Sacropelvic Fixation: A Comprehensive Review

Lumbar pedicle subtraction osteotomy: techniques and outcomes

Pedicle subtraction osteotomy has been thoroughly described and studied over the past 2 decades, being applied mainly in the lumbar spine, followed by the thoracic spine. Our better understanding of alignment biomechanics, and the progressive refinements of the surgical technique over time made it a very efficient procedure for the management of fixed sagittal malalignment. However, a long learning curve is mandatory to mitigate the associated risks particularly neurological deficits and achieve satisfactory clinical and radiological outcomes with an acceptable rate of complications.

Treatment of an Impending Pathologic Sacral Fracture with a Novel Iliosacral Fusion Construct: A Case Report

CASE

A 49-year-old woman presented with left leg radiculopathy and posterior pelvic pain. Subsequent evaluation demonstrated metastatic multiple myeloma with an impending left S1 sacral fracture. Immediate posterior pelvic ring stabilization was recommended to prevent fracture and disruption of her oncologic recovery. This was performed percutaneously with computer-assisted navigation using a novel cannulated screw design.

CONCLUSION

The patient was treated with prophylactic percutaneous posterior pelvic ring fixation with a novel cannulated screw design that provided a durable construct for immediate weight-bearing. The fixation prevented a pathologic fracture and allowed immediate return to activity.

Modified unilateral iliac screw fixation with partial reduction in the treatment of high-grade spondylolisthesis at L5/S1 in adult patients: introduction of key technique, report of clinical outcomes and analysis of spinopelvic parameters

BACKGROUND

Management of high-grade spondylolisthesis (HGS) remains challenging. Spinopelvic fixation such as iliac screw (IS) was developed to deal with HGS. However concerns regarding constructs prominence and increased infection-related revision surgery have complicated it's use. We aim to introduce the modified iliac screw (IS) technique in treating high-grade L5/S1 spondylolisthesis and it's clinical and radiological outcomes.

METHODS

Patients with L5/S1 HGS who underwent modified IS fixation were enrolled. Pre- and postsurgical upright full spine radiographs were obtained to analyze sagittal imbalance, spinopelvic parameters, pelvic incidence-lumbar lordosis mismatch (PI-LL), slip percentage, slip angle (SA), and lumbosacral angle (LSA). Visual analogue scale (VAS), Oswestry disability index (ODI) were evaluated pre- and postoperatively for clinical outcomes assessment. Estimated blood loss, operating time, perioperative complications and revision surgery were documented.

RESULTS

From Jan 2018 to March 2020, 32 patients (15 males) with mean age of 58.66 ± 7.77 years were included. The mean follow-up period was 49 months. The mean operation duration was 171.67 ± 36.66 min. At the last follow-up: (1) the VAS and ODI score were significantly improved (p < 0.05), (2) PI increased by an average of 4.3°, the slip percent, SA and LSA were significantly improved (p < 0.05), (3) four patients (16.7%) with global sagittal imbalance recovered a good sagittal alignment, PI-LL within ± 10° was observed in all patients. One patient experienced wound infection. One patient underwent a revision surgery due to pseudoarthrosis at L5/S1.

CONCLUSION

The modified IS technique is safe and effective in treating L5/S1 HGS. Sparing use of offset connector could reduce hardware prominence, leading to lower wound infection rate and less revision surgery. The long-term clinical affection of increased PI value is unknown.

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.

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

Background: Posterior long spinal fusion was the common procedure for adult spinal deformity (ASD). Although the application of sacropelvic fixation (SPF), the incidence of pseudoarthrosis and implant failure is still high in long spinal fusion extending to lumbosacral junction (LSJ). To address these mechanical complications, advanced SPF technique by multiple pelvic screws or multirod construct has been recommended. This was the first study to compare the biomechanical performance of combining multiple pelvic screws and multirod construct to other advanced SPF constructs for the augmentation of LSJ in long spinal fusion surgery through finite element (FE) analysis.

Methods: An intact lumbopelvic FE model based on computed tomography images of a healthy adult male volunteer was constructed and validated. The intact model was modified to develop five instrumented models, all of which had bilateral pedicle screw (PS) fixation from L1 to S1 with posterior lumbar interbody fusion and different SPF constructs, including No-SPF, bilateral single S2-alar-iliac (S2AI) screw and single rod (SS-SR), bilateral multiple S2AI screws and single rod (MS-SR), bilateral single S2AI screw and multiple rods (SS-MR), and bilateral multiple S2AI screws and multiple rods (MS-MR). The range of motion (ROM) and stress on instrumentation, cages, sacrum, and S1 superior endplate (SEP) in flexion (FL), extension (EX), lateral bending (LB), and axial rotation (AR) were compared among models.

