Lumbo-pelvic related indexes: impact on adult spinal deformity surgery

Change in pelvic incidence due to sacral stress fracture following multilevel instrumented fusion

Multilevel-instrumented fusion is a common surgical technique used to treat adult spinal deformity (ASD), but it can occasionally lead to rare complications such as sacral insufficiency fractures. The impact of sacral fractures on spinopelvic parameters, particularly pelvic incidence (PI), has not been thoroughly investigated even though they have been documented in the literature. Here, we present a case of a patient who underwent a Th11-sacrum instrumented fusion for ASD. She underwent a revision surgery 18 months after the first procedure to treat proximal junctional pain brought on by a localised kyphosis of the rods. An asymptomatic sacral fracture was discovered during the radiological evaluation: the PI had increased from 71° to 103° between the 2 surgical procedures.

The Impact of Radiographic Lower Limb-Spinal Length Proportion on Whole-Body Sagittal Alignment

STUDY DESIGN

A radiographic comparative study.

OBJECTIVE

To investigate the influence of radiographic lower limb-spinal length proportion on sagittal radiographic parameters.

SUMMARY OF BACKGROUND DATA

Although lordotic realignment of the lumbar spine is a well-established surgical strategy, its ideal target has not been fully understood. The widely used pelvic incidence-lumbar lordosis discrepancy (PI-LL) method to guide lordotic restoration of the lumber spine in the standing posture, may be further refined using the novel, radiographic lower limb-spinal length proportion parameter in selected subjects.

METHODS

A 100 healthy subjects were imaged in the standing posture using EOS imaging to obtain whole-body lateral radiographs for the measurement of sagittal radiographic parameters. Univariate analyses were performed to compare radiographic parameters between groups with different radiographic lower limb-spinal length proportion. Multivariate analyses were performed to identify the associations between lower limb-spinal length proportions and other radiographic parameters.

RESULTS

Regardless of lower limb-spinal length proportion (mean = 1.4), global lumbar angle (GLA) differed from spinal lordosis (SL), with the absolute means of SL and GLA larger and smaller than pelvic incidence (PI) respectively. Univariate analysis showed that patients with proportionately larger lower limb-spinal length proportion are more likely to have larger mean T1-slope, global thoracic angle (GTA), spinal kyphosis (SK), GLA, and SL. Multivariate analysis showed that a larger lower limb length-spinal length proportion is predictive of larger GLA is less than -47.69° (Odds Ratio (OR) 2.660, P = 0.026), and larger T1-slope of more than 18.84° (OR 3.695, P = 0.012).

CONCLUSION

Larger radiographic lower limb-spinal length proportion results in naturally accentuated spinal curves. These patients balance with a larger lumbar lordosis that is closer to the PI and a higher T1-slope which should be considered for spinal realignment. SL differs from GLA and should be separately assessed.Level of Evidence: 3.

Multiple-rod constructs in adult spinal deformity surgery for pelvic-fixated long instrumentations: an integral matched cohort analysis

PURPOSE

Multiple-rod constructs (Multi-Rod: extra rods for additional pillar support) are occasionally used in adult spinal deformity (ASD) surgery. We aimed to compare and analyze the general outcome of multi-rod constructs with a matched two-rod cohort, to better understand the differences and the similitudes.

METHODS

This is a retrospective matched cohort study including patients with ASD that underwent surgical correction with long posterior instrumentation (more than five levels), pelvic fixation and a minimum 1-year follow-up. Matching was considered with demographical data, preoperative radiographical parameters, preoperative clinical status [health-related quality-of-life (HRQoL) scores] and surgical characteristics (anterior fusion, decompression, rod material, osteotomies). Postoperative radiographical and clinical parameters, as well as complications, were obtained. Univariate and multivariate analysis was performed regarding postoperative improvement, group variables comparison and parameters correlation.

RESULTS

Thirty-three patients with multi-rod construct and 33 matched with a two-rod construct were selected from a database with 346 ASD-operated patients. Both groups had a significant improvement with surgical management in the radiographical and HRQoL parameters (p < 0.001). Differences between groups for the postoperative radiographical, clinical and perioperative parameters were not significant. Rod breakage was more frequent in the two-rod group (8 vs 4, p = 0.089), as well as the respective revision surgery for those cases (6 vs 1 p = 0.046). Risk factors related to revision surgery were greater kyphosis correction (p = 0.001), longer instrumentation (p = 0.037) and greater sagittal vertical axis correction (p = 0.049).

