Predicting ideal spinopelvic balance in adult spinal deformity

Anterior column realignment via a minimally invasive hybrid approach in adult spinal deformity surgery: a short-term retrospective study

BACKGROUND

Anterior column realignment (ACR) is a novel surgical method for correcting spinal sagittal balance. meanwhile, oblique lumbar interbody fusion (OLIF) and anterior lumbar interbody fusion (ALIF) are considered minimally invasive surgical methods through natural anatomical space. This study aimed to explore the corrective effects and clinical outcomes of OLIF or ALIF combined with ACR technology in patients with adult spinal deformity (ASD).

METHODS

We retrospectively analyzed patients with sagittal imbalance who received OLIF and/or ALIF and ACR treatment from 2018 to 2021. Surgical time and intraoperative bleeding volume are recorded, the corrective effect is determined by the intervertebral space angle (IVA), lumbar lordosis (LL), the sagittal vertical axis (SVA), clinical outcome is evaluated by preoperative and final follow-up visual analog pain score (VAS), Japanese orthopedic association scores (JOA) and complications.

RESULTS

Sixty-four patients were enrolled in the study, average age of 65.1(range, 47-82) years. All patients completed 173 fusion segments, for 150 segments of ACR surgery. The operation time of ALIF-ACR was 50.4 ± 22.1 min; The intraoperative bleeding volume was 50.2 ± 23.6 ml. The operation time and intraoperative bleeding volume of single-segment OLIF-ACR was 66.2 ± 19.4 min and 70.2 ± 31.6 ml. At the follow-up of 6 months after surgery, the intervertebral space angle correction for OLIF-ACR and ALIF-ACR is 9.2° and 12.2°, the preoperative and postoperative lumbar lordosis were 16.7° ± 6.4°and 47.1° ± 3.6° (p < 0.001), VAS and JOA scores were improved from 6.8 to 1.8 and 7.8 to 22.1 respectively, statistically significant differences were observed in these parameters. The incidence of surgical related complications is 29.69%, but without serious complications.

CONCLUSION

ACR via a minimally invasive hybrid approach for ASD has significant advantages in restoring local intervertebral space angulation and correcting the overall sagittal balance. Simultaneously, it can achieve good clinical outcomes and fewer surgical complications.

Supine and Dynamic Extension Radiographs as the Strongest Predictors of Post-operative Alignment in Minimally Invasive Lumbar Spine Surgery

STUDY DESIGN

Institutional review board-approved retrospective cohort study.

OBJECTIVES

Failure to achieve alignment goals may result in accelerated adjacent segment degeneration and poorer outcomes. In "open" spine surgery, intraoperative tools can fine tune alignment; minimally invasive spine surgery techniques may not allow for this type of intraoperative adjustment. The aim of this study was to identify pre-operative radiographic parameters that accurately predict post-operative alignment after minimally invasive lumbar spine surgery. We hypothesized that pre-operative supine and extension sagittal alignment would predict post-operative standing alignment.

METHODS

50 consecutive patients underwent lateral or anterior lumbar interbody fusion with or without percutaneous posterior instrumentation by a single-surgeon. Sagittal alignment parameters were evaluated on pre-operative standing scoliosis radiographs, dynamic radiographs, supine CT scout, and 6-week post-operative standing radiographs. Demographic and perioperative data were analyzed.

RESULTS

The mean age was 67.8 years. The mean BMI was 29.7. On average, 3 levels were instrumented (range, 2-6). Surgical time was 4.5 ± 1.8 hours. Following surgery, global lordosis increased from 44.7 ± 17° to 48.6 ± 16° (P = .001). However, there was no significant difference between the pre-operative supine (48.5 ± 15°), pre-operative extension (49.2 ± 18°), or 6-week post-operative standing radiographs (48.6 ± 16°). There were strong correlations between post-operative alignment and pre-operative supine (r = .825) and extension (r = .851) alignment.

CONCLUSIONS

Our results suggest that pre-operative supine and extension radiographs could be a gold standard for minimally invasive lumbar spine surgery alignment correction as they predict post-operative alignment. The extension alignment was the strongest predictor of post-operative alignment.

Optimal Lumbar Lordosis Correction for Adult Spinal Deformity with Severe Sagittal Imbalance in Patients Over Age 60: Role of Pelvic Tilt and Pelvic Tilt Ratio

STUDY DESIGN

A retrospective study.

