Natural history of spinopelvic alignment differs from symptomatic deformity of the spine

Adaptation of the Lumbar Spine From Orthostasis to Supine

STUDY DESIGN

Observational-ecologic study.

INTRODUCTION

Spine and pelvis undergo modifications in alignment so that the individual can maintain an orthostatic position, but to date there is no evidence as to the contribution of each lumbar segment and the change that occurs in them when moving from orthostasis to supine position.

OBJECTIVE

To identify the difference in the contribution of the lumbar segments and pelvis to the formation of lumbar lordosis in both positions (orthostasis and supine) and how each one alters in this change.

SUMMARY OF BACKGROUND DATA

lumbar lordosis adapts to the individual's body position and can be physiological or pathologic.

MATERIALS AND METHODS

Retrospective cohort study that included 174 patients: the segments total lumbar lordosis (LL), L1-L4, L4-S1, L4-L5, L5-S1, and sacral slope were measured on x-rays (orthostasis) and MRI (supine). We obtained the mean values, correlations and models proposed for the relationship between the values found.

RESULTS

The SS, LL, L1-L4, L4-S1, and L4-L5 had their angular value reduced, and L5-S1 had its contribution to lordosis significantly increased when lying down. Moderate and strong correlations were obtained between SS × LL, L1-L4 and L4-S1, and between LL versus L1-L4 and L4-S1 in both positions. When using linear regression, proposed models were obtained with a high coefficient of determination between LL versus SS, L1-L4 and L4-S1 in orthostasis, for the same measurements and SS versus L4-S1 in supine, as well as for lordosis when comparing the 2 positions.

CONCLUSIONS

The L5-S1 segment has no change in angular value when lying in supine and is thus the largest contributor to lordosis in supine. L1-L4 increases its angular value when standing in orthostasis, the position in which it is the greatest contributor to lordosis.

Sagittal Alignment in the Degenerative Lumbar Spine: Surgical Planning

➤ Sagittal alignment of the spine has gained attention in the field of spinal deformity surgery for decades. However, emerging data support the importance of restoring segmental lumbar lordosis and lumbar spinal shape according to the pelvic morphology when surgically addressing degenerative lumbar pathologies such as degenerative disc disease and spondylolisthesis.➤ The distribution of caudal lordosis (L4-S1) and cranial lordosis (L1-L4) as a percentage of global lordosis varies by pelvic incidence (PI), with cephalad lordosis increasing its contribution to total lordosis as PI increases.➤ Spinal fusion may lead to iatrogenic deformity if performed without attention to lordosis magnitude and location in the lumbar spine.➤ A solid foundation of knowledge with regard to optimal spinal sagittal alignment is beneficial when performing lumbar spinal surgery, and thoughtful planning and execution of lumbar fusions with a focus on alignment may improve patient outcomes.

Analysis of Mechanical Failure Using the GAP Score After Surgery With Lateral and Posterior Fusion for Adult Spinal Deformity

STUDY DESIGN

A retrospective observational study.

OBJECTIVE

The purpose of this study was to evaluate the Global Alignment and Proportion (GAP) score and mechanical failure (MF) following corrective fusion surgery with planned 2-stage surgery using lateral lumbar interbody fusion in patients with adult spinal deformity (ASD).

METHODS

Fifty-four patients (2 men, 52 females, aged 70.3 years) were included. MF, proximal junctional failure (PJF), and rod breakage (RB) occurred in 46.3% (25/54), 22.2% (12/54), and 29.6% (16/54) of patients, respectively. The immediate postoperative GAP scores were compared between patients with MF and without MF (MF+ and MF-, respectively). GAP scores in groups with and without PJF or RB were also compared.

RESULTS

Patients were grouped according to the GAP score for spinopelvic alignment: 23 (42.6%) as proportioned, 22 (40.7%) as moderately disproportioned, and 9 (16.7%) as severely disproportioned. The pre- and postoperative spinopelvic parameters did not differ significantly between the MF- and MF+ groups except pelvic incidence. Postoperatively, the mean pelvic incidence-lumbar lordosis changed to <10° in both groups. The GAP score and 3 categories of GAP scores did not differ significantly between the PJF- and PJF+ groups or between the RB+ and RB- groups.

CONCLUSION

Multiple factors can cause PJF and RB, and the patient's background may affect the ability to use the GAP score to predict MF. Further research may be needed in the future using modified GAP scores with additional factors in ASD patients.

The effect of ethnicity on the age-related changes of spinopelvic characteristics: a systematic review

Spinopelvic characteristics influence the hip's biomechanical behaviour. However, to date there is little knowledge defining what 'normal' spinopelvic characteristics are. This study aims to determine how static spinopelvic characteristics change with age and ethnicity among asymptomatic, healthy individuals. This systematic review followed the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines to identify English studies, including ≥ 18-year-old participants, without evidence of hip or spine pathology or a history of previous surgery or interventional treatment, documenting lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), and pelvic incidence (PI). From a total of 2,543 articles retrieved after the initial database search, 61 articles were eventually selected for data extraction. When all ethnicities were combined the mean values for LL, SS, PT, and PI were: 47.4° (SD 11.0°), 35.8° (SD 7.8°), 14.0° (SD 7.2°), and 48.8° (SD 10°), respectively. LL, SS, and PT had statistically significant (p < 0.001) changes per decade at: -1.5° (SD 0.3°), -1.3° (SD 0.3°), and 1.4° (SD 0.1°). Asian populations had the largest age-dependent change in LL, SS, and PT compared to any other ethnicity per decade at: -1.3° (SD 0.3°) to -0.5° (SD 1.3°), -1.2° (SD 0.2°) to -0.3° (SD 0.3°), and 1.7° (SD 0.2°) versus 1.1° (SD 0.1°), respectively. Ageing alters the orientation between the spine and pelvis, causing LL, SS, and PT to modify their orientations in a compensatory mechanism to maintain sagittal alignment for balance when standing. Asian populations have the largest degree of age-dependent change to their spinopelvic parameters compared to any other ethnicity, likely due to their lower PI.

Examining Clinical Opinion and Experience Regarding Utilization of Plain Radiography of the Spine: Evidence from Surveying the Chiropractic Profession

Plain Radiography of the spine (PROTS) is utilized in many forms of healthcare including the chiropractic profession; however, the literature reflects conflicting opinions regarding utilization and value. Despite being an essential part of Evidence-Based Practice (EBP), few studies assess Doctors of Chiropractic (DCs) clinical opinions and experience regarding the utilization of (PROTS) in practice. In this study, DCs were surveyed regarding utilization of PROTS in practice. The survey was administered to an estimated 50,000 licensed DCs by email. A total of 4301 surveys were completed, of which 3641 were United States (US) DCs. The Clinician Opinion and Experience on Chiropractic Radiography (COECR) scale was designed to analyze survey responses. This valid and reliable scale demonstrated good internal consistency using confirmatory factor analysis and the Rasch model. Survey responses show that 73.3% of respondents utilize PROTS in practice and 26.7% refer patients out for PROTS. Survey responses show that, among US DCs, 91.9% indicate PROTS has value beyond identification of pathology, 86.7% indicate that PROTS is important regarding biomechanical analysis of the spine, 82.9% indicate that PROTS is vital to practice, 67.4% indicate that PROTS aids in measuring outcomes, 98.6% indicate the opinion that PROTS presents very low to no risk to patients, and 93.0% indicate that sharing clinical findings from PROTS studies with patients is beneficial to clinical outcomes. The results of the study indicated that based on clinical experience, the majority of DCs find PROTS to be vital to practice and valuable beyond the identification of red flags.

Preoperative Association Between Quantitative Lumbar Muscle Parameters and Spinal Sagittal Alignment in Lumbar Fusion Patients

STUDY DESIGN

A retrospective cross-sectional study.

OBJECTIVE

To assess the association between spinal muscle morphology and spinopelvic parameters in lumbar fusion patients, with a special emphasis on lumbar lordosis (LL).

SUMMARY OF BACKGROUND DATA

Maintenance of sagittal alignment relies on muscle forces, but the basic association between spinal muscles and spinopelvic parameters is poorly understood.

MATERIALS AND METHODS

Patients operated between 2014 and 2017 who had both lumbar magnetic resonance imaging scan and standing whole-spine radiographs within six months before surgery were included. Muscle measurements were conducted on axial T2-weighted magnetic resonance images at the superior endplate L3-L5 for the psoas and L3-S1 for combined multifidus and erector spinae (paraspinal) muscles. A pixel intensity threshold method was used to calculate the total cross-sectional area (TCSA) and the functional cross-sectional area (FCSA). Spinopelvic parameters were measured on lateral standing whole-spine radiographs and included LL, pelvic incidence (PI), PI-LL mismatch, pelvic tilt, sacral slope, thoracic kyphosis, and sagittal vertical axis. Analyses were stratified by biological sex. Multivariable linear regression analyses with adjustments for age and body mass index (BMI) were performed.

