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1.  Radiographic Comparison of Lateral Lumbar Interbody Fusion Versus Traditional Fusion Approaches: Analysis of Sagittal Contour Change 
Background
Lateral approach to lumbar fusion has been gaining popularity in recent years. With increasing awareness of the significance of sagittal balance restoration in spinal surgery, it is important to investigate the potential of this relatively new approach in correcting sagittal deformities in comparison to conventional approaches. The aim of this study was to evaluate sagittal contour changes seen in lateral lumbar interbody fusion and compare them with radiographic changes in traditional approaches to lumbar fusion.
Methods
Lumbar fusion procedures from January 2008 to December 2009 were reviewed. Four approaches were compared: anterior lumbar interbody fusion (ALIF), lateral lumbar interbody fusion (LLIF), transforaminal interbody fusion (TLIF) and posterior spinal fusion (PSF). Standing pre-operative and 6-week post-operative radiographs were measured in terms of operative level, suprajacent and subjacent level, and regional lumbar lordosis (L1-S1) as well as operative level anterior (ADH) and posterior disc heights (PDH). T-test was used to analyze differences between and within different approaches (α=0.05).
Results
A total of 147 patients underwent lumbar fusion at 212 levels. Mean operative level segmental lordosis change after each procedure is as follows: ALIF 3.8 ± 6.6° (p < 0.01); LLIF 3.2 ± 3.6° (p<0.01); TLIF 1.9 ± 3.9° (p<0.01); and PSF 0.7 ± 2.9° (p =0.13). Overall lumbar lordosis change after each procedure is as follows: ALIF 4.2 ± 5.8° (p < 0.01); LLIF 2.5 ± 4.1° (p<0.01); TLIF 2.1 ± 6.0 (p = 0.02); PSF -0.5 ± 6.2° (p = 0.66). There were no significant changes in the supradjcent and subjacent level lordosis in all approaches except in ALIF where a significant decrease in supradjecent level lordosis was seen. Mean ADH and PDH significantly increased for all approaches except in PSF where PDH decreased post-operatively.
Conclusion
LLIF has the ability to improve sagittal contour as well as other interbody approaches and is superior to posterioronly approach in disc height restoration. However, ALIF provides the greatest amount of segmental and overall lumbar lordosis correction.
Level of Evidence
This is a Level III study.
Clinical Relevance
Regional lordosis correction may be effectively achieved with LLIF. This approach is a good addition to a surgeon's armamentarium in maintenance or restoration of normal lumbar sagittal alignment.
doi:10.14444/2016
PMCID: PMC4480050  PMID: 26114085
LLIF; XLIF; DLIF; ALIF; TLIF; PSF; Transforaminal; Lateral; Transpsoas; Direct; Extreme; Sagittal Balance
2.  Surgical Outcomes of Post-Fusion Lumbar Flatback Deformity with Sagittal Imbalance 
Objectives
To review surgical results of post-fusion lumbar flatback treated with pedicle subtraction osteotomy (PSO) or Smith-Petersen osteotomies (SPOs).
Methods
Twenty-eight patients underwent osteotomies. Radiological outcomes by sagittal vertical axis (SVA), and pelvic tilt (PT), T1 pelvic angle (T1PA), and pelvic incidence (PI)-lumbar lordosis (LL) at preoperative, postoperative 1 month, and final were evaluated. Oswestry Disability Index (ODI), visual analog scale (VAS) score of back pain/leg pain, and Scoliosis Research Society-22 score (SRS-22r) were analyzed and compared. Patients were divided into 2 groups (SVA ≤5 cm : normal, SVA >5 cm : positive) at final and compared outcomes.
Results
Nineteen patients (68%) had PSO and the other 9 patients had SPOs with anterior lumbar interbody fusions (ALIFs) (Mean age : 65 years, follow-up : 31 months). The PT, PI-LL, SVA, T1PA were significantly improved at 1 month and at final (p<0.01). VAS score, ODI, and SRS-22r were also significantly improved at the final (p<0.01). 23 patients were restored with normal SVA and the rest 5 patients demonstrated to positive SVA. SVA and T1PA at 1 month and SVA, PI-LL, and T1PA at final were significantly different (p<0.05) while the ODI, VAS, and SRS-22r did not differ significantly between the groups (p>0.05). Common reoperations were early 4 proximal junctional failures (14%) and late four rod fractures.
Conclusion
Our results demonstrate that PSO and SPOs with ALIFs at the lower lumbar are significantly improves sagittal balance. For maintenance of normal SVA, PI-LL might be made negative value and T1PA might be less than 11° even though positive SVA group was also significantly improved clinical outcomes.
doi:10.3340/jkns.2016.59.6.615
PMCID: PMC5106362  PMID: 27847576
Post-fusion flatback deformity; Pedicle subtraction osteotomy; Smith-Petersen osteotomy; Anterior lumbar interbody fusion
3.  Sagittal balance parameters influence indications for lumbar disc arthroplasty or ALIF 
European Spine Journal  2011;20(Suppl 5):647-662.
Abstract
Chronic lower back pain is a potentially incapacitating condition associated with disc degeneration. Although therapy is primarily pharmaceutical, surgery comprising arthrodesis constitutes an alternative. Anterior intersomatic lumbar arthrodesis (ALIF, anterior interbody lumbar fusion) is the reference approach, although total disc arthroplasty may also be undertaken. Analysis of pelvic and spinal parameters provides the best indication of sagittal balance.
Materials and methods
This was a prospective study in a continuous series of 99 patients presenting chronic lower back pain due to disc disease. Pelvic incidence, sacral slope, pelvic tilt, spino-sacral angle (SSA) and the four back types in the Roussouly classification were studied in radiographs of the whole spine under load using an EOS imaging system.
Results
The pre-operative SSA value for the study population was 126.09° ± 8.45° and the mean spine tilt angle was 90° compared with 95° in healthy subjects. Following surgery, the SSA was considerably increased in the discal arthroplasty, resulting in a significantly more balanced spinal position. In the group of patients undergoing arthrodesis using the ALIF technique, no such significant improvement was found despite the use of a lordosis cage. We showed that in cases of low pelvic incidence, it was necessary to maintain a Roussouly type 1 or 2 back without increasing lordosis. The results demonstrated the value of L4–L5 disc prostheses in these subjects. L5–S1 arthrodesis seemed a more suitable approach for treating patients with elevated sacral slope (back type 3 or 4). This new type of analysis of sagittal parameters should be performed prior to all surgical procedures involving lumbar prostheses.
doi:10.1007/s00586-011-1933-0
PMCID: PMC3175915  PMID: 21845396
Lumbar disc degeneration; ALIF; Total disc prosthesis; Sagittal balance; Spino-pelvic organisation; Spino-sacral angle
4.  Anterior Cervical Discectomy and Fusion Alters Whole-Spine Sagittal Alignment 
Yonsei Medical Journal  2015;56(4):1060-1070.
Purpose
Anterior cervical discectomy and fusion (ACDF) has become a common spine procedure, however, there have been no previous studies on whole spine alignment changes after cervical fusion. Our purpose in this study was to determine whole spine sagittal alignment and pelvic alignment changes after ACDF.