OBJECTIVES

The purpose of this study was to evaluate optimal and ideal target values of the spine balance correction in elderly patients with adult spinal deformity who were over the age of 60 years.

SUMMARY OF BACKGROUND DATA

The target values of the Scoliosis Research Society -Schwab classification to obtain satisfactory alignment and favorable outcomes are used in many spinal reconstruction surgeries. However, uniformly applying the Scoliosis Research Society-Schwab classification to all elderly patients aged 60 years or older showing sagittal malalignment may lead to several inconsistencies.

METHODS

This study included 121 patients (average age 70.5 yr and a minimum 2-yr follow-up) with adult spinal deformity who underwent long-segment fusion from T10 to sacrum. We used Pearson's correlation coefficient to analyze the relationship between clinical and radiographic parameters, and multilinear regression analysis and multivariate logistic regression model (backward elimination method) were conducted using the correlation factors of postoperative (Post) and last follow-up (Last) sagittal vertical axis to find the risk factors of Post sagittal imbalance.

RESULTS

Logistic regression analysis with the correlation factors of Post and Last sagittal vertical axis led to risk factors of Post sagittal imbalance, and after confirming the significance of each path, it was confirmed that the effects of pelvic incidence (PI)- lumbar lordosis (LL) and Post pelvic tilt ratio (PTr) were valid (P < 0.05). After using ROC curve, target value of PI-LL was 1.33, and that of PTr was 25.95%.

CONCLUSION

Through our study, the risk factors of Post sagittal imbalance were the Post value of PI-LL and that of PTr, and target value of PI-LL was <1.33 and that of PTr was <25.95%. These target values can be effective guidelines for spine surgeons who perform spine reconstruction surgeries for elderly patients with a pure sagittal imbalance based on Schwab's formula.Level of Evidence: 4.

What is the best lateral radiograph positioning technique for assessment of sagittal balance: A biomechanical study on influence of different arm positions

PURPOSE

To evaluate the influence of different arm postures from the physiological standing position using force plate analysis of the gravity line.

METHODS

Forty healthy volunteered university students were enrolled. Each subject assumed different standing positions including standing with arms resting on the side (control), with fist over the clavicle (clavicular position), with active shoulder flexion in 30°, 60° and 90° with elbows extended (active flexion A), with hand rest on a bar with a static support (passive flexion P), and with hand rest on a bar with a drip stand (passive flexion D). The offset of the gravity line from the heel was measured by force plate analysis. The offset of the gravity line in different arm positions was compared with the control using paired t-test.

RESULTS

The mean anterior offset of the gravity line in control position is 39.80% of the foot length. All testing positions showed anterior shift of the gravity line compared with the control position from 0.51% to 7.50%. There were statistically significant changes of the gravity line from the control position in all ( p < 0.05), except in the clavicular position ( p = 0.249).

CONCLUSION

All testing positions cause anterior shifting of the center of gravity from the physiological standing position. Clavicular position is the best comparable posture to the physiological standing position in taking a lateral radiograph. We recommend using the clavicular position as the standard testing position in the assessment of the sagittal profile.

Relationship Between Lumbar Lordosis and Pelvic Incidence in the Adolescent Patient: Normal Cohort Analysis and Literature Comparison

STUDY DESIGN

Retrospective review; literature comparison.

OBJECTIVES

To review the literature on the relationship between lumbar lordosis (LL) and pelvic incidence (PI) and evaluate this relationship in asymptomatic adolescents while testing the validity of previously reported adult correlation models between LL and PI in an adolescent population.

SUMMARY OF BACKGROUND DATA

Accurate understanding of the normal spinopelvic relationship is critical when considering surgical fusion of the lumbar spine. Many studies have reported relationships between pelvic measurements and LL in adult populations, but data in pediatric populations is lacking.

METHODS

A literature search was performed to identify previously reported relationships between pelvic parameters and LL in adults and pediatric patients. A cohort of 125 asymptomatic adolescent patients evaluated at our institution was evenly split into two cohorts for model development and validation. Linear regression between LL and PI was performed. The resultant regression model was tested in the validation cohort along with previously reported formulae with LL as a function of PI. Mean absolute error (MAE) was calculated and compared between prior models and the newly developed adolescent model using analysis of variance and post-hoc testing.

