Sacral and pelvic osteotomies for correction of spinal deformities

Spinopelvic Alignment: Importance in Spinal Pathologies and Realignment Strategies

Sagittal spinal malalignment can lead to pain, decreased function, dynamic imbalance, and compromise of patient-reported health status. The goal of reconstructive spine surgery is to restore spinal alignment parameters, and an understanding of appropriate patient-specific alignment is important for surgical planning and approaches. Radiographic spinopelvic parameters are strongly correlated with pain and function. The relationship between spinopelvic parameters and disability in adult spinal deformity patients is well-established, and optimal correction of sagittal alignment results in improved outcomes regarding patient health status and mechanical complications of surgery.

Irreducible L5/S1 Spondyloptosis in Over 20 Years After Neglected Trauma Treated with Modified Grob's Technique - Case Report

Introduction

Spondyloptosis, characterized by complete slippage of the upper vertebral body relative to the lower vertebral body, is an exceedingly rare condition. Typically, it occurs as a result of a high-energy injury and is promptly managed. It is uncommon for a patient to present to a spinal surgery unit several decades after the initial incident.

Case Report

In this case report, we describe the case of a 62-year-old man who experienced a lumbosacral injury from a fall twenty years prior to seeking treatment. The patient had multiple comorbidities, including obesity and internal medicine conditions. He presented with severe back pain radiating to the lower extremities, accompanied by significant neurogenic chroma and lower extremity weakness. Imaging studies revealed spondyloptosis at the L5/S1 level, along with bony fusion and spinal canal stenosis at the L3/L4 level.

Conclusion

The patient underwent surgical intervention using Grob's direct pediculo-body fixation technique. The postoperative period was uneventful, and over the course of one year of follow-up, the patient experienced a resolution of symptoms and significant improvement in functional capacity.

Sacral osteotomy combined with triangular osteosynthesis in the treatment of malunion and nonunion of vertically displaced pelvic fractures

Background

Malunion and nonunion of vertically displaced pelvic fractures result in lower limb length discrepancies, claudication, and pain. There have been few previous reports of this type of corrective surgery for these old pelvic fractures. We present a surgical technique of sacral osteotomy combined with triangular osteosynthesis in the treatment of malunion and nonunion of vertically displaced pelvic fractures and report on its short-term clinical results.

Methods

We retrospectively reviewed nine patients (five males and four females) with malunion or nonunion of vertically displaced pelvic fractures treated with sacral osteotomy and triangular osteosynthesis from April 2015 to January 2020. The age ranged from 14 to 45 years (average, 30.7 years). The time from injury to deformity correction surgery ranged from 3 months to 5 years (average, 12.8 months). The vertical displacement of a unilateral hemipelvis was 3.0–4.5 cm (average, 3.80 cm). According to AO/OTA classification at the initial fracture, there are eight cases in type C1.3 and one case in type C3.3. Sacral osteotomy and triangular osteosynthesis were used in all nine patients. The degree of unilateral hemipelvic reduction was assessed postoperatively based on measurements from the anteroposterior (AP) X-ray. Majeed score and pain visual analog scale (VAS) were used to assess the therapeutic effect of the patients during follow-up.

Results

In all nine patients, postoperative AP X-ray showed correction displacement of 1.7–3.9 cm (average, 3.20 cm). All the patients were followed up for 6–36 months (average, 12.7 months). At the last follow-up, the Majeed score of pelvic fracture increased from an average of 53.9 points (30–84 points) preoperatively to 87.0 points (72–94 points), and the VAS score for pain decreased from an average of 6.0 points (4–8 points) preoperatively to 1.2 points (0–3 points). None had complications like infection, implant broken, screw loosening, iatrogenic nerve, and blood vessel injury.

Conclusion

Sacral osteotomy combined with triangular osteosynthesis for the treatment of pelvic malunion and nonunion caused by sacral fractures can correct significantly vertical displacement of a unilateral pelvis, prolong limb length, and reconstruct the stability of a pelvic ring, achieving good clinical results.