Materials and Methods
Forty-eight patients who had undergone ACDF from January 2011 to December 2012 were enrolled in this study. Cervical lordosis, thoracic kyphosis, lumbar lordosis, sagittal vertical axis (SVA), and pelvic parameters were measured preoperatively and at 1, 3, 6, and 12 months postoperatively. Clinical outcomes were assessed using Visual Analog Scale (VAS) scores and Neck Disability Index (NDI) values.
Results
Forty-eight patients were grouped according to operative method (cage only, cage & plate), operative level (upper level: C3/4 & C4/5; lower level: C5/6 & C6/7), and cervical lordosis (high lordosis, low lordosis). All patients experienced significant improvements in VAS scores and NDI values after surgery. Among the radiologic parameters, pelvic tilt increased and sacral slope decreased at 12 months postoperatively. Only the high cervical lordosis group showed significantly-decreased cervical lordosis and a shortened SVA postoperatively. Correlation tests revealed that cervical lordosis was significantly correlated with SVA and that SVA was significantly correlated with pelvic tilt and sacral slope.
Conclusion
ACDF affects whole spine sagittal alignment, especially in patients with high cervical lordosis. In these patients, alteration of cervical lordosis to a normal angle shortened the SVA and resulted in reciprocal changes in pelvic tilt and sacral slope.
doi:10.3349/ymj.2015.56.4.1060
PMCID: PMC4479836  PMID: 26069131
ACDF; whole spine sagittal alignment; pelvic parameters
5.  Comparison of Sagittal Spinopelvic Alignment between Lumbar Degenerative Spondylolisthesis and Degenerative Spinal Stenosis 
Objective
The purpose of this study was to evaluate the differences in sagittal spinopelvic alignment between lumbar degenerative spondylolisthesis (DSPL) and degenerative spinal stenosis (DSS).
Methods
Seventy patients with DSPL and 72 patients with DSS who were treated with lumbar interbody fusion surgery were included in this study. The following spinopelvic parameters were measured on whole spine lateral radiographs in a standing position : pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis angle (LL), L4-S1 segmental lumbar angle (SLL), thoracic kyphosis (TK), and sagittal vertical axis from the C7 plumb line (SVA). Two groups were subdivided by SVA value, respectively. Normal SVA subgroup and positive SVA subgroup were divided as SVA value (<50 mm and ≥50 mm). Spinopelvic parameters/PI ratios were assessed and compared between the groups.
Results
The PI of DSPL was significantly greater than that of DSS (p=0.000). The SVA of DSPL was significantly greater than that of DSS (p=0.001). In sub-group analysis between the positive (34.3%) and normal SVA (65.7%), there were significant differences in LL/PI and SLL/PI (p<0.05) in the DSPL group. In sub-group analysis between the positive (12.5%) and normal SVA (87.5%), there were significant differences in PT/PI, SS/PI, LL/PI and SLL/PI ratios (p<0.05) in the DSS group.
Conclusion
Patients with lumbar degenerative spondylolisthesis have the propensity for sagittal imbalance and higher pelvic incidence compared with those with degenerative spinal stenosis. Sagittal imbalance in patients with DSPL is significantly correlated with the loss of lumbar lordosis, especially loss of segmental lumbar lordosis.
doi:10.3340/jkns.2014.55.6.331
PMCID: PMC4166328  PMID: 25237428
Sagittal spinopelvic alignment; Pelvic incidence; SVA; Lumbar lordosis; Degenerative spondylolisthesis; Degenerative spinal stenosis
6.  Sagittal Balance and Spinopelvic Parameters After Lateral Lumbar Interbody Fusion for Degenerative Scoliosis: A Case-Control Study 
Spine  2014;39(3):E166-E173.
Study Design
Retrospective matched–cohort analysis.
Objective
To evaluate the change in radiographic parameters in patients undergoing interbody fusion and posterior instrumentation compared to posterior spine fusion alone (PSF) for degenerative scoliosis.
Summary of Background Data
Little is known about the effect of lateral interbody fusion (LIF) on sagittal plane correction in the setting of degenerative scoliosis. We performed a retrospective study to investigate these changes compared to PSF.
Methods
Between 1997 and 2011, 33 patients had LIF at 181 levels between T8 and L5 vertebrae for the treatment of degenerative scoliosis (mean; 5±2 levels). Of those, 23 patients had additional anterior lumbar interbody fusion (ALIF) at 37 levels between L4 and S1 vertebrae (mean; 1.6±0.5 levels). A 1:1 matched control of patients who underwent PSF was performed. Patients were matched by age, gender, and diagnosis. Clinical and radiographic data were collected and compared between the matched cohorts.
Results
Lumbar lordosis was significantly restored in LIF±ALIF compared to PSF cohort (44°±14° versus 36°±15°, p=0.02). The segmental lumbar lordosis over the 102 LIF levels significantly improved from 12°±10° to 21°±13° postoperatively (p<0.0001). However, the change over the 37 ALIF levels was not significant (from 30°±15° to 29°±9°, p=0.8). Sagittal plane alignment was improved in LIF±ALIF compared to PSF cohort and trended toward but did not reach significance (3.8±3.2 cm versus 6.2±5.7 cm, p=0.09). Sacral slope was significantly higher in LIF±ALIF compared to PSF cohort (33°±11° versus 28°±10°, p=0.03). Pelvic tilt was lower in LIF±ALIF compared to PSF cohort and trended toward but did not reach significance (22°±10° versus 26°±10°, p=0.08).
Conclusion
Lumbar lordosis and sacral slope were mildly but statistically improved in the interbody fusion cohort compared to PSF cohort. Sagittal alignment and pelvic tilt trended toward but did not reach statistical significance. Segmental lumbar lordosis was improved at LIF levels more than at ALIF levels.
doi:10.1097/BRS.0000000000000073
PMCID: PMC4340477  PMID: 24150436
lateral interbody fusion; anterior lumbar interbody fusion; posterior spine fusion; sagittal alignment; coronal plane; spinopelvic parameters; degenerative scoliosis
7.  Radiographic Results of Minimally Invasive (MIS) Lumbar Interbody Fusion (LIF) Compared with Conventional Lumbar Interbody Fusion 
Korean Journal of Spine  2013;10(2):65-71.
Objective
To evaluate the radiographic results of minimally invasive (MIS) anterior lumbar interbody fusion (ALIF) and transforaminal lumbar interbody fusion (TLIF).
Methods
Twelve and nineteen patients who underwent MIS-ALIF, MIS-TLIF, respectively, from 2006 to 2008 were analyzed with a minimum 24-months' follow-up. Additionally, 18 patients treated with single level open TLIF surgery in 2007 were evaluated as a comparative group. X-rays and CT images were evaluated preoperatively, postoperatively, and at the final follow-up. Fusion and subsidence rates were determined, and radiographic parameters, including lumbar lordosis angle (LLA), fused segment angle (FSA), sacral slope angle (SSA), disc height (DH), and foraminal height (FH), were analyzed. These parameters were also compared between the open and MIS-TLIF groups.
