Correction of pelvic obliquity in neuromuscular spinal deformities using the "T construct": results and complications in a prospective series of 60 patients

Pelvic Fixation Technique Using the Ilio-Sacral Screw for 173 Neuromuscular Scoliosis Patients

Pelvic fixation remains one of the main challenging issues in non-ambulatory neuromuscular scoliosis (NMS) patients, between clinical effectiveness and a high complication rate. The objective of this multicenter and retrospective study was to evaluate the outcomes of a technique that was applied to treat 173 NMS patients. The technique is not well-known but promising; it uses the ilio-sacral screw, combined with either the posterior spinal fusion or fusionless bipolar technique, with a minimum follow-up of two years. The mean operative age of the patients was 13 ± 7 years. The mean preoperative main coronal curve was 64° and improved by a mean of -39° postoperatively. The mean preoperative pelvic obliquity was 23°, which improved by a mean of -14° postoperatively. No decrease in the frontal or sagittal correction was observed during the last follow-up. The sitting posture improved in all cases. Twenty-nine patients (17%) had a postoperative infection: twenty-six were treated with local debridement and antibiotics, and three required hardware removal. Fourteen mechanical complications (8%) occurred: screw malposition (n = 6), skin prominence (n = 1), and connector failure (n = 1). This type of surgery is associated with a high risk for infection. Comorbidities, rather than the surgery itself, were the main risk factors that led to complications. The ilio-sacral screw was reliable and effective in correcting pelvic obliquity in NMS patients. The introduction of intraoperative navigation should minimize the risk of screw misplacement and facilitate revision or primary fixation.

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.

The Utilization of Dual Second Sacral Alar-Iliac Screws for Spinopelvic Fixation in Patients with Severe Kyphoscoliosis

OBJECTIVES

As a new pelvic fixation technique, the dual S2AI screws fixation technique could provide highly stable distal strength, and have wide clinical prospect in the correction of severe kyphoscoliosis. However, the ideal trajectory parameters, indications and clinical outcomes of this technique have not been reported so far. This study aimed to determine the anatomical parameters of dual S2AI screws in the normal Chinese adult population, investigating the indications of this technique and evaluating the feasibility and clinical outcomes.

METHODS

Fifteen males and 15 females with normal pelvis underwent a pelvic CT scan to determine ideal dual S2AI screws trajectories. Sagittal angle (SA), transverse angle (TA), maximal length (ML), sacral length, and skin distance were measured. Subsequently, we retrospectively reviewed the data of 16 patients (seven males and nine females) who underwent dual S2AI screw fixation and 23 patients who underwent single S2AI screw fixation between January 2014 and December 2019. Preoperative, postoperative, and latest follow-up measurements of Cobb angle, coronal balance (CB), spinal pelvic obliquity (SPO), and regional kyphosis (RK) were obtained. The mean follow-up time was 16.7 ± 7.1 months (range: 12-30 months). Independent t-test was used to determine the difference in the analysis of the trajectories. The paired sample non-parametric Wilcoxon test was performed to assess the changes in radiographic parameters between different time points and different groups.

RESULTS

For both male and females, the proximal S2AI screws had significantly higher TA and ML, but a lower SA than distal screws. Females showed significantly more caudal (SA: 25.03° ± 2.32° vs. 29.82° ± 2.47°, t = 7.742, P < 0.001) trajectories of distal screw. Additionally, ML in the females were significantly shorter than that in males (106.81 mm ± 6.79 mm vs. 101.63 mm ± 6.55 mm, t = 3.007, P = 0.003, 124.41 mm ± 7.57 mm vs. 116.23 mm ± 7.03 mm, t = 4.337, P < 0.001). Eight had unilateral and eight had bilateral dual S2AI screw placement. Respectively, both the single S2AI and dual S2AI groups showed significant postoperative improvement of Cobb angle, RK angle and SPO angle. In patients with dual S2AI screws fixation, two patients found that screws loosening occurred in one of dual screws at 1-year follow-up, and in patients with single S2AI screws fixation, six patients found screw loosing as well as two patients found screw breakage at 1-year follow-up. None of all patients had any prominent loss of correction.

CONCLUSION

The ideal trajectory of dual S2AI screw could be well established. The dual S2AI screw fixation technique is feasible in patients with severe kyphoscoliosis, and provides satisfactory correction of deformity with few postoperative complications.

Ambulatory capacity following fusion to the sacrum with pelvic fixations pediatric spinal deformity patients

OBJECTIVE

To investigate outcomes of ambulatory pediatric patients fused to the sacrum with pelvic fixation.

STUDY DESIGN

Retrospective cohort.

BACKGROUND

Historically in the pediatric spinal deformity literature, long fusions to the sacrum with pelvic fixation have been limited to non-ambulatory patients with pelvic obliquity. This analysis assesses the impact of how long fusions that include pelvic fixation in ambulatory pediatric patients.

METHODS

Consecutive pediatric patients undergoing fusion to the sacrum with pelvic fixation with any ambulatory capacity at a tertiary academic pediatric spine program from 2016 to 2018 were included in this review. Patient demographics, surgical details, and postoperative results were collected and analyzed to identify the impact on postoperative gait and ambulation function. Outcomes were determined from PROMIS, Parent Proxy Mobility questionnaires, as well as an institution specific pediatric gait questionnaire.

