Lumbar spondylolysis: reactive marrow changes seen in adjacent pedicles on MR images

MR imaging differentiating features between lytic and degenerative lumbosacral spondylolisthesis

Spondylolisthesis is characterized by the displacement of one vertebral body in relation to the adjacent vertebra. It is commonly observed in the lower lumbar region and can be caused by a variety of factors, including spondylolysis (a fracture in the pars interarticularis) or degenerative disease. Magnetic resonance imaging (MRI) is becoming increasingly popular as the primary modality for evaluation of low back pain and is often used in the absence of radiographs or Computed Tomography. However, it can be challenging for radiologists to differentiate between the two types of spondylolisthesis based on MRI alone. The goal of this article is to identify key imaging features on MRI that can aid radiologists in differentiating between spondylolysis and degenerative spondylolisthesis on MRI. Five key concepts are discussed: the "step-off" sign, the "wide canal" sign, T2 cortical bone signal on MRI, epidural fat interposition, and fluid in the facet joints. The utility, limitations and potential pitfalls of these concepts are also discussed to provide a comprehensive understanding of their use in differentiating between the two types of spondylolisthesis on MRI.

L5 spondylolysis: Anatomical study comparing healed and unhealed lesions

The anatomy and pathogenesis of spondylolysis has been widely studied; however, the microanatomy of spondylolysis of the lumbar vertebra has not been well described. Therefore, we aim to better elucidate this anatomy. Twenty dry bone specimens of healed and unhealed spondylolysis of the L5 vertebra were collected from human skeletal remains. Twelve L5 vertebrae were examples of unhealed spondylolysis and eight specimens exhibited a healed (i.e., bony fusion of the lesion) spondylolysis lesion. The specimens underwent macro and microanatomical analysis followed by CT and microCT imaging. Finally, selected healed and unhealed lesions were submitted for histological analysis using Mason Trichrome staining. The pars interarticularis of two L5 vertebrae without signs of healed/unhealed spondylolysis were evaluated histologically as controls. Of the 12 unhealed L5 pars defects, three were unilateral on left side. Of the eight healed pars defects, all were unilateral and seven of these were on left sides. One unilateral pars defect also had spina bifida occulta. Both on imaging and histological analysis, healed pars defects were only so superficially and not at deeper levels. Histologically, unhealed edges were made up of dense cortical bone while healed edges were made up primarily of trabecular bone. Based on our anatomical findings, the so-called healed spondylolysis lesions, although externally fused, are not thoroughly fused internally. Moreover, the anterior and posterior edges of the unhealed spondylosysis lesions are irregular and show signs of long-term disarticulation. Taken together, these data suggest that such 'healed' lesions might not be as stable as the normal L5 pars interarticularis.

Stress Injuries of the Spine in Sports

Spine sports stress injuries account for a significant amount of time loss at play in athletes, particularly if left unrecognized and allowed to progress. Spondylolysis makes up most of these stress injuries. This article focuses on spondylolysis, bringing together discussion from the literature on its pathomechanics and the different imaging modalities used in its diagnosis. Radiologists should be aware of the limitations and more importantly the roles of different imaging modalities in guiding and dictating the management of spondylolysis. Other stress-related injuries in the spine are also discussed including but not limited to pedicle fracture and apophyseal ring injury.

Association of MRI-defined lumbar paraspinal muscle mass and slip percentage in degenerative and isthmic spondylolisthesis: A multicenter, retrospective, observational study