Results
In the MIS interbody fusion group, statistically significant increases were observed in LLA, FSA, and DH and FH between preoperative and final values. The changes in LLA, FSA, and DH were significantly increased in the MIS-ALIF group compared with the MIS-TLIF group, but SSA and FH were not significantly different. No significant differences were seen between open and MIS-TLIF except for DH. The interbody subsidence and fusion rates of the MIS groups were 12.0±4% and 96%, respectively.
Conclusion
Radiographic results of MIS interbody fusion surgery are as favorable as those with conventional surgery regarding fusion, restoration of disc height, foraminal height, and lumbar lordosis. MIS-ALIF is more effective than MIS-TLIF for intervertebral disc height restoration and lumbar lordosis.
doi:10.14245/kjs.2013.10.2.65
PMCID: PMC3941727  PMID: 24757461
Minimally Invasive Interbody Fusion; Transforaminal Lumbar Interbody Fusion; Anterior Lumbar Interbody Fusion; Radiographic Results
8.  Sagittal spinal alignment in patients with lumbar disc herniation 
European Spine Journal  2009;19(3):435-438.
A retrospective cross-sectional study was designed to evaluate total sagittal spinal alignment in patients with lumbar disc herniation (LDH) and healthy subjects. Abnormal sagittal spinal alignment could cause persistent low back pain in lumbar disease. Previous studies analyzed sciatic scoliotic list in patients with lumbar disc herniation; but there is little or no information on the relationship between sagittal alignment and subjective findings. The study subjects were 61 LDH patients and 60 age-matched healthy subjects. Preoperative and 6-month postoperatively lateral whole-spine standing radiographs were assessed for the distance between C7 plumb line and posterior superior corner on the top margin of S1 sagittal vertical axis (SVA), lumbar lordotic angle between the top margin of the first lumbar vertebra and first sacral vertebra (L1S1), pelvic tilting angle (PA), and pelvic morphologic angle (PRS1). Subjective symptoms were evaluated by the Japanese Orthopedic Association (JOA) score for lower back pain (nine points). The mean SVA value of the LDH group (32.7 ± 46.5 mm, ± SD) was significantly larger than that of the control (2.5 ± 17.1 mm), while L1S1 was smaller (36.7 ± 14.5°) and PA was larger (25.1 ± 9.0°) in LDH than control group (49.0 ± 10.0° and 18.2 ± 6.0°, respectively). At 6 months after surgery, the malalignment recovered to almost the same level as the control group. SVA correlated with the subjective symptoms measured by the JOA score. Sagittal spinal alignment in LDH exhibits more anterior translation of the C7 plumb line, less lumbar lordosis, and a more vertical sacrum. Measurements of these spinal parameters allowed assessment of the pathophysiology of LDH.
doi:10.1007/s00586-009-1240-1
PMCID: PMC2899756  PMID: 20091188
Sagittal spinal alignment; Lumbar disc herniation; Radicular pain
9.  Sagittal Balance Correction in Lateral Interbody Fusion for Degenerative Scoliosis 
Background
Sagittal balance restoration has been shown to be an important determinant of outcomes in corrective surgery for degenerative scoliosis. Lateral interbody fusion (LIF) is a less-invasive technique which permits the placement of a high lordosis interbody cage without risks associated with traditional anterior or transforaminal interbody techniques. Studies have shown improvement in lumbar lordosis following LIF, but only one other study has assessed sagittal balance in this population. The objective of this study is to evaluate the ability of LIF to restore sagittal balance in degenerative lumbar scoliosis.
Methods
Thirty-five patients who underwent LIF for degenerative thoracolumbar scoliosis from July 2013 to March 2014 by a single surgeon were included. Outcome measures included sagittal balance, lumbar lordosis, Cobb Angle, and segmental lordosis. Measures were evaluated pre-operative, immediately post-operatively, and at their last clinical follow-up. Repeated measures ANOVAs were used to assess the differences between pre-operative, first postoperative, and a follow-up visit.
Results
The average sagittal balance correction was not significantly different: 1.06cm from 5.79cm to 4.74cm forward. The average Cobb angle correction was 14.1 degrees from 21.6 to 5.5 degrees. The average change in global lumbar lordosis was found to be significantly different: 6.3 degrees from 28.9 to 35.2 degrees.
Conclusions
This study demonstrates that LIF reliably restores lordosis, but does not significantly improve sagittal balance. Despite this, patients had reliable improvement in pain and functionality suggesting that sagittal balance correction may not be as critical in scoliosis correction as previous studies have indicated.
Clinical Relevance
LIF does not significantly change sagittal balance; however, clinical improvement does not seem to be contingent upon sagittal balance correction in the degenerative scoliosis population.
The DUHS IRB has determined this study meets criteria for an IRB waiver.
doi:10.14444/3029
PMCID: PMC5027815  PMID: 27652200
lateral interbody fusion; sagittal balance; scoliosis; lumbar lordosis; retroperitoneal approach
10.  Surgical Management of Minimally Invasive Anterior Lumbar Interbody Fusion with Stand-Alone Interbody Cage for L4-5 Degenerative Disorders: Clinical and Radiographic Findings 
Neurologia Medico-Chirurgica  2013;53(12):861-869.
Surgical treatment for degenerative spinal disorders is controversial, although lumbar fusion is considered an acceptable option for disabling lower back pain. Patients underwent instrumented minimally invasive anterior lumbar interbody fusion (mini-ALIF) using a retroperitoneal approach except for requiring multilevel fusions, severe spinal canal stenosis, high-grade spondylolisthesis, and a adjacent segments disorders. We retrospectively reviewed the clinical records and radiographs of 142 patients who received mini-ALIF for L4-5 degenerative lumbar disorders between 1998 and 2010. We compared preoperative and postoperative clinical data and radiographic measurements, including the modified Japanese Orthopaedic Association (JOA) score, visual analog scale (VAS) score for back and leg pain, disc height (DH), whole lumbar lordosis (WL), and vertebral wedge angle (WA). The mean follow-up period was 76 months. The solid fusion rate was 90.1% (128/142 patients). The average length of hospital stay was 6.9 days (range, 3–21 days). The mean blood loss was 63.7 ml (range, 10–456 ml). The mean operation time was 155.5 min (range, 96–280 min). The postoperative JOA and VAS scores for back and leg pain were improved compared with the preoperative scores. Radiological analysis showed significant postoperative improvements in DH, WL, and WA, and the functional and radiographical outcomes improved significantly after 2 years. The 2.8% complication rate included cases of wound infection, liquorrhea, vertebral body fractures, and a misplaced cage that required revision. Mini-ALIF was found to be associated with improved clinical results and radiographic findings for L4-5 disorders. A retroperitoneal approach might therefore be a valuable treatment option.
doi:10.2176/nmc.oa2012-0379
PMCID: PMC4508736  PMID: 24140782
anterior lumbar interbody fusion; circumferential fusion; degenerative lumbar spinal disorder; minimally invasive therapy
11.  Comparison of instrumented anterior interbody fusion with instrumented circumferential lumbar fusion 
European Spine Journal  2003;12(6):567-575.