Results: Compared with intact model and No-SPF, the ROM of global lumbopelvis, LSJ, and sacroiliac joint (SIJ) was decreased in SS-SR, MS-SR, SS-MR, and MS-MR in all directions. Compared with SS-SR, the ROM of global lumbopelvis and LSJ of MS-SR, SS-MR, and MS-MR further decreased, while the ROM of SIJ was only decreased in MS-SR and MS-MR. The stress on instrumentation, cages, S1-SEP, and sacrum decreased in SS-SR, compared with no-SPF. Compared with SS-SR, the stress in EX and AR further decreased in SS-MR and MS-SR. The most significantly decreased ROM and stress were observed in MS-MR.

Conclusion: Both multiple pelvic screws and multirod construct could increase the mechanical stability of LSJ and reduce stress on instrumentation, cages, S1-SEP, and sacrum. The MS-MR construct was the most adequate to reduce the risk of lumbosacral pseudarthrosis, implant failure, and sacrum fracture. This study may provide surgeons with important evidence for the application of MS-MR construct in the clinical settings.

Sacropelvic fixation

The sacropelvis is not only an anatomically complex region but also a biomechanically unique zone transferring axial weights via the transitional lumbosacral junction and the pelvic girdle to the lower appendicular skeleton. When the sacral instrumentation alone is insufficient to achieve stability and solid arthrodesis across the lumbosacral junction, as in long-segment fusions, high-grade spondylolisthesis, deformity corrections, complex sacral/lumbosacral injuries, and neoplasms, sacropelvic fixation is indicated. Many modern sacropelvic fixation modalities outperform historical modalities, especially the conventionally open and percutaneous iliac and S2-alar-iliac screw (S2AI) fixation techniques. Novel screw insertion technologies such as navigation and robotics and modern screw designs aim to maximize the accuracy of screw placement and minimize complications. This review addresses the anatomy and biomechanics of the sacropelvic region as well as the indications, evolution, advantages, and disadvantages of various past and contemporary techniques of lumbosacral and sacropelvic fixation.

S2 alar-iliac screw versus traditional iliac screw for spinopelvic fixation: a systematic review of comparative biomechanical studies

PURPOSE

To review and compare biomechanical properties between S2 alar-iliac (S2AI) screws and traditional iliac screws for spinopelvic fixation.

METHODS

A systematic review was performed according to PRISMA guidelines. All clinical, cadaveric, and finite-element model (FEM) studies that compared the biomechanical properties between S2AI screws and traditional iliac screws were included. Study methodological quality for cadaveric studies were analyzed using the Quality Appraisal for Cadaveric Studies (QUACS) scale.

RESULTS

Eight studies (4 cadaveric, 4 FEM) analyzing 58 S2AI screws and 48 traditional iliac screws were included. According to QUACS, the overall methodological quality was "moderate to good" for all four cadaveric studies. All four cadaveric studies found no difference in biomechanical stiffness, screw toggle, rod strain, and/or load-to-failure between the S2AI screws and traditional iliac screws for spinopelvic fixation. All four FEM studies found that S2AI screws were associated with lower implant stresses compared to traditional iliac screws.

CONCLUSIONS

There is moderate biomechanical evidence to suggest that there is no significant difference in stability and stiffness between S2AI screws and traditional iliac screws for spinopelvic fixation. However, there is some evidence to support that the placement of S2AI screws may have lower implant stresses on the overall lumbosacral instrumentation compared to traditional iliac screws.

Clinical evaluation of S1 alar screws application in short-segment lumbosacral fixation and fusion for spine infection with severe S1 vertebral body loss

Background

The one-stage posterior approach for treating spinal infection has recently been generally accepted. However, severe vertebral body loss caused by infection remains a major challenge in posterior surgery. This study was conducted to evaluate the clinical application and outcomes of S1 alar screws used in the one-stage posterior surgery of short-segment lumbosacral fixation and fusion after debridement for infection with severe S1 vertebral body loss.

Methods

The clinical features and treatment outcomes of 7 patients with spinal infections from August 2016 to August 2021 who were treated with one-stage posterior surgery using S1 alar screws were retrospectively analyzed. The clinical data, including patient data, visual analogue scale (VAS), Oswestry Disability Index (ODI), fusion time and complications of the patients, were recorded.

