 33 months (range, 13-54 months). Radiographic fusion across the lumbosacral junction was obtained in all 13 patients. The average pre- and post-operative ODI scores were 40.0 and 17.5, respectively. The questionnaire for buttock pain revealed the following: 9 patients (69%) perceived improvement; 3 patients (23%) reported no change; and 1 patient (7.6%) had aggravation of pain. Two patients complained of prominence of the iliac hardware. The complications included one violation of the greater sciatic notch and one deep wound infection.

CONCLUSION

Iliac screw fixation is a safe and valuable technique that provides added structural support to S1 screws in long-segment spinal fusions. Iliac screw fixation is an extensive surgical procedure with potential complications, but high success rates can be achieved when it is performed systematically and in appropriately selected patients.