Predictive value of pelvic incidence in progression of spondylolisthesis

How much does an MRI change over a period of up to 2 years in patients with chronic low back pain? Is a repeated MRI really necessary in the follow-up of patients with chronic low back pain?

PURPOSE

Clinical practices vary between healthcare providers when it comes to asking for a Magnetic Resonance Imaging (MRI) during follow-up for chronic low-back pain (LBP). The association between progressive changes on the MRI and the clinical relevance of these findings is not clearly defined. The objective of our study is to investigate to what extent do MRI findings change during a period less than or equal to two years in patients with chronic LBP. We question the efficacy of its routinary use as a tool for follow-up and we also study the correlation between new changes on MRI and modifications in therapeutic attitude.

METHODS

Data was collected from 468 lumbar spine MRIs from 209 patients undergoing two or more MRIs between January 2015 and December 2019 with a mean of 2.24 MRIs per patient. The evaluated data included diagnosis, reason for request, MRI findings and treatment offered post-MRI. MRIs were assessed according to a standardized scoring system from 0 to 14 points according to the severity in findings (modified Babinska Score). Radiological changes were defined as increased severity of findings in the most affected segment.

RESULTS

51.06% of MRI requests had no documented reason to be asked for. The average score of the findings on the first MRI was 5,733 (SD 2,462) and 6,131 (SD 2,376) on the second, not reaching a statistically significant difference (p = 0.062). There was no difference on the findings between the first and the second MRI in 40, 15% (n = 104) and up to 89, 96% with only mild changes (-1/ + 2 points over 14 possibles). After repeating the MRI, no modification to the treatment plan was made in 44, 79% of patients (n = 116) and only in 11.58% (n = 30) was surgical treatment indicated.

CONCLUSION

The rate of lumbar MRI has risen to an alarming pace without evidence of consequent improvements in patient outcomes. A significant number of repeated MRIs did not show radiological changes, nor did they give rise to further surgical treatment after obtaining these images. This study should help to review the real applications of clinical guides on the appropriate use for image tests.

Lumbar Spondylolisthesis Grading: Current Standards and Important Factors to Consider for Management

Spondylolisthesis is a common condition with a prevalence of 4-6% in childhood and 5-10% in adulthood. The Meyerding Classification, developed in 1932, assigns grades (I to V) based on the degree of slippage observed on standing, neutral lateral lumbar radiographs. Despite its historical significance and reliability, more factors should be evaluated to predict spondylolisthesis progression, especially in low-grade cases. The manuscript highlights areas for improvement in spondylolisthesis classification, emphasizing the need for considering factors beyond vertebral slippage. Factors such as global and segmental alignment, pelvic incidence, overhang, the number of affected levels, and the use of lateral flexion-extension radiographs to assess for stability using the kyphotic angle and slippage degree are identified as crucial in predicting progression and determining effective management strategies.

Prevalence and Risk Factors of Degenerative Spondylolisthesis and Retrolisthesis in the Thoracolumbar and Lumbar Spine - An EOS Study Using Updated Radiographic Parameters

STUDY DESIGN

Single centre, cross-sectional study.

OBJECTIVES

The objective is to report the prevalence of spondylolisthesis and retrolisthesis, analyse both conditions in terms of the affected levels and severity, as well as identify their risk factors.

METHODS

A review of clinical data and radiographic images of consecutive spine patients seen in outpatient clinics over a 1-month period is performed. Images are obtained using the EOS® technology under standardised protocol, and radiographic measurements were performed by 2 independent, blinded spine surgeons. The prevalence of both conditions were shown and categorised based on the spinal level involvement and severity. Associated risk factors were identified.

RESULTS

A total of 256 subjects (46.1% males) with 2304 discs from T9/10 to L5/S1 were studied. Their mean age was 52.2(± 18.7) years. The overall prevalence of spondylolisthesis and retrolisthesis was 25.9% and 17.1% respectively. Spondylolisthesis occurs frequently at L4/5(16.3%), and retrolisthesis at L3/4(6.8%). Majority of the patients with spondylolisthesis had a Grade I slip (84.3%), while those with retrolisthesis had a Grade I slip. The presence of spondylolisthesis was found associated with increased age (P < .001), female gender (OR: 2.310; P = .005), predominantly sitting occupations (OR:2.421; P = .008), higher American Society of Anaesthesiology grades (P = .001), and lower limb radiculopathy (OR: 2.175; P = .007). Patients with spondylolisthesis had larger Pelvic Incidence (P < .001), Pelvic Tilt (P < .001) and Knee alignment angle (P = .011), but smaller Thoracolumbar junctional angle (P = .008), Spinocoxa angle (P = .007). Retrolisthesis was associated with a larger Thoracolumbar junctional angle (P =.039).

CONCLUSION

This is the first study that details the prevalence of spondylolisthesis and retrolisthesis simultaneously, using the EOS technology and updated sagittal radiographic parameters. It allows better understanding of both conditions, their mutual relationship, and associated clinical and radiographic risk factors.

Management of low back pain accompanying sagittal plane pathologies in children: Spondylolysis/spondylolisthesis and Scheuermann's disease

Background

Low back pain in childhood was underappreciated for a long time, but recent studies report higher prevalences, up to 70%. Two of the common causes are spondylolyis/spondylolisthesis and Scheuermann's disease. These disorders are relevant in a way they both cause significant back pain, and may disrupt the sagittal spinal balance.

Purpose

To present the current evidence on the diagnosis, natural history and treatment of these disorders with a special focus on sagittal spinal alignment.

Methods

This study is conducted as a literature review.

Results and Conclusions

Spondylolysis and low-grade spondylolisthesis have a benign course and are typically treated conservatively. When pars repair is indicated, pedicle screw-based techniques achieve more than 90% fusion with acceptable complication rates. High-grade spondylolisthesis, however, is frequently progressive. Surgical treatment involves fusion, which can be done in situ or after reduction. Reduction is useful for "unbalanced" patients to acquire sagittal spinopelvic balance, and it is important to distinguish these patients. Despite lowering the risk for pseudoarthrosis, reduction brings a risk for neurologic complications. With re-operation rates as high as 40%, these patients definitely require careful preoperative planning. Scheuermann's disease generally causes back pain in addition to cosmetic discomfort during adolescence. If the kyphosis is lower than 60°, symptoms typically resolve into adulthood with conservative measures only. However, it must be kept in mind that these patients may experience problems with physical performance and have a lower quality of life even when the problem seems to have "resolved". Severe kyphosis and intractable back pain are the most frequently referred surgical indications, and surgery typically involves fusion. Proper utilization of osteotomies and proper selection of the upper and lower fusion levels are of utmost importance to prevent complications in these patients.

Surgical management of high-grade paediatric spondylolisthesis: meta-analysis and systematic review

PURPOSE

There is currently no consensus on the management of high-grade spondylolisthesis (HGS) in paediatric populations. The objective of this analysis is to compare the outcomes of reduction followed by fusion (RFF) or in situ fusion (ISF) in paediatric patients.