Results

All 7 patients were followed up for an average duration of 14.57 months (range, 12—18 months). The VAS score decreased significantly from 7.3 preoperatively (range, 6—8) to 2.6 postoperatively (range, 2—3). The ODI score demonstrated a steady and gradual increase from 73.8 preoperatively (range, 68—75) to 33.6 postoperatively (range, 30—37). Bony fusion time was observed approximately 6.8 months after surgery. Two patients in our study experienced the postoperative local pain, which could be relieved by analgesics and disappeared 3 months after the operation. There were no complications of intraoperative fracture, posterior wound infection or neurovascular injury.

Conclusions

S1 alar screws are suitable for use in the operation and could be an alternative option to S1 pedicle screws for short-segment lumbosacral fixation and fusion with severe S1 vertebral body loss caused by spinal infection, which could provide satisfactory clinical outcomes.

Freehand S2-Alar-Iliac Screw Placement Technique in Lumbosacral Spinal Tumors: A Preliminary Study

OBJECTIVE

S2-alar-iliac (S2AI) screw technique is widely used in spinal surgery, but it is rarely seen in the field of spinal tumors. The aim of the study is to report the preliminary outcomes of the freehand S2AI screw fixation after lumbosaral tumor resection.

METHODS

The records of patients with lumbosacral tumor who underwent S2AI screw fixation between November 2016 to November 2020 at our center were reviewed retrospectively. Outcome measures included operative time, blood loss, complications, accuracy of screws, screw breach, and overall survival. Mean ± standard deviation or range was used to present continuous variables. Kaplan-Meier curve was used to present postoperative survival.

RESULTS

A total of 23 patients were identified in this study, including 12 males and 11 females, with an average age of 47.3 ± 14.5 (range,15-73). The mean operation time was 224.6 ± 54.1 (range, 155-370 min). The average estimated blood loss was 1560.9 ± 887.0 (600-4000 ml). A total of 46 S2AI screws were implanted by freehand technique. CT scans showed three (6.5%) screws had penetrated the iliac cortex, indicating 93.5% implantation accuracy rate. No complications of iatrogenic neurovascular or visceral structure were observed. The average follow-up time was 31.6 ± 15.3 months (range, 13-60 months). Two patients' postoperative plain radiography showed lucent zone around the screw. One patient underwent reoperation for wound delayed infection. At the latest follow-up, eight patients had tumor-free survival, 11 had survival with tumor, and four died of disease.

CONCLUSION

The freehand S2AI screw technique is reproducible, safe, and reliable in the management of lumbosacral spinal tumors.

Sacro-pelvic Anthropometry in the Portuguese Population and Its Implication for Screw Placement in Spinal Surgery: A Single Centre Retrospective Analysis

Objective  The aim of this study was to assess the sacropelvic anthropometry in the Portuguese population, through the study of pelvic computed tomography (CT) scans. Methods  Pelvic CT scans of 40 individuals were analyzed, and the length and angle measurements were performed according to predefined screw trajectories of S1 anterior (S1A), anterolateral (S1AL) and anteromedial (S1AM), S2 anterolateral (S2AL) and anteromedial (S2AM), S2 alar iliac (S2AI), iliac, and sacroiliac (SI) screws. Comparisons between genders were also performed. Results  The S1A screw trajectory mean length was 30.80 mm. The S1AL mean length and lateral angle were 36.48 mm and 33.13°, respectively, and the S1AM's were 46.23 mm and 33.21°. The S2AL mean length was 28.66 mm and lateral angle was 26.52°, and the S2AM length and angle were 29.99 mm and 33.61°, respectively. The S2 alar-iliac screw trajectory mean length, lateral, and caudal angles were 125.84 mm, 36.78°, and 28.66°, respectively. The iliac screw trajectory mean length, lateral, and caudal angles were 136.73 mm, 23,86° and 24.01°, respectively. The sacroiliac screw trajectory length was 75.50 mm. The length of the screws was longer in men than in women, except for the S1A and SI screws, for which no difference was found between genders. Conclusion  This study describes sacropelvic anatomical specifications. These defined morphometric details should be taken into consideration during surgical procedures.

Hardware Failure in Spinal Tumor Surgery: A Hallmark of Longer Survival?