Posterior lumbar interbody fusion (PLIF) restores disc height, the load bearing ability of anterior ligaments and muscles, root canal dimensions, and spinal balance. It immobilizes the painful degenerate spinal segment and decompresses the nerve roots. Anterior lumbar interbody fusion (ALIF) does the same, but could have complications of graft extrusion, compression and instability contributing to pseudarthrosis in the absence of instrumentation. The purpose of this study was to assess and compare the outcome of instrumented circumferential fusion through a posterior approach [PLIF and posterolateral fusion (PLF)] with instrumented ALIF using the Hartshill horseshoe cage, for comparable degrees of internal disc disruption and clinical disability. It was designed as a prospective study, comparing the outcome of two methods of instrumented interbody fusion for internal disc disruption. Between April 1994 and June 1998, the senior author (N.R.B.) performed 39 instrumented ALIF procedures and 35 instrumented circumferential fusion with PLIF procedures. The second author, an independent assessor (S.M.), performed the entire review. Preoperative radiographic assessment included plain radiographs, magnetic resonance imaging (MRI) and provocative discography in all the patients. The outcome in the two groups was compared in terms of radiological improvement and clinical improvement, measured on the basis of improvement of back pain and work capacity. Preoperatively, patients were asked to fill out a questionnaire giving their demographic details, maximum walking distance and current employment status in order to establish the comparability of the two groups. Patient assessment was with the Oswestry Disability Index, quality of life questionnaire (subjective), pain drawing, visual analogue scale, disability benefit, compensation status, and psychological profile. The results of the study showed a satisfactory outcome (score≤30) on the subjective (quality of life questionnaire) score of 71.8% (28 patients) in the ALIF group and 74.3% (26 patients) in the PLIF group (P>0.05). On categorising Oswestry Index scores into "excellent", "better", "same", and "worse", we found no difference in outcome between the two groups: 79.5% (n=31) had satisfactory outcome with ALIF and 80% (n=28) had satisfactory outcome with PLIF. The rate of return to work was no different in the two groups. On radiological assessment, we found two nonunions in the circumferential fusion (PLIF) group (94.3% fusion rate) and indirect evidence of no nonunions in the ALIF group. There was no significant difference between the compensation rate and disability benefit rate between the two groups. There were three complications in ALIF group and four in the PLIF (circumferential) group. On the basis of these results, we conclude that it is possible to treat discogenic back pain by anterior interbody fusion with Hartshill horseshoe cage or with circumferential fusion using instrumented PLIF.
doi:10.1007/s00586-002-0516-5
PMCID: PMC3467994  PMID: 14673717
Disc degeneration; Interbody fusion; Cages
12.  Pre- and post-operative sagittal balance in idiopathic scoliosis: a comparison over the ages of two cohorts of 132 adolescents and 52 adults 
European Spine Journal  2012;22(Suppl 2):203-215.
Study design
Retrospective study of a prospective clinical and radiological database of subjects with adolescent (AIS) and adult (AS) idiopathic scoliosis undergoing surgical correction by posterior approach.
Objectives
To evaluate the differences in sagittal alignment of the spine and pelvis in AIS and AS before surgery and changes after surgery in both populations.
Summary of background data
The relationship between the spine and pelvis highly influences the sagittal balance in adults and adolescents. However, the sagittal alignment of the spine and pelvis before and after surgery in idiopathic scoliosis, whatever the age, is poorly defined in the literature.
Methods
Clinical and radiological data were extracted from a prospective database of 132 AIS patients and 52 AS before and at last follow-up after surgical correction. Sagittal parameters were evaluated on AP and lateral radiographs using a custom software: pelvic incidence (PI), sacral slope (SS), pelvic tilt (PT), lumbar lordosis (LL), thoracic kyphosis (TK), C7 Barrey’s ratio, spino-sacral angle (SSA). A new algorithm of combination of balance parameters was proposed to characterize and compare the various pathological spino-pelvic settings. Based on PI subdivision in high (<55°) and low values (>55°), then on a range of PT indexed on PI giving the pelvis positioning (anteverted, normal or retroverted), the population was finally characterized by the C7 plumbline position with regard to the posterior edge of the sacrum and the center of the femoral heads, in balanced, slightly unbalanced and unbalanced. More specifically, the AIS study included the cervical shape alignment with cervical lordosis (CL) and sagittal thoracic profile assessment (hypo vs. normokyphotic). In AS, the study focused on thoraco-lumbar kyphosis (TLK) occurrence (LL length). Paired Student t tests were used for comparison (α = 0.02).
Results
Pre-operatively, in AIS there was a prevalence of lower PI (57 %). Whatever the PI, PT remained anteverted or normal. Positioning of C7 was much more unbalanced, forward of the femoral heads (50 %), than in asymptomatic population (17 %). There was a notable loss and reversal of cervical lordosis in the majority of subjects, with an average cervical kyphosis measurement of 10 ± 18°. Thoracic kyphosis values were lower than average, while lumbar lordosis values were within normal limits. After surgery, in the entire group, a slight but significant increase of PT coupled to a decrease of SS and LL was noted, while no changes could be documented in thoracic kyphosis and cervical lordosis. However, when sub-classified according to thoracic hypo versus normokyphosis pre-op, there was a significant decrease of TK coupled to a decrease of LL and CL in the normokyphotic group, while TK and CL were improved in the hypokyphotic group. A significant number of patients improved their global balance. Changes in sagittal profile between Lenke curve types were minimal. In AS there were significant differences between low and high PI populations. Severity of unbalance increased in high PI population with association of retroverted pelvis and forward unbalance. In lower PI, increasing PT was generally sufficient to balance the patients. The occurrence of TLK was strongly increased in the entire population and became the rule in those with lower PI (76 %). Post-operatively, in those with high PI, PT did not change while global balance improved slightly. The strategy of correction in higher PI was to maintain TLK. In those with low PI, PT improved while C7 did not change. Correction of TLK was obtained in eight cases.