METHODS

Using major databases, a systematic literature search was performed. Primary studies comparing ISF with RFF in paediatric and adolescent patients were identified. Study data including patient-reported outcomes, complications, and spinopelvic parameters were collected and analysed.

RESULTS

Seven studies were included, comprising 97 ISF and 131 RFF. Average patient age was 14.4 ± 2.1 years and follow up was 8.2 ± 5.1 years. Patients undergoing RFF compared to patients undergoing ISF alone were less likely to develop pseudarthrosis (RR 0.51, 95% CI, [0.26, 0.99], p = 0.05). On average, RFF led to 11.97º more reduction in slip angle and 34.8% more reduction in sagittal translation (p < 0.00001) compared to ISF. There was no significant difference between patient satisfaction and pain at follow up. Neurologic complications and reoperation rates were not significantly different.

CONCLUSIONS

Both RFF and ISF are effective techniques for managing HGS. Performing a reduction followed by fusion reduces the likelihood of pseudarthrosis in paediatric patients. The difference between risk of neurologic complications, need for reoperation, patient satisfaction, and pain outcomes did not reach statistical significance. Correlation with patient-reported outcomes still needs to be further explored. LEVEL 3 EVIDENCE: Meta-analysis of Level 3 studies.

Errors in the radiographic measurement of pelvic incidence

Pelvic incidence (PI) is often quantified in patients undergoing total hip arthroplasty. Errors in radiographic PI measurements can affect clinical outcomes. The purposes of this study were (1) to evaluate the error in radiographic PI measurement in patients with hip osteoarthritis (OA) and (2) to analyze the factors related to the error. Radiographs and computer tomography (CT) images of 100 patients (24 men and 76 women; mean age 63.7 years) with unilateral OA were reviewed. The error in radiographic PI measurement was defined as the difference between the radiographic measurement of the PI (rPI) and the accurate value of PI measured using CT images (cPI). Factors related to the error in the rPI were analyzed, including the coronal and axial rotation of the pelvis on lateral radiographs. The degree of coronal and axial rotation was expressed as the angle of rotation around the anteroposterior and craniocaudal axes. The mean rPI was significantly larger than the cPI (57.8° and 54.1°, p < 0.01). The error in the rPI was 3.6° on average and 15.8° at maximum. The mean coronal and axial rotation of the pelvis was 9.6° and 4.4°, respectively. The error in the rPI positively correlated with coronal pelvic rotation and rPI, and negatively correlated with axial pelvic rotation (p < 0.01, r = 0.35, 0.43, and -0.45, respectively). The rPI was 3.6° larger on average than the cPI in patients with hip OA. Coronal and axial rotation of the pelvis and a large PI were related to the error in the rPI.

Pelvic incidence measurement with supine magnetic resonance imaging: A validity and reliability study

OBJECTIVE

Classically, pelvic incidence (PI) and other spinopelvic sagittal parameters are measured using plain x-ray obtained with the patient standing. However, it is difficult to obtain a perfect mid-sagittal appearance of the sacral endplate and superimposition of both femoral heads from a plain x-ray. Overlapping of the iliac wings also could obscure the appearance of the sacral endplate. Recent studies showed that MRI was more reliable than x-ray for evaluating some spinal sagittal parameters. To our knowledge, measurements of spinopelvic sagittal parameters using supine MRI have not been reported previously. We assessed the validity and reliability of measurements of spinopelvic sagittal parameters from standing lateral x-rays and supine magnetic resonance imaging (MRI).

METHODS

We recruited 26 asymptomatic volunteers for this study. Standing lateral lumbosacral radiographs, including femoral heads and spinopelvic MRI images with coronal images of the femoral heads were performed. The anatomic reference point required to measure PI was found on coronal MRI images and transferred to the midline sagittal MRI using the bladder wall as a second reference point. PI, sacral slope (SS), and pelvic tilt (PT) were measured on x-ray and MRI images. Validity and reliability of results also were tested.

RESULTS

Of 14 males and 12 females (average age, 31.30), PI was obtained from x-ray and MRI in 52. ± 6.89 and 51.42 ± 6.43, respectively. From standing x-ray to supine MRI, PT decreased by 3.16°, while SS increased 2.5°. A paired t-test showed a significant difference between PT values from x-ray and MRI. The correlation was highest between the x-ray and MRI measurements of PI, PT, and SS, respectively. Intraobserver and interobserver reliabilities were between 0.88 and 0.96 on x-ray and MRI. All reliabilities were excellent, although MRI values were higher.

CONCLUSION

MRI was more reliable in the measurement of spinopelvic parameters than classic standing x-ray examination. Higher reliability and being radiation-free could make MRI a good alternative to standing x-ray.

Sagittal balance of the spine

Spinal balance can be defined as the trade-off between outside forces acting on the spine and the muscle response of the trunk, under sensorineural regulation, to maintain stable upright posture, both static and dynamic. Homo sapiens developed sagittal alignment along with bipedalism. The upright posture was an important step in human evolution, to master the environment, at the price of some instability in postural control in the trunk, and to maintain horizontal gaze. To make upright stance energetically economical and thus sustainable, reciprocal sagittal curvatures developed. Sagittal spinal organization is governed by strict rules under physiological conditions, enabling alignment between the center of mass and the lower limb joint centers. In children and adolescents, morphologic changes related to skeletal growth and postural control centers maturation alter spinal alignment and hence spinal balance, with increases in pelvic incidence, sacral slope and consequently lumbar lordosis and thoracic kyphosis. Global cervical lordosis remains stable, at the cost of an increase of the inferior cervical lordosis angle in correlation with T1 inclination or T1 slope. In pathology, spinal alignment may induce certain spinal pathologies such as growth-related spinal dystrophy or spondylolisthesis. It can also be altered by spinal deformity such as scoliosis, a regional disorder inducing adjacent compensatory mechanisms. The management of spinal pathologies is indissociable from understanding and maintaining or restoring individual sagittal alignment so as to ensure physiological distribution of stresses and limit onset of complications or decompensation in adulthood.

High-Grade Lumbar Spondylolisthesis

Most high-grade spondylolistheses are resultant from isthmic spondylolisthesis, as complete discontinuity of the pars is typically necessary to allow for this degree of anterior vertebral translation, although can occur less commonly in other scenarios. Higher-grade slips can affect the global sagittal balance of the patient and often result in altered gait patterns and compensatory posturing. Management usually entails surgical decompression and fusion with instrumentation. The addition of anterior column support carries many advantages, including greater surface area for fusion, dynamic compression load sharing at the lumbosacral junction, and a powerful adjunct for deformity correction.

What is the Risk of Developing Proximal Junctional Kyphosis During Growth Friendly Treatments for Early-onset Scoliosis?

BACKGROUND

Rib-based and spine-based systems are commonly used distraction-based growth friendly treatments for early-onset scoliosis (EOS). Our primary purpose was to determine the risk of developing postoperative proximal junctional kyphosis (PJK) during distraction-based growth friendly surgery.