Objective: Instrumentation failure in spine tumor surgery is a common reason for revision operation. Increases in patient survival demand a better understanding of the hardware longevity. The study objective was to investigate risk factors for instrumentation failure requiring revision surgery in patients with spinal tumors.Methods: A retrospective cohort from a single tertiary care specialty hospital from January 2005 to January 2021, for patients with spinal primary or metastatic tumors who underwent surgical intervention with instrumentation. Demographic and treatment data were collected and analyzed. Kaplan-Meier analysis was performed for overall survival, and separate univariate and multivariate regression analysis was performed.Results: Three hundred fifty-one patients underwent surgical intervention for spinal tumor, of which 23 experienced instrumentation failure requiring revision surgery (6.6%). Multivariate regression analysis identified pelvic fixation (odds ratio [OR], 10.9), spinal metastasis invasiveness index (OR, 1.11), and survival of greater than 5 years (OR, 3.6) as significant risk factors for hardware failure. One- and 5-year survival rates were 57% and 8%, respectively.Conclusion: Instrumentation failure after spinal tumor surgery is a common reason for revision surgery. Our study suggests that the use of pelvic fixation, invasiveness of the surgery, and survival greater than 5 years are independent risk factors for instrumentation failure.

Three-dimensional digital anatomical measurement of modified sacroiliac screws

Purpose

To rebuild a model of the pelvis and effectively simulate the trajectory of modified sacroiliac screws, we measured the parameters of each screw and screw channel and assessed the safety and feasibility of the parameters in adults.

Method and materials

One hundred (50 males and 50 females) normal adult pelvic computed tomography (CT) images were randomly selected and imported into Mimics software to rebuild the three-dimensional pelvis model. In these models, each ideal channel of modified screws was simulated, and then we obtained the precise parameters of screws and channels using Mimics and Three-matic software.

Results

The results of the comparison (right vs. left) showed that there were no significant differences in any of the angles, radius or M1SI parameters (the first modified sacroiliac). However, one parameter (BS) of M2SI (the second modified sacroiliac), two parameters (AP and BS) of M3SI (the third modified sacroiliac), and three parameters (AP, BS, L) of M4SI (the fourth modified sacroiliac) were statistically significant (P < 0.05). The result of comparison (between genders) showed that there were no significant differences in M1SI and M2SI; in contrast, the radius, length and the α angle of M3SI and M4SI were significantly different between genders (P < 0.05), and the radius of M4SI required special attention. If the radius of the limiting screw channel was > 3.50 mm, 52 cases (52%, 24 males and 28 females) could not complete the M4SI screw placement among 100 samples. If the radius of the limiting screw channel was > 3.0 mm, a total of 10 cases (10%, 2 males and 8 females) could not complete the M4SI screw placement.

Conclusion

Through the measurement of 100 healthy adult real three-dimensional pelvic models, we obtained the parameters of each modified sacroiliac screw and measured the three angles of each screw based on international coordinates for the first time, which can instruct clinical application.

Does Prior Lumbar Fusion Influence Dislocation Risk in Hip Arthroplasty Performed for Femoral Neck Fracture?

BACKGROUND

Immobility of the lumbar spine predicts instability following elective total hip arthroplasty (THA). The purpose of this study is to determine how prior lumbar fusion (LF) influenced dislocation rates and revision rates for patients undergoing THA or hemiarthroplasty (HA) for femoral neck fracture (FNF).

METHODS

A retrospective cohort analysis was conducted utilizing the PearlDiver database from 2010 to 2018. Patients who underwent arthroplasty for FNF were identified based on history of LF and whether they underwent THA or HA. Univariate and multivariate analyses were performed.

RESULTS

A total of 328 patients with prior LF and FNF who underwent THA were at increased risk for 1-year dislocation (odds ratio [OR] 2.19, P < .001) and 2-year revision (OR 2.22, P < .001) compared to 14,217 patients without LF. The 461 patients with prior LF and FNF who underwent HA were at increased risk for dislocation (OR 2.22, P < .001) compared to 42,327 patients without LF. Patients with prior LF and FNF who underwent THA had higher rates of revision than patients with prior LF who underwent HA for FNF (OR 2.11, P < .001). In patients with prior LF and FNF, THA was associated with significantly increased risk for dislocation (OR 3.07, P < .001) and revision (OR 2.53, P < .001) compared to THA performed for osteoarthritis.

CONCLUSION

Patients with prior LF who sustained an FNF and underwent THA or HA were at increased risk for early dislocation and revision compared to those without prior LF. This risk of dislocation and revision is even greater than that observed in patients with prior LF who underwent THA for osteoarthritis.

LEVEL OF EVIDENCE

Level III.

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

OBJECTIVE

There is no consensus regarding the best surgical strategy at the lumbosacral junction (LSJ) in long constructs for adult spinal deformity (ASD). The use of interbody fusion (IF) has been advocated to increase fusion rates, with additional pelvic fixation (PF) typically recommended. The actual benefit of IF even when extending to the pelvis, however, has not been vigorously analyzed. The goal of this work was to better understand the role of IF, specifically with respect to arthrodesis, when extending long constructs to the ilium.