RESULTS

25 patients met inclusion criteria. 96.0% of patients had non-idiopathic scoliosis. 48% (12/25) of patients had previous spinal surgery. Median fusion levels were 17.0. 40% (10/25) had preoperative motor and gait deficits and only one patient with a documented decline at postoperative clinical examination. All 25 patients retained ambulatory capacity following their spinal fusion to the sacrum with pelvic fixation. 64% (16/25) of patients or family members completed the postoperative gait questionnaire. The mean PROMIS T-score was 43.4 (95% CI 36.5-50.0) for intact patients. The postoperative gait questionnaires revealed that 75% (6/8) of neurologically intact patients stated they would have the surgery again. 100% (8/8) of these patients noted an improved posture and 25% (2/8) reported a subjective decrease in ambulatory capacity status/post fusion to the sacrum. 100.0% (8/8) of limited ambulatory patients stated they would have the surgery again and noted improved posture with only 25% (2/8) noting a subjective decrease in ambulation postoperatively.

CONCLUSION

In appropriately selected pediatric spinal deformity patients fusion to the sacrum using pelvic fixation can maintain ambulation with high overall surgical satisfaction.

LEVEL OF EVIDENCE

III.

A novel radiological projection of the pelvis to evaluate the sitting imbalance in pelvis nonunions and malunions

INTRODUCTION

Inadequate initial management of unstable pelvic injuries is usually associated with a fracture non-union and/or mal-union. Complete clinical and imaging evaluation is mandatory for a correct preoperative planning. Among other symptoms, sitting discomfort may arise from asymmetry of the ischial tuberosities or pressure from a prominent bony projection. Conventional radiographs are usually taken with the individual in a supine position and not in position where the symptoms are referred. We attempted to define a new radiological projection different than the regular pelvis views to study the position of pelvis of a normal person in sitting position. The second objective was to demonstrate its utility in the evaluation of a pelvic deformity.

MATERIAL AND METHODS

Fifteen healthy individuals were evaluated with a radiological projection in a sitting position. One patient with a vertically migrated pelvis nonunion was also evaluated with the same radiological protocol.

RESULTS

In each volunteer's radiological study, a parallel line could be drawn between the sitting table and both distal aspects of the ischial tuberosities, sacral alas and superior aspect of the iliac wings. A plumb line perpendicular to the above mentioned ones could be drawn uniting the vertebras' spinous processes. A 90⁰ line intersection confirms the absence of deformity. In the pathological case, a pseudo scoliosis of the thoracolumbar spine is detected trying to compensate the pelvis obliquity and maintain equilibrium.

CONCLUSIONS

We determined normal and pathological radiological features in the sitting imbalance of the pelvic in the anteroposterior plane of the pelvis. The study helps to understand the biomechanics and compensation of the pelvis to define surgical indications and predict post correction anatomy.

Intra and inter-observer reliability of determining degree of pelvic obliquity in neuromuscular scoliosis using the EOS-CHAIR® protocol

PURPOSE

Scoliosis with pelvic obliquity (PO) could be investigated with the EOS-CHAIR protocol as the most common deformity especially in patients with trunk hypotonia and quadriplegia. However, the intra-observer and inter-observer reliability of various angles assessing PO was not investigated with this new imaging protocol.

METHODS

A retrospective cohort of 36 EOS frontal full-spine acquisitions made in sitting position was used. The sacroiliac pelvic obliquity angle, iliac crest pelvic obliquity angle, and ischiatic pelvic obliquity angle were assessed in an intra-observer and inter-observer study.

RESULTS

The use of the EOS-CHAIR protocol was implemented satisfactory with a high acceptance rate by all caregivers and patients and their families. Intra-observer and inter-observer reliability was excellent for the three tested angular measurements.

DISCUSSION

As for idiopathic scoliosis, we postulate the EOS system as being superior to standard radiographs to assess 3D spinal deformities in neuromuscular conditions. The EOS-CHAIR protocol improves preoperative comprehension of the lumbosacral junction anatomy in patients with poor standing or sitting postures. Our results show a very high reliability of three different angular measurements of the frontal pelvic obliquity in sitting position. Then it is possible to use one of these three angles as well as the others to assess frontal pelvic obliquity in neuromuscular patients. This frontal pelvic obliquity protocol in sitting position with the EOS-CHAIR is a validated measurement technique that needs to be used now to measure PO as a critical parameter of the global trunk balance in neuromuscular patients.

Burden of Surgical Site Infections Associated with Select Spine Operations and Involvement of Staphylococcus aureus

BACKGROUND

Spine operations may be indicated for treatment of diseases including vertebral injuries, degenerative spinal conditions, disk disease, spinal misalignments, or malformations. Surgical site infection (SSI) is a clinically important complication of spine surgery. Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus (MRSA), is a leading cause of post-spinal SSIs.