METHODS

A multicenter, retrospective, radiographic comparison was performed for a group of 40 children with EOS who were treated with posterior distraction-based implants. PJK was defined as proximal junction sagittal angle (PJA)≥10 degrees and PJA at least 10 degrees greater than preoperative.

RESULTS

Eight subjects (20%) at immediate postoperative follow-up and 11 subjects (27.5%) at minimum 2-year follow-up had developed PJK. The risk of developing PJK between rib-based and spine-based growing systems was not significantly different at immediate postoperative (17% vs. 25%) or at final (25% vs. 31%) follow-ups.Further analysis combining both treatment groups demonstrated that PJK subjects were significantly older at time of initial surgery (7.1 y PJK vs. 5.0 y no PJK). Radiographic comparisons between PJK versus no PJK: Preoperative scoliosis (69.9 vs. 76.0 degrees), thoracic kyphosis (45.1 vs. 28.7 degrees), lumbar lordosis (53.1 vs. 44.0 degrees), PJA (2.2 vs. 2.8 degrees), sagittal vertical axis (1.5 vs. 2.6 cm), pelvic incidence (52.8 vs. 47.4 degrees), pelvic tilt (14.3 vs. 8.7 degrees), and sacral slope (37.7 vs. 35.9 degrees). At both initial postoperative and at final follow-up visits, a significant difference was found for cervical lordosis 32.2 versus 14.0 degrees and 42.0 versus 16.6 degrees, respectively. Risk ratio for developing PJK at final follow-up was 2.8 for subjects with preoperative thoracic hyperkyphosis and was 3.1 for subjects with high pelvic incidence (P<0.05).

CONCLUSIONS

The risk of developing PJK during distraction-based growth friendly treatment for EOS was 20% immediately after implantation and 28% at minimum 2-year follow-up, with no difference observed between rib-based and spine-based treatment groups. As this study identifies a significant risk of developing PJK during the treatment of EOS, it allows clinicians to preoperatively council patients and their families about this possible complication. In addition, several potential risk factors for the development of postoperative PJK were identified, but should be investigated further in future studies.

LEVEL OF EVIDENCE

Level III-therapeutic study (retrospective, comparative).

Increased and decreased pelvic incidence, sagittal facet joint orientations are associated with lumbar spine osteoarthritis in a large cadaveric collection

PURPOSE

Degenerative joint disease of the lumbar spine is a pervasive problem in healthcare; however, its aetiology and risk factors remain poorly defined. There have been recent attempts to correlate the anatomic parameters of facet angle and pelvic incidence with spine osteoarthritis, although data remains limited. The purpose of this experiment was to determine how age, gender, race, facet angle, tropism, and pelvic incidence correlate to facet joint osteoarthritis in the lumbar spine.

METHODS

A total of 576 cadaveric lumbar spines were obtained. Using validated techniques, facet angle, tropism, and pelvic incidence were measured. Osteoarthritis of the lumbar spines was graded from 0-4 at each level. Correlations between osteoarthritis and age, gender, facet angle, tropism, and pelvic incidence were evaluated with regression analysis.

RESULTS

Facet angle became more coronally oriented, and facet tropism increased from L1-L2 to L5-S1. Arthritis was highest at the L4-L5 joint (2.2 ± 1.1), compared to the L5-S1 (2.1 ± 1.1), L3-L4 (1.9 ± 1.1), L2-L3 (1.5 ± 1.0) and L1-L2 (1.0 ± 1.0) joints (p < 0.001). Age was the strongest predictor of arthritis at all levels (standardized betas 0.342 through 0.494, p < 0.001). Correlations between gender, race and osteoarthritis were not significant at any level. A decreased facet angle was predictive of increased arthritis at each joint level (standardized betas -0.091 through -0.153, p < 0.05 for all). Tropism was a predictor of increased arthritis at caudal levels. Pelvic incidence was a predictor of increased arthritis at L3-L4 (standardized beta 0.080, p = 0.02), L4-L5 (standardized beta 0.081,p = 0.02), and L5-S1 (standardized beta 0.100, p = 0.01).

CONCLUSIONS

Facet arthritis was correlated with a more sagittal orientation of the facet joints, increased tropism, and perturbations of pelvic incidence.

Increased Pelvic Incidence is Associated With a More Coronal Facet Orientation in the Lower Lumbar Spine: A Cadaveric Study of 599 Lumbar Spines

STUDY DESIGN

An anatomic study of facet angle orientation and morphology of the lumbar spine was performed.

OBJECTIVE

The aim of this study was to determine how age, gender, race, and pelvic incidence (PI) correlate with facet orientation in the lumbar spine.

SUMMARY OF BACKGROUND DATA

Lumbar facet orientation has important implications in the development of numerous pathologies of the spine, including arthritis, spondylolisthesis, and adult spinal deformity. Preliminary reports have suggested that sagittal balance of the spine may contribute to facet joint orientation. We therefore designed an anatomic study to investigate the relationship between PI and facet orientation, within the context of age, gender, and race.

METHODS

Five hundred ninety-nine cadaveric lumbar spines were obtained from the Hamann-Todd osteological collection. It was determined that facet angle was most reliably assessed by measuring the angle between the superior articular facet and the spinous process. Facet angles were measured bilaterally at each level from T12-L1 through L5-S1 in every specimen. Multivariate regression analysis was used to determine independent predictors of facet angle at each level.

RESULTS

Facet angle increased rostrally to caudally, from 22.6 ± 8.3° at T12-L1 to 49.1 ± 12.4° at L5-S1. Cadaver age was an independent predictor of a more sagittal facet angle at lower spinal levels. Caucasian race was an independent predictor of increasing facet angle. Increased PI had no effect on facet angle at T12-L1, L1-L2, L2-L3, or L3-L4, although was a significant predictor of more coronally oriented facet joints at L4-L5 (standardized beta 0.096, P = 0.009) and L5-S1 (standardized beta 0.079, P = 0.032).

CONCLUSION

The results of this study provide important data regarding differences in facet angle that exists between individuals. Moreover, the results of this study suggest that facet joints do possess the ability to remodel over time, perhaps in response to perturbations of sagittal balance, osteophyte formation, or other yet to be determined factors.

LEVEL OF EVIDENCE

N/A.

Radiographic Signs of Femoroacetabular Impingement Are Associated With Decreased Pelvic Incidence

PURPOSE

To investigate the relation between cam, acetabular version, and pelvic incidence.

METHODS

This was a retrospective analysis of 65 patients with symptomatic hip pain and radiographic signs of femoroacetabular impingement (FAI). Twenty-seven patients were used as a control. All patients received a CT scan of the pelvis that included the sacral endplate. Alpha angle, acetabular version, and pelvic incidence (PI) were measured on 2D CT. Patients were then assigned to 1 of 4 groups: control, cam (alpha angle > 55°, version > 15°), retroverted (alpha angle < 55°, version < 15°), or mixed (alpha angle > 55°, version < 15°).

RESULTS

The PI in mixed-type FAI was 46.7° ± 3.7°, which showed a statistically significant decrease from the PI of the control group, 56.1° ± 4.4° (P = .01). The PI for cam-only deformity was 50.8° ± 4.6°, and the PI for retroverted-only deformity was 51.0° ± 4.6°. Neither was statistically different from the control.