RESULTS

In our adolescent cohort (mean age: 13 ± 2), there was a strong correlation between PI and LL (r = 0.53). Regression analysis in the development cohort produced the following predictive model: LL = 0.66(PI) + 24.2. Testing in the validation cohort revealed a good correlation between predicted and actual LL (r = 0.51) and an MAE of 8.3. All but three previously reported models functioned with similar accuracy in the adolescent population, with only two methods having an MAE over 10.

CONCLUSIONS

The majority of previously published formulae for predicting LL as a function of PI developed in adults can be extrapolated to adolescent populations. These relationships are important in understanding how to surgically restore the sagittal alignment in adolescents with spinal deformity.

LEVEL OF EVIDENCE

Level IV.

Spinopelvic Parameters in Asymptomatic Subjects Without Spine Disease and Deformity: A Systematic Review With Meta-Analysis

STUDY DESIGN

A systematic review with meta-analysis.

OBJECTIVE

To combine published data, focusing on the development of optimal spinopelvic parameters in adult asymptomatic subjects without spine deformity while taking into consideration the impact of potential confounders.

SUMMARY OF BACKGROUND DATA

A well-grounded approach to define the optimal spinopelvic parameters is necessary for planning surgical correction of spine deformity.

MATERIALS

Selection criteria: (1) randomized and nonrandomized prospective, cross-sectional, and retrospective studies; (2) participants: asymptomatic subjects without spine deformity aged above 18 years; (3) studied parameters: lumbar lordosis (LL), pelvic incidence, sacral slope, and pelvic tilt; (4) potential confounders: method of measurement, sex, age, ethnicity, weight, height, and body mass index. Search method: Ovid MEDLINE (1946-current) and EMBASE (1980-current), all years through October 2015 were included. Data were collected: number of enrolled subjects, means of the studied characteristics, SD, SE of the means, 95% confidence intervals. A meta-analysis was performed to evaluate the pooled means and range of optimal values (pooled mean±pooled SD) taking into consideration the impact of confounders. The GRADE approach was applied to evaluate the level of evidence.

RESULTS

Seventeen of 1018 studies were included (2926 subjects from 9 countries). The pooled means and the optimal ranges were: LL (L1-S1), 54.6 (42-67) degrees; LL (L1-L5), 37.0 (22-53) degrees; pelvic incidence, 50.6 (39-62) degrees; sacral slope, 37.7 (28-48) degrees; pelvic tilt, 12.6 (3-22) degrees. The pooled results were statistically significant (P<0.001), but heterogeneous. Impact of the following confounders was revealed: method of measurement, ethnicity, age, and body mass index. A methodology was created to define an individualized optimal value and range of each studied parameter taking into consideration the influence of confounders.

CONCLUSIONS

The pooled results and developed methodology can be used as diagnostic criteria for evaluation of the spinopelvic parameters, planning of surgical interventions and evaluation of the treatment effect.

The impact of standing regional cervical sagittal alignment on outcomes in posterior cervical fusion surgery

BACKGROUND

Positive spinal regional and global sagittal malalignment has been repeatedly shown to correlate with pain and disability in thoracolumbar fusion.

OBJECTIVE

To evaluate the relationship between regional cervical sagittal alignment and postoperative outcomes for patients receiving multilevel cervical posterior fusion.

METHODS

From 2006 to 2010, 113 patients received multilevel posterior cervical fusion for cervical stenosis, myelopathy, and kyphosis. Radiographic measurements made at intermediate follow-up included the following: (1) C1-C2 lordosis, (2) C2-C7 lordosis, (3) C2-C7 sagittal vertical axis (C2-C7 SVA; distance between C2 plumb line and C7), (4) center of gravity of head SVA (CGH-C7 SVA), and (5) C1-C7 SVA. Health-related quality-of-life measures included neck disability index (NDI), visual analog pain scale, and SF-36 physical component scores. Pearson product-moment correlation coefficients were calculated between pairs of radiographic measures and health-related quality-of-life scores.