RESULTS

A total of 104 patients (62.5% female) were included in the analysis. The patient population was 90.4% White with a median age at surgery of 69 years and a median BMI of 27.8 kg/m 2 . All muscle measurements were significantly smaller in women. PI, pelvic tilt, and thoracic kyphosis were significantly greater in women. PI-LL mismatch was 6.1° (10.6°) in men and 10.2° (13.5°) in women ( P =0.106), and sagittal vertical axis was 45.3 (40.8) mm in men and 35.7 (40.8) mm in women ( P =0.251). After adjusting for age and BMI, paraspinal TCSA at L3-L5, and paraspinal FCSA at L4 showed significant positive associations with LL in women. In men, psoas TCSA at L5 and psoas FCSA at L5 showed significant negative associations with LL, but none of the paraspinal muscle measurements.

CONCLUSION

Our findings indicate that psoas and lumbar spine extensor muscles interact differently on LL among men and women, creating a unique mechanical environment.

LEVEL OF EVIDENCE

Level 4.

Psychometric Properties of the Scoliosis Research Society Questionnaire (Version 22r) Domains Among Adults With Spinal Deformity: A Rasch Measurement Theory Analysis

Objective

Adult spinal deformity (ASD) have lower health-related quality of life (HRQoL) compared to the general population. Applying Rasch measurement theory (RMT), this study tested the revised Scoliosis Research Society-22 (SRS-22r) HRQoL instrument among symptomatic adult patients with degenerative spinal disorders and varying degrees of ASD.

Methods

SRS-22r data from 637 outpatient spine clinic patients with degenerative spine conditions were investigated for unidimensionality, item/scale fit, differential item functioning (DIF), scale coverage/targeting, and person separation index (PSI) using RMT.

Results

Unidimensionality of the SRS-22r was not supported for either the total score or for 3 of its 5 domains. Item fit was acceptable for 11/22 items. The individual domains showed good coverage despite the degree of structural disorders. Ordered thresholds were achieved by merging response categories in some of the items. DIF towards age or sex was found in 11/22 items and in some domain items. The PSI exceeded 0.7 for the SRS-22r total score.

Conclusion

The individual domain scores of the SRS-22r perform better than the total score providing good coverage and targeting among patients with ASD. Refinements of items and domains may improve the structural validity of the instrument to meet the criteria for measuring ASD patients, even when multidimensionality persists.

Optimal Cut-Off Points of Sagittal Spinopelvic Parameters as a Morphological Parameter to Predict Efficiency in Nerve Block and Pulsed Radiofrequency for Lumbar Facet Joint Pain: A Retrospective Study

Background

After proper patient selection, anatomically correct pulsed radiofrequency of the lumbar facet joints provide long-term pain relief in a routine clinical setting. In the study, we performed an analysis of clinical and radiological predictive factors and provide the scientific basis for this promising modality.

Methods

The study included 198 patients with lower back pain due to lumbar facet joint disease who underwent medial branch block and pulsed radiofrequency during the period 2015–2019. According to the improvement in pain score, the patients were divided into good and poor outcome groups. Clinical and radiological data were collected and analyzed.

Results

The multivariable analysis revealed the predictive factors, including lumbar lordosis, lower lumbar lordosis, pelvic tilt, the number of facet joints, old compression fracture with/without vertebroplasty, and post lumbar fusion procedures.

Conclusion

With the results of this study, we demonstrated that the improved outcome after the surgery was related to lumbar lordosis, lower lumbar lordosis, pelvic tilt, the number of facet joints, old compression fracture with/without vertebroplasty, and the lumbar fusion procedures. Old compression fractures and lumbar fusion would change the radiological factors and cause refractory lumbar facet joint pain.

Characteristics of Osteoporotic Low Lumbar Vertebral Fracture and Related Lumbosacral Sagittal Imbalance

Osteoporotic vertebral fracture (OVF) usually occurs in the thoracolumbar region and rarely affects the low lumbar region. The characteristics of osteoporotic low lumbar fracture (OLLF) have not been reported. Lumbosacral sagittal balance plays an important role in preserving the normal physiologic function of the spine. However, it is unknown how lumbosacral parameters vary in patients with OLLF. The authors retrospectively analyzed the clinical and radiologic characteristics of patients with OLLF and osteoporotic thoracolumbar vertebral fracture (OTVF) who were treated at their institution. Vertebral height, local deformity angle, and visual analog scale and Oswestry Disability Index scores were assessed preoperatively and postoperatively for both groups. The changes in lumbosacral parameters were measured for patients with OLLF. The results showed that OLLF was more likely to occur at L3 (53.66%) and that the prevalence of severe trauma (29.27%) was higher among patients with OLLF (P<.05). The most common morphologic type of the vertebrae affected by OLLF was biconcave (58.54%, P<.05). Patients who had OLLF showed an apparent increase in pelvic tilt and a decrease in local lordosis and sacral slope. Postoperatively, vertebral height, local deformity angle, and visual analog scale and Oswestry Disability Index scores were significantly improved compared with preoperative values (P<.05). Among patients with OLLF, local lordosis and sacral slope increased significantly, whereas pelvic tilt decreased significantly after percutaneous kyphoplasty. Restoration of local lordosis had a mean value of 6.29°±4.80°. These results indicate that OLLF has unique characteristics compared with OTVF and that it results in lumbosacral sagittal imbalance. Percutaneous kyphoplasty is effective and safe for the treatment of OLLF and plays an important role in postoperative improvement of sagittal imbalance. [Orthopedics. 2021;44(1):e7-e12.].

Restoring lumbar lordosis: a systematic review of controlled trials utilizing Chiropractic Bio Physics® (CBP®) non-surgical approach to increasing lumbar lordosis in the treatment of low back disorders

[Purpose] To systematically review controlled trial evidence for the use of lumbar extension traction by Chiropractic BioPhysics^® methods for the purpose of increasing lumbar lordosis in those with hypolordosis and low back disorders. [Methods] Literature searches were performed in Pubmed, PEDro, CINAHL, Cochrane, and ICL databases. Search terms included iterations related to the lumbar spine, low back pain and extension traction rehabilitation. [Results] Four articles detailing 2 randomized and 1 non-randomized trial were located. Trials demonstrated increases in radiographic measured lordosis of 7–11°, over 10–12 weeks, after 30–36 treatment sessions. Randomized trials demonstrated traction treated groups mostly maintained lordosis correction, pain relief, and disability after 6-months follow-up. The non-randomized trial showed lordosis and pain intensity were maintained with periodic maintenance care for 1.5 years. Importantly, control/comparison groups had no increase in lumbar lordosis. Randomized trials showed comparison groups receiving physiotherapy-less the traction, had temporary pain reduction during treatment that regressed towards baseline levels as early as 3-months after treatment. [Conclusion] Limited but good quality evidence substantiates that the use of extension traction methods in rehabilitation programs definitively increases lumbar hypolordosis. Preliminarily, these studies indicate these methods provide longer-term relief to patients with low back disorders versus conventional rehabilitation approaches tested.

Assessment of Sagittal Spinopelvic Balance in a Population of Normal Chinese Children

STUDY DESIGN

A retrospective study of 257 normal children at a single center from July 2016 to November 2018 was performed.

OBJECTIVE

To evaluate the spinopelvic parameters in a population of normal children and adolescents in mainland China.

SUMMARY OF BACKGROUND DATA

Values for sagittal parameters of the spine vary significantly by ages and different population. No study has yet quantified the normal measures for children and adolescents in China, or how these measures compare with other populations.

METHODS

Pelvic incidence (PI), sacral slope, pelvic tilt, thoracic kyphosis (TK, T5-T12), lumbar lordosis (LL, L1-S1), and sagittal vertical axis were measured and evaluated by whole spine AP&lateral X-ray images.

RESULTS

A total of 257 subjects, including 116 boys (45%) and 141 girls (55%) aged 3 to 12 years, were enrolled. Correlation matrix analysis demonstrated that sagittal balance is strongly correlated with age and Risser sign, including PI, a reported fixed parameter. Further investigation showed that PI could be expressed by the equation PI = 26.243+1.153×age.

CONCLUSION

PI was not a fixed but a dynamic parameter in the population under 12-year old. Indeed, PI increases with age and bone maturity in childhood. We also found lower PI, pelvic tilt, and sacral slope compared with published studies of adolescents in other countries. These results may aid in the treatment of patients with spinal deformity, to help them achieve a certain degree of sagittal spinopelvic balance.

LEVEL OF EVIDENCE

2.

Evidence-Based Recommendations for Spine Surgery

: This next issue of Evidence-Based Recommendations for Spine Surgery examines six articles that seek to address pressing and relevant issues in contemporary spine surgery. These articles explore the safety and efficacy of tranexamic acid during lumbar surgery, the utility of post-operative MRI after spinal decompression surgery, the role of teriparatide for fusion support in osteoporotic patients, sagittal spinopelvic alignment in adults, the comparative effectiveness of lumbar disk arthroplasty and prognostic factors for satisfaction after lumbar decompression surgery. These important publications are examined rigorously - both clinically and methodologically - and recommendations regarding impact on clinical practice are provided.Level of Evidence: N/A.