CONCLUSIONS

This study suggests that mixed-type FAI may develop as a response to decreased PI. This result is consistent with previous reports showing decreased PI associated with cam and retroversion deformities. Although the cause of FAI remains controversial, the potential impact of sagittal balance of the pelvis, and specifically, decreased PI, should not be ignored.

LEVEL OF EVIDENCE

Level IV, therapeutic case series.

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.

Surgical Treatment Strategies for High-Grade Spondylolisthesis: A Systematic Review

BACKGROUND

HGS is a severe deformity most commonly affecting L5-S1 vertebral segment. Treatment available for HGS includes a range of different surgical options: full or partial reduction of translation and/or abnormal alignment and in situ fusion with or without decompression. Various instrumented or non-instrumented constructs are available, and surgical approach varies from anterior/posterior to combined depending on surgeon preference and experience. The aim of this systematic review was to review the literature on lumbosacral high-grade spondylolisthesis (HGS), identify patients at risk for progression to higher-grade slip and evaluate various surgical strategies to report on complications and radiographic and clinical outcomes.

METHODS

Systematic search of PubMed, Cochrane and Google Scholar for papers relevant to HGS was performed. 19 articles were included after title, abstract, and full-text review and grouped to analyze baseline radiographic parameters and the effect of surgical approach, instrumentation, reduction and decompression on patient radiographic and clinical outcomes.

RESULTS

There is a lack of high-quality studies pertaining to surgical treatment for HGS, and a majority of included papers were Level III or IV based on the JBJS Levels of Evidence Criteria.

CONCLUSIONS

Surgical treatment for HGS can vary depending on patient age. There is strong evidence of an association between increased pelvic incidence (PI) and presence of HGS and moderately strong evidence that patients with unbalanced pelvis can benefit from correction of lumbopelvic parameters with partial reduction. Surgeons need to weigh the benefits of fixing the deformity with the risks of potential complications, assessing patient satisfaction as well as their understanding of the possible complications. However, further research is necessary to make more definitive conclusions on surgical treatment guidelines for HGS.

LEVEL OF EVIDENCE

II.

Correlation of pelvic incidence with radiographical parameters for acetabular retroversion: a retrospective radiological study

Background

Pelvic incidence (PI) has been linked to several degenerative processes within the spinopelvic system. Acetabular retroversion is a recognised risk factor for osteoarthritis of the hip. We therefore hypothesised that these two factors might be part of a specific anatomical variant associated with degenerative changes. This study was performed to clarify this issue.

Methods

The pelvic incidence was measured on 589 computertomographical data sets acquired between 2008 and 2010. For 220 patients a 2D rendering in an antero-posterior view of the CT data set was performed to evaluate the parameters of acetabular retroversion. Those included the prominence of the ischial spine sign (PRISS), the cross-over sign (COS) and the posterior wall sign (PWS). Between 477 and 478 hips were evaluated depending on the parameter of retroversion.

Results

The mean pelvic incidence was significantly lower in hips positive for the PRISS and the PWS. However, there were no significant differences between hips positive or negative for the COS.

Discussion

As hypothesised, the lower PI values in PWS and PRISS positive hips suggest a link between PI and retroversion of the acetabulum. Whether this is of any clinical relevance remains, however, unknown.

Conclusion

Acetabular retroversion is linked to PI. In hips where the prominence of the ischial spine sign and/or the posterior wall sign was present, the mean pelvic incidence value was lower.

Common normal variants of pediatric vertebral development that mimic fractures: a pictorial review from a national longitudinal bone health study

Children with glucocorticoid-treated illnesses are at risk for osteoporotic vertebral fractures, and growing awareness of this has led to increased monitoring for these fractures. However scant literature describes developmental changes in vertebral morphology that can mimic fractures. The goal of this paper is to aid in distinguishing between normal variants and fractures. We illustrate differences using lateral spine radiographs obtained annually from children recruited to the Canada-wide STeroid-Associated Osteoporosis in the Pediatric Population (STOPP) observational study, in which 400 children with glucocorticoid-treated leukemia, rheumatic disorders, and nephrotic syndrome were enrolled near glucocorticoid initiation and followed prospectively for 6 years. Normal variants mimicking fractures exist in all regions of the spine and fall into two groups. The first group comprises variants mimicking pathological vertebral height loss, including not-yet-ossified vertebral apophyses superiorly and inferiorly, which can lead to a vertebral shape easily over-interpreted as anterior wedge fracture, physiological beaking, or spondylolisthesis associated with shortened posterior vertebral height. The second group includes variants mimicking other radiologic signs of fractures: anterior vertebral artery groove resembling an anterior buckle fracture, Cupid's bow balloon disk morphology, Schmorl nodes mimicking concave endplate fractures, and parallax artifact resembling endplate interruption or biconcavity. If an unexpected vertebral body contour is detected, careful attention to its location, detailed morphology, and (if available) serial changes over time may clarify whether it is a fracture requiring change in management or simply a normal variant. Awareness of the variants described in this paper can improve accuracy in the diagnosis of pediatric vertebral fractures.

High-grade spondylolisthesis treated using a modified Bohlman technique: results among multiple surgeons

OBJECT

The ideal surgical management of high-grade spondylolisthesis remains unclear. Concerns regarding the original Bohlman transsacral interbody fusion technique with stand-alone autologous fibular strut include late graft fracture and incomplete reduction of lumbosacral kyphosis. The authors' goal was to evaluate the radiographic and surgical outcomes of patients treated for high-grade spondylolisthesis with either transsacral S-1 screws or standard pedicle screw fixation augmenting the Bohlman posterior transsacral interbody fusion technique.

METHODS

A retrospective review of patients who underwent fusion for high-grade spondylolisthesis in which a Bohlman oblique posterior interbody fusion augmented with either transsacral or standard pedicle screw fixation was performed by 4 spine surgeons was completed. Estimated blood loss, operating time, perioperative complications, and need for revision surgery were evaluated. Upright pre- and postsurgical lumbar spine radiographs were compared for slip percent and slip angle.

RESULTS

Sixteen patients (12 female and 4 male) with an average age of 29 years (range 9-66 years) were evaluated. The average clinical follow-up was 78 months (range 5-137 months) and the average radiographic follow-up was 48 months (range 5-108 months). Ten L4-S1 and 6 L5-S1 fusions were performed. Five fibular struts and 11 titanium mesh cages were used for interbody fusion. Six patients had isolated transsacral screws placed, with 2 (33%) of the 6 requiring revision surgery for nonunion. No nonunions were observed in patients undergoing spanning pedicle screw fixation augmenting the interbody graft. Six patients experienced perioperative complications including 3 iliac crest site infections, 1 L-5 radiculopathy without motor involvement, 1 deep vein thrombosis, and 1 epidural hematoma requiring irrigation and debridement. The average estimated blood loss and operating times were 763 ml and 360 minutes, respectively. Slip percent improved from an average of 62% to 37% (n = 16; p < 0.01) and slip angle improved from an average of 18° to 8° (n = 16; p < 0.01). No patient experienced L-5 or other motor deficit postoperatively.