Sacral Pedicle Subtraction Osteotomy for Treatment of High-Grade Spondylolisthesis: A Technical Note and Review of the Literature

BACKGROUND

Lumbosacral deformities are caused by high-grade spondylolisthesis, fractures, iatrogenic flat back, and other etiologies. The S1 pedicle subtraction osteotomy (PSO) can facilitate reduction of spondylolisthesis and lower the pelvic incidence. There are limited reports on the indications and outcomes of this technique.

OBJECTIVE

To present a technical description and literature review of the S1 PSO with video summary.

METHODS

This was a retrospective review of a single case to highlight the use of S1 PSO for the treatment of high-grade spondylolisthesis. A literature review was performed in accordance with STROBE guidelines.

RESULTS

A 47-year-old woman presented with back and right leg pain related to grade 4 spondylolisthesis at L5-S1 with sagittal imbalance and lumbosacral kyphosis. She was taken for an L2-pelvis instrumented fusion with S1 PSO. Three days later, she was taken for an L4-5 and L5-S1 anterior lumbar interbody fusion with the L5-S1 segmental plate. Her postoperative course was notable for right foot drop that resolved in 6 weeks. Postoperative x-rays showed successful reduction of spondylolisthesis with normal alignment and sagittal balance. Based on 6 studies involving 22 true sacral PSOs in the literature, the procedure carries a 27% risk of neurological deficit, typically in the form of L5 palsy.

CONCLUSION

The S1 PSO is a technically challenging operation that has a unique role in the treatment of high-grade spondylolisthesis. It carries a significant risk of L5 palsy and should be reserved for surgeons with experience performing complex 3-column osteotomies.

Correction of the pelvic incidence using a bilateral extending pelvic osteotomy: a proof of concept study

INTRODUCTION

The aim of this proof of concept human cadaver study was to quantify the effect of a bilateral extending pelvic osteotomy (BEPO) on pelvic incidence (PI) as a potential alternative for a pedicle subtraction osteotomy (PSO) in patients with severe spinal sagittal malalignment.

MATERIALS AND METHODS

10 fresh frozen human cadavers were treated with the BEPO technique. CT images were made before and after the osteotomy and pure sagittal images were created on which PI was measured.

RESULTS

The mean pre-osteotomy PI was 47.9° (range 36.4-63.9) and the mean post-osteotomy PI was 36.5° (range 22.1-54.4). The mean correction was - 10.4° with a range of - 8.4° to - 17.3° (p = 0.03), which resulted in a mean decrease of 23% in the PI (range 16-42).

CONCLUSIONS

There was a feasible and effective correction of PI using the BEPO technique on the os ilium. This was a preliminary cadaveric study. No conclusions could be made on global sagittal alignment. We postulate that an extending osteotomy of the ilium could be a potential alternative for a PSO reducing the complexity of spine surgery in patients with severe spinal sagittal malalignment.

On the pedicle subtraction osteotomy technique and its modifications during the past two decades: a complementary classification to the Schwab's spinal osteotomy classification

PURPOSE

To propose a complementary classification to the Schwab's osteotomy classification that would regroup together under a common umbrella different published pedicle subtraction osteotomy (PSO) variations that are commonly used, to have a common language and complete the spine surgeon's armamentarium when dealing with rigid spinal deformities.

METHODS

The 2 general types corresponding to the grades 3 and 4 of the Schwab classification were separated into 6 gradual subtypes (grades 3A, 3B, 3C, 4A, 4B, 4C). The classification is based on the amount of resected pedicle, the inclusion or not of the disc above, and the location of the axis of rotation. Based on the proposed classification, a reliability study was performed using 18 cases that were classified by 8 readers with expertise in the management of adult deformities with the use of osteotomies.

RESULTS

Clinical cases were classified according to the 6 grades proposed in the classification. The intra-rater reliability for the classification was "almost perfect agreement" with a Fleiss kappa coefficient average of 0.92 (range 0.85-1.00). The inter-rater reliability was "almost perfect agreement" with a coefficient average of 0.90 for the 2 readings that were done at an interval of 2 weeks.