Deterioration of sagittal spinal alignment with age originates from the pelvis not the lumbar spine: a 4-year longitudinal cohort study

PURPOSE

There is controversy regarding age-related deterioration of spinal sagittal alignment in cross-sectional study. Although we reported that deterioration in spinal alignment originated at the cervical spine in males and the pelvis in females, others studies have indicated that the lumbar spine is initially implicated in both sexes. The purpose of this study was to clarify these differences in a longitudinal cohort study.

METHODS

Our analysis was based on 237 individuals aged 60-89 years who participated in our health screening study in 2014 and 2018. They were classified into six groups by birth year and sex: 60-69 years (26 males, 49 females); 70-79 years (35 males, 88 females); and 80-89 years (19 males, 20 females). The following parameters were measured from standing radiographs: pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), thoracic kyphosis, T1 slope, cervical lordosis, C7 sagittal vertical axis (C7 SVA), and C2-7 SVA.

RESULTS

In males, the first significant change was an increase in the PT angle (19°, in 2014, to 21°, in 2018) in the 80-89 years age group (P < 0.05), with no significant deterioration in cervical parameters. In females, spinal deterioration included a change in the SS (32°-30°), PT (18°-20°), and SVA (- 8 to 6 mm) in the 60-69 years age group (P < 0.05), with no change in the LL.

CONCLUSIONS

Contrary to prior studies, our longitudinal data indicated that deterioration in spinal alignment originates in the pelvis for both sex but develops earlier in females than males.

Natural history of the aging spine: a cross-sectional analysis of spinopelvic parameters in the asymptomatic population

OBJECTIVE

There have been numerous studies demonstrating increased pain and disability when patients' spinopelvic parameters fall outside of certain accepted ranges. However, these values were established based on patients suffering from spinal deformities. It remains unknown how these parameters change over a lifetime in asymptomatic individuals. The goal of this study was to define a range of spinopelvic parameters from asymptomatic individuals.

METHODS

Sagittal scoliosis radiographs of 210 asymptomatic patients were evaluated. All measurements were reviewed by 2 trained observers, supervised by a trained clinician. The following parameters and relationships were measured or calculated: cervical lordosis (CL), thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sagittal vertical axis (SVA), cervical SVA (cSVA), and T1 slope, TK/LL, truncal inclination, pelvic tilt (PT), LL-PI, LL/PI, and T1 slope/PI. Patients were stratified by decade of life, and regression analysis was performed to delineate the relationship between each consecutive age group and the aforementioned parameters.

RESULTS

Cervical lordosis (R2 = 0.61), thoracic kyphosis (R2 = 0.84), SVA (R2 = 0.88), cSVA (R2 = 0.51), and T1 slope (R2 = 0.77) all increase with age. Truncal inclination (R2 = 0.36) and T1 slope/CL remain stable over all decades (R2 = 0.01). LL starts greater than PI, but in the 6th decade of life, LL becomes equal to PI and in the 7th decade becomes smaller than PI (R2 = 0.96). The ratio of TK/LL is stable until the 7th decade of life (R2 = 0.81), whereas PT is stable until the 6th decade (R2 = 0.92).

CONCLUSIONS

This study further refines the generally accepted LL = PI + 10° by showing that patients under the age of 50 years should have more LL compared to PI, whereas after the 5th decade the relationship is reversed. SVA was not as sensitive across age groups, exhibiting a marked increase only in the 7th decade of life. Given the reliable increase of CL with age, and the stability of T1 slope/CL, this represents another important relationship that should be maintained when performing cervical deformity/fusion surgery. This study has important implications for evaluating adult patients with spinal deformities and for establishing corrective surgical goals.

SAGITTAL BALANCE IN ADOLESCENT IDIOPATHIC SCOLIOSIS

ABSTRACT Objective The objective of this study is to achieve a better understanding of the parameters that influence sagittal balance in a population with adolescent idiopathic scoliosis (AIS). Methods A retrospective study of 80 patients with adolescent idiopathic scoliosis (AIS) was conducted. The parameters evaluated were: age, sex, pelvic incidence (PI), sacral slop (SS), pelvic tilt (PT), sagittal balance (SB), coronal balance (CB), lumbar lordosis (LL), thoracic kyphosis (TK) divided into upper (between T1 and T5) and lower (between T5 and T12), cervical spine alignment (CSA), and Cobb’s coronal angle (CCA) of primary scoliotic curvature. Results Regarding the sagittal balance, this study demonstrated a significant statistical positive correlation with cervical shape (p<0.01) and upper thoracic kyphosis (from T1 to T5) (p<0.05), but not with the other variables. LL had a strong influence on lower thoracic curvature (from T5 to T12) and was strongly influenced by the PI and SS. Conclusions Sagittal balance is a parameter that is influenced by multiple factors. In fact, it is closely related to cervical shape and the upper thoracic curvature (from T1 to T5), which in turn, is closely linked to the severity of the scoliotic kyphosis. The Cobb angle of the lower thoracic spine (from T5 to T12) is more closely correlated with the angle of lumbar lordosis than with the upper thoracic kyphosis (from T1 to T5). Level of evidence IV; Case Series.

A Geometric Model to Determine Patient-Specific Cup Anteversion Based on Pelvic Motion in Total Hip Arthroplasty

Introduction

Cup position is critical to stability in total hip arthroplasty and is affected by pelvis motion during positions of daily life. The purpose of this study was to explicitly define the relationship between sagittal pelvic motion and resultant cup functional anteversion and create a tool to guide the surgeon to a patient-specific intra-operative anteversion.

Materials and Methods

10,560 combinations of inclination, anteversion, and pelvic tilt were generated using a geometric model. Resultant functional anteversion was calculated for each iteration and variables were correlated. An electronic mobile tool was created that compares inputted patient-specific values to population-based averages to determine pelvic positions and dynamics that may lead to instability.

Results

A third-degree polynomial equation was used to describe the relationship between variables. The freely downloadable mobile tool uses input from pre-operative plain radiographic measurements to provide the surgeon a quantitative correction to intra-operative cup anteversion based on differences in functional anteversion compared to population-based averages.

Conclusion

This study provides a geometric relationship between planned cup position, pelvic position and motion, and the resultant functional anteversion. This mathematical model was applied to an electronic tool that seeks to determine an individualized intra-operative cup anteversion based on measured patient-specific pelvic dynamics.

Further validation of the Scoliosis Research Society (SRS-30) questionnaire among adult patients with degenerative spinal disorder

PURPOSE

The Scoliosis Research Society (SRS-30) questionnaire proved valid in measuring health-related quality of life (HRQoL) in adult patients with spinal deformity or degenerative disease. This study further assesses the validity of the SRS-30 by comparing its results with other HRQoL instruments, such as Oswestry disability index (ODI) and the RAND-36, among unselected adult patients with degenerative spinal disorder.

MATERIALS AND METHODS

628 consecutive patients completed the SRS-30, the ODI, the pain visual analog scale (VAS), and RAND-36 questionnaires. Using a 9 mm minimal important difference threshold of the VAS, patients were divided into three groups of symptom location: back pain (n = 226), lower extremity pain (n = 161), and combination of both (n = 241). Statistical and illustrative tests using beta coefficients, Rasch measurement analytics, and score distributions were used for analysis.

RESULTS

The SRS-30 functioned well for all three subgroups. There were small differences in convergent validity of the SRS-30 compared to the ODI and the RAND-36 between the three subgroups. The SRS-30 performed similarly in different pain groups independent of age, gender, or deformity severity. The scale displayed good coverage and targeting for all three subgroups.

CONCLUSIONS

The SRS-30 proved to provide valid HRQoL scores for all adult patients with degenerative spinal disorders. Implications for Rehabilitation Degenerative spinal conditions associated with spinal deformities are common in patients over 60 years. Low back pain is globally the leading cause of disability. The applicability of the Scoliosis Research Society (SRS-30) questionnaire has not been tested in relation to different pain origins. The SRS-30 proved to provide valid health-related quality of life assessment among patients with degenerative spinal disease independent of pain location. The SRS-30 questionnaire can be used to assess the level of disability and rehabilitation of patients with degenerative spinal disease.

Normal values for sagittal spinal alignment: a study of Brazilian subjects

OBJECTIVES

The purpose of this study is to investigate the normal values of and chain of correlations between spinopelvic parameters in a Brazilian population.

METHODS

This is a prospective observational study including asymptomatic adult subjects who had full spinal radiographs performed. The subjects were stratified by age into 3 groups (18-39 years old, 40-59 years old, and >60 years old), and radiographic parameters were compared across age groups and gender using ANOVA and Student's t-test, respectively. The relationships between various radiographic parameters were evaluated with Pearson correlation coefficients.

