Radiographic classification of L5 isthmic spondylolisthesis as adolescent or adult vertebral slip

Imaging predictors of progression of lumbar spondylolysis to spondylolisthesis: a systematic review

BACKGROUND CONTEXT

Isthmic spondylolisthesis (IS) is defined as the anterior translation of one lumbar vertebra relative to the next caudal segment as a result of a unilateral or bilateral fracture of the pars interarticularis. These fractures are interchangeably known as "pars defects" or "spondylolysis." Many risk factors have been proposed to explain the progression of a spondylolytic defect to IS, however, none are validated.

PURPOSE

This systematic review provides an overview of various radiological and imaging parameters that can help predict the risk of progression of a spondylolytic defect into IS.

STUDY DESIGN

Systematic review.

METHODS

Medline, Embase and Cochrane online database were searched. The various correlations between imaging features with observed spondylolisthesis prevalence or severity or spondylolysis rates of spondylolisthesis were evaluated to provide a list of imaging risk factors to predict IS. Significance of the correlations in the original article was recorded to enable comparison of the collected evidence of separate image features.

RESULTS

All searches combined generated a total of 431 results of which 26 articles were included into this study. Of the 22 potential risk factors identified, 5 were found to be statistically insignificant, 8 were found to be significant and 9 had mixed results. The following features were found to be significant risk factors in at least on study: disc degeneration, transverse process width, pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, lumbar index, thoracic kyphosis, facet joint angle above the level of defect, facet joint degeneration, facet tropism, multifidus size, lateral erector spinae size, mesenteric fat thickness, subcutaneous fat thickness and soft tissue calcification.

CONCLUSION

Our research suggests that only disc degeneration had moderately strong evidence with consistent significant associations with development of IS in patients with spondylolysis. Transverse process width, pelvic incidence, pelvic tilt, sacral slope, lumbar lordosis, lumbar index, thoracic kyphosis, facet joint angle above the level of defect, facet joint degeneration, facet tropism, multifidus size, lateral erector spinae size, mesenteric fat thickness, subcutaneous fat thickness and soft tissue calcification had some evidence. All other radiological factors had weak evidence. The results of this study can be used to improve early clinical decision making for patients with spondylolysis.

Normal spino-pelvic parameters and correlation between lumbar lordosis (LL) and pelvic incidence (PI) in children and adolescents in Indian population

PURPOSE

The purpose of this work is to describe normal spino-pelvic parameters for pediatric and adolescent Indian population (and compare it with a cohort of different ethnicity) and to find out the correlation of pelvis incidence (PI) and lumbar lordosis (LL) METHODS: 129 asymptomatic subjects (66 males, 63 females) with age 4-15 years were studied. Pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and lumbar lordosis (LL) were measured on lateral whole-spine standing radiographs using computer software and compared in relation to age, sex, and ethnicity. Using correlation and regression analysis, the association and predictability of LL with PI was studied within the entire sample and then among age groups 4-10 and 11-15 years.

RESULTS

Mean PI was 42° ± 8.1°, whereas PT and SS were 12.9° ± 7.8° and 29.3° ± 9.62°, respectively. PI and SS were lower (p < 0.0001), but PT was higher than Caucasians. Overall PI remained unchanged in the age group > 10 years in comparison to the younger age. Mean PT was lower (p = 0.0020), but SS and LL were higher (p = 0.0027 and p = 0.0002 respectively). Angular spino-pelvic parameters were similar between sex groups. Overall correlation between PI and LL was 0.4 (p < 0.0001) which was 0.1 (p = 0.2345) and 0.5 (p < 0.0001) for ages 4-10 and 11-15 years, respectively. Overall, the prediction of PI based on LL is not very accurate with a simple linear term between PI and LL (R² = 0.1) and only improve marginally with a restricted cubic spline function.

CONCLUSIONS

In pediatric and adolescent' population, ethnicity and age-related variations of normal sagittal spino-pelvic parameters exist and should be considered in patient management.

Sacropelvic Parameters and L5 Spondylolysis: Computed Tomography Analysis

Study Design

Retrospective analysis of computed tomography scans.

Purpose

This study aims to determine the association of sagittal sacropelvic parameters with L5 spondylolysis.

Overview of Literature

The association of increased pelvic incidence (PI) and decreased sacral table angle (STA) with spondylolysis has been reported, but no study has simultaneously analyzed multiple sacropelvic variables to compare their association.

Methods

In this study, computed tomography scans obtained to assess major trauma in patients aged >16 years were analyzed. Scans meeting one of the following criteria were excluded: abnormal anatomy, previous spine or hip/pelvis surgery, or spinal pathology, including deformity, infection, tumor, or trauma. sacral anatomic orientation (SAO), PI, pelvic thickness (PTH), femoro-sacral posterior angle (FSPA), STA, and sacral kyphosis (SK) were measured.

Results

Overall, 202 scans were analyzed: 25 with L5 spondylolysis and 177 normal. Among the groups, a significant difference was observed in SAO (43.3° vs. 51.6°), PI (61.7° vs. 49.8°), STA (95.4° vs. 101.8°), and SK (31.0° vs. 23.7°). Based on the logistic regression analysis, only PI (odds ratio [OR], 1.074; 95% CI, 1.026–1.124) and STA (OR, 0.822; 95% CI, 0.734–0.920) remained significant predictors for the presence of spondylolysis. In the spondylolysis group, PI correlated significantly with PTH (r=−0.589), FSPA (r=0.880), and SK (r=0.576), whereas in the normal group, PI correlated significantly with FSPA (r=0.781) and SK (r=0.728).

Conclusions

By simultaneously assessing multiple sacropelvic parameters, we associated increasing PI with L5 spondylolysis. Decreasing STA, which likely represents a chronic remodeling secondary to spondylolysis, was also associated with increased risk. Back pain in an adolescent or young adult with high PI or low STA should raise suspicion of a possible occult spondylolysis.

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.

Comparison of the sacral table angles by progression stage of lumbar spondylolysis

STUDY DESIGN

Retrospective study.