CONCLUSION

The developed classification proved to be reliable and intuitive. It is an original way to display a catalog of different available PSO modifications including the original technique, in a logical and gradual order to help the surgeons in their decisions and show them that between a grade 2 osteotomy and a grade 5 osteotomy, many intermediate options are available. Further work with a treatment algorithm for clinical practice based on the current classification may be developed in the future.

Lumbosacral osteotomy to correct PI-LL mismatch in the presence of abnormally high pelvic incidence

STUDY DESIGN

A case report. It is important to achieve optimal sagittal balance in spinal deformity surgery by matching LL to PI. A Lumbar osteotomy to increase lordosis is often the method used to achieve this in adult patients. However, in patients with high PI with compensatory lumbar hyperlordosis, providing further lordosis does not address the root cause. The paper will describe a technique of lumbosacral osteotomy to address sagittal malalignment with associated coronal imbalance and pelvic incidence (PI)-lumbar lordosis (LL) mismatch.

METHODS

A 16-year-old female patient presented with low back pain and right leg pain. Standing anteroposterior X-ray showed scoliosis with a Cobb angle of 34º and 5.7 cm of coronal imbalance. Lateral X-ray showed a sacralized L5 with a PI of 85º and LL of 47º. Pedicle subtraction osteotomy through the sacralized L5 addressed the malalignment secondary to a high PI-LL mismatch of 38º.

RESULTS

Following alar resection, an osteotomy was performed below the L5 pedicles. The cranial parts including the superior endplate and intervertebral disc were removed. Osteotomy closure was achieved using the central rod technique. L5 incidence was reduced from 59º to 33º with reduced coronal malalignment. Back pain was significantly improved and PI-LL mismatch was improved to 10º two years post-operatively with no local loss of sagittal correction.

CONCLUSIONS

A lumbosacral osteotomy at the lumbosacral junction is useful to improve high PI - LL mismatch in patients with abnormally high PI with compensatory lumbar hyperlordosis.

Pelvic incidence: A study of a spinopelvic parameter in MRI evaluation of pelvic organ prolapse

PURPOSE

This study aims to compare pelvic incidence (PI), a skeletal angle formed by the first sacral vertebrae and femoral heads, in women with and without pelvic organ prolapse (POP) and to explore the correlation of PI with the progression of POP, through 3D reconstruction of MRI scans.

METHOD

The case-control study enrolled 48 prolapse patients and 48 paired subjects by collecting and screening clinical information including age, BMI, vaginal deliveries, and levator ani defect scores. PI values were measured in 3D reconstruction models based on MRI scans, and the mean and standard deviation values of PI in both groups were calculated. Receiver operating characteristic (ROC) analysis and logistic regression were used to quantify relationships between PI and prolapse. Additionally, by performing a cross-section study of 69 patients with POP, correlations between PI values and descending vaginal locations were assessed by multivariate linear regression models.

RESULTS

Compared with the control group, the patient group has a significantly larger average PI (48.68 ± 10.77˚ vs 42.20 ± 8.55˚, P=0.002). ROC analysis for the classification of prolapse based on PI has an area under the curve of 70.1 % (P < 0.001). Logistic regression identified a larger PI value as a risk factor of prolapse with an odds ratio of 2.90 (95 %CI: 1.46-5.74, P = 0.002) for PI per increasing 10˚. Point Ba and Bp represent the most distal positions of any part of the upper anterior and posterior vaginal walls, respectively. In the patient group, internally, Ba and Bp would descend 0.62 (95 %CI: 0.24-1.00, P=0.002) cm and 0.74 (95 %CI 0.22-1.26, P=0.006) cm for every 10° increase in PI, respectively. The coefficients of the partial correlation of PI for Ba and Bp are 0.381 (P = 0.002) and 0.336 (P = 0.006).

CONCLUSIONS

PI is significantly related to morbidity and progression of POP, especially for the anterior and posterior pelvic compartments. As an individual constant value of the spinopelvic skeletal shape, a larger PI value is a risk factor and should be evaluated carefully in medical imaging of POP.