Conclusions
A decrease of cervical lordosis and thoracic kyphosis is commonly associated with AIS. The anterior unbalance frequently found in AIS does not seem to have the same significance of severity as in AS. In AIS PI does not change the balance criterions, while in AS the severity of unbalance is increased with higher PI. TLK seems to be a way of worsening the balance in elderly, mainly in lumbar and thoraco-lumbar scoliosis with low PI. Surgical correction of the thoracic and lumbar spine in AIS induces significant changes in the sagittal spino-pelvic profile. Changes in the cervical sagittal profile vary according to the pre-op sagittal profile of the thoracic kyphosis. Cervical lordosis and thoracic kyphosis are improved by surgical correction in subjects with pre-operative hypokyphosis, but a reverse effect is noted in those with normal pre-operative kyphosis. The clinical significance of these changes in sagittal shape remains to be determined. In AS, it appears easier to restore a good balance in the lower PI population than in those with less pre-operative unbalance.
doi:10.1007/s00586-012-2571-x
PMCID: PMC3616473  PMID: 23188161
Adolescent idiopathic scoliosis; Adult scoliosis; Kyphosis; Lordosis; Pelvis; Sagittal balance; Spine; Cervical spine
13.  The impact of sagittal balance on clinical results after posterior interbody fusion for patients with degenerative spondylolisthesis: A Pilot study 
Background
Comparatively little is known about the relation between the sagittal vertical axis and clinical outcome in cases of degenerative lumbar spondylolisthesis. The objective of this study was to determine whether lumbar sagittal balance affects clinical outcomes after posterior interbody fusion. This series suggests that consideration of sagittal balance during posterior interbody fusion for degenerative spondylolisthesis can yield high levels of patient satisfaction and restore spinal balance
Methods
A retrospective study of clinical outcomes and a radiological review was performed on 18 patients with one or two level degenerative spondylolisthesis. Patients were divided into two groups: the patients without improvement in pelvic tilt, postoperatively (Group A; n = 10) and the patients with improvement in pelvic tilt postoperatively (Group B; n = 8). Pre- and postoperative clinical outcome surveys were administered to determine Visual Analogue Pain Scores (VAS) and Oswestry disability index (ODI). In addition, we evaluated full spine radiographic films for pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL), sacrofemoral distance (SFD), and sacro C7 plumb line distance (SC7D)
Results
All 18 patients underwent surgery principally for the relief of radicular leg pain and back pain. In groups A and B, mean preoperative VAS were 6.85 and 6.81, respectively, and these improved to 3.20 and 1.63 at last follow-up. Mean preoperative ODI were 43.2 and 50.4, respectively, and these improved to 23.6 and 18.9 at last follow-up. In spinopelvic parameters, no significant difference was found between preoperative and follow up variables except PT in Group A. However, significant difference was found between the preoperative and follows up values of PT, SS, TK, LL, and SFD/SC7D in Group B. Between parameters of group A and B, there is borderline significance on preoperative PT, preoperative LL and last follow up SS.
Correlation analysis revealed the VAS improvements in Group A were significantly related to postoperative lumbar lordosis (Pearson's coefficient = -0.829; p = 0.003). Similarly, ODI improvements were also associated with postoperative lumbar lordosis (Pearson's coefficient = -0.700; p = 0.024). However, in Group B, VAS and ODI improvements were not found to be related to postoperative lumbar lordosis and to spinopelvic parameters.
Conclusion
In the current series, patients improving PT after fusion were found to achieve good clinical outcomes in degenerative spondylolisthesis. Overall, our findings show that it is important to quantify sagittal spinopelvic parameters and promote sagittal balance when performing lumbar fusion for degenerative spondylolisthesis.
doi:10.1186/1471-2474-12-69
PMCID: PMC3080356  PMID: 21466688
14.  Spinal sagittal imbalance in patients with lumbar disc herniation: its spinopelvic characteristics, strength changes of the spinal musculature and natural history after lumbar discectomy 
Background
Spinal sagittal imbalance is a widely acknowledged problem, but there is insufficient knowledge regarding its occurrence. In some patients with lumbar disc herniation (LDH), their symptom is similar to spinal sagittal imbalance. The aim of this study is to illustrate the spinopelvic sagittal characteristics and identity the role of spinal musculature in the mechanism of sagittal imbalance in patients with LDH.
Methods
Twenty-five adults with spinal sagittal imbalance who initially came to our clinic for treatment of LDH, followed by posterior discectomy were reviewed. The horizontal distance between C7 plumb line-sagittal vertical axis (C7PL-SVA) greater than 5 cm anteriorly with forward bending posture is considered as spinal sagittal imbalance. Radiographic parameters including thoracic kyphotic angle (TK), lumbar lordotic angle (LL), pelvic tilting angle (PT), sacral slope angle (SS) and an electromyography(EMG) index ‘the largest recruitment order’ were recorded and compared.
Results
All patients restored coronal and sagittal balance immediately after lumbar discectomy. The mean C7PL-SVA and trunk shift value decreased from (11.6 ± 6.6 cm, and 2.9 ± 6.1 cm) preoperatively to (−0.5 ± 2.6 cm and 0.2 ± 0.5 cm) postoperatively, while preoperative LL and SS increased from (25.3° ± 14.0° and 25.6° ± 9.5°) to (42.4° ± 10.2° and 30.4° ± 8.7°) after surgery (P < 0.05). The preoperative mean TK and PT (24.7° ± 11.3° and 20.7° ± 7.8°) decreased to (22.0° ± 9.8° and 15.8 ± 5.5°) postoperatively (P < 0.05). The largest recruitment order on the level of T7-T8, T12-L1 and the herniated level all improved compared with before and after surgery (P < 0.05). All patients have been followed up for more than 2 years. The mean ODI was 77.8 % before surgery to 4.2 % at the final follow-up.
Conclusions
Spinal sagittal imbalance caused by LDH is one type of compensatory sagittal imbalance. Compensatory mechanism of spinal sagittal imbalance mainly includes a loss of lumbar lordosis, an increase of thoracic kyphosis and pelvis tilt. Spinal musculature plays an important role in spinal sagittal imbalance in patients with LDH.
doi:10.1186/s12891-016-1164-y
PMCID: PMC4957349  PMID: 27444272
Spinal sagittal imbalance; Lumbar disc herniation; Spinal musculature; Electromyography
15.  The Relationship between T1 Sagittal Angle and Sagittal Balance: A Retrospective Study of 119 Healthy Volunteers 
PLoS ONE  2016;11(8):e0160957.
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.
doi:10.1371/journal.pone.0160957
PMCID: PMC4981349  PMID: 27513865
16.  Influence of spinal sagittal alignment, body balance, muscle strength, and physical ability on falling of middle-aged and elderly males 
European Spine Journal  2013;22(6):1346-1353.
Objective
Risk factors for falling in elderly people remain uncertain, and the effects of spinal factors and physical ability on body balance and falling have not been examined. The objective of this study was to investigate how factors such as spinal sagittal alignment, spinal range of motion, body balance, muscle strength, and gait speed influence falling in the prospective cohort study.
Methods
The subjects were 100 males who underwent a basic health checkup. Balance, SpinalMouse® data, grip strength, back muscle strength, 10-m gait time, lumbar lateral standing radiographs, body mass index, and fall history over the previous year were examined. Platform measurements of balance included the distance of movement of the center of pressure (COP) per second (LNG/TIME), the envelopment area traced by movement of the COP (E AREA), and the LNG/E AREA ratio. The thoracic/lumbar angle ratio (T/L ratio) and sagittal vertical axis (SVA) were used as an index of sagittal balance.