OBJECTIVES

The purpose of this study was to investigate sacral table angle (STA) values in early-stage spondylolysis. Several studies suggested that the STA of patients with L5 spondylolysis or spondylolisthesis was significantly lower than that of healthy controls. Separation of the pars interarticularis creates shear stress between the upper sacral end plate and L5 vertebra. This was considered the cause of low STA in patients with spondylolysis or spondylolisthesis. However, if a low STA value is obtained in the early stage of L5 spondylolysis, it suggests that low STA does not result in the remodeling of the sacral end plate.

METHODS

Patients with L5 spondylolysis and those with low back pain without pars defect were retrospectively identified from a hospital database in 2014-2016. Pars defect of the spondylolysis was classified into three categories based on CT and MRI results: early, progressive, or terminal stage. The STA difference between groups was calculated using one-way analysis of variance and Scheffe F test, which were used for post hoc testing.

RESULTS

A total of 84 cases of L5 spondylolysis and 70 cases of low back pain were identified. No significant difference was found between the STAs of the early- or progressive-stage spondylolysis and the terminal-stage L5 spondylolysis and low back pain patients. The STA of the terminal-stage L5 spondylolysis was significantly lower than that of low back pain patients.

CONCLUSIONS

In conclusion, patients with early- or progressive-stage spondylolysis do not have low STA. Low STA is seen only in patients with terminal-stage spondylolysis, suggesting that low STA is associated with remodeling changes in response to shear force after onset of spondylolysis. STA value might not important as a prognostic parameter about development of the spondylolysis.

LEVEL OF EVIDENCE

Level IV.

EFFECTS OF SAGITTAL BALANCE DIFFERENCES ON SPONDYLOLISTHESIS

OBJECTIVES

This study aimed to compare the lumbar lordosis (LL) and spinopelvic parameters of patients with stage 1-2 spondylolisthesis to those of the normal population and demonstrate the importance of these parameters in sagittal balance.

METHODS

The lumbosacral parameters on the lateral radiographs of a total of 125 patients were retrospectively compared. Lumbosacral parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis angle (LLA), L5 incidence (L5I), L5 slope (L5S), and sacral table angle (STA) were compared between groups.

RESULTS

Comparison of the parameters between groups revealed no sex-based differences (p > 0.05).

CONCLUSIONS

Abnormal sagittal spinopelvic parameters are commonly examined for their effects on the development of spondylolisthesis and should be used in routine practice. We found that the low SS values in our study, unlike those of other similar studies, may be a compensatory mechanism developed to reduce pain and maintain sagittal balance. Level of Evidence II; retrospective study.

Association Between Lumbar Spinal Degeneration and Anatomic Pelvic Parameters

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

The objective was to prove the association between anatomic pelvis parameters and specific types of lumbar spinal degeneration.

SUMMARY OF BACKGROUND DATA

Different spinopelvic sagittal profile types are suggested to be associated with specific degenerative lumbar spine pathologies. Because pelvic morphology plays a key role defining the spinal shape as well as its load and function it thereby potentially predisposes the development of spinal degeneration.

MATERIALS AND METHODS

Patients with symptomatic lumbar spinal degeneration who were surgically treated in 2 spine departments from March 2011 until August 2016 were included in this retrospective analysis. Single-level degenerative pathologies were classified as lumbar disc herniation (LDH), degenerative disc disease (DDD), lumbar spinal stenosis (LSS), and degenerative spondylolisthesis (DSPL). The constant anatomic pelvic parameters pelvic incidence (PI), pelvic radius (PR), and sacral table angle (STA) were assessed in lateral radiographs of the lumbar spine and compared between the pathologies.

RESULTS

In total, 249 patients were assigned to the LDH (n=73), DDD (n=67), LSS (n=42), and DSPL (n=67) groups. Group comparisons revealed significant differences in the anatomic pelvic parameters PR (LDH, 139.5±10.8 mm; DDD, 135.9±14.0 mm; LSS, 127.8±14.3 mm; DSPL, 135.8±12.7 mm; P<0.001), PI (LDH, 53.1±10.0 degrees; DDD, 50.0±9.9 degrees; LSS, 54.5±9.6 degrees; DSPL, 57.1±10.8 degrees; P=0.001), and STA (LDH, 95.3±12.7 degrees; DDD, 105.4±9.0 degrees; LSS, 105.9±11.5 degrees; DSPL, 98.6±9.5 degrees; P<0.001). Post hoc tests indicated significant differences between the PR of the LSS group and that of all other subgroups (P<0.012), the PI of the DDD group and that of DSPL (P<0.001), and the STA of the LDH/DSPL groups and that of the LSS/DDD group (P<0.005).

CONCLUSIONS

We found all the constant anatomic parameters to be specific for distinct types of degeneration, suggesting pelvis shape is a predisposing factor for their development.

LEVEL OF EVIDENCE

Level III.

Proximal sacral deformity: a common element in lytic isthmic spondylolisthesis at L5 and in degenerative spondylolisthesis at L4-L5 segment. Two apparently very different etiopathogenic entities

A radiographic study was carried out to investigate the relationship between proximal sacral sagittal anatomy (either kyphosis or lordosis) and either isthmic or degenerative spondylolisthesis. In addition, we studied whether there is a relationship between proximal sacral kyphosis and the degree of such listhesis in the case of L5 isthmic spondylolisthesis. Lateral standing x-rays were used from 173 patients, ninety of whom had degenerative spondylolisthesis L4-L5, and eighty-three an isthmic spondylolisthesis of L5 (67 low-grade and 16 high-grade) and compared with a control group of 100 patients adjusted by age and gender, without any type of spondylolisthesis. Listhesis was graded using Meyerding's classification and the proximal sacral kyphosis angle (CSP) was measured between S1 and S2 posterior walls, according to Harrison's method. In our series, there was a proximal sacral kyphosis in both types of spondylolisthesis, greater in the lytic type. By contrast, the control group had a proximal sacral lordosis. The differences were statistically significant. Therefore, we concluded that there was a proximal sacral kyphosis in patients with both degenerative and isthmic lytic spondylolisthesis, but with our results, we were not able to ascertain whether it is a cause or a consequence of this listhesis.