RESULTS

One hundred and thirty asymptomatic volunteers (mean age, 48 years) met the inclusion criteria. The mean sagittal parameters in a normal Brazilian population were as follows: lumbar lordosis (LL) of 56.8°, pelvic tilt (PT) of 12.4°, pelvic incidence (PI) of 49.4°, PI-LL of -7.4°, T1 pelvic angle (TPA) of 8°, sagittal vertical axis (SVA) of -0.54 cm and T1 slope of 25.2°. Subjects ≥60 years old had significantly higher values of SVA (p=0.024) and TPA (p=0.009) than the two younger age groups. The TPA was significantly correlated with the following spinopelvic parameters: LL (r=-0.172, p=0.005), PT (r=0.776, p<0.001), PI (r=0.508, p<0.001), PI-LL (r=0.717, p<0.001), SVA (r=0.409, p<0.001) and T1 slope (r=0.172, p=0.050).

CONCLUSION

This study demonstrated significant physiologic trunk inclination with increasing age. The TPA, an angular parameter of global spinal alignment, presented a chain of correlations with different spinal segments.

Risk factors for medical complications after long-level internal fixation in the treatment of adult degenerative scoliosis

PURPOSE

This study evaluates baseline patient characteristics and surgical parameters for risk factors of medical complications in ASD patients received posterior long level internal fixation.

METHODS

Analysis of consecutive patients who underwent posterior long-level instruction fixation for adult degenerative scoliosis (ADS) with a minimum of two year follow-up was performed. Pre-operative risk factors, intraoperative variables, peri-operative radiographic parameters, and surgical-related risk factors were collected to analyze the effect of risk factors on medical complications. Patients were separated into groups with and without medical complication. Then, complication group was further classified as major or minor medical complications. Potential risk factors were identified by univariate testing. Multivariate logistic regression was used to evaluate independent predictors of medical complications.

RESULTS

One hundred and thirty-one ADS patients who underwent posterior long segment pedicle screws fixation were included. Total medical complication incidence was 25.2%, which included infection (12.2%), neurological (11.5%), cardiopulmonary (7.6%), gastrointestinal (6.1%), and renal (1.5%) complications. Overall, 7.6% of patients developed major medical complications, and 17.6% of patients developed minor medical complications. The radiographic parameters of pre-operative and last follow-up had no significant difference between the groups of medical complications and the major or minor medical complications subgroups. However, the incidence of cerebrospinal fluid leak (CFL) in patients who without medical complications was much lower than that with medical complications (18.4 vs. 42.4%, P = 0.005). Independent risk factors for development of medical complications included smoking (OR = 6.45, P = 0.012), heart disease (OR = 10.07, P = 0.012), fusion level (OR = 2.12, P = 0.001), and length of hospital stay (LOS) (OR = 2.11, P = 0.000). Independent risk factors for development of major medical complications were diabetes (OR 6.81, P = 0.047) and heart disease (OR = 5.99, P = 0.049). Except for the last follow-up, Oswestry Disability Index and visual analog scale of the patient experienced medical complications trend higher score; the clinical outcomes have no significant difference between the medical and major complications groups.

CONCLUSION

Heart disease comorbidity is an independent risk factor for both medical and major medical complications. Smoking, fusion level, and LOS are independent risk factors for medical complication. Diabetes is the independent risk factors for major medical complications.

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.

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.

Multilevel Schwab grade II osteotomies for sagittal plane correction in the management of adult spinal deformity

BACKGROUND CONTEXT

Prior reports have compared posterior column osteotomies with pedicle subtraction osteotomies in terms of utility for correcting fixed sagittal imbalance in adolescent patients with deformity. No prior reports have described the use of multilevel Smith-Petersen Osteotomies (SPOs) alone for surgical correction in the adult spinal deformity (ASD) population.

PURPOSE

The study aimed to determine the utility of multilevel SPOs in the management of global sagittal imbalance in ASD patients.

STUDY DESIGN/SETTING

This is a retrospective observational study at a single academic center.

PATIENT SAMPLE

The sample included 85 ASD patients.

OUTCOME MEASURES

This is a radiographic outcomes cohort study.

METHODS

The radiographs of 85 ASD patients were retrospectively evaluated before and after long-segment (>5 spinal levels) fusion and multilevel SPO (≥3 levels) for sagittal imbalance correction. The number of osteotomies, correction in regional lumbar lordosis (LL), and correction per osteotomy was evaluated. Independent predictors of correction per SPO were evaluated with a hierarchical linear regression analysis.

RESULTS

Eighty-five patients (mean age: 67.5±11 years) were identified with ASD (372 SPOs). The mean preoperative sagittal vertical axis (SVA) and T1 pelvic angle (TPA) were 8.16±6.75 cm and 25°±13.23°, respectively. The mean postoperative central sacral vertical line (CSVL) and SVA were 0.67±0.70 cm and 1.29±5.41 cm, respectively. The mean improvement in SVA was 6.29 cm achieved with a correction of approximately 5.05° per SPO. The mean LL restoration was 20.3°±13.9°, and 33(39%) patients achieved a final pelvic incidence minus lumbar lordosis (PI-LL) ≤10°. Fifty-four (64%) achieved a postoperative PI-LL ≤15°, 75 (88%) with a PI-LL ≤20°, and 85 (100%) achieved a PI-LL ≤25°. Correction per SPO was similar regardless of prior fusion (4.87° vs. 5.72° for revisions, p=.192). In a subgroup analysis of SVA greater than 10 cm, there was no significant difference in the final LL, thoracic kyphosis, PI-LL, SVA, CSVL, and TPA, as compared with SVA <10 cm. The LL was the only independent predictor of osteotomy correction per level (LL: β coefficient=-0.108, confidence interval: -0.141 to 0.071, p<.0001).

CONCLUSIONS

Multilevel SPOs are feasible for restoration of LL as well as sagittal and coronal alignment in the ASD population with or without prior instrumented fusion.

Lumbar Spine Alignment in Six Common Postures: An ROM Analysis With Implications for Deformity Correction

STUDY DESIGN

A cross-sectional study of prospectively collected data.

OBJECTIVE

To compare lumbar spine alignment in six common postures, and estimate loss in range of motion (ROM) relative to standing.

SUMMARY OF BACKGROUND DATA

Ideal position for fusion of lumbar spine remains unknown. Although surgical fusion is necessary for deformity correction and symptom relief, the final position in which the vertebrae are immobilized should provide maximum residual function.

METHODS

Data were collected prospectively from 70 patients with low back pain recruited over a year. All subjects had x-rays performed in slump sitting, forward bending, supine, half squatting, standing, and backward bending postures. ROM quantified in terms of sagittal global and segmental Cobb angles was measured from L1 to S1. Loss of ROM relative to standing was calculated for each posture. Analysis of variance and unpaired t tests were used to identify differences in alignment between postures.

RESULTS

Slump sitting gives the greatest lumbar flexion followed by forward bending, and supine postures (P < 0.001). Backward bending produces greater lumbar extension than standing (P = 0.035). Half-squatting and standing postures were not significantly different (P = 0.938). For all postures, L4-5 and L5-S1 segments remained in lordosis, with L4-5 having greater ROM than L5-S1. L1-2 turns kyphotic in lying supine, L2-3 at forward bending, and L3-4 at slump sitting in the form of a "kyphosing cascade." Should the entire lumbar spine be fused in standing position from L1-S1, there would likely be a mean loss of 47.6° of lumbar flexion and 5.9° of lumbar extension.

CONCLUSION

The present study demonstrates the extent of flexibility required of the lumbar spine in assuming various postures. It also enables comparison of the differences in degree of motion occurring in the lumbar spine, both across postures and across segments. Significant loss in ROM, particularly flexion, is anticipated with fusion modeled after the lordotic standing lumbar spine.

LEVEL OF EVIDENCE

2.

Pelvic Incidence Can Be Changed not only by Age and Sex, but also by Posture Used during Imaging

OBJECTIVE

Computed tomography (CT), rather than conventional 2-dimensional radiography, was used to scan and measure pelvic parameters. The results were compared with measurements using X-ray.

METHODS

Pelvic parameters were measured using both CT and X-ray in 254 patients who underwent both abdomino-pelvic CT and X-ray at the pelvic site. We assessed the similarity of the pelvic parameters between the 2 exams, as well as the correlations of pelvic parameters with sex and age.

RESULTS

The mean values of the subjects' pelvic parameters measured on X-ray were: sacral slope (SS), 31.6°; pelvic tilt (PT), 18.6°; and pelvic incidence (PI), 50.2°. The mean values measured on CT were: SS, 35.1°; PT, 11.9°; and PI, 47.0°. PT was found to be 4.07° higher on X-ray and 2.98° higher on CT in women, with these differences being statistically significant (p<0.001, p<0.001). PI was 4.10° higher on X-ray and 2.78° higher on CT in women, with these differences also being statistically significant (p<0.001, p=0.009). We also observed a correlation between age and PI. For men, this correlation coefficient was 0.199 measured using X-ray and 0.184 measured using CT. For women, this correlation coefficient was 0.423 measured using X-ray and 0.372 measured using CT.

CONCLUSION

When measured using CT compared to X-ray, SS increased by 3.5°, PT decreased by 6.7°, and PI decreased by 3.2°. There were also statistically significant differences in PT and PI between male and female subjects, while PI was found to increase with age.