The objective of this study is to investigate the role of paraspinal muscles in the progression of different types of spondylolisthesis by examining the correlation between cross-sectional area (CSA) of lumbar paraspinal muscle and slip percentage (SP) in degenerative spondylolisthesis and isthmic spondylolisthesis.A multicenter retrospective analysis was carried out including 219 subjects diagnosed with lumbar spondylolisthesis. Using T2-weighted axial magnetic resonance imgaging, CSAs of the psoas major (PM), multifidus (MU), and erector spinae were measured and divided by L5 vertebral body (VB) CSA. SP was measured using sagittal T2-weighted images. Correlations between muscle CSA ratio and SP were calculated in each group. Regression analysis was performed to predict the influence of each muscle CSA/VB CSA ratio on SP.No significant correlation was found in the degenerative spondylolisthesis group between any of the muscle CSA ratios and SP. Both PM/VB ratio (r = -0.24, P = .021) and MU/VB ratio (r = -0.26, P = .012) were negatively correlated with SP in the isthmic spondylolisthesis group. MU had more influence on SP than PM in the isthmic spondylolisthesis group (regression coefficient MU/VB: -8.08, PM/VB: -4.34).Both PM and MU muscle CSA ratios were negatively correlated with SP in the isthmic group. MU had more influence on SP than PM. No muscles had any correlations with SP in the degenerative group. This discrepancy between the two groups suggests that exercise programs or interventions regarding the segmental stability of isthmic spondylolisthesis and degenerative spondylolisthesis should be distinguished in clinical practice.Clinical Research Information Service of Korea Centers for Disease control and Prevention, KCT0002588. Registered on 12 December 2017, https://cris.nih.go.kr/cris/search/search_result_st01.jsp?seq=10702.

Pedicle Stress Injury in Children and Adolescents With Low Back Pain

STUDY DESIGN

A cross-sectional, retrospective cohort study.

OBJECTIVE

To examine the prevalence of the pedicle stress injury, spondylolysis in children and adolescents with low back pain. And secondly, to test the hypothesis that these pathologies are associated with lumbar lordosis angle.

SUMMARY OF BACKGROUND DATA

The prevalence of the pedicle stress injury has not been investigated in children with low back pain. In recent studies, lumbar lordosis angle was associated with spondylolysis, on the other hand the pedicle stress injury was not investigated yet.

METHODS

In this retrospective study, 789 consecutive lumbar magnetic resonance imaging under 18 years of age were reviewed between January 2015 and July 2018. Seven hundred magnetic resonances imaging among them were included in the study (mean age: 14.87 ± 2.41 yrs; range: 4-17). Prevalence of spondylolysis, spondylolisthesis, pedicle stress injury, pedicle deformation, disc degeneration, and increased lordosis was investigated and compared in terms of sex. The relationship between increased lordosis and other pathologies was evaluated with risk ratio. Nominal variables were evaluated between the two groups using chi-square, Mann-Whitney U test.

RESULTS

Prevalence of pedicle stress injury (12.7%), spondylolysis (8.7%), spondylolisthesis (4.1%), pedicle deformation (3.1%), disc degeneration (24%), increase in lordosis (17.4%) was found. Spondylolysis and pedicle injury were more frequent in males (P = 0.025, P < 0.001, respectively). Increased lordosis was more frequent in females (P < 0.001). Pedicle stress injury was frequently observed between 13 to 17 years and often an isolated lesion (69.6%). Spondylolysis, spondylolisthesis, pedicle deformity were more frequent in increased lordosis (P < 0.001), whereas pedicle injury frequency was not found to be different (P = 0.997).

CONCLUSION

Pedicle stress injury is a common cause of back pain under 18 years of age, more common in males, and often an isolated lesion. No relationship was found between pedicle stress injury and increased lordosis, unlike other pathologies.

LEVEL OF EVIDENCE

3.