Differences of Sagittal Lumbosacral Parameters between Patients with Lumbar Spondylolysis and Normal Adults

BACKGROUND

Recent studies have suggested an association between elevated pelvic incidence (PI) and the development of lumbar spondylolysis. However, there is still lack of investigation for Han Chinese people concerning the normal range of spinopelvic parameters and relationship between abnormal sagittal parameters and lumbar diseases. The objective of the study was to investigate sagittal lumbosacral parameters of adult lumbar spondylolysis patients in Han Chinese population.

METHODS

A total of 52 adult patients with symptomatic lumbar spondylolysis treated in the General Hospital of Armed Police Force (Beijing, China) were identified as the spondylolysis group. All the 52 patients were divided into two subgroups, Subgroup A: 36 patients with simple lumbar spondylolysis, and Subgroup B: 16 patients with lumbar spondylolysis accompanying with mild lumbar spondylolisthesis (slip percentage <30%). Altogether 207 healthy adults were chosen as the control group. All patients and the control group took lumbosacral lateral radiographs. Seven sagittal lumbosacral parameters, including PI, pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), L5 incidence, L5 slope, and sacral table angle (STA), were measured in the lateral radiographs. All the parameters aforementioned were compared between the two subgroups and between the spondylolysis group and the control group with independent-sample t- test.

RESULTS

There were no statistically significant differences of all seven sagittal lumbosacral parameters between Subgroup A and Subgroup B. PI, PT, SS, and LL were higher (P < 0.05) in the spondylolysis group than those in the control group, but STA was lower (P < 0.001) in the spondylolysis group.

CONCLUSIONS

Current study results suggest that increased PI and decreased STA may play important roles in the pathology of lumbar spondylolysis in Han Chinese population.

Guideline summary review: an evidence-based clinical guideline for the diagnosis and treatment of adult isthmic spondylolisthesis

BACKGROUND CONTEXT

The North American Spine Society's (NASS) Evidence-Based Clinical Guideline for the Diagnosis and Treatment of Adult Isthmic Spondylolisthesis features evidence-based recommendations for diagnosing and treating adult patients with isthmic spondylolisthesis. The guideline is intended to reflect contemporary treatment concepts for symptomatic isthmic spondylolisthesis as reflected in the highest quality clinical literature available on this subject as of June 2013. NASS' guideline on this topic is the only guideline on adult isthmic spondylolisthesis accepted in the Agency for Healthcare Research and Quality's National Guideline Clearinghouse.

PURPOSE

The purpose of the guideline is to provide an evidence-based educational tool to assist spine specialists when making clinical decisions for adult patients with isthmic spondylolisthesis. This article provides a brief summary of the evidence-based guideline recommendations for diagnosing and treating patients with this condition.

STUDY DESIGN

This is a guideline summary review.

METHODS

This guideline is the product of the Adult Isthmic Spondylolisthesis Work Group of NASS' Evidence-Based Clinical Guideline Development Committee. The methods used to develop this guideline are detailed in the complete guideline and technical report available on the NASS website. In brief, a multidisciplinary work group of spine care specialists convened to identify clinical questionsto address in the guideline. The literature search strategy was developed in consultation with medical librarians. Upon completion of the systematic literature search, evidence relevant to the clinical questions posed in the guideline was reviewed. Work group members utilized NASS evidentiary table templates to summarize study conclusions, identify study strengths and weaknesses, and assign levels of evidence. Work group members participated in webcasts and in-person recommendation meetings to update and formulate evidence-based recommendations and incorporate expert opinion when necessary. The draft guidelines were submitted to an internal peer review process and ultimately approved by the NASS Board of Directors. Upon publication, the Adult Isthmic Spondylolisthesis guideline was accepted into the National Guideline Clearinghouse and will be updated approximately every 5 years.

RESULTS

Thirty-one clinical questions were addressed, and the answers are summarized in this article. The respective recommendations were graded according to the levels of evidence of the supporting literature.

CONCLUSIONS

The evidence-based clinical guideline has been created using techniques of evidence-based medicine and best available evidence to aid practitioners in the diagnosis and treatment of adult patients with isthmic spondylolisthesis. The entire guideline document, including the evidentiary tables, literature search parameters, literature attrition flowchart, suggestions for future research, and all of the references, is available electronically on the NASS website at https://www.spine.org/ResearchClinicalCare/QualityImprovement/ClinicalGuidelines.aspx and will remain updated on a timely schedule.

Sacral orientation and Scheuermann's kyphosis

To examine whether the association between spinal alignment and sacral anatomical orientation (SAO) can be detected in skeletal populations, by comparing SAO values in individuals with a typical SD to individuals with normal spinal alignment. 2025 skeletons were screened for Scheuermann's disease. Scheuermann's kyphosis was established by the presence of apophyseal abnormalities associated with more than 5° of anterior wedging in each of three adjacent vertebrae. SAO was measured as the angle created between the intersection of a line running parallel to the superior surface of the sacrum and a line running between the anterior superior iliac spine and the anterior-superior edge of the symphysis pubis (PUBIS). SAO was measured on 185 individuals with normal spines and 183 individuals with Scheuermann's kyphosis. Out of 2025 skeletons, 183 (9 %) were diagnosed with Scheuermann's kyphosis. The sacrum was significantly more horizontally oriented in individuals with Scheuermann's kyphosis compared with the control (SAO: 44.44 ± 9.7° vs. 50 ± 9.9°, p < 0.001). Alteration in spinal biomechanics due to a horizontally orientated sacrum may be an important contributing factor for the development of Scheuermann's kyphosis.

The Association of Sacral Table Angle Measurements With Spondylolytic and Spondylolisthetic Defects at the Lumbosacral Articulation: A Radiographic Analysis

STUDY DESIGN

Retrospective radiographic study of 6 patients with L5 spondylolysis observed prospectively before the onset of lysis through adulthood. A radiographic analysis of 50 pediatric control subjects was compared with the study group.

OBJECTIVE

To determine whether sacral table angle (STA) measurements bear etiologic association with the development of spondylolysis and/or subsequent spondylolisthesis.

SUMMARY OF BACKGROUND DATA

Although radiographic parameters in association with spondylolysis and isthmic spondylolisthesis have been studied, no parameter has been shown to definitively have a role in development of this disease process. The STA is a recently described radiographic parameter useful in measuring anatomic changes across the lumbosacral articulation. This measurement's role as a predictor of pars lysis and subsequent slippage remains unknown.