CONCLUSION

No major disadvantage on the use of multi-rod construct was identified. This supports the benefit of using multi-rod constructs to avoid implant failure. These slides can be retrieved under Electronic Supplementary Material.

An analysis of radiographic parameters comparison between lumbar spine latericumbent and full-length lateral standing radiographs

BACKGROUND CONTEXT

The lumbar spine latericumbent and full-length lateral standing radiographs are most commonly used to assess lumbar disorder. However, there are few literatures on the difference and correlation of the sagittal parameters between the two shooting positions.

PURPOSE

The study aimed to investigate the difference of sagittal parameters in spine lateral radiographs between latericumbent and upright positions, identify the correlation, and establish a preliminary linear fitting formula.

STUDY DESIGN

The study is a prospective study on radiographic evaluation of sagittal alignment using latericumbent and upright positions.

PATIENT SAMPLE

One hundred fifty-seven patients were recruited from the orthopedics clinic of a single medical center.

OUTCOME MEASURE

Angle measurement, the intra- and interobserver measurement reliability of measurement, and analysis of the angle measurement were carried out.

METHOD

The sagittal alignment of 157 patients were assessed using Surgimap software from two kinds of lateral radiographs to acquire the following parameters: lumbar lordosis (LL), pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), L4-L5 intervertebral angle (IVA4-5), L4-L5 intervertebral height index (IHI4-5), and PI-LL. The Kolmogorov-Smirnov test, paired t test, Pearson correlation analysis, and multivariate linear regression analysis were used to analyze the data.

RESULTS

The results showed significantly statistical difference in LL, SS, PT, IVA4-5, and PI-LL, except for PI and IHI4-5, between the two positions. There was a significant relativity between standing LL and latericumbent LL (r=0.733, p<.01), PI (r=0.611, p<.01), and SS (r=0.626, p<.01). The predictive formula of standing LL was 12.791+0.777 latericumbent LL+0.395 latericumbent PI-0.506 latericumbent SS (adjusted R²=0.619, p<.05).

CONCLUSION

Not all of sagittal parameters obtained from two positions are identical. Thus, the full-spine lateral standing films are difficult to be replaced. The surgeon should give sufficient consideration to the difference between the two views. We may primarily predict standing LL with the formula when we could not get whole-spine lateral standing radiographs.

Global tilt: a single parameter incorporating spinal and pelvic sagittal parameters and least affected by patient positioning

PURPOSE

Regarding the close interaction between the spinal alignment and the pelvis orientation, no parameter is routinely used to describe and to evaluate the global spinopelvic balance, taking into account simultaneously the spinal part and the pelvic part of the global alignment. We described the global tilt (GT) that could analyze malalignment considering the spine and the pelvis simultaneously. From a geometrical point of view, the global tilt is the sum of the pelvic tilt (PT) and the C7 vertical tilt (angular value of sagittal vertical axis). The aim of this study is to evaluate the global tilt with comparison to PT and sagittal vertical axis (SVA), with the hypothesis that GT would be the least sensitive to positional changes.

METHODS

A cohort of 22 patients with sagittal malalignment was identified from a multicentric database of adult spinal deformities (ASD). Inclusion criteria were age >30 years, SVA > 40 mm and/or PT > 20°. All patients had full spine EOS radiographs in positions 1 and 2 (P1 and P2), in which the patient was asked to stand and put his hands on his shoulders without any effort (P1), or to make an effort to be as straight as possible (P2). PT, SVA and GT were measured in both positions and changes between P1 and P2 were calculated and compared using Student's t test with significance level at p < 0.05.

RESULTS

No significant changes were observed for GT; SVA and PT were significantly influenced by patient positioning. SVA decreased and PT increased for all cases in P2 whereas the changes in GT were in either direction. The average increase in PT was 7.1° (±5.4) or 30.8 % (±24.9); decrease in SVA was 45.1 mm (±25.6) or 60.0 % (±44.2) while the change in GT was 4.4° (±3.3) or 12.6 % (±9.3).

DISCUSSION

GT appears to be less affected by the patient's position compared to SVA and PT. This seems logical because GT contains both spinal alignment and pelvic compensation; it is not affected by their changes in opposing directions.

CONCLUSION

GT appears to be the most reliable single sagittal plane parameter in ASD. It is the least affected by patient position and incorporates both the pelvic and the spinal alignment within one measure.