Sacrum osteotomy to change pelvic parameters: Surgical technique and 3D modeling

PURPOSE

Some clinical situations, such as great sagittal imbalance, high-grade isthmic spondylolisthesis or sacral malunion could require a sacral osteotomy to decrease pelvic parameters, horizontalize the sacrum or correct sacral malunion. Here is described a novel technique to perform a sacral osteotomy to decrease pelvic parameters with a lumbo-pelvic construct, with first a sacral slope decrease, then a pelvic tilt decrease.

METHODS

Simulations have been performed using tridimensional reconstructions of the lumbar spine and pelvis, made from CT-scan images of a healthy individual. A cadaveric study has then been performed.

RESULTS

3D modeling exhibited linear relationship between osteotomy angle and pelvic incidence correction, through multiple simulations with 1° increment. Cadaveric study demonstrated feasibility.

CONCLUSION

This preliminary work shows that this technique is efficient to decrease pelvic parameters. A linear relationship has been exhibited between osteotomy angle and PI decrease, as per the following formula: osteotomy angle=PI change/0.84.

Complication profile associated with S1 pedicle subtraction osteotomy compared with 3-column osteotomies at other thoracolumbar levels for adult spinal deformity: series of 405 patients with 9 S1 osteotomies

OBJECTIVE

There is an increased recognition of disproportional lumbar lordosis (LL) and artificially high pelvic incidence (PI) as a cause for positive sagittal imbalance and spinal pelvic mismatch. For such cases, a sacral pedicle subtraction osteotomy (PSO) may be indicated, although its morbidity is not well described. In this study, the authors evaluate the specific complication risks associated with S1 PSO.

METHODS

A retrospective review of all adult spinal deformity patients who underwent a 3-column osteotomy (3CO) for thoracolumbar deformity from 2006 to 2019 was performed. Demographic, clinical baseline, and radiographic parameters were recorded. The primary outcome of interest was perioperative complications (surgical, neurological, and medical). Secondary outcomes of interest included case length, blood loss, and length of stay. Multivariate analysis was used to assess the risk of S1 PSO compared with 3CO at other levels.

RESULTS

A total of 405 patients underwent 3CO in the following locations: thoracic (n = 55), L1 (n = 25), L2 (n = 29), L3 (n = 141), L4 (n = 129), L5 (n = 17), and S1 (n = 9). After S1 PSO, there were significant improvements in the sagittal vertical axis (14.8 cm vs 6.7 cm, p = 0.004) and PI-LL mismatch (31.7° vs 9.6°, p = 0.025) due to decreased PI (80.3° vs 65.9°, p = 0.006). LL remained unchanged (48.7° vs 57.8°, p = 0.360). The overall complication rate was 27.4%; the surgical, neurological, and medical complication rates were 7.7%, 6.2%, and 20.0%, respectively. S1 PSO was associated with significantly higher rates of overall complications: thoracic (29.1%), L1 (32.0%), L2 (31.0%), L3 (19.9%), L4 (32.6%), L5 (11.8%), and S1 (66.7%) (p = 0.018). Similarly, an S1 PSO was associated with significantly higher rates of surgical (thoracic [9.1%], L1 [4.0%], L2 [6.9%], L3 [5.7%], L4 [10.9%], L5 [5.9%], and S1 [44.4%], p = 0.006) and neurological (thoracic [9.1%], L1 [0.0%], L2 [6.9%], L3 [2.8%], L4 [7.0%], L5 [5.9%], and S1 [44.4%], p < 0.001) complications. On multivariate analysis, S1 PSO was independently associated with higher odds of overall (OR 7.93, p = 0.013), surgical (OR 20.66, p = 0.010), and neurological (OR 14.75, p = 0.007) complications.

CONCLUSIONS

S1 PSO is a powerful technique for correction of rigid sagittal imbalance due to an artificially elevated PI in patients with rigid high-grade spondylolisthesis and chronic sacral fractures. However, the technique and intraoperative corrective maneuvers are challenging and associated with high surgical and neurological complications. Additional investigations into the learning curve associated with S1 PSO and complication prevention are needed.