CONCLUSIONS

The modified Bohlman technique for treatment of high-grade spondylolisthesis has reproducible outcomes among multiple surgeons and results in significant improvements in slip percent and slip angle. Fusion rates were high (14 of 16; 88%), especially with spanning instrumentation augmenting the oblique interbody fusion. Rates of L-5 motor deficit were low in comparison with techniques involving reduction of the anterolisthesis.

Sagittal balance, a useful tool for neurosurgeons?

New instrumentation techniques have made any correction of the spinal architecture possible. Sagittal balance has been described as an important parameter for assessing spinal deformity in the early 1970s, but over the last decade its importance has grown with the published results in terms of overall quality of life and fusion rate. Up until now, most of the studies have concentrated on spinal deformity surgery, but its use in the daily neurosurgery practice remains uncertain and may warrant further studies.

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.

Lumbar Spondylolysis and Spondylolisthesis in Down Syndrome: A Cross-sectional Study at One Institution

STUDY DESIGN

Retrospective cross-sectional study.

OBJECTIVES

To describe lumbar spondylolysis and spondylolisthesis and establish their prevalence in individuals with Down syndrome.

SUMMARY OF BACKGROUND DATA

Orthopedic problems in Down syndrome are variable and numerous. Lumbar spondylolysis and spondylolisthesis may be common conditions in Down syndrome. However, there has been a paucity of data on the association of these conditions in the published literature.

METHODS

A retrospective review of 110 patients with Down syndrome seen at a single institution from 2000 through 2012 was performed. Medical records, X-rays, and physician dictations were carefully reviewed to establish a detailed database of the study population.

RESULTS

Of the 110 patients in the study, 20 exhibited spondylolysis (unilateral, n = 11; bilateral, n = 9), whereas 38 had lumbar spondylolisthesis (isthmic, n = 9; dysplastic, n = 2; degenerative, n = 27). No gender difference was noted (p ≥ .7732). Fifteen patients reported low back pain (LBP) and/or leg pain. There was no significant association between LBP, leg pain, and spondylolysis (p = .9232). Both of these symptoms were highly predictive of lumbar spondylolisthesis, however (p = .0006). No significant findings were noted in pelvic parameters (pelvic incidence, sacral slope, pelvic tilt, or lumbar lordosis) in this study.

CONCLUSIONS

The prevalence of spondylolysis and spondylolisthesis in individuals with Down syndrome may be as high as 18.7% and 32.7%, respectively, significantly higher than in the non-Downs population. Etiopathogenesis of these conditions in Down syndrome does not appear to be related to pelvic parameters. Low back pain and leg pain may be more predictive of spondylolisthesis in Down syndrome than in the general population. Therefore, it is recommended that individuals with Down syndrome and LBP and/or leg pain be evaluated for lumbar spondylolisthesis.

The relationship between sagittal spinopelvic parameters and the degree of lumbar intervertebral disc degeneration in young adult patients with low-grade spondylolytic spondylolisthesis

We investigated the relationship between spinopelvic parameters and disc degeneration in young adult patients with spondylolytic spondylolisthesis. A total of 229 men with a mean age of 21 years (18 to 26) with spondylolytic spondylolisthesis were identified. All radiological measurements, including pelvic incidence, sacral slope, pelvic tilt, lumbar lordosis, sacral inclination, lumbosacral angle (LSA), and sacrofemoral distance, were calculated from standing lateral lumbosacral radiographs. The degree of intervertebral disc degeneration was classified using a modified Pfirrmann scale. We analysed the spinopelvic parameters according to disc level, degree of slip and disc degeneration.

There were significant positive correlations between the degree of slip and pelvic incidence (p = 0.009), sacral slope (p = 0.003) and lumbar lordosis (p = 0.010). The degree of slip and the LSA were correlated with disc degeneration (p < 0.001 and p = 0.003, respectively). There was also a significant difference between the degree of slip (p < 0.001) and LSA (p = 0.006) according to the segmental level of disc degeneration.

Cite this article: Bone Joint J 2013;95-B:1239–43.

The sagittal pelvic thickness: a determining parameter for the regulation of the sagittal spinopelvic balance

Objective. To propose and validate a dimensional parameter, the sagittal pelvic thickness (SPT) (distance between the middle point of the upper sacral plate and the femoral heads axis, expressed as a ratio with the length of the upper plate of S1: (SPT/S1) for the analysis of the sagittal balance of the pelvispinal unit. Methods. The parameters were analysed on standing radiographic imaging and compared for normal, low back pain, children, and spondylolysis cases. Results. Values of SPT/S1 were observed significantly higher in high grade spondylolysis populations and in children (3,5 and 3,7) than in normal population (3,3). A geometrical connection with the classical angular parameters validated SPT/S1. Conclusion. SPT/S1 was considered reflecting the lever arm of action of spinopelvic muscles and ligaments and describing the ability of a subject to compensate a sagittal unbalance. It was proposed as an anatomical and functional pelvic parameter.

Spondylolisthesis in Operative Adolescent Idiopathic Scoliosis: Prevalence and Results of Surgical Intervention

STUDY DESIGN

Retrospective, matched cohort.

OBJECTIVES

To evaluate patients with spondylolisthesis who underwent spinal fusion for adolescent idiopathic scoliosis (AIS); compare their overall satisfaction using the Scoliosis Research Society's outcome measure (SRS-22) with that of patients without spondylolisthesis; examine postoperative radiographs to determine slip progression and scoliotic correction; and provide a guide in choosing the lowest instrumented vertebral level.

SUMMARY OF BACKGROUND DATA

Spondylolisthesis has been reported to occur in 6.2% of patients with AIS. To the authors' knowledge, there is no prior matched-pair study comparing radiographic and clinical outcomes of patients who have undergone spinal fusion for AIS in the setting of spondylolisthesis.

METHODS

Records and radiographs of 349 patients with AIS treated with spinal fusion were reviewed to evaluate for spondylolisthesis. A set of matched controls with AIS but without spondylolisthesis was assembled. Data collected included Lenke curve type, curve magnitude, level and grade of spondylolisthesis, preoperative and postoperative slip angle, number of levels between the fusion and the spondylolisthesis, SRS-22 scores, curve correction, and slip progression.

RESULTS

Sixteen patients with operatively treated AIS (4.58%) also had spondylolisthesis. No patients with low-grade slips had progression of the slip at final follow-up of an average of 4 years. All fusions and listheses were separated by at least 3 levels. No significant differences were seen in postoperative SRS-22 scores between patients with AIS and those with AIS and spondylolisthesis.

CONCLUSIONS

Adolescent idiopathic scoliosis and spondylolisthesis can be treated independently. Powerful curve corrections can be obtained and maintained for at least 4 years in patients with AIS regardless of the presence of spondylolisthesis. Preserving motion of 3 levels between a posterior spinal fusion for AIS and a spondylolisthesis does not contribute to slip progression. According to SRS-22 questionnaire data, patients with concomitant AIS and spondylolisthesis who undergo spinal fusion procedures do well clinically.

