Radiographical spinopelvic parameters and disability in the setting of adult spinal deformity: a prospective multicenter analysis

Sagittal radiographic parameters demonstrate weak correlations with pretreatment patient-reported health-related quality of life measures in symptomatic de novo degenerative lumbar scoliosis: a European multicenter analysis

OBJECTIVE

Previous studies have demonstrated that among patients with adult spinal deformity (ASD), sagittal plane malalignment is poorly tolerated and correlates with suboptimal patient-reported health-related quality of life (HRQOL). These studies included a broad range of radiographic abnormalities and various types of ASD. However, the clinical and radiographic characteristics of de novo degenerative lumbar scoliosis (DNDLS), a subtype of ASD, may influence previously reported correlation strengths. The aim of this study was to correlate sagittal radiographic parameters with pretreatment HRQOL in patients with symptomatic DNDLS.

METHODS

In this multicenter retrospective study of prospectively collected data, 74 patients with symptomatic DNDLS were enrolled based on anteroposterior and lateral 36-inch standing radiographs. Measurements included Cobb angle, coronal imbalance, pelvic incidence (PI), pelvic tilt (PT), lumbar lordosis (LL), sagittal vertical axis (SVA), thoracic kyphosis, pelvic incidence minus lumbar lordosis (PI−LL), T1-pelvic angle, and global tilt. HRQOL questionnaires included the Oswestry Disability Index (ODI), Scoliosis Research Society (SRS-22r), 36-item Short-Form Health Survey, and numeric rating scale (NRS) for back and leg pain. Correlations between radiographic parameters and HRQOL were assessed. Finally, HRQOL and increasing severity of sagittal modifiers (SVA, PI−LL, and PT) were evaluated.

RESULTS

Weak correlations were found between SVA and ODI (r = 0.296, p < 0.05) and PT with NRS back pain and the SRS pain domain (r = −0.260, p < 0.05, and r = 0.282, p < 0.05, respectively). Other sagittal radiographic parameters did not show any significant correlation with HRQOL. No significant differences in HRQOL were found concerning the increasing severity of PT, PI−LL, and SVA.

CONCLUSIONS

While DNDLS is a severe disabling condition, no noteworthy association between clinical and sagittal radiographic parameters was found through this study, demonstrating that sagittal radiographic parameters should not be considered the unique predictor of pretreatment suboptimal health status in this specific group of patients. Future studies addressing classification and treatment algorithms will have to take into account the existing subgroups of ASD.

T1 Slope Minus Cervical Lordosis (TS-CL), the Cervical Answer to PI-LL, Defines Cervical Sagittal Deformity in Patients Undergoing Thoracolumbar Osteotomy

BACKGROUND

Cervical kyphosis and C2-C7 plumb line (CPL) are established descriptors of cervical sagittal deformity (CSD). Reciprocal changes in these parameters have been demonstrated in thoracolumbar deformity correction. The purpose of this study was to investigate the development of CSD, using T1 slope minus cervical lordosis (TS-CL) to define CSD and to correlate TS-CL and a novel global sagittal parameter, cervical-thoracic pelvic angle (CTPA), with CPL.

METHODS

A multicenter, retrospective analysis of patients with thoracolumbar deformity undergoing three-column osteotomy was performed. Preoperative and postoperative cervical parameters were investigated. Linear regression for postoperative values resulted in a CPL of 4 cm corresponding to a TS-CL threshold of 17°. Patients were classified based on postoperative TS-CL into uncompensated (TS-CL > 17°) or compensated cohorts (TS-CL < 17°); the two were compared using an unpaired t test. Logistic regression modeling was used to determine predictors of postoperative CSD.

RESULTS

A total of 223 patients with thoracolumbar deformity (mean age, 57.56 years) were identified. CTPA correlated with CPL (preoperative r = .85, postoperative r = .69). TS-CL correlated with CTPA (preoperative r = .52, postoperative r = .37) and CPL (preoperative r = .52; postoperative r = .37). CSD had greater preoperative CPL (P < .001) and CTPA (P < .001). The compensated cohort had a decrease in TS-CL (from 10.2 to 8.0) with sagittal vertical axis (SVA) correction, whereas the uncompensated had an increase in TS-CL (from 22.3 to 26.8) with all P < .001. Reciprocal change was demonstrated in the compensated group given that CL decreased with SVA correction (r = .39), but there was no such correlation in the uncompensated. Positive predictors of postoperative CSD included baseline TS-CL > 17° (P = .007), longer fusion (P = .033), and baseline CTPA (P = .029).

CONCLUSIONS

TS-CL and CTPA correlated significantly with established sagittal balance measures. Whereas reciprocal change in cervical and thoracolumbar alignment was demonstrated in the compensated cohort, the uncompensated population had progression of their cervical deformities after three-column osteotomy.

CLINICAL RELEVANCE

The balance between TS-CL mirrors the relationship between pelvic incidence minus lumbar lordosis in defining deformities of their respective spinal regions.

Patients with Adult Spinal Deformity with Previous Fusions Have an Equal Chance of Reaching Substantial Clinical Benefit Thresholds in Health-Related Quality of Life Measures but Do Not Reach the Same Absolute Level of Improvement

BACKGROUND

Substantial clinical benefit (SCB) represents a threshold above which patients recognize substantial improvement and represents a rational target for defining clinical success. In adult spinal deformity (ASD) surgery, previous fusions may impact outcomes after deformity correction.

OBJECTIVE

To investigate the impact of previous spinal fusion on the likelihood of reaching SCB thresholds for 2-year health-related quality of life (HRQOL) after ASD surgery.

METHODS

We conducted a retrospective review comparing baseline demographic, HRQOL, and radiographic features for patients with ASD undergoing primary versus revision procedures. The primary outcome measure was reaching SCB threshold in Oswestry Disability Index (ODI), SF-36 Physical Component Summary (PCS), and back and leg pain (numeric rating scale). Secondary outcomes included absolute and change scores in ODI, PCS, and back and leg pain.

RESULTS

In total, 332 patients achieved 2-year follow-up (228 primary; 104 revision cases). Those undergoing revision surgery had similar demographic features (age 58.3/55.9, female 80.8%/82.9%) to patients undergoing primary surgery. They had worse baseline HRQOL (ODI 48.5/41.2, PCS 29.5/33.4, back 7.5/7.0, and leg pain 4.9/4.3; P < 0.001) and radiographic deformity (sagittal vertical axis 111.4/45.1, lumbopelvic mismatch 26.7/11.0, pelvic tilt 29.5/21.0; P < 0.0001). Nevertheless, the number of patients who reached SCB for ODI (38.3/36.3%), PCS (48.5/53.4%), back (53.1/60.5%), and leg pain numeric rating scale (28.6/36.9%) did not significantly differ. Revision patients had worse 2-year HRQOL for all measures.

CONCLUSIONS

Patients undergoing revision surgery have worse baseline HRQOL and deformity. Although they do not achieve the same absolute level of 2-year HRQOL outcome, they have a similar likelihood of reaching SCB threshold for improvement in 2-year HRQOL.

Is anatomic acetabular orientation related to pelvic morphology? CT analysis of 150 healthy pelvises

BACKGROUND

Links between sagittal spinal alignment and acetabular orientation attract considerable research attention with the goal of optimising prosthetic cup position. However, whether pelvic incidence (PI) is related to anatomic acetabular orientation remains unknown. We therefore conducted a radiological study with the following objectives: to look for correlations between PI and anatomic acetabular parameters; to describe the sacro-pubic angle (SPA), defined by fixed bony pelvic landmarks, and its relations with acetabular anteversion; and to determine whether anatomical parameters (PI and SPA) correlate with demographic characteristics.

HYPOTHESIS

PI correlates with anatomical acetabular parameters.

MATERIALS AND METHODS

We conducted a computed tomography (CT) study of the pelvises of 150 patients free of degenerative disease. Three parameters were measured: anatomic acetabular orientation in the Lewinnek reference plane, PI, and the SPA subtended by the line connecting the midpoint of the sacral endplate to the pubic symphysis and the anterior pelvic plane. Statistical tests were performed to look for correlations among these parameters.

RESULTS

Intra-observer and inter-observer reproducibility was considered highly satisfactory (inter-class correlation coefficient, >86% and >82%, respectively). Mean PI was 58.6°±10.2° (range, 32.8°-97.6°), with no significant differences between genders or across age groups. Mean SPA was 34.7°±5.5° (range, 18.3°-49.8°). Mean anatomic acetabular anteversion (AAA) was greater in females (23.4°; range, 11.5°-34.5°) than in males (20°; range, 7.5°-34.5°) (P<0.001). PI did not correlate with any of the acetabular parameters (PI/AAA, r=0.8 and P=0.33; PI/acetabular inclination on the horizontal, r=-0.96 and P=0.24). SPA correlated significantly with both PI (r=0.33 and P<0.001) and AAA (r=0.33 and P<0.001).

DISCUSSION

This CT study of normal pelvises showed that AAA was significantly greater in females and that SPA correlated significantly with both PI and acetabular anteversion. SPA could serve to define the "theoretical" AAA of each individual patient and could thus be incorporated into surgical planning protocols or intra-operative guidance methods for hip replacement surgery.

LEVEL OF EVIDENCE

IV, retrospective study with no control group.

How does sagittal imbalance affect the appropriateness of surgical indications and selection of procedure in the treatment of degenerative scoliosis? Findings from the RAND/UCLA Appropriate Use Criteria study

BACKGROUND CONTEXT

Degenerative lumbar scoliosis (DLS) is often associated with sagittal imbalance, which may affect patients' health outcomes before and after surgery. The appropriateness of surgery and preferred operative approaches has not been examined in detail for patients with DLS and sagittal imbalance.

PURPOSE

The goals of this article were to describe what is currently known about the relationship between sagittal imbalance and health outcomes among patients with DLS and to determine how indications for surgery in patients with DLS differ when sagittal imbalance is present.

STUDY DESIGN/SETTING

This study included a literature review and an expert panel using the RAND/University of California at Los Angeles (UCLA) Appropriateness Method.