Correlation of cervical sagittal alignment parameters on full-length spine radiographs compared with dedicated cervical radiographs

BACKGROUND

Radiographic parameters to evaluate the cervical spine in adult deformity using 36-inch films have been proposed. While 36-inch films are used to evaluate spinal deformity, dedicated cervical films are more commonly used to evaluate cervical spine pathology. The purpose of this study is to determine correlations between sagittal measures from a dedicated cervical spine radiographs and 36-inch spine radiographs.

METHODS

Patients who had standing cervical and 36-inch radiographs within four weeks of each other were identified. On separate occasions, the following measures were determined: C0-C2, C0-C7, C1-C2 and C2-C7 sagittal Cobb angles; T1 slope; chin-brow-vertical angle (CBVA), C1-C7 sagittal vertical axis (SVA), C2-C7SVA, center of gravity-C7 sagittal vertical axis (COG-C7SVA). Paired t-tests and correlation analyses were done between parameters from the cervical and the 36-inch film.

RESULTS

Radiographic measurements were collected on 40 patients (33 females and 7 males, mean age of 48.9 ± 14.5 years). All correlations were statistically significant at p < 0.001. C0-C2 Cobb had the strongest correlation (r = 0.81) and C2-C7 Cobb had the weakest (r=0.62). Among sagittal balance parameters, COG-C7SVA had the weakest correlation (r = 0.42) and C1-C7SVA (r = 0.64) and the C2-C7SVA (r = 0.65) had strong correlations. The T1 slope and the CBVA had correlation coefficients of 0.74 and 0.91, respectively. There was no statistically significant difference in measures taken from the cervical film and 36-inch film, except for the C0-C7 Cobb (p = 0.000) with a measurement difference of 7° and the T1 tilt (p = 0.000) with a measurement difference of 5°.

CONCLUSION

Except for COG-C7 SVA, strong correlations between most cervical spine parameters taken from a dedicated cervical film and those taken from a 36-inch film were seen. 36-inch radiographs provide a reasonable estimation of cervical sagittal spine parameters and may obviate the need for a dedicated cervical spine radiograph.

Osteotomies through a fusion mass in the lumbar spine

INTRODUCTION

Flat-back syndrome is one of the main causes of surgical failure after lumbar fusion and can lead to a revision surgery to correct it. Three-column pedicle subtraction osteotomy is an efficient technique to restore lumbar lordosis (LL) for fixed sagittal malalignment. The fusion mass stemming from the past surgeries makes the procedure demanding as most anatomical landmarks are missing.

MATERIAL AND METHODS

This review article will focus on the correction of this lack of LL through the fusion mass. We will successively review the preoperative management, the surgical specificities, and various types of clinical cases that can be encountered in flat-back syndromes.

CONCLUSION

PSO in the fixed fusion mass is technically demanding. Preoperative CT-scan and preoperative navigation allow us to push the limits when anatomical landmarks disappear. Bleeding and neurologic are the two major complications feared by the surgeon. The best way to avoid these revision surgeries is to restore a proper lumbar lordosis at the time of initial surgery by considering lumbo-pelvic indexes.

Osteotomy of the spine for multifocal deformities

INTRODUCTION

When a deformity involves more than one area of the spine, it becomes a multifocal deformity; such a deformity could either be extending on two adjacent segments, or be two separated deformities on two non-adjacent segments.

MATERIALS AND METHODS

The surgical management of multifocal spinal deformities is challenging and must be done through a thorough preoperative planning where spinal and pelvic parameters should accurately be determined. Different strategies should be applied depending on the type of the multifocal deformity, the area involved, the angulation and stiffness of the spine in that area, and the presence of either a pure sagittal malalignment or a combined coronal and sagittal malalignment. This paper discusses these strategies and gives guidelines regarding the use of the different osteotomy techniques depending on each different situation that the deformity spine surgeon may encounter. For instance, where is the ideal level to perform a pedicle subtraction osteotomy (PSO) in a multifocal deformity? How does one take advantage of the remaining high discs to increase the correction without the need for a second PSO? When and where does one perform an asymmetrical PSO? When and where does one perform two PSOs? How does navigation help the spine surgeon to push the surgical limits further in these complex cases?

CONCLUSION

All these questions about the management of multifocal deformities will be discussed and answered with technical details and concrete examples of the different situations that may be encountered.