Management of high-grade spondylolisthesis

Management of high-grade spondylolisthesis (HGS) remains challenging and is associated with significant controversies. The best surgical procedure remains debatable. Although the need for instrumentation is generally agreed upon, significant controversies still surround the role of reduction and anterior column support in the surgical management of HGS. Complications with operative management of HGS can be significant and often dictate the selection of surgical approach. This review highlights the pathophysiology, classification, clinical presentation, and management controversies of HGS, in light of recent advances in our understanding of the importance of sagittal spinopelvic alignment and technologic advancements.

L5 spondylolysis/spondylolisthesis: a comprehensive review with an anatomic focus

INTRODUCTION

Spondylolysis is most commonly observed in the lumbar spine, particularly L5, and is associated with spondylolisthesis, or anterior "slippage" of a vertebra in relation to an adjacent vertebra. Isthmic spondylolisthesis is the result of a pars interarticularis defect and will be the only type of spondylolisthesis addressed in this review.

CONCLUSIONS

Spondylolysis and spondylolisthesis represent a relatively common cause of low back pain, especially in young athletes, and a less common cause of neurologic compromise. When discovered in a symptomatic patient with corroborating imaging findings, early intervention provides an excellent prognosis. Herein, we review the anatomy and pathology of spondylosis and spondylolisthesis of the L5 vertebra.

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.

Biomechanical evaluation of predictive parameters of progression in adolescent isthmic spondylolisthesis: a computer modeling and simulation study

Background

Pelvic incidence, sacral slope and slip percentage have been shown to be important predicting factors for assessing the risk of progression of low- and high-grade spondylolisthesis. Biomechanical factors, which affect the stress distribution and the mechanisms involved in the vertebral slippage, may also influence the risk of progression, but they are still not well known. The objective was to biomechanically evaluate how geometric sacral parameters influence shear and normal stress at the lumbosacral junction in spondylolisthesis.

Methods

A finite element model of a low-grade L5-S1 spondylolisthesis was constructed, including the morphology of the spine, pelvis and rib cage based on measurements from biplanar radiographs of a patient. Variations provided on this model aimed to study the effects on low grade spondylolisthesis as well as reproduce high grade spondylolisthesis. Normal and shear stresses at the lumbosacral junction were analyzed under various pelvic incidences, sacral slopes and slip percentages. Their influence on progression risk was statistically analyzed using a one-way analysis of variance.

Results

Stresses were mainly concentrated on the growth plate of S1, on the intervertebral disc of L5-S1, and ahead the sacral dome for low grade spondylolisthesis. For high grade spondylolisthesis, more important compression and shear stresses were seen in the anterior part of the growth plate and disc as compared to the lateral and posterior areas. Stress magnitudes over this area increased with slip percentage, sacral slope and pelvic incidence. Strong correlations were found between pelvic incidence and the resulting compression and shear stresses in the growth plate and intervertebral disc at the L5-S1 junction.

Conclusions

Progression of the slippage is mostly affected by a movement and an increase of stresses at the lumbosacral junction in accordance with spino-pelvic parameters. The statistical results provide evidence that pelvic incidence is a predictive parameter to determine progression in isthmic spondylolisthesis.

Spondylolisthesis in twins: multifactorial etiology: a case report and review of the literature

STUDY DESIGN

Report of a high dysplastic developmental spondylolisthesis in two identical twins of two unrelated families.

OBJECTIVE

To investigate the multifactorial etiology of developmental spondylolisthesis.

SUMMARY OF BACKGROUND DATA

Multiple studies have suggested an association between a high pelvic incidence and the presence of isthmic spondylolisthesis. Other studies suggest a genetic background for spondylolysis and a pattern of inheritance of susceptibility to spondylolysis and spondylolisthesis. Heterozygous cartilage-derived morphogenetic protein-1 (CDMP-1) mutation has previously been associated with spondylolysis and severe spondylolisthesis.

METHODS

Two identical female twins presented with a developmental spondylolisthesis. Pelvic parameters, lumbar lordosis and grade of spondylolisthesis were calculated on a lateral standing spine radiograph. MRI is performed to confirm a high dysplastic developmental spondylolisthesis. Blood sample of these four individuals were analyzed for the presence of a CDMP-1 mutation, a cartilage-specific member of the TGF-b superfamily of secreted signaling molecules that plays a key role in chondrogenesis, growth, and patterning of the developing vertebrate skeleton.

RESULTS

PI, SS, PT, LL, and SI are significantly greater in all of these patients in comparison with the general population. Spinal MRI confirms a high dysplastic developmental spondylolisthesis in both twins. Mutation analysis of the two coding exons of CDMP-1 did not reveal any mutation in all four individuals.

CONCLUSION

To our knowledge, this is the first report of a high dysplastic developmental spondylolisthesis in identical twins. The presence of a high dysplastic developmental spondylolisthesis in two identical twins shows the convergence in etiology of different factors such as genetics, maturation, critical age, female sex, high pelvic incidence. Although we cannot confirm that CDMP-1 mutation plays a key role in the etiology of spondylolysis/spondylolisthesis, neither can we rule out that CDMP-1 problems may be an etiology for at least a subpopulation of patients. However, the presence of a developmental spondylolisthesis in two sets of identical twins still suggests a genetic susceptibility to spondylolysis and spondylolisthesis.

Spondylolysis and spondylolisthesis in children and adolescents

A review of the current literature shows that there is a lack of consensus regarding the treatment of spondylolysis and spondylolisthesis in children and adolescents. Most of the views and recommendations provided in various reports are weakly supported by evidence. There is a limited amount of information about the natural history of the condition, making it difficult to compare the effectiveness of various conservative and operative treatments. This systematic review summarises the current knowledge on spondylolysis and spondylolisthesis and attempts to present a rational approach to the evaluation and management of this condition in children and adolescents.

Redefining the technique for the radiologic measurement of slip in spondylolisthesis

STUDY DESIGN

Comparison of 2 radiographic measurement techniques of slip severity in spondylolisthesis.

OBJECTIVE

To analyze the differences between 2 radiologic measurement techniques of slip severity in L5-S1 developmental spondylolisthesis.

SUMMARY OF BACKGROUND DATA

Different techniques for the assessment of slip in spondylolisthesis have been described in the literature, resulting in 2 different methods to report the position of the L5 vertebra on the S1 superior endplate. The clinical impact of these differences in slip measurement is unknown.

METHODS

Radiographs of 130 subjects with developmental spondylolisthesis were reviewed. Two different techniques were used to assess the grade and percentage of slip. The technique 1 uses a line drawn from the L5 vertebra postero-inferior corner that is perpendicular to the S1 vertebra endplate. The technique 2 uses a line tangential to the L5 vertebra posterior wall that intersects the S1 vertebra endplate. The lumbosacral angle (LSA) was also measured to assess the orientation of L5 over S1. The slip percentage and grade obtained from the 2 techniques were compared. The influence of the LSA on the measurement of slip severity was also assessed.