Importance of Spinal Alignment in Primary and Metastatic Spine Tumors

Spinal alignment, particularly with respect to spinopelvic parameters, is highly correlated with morbidity and health-related quality-of-life outcomes. Although the importance of spinal alignment has been emphasized in the deformity literature, spinopelvic parameters have not been considered in the context of spine oncology. Because the aim of oncologic spine surgery is mostly palliative, consideration of spinopelvic parameters could improve postoperative outcomes in both the primary and metastatic tumor population by taking overall vertebral stability into account. This review highlights the relevance of focal and global spinal alignment, particularly related to spinopelvic parameters, in the treatment of spine tumors.

The Use of Sacral Osteotomy in the Correction of Spinal Deformity: Technical Report and Systematic Review of the Literature

BACKGROUND

Flat back deformity is a disabling adverse outcome following instrumented lumbar fusion. As patients are often fused in this non-physiologic alignment, correction is complex and has conventionally required fracture of the preexisting fusion mass. Sacral osteotomy may be one effective means of correcting the positive sagittal balance in these patients. Here we report a case of flat back deformity corrected using a 3-column sacral osteotomy, and systematically review the available literature on the effectiveness of 3-column sacral osteotomy for correcting flat back deformity.

METHODS

A systematic review was performed using the results of a search of the PubMed, EMBASE, Web of Science, and Cochrane databases according to PRISMA guidelines. We also include our patient as an example of the technique.

RESULTS

Eight studies-all case reports or small case series-were identified describing 37 patients, including our case example. The variety of techniques was too heterogeneous for meta-analysis, but all studies reported good correction of sagittal deformity. Transient L5 palsy was the most common side effect of this technique, being reported in 21 patients (56.8%) across all studies.

CONCLUSIONS

Sacral osteotomy is potentially an effective means of correcting positive sagittal balance in patients with flat back deformity secondary to high pelvic incidence.

Dual iliac screws in spinopelvic fixation: a systematic review

PURPOSE

The classical spinopelvic fixation includes 1 iliac screw on each side. The purpose of this study is to specify the indications of the "dual iliac screw" (DIS) construct, i.e., when to put 2 iliac screws on each side, to describe its biomechanical advantages, and to define its related technical aspects.

METHODS

A primary search on Medline through PubMed distribution was performed, with the use of the terms "pelvic fixation" or "spinopelvic" or "lumbo-iliac" and the terms "dual iliac screw" or "double iliac screw." English papers corresponding to the inclusion criteria were analyzed regarding the specific indications of the DIS construct and its surgical technique and advantages.

RESULTS

Eleven papers were identified according to the research criteria and included in this review. Three main indications were identified for the DIS technique according to three types of pathologies: in adult deformities when a long construct is needed in an osteoporotic patient or when correction requires three-column osteotomy of the sacrum; in trauma when a U-shaped fracture-dislocation of the sacrum is involved; in sacral tumors when a sacrectomy is performed or when destructive metastatic lesions of the sacrum require palliative surgical treatment. Biomechanically, the DIS technique proved to have higher construct stiffness in terms of compression and torsion.

CONCLUSION

In specific cases, affecting different areas of spinal diseases, the DIS technique is more advantageous, when compared to the "single iliac screw" version, as it would provide a stronger and safer fixation at the base of the spinopelvic construct. These slides can be retrieved under Electronic Supplementary Material.

The Clinical Significance of L5 Incidence in Patients with High Pelvic Incidence: A Case Report

Objective: To present a case of sagittal malalignment with high pelvic incidence and its surgical management. Summary of Background Data: Though rare, patients with high pelvic incidence (PI) around 90° without spondylolisthesis or spondylolysis often show sagittal malalignment with low back pain. However, little has been reported about the treatment of such cases. Methods: We report a case of a 15-year-old female complaining of severe difficulty in maintaining an upright position and gait disturbance due to back pain. Radiographs showed high PI of 88° and L5 incidence (L5I) of 67° combined with hyperlordosis of lumbar segments. A lower Lordosis Distribution Index (LDI; percentage of lordosis on segments L4–S1 in entire lumbar lordosis of L1-S1) was detected despite the high overall lumbar lordosis. The patient was surgically treated by two-stage combined posterior and anterior short fusion from the sacrum. Results: The surgical strategy was planned with attention to L5I instead of PI. L5I decreased to 49° and sagittal alignment of the whole spine—including cervical, thoracic, and lumbar spine—improved without any complications. Activity of daily living (ADL）improved preoperatively with relief of low back pain. Conclusions: Improvement of L5I by performing short fusion from L4 to S1 may be a strategy for patients with high PI complaining of low back pain due to sagittal malalignment.