METHODS

The researchers examined the longitudinal plain radiographs of 6 patients observed from childhood, before the development of spondylolysis, through adulthood. Measurements of STA and percent slippage were performed. Fifty pediatric control subjects' radiographs were also examined with STA measurements. Statistical analysis was conducted on results.

RESULTS

Mean STA of the study group before the development of spondylolysis was 95° ± 5.5°. Mean STA from the control group was 97.5° ± 4.3°. No statistical difference was found between groups (p > .05). No index patient had an abnormal STA before spondylolysis (less than 89°, defined as being outside 2 standard deviations from the control mean). Four of 6 index patients with spondylolysis developed spondylolisthesis. A negative correlation (r = .54) was seen for STA as a function of increasing percent slip when assessed longitudinally.

CONCLUSIONS

Abnormal STA measurement was not seen before the development of spondylolysis in this study population. Decreasing STAs were seen secondarily in patients with L5 spondylolisthetic progression. This finding points to anatomic change and secondary remodeling of the upper sacrum as a result of slippage.

The Comparison of Sagittal Spinopelvic Parameters between Young Adult Patients with L5 Spondylolysis and Age-Matched Control Group

Objective

To compare spinopelvic parameters in young adult patients with spondylolysis to those in age-matched patients without spondylolysis and investigate the clinical impact of sagittal spinopelvic parameters in patients with L5 spondylolysis.

Methods

From 2009 to 2012, a total of 198 young adult male patients with spondylolysis were identified. Eighty age-matched patients without spondylolysis were also selected. Standing lateral films that included both hip joints were obtained for each subject. Pelvic incidence (PI), sacral slope (SS), pelvic tilt, lumbar lordosis angle, sacral inclination, lumbosacral angle, and sacral table angle were measured in both groups. A comparative study of the spinopelvic parameters of these two groups was performed using SPSS 15.0 (SPSS Inc., Chicago, IL, USA).

Results

Among the aforementioned spinopelvic parameters, PI, SS and STA were significantly different between patients with spondylolysis and those without spondylolysis. PI and SS were higher in the spondylolysis group than in the control group, but STA was lower in the spondylolysis group than in the control group.

Conclusion

PI and SS were higher in the spondylolysis group than in the control group, but STA was lower in the spondylolysis group than in the control group. Patients with spondylolysis have low STA at birth, which remains constant during growth; a low STA translates into high SS. As a result, PI is also increased in accordance with SS. Therefore, we suggest that STA is an important etiologic factor in young adult patients with L5 spondylolysis.

The relevance of sacral and sacro-pelvic morphology in developmental lumbosacral spondylolisthesis: are they equally important?

STUDY DESIGN

Retrospective study of the importance of sacral and sacro-pelvic morphology in developmental L5-S1 spondylolisthesis.

OBJECTIVES

To determine and compare the importance of sacral and sacro-pelvic morphology in developmental L5-S1 spondylolisthesis. Recent studies have shown abnormalities in sacral and sacro-pelvic morphology in spondylolisthesis. However, it is still unclear if sacral and sacro-pelvic morphology are correlated and if they are equally important in the progression of spondylolisthesis.

METHODS

Lateral radiographs of 120 controls and 131 subjects with developmental L5-S1 spondylolisthesis were analyzed. Sacral table angle (STA) and pelvic incidence (PI) were compared using Student t tests. The relationship between STA and PI was assessed separately in the control and spondylolisthesis groups using Pearson's coefficients. The proportion of subjects with high PI but average STA was compared to the proportion of subjects with low STA but average PI using χ (2) tests.

RESULTS

STA was significantly lower and PI was significantly higher in the spondylolisthesis group. STA was statistically related to PI in both control (r = -0.43) and spondylolisthesis (r = -0.57) groups. In the spondylolisthesis group, STA (r = -0.45) and PI (r = 0.35) were significantly related to slip percentage. STA remained statistically related to slip when controlling for PI. A significantly greater proportion of subjects in the spondylolisthesis group had average STA and high PI, rather than average PI and low STA.

CONCLUSION

The significant relationship between PI and STA validates that geometrically sacral morphology depends on sacro-pelvic morphology. This study failed to demonstrate a clear predominant role of either STA or PI in the presence of spondylolisthesis.

L5 pedicle length is increased in subjects with spondylolysis: an anatomic study of 1072 cadavers

BACKGROUND

In spondylolisthesis, it is believed that as L5 slips on S1, the pedicle may become elongated in response to the instability in an attempt to bridge the defect. Whether patients with spondylolysis, which is largely developmental, also develop elongation of the pedicles is unknown.

QUESTIONS/PURPOSES

The purpose of this study is to evaluate and quantify the increase in L5 pedicle length in subjects with spondylolysis as compared with normal healthy subjects.

METHODS

Nine hundred fifty-two human cadaveric specimens without spondylolysis and 120 specimens with spondylolysis from the Hamann-Todd Osteological Collection were examined by a single examiner. Baseline data, including age, sex, and race of specimens, were collected. Digital calipers were used to measure the pedicle lengths at the L5 level. Linear regression analysis was performed to compare the L5 pedicle lengths in healthy patients and patients with spondylolysis.

RESULTS

Linear regression showed a significant association of increased L5 pedicle length in subjects with spondylolysis. The average L5 pedicle length in subjects with spondylolysis was greater compared with subjects without spondylolysis. In spondylolytic specimens, pedicles start to elongate after the age of 40 years. The pedicle lengths increase progressively from 5.6 mm at 40 years to 6.7 mm at 80 years with a 1% to 3% increment every decade. The pedicle lengths showed little variation in specimens from healthy subjects.

CONCLUSIONS

In spondylolytic specimens, there is progressive elongation of L5 pedicle length after the third decade. An increase in L5 pedicle length in all age groups compared with the specimens from healthy subjects suggests that pathologic changes occur in bony anatomy of L5 vertebrae as early as adolescence when the condition develops.

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.