Sagittal spino-pelvic alignment in adults: The Wakayama Spine Study

OBJECTIVES

To establish the normal values of spino-pelvic alignment and to clarify the effect of age-related changes using large, community-based cohorts.

METHODS

In this study, data from 1461 participants (466 men, 995 women) were analyzed. On lateral standing radiographs, the following parameters were measured: thoracic kyphosis (TK), lumbar lordosis (LL), pelvic tilt (PT), pelvic incidence (PI), and C7 sagittal vertical axis (SVA). All values are expressed as the mean±standard deviation. The Spearman rank correlation coefficient was used to examine correlations between variables of spino-pelvic parameters. Finally, we analyzed the relationship between age and spino-pelvic parameters. Therefore, we entered values for the body mass index (BMI), SVA, TK, and PI-LL into a multiple regression model to adjust for potential confounding factors.

RESULTS

The SVA, TK, and PT increased with age, and LL decreased with age. Regarding sex differences, the TK was statistically significantly larger in men than in women, and LL, PT, and PI were statistically significantly smaller in men than in women. Correlation coefficients between the SVA and TK, between the SVA and PI-LL, and between TK and PI-LL were none, strong, and weak, respectively. Results of multiple regression analysis between age and spino-pelvic parameters showed that the standardized partial regression coefficients for the SVA, TK, and PI-LL were 0.17, 0.30, and 0.23, respectively, in men and 0.29, 0.32, and 0.23, respectively, in women.

CONCLUSIONS

We found that all parameters were significantly associated with age in men and women. The SVA, TK, and PT increased with age, and LL decreased with age. Results of multiple regression analysis also demonstrated that the SVA, TK, and PI-LL are related to age. Indeed, the PI-LL value increased with age. In this study, a more excessive PI-LL mismatch was shown, indicating an increased risk of spinal malalignment. Differences in the absolute values of spino-pelvic parameters in each sex were small yet statistically significant. Thus, further study should be performed to corroborate this finding.

Sagittal spinal alignment in asymptomatic patients over 30 years old in the Korean population

BACKGROUND

We aim to provide sagittal and pelvic parameters according to different age groups in an asymptomatic population all over 30 years old and to investigate the possible causes of changes in these parameters.

METHODS

Whole-spine, standing lateral radiographs were taken in 128 asymptomatic Korean people over 30 years old. The spinal parameters (the total thoracic kyphosis (TTK), maximal lumbar lordosis (MLL), total lumbar lordosis (TLL), lower lumbar lordosis (LLL), thoracolumbar junctional angle (TLJA), and lumbar inclination (LI)), pelvic parameters (pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT)), and spinal balance parameters (spinal balance, sacropelvic balance, and spinopelvic balance) were measured. The body mass index, body protein mass, waist line, skeletal muscle mass, and body fat mass were also measured for potential causes.

RESULTS

TTK and TLJA were significantly increased in the group over 70 years of age compared to the other age groups (p = 0.0002, <0.001). TLL was significantly decreased in the group over 70 years of age (p = 0.002), whereas the PI values were similar to PI even in over 70-year age group. LLL did not differ in the group over 70 years of age (p = 0.29), gradually increasing with an increase in age. SS was significantly decreased and PT was significantly increased in the group over 70 years of age as compared to the other age groups (p = 0.049, 0.049, respectively). PI was similar in all age groups (p = 0.75). Spinal balance was significantly decreased in the group over 70 years of age (p = <0.0001). PT was significantly associated with body protein mass and skeletal muscle mass (p = 0.01, 0.001, respectively). Body protein mass and skeletal muscle mass were significantly lower in the group over 70 years of age (p = 0.02, 0.02) and were possible causes.

CONCLUSIONS

Several sagittal and pelvic parameters are different in asymptomatic adults over 70 years of age. Decreased body protein mass and skeletal muscle mass are possible causes of these changes.

Curve Characteristics and Foraminal Dimensions in Patients With Adult Scoliosis and Radiculopathy

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To demonstrate a correlation between radiculopathy symptoms, foraminal morphology, and curve types.

SUMMARY OF BACKGROUND DATA

Patients with degenerative scoliosis frequently present with foraminal stenosis and radiculopathy, the origin of which is not well understood.

METHODS

A total of 48 patients (384 foraminas) were included: 14 with low back pain (B); 16 with femoral nerve pain (F); and 18 with sciatic nerve pain (S). The symptomatic foramen of groups F and S were compared with asymptomatic foramina. Alignment was measured from standardized radiographs; 3D-CT reconstructions were used to measure foraminal height and area. Data are presented as mean±SD. The χ, t test, and Pearson coefficients were calculated; as well as interobserver and intraobserver reproducibility (Cohen κ).

RESULTS

Seventeen of the 18 patients with sciatic nerve pain (S) presented foraminal stenosis (<40 mm) at the concavity of the fractional curve distal to the main lumbar structural curve. The symptomatic foramina were significantly smaller in height (7.8±2.5 vs. 12.1±3.1 mm, P<0.0001) and area (30.1±14.3 vs. 57.6±28.7 mm, P<0.0001) compared with asymptomatic foramen; 7/7 patients with femoral nerve pain (F) and lumbar structural curves (apex L3 or lower) had foraminal stenosis at the concavity of the fractional curve. Eight of the 9 patients with femoral nerve pain (F) and thoracic, thoracolumbar, or lumbar (apex L2 or higher) curves, presented foraminal stenosis in the concavity of the caudal fractional curve. The symptomatic foraminal spaces were significantly smaller in height (9.2±3.2 vs. 12.1±3.1 mm, P<0.0001) and area (30.1±15.2 vs. 57.6±28.7 mm, P<0.0001). Foraminal height correlated with foraminal area (r=0.68-0.85; P<0.0001). Interobserver agreement was between 0.6092 and 0.8679.

CONCLUSIONS

A correlation between curve types and symptomatic foraminal stenosis exists. Adult scoliosis patients with sciatic nerve pain typically present with foraminal stenosis at the concavity of the caudal fractional curve. Similarly, patients with femoral nerve pain present with foraminal stenosis at the concavity of the caudal fractional curve when the main structural curve is thoracic, thoracolumbar, or lumbar (apex L2 or higher).

Interpedicular height as a predictor of radicular pain in adult degenerative scoliosis

BACKGROUND CONTEXT

Spine surgeons must correlate clinical presentation with radiographic findings in a patient-tailored approach. Despite the prevalence of adult degenerative scoliosis (ADS), there are few radiographic markers to predict the presence of radiculopathy. Emerging data suggest that spondylolisthesis, obliquity, foraminal stenosis, and curve concavity may be associated with radiculopathy in ADS.

PURPOSE

The purpose of this study was to determine if radicular pain in ADS is associated with reduced interpedicular heights (IPHs) as measured on routine radiographs.

STUDY DESIGN/SETTING

This is a retrospective case-controlled study.

PATIENT SAMPLE

The authors carried out a retrospective chart review at a tertiary care referral center that included ADS patients referred to scoliosis surgeons between 2012 and 2014. Inclusion criteria included patients with ADS and no prior thoracolumbar surgery. Data were collected from initial spine surgeon clinic notes and radiographs.

OUTCOME MEASURES

Clinical outcome data included presence, side(s), and level(s) of radicular pain; presence of motor deficits; and presence of sensory deficits.

METHODS

Variables included age, gender, Scoliosis Research Society-30 (SRS-30) and Oswestry Disability Index (ODI) questionnaire data, and radiographic measurements. Radiographic measurements included Cobb angles and L1 to S1 IPHs on upright and supine radiographs. Associations between variables and outcome measures were assessed with univariate and multivariate statistical analyses. Authors have no conflicts of interests relevant to this study.

RESULTS

A total of 200 patients with an average age of 51 years met the inclusion criteria. Sixty of the 200 patients presented with radicular pain. Older age was associated with radicular pain, weakness, and sensory deficits. Patients who were 55 years or older were approximately eight times more likely to have radicular pain (odds ratio [OR]=7.96, 95% confidence interval [CI]: 3.73, 17.0; p<.001), five times more likely to have motor deficit (OR=5, 95% CI: 2.55, 9.79; p<.001), and five times more likely to have sensory deficit (OR=5.2, 95% CI: 2.65, 10.2; p<.001) than those younger than 55. More caudally located nerve roots are more likely to develop radicular pain (p<.001). Motor deficits were associated with worse SRS-30 functional (p=.02) and ODI scores (p=.005), but radicular pain and sensory deficits were not associated with lower SRS-30 or ODI scores. Ipsilateral and same-level radicular pain were associated with reduced IPH on supine radiographs (p=.002 and p=.0002, respectively). Finally, reduced IPH on upright radiographs was associated with side- and level-specific radicular pain (p=.04).

CONCLUSIONS

Radicular pain in ADS patients is associated with reduced IPHs and older age. Measuring IPHs on routine radiographs may be helpful in associating clinical radiculopathy with radiographic measures to guide patient management and surgical planning.

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.