Predicting the Effect of Bilateral Pelvic Osteotomy on Sagittal Alignment Correction and Surrounding Muscles: A Mathematical Model

Study Design. Mathematical Model. Objectives. To investigate the relationship between pelvic osteotomy opening angle (OA) and its effect on spinopelvic sagittal parameters as well as the resting length of surrounding muscles. Methods. Predictive equations correlating OA with spinopelvic parameters were derived using geometric relationships. A geometric model calculated spinopelvic parameters (SVA, pelvic incidence [PI], PT, and T1 pelvic angle [TPA]) produced by progressively increasing the OA. These values were compared to optimal balance criteria in the literature. Four muscles crossing the osteotomy site were evaluated: Gluteus Medius (GMED), Gluteus Maximus (GMAX), Piriformis (P), and Tensor Fascia Lata (TFL). Insertion points were obtained from an OpenSim software model. GMAX and GMED were subdivided into 3 (anterior, middle, and posterior). Results. OA correlated negatively with PI, TPA, and SVA and positively with PT. From baseline SVA of 22 cm, OA 21° reduced SVA to 5cm. OA 23° reduced TPA to 14°. OA 30° increased PT to 20°. OA 26° decreased PI-LL to 10°. OA range of 26°-30° resulted in optimal sagittal deformity correction. OA correlated with SR positively for TFL and anterior GMED and negatively for the rest of muscles. For this OA, the SR approximately decreased 6%, 5%, 6%, 8%, and 5% for posterior GMED, anterior GMAX, middle GMAX, posterior GMAX, and P, respectively. It increased 8% and 4% for anterior GMED and TFL, respectively. Conclusion. Predictive relationships between osteotomy OA and spinopelvic parameters were shown, providing proof of concept that sagittal balance may be achieved via pelvic osteotomy.

Pelvic incidence measurement using a computed tomography data-based three-dimensional pelvic model

Objectives

To introduce a new method of pelvic incidence (PI) measurement based on three-dimensional (3D) pelvic models reconstructed from CT images and to report the normal distribution of PI in normal pelvic anatomy.

Methods

CT images of 320 subjects with normal pelvic anatomy who visited the Radiology Department between 2006 and 2017 were retrospectively selected and saved in Digital Imaging and Communications in Medicine (DICOM) format. A computerized method was employed to determine the bony landmarks required for the measurement of PI. To quantify the method’s accuracy and reliability, the intraclass correlation coefficient (ICC) was calculated. A subgroup of 30 DICOM files was randomly selected to perform a validation study. Three independent testers performed all procedures. All measurements were performed twice independently by the three testers on all 10 subjects with an interval of 2 weeks. Independent samples t tests were used to identify statistically significant differences in the PI value between sexes. Pearson correlation coefficient was employed to determine the relationship between PI and age.

Results

PI measurement using the new method resulted in an excellent intraobserver reliability (0.9612, range 0.8917–0.9893; p < 0.001) and interobserver reliability (0.9867, range 0.9611–0.9964; p < 0.001). PI was significantly different between sexes, with larger PI in women (p = 0.019). PI was significantly larger in the 40–80-year age group (45.94 ± 9.08°) than the < 40-year age group (43.50 ± 7.39°). We did not find any linear correlation between PI and age in the male (r = 0.140, p = 0.105) or female subgroup (r = 0.119, p = 0.107). A weak correlation between PI and age overall was observed (r = 0.142, p = 0.011).

Conclusion

Accurate PI measurement could be achieved by a CT data-based 3D pelvic model.