METHODS

To develop appropriate use criteria for DLS, researchers at the RAND Corporation recently employed the RAND/UCLA Appropriateness Method, which involves a systematic review of the literature and multidisciplinary expert panel process. Experts reviewed a synopsis of published literature and rated the appropriateness of five common operative approaches for 260 different clinical scenarios. In the present work, we updated the literature review and compared panelists' ratings in scenarios where imbalance was present versus absent. This work was funded by the Collaborative Spine Research Foundation, a group of surgical specialty societies and device manufacturers.

RESULTS

On the basis of 13 eligible studies that examined sagittal imbalance and outcomes in patients with DLS, imbalance was associated with worse functional status in the absence of surgery and worse symptoms and complications postoperatively. Panelists' ratings demonstrated a consistent pattern across the diverse clinical scenarios. In general, when imbalance was present, surgery was more likely to be appropriate or necessary, including in some situations where surgery would otherwise be inappropriate. For patients with moderate to severe symptoms and imbalance, a deformity correction procedure was usually appropriate and frequently necessary, except in some patients with severe risk factors for complications. Conversely, procedures that did not correct imbalance, when present, were usually inappropriate.

CONCLUSIONS

Clinical experts agreed that sagittal imbalance is a major factor affecting both when surgery is appropriate and which type of procedure is preferred among patients with DLS.

The Impact of Spino-Pelvic Alignment on Total Hip Arthroplasty Outcomes: A Critical Analysis of Current Evidence

BACKGROUND

In this review, we (1) evaluated the effect of adult spine deformity (ASD) and its surgical correction on patients who had a total hip arthroplasty (THA); (2) evaluated the outcomes of THA in patients who have had previous spinal fusion; and (3) we presented an algorithm on how to surgically address patients who simultaneously require THA and ASD correction.

METHODS

A comprehensive literature search was conducted. Our final analysis included 14 studies. Overall, there were 3 studies that reported on the impact of ASD on THA outcomes, 6 studies reported on the effect of ASD correction on THA outcomes, and 5 studies reported on the effect of spinal fusion on THA outcomes.

RESULTS

Patients with concurrent ASD and THA are at increased risk of THA dislocations and revisions with studies reporting a compiled 2.9% dislocation rate in 1167 patients. Patients who underwent ASD correction demonstrated a post-operative reduction of acetabular anteversion (mean reduction range 4.96°-11.2°, P < .001) and tilt (mean -7° ± 10°, P < .001). In THA patients with concurrent lumbosacral fusion, dislocation rates ranged between 3% at 1 year and 7.5% at 2 years compared to 0.4%-2.1% dislocation rates in matching cohorts (P < .001).

CONCLUSION

Spine balance can alter THA outcomes, but the exact mechanism is yet to be elucidated. We aimed at bridging the gap between hip and spine surgeons with an up-to-date analysis of the best available evidence and presented an algorithm for approaching patients who may simultaneously need ASD correction and THA.

Are There Age- and Sex-related Differences in Spinal Sagittal Alignment and Balance Among Taiwanese Asymptomatic Adults?

BACKGROUND

Sagittal spinopelvic balance and proper sagittal alignment are important when planning corrective or reconstructive spinal surgery. Prior research suggests that people from different races and countries have moderate divergence; to the best of our knowledge, the population of Taiwan has not been studied with respect to this parameter.

QUESTIONS/PURPOSES

To investigate normal age- and sex-related differences in whole-spine sagittal alignment and balance of asymptomatic adults without spinal disorders.

METHODS

In this prospective study, we used convenience sampling to recruit asymptomatic volunteers who accompanied patients in the outpatient orthopaedic department. One hundred forty males with a mean age of 48 ± 19 years and 252 females with a mean age of 53 ± 17 years underwent standing lateral radiographs of the whole spine. For analysis, participants were divided in three groups by age (20 to 40 years, 41 to 60 years, and 61 to 80 years) and analyzed by sex (male and female). The following eight radiologic parameters were measured: sacral slope, pelvic tilt, pelvic incidence, thoracic kyphosis, lumbar lordosis, cervical lordosis, C2-C7 sagittal vertical axis, and C7-S1 sagittal vertical axis. Three observers performed estimations of the sagittal parameters twice, and the intraclass correlation coefficients for inter- and intraobserver variability were 0.81 and 0.83.

RESULTS

The mean pelvic incidence was 49° ± 12°; lumbar lordosis was smaller in the group that was 61 to 80 years old than in the groups that were 20 to 40 years and 41 to 60 years (95% CI of the difference, 4.50-13.64 and 1.00- 9.60; p < 0.001), while cervical lordosis was greater in the 61 to 80 years age group than the other two groups (95% CI of the difference, -14.64 to -6.57 and -11.57 to -3.45; p < 0.001). The mean C7-S1 sagittal vertical axis was 30 ± 29 mm, and there was no difference among the three groups and between males and females. Pelvic tilt was greater in the group 61 to 80 years old than the 20 to 40 years and 41 to 60 years age groups (95% CI of the difference, -10.81 to -5.42 and -7.15 to -2.08; p < 0.001), while sacral slope was larger in 61 to 80 years age group than in the 41 to 60 years group (95% CI of the difference, 0.79-6.25; p = 0.006). C7 slope was greater in 61 to 80 years age group than in the 20 to 40 years group (95% CI of the difference, -7.49 to -1.26; p = 0.002) and larger in 41 to 60 years age group than in 20 to 40 years group (95% CI of the difference, -6.31 to -0.05; p = 0.045). C2-C7 sagittal vertical axis was greater in males than in females (95% CI of the difference, 2.84-7.74; p < 0.001). C7 slope was negatively correlated with thoracic kyphosis (95% CI of the difference, -0.619 to 0.468; p < 0.001) and lumbar lordosis (95% CI of the difference, -0.356 to -0.223; p < 0.001), and positively correlated with pelvic incidence (95% CI of the difference, 0.058- 0.215; p < 0.001) and cervical lordosis (95% CI of the difference, 0.228 - 0.334; p < 0.001).

CONCLUSIONS

Normal values of the spinopelvic sagittal parameters vary by age and sex in Taiwanese individuals.

CLINICAL RELEVANCE

Pelvic incidence and sacral slope observed in this population seemed smaller than those reported in other studies of white populations; this seems important when considering spine surgery in Taiwanese patients. Future studies should include collection of whole body sagittal parameters of larger and more-diverse populations, and assessments of patients with symptomatic spinal disorders.

Predicting Perioperative Complications in Adult Spinal Deformity Surgery Using a Simple Sliding Scale

STUDY DESIGN

A retrospective database study.

OBJECTIVE

The aim of this study was to develop and validate a sliding scale for predicting perioperative complications associated with adult spinal deformity (ASD) surgery.

SUMMARY OF BACKGROUND DATA

ASD surgery can have high perioperative complication rates, which is associated with increased morbidity and mortality.

METHODS

Data on consecutive ASD patients undergoing posterior corrective surgery over a 6-year interval were collected from a prospective database. The patients' preoperative general condition, surgical status, and perioperative complications occurring within 30 days of surgery were analyzed and independent predictors were determined using multivariable logistic regression analysis. We made the sliding scale using cut-off values from receiver operating curve analysis and validated the performance of this model.

RESULTS

Three hundred four patients were included with a mean age of 62.9 years. One hundred eight patients (35.5%) were affected by at least one perioperative complication with a total of 195 perioperative complications, including neurological (12.8%), excessive blood loss (11.2%), delirium (11.2%), and infection (3.6%). Total independent predictors were age [odds ratio (OR): 1.042], operation time (OPT) (OR: 2.015), and estimated blood loss (EBL) (OR: 4.885) with cut-off values of approximately 70 years, 6 hours, and 2000 mL, respectively. Fusion of ≥10 segments (OR: 2.262), three-column osteotomy (OR: 1.860), current use of antihypertensive (OR: 2.595) and anticoagulant (OR: 7.013), and body mass index (OR: 1.160) were risk factors for neurological complications, infection, and deep vein thrombosis/pulmonary thrombosis. Our proposed sliding scale had a sensitivity of 91%, specificity of 58.1%, and the incidence of perioperative complication in the validation dataset was smaller than that without this scale (P ≤ 0.05).

CONCLUSION

Patients' age, current medication, and degenerative pathology might be independent preoperative as well as operative predictors. An age and comorbidities based sliding scale with classifications of OPT and EBL may be useful for risk prediction in ASD surgery.

LEVEL OF EVIDENCE

3.

Negative Sagittal Balance Following Adult Spinal Deformity Surgery

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

Elucidate negative sagittal balance following adult spinal deformity surgery.

METHODS

We conducted a retrospective review of adult spinal deformity patients who underwent long fusion (>5 levels) to the sacrum by a single surgeon at a single institution between 2011 and 2015. Patients were divided into cohorts of postoperative sagittal vertical axis (SVA) <-10 mm, between -10 and +10 mm, or >+10 mm, denoted as groups 1, 2, and 3, respectively. Univariate analysis compared preoperative factors between the groups, and a multivariable logistic regression model was used to determine independent risk factors for developing a negative sagittal balance (SVA<-10 mm) following adult spinal deformity correction.

RESULTS

We reviewed 8 patients in group 1, 9 patients in group 2, and 25 patients in group 3. The average postoperative SVA for group 1, group 2, and group 3 were -30.99, +3.67, and +55.56 mm, respectively. There was a trend toward higher upper-instrumented vertebra (UIV) in group 1 (T2) compared with group 2 (T10) and group 3 (T9) (P = .05). A trend toward lower preoperative SVA in groups 1 and 2 compared with group 3 was also seen (+53.36 vs +71.73 vs +122.80 mm) (P = .06). Finally, we found a trend toward lower body mass index in group 1 compared with groups 2 and 3 (24.71 vs 25.92 vs 29.33 kg/m²) (P = .07). Based on multivariable regression, higher UIV was found to be a statistically significant independent predictor for developing a postoperative negative sagittal balance of <-10 mm (P = .02, odds ratio = 0.67).