RESULTS

Both C2-C7 SVA and CGH-C7 SVA negatively correlated with SF-36 physical component scores (r =-0.43, P< .001 and r =-0.36, P = .005, respectively). C2-C7 SVA positively correlated with NDI scores (r = 0.20, P = .036). C2-C7 SVA positively correlated with C1-C2 lordosis (r = 0.33, P = .001). For significant correlations between C2-C7 SVA and NDI scores, regression models predicted a threshold C2-C7 SVA value of approximately 40 mm, beyond which correlations were most significant.

CONCLUSION

Our findings demonstrate that, similar to the thoracolumbar spine, the severity of disability increases with positive sagittal malalignment following surgical reconstruction.

Discordance of gravity line and C7PL in patient with adult spinal deformity--factors affecting the occiput-trunk sagittal discordance

BACKGROUND CONTEXT

During quiet standing, the gravity line (GL) can be located according to the sum of the ground reaction forces (GRFs) measured with a force platform. C7 plumb line (C7PL) is an easy method to estimate sagittal trunk balance, but discordance between C7PL and the GL is widely recognized. However, the prevalence of occiput-trunk (O-T) discordance (GL-C7PL>3 cm) and the factors affecting this type of discordance have not yet been determined.

PURPOSE

The purpose of this study was to report the prevalence of O-T discordance in adult spinal deformity (ASD) patients and identify the factors affecting this type of discordance.

STUDY DESIGN

This was a retrospective consecutive case series of ASD.

PATIENT SAMPLE

This retrospective case series included 300 consecutive ASD patients. The inclusion criteria were age more than 50 years, Cobb angle of the main curve more than 20°, and C7PL more than 5 cm. The exclusion criteria consisted of inappropriate radiography; syndromic, neuromuscular, or other pathologic conditions; and previous joint replacement.

OUTCOME MEASURES

The outcome measures included self-reported (Scoliosis Research Society 22 and Oswestry disability index [ODI]) and radiographic measures.

METHODS

In a retrospective consecutive case series, demographic and radiographic patient data were reviewed. Demographic data included age, gender, curve type, SRS22, and ODI. Radiographic data included GL, C7PL, C2-C7, T2-T5, T5-T12, T10-L2, T2 tilt, lumbar lordosis (LL), sacrum slope (SS), pelvic tilt (PT), and pelvic incidence (PI). Global sagittal and spinopelvic alignments were also reviewed. Patients were categorized in either a O-T concordance (C group, GL-C7PL<3 cm) or a O-T discordance (D group, GL-C7PL more than +3 cm) group, and the demographic, radiographic, and clinical outcome data were compared between these groups. One-way analysis of variance, correlation coefficient tests, and multiple regression and logistic regression analyses were performed for statistical analysis. p Value less than .01 was considered statistically significant. Force platform analysis was performed to assess the relationship among GRF, GL, and C7PL.

RESULTS

Among 300 consecutive ASD patients, 72 (24%) were categorized in the D group. There was no significant difference in terms of demographic data between the C and D groups. The SRS and ODI of patients with GL more than 10 cm were significantly lower than those of patients with GL less than 10 cm. Comparisons of regional sagittal alignment showed significantly higher T5-T12 values in the D group, and multiple regression analysis revealed significant correlations among T2-T5, T5-T12, and GL-C7PL. In contrast, the analysis of global sagittal alignment revealed a significantly large T2 sagittal tilt in the D group compared with the C group. Force platform analysis showed concordance between GRF and GL, whereas discordance was observed between GRF and C7PL. The D group could be classified into 2 groups based on the global sagittal alignment: 10 patients were classified as the hypo-compensation type (small SVA, small CL, small TK, and normal-to-small LL), whereas 62 were classified as the forward-leaning type (large sagittal vertical axis, large cervical lordosis, large thoracic kyphosis, and small LL).

CONCLUSIONS

The prevalence of discordance between GL and C7PL in ASD patients was 24%, and thoracic kyphosis and global sagittal alignment were significantly correlated with this discordance. The concordance of GRF and GL and the discordance of GRF and C7PL highlight the importance and necessity of accounting for GL when considering surgical treatment.

An analysis of spinopelvic sagittal alignment after lumbar lordosis reconstruction for degenerative spinal diseases: how much balance can be obtained?

STUDY DESIGN

A retrospective and radiological study of degenerative spinal diseases.

OBJECTIVE

To explore the changes in spinopelvic sagittal alignment after lumbar instrumentation and fusion of degenerative spinal diseases.