Sacral pedicle subtraction osteotomy for an extreme case of positive sagittal balance: case report

The importance of sagittal spinal balance and lumbopelvic parameters is now well understood. The popularization of various osteotomies, including Smith-Peterson, Ponte, and pedicle subtraction osteotomies (PSOs), as well as vertebral column resections, have greatly enhanced the spine surgeon's ability to recognize and effectively treat sagittal imbalance. Yet rare circumstances remain, most notably in distal kyphotic deformities and patients with extremely elevated pelvic incidences, where these techniques remain inadequate. In this article, the authors describe a patient with severe sagittal imbalance despite multiple prior anterior and posterior reconstructive surgeries in which a sacral PSO was performed with good results. A description of this technique as well as a brief review of the literature is provided.

New method for correction of lumbo-sacral kyphosis deformity in patient with high pelvic incidence

STUDY DESIGN

Technical note.

OBJECTIVE

We describe a novel technique of bilateral longitudinal sacral osteotomy allowing direct reduction of high pelvic incidence (PI) and correction of sagittal imbalance.

METHODS

A 25-year-old female patient presented with a disabling lumbo-sacral kyphosis fused in situ through previous operations with residual low-grade wound infection and grade IV L5/S1 spondylolisthesis with severity index (SI) of 65%. A two-stage correction was performed. First anterior in situ fixation of the L4-L5-S1 segments was performed using a hollow modular anchorages (HMA) screw and L3/L4 anterior interbody cage. The second stage consisted of instrumentation of the lower lumbar spine and pelvis; placement of an S1 transverse K-wire as pivot point and bilateral longitudinal sacral osteotomy which allowed for gradual retroversion of the central sacrum relative to the pelvis.

RESULTS

Sacrum was derotated by 30° which allowed to restore spinal sagittal balance and decrease SI by 15%. Postoperative recovery was complicated by a flare up of the pre-existing deep wound infection.

CONCLUSIONS

Bilateral longitudinal sacral osteotomy appears to be a safe and efficient way of correcting the sagittal imbalance caused by an extremely high PI. Although technically demanding, it achieves good radiological and functional outcomes and avoids entering the spinal canal.

Increased and decreased pelvic incidence, sagittal facet joint orientations are associated with lumbar spine osteoarthritis in a large cadaveric collection

PURPOSE

Degenerative joint disease of the lumbar spine is a pervasive problem in healthcare; however, its aetiology and risk factors remain poorly defined. There have been recent attempts to correlate the anatomic parameters of facet angle and pelvic incidence with spine osteoarthritis, although data remains limited. The purpose of this experiment was to determine how age, gender, race, facet angle, tropism, and pelvic incidence correlate to facet joint osteoarthritis in the lumbar spine.

METHODS

A total of 576 cadaveric lumbar spines were obtained. Using validated techniques, facet angle, tropism, and pelvic incidence were measured. Osteoarthritis of the lumbar spines was graded from 0-4 at each level. Correlations between osteoarthritis and age, gender, facet angle, tropism, and pelvic incidence were evaluated with regression analysis.

RESULTS

Facet angle became more coronally oriented, and facet tropism increased from L1-L2 to L5-S1. Arthritis was highest at the L4-L5 joint (2.2 ± 1.1), compared to the L5-S1 (2.1 ± 1.1), L3-L4 (1.9 ± 1.1), L2-L3 (1.5 ± 1.0) and L1-L2 (1.0 ± 1.0) joints (p < 0.001). Age was the strongest predictor of arthritis at all levels (standardized betas 0.342 through 0.494, p < 0.001). Correlations between gender, race and osteoarthritis were not significant at any level. A decreased facet angle was predictive of increased arthritis at each joint level (standardized betas -0.091 through -0.153, p < 0.05 for all). Tropism was a predictor of increased arthritis at caudal levels. Pelvic incidence was a predictor of increased arthritis at L3-L4 (standardized beta 0.080, p = 0.02), L4-L5 (standardized beta 0.081,p = 0.02), and L5-S1 (standardized beta 0.100, p = 0.01).