Results
LNG/TIME and E AREA showed significant positive correlations with age, T/L ratio, SVA, and 10-m gait time; and significant negative correlations with lumbar lordosis angle, sacral inclination angle, grip strength and back muscle strength. Multiple regression analysis showed significant differences for LNG/TIME and E AREA with T/L ratio, SVA, lumbar lordosis angle and sacral inclination angle (R2 = 0.399). Twelve subjects (12 %) had experienced a fall over the past year. Age, T/L ratio, SVA, lumbar lordosis angle, sacral inclination angle, grip strength, back muscle strength, 10-m gait time, height of the intervertebral disc, osteophyte formation in radiographs and LNG/E AREA differed significantly between fallers and non-fallers. The group with SVA > 40 mm (n = 18) had a significant higher number of subjects with a single fall (6 single fallers/18: p = 0.0075) and with multiple falls (4 multiple fallers/18: p = 0.0095).
Conclusion
Good spinal sagittal alignment, muscle strength and 10-m gait speed improve body balance and reduce the risk of fall. Muscle strength and physical ability are also important for spinal sagittal alignment. Body balance training, improvement of physical abilities including muscle training, and maintenance of spinal sagittal alignment can lead to prevention of fall.
doi:10.1007/s00586-013-2721-9
PMCID: PMC3676567  PMID: 23443680
Fall; Spinal sagittal alignment; Body balance; Muscle strength; Physical ability
17.  Sagittal Plane Analysis of Adolescent Idiopathic Scoliosis after VATS (Video-Assisted Thoracoscopic Surgery) Anterior Instrumentations 
Yonsei Medical Journal  2007;48(1):90-96.
Radiographic sagittal plane analysis of VATS (video-assisted thoracoscopic surgery) anterior instrumentation for adolescent idiopathic scoliosis. This is retrospective study. To report, in details about effects of VATS anterior instrumentation on the sagittal plane. Evaluations of the surgical outcome of scoliosis have primarily studied in coronal plane correction, functional, and cosmetic aspects. Sagittal balance, as well as coronal balance, is important in functional spine. Recently, scoliosis surgery applying VATS has been increasingly performed. Its outcome has been reported several times; however, according to our search of the literature, the only one study partially mentioned. The study population was a total of 42 cases of idiopathic scoliosis patients (8 male, 34 female). Their mean age was 15.6 years (13 to 18 years). The 18 cases were Lenke IA type, 16 cases were Lenke IB type, and 8 cases were Lenke IC type. The preoperative Cobb's angle was 54.5 ± 13.9°. All patients were followed up for a minimum of 2 years and implanted, on average, at the 5.9 level (5 to 8 levels). The most proximal implant was the 4th thoracic spine, and the most distal implant was the 1st lumbar spine. Whole spine standing PA and lateral radiographs were taken before surgery, 2 months after surgery, and at the last follow up (range 24-48 months, mean 35 months). The C7 plumbline proximal junctional measurement (PJM), distal junctional measurement (DJM), thoracic kyphosis, and lumbar lordosis angles were measured and compared. In all cases, follow-ups were possible and survived till the last follow up. The Cobb's angle in coronal plane at the last follow up was 19.7 ± 9.3° and was corrected to 63.8% on average. The preoperative C7 sagittal plumbline before surgery was -13.9 ± 29.1 mm, the final follow up was -9.9 ± 23.8 mm, and the average positive displacement was 4 mm. Thoracic kyphosis was increased from preoperative 18.2 ± 7.7° to 22.4 ± 7.2° on average at the last follow up, and the increase was, on average, 4.2°. The PJM angel was increased from 6.2 ± 4.3° preoperative to 8.8 ± 3.7° at the last follow up, and the increment was, on the average, 2.6°. The DJM angle before surgery was 6.8 ± 5.1° and 6.7 ± 4° at the last follow up, and did not change noticeably. Preoperative lumbar lordosis was 42 ± 10.7° and 43.5 ± 11.1° after surgery. Similarly, it did not change greatly. The scoliosis surgery applying VATS displaced the C7 sagittal plumb line by 4 mm to the anteriorly, increased thoracic kyphosis by 4.2°, and increased PJM by 2.6°. DJM and lumbar lordosis, before and after operation, were not significantly different. Although the surgical technique of VATS thoracic instrumentation is difficult to make the normal thoracic kyphosis, an acceptable sagittal balance can be obtained in Lenke type I adolescent idiopathic scoliosis using VATS.
doi:10.3349/ymj.2007.48.1.90
PMCID: PMC2627991  PMID: 17326250
Scoliosis; VATS; sagittal balance
18.  Subsidence after anterior lumbar interbody fusion using paired stand-alone rectangular cages 
European Spine Journal  2005;15(1):16-22.
The authors conducted a study to determine at what stage after surgery the subsidence occurred, and to assess the relationships of radiographic fusion and the recurrence of symptoms with the development of subsidence. Ninety patients underwent a single-level anterior lumbar interbody fusion (ALIF) using paired stand-alone rectangular cages between November 2000 and June 2002. All patients had regular clinical or imaging follow-up for a minimum of 19 months (range 19–38 months, mean = 27 months). The ratio of male to female patients was 1:3.1. The patients’ ages at the time of ALIF ranged from 25 to 72 years, with a mean of 53 years. The preoperative and postoperative intervertebral disc heights were serially measured by plain radiographs. The location of cage subsidence into the vertebral body and times until the presence of subsidence were also assessed. The mean preoperative intervertebral disc height was 11.6±3.1 mm, which spread immediately after surgery to 16.9±2.0 mm. This increase was statistically significant (P=0.001). At the last follow-up visit, the mean intervertebral disc height had been reduced to 13.2±2.4 mm. Sixty-nine of 90 patients (76.7%) developed cage subsidence into the surrounding vertebral body. Subsidence was more often noted in the superior endplate above the cage with regard to the location of cage subsidence [superior endplate: 27 patients (39.1%), inferior endplate: 12 patients (17.3%), both: 30 patients (43.6%)]. The onset of subsidence varied from 0.25 to 8 months after surgery (median, 2.75 months). The 8-, 12-, and 16-week actuarial rates for developing cage subsidence were 38.9, 63.4, and 70.7%, respectively, when using the Kaplan–Meier method. There was no statistical correlation between the recurrence of symptoms (P=0.3952) and radiographic fusion (P=0.9518) with the log-rank test in development of subsidence. This study demonstrates that cage subsidence is an expected occurrence after ALIF using stand-alone rectangular cages. The 3- and 4-month actuarial rates for developing cage subsidence were 63.4 and 70.7%, respectively, and cage subsidence had no correlation with recurrence of symptoms and radiographic fusion in our study.
doi:10.1007/s00586-004-0817-y
PMCID: PMC3454564  PMID: 15843972
Anterior lumbar interbody fusion (ALIF); Cage; Subsidence
19.  Single transverse-orientation cage via MIS-TLIF approach for the treatment of degenerative lumbar disease: a technical note 
Background: Single transverse cage placed in the anterior vertebral column can better maintain lumbar lordosis and sagittal alignment and is frequently used via the lateral transpsoas approach. However, there is no clear description in the literature of the steps required to place the single transverse cage during the instrumented transforaminal lumbar interbody fusion (TLIF) procedure for the treatment of degenerative lumbar disease. The objective of this study is to describe the technique using single transverse-orientation cage when performing TLIF procedures. Materials and methods: We present 18 illustrative cases in which single transverse-orientation cage was placed according to a step-by-step technique that can be used during the TLIF procedure. Information acquired included procedure time, intraoperative blood loss and postoperative complications. The preoperative and postoperative Oswestry Disability Index (ODI) and the visual analogue scale (VAS) scores were recorded. Changes in disc height and segmental lordosis were measured at radiographs. Results: The single transverse-orientation cage was successfully placed in 18 patients in a stepwise technique to achieve lumbar fusion. Using this technique, the patients significantly improved clinically and radiographically at postoperative visits. Conclusions: This is the first report demonstrating the safety and efficacy of instrumented TLIF with single transverse-orientation cage for the treatment of degenerative lumbar disease. Single transverse-orientation cage via MIS-TLIF approach can maintain greater lumbar lordosis and avoid the unique complications of lateral transpsoas approach. Understanding the options for cage placement is important for surgeons considering the use of this technique.