CONCLUSIONS

Our results demonstrate that a higher UIV may predispose patients undergoing adult spinal deformity correction to have a postoperative negative sagittal balance.

Spinopelvic Changes Based on the Simplified SRS-Schwab Adult Spinal Deformity Classification: Relationships With Disability and Health-Related Quality of Life in Adult Patients With Prolonged Degenerative Spinal Disorders

STUDY DESIGN

Cross-sectional, observational study.

OBJECTIVE

To study the occurrence of sagittal malalignment, the adaptability of a simplified sagittal modifiers grading of the Scoliosis Research Society (SRS)-Schwab adult spinal deformity (ASD) classification, and the deformity-specific SRS questionnaire version 30 (SRS-30) in an unselected adult cohort with symptomatic degenerative spinal disorders.

SUMMARY OF BACKGROUND DATA

The sagittal modifiers of the SRS-Schwab ASD classification correlate with health-related quality of life (HRQoL) measures in patients with ASD. The deformities and disabilities caused by sagittal malalignment in patients with common degenerative spinal disorders of multiple etiologies are rarely studied. A simplified and categorizing version of the SRS-Schwab ASD classification in relation to the Oswestry Disability Index (ODI) and the SRS-30 outcomes has not yet been developed.

METHODS

We recruited 874 consecutive patients with degenerative spinal disorders between March 2013 and February 2014. Full spine radiographs were taken and the patients divided into sagittal deformity severity groups: mild or none, moderate, and marked deformity. Participants completed the ODI, SRS-30, and a general health questionnaire.

RESULTS

We included 637 patients in the analysis. The severity of sagittal deformity was mild or none in 407 (63.9%) patients, moderate in 159 (25.0%), and marked in 71 (11.1%). Linearity across the modifier grades and deformity classes was found for ODI total score (P = 0.033), and the function/activity (P = 0.004) and self-image/appearance (P = 0.030) domains of the SRS-30. Age, body mass index, duration of symptoms, and the use of painkillers increased while physical activity, working, and educational status decreased significantly with deformity severity.

CONCLUSION

Sagittal spinopelvic malalignment is significantly related to deterioration of the ODI and the SRS-30 in symptomatic adults with degenerative spinal disorders. The SRS-Schwab classification sagittal modifiers categorized into three groups is a practical tool to detect various clinically significant grades of deformity in a cohort with no recognized ASD.

LEVEL OF EVIDENCE

3.

Alphabet Soup: Sagittal Balance Correction Osteotomies of the Spine-What Radiologists Should Know

Global sagittal malalignment has been demonstrated to have correlation with clinical symptoms and is a key component to be restored in adult spinal deformity. In this article, various types of sagittal balance-correction osteotomies are reviewed primarily on the basis of the 3 most commonly used procedures: Smith-Petersen osteotomy, pedicle subtraction osteotomy, and vertebral column resection. Familiarity with the expected imaging appearance and commonly encountered complications seen on postoperative imaging studies following correction osteotomies is crucial for accurate image interpretation.

Acquired spondylolysis and spinopelvic sagittal alignment

Acquired spondylolysis represents an uncommon complication of spine surgery, of an unknown incidence and etiology. We studied patients presenting this rare entity, with the purpose to investigate the incidence, imaging findings, patients' clinical characteristics, as well as to provide an interpretation of the mechanisms that may lead to this phenomenon. The presented working hypothesis, regarding etiology, suggests that there is a relation between variations in spinopelvic sagittal alignment and acquired spondylolysis. Between January 2010 and January 2015, six patients presented spondylolysis after short-segment transforaminal lumbar interbody fusion, at a mean time of 43 months after surgery. The preoperative intactness and postoperative defect of pars interarticularis were documented with computed tomography scans in all patients. Standard radiographical spinopelvic parameters were measured before and after surgery. The optimum values of lumbar lordosis (LL) and pelvic incidence minus lumbar lordosis modifier (PI-LL mismatch) were calculated as well. The incidence of acquired spondylolysis was 0.95% among patients with short-segment lumbar fusion. Patients presented high-grade PI with a vertically orientated sacral endplate, while LL was found 9° greater and PI-LL mismatch 9° lower than the respective optimum values, indicating a non-harmonized alignment. In conclusion, acquired spondylolysis, though rare, may occur in patients with high-grade PI and sacral slope, and suboptimal spinopelvic sagittal alignment after lumbar spine surgery, thereby highlighting the importance of detailed preoperative planning in spine surgery, along with the study of sagittal balance.

Under Correction of Sagittal Deformities Based on Age-adjusted Alignment Thresholds Leads to Worse Health-related Quality of Life Whereas Over Correction Provides No Additional Benefit

STUDY DESIGN

Retrospective review of prospectively-collected database.

OBJECTIVE

This study aims to compare 2-year clinical outcomes of patients who underwent surgical reconstructions based on their achievement to age-adjusted alignment ideals.

SUMMARY OF BACKGROUND DATA

Recent research in sagittal plane has proposed age-adjusted alignment thresholds. However, the impact of these thresholds on postoperative health-related quality of life (HRQOL) is yet to be investigated.

METHODS

Patients were included if they were more than 18-years old and underwent surgical correction of adult spinal deformity with a complete 2-year follow-up. Patients were stratified into three groups based on achievement of age-adjusted thresholds in pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), and sagittal vertical axis (SVA). First group included patients who reached the exact age-adjusted threshold ± 10 years (MATCHED), other two groups included patients who were over corrected (OVER), and under corrected (UNDER). Clinical outcomes including actual value and offset from age-adjusted Oswestry Disability Index, Short-Form-36 (SF-36) -physical component summary, and Scoliosis Research Society-22r (SRS-22r) were compared between groups at 2 years follow-up.

RESULTS

A total of 343 patients (mean, 57 yrs and 83% females) were included. Sagittal profile of the population was: PT = 23.6°, SVA = 65.8 mm, and PI-LL = 15.6°. At 2-year follow-up, there was significant improvement in all sagittal modifiers with 25.7%, 24.3%, and 33.1% of the patients matching their age alignment targets in terms of PT, PI-LL, and SVA, respectively. For PT and PI-LL, the three groups (MATCHED, OVER, and UNDER) had comparable values and offsets from age-adjusted patient reported outcome. However, for SVA groups, patients in UNDER had significantly worse HRQOL than the two other groups. Patients in PT, PI-LL, and SVA UNDER groups were significantly younger than the other groups, P < 0.05.

CONCLUSION

At 2 years after adult spinal deformity surgical treatment, only 24.3% to 33.1% of the patients reached age-adjusted alignment thresholds. Those under corrected in SVA demonstrated worse clinical outcomes. No significant improvements were found between matched and overcorrected patients, with overcorrection being an established risk for proximal junctional kyphosis. These results further emphasize the need for patient specific operative planning.

LEVEL OF EVIDENCE

3.

Factors Associated with Neck and Shoulder Pain in Volunteers

Introduction

The aims of the present study were 1) to examine the association between neck and shoulder pain (NSP) and lifestyle in the general population and 2) to examine if sagittal spino-pelvic malalignment is more prevalent in NSP.

Methods

A total of 107 volunteers (mean age, 64.5 years) were recruited in this study from listings of resident registrations in Kihoku region, Wakayama, Japan. Feeling pain or stiffness in the neck or shoulders was defined as an NSP. The items studied were: 1) the existence or lack of NSP and their severity (using VAS scale), 2) Short Form-36 (SF-36), 3) Self-Rating Questionnaire for Depression (SRQ-D), 4) Pain Catastrophizing Scale (PCS), 5) a detailed history consisting of 5 domains as being relevant to the psychosocial situation of patients with chronic pain, 6) A VAS of pain and numbness to the arm, and from thoracic region to legs. The radiographic parameters evaluated were also measured. Participants with a VAS score of 40 mm or higher and less were divided into 2 groups. Association of SF-36, SRQ-D, and PCS with NSP were assessed using multiple regression analysis.

Results

In terms of QoL, psychological assessment and a detailed history, bodily pain in SF-36, SRQ-D, and family stress were significantly associated with NSP. A VAS of pain and numbness to the arm, and from thoracic region to legs, was significantly associated with NSP. There were no statistical correlations between the VAS and radiographic parameters of the cervical spine. Among the whole spine sagittal measurements, multiple logistic regression analysis showed that sacral slope (SS) and sagittal vertical axis (SVA) were significantly associated with NSP.

Conclusion

In this study, we showed the factors associated with NSP. Large SS and reduced SVA were significantly associated with NSP, while cervical spine measurements were not.

Improvement in Sagittal Balance After Decompression Surgery without Fusion in Patients with Degenerative Lumbar Stenosis: Clinical and Radiographic Results at 1 Year

OBJECTIVE

To evaluate modifications in static spinal status after posterior decompression surgery without fusion in patients with symptomatic central canal stenosis.

METHODS

From November 2014 to May 2016, 72 patients who underwent isolated decompression for lumbar spinal stenosis were enrolled prospectively in this single-center study. All of the patients had lateral full-body x-ray scans with the EOS system (EOS Imaging, Paris, France) before surgery and after 12 months of follow-up. Patients were classified into 3 groups according to their preoperative sagittal vertical axis (<50 mm, ≥50 mm, and <100 mm, ≥100 mm).

RESULTS

SVA decreased significantly (SVA preoperative: 72.3 ± 43.1; SVA postoperative: 48.3 ± 46.8. P < 0.001). Lumbar lordosis increased significantly from 41.9 ± 13.4 in the preoperative period to 46.5 ± 14.8 at the last follow-up (P < 0.001). In the imbalance groups, the mean postoperative SVA decreased significantly compared with preoperative SVA (P = 0.004). Surgery led to a significant increase in lumbar lordosis in the 3 groups (P < 0.05). Nonetheless, a certain degree of residual imbalance persisted in the major imbalance group. In all of the groups, decompression surgery led to a significant improvement in clinical scores (P < 0.05).