Radiographic analysis of spondylolisthesis and sagittal spinopelvic deformity

Traditional radiographic analysis of spondylolisthesis focuses on the regional sagittal deformity at the lumbosacral junction. Pelvic morphology has also been cited as an important factor that contributes to the development of high-grade spondylolisthesis. However, the importance of global sagittal balance of the spine and pelvis in patients with spondylolisthesis has been emphasized recently. Patients with this condition can develop abnormal sagittal spinopelvic balance; restoration of sagittal spinal alignment can improve their health-related quality of life. Reduction has been used to restore alignment, but its role in the management of high-grade spondylolisthesis is controversial. None of the current classification systems take sagittal sacropelvic and spinopelvic balance into account. Improved understanding of the relationship between the spine and pelvis has led to the development of a new classification system that incorporates analysis of spinopelvic balance in the radiographic assessment. This new system may aid surgeons in identifying patients who would benefit from a partial reduction procedure.

Spondylolysis and spondylolisthesis: a narrative review of etiology, diagnosis, and conservative management

OBJECTIVE

To review current literature regarding the etiology, diagnosis, and conservative treatment of spondylolysis and spondylolytic spondylolisthesis.

METHODS

The PubMed database was searched for articles on spondylolysis and/or spondylolisthesis and their incidence, diagnosis, imaging, treatment, and prognosis. The bibliographies of articles determined to be relevant were also reviewed.

RESULTS

A PubMed search of spondylolysis or spondylolis-thesis yielded over 800 citations. Sixty-eight articles were selected based on an opinion of perceived relevance to the subjects of spondylolysis and spondylolisthesis.

CONCLUSIONS

Spondylolysis affects approximately 6% of the population. The lesion likely represents a stress fracture and the typical age of onset is early childhood and adolescence. Most individuals are asymptomatic. Adolescents with low back pain may have an impending or new pars defect. A high index of suspicion for a new pars defect should prompt utilization of physiologic imaging to determine the likelihood of pars union in young patients. Restrictive bracing may lead to healing of the fracture and cessation of pain. Spondylolisthesis is a common complication of spondylolysis. Spondylolisthesis progression is typically small and most likely in young individuals. Significant progression in adults is rare. The finding of spondylolysis and spondylolisthesis in an adult patient is usually incidental and not likely to be a direct source of pain unless there is concurrent instability.

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.

Clinical application of a novel assessment for lumbosacral stability

OBJECT

To evaluate the grade of lumbosacral stability, shape analysis was conducted on plain radiographs of the lumbar spine.

METHODS

One hundred twenty-six patients were classified into 2 groups: those with a single-segment disc space narrowing at L5-S1 or at L4-5. Stability was evaluated using the discriminant function (z score) derived from the analysis of radiographic parameters-that is, relative thickness of transverse process of L-5 and the sacral table angle.

RESULTS

In patients with a space narrowing at L5-S1, the author observed a significantly slender L-5 transverse process and acute obliquity of the sacral endplate; accordingly, the z score was negative. In patients with a broad transverse process and a positive z score, the segment associated with disc height loss was L4-5. Thus, a close correlation was found between the site of the disc height loss and the bony characteristics of L-5 and S-1. Furthermore, it could be expected with a high degree reliability that when young adult patients had a z score less than -2 or -3, their L-5 vertebra would develop degenerative spondylolisthesis after middle age and the L5-S1 segment could be saved from age-related alterations as long as the z score was greater than 2.5. The constitutional characteristics of the lumbosacral junction may exert a major influence on the site of disc degeneration.

CONCLUSIONS

Stability at the lumbosacral junction was thought to be quantitatively represented by the z score, with z being designated the lumbosacral stability score.

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.

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.

Sacral orientation and spondylolysis

STUDY DESIGN

A descriptive study (based on skeletal material) was designed to measure sacral anatomic orientation (SAO) in individuals with and without spondylolysis.

OBJECTIVE

To test whether a relationship between SAO and spondylolysis exists.

SUMMARY OF BACKGROUND DATA

Spondylolysis is a stress fracture in the pars interarticularis (mainly of L5). The natural history of the phenomenon has been debated for years with opinions divided, i.e., is it a developmental condition or a stress fracture phenomenon. There is some evidence to suggest that sacral orientation can be a "key player" in revealing the etiology of spondylolysis.

METHODS

The pelvis was anatomically reconstructed and SAO was measured as the angle created between the intersection of a line running parallel to the superior surface of the sacrum and a line running between the anterior superior iliac spine (ASIS) and the anterior-superior edge of the symphysis pubis (PUBIS).SAO was measured in 99 adult males with spondylolysis and 125 adult males without spondylolysis. The difference between the groups was tested using an unpaired t test.

RESULTS

Spondylolysis prevalence is significantly higher in African-Americans compared to European-Americans: 5.4% versus 2.04% in males (P < 0.001) and 2.31% versus 0.4%, P < 0.001 in females. SAO was significantly lower in the spondylolytic group (44.07 degrees +/- 11.46 degrees) compared to the control group (51.07 degrees +/- 8.46 degrees, P < 0.001).

CONCLUSION

A more horizontally oriented sacrum leads to direct impingement on L5 pars interarticularis by both L4 inferior articular facet superiorly and S1 superior articular facet inferiorly. Repetitive stress due to standing (daily activities) or sitting increases the "pincer effect" on this area, and eventually may lead to incomplete synostosis of the neural arch.

Prevalence of sacral spina bifida occulta and its relationship to age, sex, race, and the sacral table angle: an anatomic, osteologic study of three thousand one hundred specimens

STUDY DESIGN

An anatomic, osteologic study of spina bifida occulta (SBO).

OBJECTIVE

To determine the prevalence and patterns of SBO in a large population and examine its relationship to age, sex, and race; then to evaluate SBOs relationship to the sacral table angle (STA) when compared with an age-matched control group.

SUMMARY OF BACKGROUND DATA

SBO has a reported prevalence of 1.2% to 50% and has been implicated in various pathologic problems. SBO is often associated with spondylolysis or spondylolithesis. The STA has been implicated as an etiologic or predictive factor in the presence of pars defects.