SUMMARY OF BACKGROUND DATA

Efforts have been paid to clarify the ideal postoperative sagittal profile for degenerative spinal diseases. However, little has been published about the actual changes of sagittal alignment after lumbar lordosis reconstruction.

METHODS

Radiographical analysis of 83 patients with spinal degeneration was performed by measuring sagittal parameters before and after operations. Comparative studies of sagittal parameters between short (1 level) and long (≥ 2 level) instrumentation and fusion were performed. Different variances (Δ) of these sagittal parameters before and after operations were calculated and compared. Correlative study and linear regression were performed to establish the relationship between variances.

RESULTS

No significant changes were shown in the short-fusion group postoperatively. In the long-fusion group, postoperative lumbar lordosis (LL) and sacral slope (SS) were significantly increased; pelvic tilt (PT), sagittal vertical axis (SVA), pelvic incidence minus lumbar lordosis, and PT/SS were significantly decreased. Different variances of ΔLL, ΔSS, ΔPT, ΔSVA, Δ(pelvic incidence - LL), and ΔPT/SS were significantly greater in the long-fusion group than the short-fusion group. Close correlations were mainly shown among ΔLL, ΔPT, and ΔSVA. Linear regression equations could be developed (ΔPT = -0.185 × ΔLL - 7.299 and ΔSVA = -0.152ΔLL - 1.145).

CONCLUSION

In degenerative spinal diseases, long instrumentation and fusion (≥ 2 levels) provides more efficient LL reconstruction. PT, SS, and SVA improve corresponding to LL in a linear regression model. Linear regression equations could be developed and used to predict PT and SVA change after long instrumentation and fusion for LL reconstruction.

Variations of cervical lordosis and head alignment after pedicle subtraction osteotomy surgery for sagittal imbalance

INTRODUCTION

The variations of the cervical lordosis after correction of sagittal imbalance have been poorly studied. The aim of our study is to verify whether the cervical lordosis changes after surgery for sagittal imbalance.

MATERIALS AND METHODS

Thirty-nine patients were included in the study. Cervical, thoracic and lumbar spine, pelvic and lower-limb sagittal parameters were recorded. The cranial alignment was measured by the newly described Cranial Slope.

RESULTS

The global cervical kyphosis (preop -43°, postop -31.5°) and the upper (preop -24.1°, postop -20.2°) and lower cervical kyphosis (preop -18.1°, postop -9.2°) were significantly reduced after surgical realignment of the trunk. A positive linear correlation was observed between the changes in T1 slope and the lower cervical lordosis, and between T1 slope and the global cervical alignment.

CONCLUSIONS

The cervical lordosis is reduced by surgical correction of malalignment of the trunk, suggesting an adaptive role to maintain the head's neutral position.

Craniopelvic alignment in elderly asymptomatic individuals: analysis of 671 cranial centers of gravity

STUDY DESIGN

Prospective radiographical analysis using the cranial center of gravity (CCG) of sagittal vertical axis (SVA) in elderly asymptomatic individuals.

OBJECTIVE

To determine sex differences and age-related correlations of CCG and relationships between CCG and other spinopelvic parameters/health-related quality of life (HRQOL) measures.

SUMMARY OF BACKGROUND DATA

Few studies have investigated CCG in a relatively large sample of elderly asymptomatic individuals.

METHODS

Six hundred seventy-one healthy participants older than 50 years (mean age, 72.9 yr; range, 50-92 yr) were enrolled. Whole-spine standing radiographs were obtained. The following radiographical measurements were obtained: (1) CCG-C7 SVA, (2) C7-SVA, (3) CCG-SVA, (4) C2-C7 lordosis angle, (5) thoracic kyphosis, (6) lumbar lordosis, (7) pelvic incidence, and (8) sacral slope. HRQOL measures included the EuroQol-5D and Oswestry Disability Index. Pearson product-moment correlation coefficients were calculated between pairs of radiographical measures and HRQOL.

RESULTS

Sex differences were observed in CCG-C7 SVA, CCG-SVA, C2-C7 Cobb angle, thoracic kyphosis, and pelvic incidence. Three SVA parameters (CCG-C7 SVA, C7-SVA, CCG-SVA) rapidly increased between seventh and ninth decades and were approximately 40, 80, and 120 mm, respectively, in the ninth decade. Age-related correlations were observed for all parameters without pelvic incidence, and the CCG measurement correlated the most with age. Furthermore, CCG-SVA correlated with other spinopelvic measurements and HRQOL.