CONCLUSIONS

Our study showed an improvement in sagittal balance and lumbar lordosis after decompression surgery without fusion, even in patients with a preoperative SVA >100 mm. However, a certain degree of sagittal imbalance may persist after surgery in patients with major initial imbalance (SVA >100 mm). Nonetheless, after surgery, these patients experienced a clinical benefit comparable with that in the other groups.

Compensatory mechanism of the spine after corrective surgery without lumbar-sacral fixation for traumatic thoracolumbar kyphotic spine deformity

BACKGROUND

It remains unclear whether long fusion including lumbar-sacral fixation is needed in corrective surgery to obtain good global sagittal balance (GSB) for the treatment of traumatic thoracolumbar kyphotic spine deformity. The purposes of this study were to evaluate compensatory mechanism of the spine after corrective surgery without lumbar-sacral fixation and to evaluate the parameters affecting the achievement of good GSB post-operatively.

METHODS

Twenty (20) subjects requiring corrective surgery (distal end of fixation was L3) were included in this study. The radiographic parameters were measured pre-operatively and at one month after surgery. Sagittal Vertical Axis (SVA), Lumber Lordosis angle altered by fracture (fLL), Thoracic Kyphosis angle altered by fracture (fTK), Pelvic Tilt (PT), Sacral Slope (SS), Pelvic Incidence (PI), Segmental Lumbar Lordosis (sLL: L3-S/L4-S), and local kyphotic angle were measured. The correlation between correction of local kyphotic angle (CLA) and the change in radiographic parameters was evaluated. Post-operatively, subjects with SVA<50 mm and PI-fLL<10°were regarded as the "good GSB group (G group). The radiographic parameters affecting the achievement of G group were statistically evaluated.

RESULTS

fLL, sLL:L3-S and sLL:L4-S were decreased indirectly because the local kyphosis was corrected directly (CLA: 26.5 ± 8.6°) (P < 0.001). CLA and the change in fLL showed significant correlation (r = 0.821), the regression equation being: Y = -0.63X+3.31 (Y: The change in fLL, X: CLA). The radiographic parameters significantly affecting the achievement of G group were: SVA, PT, PI-fLL, sLL: L3-S, and sLL: L4-S (P < 0.01).

CONCLUSION

The main compensatory mechanism was the decrease of lordosis in the lumbar spine. fLL was decreased to approximately 60% of CLA after surgery. SVA was not corrected by the compensatory mechanism.

Differences in Fundamental Sagittal Pelvic Parameters Based on Age, Sex, and Race

STUDY DESIGN

This is a retrospective cohort study.

OBJECTIVE

To determine whether age, sex, and race have independent effects on sagittal pelvic parameters.

SUMMARY OF BACKGROUND DATA

Pelvic parameters and sagittal balance correlate with health-related quality of life and are important for patient assessment and surgical planning. Age, sex, and race are 3 unalterable patient factors that may influence pelvic morphology.

METHODS

We conducted a retrospective review of consecutive adult patients who presented to our radiology practice between 2010 and 2015 and had a standing, lateral lumbosacral radiograph. Any patients without both femoral heads and L1-S1 visible on the radiograph, and any patients presenting with traumatic injury, coronal deformity, prior instrumentation, spondylolisthesis, or neoplasm of the spine were excluded. Univariate analysis determined differences in measurements among African American, white, and Hispanic races, as well as between male and female sexes. Correlation analysis between age and different measurements was also conducted. Multivariable regression was then used to determine the independent effect of age, sex, and race on pelvic parameters.

RESULTS

We investigated 1801 adults (older than 18 y) and 1246 had a recorded race. There were 1165 women, 636 men, 525 whites, 404 African Americans, and 317 Hispanics. Multivariable regression demonstrated a statistically significant increase in pelvic tilt (PT), pelvic incidence (PI), and pelvic incidence-lumbar lordosis (PI-LL) with aging, and statistically significant decrease in sacral slope (SS) and LL with aging. Women had a statistically greater LL than men. African Americans had a statistically smaller PT and greater SS and PI-LL relative to whites, while Hispanics had a statistically smaller PT and PI-LL, and a statistically greater SS and LL relative to whites.

CONCLUSIONS

Pelvic parameters were different between sexes, among races, and changed with age. These findings are important for patient assessment and preoperative planning to obtain optimal sagittal balance.

LEVEL OF EVIDENCE

Level 3.

Using spinopelvic parameters to estimate residual lumbar lordosis assuming previous lumbosacral fusion-a study of normative values

BACKGROUND CONTEXT

Pelvic incidence (PI)=pelvic tilt (PT)+sacral slope (SS) is an established trigonometric equation which can be expanded from studying the fixed pelvis with the spine to a fixed spinopelvic complex with the remnant spine, in scenarios of spinopelvic fusion or ankylosis. For a fixed spinopelvic complex, we propose the equation termed: lumbar incidence (LI)=lumbar tilt (LT)+lumbar slope (LS).

PURPOSE

This study aimed to establish reference values for LI, LT, and LS at each lumbar vertebral level, and to show how LI can be used to determine residual lumbar lordosis (rLL).

STUDY DESIGN

This is a cross-sectional study of prospectively collected data, conducted at a single academic tertiary health-care center.

PATIENT SAMPLE

The study included 53 healthy patients aged 19-35 with first episode mechanical low back pain for a period of <3 months. Patients with previous spinal intervention, those with known or suspected spinal pathologies, and those who were pregnant, were excluded.

OUTCOME MEASURES

Radiological measurements of LI, LT, LS, and rLL.

METHODS

All patients had full-body lateral standing radiographs obtained via a slot scanner. Basic global and regional radiographic parameters, spinopelvic parameters, and the aforementioned new parameters were measured. LI was correlated with rLL at each level by plotting LI against rLL on scatter plots and drawing lines-of-best-fit through the datapoints.

RESULTS

The mean value of L5I was 22.82°, L4I was 6.52°, L3I was -0.92°, L2I was -5.56°, and L1I was -5.95°. LI turns negative at L3, LS turns negative at the L3/L4 apex, and LT remains positive throughout the lumbar spine. We found that the relationship of LI with its corresponding rLL follows a parabolic trend. Thus, rLL can be determined from the linear equations of the tangents to the parabolic lumbar spine. We propose the LI-rLL method for determining rLL as the LI recalibrates via spinopelvic compensation post instrumentation, and thus the predicted rLL will be based on this new equilibrium, promoting restoration of harmonized lordosis. The rLL-to-LI ratio is a simplified, but less accurate, method of deriving rLL from LI.

CONCLUSIONS

This study demonstrates the extended use of PI=PT+SS proposed as LI=LT+LS. These new spinopelvic reference values help us better understand the position of each vertebra relative to the hip. In situations when lumbar vertebrae are fused or ankylosed to the sacrum to form a single spinopelvic complex, LI can be used to determine rLL, to preserve spinal harmony within the limits of compensated body balance.

Influence of Distal Fusion Level on Sagittal Spinopelvic and Spinal Parameters in the Surgical Management of Adolescent Idiopathic Scoliosis

Study Design

Retrospective analysis of adolescent idiopathic scoliosis.

Purpose

This study aimed to investigate the influence of distinct distal fusion levels on spinopelvic parameters in patients with adolescent idiopathic scoliosis (AIS) who underwent posterior instrumentation and fusion surgery.

Overview of Literature

The distal fusion level selection in treatment of AIS is the one of milestone to effect on surgical outcome. Most of the paper focused on the coronal deformity correction and balance. The literature have lack of knowledge about spinopelvic changing after surgical treatment and the relation with distal fusion level. We evaluate the spinopelvic and pelvic parameter alteration after fusion surgery in treatment of AIS.

Methods

A total of 100 patients with AIS (88 females and 12 males) were retrospectively reviewed. Patients were assigned into the following three groups according to the distal fusion level: lumbar 2 (L2), lumbar 3 (L3), and lumbar 4 (L4). Using a lateral plane radiograph of the whole spine, spinopelvic angular parameters such as thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) were radiologically assessed.

Results

The mean age was 15±2.4 years, and the mean follow-up period was 24.27±11.69 months. Regarding the lowest instrumented vertebra, patients were categorized as follows: 30 patients in L2 (group 1), 40 patients in L3 (group 2), and 30 patients in L4 (group 3). TK decreased from 36.60±13.30 degrees preoperatively to 26.00±7.3 degrees postoperatively in each group (p=0.001). LL decreased from 52.8±9.4 degrees preoperatively to 44.30±7.50 degrees postoperatively (p=0.001). Although PI showed no difference preoperatively among the groups, it was statistically higher postoperatively in group 3 than in the other groups (p<0.05). In addition, in group 2, PI decreased from 50.60±8.74 degrees preoperatively to 48.00±6.84 degrees postoperatively (p=0.027). SS decreased from 35.20±6.40 degrees preoperatively to 33.40±5.80 degrees postoperatively (p=0.08, p>0.05). However, mean SS was significantly higher in group 3 (p=0.042, p<0.05). PT decreased from 15.50±7.90 degrees preoperatively to 15.2±7.10 degrees postoperatively. The positive relationship (28.5%) between LL and PI measurements was statistically significant (r=0.285; p=0.004, p<0.01). Furthermore, the positive relationship (36.5%) between LL and SS measurements was statistically significant (r=0.365; p=0.001, p<0.01).

Conclusions

When the distal instrumentation level in AIS surgery is below L3, a significant change in PT and SS (pelvic parameters) is anticipated.

Radiological and functional outcomes of high-grade spondylolisthesis treated by intrasacral fixation, dome resection and circumferential fusion: a retrospective series of 20 consecutive cases with a minimum of 2 years follow-up

PURPOSE

Major concern during surgery for high-grade spondylolisthesis (HGS) is to reduce lumbosacral kyphosis and restore sagittal alignment. Despite the numerous methods described, lumbosacral fixation in HGS is a challenging technique associated with high complication rate. Few series have described outcomes and most of the results are limited to lumbosacral correction without global sagittal alignment analysis. This study aims at analyzing clinical and radiological outcomes of HGS patients treated with intrasacral rods on full spine radiographs.