METHODS

Three thousand one hundred osteologic specimens were evaluated for the presence of SBO. SBO was graded on a scale from 0 to III. Information on the age, sex, race, and STA of each specimen was recorded and measured, respectively. Prevalence and patterns of SBO were enumerated. The STAs of an age-matched control group of 355 specimens were examined. The SBO group and control groups were compared in regards to STA, controlling for age, sex, and race.

RESULTS

Overall, 355 specimens displayed SBO, for an overall prevalence of 12.4%. Of the SBO specimens, 68.7% were white, 88.2% were men, 53% were grade I, 37% II, and 10% III. All 3 grades of SBO were more common in men than women (88.2% vs. 11.8%) and more prevalent in whites than blacks (68.7% vs. 31.3%) (P = 0.01). SBO decreased in prevalence with increasing age. The average STA in SBO specimens was 95.9 degrees . This differed from an age-matched control group, 92.1 degrees (P < 0.0001). Every 1 degrees increase in STA resulted in a 6% increased likelihood of SBO. In SBO specimens, the STA decreased with increasing age, contrary to age-matched controls.

CONCLUSION

SBO has an overall prevalence of 12.4% in a large, diverse population. SBO is more common in men and whites and decreases in prevalence with increasing age. The STA is greater in SBO when compared with controls and an increased STA predicts SBO. In SBO, the STA decreases with increasing age.

Cervical spondylolysis in a judo player: a case report and biomechanical analysis

STUDY DESIGN

A case report and a biomechanical study using a finite element method.

OBJECTIVES

To report a case with the cervical spondylolysis and to understand the biomechanics of the cervical spine with spondylolysis at C6. Cervical spondylolysis, although not a common spinal disorder, can occur in athletes. Presently, the exact pathology, natural history and biomechanics are not known. Thus, treatment strategies for this disorder in athletes are in controversy. To treat and/or advise patients with cervical spondylolysis, the cervical spine biomechanics regarding this disorder should be understood.

METHODS

A case of a 12-year-old male judo player is presented. The patient presented with occipital and upper neck pain. Plain radiographs, reconstructed CT scan and MRIs of this patient were reviewed. Biomechanically, stress distributions were analyzed in response to 73.6 N axial compression and 1.5-Nm moment in flexion, extension, lateral bending, and axial rotation using a FE model of the intact ligamentous C3 to C7 segment. Bilateral spondylolysis was created in the model at C6. The stress results from the bilateral defect model were compared to the intact model predictions.

RESULTS

Plain radiographs showed bilateral C6 spondylolysis, and grade I spondylolisthesis. MRI showed mild disc degeneration at C6/7. With conservative treatment, the symptoms disappeared. In the spondylolysis model, the maximum Von Mises Stresses at C6/7 increased in all cervical spine motions, as compared to the intact case. Specifically, in axial rotation, the stress increase was 3.7-fold as compared to the intact model. The range of motion at C6/7 increased in the spondylolysis model as well. Again, during axial rotation, the increase in motion was 2.3-fold when compared to the intact model.

CONCLUSIONS

Cervical spondylolysis can cause biomechanical alterations, especially in axial rotation, leading to increased disc stresses and range of motion. The increased stresses in the disc and the hypermobility would be a dangerous condition for athletes participating in contact sports such as judo. Thus, we recommended that judo players with cervical spondylolysis should change to non-contact sports, such as jogging.

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.

Degenerative lumbosacral spondylolisthesis: possible factors which predispose the fifth lumbar vertebra to slip

We have analysed a number of radiological measurements in an attempt to clarify the predisposing factors for degenerative spondylolisthesis of the lumbosacral junction. We identified 57 patients with a slip and a control group of 293 patients without any radiological abnormality apart from age-related changes. The relative thickness of the L5 transverse process, the sacral table angle and the height of the iliac crest were measured and evaluated. The difference in these measurements between men and women was analysed in the control group. We found that the transverse process of L5 was extremely slender, the sacral table more inclined, and the L5 vertebra was less deeply placed in the pelvis in patients with a slip compared with the control group. The differences in these three parameters were statistically significant. We believe that the L5 vertebra is predisposed to slip when these factors act together on a rigidly-stabilised sacrum. This occurs more commonly in women, probably as a result of constitutional differences in the development of the male and female spine.

Assessment of sacral doming in lumbosacral spondylolisthesis

STUDY DESIGN

Quantitative versus subjective evaluation of sacral doming in lumbosacral spondylolisthesis.

OBJECTIVES

To evaluate the relevance of the Spinal Deformity Study Group (SDSG) index in the assessment of sacral doming and to propose a quantitative criterion to differentiate between significant and nonsignificant doming.

SUMMARY OF BACKGROUND DATA

There is no consensus on the optimal technique to assess sacral doming, although it is an important feature in spondylolisthesis.

METHODS

Five spinal surgeons subjectively assessed the sacral endplate of 100 subjects (34 high-grade spondylolisthesis, 50 low-grade spondylolisthesis, 16 controls) from lateral radiographs. Subjects were classified by each surgeon as having significant or nonsignificant sacral doming. An independent observer quantitatively evaluated sacral doming for all subjects using the SDSG index. A criterion to differentiate significant from nonsignificant sacral doming was sought, based on the comparison between the subjective assessment of surgeons and the quantitative evaluation by the independent observer. Intrarater and interrater reliability of the SDSG index was evaluated using intraclass correlation coefficient (ICC).

RESULTS

Intrarater and interrater ICCs for the SDSG index were excellent at 0.91 and 0.88, respectively. Sacral doming evaluated with the SDSG index was 11.6% +/- 5.0% (range, 1.5%-18.9%), 16.4% +/- 6.3% (range, 3.7%-35.6%), and 27.9% +/- 10.9% (range, 5.7%-56.9%) for controls, low-grade, and high-grade cases, respectively. Overall intersurgeon agreement on the significance of sacral doming was substantial at 88% (kappa = 0.72). With a threshold value of 25% for the SDSG index, 93% of concordance was found between the quantitative evaluation using the SDSG index and the multisurgeons subjective assessment.

CONCLUSION

This study confirms the relevance of the SDSG index to assess sacral doming in lumbosacral spondylolisthesis. The authors propose a criterion of 25% to differentiate significant from nonsignificant sacral doming using the SDSG index. Such a criterion will allow more accurate assessment of sacral remodeling, especially for borderline cases, and facilitate comparisons between studies.