METHODS

PubMed and applicable infectious disease conference proceedings were searched to identify relevant published studies. Overall, 343 full-text publications were screened for epidemiologic, mortality, health care resource utilization, and cost data on SSIs associated with specified spine operations.

RESULTS

Surgical site infection rates were identified in 161 studies from North America, Europe, and Asia. Pooled average SSI and S. aureus SSI rates for spine surgery were 1.9% (median, 3.3%; range, 0.1%-22.6%) and 1.0% (median, 2.0%; range, 0.02%-10.0%). Pooled average contribution of S. aureus infections to spinal SSIs was 49.3% (median, 50.0%; range, 16.7%-100%). Pooled average proportion of S. aureus SSIs attributable to MRSA was 37.9% (median, 42.5%; range, 0%-100%). Instrumented spinal fusion had the highest pooled average SSI rate (3.8%), followed by spinal decompression (1.8%) and spinal fusion (1.6%). The SSI-related mortality rate among spine surgical patients ranged from 1.1%-2.3% (three studies). All studies comparing SSI and control cohorts reported longer hospital stays for patients with SSIs. Pooled average SSI-associated re-admission rate occurring within 30 d from discharge ranged from 20% to 100% (four studies). Pooled average SSI-related re-operation rate was 67.1% (median, 100%; range, 33.5%-100%). According to two studies reporting direct costs, spine surgical patients incur approximately double the health care costs when they develop an SSI.

CONCLUSIONS

Available published studies demonstrate a clinically important burden of SSIs related to spine operations and the substantial contribution of S. aureus (including MRSA). Preventive strategies aimed specifically at S. aureus SSIs could reduce health care costs and improve patient outcomes for spine operations.

The radiological assessment of pelvic obliquity in cerebral palsy and the impact on hip development

Pelvic obliquity is a common finding in adolescents with cerebral palsy, however, there is little agreement on its measurement or relationship with hip development at different gross motor function classification system (GMFCS) levels. The purpose of this investigation was to study these issues in a large, population-based cohort of adolescents with cerebral palsy at transition into adult services. The cohort were a subset of a three year birth cohort (n = 98, 65M: 33F, with a mean age of 18.8 years (14.8 to 23.63) at their last radiological review) with the common features of a migration percentage greater than 30% and a history of adductor release surgery. Different radiological methods of measuring pelvic obliquity were investigated in 40 patients and the angle between the acetabular tear drops (ITDL) and the horizontal reference frame of the radiograph was found to be reliable, with good face validity. This was selected for further study in all 98 patients. The median pelvic obliquity was 4° (interquartile range 2° to 8°). There was a strong correlation between hip morphology and the presence of pelvic obliquity (effect of ITDL on Sharpe's angle in the higher hip; rho 7.20 (5% confidence interval 5.59 to 8.81, p < 0.001). This was particularly true in non-ambulant adolescents (GMFCS IV and V) with severe pelvic obliquity, but was also easily detectable and clinically relevant in ambulant adolescents with mild pelvic obliquity. The identification of pelvic obliquity and its management deserves closer scrutiny in children and adolescents with cerebral palsy.

Are S1 Screws a Useful Adjunct to Iliac Screws in Long Fusions to the Sacrum in Cerebral Palsy?

STUDY DESIGN

Multicenter prospective database review of patients with cerebral palsy (CP) and spinal deformity.

OBJECTIVE

To determine if the type of distal fixation is associated with improved correction of coronal deformity or pelvic obliquity (PO) at 2 years in long posterior fusions to the sacrum.

SUMMARY OF BACKGROUND DATA

Multiple techniques are utilized for distal fixation in patients with CP. Although there is emerging evidence that the augmentation of iliac screws with S1 screws may be beneficial, this remains controversial.

METHODS

A prospective, multicenter database was used to identify patients with CP who underwent long posterior fusions to the sacrum. Eighty-eight patients were included, 52 with iliac screws (I) and 36 with iliac and S1 screws (IS) for distal fixation. Preoperative, first erect, and 2-year follow-up radiographs and complications were analyzed. Statistical analysis was performed using ANOVA and repeated measures ANOVA with significance set at P < 0.05.

RESULTS

Scoliosis was the primary deformity in greater than 90% of patients in both groups (P=0.84). Preoperative coronal deformity was similar (I = 83°, IS = 87°, P = 0.49), but correction was better with the use of S1 screws on the first erect radiograph and at 2 years (I = 35°, IS = 22°, P = 0.001), reflecting correction of 58% and 74% for iliac and iliac-S1 screws, respectively (P < 0.001). Preoperative PO was similar (I = 29°, IS = 30°, P = 0.71) and was noted to improve more in the iliac-S1 group by 2 years (I = 11°, IS = 5°, P = 0.004), representing correction of 60% and 77% for the iliac and iliac-S1 groups, respectively (P = 0.018). There was no difference in the rate of major (P = 0.27) or minor (P = 0.65) complications in either group.

CONCLUSION

Bilateral S1 and iliac screws are associated with improved spinal deformity and PO correction at 2 years in the CP population. Two points of distal fixation, S1, and ilium should be considered for this population.

LEVEL OF EVIDENCE

3.