METHODS

HGS patients (Meyerding III or higher) operated between 2004 and 2014 were reviewed. All patients underwent full spine stereoradiographic images. After L5 and S1 decompression, reduction and circumferential fusion with intrasacral rod fixation and fusion up to L4 were performed under fluoroscopy. The entry points for S1 screws were located 3-5 mm above and 5 mm lateral to the first sacral hole, toward the promontory. The two short distal fusion rods were then positioned into the sacrum guided by anteroposterior fluoroscopy using Jackson's technique. Then, sacral dome resection was performed and a PEEK cage was impacted in L5S1 after reduction. Postoperatively, the hip and knee were kept flexed at 45° for 1 week and extended progressively. Preoperative, 3 months postoperative and last follow-up (> 2 years minimum) clinical and radiographic data were collected. Sagittal parameters included lumbosacral angle (LSA), olisthesis, T1 spinopelvic inclination (T1SPi) and spinopelvic parameters.

RESULTS

20 HGS patients were included (8 ptosis, 5 Meyerding IV). The mean age was 14 years. At final FU (7.2 years ± 3), LSA kyphosis and olisthesis were reduced (65° ± 14 vs 99° ± 11, p < 0.001 and 81% ± 19 vs 45% ± 18, p < 0.001, respectively). While L1L5 lordosis decreased, T1T12 kyphosis increased. At FU, global alignment with T1SPi was - 6° ± 3. No significant loss of correction was observed. Regarding complications, ten patients presented transient L5 motor deficit that occurred when patients were put in standing position. However, all recovered before 3 months postoperatively.

CONCLUSION

Intrasacral rod fixation appears to be an effective technique to correct LSA kyphosis, compensatory hyperlordosis and restore global sagittal alignment with a postoperative T1SPi corresponding to the value of the asymptomatic subject and achieve fusion. However, it remains a demanding technique with high risk of transient neurologic complications.

Prevalence and key radiographic spinal malalignment parameters that influence the risk for gastroesophageal reflux disease in patients treated surgically for adult spinal deformity

BACKGROUND

Gastroesophageal reflux disease (GERD) is a factor that has a significant negative impact on the quality of life (QoL). Vertebral fractures and/or spinal malalignment may influence the frequency of GERD. However, the epidemiology and pathology of GERD in patients with adult spinal deformity (ASD) are still largely unknown. To establish the optimal surgical strategy for GERD in patients treated surgically for ASD, we sought to clarify the GERD prevalence, determine radiographically which spinal malalignment parameters influence GERD risk, and evaluate GERD improvement postoperatively.

METHODS

Seventy-one consecutive patients with ASD who were treated with thoracolumbar corrective surgery and followed up for at least 1 year were enrolled. GERD was diagnosed by a gastroenterologist based on proton pump inhibitor medication response and/or an FSSG score > 8 points. Full-length lateral radiographs in a standing posture and in a supine, fulcrum backward-bending (FBB) position were taken preoperatively and 1 year postoperatively, and radiographic parameters were obtained. Correlations between radiographic parameters and FSSG scores were determined by Pearson's correlation coefficient. Multivariate logistic regression analyses were performed to evaluate the odds ratio (OR) with a 95% confidence interval (95% CI) for potential risk factors for GERD.

RESULTS

Patients were classified into two groups based on GERD symptoms, with 37 (52%) in the GERD+ group. Thoracolumbar kyphosis (TLK) in the FBB position was significantly more common in the GERD+ versus the GERD- group. Multivariate logistic regression analysis showed that lumbar lordosis (LL) and TLK curve in the FBB position significantly influenced the presence of GERD. Other factors showed no association with GERD. Significant improvements in FSSG scores were noted 1 year postoperatively. However, 20 (28.2%) patients still had GERD symptoms. The postoperative TLK curve was highly significantly correlated with FSSG scores 1 year postsurgery.

CONCLUSIONS

Of the 71 patients treated surgically for ASD, 37 (52%) had a high frequency of GERD symptoms. An inflexible thoracolumbar curve with increased TLK in the FBB position was significantly associated with GERD symptoms. Despite significant improvements in FSSG scores postoperatively, insufficient correction of TLK might be a risk factor for persistent GERD symptoms.

The Current Knowledge on Spinopelvic Mobility

Recent studies may suggest that our conventional knowledge of risk factors for dislocation may need rethinking. Previous studies have demonstrated a large majority of total hip arthroplasty instability with acetabular cups implanted in safe zones. Recently discovered spinopelvic motion is a coordinated biomechanical relationship among acetabular anteversion, pelvic tilt, and lumbar lordosis. Classification includes normal, hypermobile, stiff, stuck standing, stuck sitting, and fused. Normal spinopelvic motion from standing to sitting occurs with hip flexion, posterior sacral tilt, and decreased lumbar lordosis to accommodate a flexed femur and prevent impingement and dislocation. Acetabular cup implantation ideally is adapted based on spinopelvic interactions. This may lower the rate of impingement and subsequent dislocation. These new biomechanical interactions may provide a better understanding of the safe zones of anteversion and inclination.

Functional outcome of non-surgical and surgical management for de novo degenerative lumbar scoliosis: a mean follow-up of 10 years

Background

No studies have evaluated the long-term results of non-surgical and surgical management in de novo degenerative lumbar scoliosis (DNDLS). This study reports on the long-term functional outcome of patients being treated for DNDLS by non-surgical and surgical management.

Methods

This is a retrospective review of a single center database of DNDLS patients that underwent surgical or usual non-surgical management between 1996 and 2007. In a total of 88 patients, 50 (57%) underwent non-surgical and 38 (43%) surgical management. Baseline demographic, radiological-, clinical-, and surgical-related variables were collected. An Oswestry Disability Index (ODI) 2.0 questionnaire was sent to all patients after written informed consent.

Results

Twenty-nine of 88 patients participated in the study, 15 (52%) had undergone surgical and 14 (48%) non-surgical management with a mean follow-up of 10.9 years (range 8-15 years). There were no significant differences (p > 0.05) between non-surgical and surgical patients at baseline for age, body mass index, coronal Cobb angle, and clinical data. None of the non-surgical patients had undergone surgery during follow-up. In the surgical group, 40% had revision surgery. There was no significant difference in ODI total scores between groups at final follow-up (p = 0.649). A larger proportion of patients in the non-surgical group reported an ODI total score of ≤ 22, reflecting minimal disability (43 versus 20%; p = 0.245).

Conclusions

This is the first study that describes the long-term 10-year functional outcome of non-surgical and surgical management in a cohort of patients with DNDLS. No significant difference in functional outcome was found between groups after a mean follow-up of 10 years. Despite the significant potential for selection bias, these results indicate that non-surgical management of patients with DNDLS may lead to adequate functional outcome after long periods of time, with no crossover to surgery. Further study is warranted to define which patients may benefit most from which management regimen.

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

BACKGROUND CONTEXT

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

PURPOSE

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

STUDY DESIGN

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

PATIENT SAMPLE

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

OUTCOME MEASURE

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

METHOD

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

RESULTS

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

CONCLUSION

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

CORRELATION BETWEEN CERVICAL SAGITTAL ALIGNMENT AND FUNCTIONAL CAPACITY IN CERVICAL SPONDYLOSIS

ABSTRACT Objective: To correlate the radiographic parameters of sagittal cervical alignment with quality of life and functional capacity in patients with cervical spondylosis under conservative treatment. Methods: This is an observational and prospective study in patients with cervical spondylosis under conservative treatment and without indication for surgery. The 52 patients included were divided into three groups: axial pain, radiculopathy, and cervical myelopathy. The radiographic parameters considered were cervical lordosis (CL), cervical sagittal vertical axis (CSVA), T1 slope (TS) and the discrepancy between TS and CL (TS-CL). Quality of life and functional capacity were evaluated by the Neck Disability Index (NDI) questionnaire. Pain was assessed by the Visual Analogue Scale (VAS). The correlation between the radiographic parameters and the clinical scores was evaluated by the Pearson correlations coefficient. Results: There was no difference in cervical radiographic parameters between the three groups. In the total of the sample, the mean value of the CSVA was 17.8o (±8.3o), CL, 22.4° (± 8.8°); TS, 29.3° (±6.6°), and TS-CL, 7.0° (±7.4°). Significant inverse correlation (r= -0.3, p=0.039) was observed between NDI and CL, but there was no significant correlation between CL and VAS. CSVA (p=0.541), TS (p=0.287) and TS-CL (p=0.287) had no significantly correlated with NDI or VAS. Conclusion: Considering patients with cervical spondylosis not candidates for surgery, the only sagittal parameter that correlated with functional capacity was LC. In these patients, the correlation between cervical alignment and quality of life needs to be better characterized.

Femoral head retroposition as a potential compensatory mechanism in patients with a severe mismatch between pelvic incidence and lumbar lordosis

OBJECTIVE

Severe mismatch between pelvic incidence (PI) and lumbar lordosis (LL) leads to extra anterior displacement of the gravity line. The objective of this study is to investigate whether femoral head retroposition is a separate compensatory mechanism responsible for the extra anterior displacement.

SUBJECTS AND METHODS

Based on the values of PI and LL, 94 patients were divided into the PI-LL match group (PI-LL ≤ 0°), the mild PI-LL mismatch group (20°> PI-LL >0°), and the severe PI-LL mismatch group (PI-LL ≥ 20°). A series of parameters including PI, LL, PI-LL, thoracic kyphosis (TK), pelvic tilt (PT), sacral slope (SS), knee flexion angle (KFA), tibial obliquity angle (TOA), sagittal vertical axis (SVA), S1 overhang, femoral head shift (FHS), and pelvic shift (PS) were measured and compared among the three groups.

RESULTS

The severe PI-LL mismatch group exhibited significantly greater PI, PI-LL, PT, KFA, SVA, PS, and FHS, and less LL and TK, compared with the control and mild PI-LL mismatch group. The mild PI-LL mismatch group had significantly greater PI-LL, PT, KFA, TOA, and S1 overhang, and less LL and SS than the control group. SS, TOA, and S1 overhang in the severe PI-LL mismatch group differed significantly from that in the control group, but did not differ significantly from that in the mild PI-LL mismatch group.