Computed tomography evaluation of spondylolysis and spondylolisthesis in asymptomatic patients

STUDY DESIGN

A retrospective radiographic study involving analysis of abdominal and pelvic computed tomography (CT) scans obtained on patients presenting with clinical conditions other than back pain.

OBJECTIVE

To determine the incidence of spondylolysis and spondylolisthesis in patients requiring inpatient or emergency department CT evaluation for unrelated abdominal and pelvic conditions.

SUMMARY OF BACKGROUND DATA

Spondylolysis and spondylolisthesis are part of a disease process that is thought to be resultant from biomechanical stresses related to bipedal locomotion. The incidence is estimated to be 3% to 10% in the general population. Many of these cases occur without associated symptoms. To our knowledge, there is a relative paucity of data on the use of CT to evaluate the prevalence of these 2 entities in patients seeking medical attention for unrelated conditions.

METHODS

Five hundred ten consecutive abdominal and pelvic multi-detector CT scans obtained on a single scanner (Philips MX8000; Eindhoven, The Netherlands) were reviewed. These patients presented with such complaints as abdominal pain and fever, or were imaged as part of their inpatient evaluation for conditions unrelated to lumbar spine pathology. A board certified radiologist and a radiology resident retrospectively evaluated CT scans for lumbar spondylolysis, spondylolisthesis, and associated degenerative changes. A neuroradiologist confirmed all positive cases.

RESULTS

Of the 510 cases examined, there were 29 cases of spondylolysis at L5, corresponding to a prevalence of 5.7%. Twenty-three of the cases demonstrated bilateral spondylolysis and 6 unilateral. Sixteen of the 23 cases of bilateral spondylolysis also had spondylolisthesis, 13 of which were grade I, and 3 of which were grade II. In patients 45 years old and younger who did not have spondylolysis or spondylolisthesis, we observed a 32.2% incidence of sclerosis involving the L5 lumbar pedicles.

CONCLUSIONS

This study demonstrates a 5.7% prevalence of spondylolysis and a 3.1% prevalence of spondylolisthesis in patients undergoing CT scans of the abdomen and pelvis for unrelated reasons, corresponding to the rate of spondylolysis and spondylolisthesis detected in prospective plain radiographic studies. We observed a 1.2% incidence of unilateral spondylolysis, and approximately 67% of these demonstrated contralateral sclerosis. It is suggested in the literature that sclerosis of the contralateral pedicle seen in cases of unilateral spondylolysis may be a compensatory response to mechanical stresses on an unstable lumbar vertebral body.

High-grade slippage of the lumbar spine in a rat model of spondylolisthesis: effects of cyclooxygenase-2 inhibitor on its deformity

STUDY DESIGN

Radiographic and histologic evaluation of spondylolisthesis in a rat model.

OBJECTIVES

To investigate the effects of etodolac, a cox-2 inhibitor, on the severity of spondylolisthesis in a 4-week-old rat model.

SUMMARY OF BACKGROUND DATA

Spondylolisthesis occurs associated with spondylolysis in some pediatric patients. In such patients, the percent of forward slippage varies individually ranging between 0% and 100%. The factors determining the severity of forward slippage have not been clarified as yet. In earlier studies, we found that growth plate stress fracture was the basic lesion and that slippage was a consequence of the stress fracture. Hence, we hypothesized that the capacity of bone healing might be an important determinant of the degree of forward slippage.

METHODS

A lumbar spine slippage model was prepared in 4-week-old rats with vertebral physis fracture. To disrupt the fracture healing, the cyclooxygenase-2 (cox-2) inhibitor etodolac was used, and its effects on slippage and deformity were evaluated radiologically and histologically.

RESULTS

In the etodolac group, forward slip significantly increased (P < 0.05) to the Meyerding Grade III while in the control rats it was Grade I or II. Bone remodeling of the vertebral body was suppressed by etodolac. Histologically, epiphyseal separation with slippage was observed in all the control and etodolac-treated rats. However, in the etodolac-treated group, the epiphyseal plate was greatly separated and did not present periosteal thickening at the physis fracture site.

CONCLUSION

Vertebral forward slippage occurred in young rats after epiphyseal separation. In the etodolac group, slippage increased as deterioration of the bone healing capacity increased. Poor bony healing is suggested as one of the determinants of high-grade spondylolisthesis in children and adolescents.

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.

Spondylolysis, spondylolisthesis, and lumbo-sacral morphology in a medieval English skeletal population

The prevalence of spondylolysis and spondylolisthesis was studied in an adult skeletal series from a rural English medieval archaeological site. Attempts were made to evaluate the association of three aspects of lumbo-sacral skeletal morphology (pelvic incidence (a measure of the anterior inclination of the sacral table), lumbar transverse process width, and the presence of lumbo-sacral spina bifida occulta) with spondylolysis and spondylolisthesis. Results indicated a high prevalence of spondylolysis compared with a modern reference population, but few cases of spondylolisthesis were identified. Analysis of prevalence with respect to age suggests that in the study population, pars interarticularis defects generally formed late in the growth period or early in adult life. The study group showed a high mean pelvic incidence compared with modern Western Europeans, indicating a more steeply inclined sacral table, which may have elevated the risk of developing pars interarticularis defects. However, no statistically valid association could be demonstrated between the presence/absence of spondylolysis and pelvic incidence in the study material. There was no evidence for a link between lumbar transverse process index or lumbo-sacral spina bifida occulta and spondylolysis/spondylolisthesis. It is concluded that the potential role of lumbo-sacral morphology, as well as of activity regimes, should be considered when interpreting spondylolysis in paleopathological studies. If the frequency of spondylolysis is to some extent an indicator of past activity regimes, it may reflect lifestyle in younger individuals rather than in mature adults. Further work investigating the link between spondylolysis and lumbo-sacral morphological variables in premodern populations would be of value.