Pelvic incidence: an anatomic investigation of 880 cadaveric specimens

PURPOSE

Pelvic incidence is a position- and posture-independent parameter used to quantify sagittal balance of the spine, sacrum, pelvis and hips. Its functional consequences have been associated with a number of different pathologies of the spine. However, there exists considerable controversy over which demographic features contribute to the development of pelvic incidence.

METHODS

880 cadaveric skeletons from the Hamann-Todd Osteological Collection were obtained. The innominate bones and sacrum were reconstructed, and pelvic incidence was measured using a previously validated technique. Specimens with obvious fracture, infection, or rheumatologic conditions were excluded from study. Descriptive data of age at the time of death, gender, race and height were collected.

RESULTS

The average pelvic incidence was 46.0° ± 11.0°. Pelvic incidence did not change with age (r = 0.026, p = 0.288). There was no difference in pelvic incidence measurements between females and males (47.2° ± 13.8° vs. 45.8° ± 10.4°, respectively; p = 0.257), although this analysis was under-powered. Pelvic incidence was higher in African-Americans compared to Caucasians (48.9° ± 11.0° vs. 44.9° ± 10.8°; p = 0.001). There was no association between height and pelvic incidence (r = -0.042, p = 0.164).

CONCLUSIONS

This study represents the largest single cohort of pelvic incidence measurements reported in the literature. Our data suggest that pelvic incidence does not change with age or height, although racial differences do exist. As spine care providers increasingly rely on pelvic incidence as an important means to quantify sagittal balance, the normative data provided herein will provide an essential reference.

Selective Thoracic Fusion of Lenke I and II Curves Affects Sagittal Profiles But Not Sagittal or Spinopelvic Alignment: A Case-Control Study

STUDY DESIGN

Literature review and retrospective case-control study (level 3 evidence) examining 50 adolescent idiopathic scoliosis (AIS) (Lenke I or II curve) cases with 32 healthy controls of the same age. The sagittal profiles were measured preoperatively, 6 months, and 2 years after surgery and compared with those of age-matched controls at baseline.

OBJECTIVE

The purpose of this study is to compare baseline sagittal profiles of AIS Lenke I and II curves with age-matched healthy controls and at 6 months and 2 years after surgery, as well as with previously published reports.

SUMMARY OF BACKGROUND DATA

Sagittal alignment and profiles have gained significant attention in spinal deformity outcomes. The sagittal profile of patients with AIS has been previously reported, as well as the effects of surgical correction, with inconsistent results and no clear references to nonscoliotic controls.

METHODS

Baseline sagittal profiles of 50 patients presenting with Lenke I or II AIS curves treated with selective thoracic fusion were compared with 32 age-matched controls without spinal pathology. These values were also measured at 6 months and 2 years postoperatively to examine effects of selective thoracic fusion over time. Sagittal parameters examined include pelvic incidence, pelvic tilt, C7 plumb line (sagittal vertical alignment), thoracic kyphosis, and lumbar lordosis. A literature review was performed comparing previously published data. Data are presented as mean (95% confidence interval). P value of less than 0.05 was considered significant.

RESULTS

Interobserver reliability (Cohen κ= 0.49-0.95). All demographic and preoperative sagittal alignment parameters were comparable between controls and patients with AIS prior to surgery. After selective thoracic fusion, thoracic kyphosis decreased significantly from baseline (25.4º [21.6-29.2] vs. 15.3º [12.8-17.8]; P < 0.001) at 6 months and at 2 years (10.3º [7.5-13.1]; P < 0.001). The lumbar lordosis significantly decreased at 6 months from baseline (54.5º [28.6-80.5] vs. 61.8º (33.4-90.1); P < 0.001) and at 2 years (55.4º [29.0-81.9]; P < 0.001). Sagittal vertical alignment, pelvic tilt, and pelvic incidence were comparable between controls and patients with AIS at baseline and did not change with surgery.

CONCLUSIONS

Adolescents with Lenke I or II curves have comparable sagittal profiles with those of healthy controls of the same age. This suggests that Lenke I and II curves may not be hypokyphotic as previously thought. After selective thoracic fusion, patients with AIS have a significantly decreased thoracic kyphosis, which is accompanied by reciprocal changes in the noninstrumented lumbar curve. Sagittal vertical alignment and pelvic tilt are not significantly affected. These results agree with previous reports, which suggest that constructs with pedicle screws have a higher impact on sagittal curves but do not affect sagittal or spinopelvic alignment. The long-term effects of abnormal sagittal profiles need further clarification.

LEVEL OF EVIDENCE

3.

A comparative analysis of sagittal spinopelvic alignment between young and old men without localized disc degeneration

INTRODUCTION

The purpose of this study was to compare the sagittal spinopelvic parameters between young normal asymptomatic adults and older normal asymptomatic adults without localized segmental disc degeneration.

MATERIALS AND METHODS

Standing sagittal radiographs of the whole spine including the pelvis in 342 adult male volunteers (Group 1: n = 184, average age 21.2 years, range 19-28 vs. Group 2: n = 158, average age 63.8 years, range 53-79) were analyzed prospectively. Volunteers with history of spine operation, spinal disease, chronic pain in their back or legs, scoliosis, spondylolisthesis, 1-3 segmental disc space narrowing, and/or compression fractures in radiographs were excluded. The following parameters were included: thoracic kyphosis between T5 upper endplate (UEP) and T12 lower endplate (LEP), thoracolumbar kyphosis (T10 UEP - L2 LEP), T12 LEP-horizontal (H) angle (minus denotes EP above the H line), lumbar lordosis (T12 LEP - S1 UEP), lower lumbar lordosis (L4 UEP - S1 UEP), sacral slope, pelvic incidence and distances from C7 plumb/T12 plumb to the postero-superior endplate of S1. Group 2 (old men group) demonstrated larger thoracic kyphosis (30.1° ± 8.6° vs. 21.1° ± 7.8° in Group 1, P < 0.001), thoracolumbar kyphosis (10.0° ± 7.5° vs. 2.8° ± 7.1° in Group 1, P < 0.001), total lumbar lordosis at T12-S1 (57.3° ± 8.8° vs. 52.2° ± 9.2° in Group 1, P < 0.001), lower lumbar lordosis at L4-S1 (39.4° ± 6.7° vs. 32.4° ± 6.4° in Group 1, P < 0.001), a higher ratio of lower to total lumbar lordosis (69.5 ± 11.6 vs. 62.7 ± 10.6 % in Group 1, P < 0.001) and T12 LEP-H angle (-20.4° ± 5.7° vs. -15.7° ± 5.1° in Group 1, P < 0.001). There were no significant differences in sacral slope (36.5° ± 7.3° in Group 1 vs. 36.8° ± 6.7° in Group 2, P = 0.67) and pelvic incidence (46.5° ± 7.7° in Group 1 vs. 48.2° ± 8.5° in Group 2, P = 0.06). There was no significant difference in the measurement of distance from C7 plumb to the postero-superior endplate of S1 (-0.7 ± 2.4 cm in Group 1 vs. -0.3 ± 2.7 cm in Group 2, P = 0.197). However, the distance from T12 plumb to the postero-superior endplate of S1 (-0.7 ± 1.7 cm in Group 1 vs. -2.2 ± 1.7 cm in Group 2, P < 0.001) demonstrated a significant difference.

CONCLUSION

The old men group demonstrated a significant increase in thoracic kyphosis, thoracolumbar kyphosis, total and lower lumbar lordosis, a higher ratio of lower to total lumbar lordosis, and a longer distance from T12 plumb to the postero-superior endplate of S1 without changes in sacral slope and global sagittal balance.

Sagittal spinal profile and spinopelvic balance in parents of scoliotic children

BACKGROUND CONTEXT

It is well known that spinal biomechanics and familial predisposition play an important role in the onset and evolution of idiopathic scoliosis. The relationship between the sagittal profile of the spine and spinal biomechanics has also been established in a number of studies. It has been suggested previously that a certain sagittal spinal configuration with implications for spinal rotational stiffness is inherited, thus providing a possible explanation for the well-known hereditary component in adolescent idiopathic scoliosis (AIS).

PURPOSE

To test the hypothesis that the familial trend in AIS may be partially explained by the inheritance of a sagittal spinal profile, which has been shown to make the spine less resistant to rotatory decompensation.

STUDY DESIGN

A prospective case controlled radiographic analysis of the sagittal profile of the spine and spinopelvic alignment.

PATIENT SAMPLE

One hundred two parents of scoliotic children, compared with 102 age-matched controls (parents of nonscoliotic children).

OUTCOME MEASURES

Physiologic measures: sagittal profile of the spine and spinopelvic alignment.

METHODS

Freestanding lateral radiographs of 51 parent couples of girls with severe (Cobb angle >30°) progressive AIS (AIS group) and 102 age-matched controls (control group) were taken. Parents with manifest spinal deformities or spinal pathology of any kind were excluded based on history or spinal X-ray to avoid distorted sagittal images with unreliable measurements. Values were calculated for thoracic kyphosis (T4-T12), lumbar lordosis (L1-L5), spinal balance (sagittal plumb line of C7 and T4, T1-L5 sagittal spinal inclination, T9 sagittal offset), curvature parameters (expressed in the area under the curve [AUC]), and pelvic parameters (pelvic tilt, pelvic incidence, and sacral slope). In addition, the height, offset, and length of the posteriorly inclined spinal segment, inclination of each vertebra, and normalized sagittal spinal profile were calculated. Differences in spinopelvic alignment between fathers and mothers of both groups were analyzed.