PMCID: PMC4613072  PMID: 26550387
Spinal fusion; interbody cage; TLIF; degenerative lumbar disease
20.  Is the Lateral Transpsoas Approach Feasible for the Treatment of Adult Degenerative Scoliosis? 
Background
Lumbar degenerative scoliosis is a common condition in the elderly. Open traditional surgical approaches are associated with high-morbidity complication rates. Less invasive options may carry fewer risks in this patient population. A minimally disruptive lateral transpsoas retroperitoneal technique to accomplish interbody fusion was developed to avoid the morbidity of traditional open surgery, but this approach as an anterior stand-alone construction has not been reported yet for the treatment of adult degenerative scoliosis.
Questions/purposes
We determined (1) the clinical outcomes (VAS scores for back and leg, Oswestry Disability Index), (2) the radiographic outcomes (Cobb angle, lumbar lordosis, sacral slope, high-grade subsidence, osseous fusion), and (3) the reoperation and complication rates in an older population undergoing this surgical approach.
Methods
Between 2004 and 2008, 62 patients were treated surgically for adult degenerative scoliosis, of whom 46 (74%) were treated with stand-alone lateral lumbar interbody fusion; 11 of these (24%) were lost to followup before 24 months, leaving the records of 35 patients (nine men, 26 women; mean ± SD age, 68 ± 10 years) available for this retrospective review. General indications for this approach included neurogenic claudication and radicular symptoms with history of chronic low-back pain. A total of 107 levels were treated (mean, three; range, one to seven). Clinical and radiographic outcomes were assessed at a followup of 24 months.
Results
Mean VAS back pain scores improved from 85 mm preoperatively to 27 mm at latest followup (p < 0.001). VAS leg pain scores improved from 91 mm to 24 mm (p < 0.001). Oswestry Disability Index scores improved from 51 to 29 (p < 0.001). Coronal alignment improved from Cobb angles of 21° to 12° (p < 0.001). Lumbar lordosis improved from 33° to 41° (p < 0.001). Sacral slope was enhanced from 28° to 35° (p < 0.001). Fusion rate was 84% at final evaluation. High-grade subsidence was seen in 10 patients (29%). Three patients (9%) needed further surgical intervention.
Conclusions
Use of the lateral approach achieved reasonable coronal and sagittal correction, as well as improvements in pain and function, in mild scoliotic deformities; however, subsidence was a concern, occurring in 29% of patients. Questions still remain regarding the need for additional supplementation or the use of wider cages to prevent subsidence.
Level of Evidence
Level IV, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-3263-5
PMCID: PMC4016469  PMID: 23996097
21.  Does Disc Space Height of Fused Segment Affect Adjacent Disc Degeneration in Anterior Lumbar Interbody Fusion? A Radiological Study 
Background
The restoration of disc space height (DSH) is essential in anterior lumbar interbody fusion (ALIF), while it is unclear whether the reduction of DSH may alter the mechanical status and adversely affect adjacent segment, and few literatures focused on the subject.
Methods
Ninety five patients who had undergone ALIF for degenerative disc disease at our institution between March 2004 and March 2007 were retrospectively reviewed and 76 patients were enrolled in this study. Preoperative, postoperative and the final follow-up segmental lordosis (SL), whole lumbar lordosis (WLL) and DSH were measured and compared in adjacent segmental degeneration (ASD) group and non-ASD group, and the relationship between DSH, SL, WLL and ASD were investigated retrospectively.
Results
In 76 patients, the radiographic ASD was proven in 25 (32.9%) and symptomatic ASD in 2 patients. There was a significant correlation between DSH and SL, but was insignificant between DSH and WLL, and a significant correlation was noticed between ASD and SL, WLL and DSH at final follow-up.
Conclusion
The normal DSH and SL is important for preventing ASD and an anterior cage with appropriate height and lordotic angle to be used in ALIF to maintain the proper DSH and SL.
PMCID: PMC3372028  PMID: 22737570
Adjacent segment degeneration; Anterior lumbar interbody fusion; Disc space height; Segmental lordosis; Whole lumbar lordosis
22.  Influence of transforaminal lumbar interbody fusion procedures on spinal and pelvic parameters of sagittal balance 
European Spine Journal  2011;21(6):1200-1206.
Introduction
Restitution of sagittal balance is important after lumbar fusion, because it improves fusion rate and may reduce the rate of adjacent segment disease. The purpose of the present study was to describe the impact of transforaminal lumbar interbody fusion (TLIF) procedures on pelvic and spinal parameters and sagittal balance.
Materials and methods
Forty-five patients who had single-level TLIF were included in this study. Pelvic and spinal radiological parameters of sagittal balance were measured preoperatively, postoperatively and at latest follow-up.
Results
Age at surgery averaged 58.4 (±9.6) years. Mean follow-up was 35.1 months (±4.1). Twenty-nine percent of the patients exhibited anterior imbalance preoperatively, with high pelvic tilt (17.6° ± 7.9°). Of the 32 (71%) patients well balanced before the procedure, 22 (70%) had a large pelvic tilt (>20°), due to retroversion of the pelvis as an adaptive response to the loss of lordosis. Three dural tears (7%) were reported intraoperatively. Interbody cages were more posterior than intended in 27% of the cases. Disc height and lumbar lordosis at fusion level significantly increased postoperatively (p < 0.05 and p < 0.001). Pelvic tilt was significantly reduced (p < 0.01) postoperatively, whereas the global sagittal balance was not significantly modified (p = 0.07).
Conclusion
Single-level circumferential fusion helps patients reducing their pelvic compensation, but the amount of correction does not allow for complete correction of sagittal imbalance.
doi:10.1007/s00586-011-2124-8
PMCID: PMC3366140  PMID: 22179755
Lumbar fusion; TLIF; Sagittal balance; Degenerative spine
23.  Accuracy of the sagittal vertical axis in a standing lateral radiograph as a measurement of balance in spinal deformities 
European Spine Journal  1998;7(5):408-412.