CONCLUSION

Age-related changes and sex difference in craniopelvic alignment were analyzed. Craniopelvic alignment became rapidly positive with age, particularly in the eighth decade. The CCG measurement correlated the most with age and may be a useful index marker of global spinal balance in decision making for surgical treatment of adult deformity involving cervical and thoracolumbar lesions.

LEVEL OF EVIDENCE

4.

Sagittal standing posture, back pain, and quality of life among adults from the general population: a sex-specific association

STUDY DESIGN

A prospective radiographical study of sagittal standing posture among adults consecutively recruited from the general population.

OBJECTIVE

To analyze the relation of suboptimal sagittal standing posture with back pain and health-related quality of life in general adult males and females.

SUMMARY OF BACKGROUND DATA

Clinical studies have shown the association of sagittal standing posture with pain and reduced quality of life, but this relation has not been assessed in the general adult population.

METHODS

As part of the EPIPorto population-based study of adults, 178 males and 311 females were evaluated. Age, education, and body mass index were recorded. Radiographical data collection consisted of 36-in. standing sagittal radiographs. Creation of 3 groups for individual spinopelvic parameters was performed (low, intermediate, or high), and 1 of 4 sagittal types of postural patterns attributed to each participant (Roussouly classification). Back pain prevalence and severity were assessed on the basis of self-reported data and health-related quality of life using 2 main components of the 36-Item Short Form Health Survey.

RESULTS

In males, differences in back pain severity were observed only among pelvic tilt/pelvic incidence ratio groups. Females presenting high pelvic incidence and sacral slope exhibited higher odds of severe back pain than those with intermediate values (adjusted odds ratios = 2.21 and 2.15; 95% confidence interval, 1.24-3.97 and 1.21-3.86; respectively). Sagittal vertical axis showed the largest differences in physical quality of life of females: high group had 8.8 lower score than the low group (P < 0.001), but this result lost statistical significance after adjustment for age, education, and body mass index.

CONCLUSION

Sagittal standing posture was not consistently associated with quality of life measures in males. Increased pelvic incidence and sacral slope may be involved in causing severe back pain among females. Monitoring sagittal postural parameters has limited usefulness as a screening tool for causes of unspecific musculoskeletal symptoms in the general adult population.

LEVEL OF EVIDENCE

3.

Sagittal Cervical Alignment in Adolescent Idiopathic Scoliosis

STUDY DESIGN

Retrospective case series of surgically treated adolescent scoliosis patients.

OBJECTIVES

To assess the radiographic changes of cervical kyphosis and identify the possible factors affecting postoperative sagittal cervical kyphosis in surgically treated patients with adolescent idiopathic scoliosis.

SUMMARY OF BACKGROUND DATA

Cervical kyphosis is a well-recognized phenomenon in patients with adolescent idiopathic scoliosis. Despite recent reports, the prevalence, radiographic changes, and possible factors affecting postoperative sagittal cervical kyphosis are controversial.

MATERIALS AND METHODS

A retrospective review of a single-center database was performed on 133 consecutive patients with adolescent idiopathic scoliosis treated with long instrumented (more than 5 levels) spine fusion (minimum, 2 years; mean, 3.3 years; range, 2 to 5.5 years). A total of 89 patients met all of the inclusion criteria. Preoperative and postoperative radiographic measurements and patient demographics were investigated.

RESULTS

Postoperative cervical kyphosis was observed in 46 patients. Cobb angle decreased from 48.1° ± 13.1° to 15.4° ± 11.1° at the final follow-up. Cervical kyphosis significantly decreased from 5.5° ± 8.9° preoperatively to -1.5° ± 8.9° at the final follow-up. No difference was observed for T2-T5, T5-T12, lumbar lordosis, sacral slope, pelvic incidence, pelvic tilt, and sagittal vertical axis during the follow-up. Notably, T2 sagittal tilt was significantly increased from preoperatively to the final follow-up. Pearson correlation coefficient test showed a strong correlation between postoperative cervical lordosis and T2 sagittal tilt (r = 0.73; p < .001).