METHODS

A systematic review of the PubMed and Cochrane databases was performed to identify the relevant studies in English, addressing the management of LSJ in long constructs (defined as ≥ 5 levels) in ASD. The search terms used were as follows: "Lumbosacral Junction," "Long Constructs," "Long Fusion to the Sacrum," "Sacropelvic Fixation," "Interbody Fusion," and "Iliac Screw." The authors excluded technical notes, case reports, literature reviews, and cadaveric studies; pediatric populations; pathologies different from ASD; studies not using conventional techniques; and studies focused only on alignment of different levels.

RESULTS

The PRISMA protocol was used. The authors found 12 retrospective clinical studies with a total of 1216 patients who were sorted into 3 different categories: group 1, using PF or not (n = 6); group 2, using PF with or without IF (n = 5); and group 3, from 1 study comparing anterior lumbar interbody fusion versus transforaminal lumbar interbody fusion. Five studies in group 1 and 4 in group 2 had pseudarthrosis rate as primary outcome and were selected for a quantitative analysis. Forest plots were used to display the risk ratio, and funnel plots were used to look at the risk of publication bias. The summary risk ratios were 0.36 (0.23-0.57, p < 0.001) and 1.03 (0.54-1.96, p = 0.94) for the PF and IF, respectively; there is a protective effect of overall pseudarthrosis for using PF in long constructs for ASD surgeries, but not for using IF.

CONCLUSIONS

The long-held contention that L5/S1 IF is always advantageous in long-construct deformity surgery is not supported by the current literature. Based on the findings from this systematic review and meta-analysis, PF with or without additional L5/S1 interbody grafting demonstrates similar overall construct pseudarthrosis rates. The added risk and costs associated with IF, therefore, should be more closely considered on a case-by-case basis.

Utilization of S1 Foraminal Hooks for Augmentation of S1 Screws in Adult Spinal Deformity Surgery: Comparative Study With Iliac Screws

OBJECTIVE

To compare the outcomes of S1 foraminal hooks and iliac screws regarding fusion rate at the lumbosacral junction and protective effects on S1 screws.

METHODS

From January 2017 to December 2019, consecutive patients who underwent long fusions (uppermost instrumented vertebra at or above L1) to the sacrum for adult spinal deformity were enrolled. Patients were divided into S1 foraminal hook group and iliac screw group. Radiographic parameters and the incidence of pseudarthrosis and instrument failure at the lumbosacral junction were compared between the groups.

RESULTS

Twenty-nine patients (male:female = 1:28) with a mean age of 73.6 ± 6.8 years were evaluated. Sixteen patients (55.2%) had S1 foraminal hook fixation and 13 patients (44.8%) had iliac screw fixation. Lumbar lordosis, sacral slope, and sagittal vertical axis did not differ between the groups preoperatively and postoperatively. The rate of L5/S1 pseudarthrosis was significantly higher in S1 foraminal hook group (5 of 16, 31.3%), compared to iliac screw group (0 of 13, 0%; p = 0.048). Instrument failure at the lumbosacral junction trended toward a higher rate in S1 foraminal hook group (6 of 16, 37.5%) than in iliac screw group (1 of 13, 7.7%), without statistical significance (p = 0.09). Proximal junctional kyphosis/failure occurred less often in S1 foraminal hook group (2 of 16, 12.5%) than in iliac screw group (3 of 13, 30.8%) without statistical significance (p = 0.36).

CONCLUSION

Treatment with S1 foraminal hooks achieved equivalent satisfactory sagittal correction with proportioned alignment compared to that with iliac screws. However, S1 foraminal hooks did not provide enough structural support to the lumbosacral junction in long fusions to the sacrum.

Ilio-sacral screw pelvic fixation when correcting spinal deformities with or without pelvic obliquity: our experience over 40 years

Ilio-sacral screw fixation for treatment of spinal deformities with pelvic obliquity was used from more than 40 years in our department of pediatric orthopedics. Despite trying all the other systems published in the literature, the authors came back to iliosacral screw to address the pelvic fixation. Keeping the same anatomical and biomechanical principles, with no damage of the SI joint, they improve the technology over time, to allow an easy use. The fear about the precise insertion necessary to prevent any root irritation is now greatly reduced thanks to the modern navigation. The history of the establishment and the advantages of this technique are explained based on more than 250 cumulative cases with an excellent correction of the pelvic obliquity, without any case of complete pull out of the ilio-sacral screw. A very low rate of nonunion thanks to the 3D adaptation of the balance in erect standing or sitting posture of the patient, thanks to the motion of the intact SI joint, and the small sagittal motion existing in the linkage screw/connector. All this comparing favorably to the other techniques published in the current literature.