RESULTS

A significant difference (P < 10(-5)) was found between technique 1 (mean = 34.2% +/- 32.6%) and technique 2 (mean = 42.5% +/- 25.8%) with respect to the slip percentage. Eight subjects were found to switch classification from a low to a high-grade slip (or inversely) depending on the technique used. There was a significant relationship between the LSA and the difference in the measurement of slip percentage using either technique 1 or technique 2.

CONCLUSION

The 2 measurement techniques can have a significant impact on the interpretation of slip severity in spondylolisthesis. The differences between the measurement techniques are influenced by the orientation of L5 over S1 and could potentially affect the clinical decision making. It is important to standardize and specify the technique used to plan and assess interventions in L5-S1 developmental spondylolisthesis.

Contemporary management of isthmic spondylolisthesis: pediatric and adult

BACKGROUND

Isthmic spondylolisthesis is common in pediatric and adult patients. Most cases are asymptomatic. When symptomatic, nonsurgical treatment is an appropriate first step. Surgical treatment of this condition varies depending on patient age, degree of slip, presence of neurologic findings, and degree of deformity.

PURPOSE

To review the literature on the management of isthmic spondylolisthesis in pediatric and adult patients.

STUDY DESIGN

Review article.

METHODS

Literature review.

RESULTS AND CONCLUSIONS

Achieving a solid fusion leads to improved functional outcomes and reduction in pain. A circumferential fusion is associated with a higher fusion rate and has become more common, especially with high-grade slips. The need for reduction is controversial and is mostly indicated for patients with significant lumbosacral kyphosis and sagittal imbalance.

Radiographic analysis of newly developed degenerative spondylolisthesis in a mean twelve-year prospective study

STUDY DESIGN

Prospective study of community-based female volunteers.

OBJECTIVE

To investigate the incidence of newly developed degenerative spondylolisthesis (DS) among those without baseline deformity, and to clarify radiographic characteristics and predictors of DS.

SUMMARY OF BACKGROUND DATA

There has been limited number of prospective studies of DS. Our on-going cohort study of healthy volunteers enabled long-term observation of highly susceptible perimenopause female subjects.

METHODS

A final total of 142 female subjects without spondylolisthesis at baseline radiographs were included and followed up for more than 8 years. Standardized serial entire spine radiographs were used to measure spinopelvic alignment, including pelvic incidence (PI), vertebral inclination angle, disc height, vertebral size, and facet orientation.

RESULTS

The incidence of newly developed DS was 12.7%. Comparison between DS and non-DS subjects demonstrated that DS subjects had significantly greater baseline lumbar lordosis, PI, vertebral inclination angle, and smaller vertebral size. Exaggerated lumbopelvic alignment was more prominent in L3-DS than in L4-DS, and L4-DS was associated with the decrease in L4/5 disc height. Multivariate analysis revealed that PI, L4 vertebral inclination, adjusted vertebral size, and facet sagittalization were independent predictors of the development of DS.

CONCLUSION

This was the first study to confirm the relationship of PI and the development of DS in a long-term prospective observation. Proposed pathogenetic differences might explain the fact that L4-DS is far more prevalent than L3-DS. The development of DS could be predicted by baseline lumbopelvic morphology among the highly susceptible perimenopause women.

A variability study of computerized sagittal sacral radiologic measures

STUDY DESIGN

A radiographic study was conducted to investigate the accuracy of computer-assisted measurement of sacral morphology in a population with developmental L5-S1 spondylolisthesis.

OBJECTIVE

The purpose of this study was to evaluate the inter- and intraobserver variability of computer measurements of sacral morphology.

SUMMARY AND BACKGROUND DATA

Recent studies have shown differences in sacral morphology among patients with spondylolisthesis. The sacral table angle (STA) is a fundamental sacral anatomic parameter that is specific and constant to each individual, while the S1 superior and S2 inferior angles are defined as anatomic measures specific to S1 and S2. Sacral kyphosis measured by Ferguson or Cobb method has also been used to evaluate the sagittal shape of the sacrum. Currently, computerized measures are gaining popularity for the study of sagittal balance, but their reliability especially in sacral morphology has never been properly evaluated.

METHODS

The standing lateral radiographs of 30 adolescents were randomly selected from the radiographic database of our institution: 10 radiographs of asymptomatic individuals, 10 of subjects with low grade L5-S1 spondylolisthesis and 10 with high grade L5-S1 developmental spondylolisthesis. Three surgeons measured sacral morphologic variables on the 30 radiographs at 2 occasions, with a 15 days interval between the 2 sessions, using a computer assisted technique. Intraclass correlation coefficients (ICCs) were used for statistical analysis.

RESULTS

The ICC values measured within observers varied between 0.951 to 0.995, whereas the ICC measured between observers varied between 0.957 to 0.995. There was a slight decrease of the ICC measured in the high grade L5-S1 spondylolisthesis group compared to the normal subjects. However, the difference was not statistically significant.

CONCLUSION

These results confirm the reliability and repeatability of computer-assisted angular measurement of sacral morphology in subjects with L5-S1 spondylolisthesis, even in the presence of lumbosacral junction dysplasia. The use of computerized measurements can be recommended for the evaluation of the sagittal sacral anatomy in future clinical and research studies.

Unilateral transforaminal lumbar interbody fusion: a review of the technique, indications and graft materials

Transforaminal lumbar interbody fusion (TLIF) is an alternative interbody fusion procedure in which interbody space is accessed via a path that runs through the far lateral portion of the vertebral foramen. TLIF reduces the potential complications of other approaches, including the transabdominal approach or posterior lumbar interbody fusion (PLIF), but still achieves clinical outcomes and circumferential fusion results comparable with PLIF. Operative indications for TLIF are contested among many spine experts. The optimal indications for using this technique are spondylolisthesis, degenerative disc disease with a specific discogenic pain pattern, lumbar stenosis with instability and recurrent lumbar disc herniation with radiculopathy. Various instrumentation techniques and graft materials are available to use in TLIF, and each option has benefits and disadvantages. Further research is needed, however, TLIF with one cage and excised local bone and augmented with a bilateral pedicle screw seems to be an effective and affordable treatment.

Influence of sacral morphology in developmental spondylolisthesis

STUDY DESIGN

A radiographic study was conducted to investigate sacral morphology in a children and adolescent population with developmental L5-S1 spondylolisthesis.

OBJECTIVE

To determine the relationship between sacral morphology and developmental L5-S1 spondylolisthesis.

SUMMARY AND BACKGROUND DATA

The morphology of the adult sacrum has been recently shown to be abnormal in low grade spondylolisthesis. However, sacral morphology has never been evaluated in a pediatric population where remodeling and secondary changes are less pronounced. It remains unknown if these changes in sacral morphology are primary or secondary in developmental L5-S1 spondylolisthesis.