CONCLUSIONS

Despite the significant increase of cervical lordosis, 85% of patients still have a kyphotic or less lordotic cervical spine. The strong positive association between cervical lordosis and T2 sagittal tilt suggests that the sagittal cervical alignment of adolescent idiopathic scoliosis patients is closely related to the global sagittal spine balance rather than thoracic kyphosis.

Far lateral approaches (XLIF) in adult scoliosis

PURPOSE

To review the literature on the use of extreme lateral interbody fusion (XLIF) in adult spinal deformity, to discuss on its limits and advantages and to propose a guide to surgical strategy.

METHODS

Surgical technique XLIF is a minimally invasive surgery (MIS) technique to anteriorly access the spine from midthoracic to L5. Important aspects of the technique are a muscle splitting approach through the psoas, use of advanced neuromonitoring to detect the lumbar plexus within the psoas, bilateral annulus release and large footprint interbody cages, supported by the stronger bone of ring apophyses. Large, laterally inserted cages provide strong correction of coronally asymmetrical disc spaces. Literature review MEDLINE database, the Web using Google Scholar and proceedings of the Society for Lateral Access Surgery meetings were searched for relevant articles on technique, results and complications.

RESULTS

XLIF with posterior percutaneous pedicle screw instrumentation provides 40-75 % correction of coronal curves, with modest increase of lordosis. Only anterior XLIF can provide less correction. Self-limited thigh symptoms are frequent after transpsoas access. Permanent neural deficit and visceral complications have also been reported. Combined XLIF-MIS could have a lower complication compared to open circumferential surgery in historical series.

CONCLUSIONS

XLIF is a promising MIS option for adult deformity. Specific surgical strategies are needed to avoid imbalance and define ideal fusion levels and methods. An XLIF-based MIS strategy with a reduced number of levels of lumbar scoliosis can lead to significant advantages. Evaluation of the incidence, complications, their avoidance and real impact on patients' outcomes is necessary to better understand the advantages of this approach. Studies comparing effectiveness and safety of traditional versus XLIF approaches are needed to assist evidence-based decision making.

Pelvic incidence and lumbar spine instability correlations in patients with chronic low back pain

Purpose

Many factors such as lumbar instability and spinopelvic alignment are associated with low back pain. Our purpose was to analyze the pelvic incidence - one of spinopelvic alignment parameters- and spine instability correlations in patients with chronic low back pain.

Methods

Fifty-two patients suffering from chronic low back pain entered this case control study. Lateral spine radiography was taken from patients. pelvic incidence and L3, L4 and L5‘s vertebral body width were measured for all patients, and lumbar instability was evaluated in 3 different levels: L5-S1, L4-L5 and L3-L4.

Results

Thirty-two patients having lumbar instability formed group A and 20 patients without lumbar spine instability allocated to group B. Average age, mean weight, height, body mass index and mean vertebral width of both groups did not differ meaningfully. Pelvic incidence‘s mean amounts set to 53.9 in group B and 57.7 in group A without any significant difference; but pelvic incidence was significantly lower in patients with lumbar instability of L5-S1 origin (P=0.01).

Conclusions

Overall, pelvic incidence did not differ between two groups. However, separate evaluation of each level revealed lumbar instability of L5-S1 segment to be associated with lower pelvic incidence.

Radiological analysis of lumbar degenerative kyphosis in relation to pelvic incidence

BACKGROUND CONTEXT

Lumbar degenerative kyphosis (LDK) is characterized by sagittal imbalance resulting from a loss of lumbar lordosis (LL). The pelvic incidence (PI) regulates the sagittal alignment of the spine and pelvis.

PURPOSE

The purpose of this study is to evaluate the spinopelvic parameters in patients with LDK and to compare them with those of a normal population.

STUDY DESIGN/SETTING

A cross-sectional study.

PATIENT SAMPLE

The selected patients showed characteristic clinical features of LDK. As control group, asymptomatic volunteers without spinal pathology were recruited.

OUTCOME MEASURES

Full-length radiographs of the spine in the anteroposterior and lateral planes were taken, extending from the base of the skull to the proximal femur. Pelvic incidence, sacral slope (SS), pelvic tilt (PT), main thoracic kyphosis (TK), thoracolumbar junction (TLJ), LL, and sagittal vertical axis (SVA) were evaluated.