RESULTS

In the fathers of the AIS group, the plumb line of T4 was significantly less posteriorly positioned relative to the hip axis (79 mm vs. 92 mm; p=.009); the overall AUC and the lumbar AUC were significantly smaller (p=.002 and p=.008, respectively) as compared with the fathers in the control group. Vertebrae T11-L2 were significantly less backwardly inclined in the fathers of the AIS group (T11, L2: p<.05 and T12-L1: p<.01). An analysis of sagittal spinal profile showed a significantly flatter spine in the fathers of the AIS group (p=.01). No significant differences were observed in height, offset, and length of the backwardly inclined spinal segment. In the mothers of the AIS group, no statistically significant differences were observed in the spinopelvic parameters, spinal curvature, inclination of the vertebrae, and declive spinal segment parameters or sagittal spinal profile as compared with the mothers in the control group.

CONCLUSIONS

The sagittal spinal profile of the fathers of scoliotic children was significantly flatter than the sagittal spinal profile of fathers of nonscoliotic children. No difference was found in the sagittal spinal profile of the mothers of scoliotic children as compared with mothers of nonscoliotic children. Although it is well known that scoliotic mothers have an increased risk of having a scoliotic offspring, this study indicates that fathers may possibly contribute as well through their sagittal spinal profile to the inheritance of idiopathic scoliosis.

Increased pelvic incidence may lead to arthritis and sagittal orientation of the facet joints at the lower lumbar spine

BACKGROUND

Correct sagittal alignment with a balanced pelvis and spine is crucial in the management of spinal disorders. The pelvic incidence (PI) describes the sagittal pelvic alignment and is position-independent. It has barely been investigated on CT scans. Furthermore, no studies have focused on the association between PI and facet joint (FJ) arthritis and orientation. Therefore, our goal was to clarify the remaining issues about PI in regard to (1) physiologic values, (2) age, (3) gender, (4) lumbar lordosis (LL) and (5) FJ arthritis and orientation using CT scans.

METHODS

We retrospectively analyzed CT scans of 620 individuals, with a mean age of 43 years, who presented to our traumatology department and underwent a whole body CT scan, between 2008 and 2010. The PI was determined on sagittal CT planes of the pelvis by measuring the angle between the hip axis to an orthogonal line originating at the center of the superior end plate axis of the first sacral vertebra. We also evaluated LL, FJ arthritis and orientation of the lumbar spine.

RESULTS

596 individuals yielded results for (1) PI with a mean of 50.8°. There was no significant difference for PI and (2) age, nor (3) gender. PI was significantly and linearly correlated with (4) LL (p = < 0.0001). Interestingly, PI and (5) FJ arthritis displayed a significant and linear correlation (p = 0.0062) with a cut-off point at 50°. An increased PI was also significantly associated with more sagitally oriented FJs at L5/S1 (p = 0.01).

CONCLUSION

PI is not correlated with age nor gender. However, this is the first report showing that PI is significantly and linearly associated with LL, FJ arthritis and more sagittal FJ orientation at the lower lumbar spine. This may be caused by a higher contact force on the lower lumbar FJs by an increased PI. Once symptomatic or in the event of spinal trauma, patients with increased PI and LL could benefit from corrective surgery and spondylodesis.

Evaluation of pelvic morphology in the sagittal plane

BACKGROUND CONTEXT

It is generally accepted that for normal subjects the angle of pelvic incidence (PI) increases during childhood and then remains unchanged throughout adolescence and adulthood. However, recent findings show that PI increases linearly throughout the lifespan due to morphological changes of the pelvis.

PURPOSE

A retrospective study aiming to determine the extent of morphological changes of the pelvis related to the age of the subjects.

STUDY DESIGN

Pelvic morphology was evaluated in a normal adult population by measuring the anatomical parameters of sagittal pelvic alignment.

PATIENT SAMPLE

The final study cohort consisted of 330 subjects (mean age, 45.3 years; standard deviation, 18.1 years; range, 18-87 years; 164 male and 166 female subjects).

OUTCOME MEASURES

Physiologic measures, obtained as measurements of PI, sacral end plate width (S1W), and pelvic thickness (PTH).

METHODS

Parameters of PI, S1W, and PTH were evaluated from computed tomography images of the subjects. The measured PTH was normalized according to S1W and age of the subjects, allowing the comparison among anatomies of different sizes. The normalized components of PTH in anteroposterior and cephalocaudal directions were computed to determine the configuration and extent of changes in pelvic morphology related to subject age.

RESULTS

Statistically significant correlation with both age and PI was obtained for all normalized parameters (except for the anteroposterior component of PTH for male subjects), and no statistically significant differences were observed between the sexes. With increasing PI that occurs due to the aging process, a decrease of PTH can be observed that is manifested not only as an increase of the distance between the sacrum and the hip axis in the anterior direction but considerably more as a decrease of the distance between the sacrum and the hip axis in the cephalic direction. By considering these morphological changes in the pelvis simultaneously, the hip axis can move only within a narrow area.

CONCLUSIONS

The changes in pelvic morphology due to the aging process occur in the anterior direction, which may be due to the remodeling process affecting the coxal bone that results in an anterior drift of the acetabulum relative to the sacrum. More importantly, the changes are considerably more evident in the cephalic direction, which may be the result of the weight-bearing loads and consequent wear of acetabular cartilage.

Simple prediction method of lumbar lordosis for planning of lumbar corrective surgery: radiological analysis in a Korean population

PURPOSE

This study aimed at deriving a lordosis predictive equation using the pelvic incidence and to establish a simple prediction method of lumbar lordosis for planning lumbar corrective surgery in Asians.

METHODS

Eighty-six asymptomatic volunteers were enrolled in the study. The maximal lumbar lordosis (MLL), lower lumbar lordosis (LLL), pelvic incidence (PI), and sacral slope (SS) were measured. The correlations between the parameters were analyzed using Pearson correlation analysis. Predictive equations of lumbar lordosis through simple regression analysis of the parameters and simple predictive values of lumbar lordosis using PI were derived.

RESULTS

The PI strongly correlated with the SS (r = 0.78), and a strong correlation was found between the SS and LLL (r = 0.89), and between the SS and MLL (r = 0.83). Based on these correlations, the predictive equations of lumbar lordosis were found (SS = 0.80 + 0.74 PI (r = 0.78, R (2) = 0.61), LLL = 5.20 + 0.87 SS (r = 0.89, R (2) = 0.80), MLL = 17.41 + 0.96 SS (r = 0.83, R (2) = 0.68). When PI was between 30° to 35°, 40° to 50° and 55° to 60°, the equations predicted that MLL would be PI + 10°, PI + 5° and PI, and LLL would be PI - 5°, PI - 10° and PI - 15°, respectively.

CONCLUSION

This simple calculation method can provide a more appropriate and simpler prediction of lumbar lordosis for Asian populations. The prediction of lumbar lordosis should be used as a reference for surgeons planning to restore the lumbar lordosis in lumbar corrective surgery.

The analysis of spinopelvic parameters and stability following long fusions with S1, S2 or iliac fixation

PURPOSE

The purpose of this study was to analyse changes of spinopelvic parameters and stability in the treatment of degenerative lumbar deformity.

METHODS

A retrospective review was carried out on 70 cases of degenerative lumbar deformity treated by long fusion with uni-cortical S1 fixation alone (US1F group, n = 20), bi-cortical S1 fixation alone (BS1F group, n = 20), additional diagonal S2 fixation (DS2F group, n = 14), and additional iliac fixation (ILF group, n = 16) from July 2003 to April 2010. The sagittal vertical axis (SVA), lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), and stability were used to evaluate radiologic outcomes. The clinical outcome was evaluated using the Oswestry Disability Index (ODI).

RESULTS

In all groups, the LL was significantly increased at three months (p < 0.05). The PI and the SS of ILF patients significantly increased at three months (p < 0.05), while none of these values changed over time in non-ILF patients. The PT did not change postoperatively in any groups. The LL, SS, and PI were significantly greater in the ILF group at three months postoperatively and later (p < 0.05). DS2F and ILF had statistically significant stability compared to US1F and BS1F (p < 0.05). The ODI scores were significantly improved after surgery in all groups compared to before surgery (p < 0.05).

CONCLUSIONS

Patients who had ILF in long fusion for the treatment of degenerative lumbar deformity had significant restoration of spinopelvic parameters compared to the other groups. In addition, DS2F and ILF provided more stability of distal instruments.