CONCLUSION

Femoral head retroposition is an entirely separate compensatory mechanism and, in this study, participated in the compensation for the anterior displacement of the gravity line induced by extra-sagittal spinal malalignment in patients with severe PI-LL mismatch.

Supra-acetabular line is better than supra-iliac line for coronal balance referencing-a study of perioperative whole spine X-rays in degenerative lumbar scoliosis and ankylosing spondylitis patients

BACKGROUND CONTEXT

The aim of spinal deformity correction is to restore the spine's functional alignment by balancing it in both the sagittal and coronal planes. Regardless of posture, the ideal coronal profile is straight, and therefore readily assessable.

PURPOSE

This study compares two radiological methods to determine which better predicts postoperative standing coronal balance.

STUDY DESIGN/SETTING

We conducted a single-center, radiographic comparative study between 2011 and 2015.

PATIENT SAMPLE

A total of 199 patients with a mean age of 55.1 years were studied. Ninety patients with degenerative lumbar scoliosis (DLS) and 109 ankylosing spondylitis (AS) were treated with posterior surgery during this period.

OUTCOME MEASURES

Baseline clinical and radiographic parameters (sagittal and coronal) were recorded. Comparison was performed between the new supra-acetabular line (central sacral vertical line [CSVL1]) and conventional supra-iliac line (CSVL2) perpendicular methods of coronal balance assessment. These methods were also compared with the gold standard standing C7 plumb line.

METHODS

Each patient underwent standardized operative procedures and had perioperative spine X-rays obtained for assessment of spinal balance. Adjusted multivariate analysis was used to determine predictors of coronal balance.

RESULTS

Significant differences in baseline characteristics (age, gender, and radiographic parameters) were found between patients with DLS and AS. CSVL1, CSVL2, and C7 plumb line differed in all the perioperative measurements. These three radiological methods showed a mean right coronal imbalance for both diagnoses in all pre-, intra-, and postoperative radiographs. The magnitude of imbalance was the greatest for CSVL2 followed by CSVL1 and subsequently the C7 plumb line. A larger discrepancy between CSVL and C7 plumb line measurements intraoperatively than those postoperatively suggests a postural effect on these parameters, which is greater for CSVL2. Multivariate analysis identified that in DLS, the preoperative C7 plumb line was predictive of its postoperative value. CSVL1, but not CSVL2, was predictive of the postoperative C7 plumb line in patients with AS.

CONCLUSIONS

The supra-acetabular line (CSVL1) is better, although not ideal, as compared with the supra-iliac line (CSVL2) in determining coronal balance. Because CSVL1 still cannot be relied on with a high predictive value, it is imperative that future studies continue to identify better intraoperative markers for achieving coronal balance.

Radiologic Parameters Can Affect the Preoperative Decision Making of Three-Column Spinal Osteotomies in the Treatment of Severe and Stiff Kyphoscoliosis

STUDY DESIGN

Retrospective analysis.

OBJECTIVE

To evaluate whether radiologic parameters affect spine surgeon's osteotomy choice in patients with severe and stiff thoracic kyphoscoliosis.

SUMMARY OF BACKGROUND DATA

Three-column osteotomies were developed to address severe and stiff kyphoscoliosis. Current choice on osteotomies is based on the morphology of kyphosis, global balance, and locations of the main curvature; however, quantitative basis for decision making is still lacking.

METHODS

Sixty patients with severe and stiff thoracic kyphoscoliosis who underwent three-column osteotomy in the thoracic spine were classified into four groups according to the grade of osteotomy. The radiologic parameters including maximum scoliosis, maximum kyphosis, deformity angular ratio (DAR; maximum Cobb angle divided by number of vertebrae involved), apical vertebral translation, coronal balance, and sagittal balance were measured and compared. Correlation analysis between the radiologic parameters and the osteotomy grades was conducted. Perioperative and long-term complications were reviewed.

RESULTS

The overall scoliosis was corrected from a mean preoperative Cobb angle of 129.1° (range, 90-174°) to 56.4° (range, 14-100°), and overall kyphosis was corrected from 124.3° (range, 64-180°) to 54.3° (range, 11-95°). As the osteotomy grades increased, the mean preoperative maximum kyphosis increased from 104.5° to 151.8° and the mean sagittal DAR (S-DAR) increased from 16.4 to 24.9. Statistically significant between-group differences were found for preoperative maximum kyphosis (P = 0.001), S-DAR (P = 0.045), and total DAR (P = 0.033). Significant correlations were observed between the preoperative maximum kyphosis and the osteotomy grade (r = 0.454, P < 0.001). The S-DAR significantly correlated with the osteotomy grade (r = 0.322, P = 0.012).

CONCLUSION

The preoperative maximum kyphosis and the S-DAR may affect the surgeon's decision on the grade of osteotomies. This may enrich the theoretical basis on preoperative planning and help with patient counseling.

LEVEL OF EVIDENCE

4.

Factors influencing spinal sagittal balance, bone mineral density, and Oswestry Disability Index outcome measures in patients with rheumatoid arthritis

PURPOSE

To identify the factors influencing spinal sagittal alignment, bone mineral density (BMD), and Oswestry Disability Index (ODI) outcome measures in patients with rheumatoid arthritis (RA).

METHODS

We enrolled 272 RA patients to identify the factors influencing sagittal vertical axis (SVA). Out of this, 220 had evaluation of bone mineral density (BMD) and vertebral deformity (VD) on the sagittal plane; 183 completed the ODI questionnaire. We collected data regarding RA-associated clinical parameters and standing lateral X-ray images via an ODI questionnaire from April to December 2012 at a single center. Patients with a history of spinal surgery or any missing clinical data were excluded. Clinical parameters included age, sex, body mass index, RA disease duration, disease activity score 28 erythrocyte sedimentation rate (DAS28-ESR), serum anti-cyclic citrullinated peptide antibody, serum rheumatoid factor, serum matrix metalloproteinase-3, BMD and treatment type at survey, such as methotrexate (MTX), biological disease-modifying anti-rheumatic drugs, and glucocorticoids. We measured radiological parameters including pelvic incidence (PI), lumbar lordosis (LL), and SVA. We statistically identified the factors influencing SVA, BMD, VD, and ODI using multivariate regression analysis.

RESULTS

Multivariate regression analysis showed that larger SVA correlated with older age, higher DAS28-ESR, MTX nonuse, and glucocorticoid use. Lower BMD was associated with female, older age, higher DAS28-ESR, and MTX nonuse. VD was associated with older age, longer disease duration, lower BMD, and glucocorticoid use. Worse ODI correlated with older age, larger PI-LL mismatch or larger SVA, higher DAS28-ESR, and glucocorticoid use.

CONCLUSIONS

In managing low back pain and spinal sagittal alignment in RA patients, RA-related clinical factors and the treatment type should be taken into consideration.

Effect of Sagittal Balance on Risk of Falling after Lateral Lumbar Interbody Fusion Surgery Combined with Posterior Surgery

PURPOSE

To demonstrate the impact of correcting sagittal balance (SB) on functional outcomes of surgical treatment for degenerative spinal disease and actual falls via utilization of new minimally invasive lumbar fusion techniques via a lateral approach.

MATERIALS AND METHODS

From November 2011 to March 2015, we enrolled 56 patients who underwent minimally invasive lateral lumbar interbody fusion (LLIF) and matched 112 patients receiving decompression/postero-lateral fusion (PLF) surgery for lumbar spinal stenosis. According to SB status using C7-plumb line-distance (C7PL) and surgery type, patients were divided into three groups: SB PLF, sagittal imbalance (SI) PLF, and LLIF groups. We then compared their outcomes.

RESULTS

The mean C7PL was 6.2±13.6 mm in the SB PLF group, 72.9±33.8 mm in the SI PLF group, and 74.8±38.2 mm in the LLIF group preoperatively. Postoperatively, C7PL in only the LLIF group improved significantly (p=0.000). Patients in the LLIF group showed greater improvement in fall-related functional test scores than the SI PLF group (p=0.007 for Alternate-Step test, p=0.032 for Sit-to-Stand test). The average number of postoperative falls was 0.4±0.7 in the SB PLF group, 1.1±1.4 in the SI PLF group, and 0.8±1.0 in the LLIF group (p=0.041). Oswestry Disability Index and the Euro-QoL 5 dimension visual analogue scale scores also showed greater improvements in the LLIF group than in the SI PLF group at postoperative 1 year (p=0.003, 0.016).

CONCLUSION

Surgical correction of SI in patients with lumbar spinal stenosis using a combination of minimal invasive LLIF and posterior surgery achieved better surgical outcomes and a lower incidence of actual falls than PLF surgery.

Adult Degenerative Lumbar Scoliosis

Adult degenerative lumbar scoliosis is a 3-dimensional deformity defined as a coronal deviation of greater than 10°. It causes significant pain and disability in the elderly. With the aging of the population, the incidence of adult degenerative lumbar scoliosis will continue to increase. During the past decade, advancements in surgical techniques and instrumentation have changed the management of adult spinal deformity and led to improved long-term outcomes. In this article, the authors provide a comprehensive review of the pathophysiology, diagnosis, and management of adult degenerative lumbar scoliosis. [Orthopedics. 2017; 40(6):e930-e939.].

Predictors of Postoperative Recovery Based on Health-Related Quality of Life in Patients after Degenerative Lumbar Scoliosis Surgery

OBJECTIVE

To investigate the factors associated with the recovery process of elderly patients after degenerative lumbar scoliosis surgery.

METHODS

A total of 213 elderly patients who had undergone surgical treatment for degenerative lumbar scoliosis from 2011 to 2015 were included retrospectively in this study. Clinical data and demographics were collected for logistic regression analysis.