Sagittal spinopelvic balance in normal children and adolescents

The sagittal spinopelvic balance is poorly documented in normal pediatric subjects. The purpose of this study is to characterize the sagittal spinopelvic balance in the pediatric population and to evaluate the correlations between spinopelvic parameters. Seven parameters were evaluated from the lateral standing radiographs of 341 normal subjects aged 3-18 years old: thoracic kyphosis (TK), thoracic tilt (TT), lumbar lordosis (LL), lumbar tilt (LT), sacral slope (SS), pelvic tilt (PT) and pelvic incidence (PI). The mean values for the pelvic parameters were 49.1+/-11.0, 7.7+/-8.0 and 41.4+/-8.2 degrees for PI, PT and SS, respectively. The mean values for the spinal parameters were 48.0+/-11.7, 44.0+/-10.9, -7.3+/-5.2 and -3.1+/-5.2 degrees for LL, TK, LT and TT, respectively. The spinopelvic parameters were different from those reported in normal adults, but the correlations between the parameters were similar. PI was significantly related to SS and PT. Significant correlations were found between the parameters of adjacent anatomical regions. Pelvic morphology (PI) regulates sagittal sacro-pelvic orientation (SS and PT). Sacral orientation (SS) is correlated with the shape (LL) and orientation (LT) of the lumbar spine. Adjacent anatomical regions of the spine and pelvis are interdependent, and their relationships result in a stable and compensated posture, presumably to minimize energy expenditure. Results from this study could be used as an aid for the planning of surgery in pediatric patients with spinal deformity in order to restore a relatively normal sagittal spinopelvic balance.

The importance of spino-pelvic balance in L5-s1 developmental spondylolisthesis: a review of pertinent radiologic measurements

STUDY DESIGN

A review article.

OBJECTIVES

The purpose of this article is to review pertinent radiologic measurements for the evaluation of spino-pelvic balance in developmental spondylolisthesis, based on the experience of the Spinal Deformity Study Group.

SUMMARY OF BACKGROUND DATA

Over the past decade, pelvic morphology has been shown to significantly influence spino-pelvic balance of the human trunk in normal and pathologic conditions. This finding has important implications for the evaluation and treatment of developmental spondylolisthesis and has fostered a renewed interest in the radiologic evaluation of spino-pelvic balance in this condition.

METHODS

The lateral standing radiographs of the spine and pelvis of subjects with developmental L5-S1 spondylolisthesis were analyzed with a dedicated software allowing the calculation of the following parameters: pelvic incidence, sacral slope, pelvic tilt, L5 incidence angle, lumbosacral angle, lumbar lordosis, thoracic kyphosis, and grade of spondylolisthesis. All measurements were done by the same individual and compared to those of an adult and child reference population.

RESULTS

The pelvic shape, best quantified by the pelvic incidence angle, determines the position of the sacral endplate. The spine reacts to this position by adapting through lumbar lordosis, the amount of lordosis increasing as the sacral slope increases in order to balance the trunk in the upright position. Pelvic incidence, sacral slope, pelvic tilt, and lumbar lordosis are found to be significantly greater in subjects with developmental spondylolisthesis, while thoracic kyphosis is significantly lower when compared to a reference population. Furthermore, the differences between the two populations increase in a direct linear fashion as the severity of the spondylolisthesis increases, suggesting that pelvic anatomy has a direct influence on the development of a spondylolisthesis. Studies also indicate that pelvic incidence is unaffected by surgical reduction and instrumentation. Pelvic tilt, sacral slope, and thoracic kyphosis are slightly affected, while grade, L5 incidence angle, lumbosacral angle, and shape of the lumbar spine are significantly improved after surgery. A postoperative improvement in L5 incidence angle and lumbosacral angle appears correlated with a better outcome while subjects with a poor outcome have a higher preoperative grade.

CONCLUSIONS

Spino-pelvic balance in the sagittal plane can be considered as an open linear chain linking the head to the pelvis where the shape and orientation of each successive anatomic segment are closely related and influence the adjacent segment. Pelvic morphology and spino-pelvic balance are abnormal in developmental spondylolisthesis. These abnormalities should be quantified on lateral standing radiographs of the spine and pelvis and have important implications for the evaluation and treatment of this pathologic condition.

Spondylolytic spondylolisthesis: a study of pelvic and lumbosacral parameters of possible etiologic effect in two genetically and geographically distinct groups with high occurrence

STUDY DESIGN

An anatomic and radiographic study of archeological skeletal remains from two genetically and geographically distinct groups with high occurrence rates of spondylolytic spondylolisthesis was done. Specimens were Aleut (27% known occurrence rate, n = 48) and Arikara Plains Indians (9% occurrence, n = 250+ of 1,062).

OBJECTIVE

To evaluate three radiographic parameters highly correlated with spondylolisthesis (pelvic incidence [PI], sacral table angle [STA], and lumbar index [LI]) in genetically homogeneous populations to determine which may be etiologic or most predictive for lysis.

SUMMARY OF BACKGROUND DATA

LI has been known to vary with the percentage of slip in lytic spondylolisthesis. Recent clinical studies have shown that PI is also significantly higher in high-grade slips, and a possible etiologic effect has been ascribed to this association. STA has also been shown to vary between normals, those with only lysis, and those with lysis and slip. The etiologic significance of STA is unknown.

METHODS

Radiographic and direct morphologic measurement of PI, LI, and STA was done on L5 and reassembled sacra and ilia. Statistical analysis of these three parameters among all groups was done.

RESULTS

1) There is a genetically determined difference in the upper sacral tilt (STA) that may be etiologic. 2) Genetically homogeneous groups with a lower STA in normal specimens have an increased occurrence rate of spondylolysis. 3) When there has been pars lysis, changes in the STA occur as well as deformity more caudal in the sacrum. 4) These changes are likely related to remodeling with epiphyseal growth related to changed axial stresses secondary to pars lysis. 5) PI is not a primary etiologic factor in the process.

CONCLUSIONS

The STA in the normal population for each genetic group varies and relates significantly to the occurrence rate and is thus probably etiologic. STA is more highly associated with the occurrence of pars defect than is PI. Upper sacral deformities appear due to the growth plate response to the changed pressure gradients across the epiphyseal plate rather than interosseous remodeling of the ilium and acetabular area. Thus, changes in PI would be secondary.