Relationship between thoracic hypokyphosis, lumbar lordosis and sagittal pelvic parameters in adolescent idiopathic scoliosis

PURPOSE

Sagittal spine and pelvic alignment of adolescent idiopathic scoliosis (AIS) is poorly described in the literature. It generally reports the sagittal alignment with regard to the type of curve and never correlated to the thoracic kyphosis. The objective of this study is to investigate the relationship between thoracic kyphosis, lumbar lordosis and sagittal pelvic parameters in thoracic AIS.

METHODS

Spinal and pelvic sagittal parameters were evaluated on lateral radiographs of 86 patients with thoracic AIS; patients were separated into hypokyphosis group (n = 42) and normokyphosis group (n = 44). Results were statistically analyzed. The lumbar lordosis was lower in the hypokyphosis group, due to the low proximal lordosis. The thoracic kyphosis was not correlated with any pelvic parameters but with the proximal lordosis. The pelvic incidence was correlated with sacral slope, pelvic tilt, lumbar lordosis and highly correlated with distal lumbar lordosis in the two groups. There was a significant linear regression between thoracic kyphosis and proximal lordosis and between pelvic incidence and distal lordosis.

CONCLUSIONS

We can consider that the proximal part of the lordosis depends on the thoracic kyphosis and the distal part depends on the pelvic incidence. The hypokyphosis in AIS is independent of the pelvic parameters and could be described as a structural parameter, characteristic of the scoliotic deformity.

Current status of adult spinal deformity

Purpose To review the current literature for the nonoperative and operative treatment for adult spinal deformity. Recent Findings With more than 11 million baby boomers joining the population of over 60 years of age in the United States, the incidence of lumbar deformity is greatly increasing. Recent literature suggests that a lack of evidence exists to support the effectiveness of nonoperative treatment for adult scoliosis. In regards to operative treatment, current literature reports a varying range of improved clinical outcomes, curve correction, and complication rates. The extension of fusion to S1 compared with L5 and lower thoracic levels compared with L1 remains a highly controversial topic among literature. Summary Most adult deformity patients never seek nonoperative or operative treatment. Of the few that seek treatment, many can benefit from nonoperative treatment. However, in selected patients who have failed nonoperative treatment and who are candidates for surgical intervention, the literature reflects positive outcomes related to surgical intervention as compared with nonoperative treatment despite varying associated ranges in morbidity and mortality rates. If nonoperative therapy fails in addressing a patient's complaints, then an appropriate surgical procedure that relieves neural compression, corrects excessive sagittal or coronal imbalance, and results in a solidly fused, pain-free spine is warranted.

A modified sagittal spine postural classification and its relationship to deformities and spinal mobility in a chinese osteoporotic population

Background

Abnormal posture and spinal mobility have been demonstrated to cause functional impairment in the quality of life, especially in the postmenopausal osteoporotic population. Most of the literature studies focus on either thoracic kyphosis or lumbar lordosis, but not on the change of the entire spinal alignment. Very few articles reported the spinal alignment of Chinese people. The purpose of this study was threefold: to classify the spinal curvature based on the classification system defined by Satoh consisting of the entire spine alignment; to identify the change of trunk mobility; and to relate spinal curvature to balance disorder in a Chinese population.

Methodology/Principal Findings

450 osteoporotic volunteers were recruited for this study. Spinal range of motion and global curvature were evaluated noninvasively using the Spinal-Mouse® system and sagittal postural deformities were characterized.

Results

We found a new spine postural alignment consisting of an increased thoracic kyphosis and decreased lumbar lordosis which we classified as our modified round back. We did not find any of Satoh’s type 5 classification in our population. Type 2 sagittal alignment was the most common spinal deformity (38.44%). In standing, thoracic kyphosis angles in types 2 (58.34°) and 3 (58.03°) were the largest and lumbar lordosis angles in types 4 (13.95°) and 5 (−8.61°) were the smallest. The range of flexion (ROF) and range of flexion-extension (ROFE) of types 2 and 3 were usually greater than types 4 and 5, with type 1 being the largest.

Conclusions/Significance

The present study classified and compared for the first time the mobility, curvature and balance in a Chinese population based on the entire spine alignment and found types 4 and 5 to present the worst balance and mobility. This study included a new spine postural alignment classification that should be considered in future population studies.

Change in pelvic tilt angle 2 to 4 years after total hip arthroplasty

The purpose of this study was to evaluate the change in pelvic tilt angle (PA) in the sagittal plane in the standing and supine positions for 2 to 4 years after total hip arthroplasty (THA). Anteroposterior pelvic radiographs of 21 male and 65 female patients were investigated before and after THA yearly over 2 to 4 years. Both the standing and supine PA significantly posteriorly tilted after THA. The difference in PA between the standing and supine positions (dPA) significantly increased after THA. Although the PA in the standing and supine positions plateaued 1 year after THA, the dPA gradually increased. In addition, the percentage of patients who showed a difference of more than 10° in dPA tended to increase yearly. In particular, elderly female patients who showed posterior tilt in PA in the standing or supine positions or a large dPA before THA tended to show a dPA of more than 10° after THA.

A review of methods for evaluating the quantitative parameters of sagittal pelvic alignment

BACKGROUND CONTEXT

The sagittal alignment of the pelvis represents the basic mechanism for maintaining postural equilibrium, and a number of methods were developed to assess normal and pathologic pelvic alignments from two-dimensional sagittal radiographs in terms of positional and anatomic parameters.

PURPOSE

To provide a complete overview of the existing methods for quantitative evaluation of sagittal pelvic alignment and summarize the relevant publications.

STUDY DESIGN

Review article.

METHODS

An Internet search for terms related to sagittal pelvic alignment was performed to obtain relevant publications, which were further supplemented by selected publications found in their lists of references. By summarizing the obtained publications, the positional and anatomic parameters of sagittal pelvic alignment were described, and their values and relationships to other parameters and features were reported.

RESULTS

Positional pelvic parameters relate to the position and orientation of the observed subject and are represented by the sacral slope, pelvic tilt, pelvic overhang, sacral inclination, sacrofemoral angle, sacrofemoral distance, pelvic femoral angle, pelvic angle, and sacropelvic translation. Anatomic pelvic parameters relate to the anatomy of the observed subject and are represented by the pelvisacral angle (PSA), pelvic incidence (PI), pelvic thickness (PTH), sacropelvic angle (PRS1), pelvic radius (PR), femorosacral posterior angle (FSPA), sacral table angle (STA), and sacral anatomic orientation (SAO). The review was mainly focused on the evaluation of anatomic pelvic parameters, as they can be compared among subjects and therefore among different studies. However, ambiguous results were yielded for normal and pathologic subjects, as the reported values show a relatively high variability in terms of standard deviation for every anatomic parameter, which amounts to around 10 mm for PTH and PR; 10° for PSA, PI, and SAO; 9° for PRS1 and FSPA; and 5° for STA in the case of normal subjects and is usually even higher in the case of pathologic subjects. Among anatomic pelvic parameters, PI was the most studied and therefore represents a key parameter in the complex framework of sagittal spinal alignment and related deformities. From the reviewed studies, the regression lines for PI and the corresponding age of the subjects indicate that PI tends to increase with age for normal (PI = +0.17 × age+46.40) and scoliotic (PI = +0.20 × age+50.52) subjects and decrease with age for subjects with spondylolisis or spondylolisthesis (PI = -0.26 × age+75.69).

CONCLUSIONS

Normative values for anatomic parameters of sagittal pelvic alignment do not exist because the variability of the measured values is relatively high even for normal subjects but can be predictive for spinal alignment and specific spinopelvic pathologies.

Analysis of pelvic incidence from 3-dimensional images of a normal population

STUDY DESIGN

Pelvic incidence (PI) was measured in 3 dimensions from computed tomographic (CT) images of normal subjects using a computerized method.

OBJECTIVE

To obtain the angle of PI from 3-dimensional (3D) images and analyze its distribution in a normal population.

SUMMARY OF BACKGROUND DATA

The sagittal alignment of the pelvis is usually evaluated in 2-dimensional (2D) sagittal radiographs. The purpose of this study is to measure and analyze PI, which represents a key parameter of sagittal alignment, in 3D images.

METHODS

A computerized method, based on image-processing techniques, was used to automatically determine the anatomical references required to measure PI, that is, the centers of the femoral heads in 3 dimensions and the center and inclination of the sacral end plate in 3 dimensions. Multiplanar image reformation was applied to obtain perfect sagittal views with all anatomical structures completely in line with the hip axis from which PI was calculated.

RESULTS

PI was successfully obtained in CT images of 370 normal subjects (mean age: 41.5 years; range: 1-87 years). The mean PI (± standard deviation) was equal to 46.6° (±9.2°) for male subjects, 47.6° (±10.7°) for female subjects, and 47.1° (±10.0°) for both sexes. No statistically significant differences were obtained between the sexes, and statistically significant correlation was obtained between PI and age.

CONCLUSION

In this study, the sagittal alignment of the pelvis was evaluated in terms of PI completely in 3 dimensions. The results show that computerized measurements of PI in 3 dimensions are less variable than manual measurements. The large span of PI values for normal subjects indicates that the natural variation of PI is relatively large.