METHODS

In terms of PI, the patient and control groups were divided into three groups: low (PI≤45°), middle (45°<PI≤60°), and high PI groups (PI>60°). All the spinopelvic parameters were compared between each group and between the patient and control groups in each group. The correlations between each of the parameters were analyzed.

RESULTS

We evaluated 172 patients with symptomatic LDK and 39 healthy volunteers. The number of LDK patients with low, middle, and high PI groups were 44 (25.6%), 72 (44.8%), and 51 (29.6%), respectively. In the control group, the number of low, average, and high PI patients were 18 (46.2%), 15 (38.5%), and 6 (15.4%), respectively. In the control group, PI determined all spinopelvic parameters except SVA. In the LDK group, PI also determined spinopelvic parameters except for TK and SVA. Lumbar degenerative kyphosis with low PI was associated with pronounced kyphosis in LL and TLJ; LDK with a high PI was associated with relatively preserved lordosis in LL with a flat or lordotic TLJ. In terms of pelvic parameters, low PI showed flattened SS and low PT, whereas high PI showed steep SS and high PT.

CONCLUSIONS

The results of this study suggest the importance of the key anatomical parameter, PI, in the determination of sagittal contour in symptomatic LDK patients and normal population. Spinopelvic parameters and pelvic compensatory mechanisms in LDK patients differ according to PI. Identifying the spinopelvic parameters is useful when correcting deformities.

The Impact of Standing Regional Cervical Sagittal Alignment on Outcomes in Posterior Cervical Fusion Surgery

BACKGROUND:

Positive spinal regional and global sagittal malalignment has been repeatedly shown to correlate with pain and disability in thoracolumbar fusion.

OBJECTIVE:

To evaluate the relationship between regional cervical sagittal alignment and postoperative outcomes for patients receiving multilevel cervical posterior fusion.

METHODS:

From 2006 to 2010, 113 patients received multilevel posterior cervical fusion for cervical stenosis, myelopathy, and kyphosis. Radiographic measurements made at intermediate follow-up included the following: (1) C1-C2 lordosis, (2) C2-C7 lordosis, (3) C2-C7 sagittal vertical axis (C2-C7 SVA; distance between C2 plumb line and C7), (4) center of gravity of head SVA (CGH-C7 SVA), and (5) C1-C7 SVA. Health-related quality-of-life measures included neck disability index (NDI), visual analog pain scale, and SF-36 physical component scores. Pearson product-moment correlation coefficients were calculated between pairs of radiographic measures and health-related quality-of-life scores.

RESULTS:

Both C2-C7 SVA and CGH-C7 SVA negatively correlated with SF-36 physical component scores (r = −0.43, P &lt; .001 and r = −0.36, P = .005, respectively). C2-C7 SVA positively correlated with NDI scores (r = 0.20, P = .036). C2-C7 SVA positively correlated with C1-C2 lordosis (r = 0.33, P = .001). For significant correlations between C2-C7 SVA and NDI scores, regression models predicted a threshold C2-C7 SVA value of approximately 40 mm, beyond which correlations were most significant.

CONCLUSION:

Our findings demonstrate that, similar to the thoracolumbar spine, the severity of disability increases with positive sagittal malalignment following surgical reconstruction.

Criteria to restore the sagittal balance in deformity and degenerative spondylolisthesis

PURPOSE

To present in a single source the relevant information needed to assess spinopelvic balance and alignment, and to estimate the amount of correction needed in a patient during surgical treatment.

METHODS

Narrative literature review

RESULTS

Sagittal balance can be evaluated by global balance estimates (sagittal vertical axis and T1 tilt). Other important parameters are the relationship between pelvic incidence and lumbar lordosis (spinopelvic harmony), between pelvic incidence and difference of thoracic kyphosis and lumbar lordosis (spinopelvic balance), excess of pelvic tilt, knee flexion and thoracic compensatory hypokyphosis. Different methods to calculate the amount of surgical correction needed in patients with sagittal imbalance have been based on combinations of these parameters.

CONCLUSIONS

Relevant parameters of sagittal imbalance have been identified and correlated with clinical outcomes. Methods for calculation of surgical correction of imbalance have been proposed, but not validated in patients with mid-term follow-up.