RESULTS

Among 213 eligible patients, 77 (38.5%) were classified as being in the excellent group, 70 (35%) as showing improvement, 24 (12%) as showing no change, and 29 (14.5%) as having deteriorated. At baseline, patients differed significantly from matched normative data in all Scoliosis Research Society domains. Larger differences from normative values were found for pain and activity domains. After surgery, each domain improved significantly. In the multivariate logistic regression, age 60-70 years (odds ratio [OR], 2.431; 95% confidence interval [CI], 1.143-5.174), and American Society of Anesthesiologists grade <3 (OR, 2.987; 95% CI, 1.519-5.874) may be predictive factors for a satisfying recovery, whereas presence of complications (OR, 0.342; 95% CI, 0.153-0.765), fusion to the sacrum (OR, 0.200; 95% CI, 0.076-0.523), and more osteotomies (OR, 0.360; 95% CI, 0.132-0.985) have negative effects on the recovery process.

CONCLUSIONS

The factors that affect postoperative recovery in elderly patients with degenerative lumbar scoliosis are age, American Society of Anesthesiologists grade, distal fusion level, presence of complications, and number of osteotomies.

Normal Age-Adjusted Sagittal Spinal Alignment Is Achieved with Surgical Correction in Adolescent Idiopathic Scoliosis

Study Design

Retrospective analysis.

Purpose

Our hypothesis is that the surgical correction of adolescent idiopathic scoliosis (AIS) maintains normal sagittal alignment as compared to age-matched normative adolescent population.

Overview of Literature

Sagittal spino-pelvic alignment in AIS has been reported, however, whether corrective spinal fusion surgery re-establishes normal alignment remains unverified.

Methods

Sagittal profiles and spino-pelvic parameters of thirty-eight postsurgical correction AIS patients ≤21 years old without prior fusion from a single institution database were compared to previously published normative age-matched data. Coronal and sagittal measurements including structural coronal Cobb angle, pelvic incidence, pelvic tilt, thoracic kyphosis, lumbar lordosis, sagittal vertical axis, C2–C7 cervical lordosis, C2–C7 sagittal vertical axis, and T1 pelvic angles were measured on standing full-body stereoradiographs using validated software to compare preoperative and 6 months postoperative changes with previously published adolescent norms. A sub-group analysis of patients with type 1 Lenke curves was performed comparing preoperative to postoperative alignment and also comparing this with previously published normative values.

Results

The mean coronal curve of the 38 AIS patients (mean age, 16±2.2 years; 76.3% female) was corrected from 53.6° to 9.6° (80.9%, p<0.01). None of the thoracic and spino-pelvic sagittal parameters changed significantly after surgery in previously hypo- and normo-kyphotic patients. In hyper-kyphotic patients, thoracic kyphosis decreased (p=0.003) with a reciprocal decrease in lumbar lordosis (p=0.01), thus lowering pelvic incidence-lumbar lordosis mismatch mismatch (p=0.009). Structural thoracic scoliosis patients had slightly more thoracic kyphosis than age-matched patients at baseline and surgical correction of the coronal plane of their scoliosis preserved normal sagittal alignment postoperatively. A sub-analysis of Lenke curve type 1 patients (n=24) demonstrated no statistically significant changes in the sagittal alignment postoperatively despite adequate coronal correction.

Conclusions

Surgical correction of the coronal plane in AIS patients preserves sagittal and spino-pelvic alignment as compared to age-matched asymptomatic adolescents.

Effect of Single-Level Transforaminal Lumbar Interbody Fusion on Segmental and Overall Lumbar Lordosis in Patients with Lumbar Degenerative Disease

OBJECTIVE

To investigate the ability of transforaminal lumbar interbody fusion (TLIF) to improve lumbar lordosis (LL).

METHODS

In this retrospective study, 92 patients undergoing single-level TLIF to treat lumbar degenerative disease were divided into a low back pain, radiculopathy, and neurogenic claudication group according to their symptoms. Preoperative and postoperative measures, including segmental LL, whole LL, pelvic incidence (PI), pelvic tilt, thoracic kyphosis, sagittal vertical axis, visual analog scale for back and leg pain, and Oswestry Disability Index, were used to evaluate radiographic and clinical outcomes.

RESULTS

All clinical parameters were significantly improved after TLIF. There was no significant difference in any radiographic parameters in the low back pain group. In the radiculopathy and neurogenic claudication groups, all radiographic parameters were significantly changed after TLIF except for segmental LL and PI in both groups and pelvic tilt in the radiculopathy group. No statistically significant differences were found in improvement of segmental LL, PI, thoracic kyphosis, and visual analog scale (leg) between the radiculopathy and neurogenic claudication groups, whereas the differences in improvement of whole LL, pelvic tilt, PI-LL, sagittal vertical axis, visual analog scale (back), and Oswestry Disability Index were significant between the 2 groups.

CONCLUSIONS

For patients with neurogenic leg symptoms owing to single-level lumbar degenerative disease, whole LL was improved after TLIF as a result of spontaneous restoration of lordosis at the unfused lumbar levels.

Global Alignment and Proportion (GAP) Score: Development and Validation of a New Method of Analyzing Spinopelvic Alignment to Predict Mechanical Complications After Adult Spinal Deformity Surgery

BACKGROUND

The restoration of normal sagittal alignment is a critical goal in adult spinal deformity surgery to achieve favorable outcomes and prevent mechanical complications. Schwab sagittal modifiers have been accepted as targets for appropriate alignment, but addressing these targets does not always prevent high mechanical complication or revision rates. This may be because the linear absolute numerical parameters do not cover the whole pelvic incidence spectrum and the distribution of lordosis, pelvic anteversion, and negative malalignment are not considered as potential causes of failure. The aim of the present study was to develop and validate a score based on pelvic-incidence-based proportional parameters to better predict mechanical complications.

METHODS

Two hundred and twenty-two patients (168 women and 54 men) followed for ≥2 years after posterior fusion at ≥4 levels were included in the study. The mean age (and standard deviation) was 52.2 ± 19.3 years (range, 18 to 84 years), and the mean duration of follow-up was 28.8 ± 8.2 months (range, 24 to 62 months). The global alignment and proportion (GAP) score was developed and validated in groups of patients randomly assigned to derivation (n = 148, 66.7%) and validation (n = 74, 33.3%) cohorts. GAP score parameters were relative pelvic version (the measured minus the ideal sacral slope), relative lumbar lordosis (the measured minus the ideal lumbar lordosis), lordosis distribution index (the L4-S1 lordosis divided by the L1-S1 lordosis multiplied by 100), relative spinopelvic alignment (the measured minus the ideal global tilt), and an age factor. Proximal and distal junctional kyphosis and/or failure, rod breakage, and other implant-related complications were considered mechanical complications. The predictive accuracy of the GAP score was analyzed using receiver operating characteristic (ROC) analyses. Associations between GAP categories and mechanical complications and revisions were analyzed using Cochran-Armitage tests.

RESULTS

In the validation cohort, 32 patients (43%) experienced mechanical complications and 17 (23%) underwent mechanical revision. The area under curve for the GAP score predicting mechanical complications was 0.92 (standard error [SE] = 0.034, p < 0.001, 95% [confidence interval [CI] = 0.85 to 0.98). Postoperatively, patients with a proportioned spinopelvic state according to the GAP score had a mechanical complication rate of 6% while those with a moderately or severely disproportioned spinopelvic state had rates of 47% and 95%, respectively.

CONCLUSIONS

The GAP score is a new pelvic-incidence-based proportional method of analyzing the sagittal plane that predicts mechanical complications in patients undergoing surgery for adult spinal deformity. Setting surgical goals according to the GAP score may decrease the prevalence of mechanical complications.

Extensive Corrective Fixation Surgeries for Adult Spinal Deformity Improve Posture and Lower Extremity Kinematics During Gait

STUDY DESIGN

Longitudinal cohort.

OBJECTIVE

The present study aimed to document changes in posture and lower extremity kinematics during gait in patients with adult spinal deformity (ASD) after extensive corrective surgery.

SUMMARY OF BACKGROUND DATA

Standing radiographic parameters are typically used to evaluate patients with ASD. Previously, preoperative walking and standing posture discrepancy were reported in patients with ASD. We did not include comparison between before and after surgery. Therefore, we thought that pre- and postoperative evaluations for patients with ASD should include gait analysis.

METHODS

Thirty-nine patients with ASD (5 men, 34 women; mean age, 71.0 ± 6.1) who underwent posterior corrective fixation surgeries from the thoracic spine to the pelvis were included. A 4-m walk was recorded and analyzed. Sagittal balance while walking was calculated as the angle between the plumb line on the side and the line connecting the greater trochanter and pinna while walking (i.e., the gait-trunk tilt angle [GTA]). We measured maximum knee extension angle during one gait cycle, step length (cm), and walking speed (m/min). Radiographic parameters were also measured.

RESULTS

The mean GTA and the mean maximum knee extension angle significantly improved from 13.4° to 6.4°, and -13.3° to -9.4°(P < 0.001 and P = 0.006), respectively. The mean step length improved from 40.4 to 43.1 cm (P = 0.049), but there was no significant change in walking speed (38.4 to 41.5 m/min, P = 0.105). Postoperative GTA, maximum knee extension angle and step length correlated with postoperative pelvic incidence minus lumbar lordosis (r = 0.324, P = 0.044; r = -0.317, P = 0.049; r = -0.416, P = 0.008, respectively).

CONCLUSION

Our results suggest that postoperative posture, maximum knee extension angle, and step length during gait in patients with ASD improved corresponding to how much correction of the sagittal spinal deformity was achieved.

LEVEL OF EVIDENCE

3.

A Novel Lumbar Motion Segment Classification to Predict Changes in Segmental Sagittal Alignment After Lateral Interbody Fixation

STUDY DESIGN

Retrospective cohort study.

OBJECTIVES

Lateral interbody fixation is being increasingly used for the correction of segmental sagittal parameters. One factor that affects postoperative correction is the resistance afforded by posterior hypertrophic facet joints in the degenerative lumbar spine. In this article, we describe a novel preoperative motion segment classification system to predict postoperative correction of segmental sagittal alignment after lateral lumbar interbody fusion.