CONCLUSIONS

Facet arthritis was correlated with a more sagittal orientation of the facet joints, increased tropism, and perturbations of pelvic incidence.

The Relationship between T1 Sagittal Angle and Sagittal Balance: A Retrospective Study of 119 Healthy Volunteers

T1 sagittal angle has been reported to be used as a parameter for assessing sagittal balance and cervical lordosis. However, no study has been performed to explore the relationship between T1 sagittal angle and sagittal balance, and whether T1 sagittal angle could be used for osteotomy guidelines remains unknown. The aim of our study is to explore the relationship between T1 sagittal angle and sagittal balance, determine the predictors for T1 sagittal angle, and determine whether T1 sagittal angle could be used for osteotomy guidelines to restore sagittal balance. Medical records of healthy volunteers in our outpatient clinic from January 2014 to August 2015 were reviewed, and their standing full-spine lateral radiographs were evaluated. Demographic and radiological parameters were collected and analyzed, including age, gender, T1 sagittal angle, maxTK, maxLL, SS, PT, and PI. Correlation coefficients between T1 sagittal angle and other spinopelvic parameters were determined. In addition, multiple regression analysis was performed to establish predictive radiographic parameters for T1 sagittal angle as the primary contributors. A total of 119 healthy volunteers were recruited in our study with a mean age of 34.7 years. It was found that T1 sagittal angle was correlated with maxTK with very good significance (r = 0.697, P<0.001), maxLL with weak significance (r = 0.206, P = 0.024), SS with weak significance (r = 0.237, P = 0.009), PI with very weak significance (r = 0.189, P = 0.039), SVA with moderate significance (r = 0.445, P<0.001), TPA with weak significance (r = 0.207, P = 0.023), and T1SPI with weak significance (r = 0.309, P = 0.001). The result of multiple regression analysis showed that T1 sagittal angle could be predicted by using the following regression equation: T1 sagittal angle = 0.6 * maxTK—0.2 * maxLL + 8. In the healthy population, T1 sagittal angle could be considered as a useful parameter for sagittal balance; however, it could not be thoroughly replaced for SVA. maxTK was the primary contributor to T1 sagittal angle. According to this equation, we could restore sagittal balance by surgically changing thoracic kyphosis and lumbar lordosis, which could serve as a guideline for osteotomy.

Sacral Alar Iliac Fixation for Spine Deformity

INTRODUCTION

As the anatomy of the lumbosacral junction presents a unique challenge for the spine surgeon with regard to achieving a solid fusion, we describe the sacral alar iliac (SAI) technique, which can be used for the placement of pelvic anchors during posterior spinal arthrodesis.

INDICATIONS & CONTRAINDICATIONS

STEP 1 PATIENT POSITIONING

Position the patient prone on a radiolucent table.

STEP 2 SURGICAL APPROACH

In approaching the starting point, perform limited dissection of the soft tissue between the S1 and S2 dorsal foramina, while taking care to minimize unnecessary dissection and blood loss.

STEP 3 CHANNEL CREATION

As the ideal screw pathway is one-third in the sacral ala and two-thirds in the ilium, start at the junction between the 1st and 2nd sacral segments, cross the sacroiliac joint, travel caudally toward the sciatic notch, cross between the inner and outer table of the ilium, and end close to the anterior inferior iliac spine cranial to the acetabular roof (Figs. 5-A and 5-B).

STEP 4 SCREW PLACEMENT

In most children and adults, use screws with an outer diameter ≥9 mm, which are recommended to prevent screw breakage.

STEP 5 ROD PLACEMENT

Ensure that the SAI screws are in line with the remainder of the spinal anchors to allow for ease of rod insertion.

STEP 6 WOUND CLOSURE

Perform carefully layered wound closure per routine at the end of the case, with special attention to meticulous hemostasis.

RESULTS

In a review of the cases of 32 pediatric patients treated with SAI fixation, Sponseller et al.27 reported a mean pelvic obliquity correction of 70% and a mean major coronal Cobb angle correction of 67%.

PITFALLS & CHALLENGES