Sagittal balance of the spine is becoming an important issue in the assessment of the degree of spinal deformity. On a standing lateral full-length radiograph of the spine, the plumb line, or sagittal vertical axis (SVA), can be used to determine the spinal sagittal balance. In this procedure patients have to adopt a habitual standing position with the knees extended during radiographic examination, though it is not known whether small changes in the position of the lower extremities affects the location of the SVA. The purpose of the present study was to investigate the effect of postural change on shifts of the SVA, and to evaluate whether the SVA as measured on a standing full-length lateral radiograph can be used as an accurate measurement of spinal balance in clinical practice. Sagittal balance was analyzed using a patient with ankylosis of the entire spine due to ankylosing spondylitis, to eliminate segmental movement of the spine. A virtual SVA was constructed for seven different standing postures by cross-referring the coordinate systems from a standing full-length lateral radiograph of the spine with video analysis. The horizontal distance between the SVA and the anterior superior corner of the sacrum was measured for each posture. Small changes in the joint angles of the lower extremities affected the SVA significantly, and resulted in the horizontal distance between the SVA and the anterior superior corner of the sacrum varying from –4.5 to +14.9 cm. High correlations were found between this distance and the joint angle of the hip (r = –0.959), knee (r = –0.936), and ankle (r = 0.755) (P < 0.01). The results of the study showed that SVA translations during standing radiographic analysis in a patient with a fixed spine depend on small changes in the hip, knee, and ankle joints. Thus, sagittal spinal (im)balance in ankylosing spondylitis can not be measured from the SVA on a standing lateral full-length radiograph of the spine unless strict procedures are developed to control for the angle of the hip, knee, and ankle joints. The accuracy of the SVA as a measurement of sagittal spinal balance in other spinal deformities, with possible additional segmental movements, therefore remains questionable.
doi:10.1007/s005860050098
PMCID: PMC3611289  PMID: 9840475
Key words Sagittal balance; Sagittal vertical axis; Spinal; deformities; Model; Human posture
24.  The Effect of the Retroperitoneal Transpsoas Minimally Invasive Lateral Interbody Fusion on Segmental and Regional Lumbar Lordosis 
The Scientific World Journal  2012;2012:516706.
Background. The minimally invasive lateral interbody fusion (MIS LIF) in the lumbar spine can correct coronal Cobb angles, but the effect on sagittal plane correction is unclear. Methods. A retrospective review of thirty-five patients with lumbar degenerative disease who underwent MIS LIF without supplemental posterior instrumentation was undertaken to study the radiographic effect on the restoration of segmental and regional lumbar lordosis using the Cobb angles on pre- and postoperative radiographs. Mean disc height changes were also measured. Results. The mean follow-up period was 13.3 months. Fifty total levels were fused with a mean of 1.42 levels fused per patient. Mean segmental Cobb angle increased from 11.10° to 13.61° (P < 0.001) or 22.6%. L2-3 had the greatest proportional increase in segmental lordosis. Mean regional Cobb angle increased from 52.47° to 53.45° (P = 0.392). Mean disc height increased from 6.50 mm to 10.04 mm (P < 0.001) or 54.5%. Conclusions. The MIS LIF improves segmental lordosis and disc height in the lumbar spine but not regional lumbar lordosis. Anterior longitudinal ligament sectioning and/or the addition of a more lordotic implant may be necessary in cases where significant increases in regional lumbar lordosis are desired.
doi:10.1100/2012/516706
PMCID: PMC3419412  PMID: 22919332
25.  The results of anterior fusion and Cotrel-Dubousset-Hopf instrumentation in idiopathic scoliosis 
European Spine Journal  2000;9(6):505-515.
Anterior instrumentation for the correction of scoliotic curves has recently been gaining in popularity. The problems of high mortality and morbidity that were associated with the employment of anterior instrumentation in the first years it was used have now been overcome. Efforts are now being concentrated on increasing the correction rates in the frontal plane and decreasing the kyphotic effect in the sagittal plane. The anterior Cotrel-Dubousset-Hopf (CDH) system is a recently developed instrumentation that has been claimed to decrease the kyphotic effect through the use of double rods. This study aimed to investigate the impact of the anterior CDH system on idiopathic scoliotic curves in frontal and sagittal planes. To this end, 26 idiopathic scoliosis patients treated with the CDH system were followed for a mean period of 32.8 ± 5.3 months. In the frontal plane, Cobb angles of major and secondary curves were measured, and postoperative and final correction rates determined. In the sagittal plane, sagittal contours of both the instrumented region and the thoracic and lumbar regions were measured, and their preoperative, postoperative and final control values were determined. In addition to clinical examination, lateral trunk shift (LT), shift of head (SH) and shift of stable vertebra (SS) were measured in vertebral units (VU), on the preoperative and postoperative radiographs in order to evaluate the effect of the system on trunk balance. It was established that in patients with single flexible thoracolumbar and lumbar curves and those with rigid thoracic curves, the correction rates obtained in the frontal plane were respectively 79.4 ± 14.8%, 68.0 ± 9.4% and 61.5 ± 8.0%, with statistical significance. Their final corrections at the last control were 76.3 ± 17.4%, 56.9 ± 9.1% and 52.3 ± 8.3%, respectively. Although the corrections in the lumbar rigid curves were relatively low, they were still statistically significant. Taking all the patients together, the mean preoperative Cobb angle of the major curves of 67.2°± 20.2° improved to a mean of 28.6°± 21.0°, which was a statistically significant difference (P < 0.05), giving a mean correction rate of 61.2 ± 20.3%. The mean correction loss of major curves in the frontal plane in all patients was 6.0°± 3.8° and the mean final correction rate was 52.6 ± 23.2%. In the sagittal plane, there was a favorable kyphotic effect on the thoracic region of patients with hypokyphosis and lordosis pattern, whilst in patients with kyphotic pattern, this effect was minimal. In patients with a single flexible lumbar curve, kyphotic effect was not observed except in two patients. In these two patients, it was thought that excessive compression force may have been used. As to the patients with a rigid lumbar curve, there was a slight decrease in lumbar lordosis. No postoperative complaints were made about imbalance, and the mean overall correction in LT values was 60.1 ± 21.7%. While preoperatively, the SH and SS values of all patients were over 0.5 VU, postoperatively, 12 patients (46.2%) were completely balanced (SH = 0 VU, SS = 0 VU) and 8 patients (30.8%) were balanced (0 VU < SH and SS < 0.5 VU). The remaining six patients, whose balance values were corrected with statistical significance but were still over 0.5 VU, were found to be the ones with rigid lumbar curves. Implant failure and systemic complications were not noted in the follow-up period. In view of these findings, it was determined that CDH instrumentation achieves significant correction rates in the frontal and sagittal planes, particularly in single flexible lumbar, thoracolumbar and thoracic rigid curves. It was found that the kyphotic effect was minimized with a double rod system. Significant clinical and radiological corrections were achieved in balance values, without any imbalance and decompensation problems.
doi:10.1007/s005860000176
PMCID: PMC3611411  PMID: 11189919
Key words Idiopathic scoliosis; Anterior instrumentation; Surgical treatment; Complications

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