METHODS

Preoperative computed tomography scans were analyzed for segmental facet osseous anatomy for all patients undergoing lateral lumbar interbody fusion at 3 institutions. Each facet was assigned a facet grade (min = 0, max = 2), and the sum of the bilateral facet grades was the final motion segment grade (MSG; min = 0, max = 4). Preoperative and postoperative segmental lordosis was measured on standing lateral radiographs. Postoperative segmental lordosis was also conveyed as a percentage of the implanted graft lordosis (%GL). Simple linear regression was conducted to predict the postoperative segmental %GL according to MSG.

RESULTS

A total of 36 patients with 59 operated levels were identified. There were 19 levels with MSG 0, 14 levels with MSG 1, 13 levels with MSG 2, 8 levels with MSG 3, and 5 levels with MSG 4. Mean %GL was 115%, 90%, 77%, 43%, and 5% for MSG 0 to 4, respectively. MSG significantly predicted postoperative %GL (P < .01). Each increase in MSG was associated with a 28% decrease in %GL.

CONCLUSIONS

We propose a novel facet-based motion segment classification system that significantly predicted postoperative segmental lordosis after lateral lumbar interbody fusion.

Risk Factors for Poor Patient-Reported Quality of Life Outcomes After Posterior Lumbar Interbody Fusion: An Analysis of 2-Year Follow-up

STUDY DESIGN

A retrospective review of prospectively collected data.

OBJECTIVE

The present study aimed to identify risk factors for poor patient-reported quality of life (QOL) outcomes, based on five categories (pain-related disorders, lumbar spine dysfunction, gait disturbance, social life dysfunction, and psychological disorders) of the Japanese Orthopaedic Association Back Pain Evaluation Questionnaire (JOABPEQ), after posterior lumbar interbody fusion (PLIF) at the 2-year follow-up.

SUMMARY OF BACKGROUND DATA

Many studies have been reported on patient QOL outcomes after lumbar surgery; however, few reports have focused on risk factors for poor postoperative QOL outcomes in terms of the various disabilities and dysfunctions after PLIF.

METHODS

One hundred consecutive patients (39 men and 61 women; mean age 69.6 [44-84] yr) who underwent single- or two-level PLIF for degenerative spondylolisthesis and/or foraminal stenosis with a 2-year follow-up were included. The effectiveness of surgery in each category of the JOABPEQ was evaluated. Demographic and clinical data and radiographic parameters were reviewed. Risk factors for poor postoperative QOL outcomes in each category of the JOABPEQ were investigated by multivariate logistic regression analysis.

RESULTS

Older age and spinopelvic malalignment (preoperative high pelvic tilt or postoperative decrease in lumbar lordosis [=postoperative increase in the mismatch between pelvic incidence and lumbar lordosis]) were risk factors for poor postoperative QOL outcomes in all categories of the JOABPEQ, except for lumbar spine dysfunction. In contrast, increase in number of PLIF segments, non-union, and radiographic adjacent segment degeneration were risk factors for poor postoperative QOL outcomes in lumbar spine dysfunction and gait disturbance.

CONCLUSION

The risk factors for poor QOL outcomes after PLIF differed among the five categories of the JOABPEQ. In particular, surgery-related factors (e.g., increase in number of PLIF segments, nonunion, and radiographic adjacent segment degeneration) had a negative effect on the improvement of lumbar spine dysfunction and gait disturbance.

LEVEL OF EVIDENCE

4.

Pelvic incidence: a fixed value or can you change it?

BACKGROUND CONTEXT

There has been renewed interest in the pelvic vertebrae by spinal surgeons recently. Those involved in working with patients with adult spinal deformity focus on the position of the fused spine as it relates to the pelvis, and determine success or failure by specific numbers for given pelvic parameters. The pelvic parameters that are commonly measured for these patients are pelvic tilt, sacral slope, and pelvic incidence (PI). Out of the three, PI has always been considered to be the fixed measurement, whereas pelvic tilt and sacral slope have the capacity to change in relation to external forces. The assumption that the PI does not change has not been proven in a healthy, asymptomatic population.

PURPOSE

This study aimed to investigate the differences in PI between three pelvic positions used in common functional activities: resting baseline pelvic posture, maximal anterior pelvic rotation, and maximal posterior pelvic rotation.

STUDY DESIGN/SETTING

This was a randomized, prospective study of 50 healthy, asymptomatic, individuals who were recruited from the vicinity of our institution.

PATIENT SAMPLE

Fifty patients (16 men with a mean age of 26.5±12.1 years; 34 women with a mean age of 27.2±10.8 years) were recruited for this study. Initial screening occurred by telephone. The inclusion criteria consisted of participants being between 18 and 79 years of age, no previous history of spine, pelvic, or lower extremity pain which had lasted longer than 48 hours, or history of any disorder in the spine, pelvis, or lower extremity that had required medical care. Female patients could not be pregnant at the time of participation.

OUTCOME MEASURES

Changes in PI were assessed by examining the differences between the values of the PI with each change in pelvic position: resting to maximal anterior pelvic rotation and resting to maximal posterior pelvic rotation. Inter-rater reliability was assessed using Cronbach's alpha.

METHODS

This study was funded by a Small Exploratory Grant from the Scoliosis Research Society. All subjects had an initial posterior-anterior and lateral radiograph taken in their resting pelvic position. If no spinal deformity was noted, each subject was instructed to maximally rotate their pelvis anteriorly and an immediate lateral radiograph was taken. The subject was then instructed to maximally rotate their pelvis posteriorly and an immediate lateral radiograph was again taken. Radiographic measurements of PI were independently measured by a board-certified, fellowship trained orthopedic spine surgeon and a board-certified musculoskeletal radiologist after defining and agreeing to the specific manner of measurement.

RESULTS

Pelvic incidence values changed in 44 of 50 subjects (88%) when they maximally anteriorly rotated their pelvis from the resting pelvic position. The mean change was 2.9°, with 23 of 50 subjects (46%) changing ≥3°. Pelvic incidence values changed in 40 of 50 subjects (80%) when they maximally posteriorly rotated their pelvis from the resting position. The mean change was 2.82° with 27 of 50 subjects (54%) changing by ≥3°.

CONCLUSIONS

This study demonstrated that for a high percentage of the healthy subjects who participated, the PI changed when the subjects varied their pelvic position. This questions the assumption that PI is a fixed parameter and suggests a potential functional motion at the sacroiliac joint. It also supports the idea that intentionally changing one's posture could lead to a change in PI, an idea that could have ramifications in surgical cases.

A Preliminary Algorithm Using Spine Measurement Software to Predict Sagittal Alignment Following Pedicle Subtraction Osteotomy

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To evaluate if spine measurement software can simulate sagittal alignment following pedicle subtraction osteotomy (PSO).

METHODS

We retrospectively reviewed consecutive adult spinal deformity patients who underwent lumbar PSO. Sagittal measurements were performed on preoperative lateral, standing radiographs. Sagittal measurements after simulated PSO were compared to actual postoperative measurements. A regression equation was developed using cases 1-7 to determine the amount of manual rotation required of each film to match the simulated sagittal vertical axis (SVA) to the actual postoperative SVA. The equation was then applied to cases 8-13.

RESULTS

For all 13 cases, the spine software accurately simulated lumbar lordosis, pelvic incidence lumbar lordosis mismatch, and T1 pelvic angle, with no significant differences between actual and simulated measurements. The pelvic tilt (PT), sacral slope (SS), thoracolumbar alignment (TL), thoracic kyphosis (TK), T9 spino-pelvic inclination (T9SPi), T1 spino-pelvic inclination (T1SPi), and SVA were inaccurately simulated. The PT, SS, T9SPi, T1SPi, and SVA all change with manual rotation of the film, and by using the regression equation developed with cases 1-7, we were able to improve the accuracy and decrease the variability of the simulated PT, SS, T9SPi, T1SPi, and SVA for cases 8-13.

CONCLUSIONS

Dedicated spine measurement software can accurately simulate certain sagittal measurements, such as LL, PI-LL, and TPA, following PSO. A number of measurements, including PT, SS, TL, TK, T9SPi, T1SPi, and SVA were inaccurately simulated. Our preliminary algorithm improved the accuracy and decreased the variability of certain measurements, but requires future prospective studies for further validation.

Beyond Pelvic Incidence-Lumbar Lordosis Mismatch: The Importance of Assessing the Entire Spine to Achieve Global Sagittal Alignment

STUDY DESIGN

Retrospective case series.

OBJECTIVE

To investigate which sagittal parameters contribute to a normal sagittal vertical axis (SVA) when there is a pelvic incidence-lumbar lordosis (PI-LL) mismatch >10° following adult spinal deformity (ASD) correction.

METHODS

We performed a retrospective review of ASD patients with >5 levels fused. Sagittal measurements between cohorts of postoperative PI-LL >10° and PI-LL<10° were compared. We correlated SVA to pelvic tilt (PT), thoracic kyphosis (TK), PI-LL, cervical lordosis (CL), and correlated the pre- to postoperative change in SVA to change in PT, change in TK, change in PI-LL, and change in CL. We also correlated SVA and the change in SVA to combined parameters of ((PI-LL) - PT + TK).

RESULTS

We analyzed 52 patients with a mean age of 59 ± 16 years. In patients with a postoperative SVA <5cm, a smaller TK was seen when PI-LL >10° than when PI-LL<10° (15.45° vs 33.04°, P = .0004). Additionally, PT was larger when PI-LL >10° than when PI-LL <10° (25.73° vs 19.07°, P = .006). SVA correlated better with ((PI-LL) - PT + TK) (R² = 0.51) than with PI-LL alone (R² = 0.33). Lastly, there was no significant correlation between change in pre- to postoperative SVA with change in TK for all cases (P = .73), but in cases where change in PI-LL was <10°, there was a significant correlation between change in TK and change in SVA (P = .009).

CONCLUSION

Our results demonstrate that PT and TK, and not just PI-LL, play an important role in maintaining sagittal balance when there is a PI-LL mismatch >10°.