METHODS

The lateral standing radiographs of 131 subjects, aged 6 to 20 years old with developmental L5-S1 spondylolisthesis (91 low grade and 40 high grade) were analyzed with a dedicated software allowing to measure the following parameters, which were analyzed for each subject by the same individual and compared to a cohort of 120 subjects without any spinal pathology with similar age and sex distribution: the sacral table index (STI), sacral table angle (STA), sacral kyphosis (SK), S1 superior angle, S2 inferior angle, and grade of spondylolisthesis. Student t test was used to compare the parameters between the groups.

RESULTS

This study demonstrated that STA is significantly smaller (P < 0.01) in children and adolescents with L5-S1 spondylolisthesis compared to a similar control group. Furthermore, STA is significantly smaller in high-grade spondylolisthesis when compared to subjects with low grade. There is also a significant difference in segmental sacral morphology (S1 and S2 anatomy) in the spondylolisthesis group. Increasing sacral kyphosis is also found to be significantly associated with spondylolisthesis.

CONCLUSION

The sagittal sacral morphology is a constant anatomic variable specific to each individual and unaffected by the position of the patient in space. The anatomy of the sacrum in children and adolescents with L5-S1 spondylolisthesis is particular and different from a control group. This study suggests that sacral anatomy may have a direct influence on the progression of spondylolisthesis; a lower STA and higher sacral kyphosis may be 2 factors predisposing to vertebral slip in developmental spondylolisthesis.

Use of pelvic incidence as a guide to reduction of H-type spino-pelvic dissociation injuries

OBJECTIVE

Describe the use of a radiographic parameter (pelvic incidence) to assess the sagittal plane reduction of H-type sacral fractures associated with spinopelvic dissociation, and assess the relationship between standing lumbar lordosis to pelvic incidence after spinopelvic dissociation.

DESIGN

Retrospective radiographic and clinical review of treatment outcomes for patients with spinopelvic dissociation injuries secondary to H-type sacral fractures.

SETTING

Level I Trauma Center.

INTERVENTION

Pelvic incidence (PI), a radiographic parameter that measures the orientation of the lumbar spine relative to the pelvis, has been shown to have a correlation with the adequacy of surgical reduction as well as the risk of progression of high-grade spondylolisthesis. We used this parameter as a measure of sagittal plane reduction of spinopelvic dissociation injuries.

PATIENTS/PARTICIPANTS

The clinical records and radiographs of five patients with spinopelvic dissociation injuries were reviewed.

MAIN OUTCOME MEASUREMENTS

Radiographic measurements included standing PI and lumbar lordosis (LL). The relationship of lumbar lordosis on pelvic incidence was tested by a regression analysis. Clinical outcome was assessed by the self-reported ability of the patient to comfortably maintain an upright stance.

RESULTS

The average follow-up period was 32 (range: 12-53) months. The average final PI was 82 (60-115) degrees. The average final lumbar lordosis was 58.2 (42-77) degrees. LL was found to be significantly related to PI (P<0.05). One patient with an abnormally high PI had lumbar fatigue with persistent stance.

CONCLUSIONS

Pelvic incidence is a potentially useful radiographic parameter that can be used to assess the adequacy of sagittal plane reduction in patients with spinopelvic dissociation injuries.

A novel approach to sagittal balance restoration following iatrogenic sacral fracture and resulting sacral kyphotic deformity

✓The authors describe the use of sacral pedicle subtraction osteotomy (PSO) with multiple sacral alar osteotomies for the correction of sacral kyphosis and pelvic incidence and for achieving sagittal balance correction in cases of fixed sagittal deformity after a sacral fracture.

In this paper, the authors report on a novel technique using a series of sacral osteotomies and a sacral PSO to correct a fixed sagittal deformity in a patient with a sacral fracture that had healed in a kyphotic position. The patient sustained this fracture after a previous surgery for multilevel instrumented fusion. Preoperative and postoperative radiographic studies are reviewed and the clinical course and outcome are presented.

Experts agree that the pelvic incidence is a fixed parameter that dictates the morphological characteristics of the pelvis and affects spinopelvic orientation and sagittal spinal alignment. An increased pelvic incidence is associated with a higher degree of spondylolisthesis in the lumbosacral junction, and increased shear forces across this junction. The authors demonstrate that the pelvic incidence can be altered and corrected with a series of sacral osteotomies to improve sacral kyphosis, compensatory lumbar hyperlordosis, and sagittal balance.

Intra and inter-observer reliability of determining degree of pelvic incidence in high-grade spondylolisthesis using a computer assisted method

Pelvic incidence was described as a fundamental parameter to describe spino-pelvic balance. In high-grade spondylolisthesis, severe dystrophic changes of the upper sacral endplate may be responsible for technical difficulties in pelvic incidence measurement. We propose to evaluate the reliability of PI measurement in high-grade spondylolisthesis patients and to compare the manual method with a computer-assisted method. In 30 high-grade spondylolisthesis patients, pelvic incidence was measured by manual and computer-assisted technique by the Spineview software package. We statistically assessed agreement between the manual and the computer-assisted technique, the intra-observer and the inter-observer reliability of the computer-assisted technique. Significant correlation was found (Spearman's rank R = 0.921 with P<0.001) between manual and computer-assisted results. The paired t test (t = 0.979 with P<0.001) and the intraclass correlation coefficient (ICC) were also significant. Intra- and inter-observer reliability of the computer-assisted technique were excellent with Spearman's rank correlation from 0.964 to 0.985 with P<0.001, a paired t test from 0.978 to 0.983 with P<0.001) and an ICC from 0.986 to 0.992. Intra- and inter-observer repeatability were better with the computer-assisted method than with the manual technique. We proved the reliability and repetability of a computer-assisted angular measurement method in high-grade spondylolisthesis patients. This validated measurement technique could be now used to measure the main parameters of the sagittal balance of the spine in further studies on spondylolisthesis patients.

The femoro-sacral posterior angle: an anatomical sagittal pelvic parameter usable with dome-shaped sacrum

The sagittal pelvic morphology modulates the individual alignment of the spine. Anatomical angular parameters were described as follows: the "Pelvic Incidence" (PI) and the Jackson's angle "Pelvic Lordosis" (PR-S1). Significant chains of relationships were expressed connecting these angles with pelvic and spinal positional parameters. This allows an individual assessment of the harmony of the sagittal spinal balance. But in case of spondylolysis with high-grade listhesis, the upper plate of the sacrum shows a dome-shaped deformity. The previous anatomical parameters are therefore imprecise. Indeed, the anterior part of the sacrum being inaccurate, an exact assessment of these angles becomes impossible. Therefore, we propose a new angular parameter named "Femoro-Sacral Posterior Angle" (FSPA): the angle between the posterior wall of the first sacral vertebra, always well definite, and the line connecting the posterior part of the sacral plate to the femoral axis. The validation of this parameter was performed and compared with the classical published parameters. It showed good inter-observer reliability, even with dome-shaped sacral plate. In spite of lower correlation with the positional parameters than those observed with PI or PR-S1, the FSPA appeared to be reliable and precise for an exact evaluation of the sagittal spino-pelvic balance is case of spondylo-listhesis with dome-shaped sacral endplate.