Two-Level Spontaneous Pedicle Fracture above a Degenerative Spondylolisthesis and Minimally Invasive Treatment

This is a case report and literature review. The objectives of the study are to describe minimally invasive treatment of pedicle fractures, to show contralateral pedicle changes with pedicle fracture treatment, and to review literature on incidence and mechanism of neural arch fractures. After conservative therapy, there are several options for the treatment of pedicle fractures including pediculoplasty, osteosynthesis, or fusion. As patients’ age increases, the incidence of pedicle fracture may rise and minimally invasive pedicle screw treatment represents a good motion-preserving option to stabilize without fusion. We report a patient with spontaneous pedicle fractures above a degenerative spondylolisthesis and evidence of contralateral pedicle changes at L2 and L3. After minimally invasive pedicle screw placement, postoperative imaging demonstrated trabeculation across both L2 and L3 fractures with a resolution of contralateral pedicle sclerotic changes and healing of incompletely fracture contralateral pedicle at L2. Pedicle fractures lead to contralateral pedicle sclerotic changes and potential fracture and may cause significant back pain. Stabilization and healing of the neural arch can be achieved with minimally invasive placement of pedicle screws without need for fusion.

Comparison of Treatment Outcomes in Nonspecific Low-Back Pain Patients With and Without Modic Changes Who Receive Chiropractic Treatment

OBJECTIVE

The aim of this study was to determine if there was a difference in outcomes in patients with nonspecific low back pain, both with and without Modic changes (MCs), who received chiropractic care.

METHODS

This prospective outcomes study included 112 patients with low back pain without disc herniation on magnetic resonance imaging. All patients were treated with spinal manipulative therapy. At baseline, the numerical rating scale (NRS) and Bournemouth Questionnaire (BQ) for disability were collected. The NRS, BQ, and Patient's Global Impression of Change (primary outcome) were collected at the follow-up time points of 1 week, 1 month, and 3 months to assess overall improvement. Magnetic resonance imaging scans were analyzed for the presence of MCs and, if present, classified as Modic I or II. The χ² test was used to compare the proportion of patients reporting clinically relevant "improvement" between patients with and without MCs and between Modic I and Modic II patients. The unpaired Student t test was used to compare NRS and BQ at baseline and change scores at all follow-up time points.

RESULTS

For the primary outcome measure, the proportion of patients reporting relevant "improvement" (Patient's Global Impression of Change), and for the secondary outcome measures (NRS and BQ change scores), there were no significant differences between Modic positive and Modic negative patients or between Modic I and Modic II patients.

CONCLUSION

Neither the presence nor absence of MCs nor the Modic change category were related to treatment outcomes for patients with low back pain without disc herniation who received chiropractic care.

ABCs of the degenerative spine

Degenerative changes in the spine have high medical and socioeconomic significance. Imaging of the degenerative spine is a frequent challenge in radiology. The pathogenesis of this degenerative process represents a biomechanically related continuum of alterations, which can be identified with different imaging modalities. The aim of this article is to review radiological findings involving the intervertebral discs, end plates, bone marrow changes, facet joints and the spinal canal in relation to the pathogenesis of degenerative changes in the spine. Findings are described in association with the clinical symptoms they may cause, with a brief review of the possible treatment options. The article provides an illustrated review on the topic for radiology residents.

TEACHING POINTS

• The adjacent vertebrae, intervertebral disc, ligaments and facet joints constitute a spinal unit. • Degenerative change is a response to insults, such as mechanical or metabolic injury. • Spine degeneration is a biomechanically related continuum of alterations evolving over time.

Signal intensity changes of the posterior elements of the lumbar spine in symptomatic adults

INTRODUCTION

Modic type 1 changes around the vertebral endplate of the lumbar spine are well known to indicate inflammation; however, the clinical significance of similar SCs of the posterior elements has not been elucidated.

METHODS

Six hundred ninety-eight MRIs of patients with complaints of low back/leg pain were retrospectively examined. Target SCs in this study were hypointensity on T1-WI and hyperintensity on T2-WI or short tau inversion recovery sequences showing the same signal patterns seen in Modic type 1 change of the lumbar posterior elements. We analyzed the (1) Prevalence, symptom, and age distribution of SCs, (2) Localization of SCs and their association with Modic type 1 changes, (3) Spinal level distribution of SCs, (4) Association between SCs and disc degeneration of the affected spinal level, and (5) Association between SCs and radiological changes (spondylolisthesis, scoliosis).

RESULTS

(1) Among 698 adult patients, 36 (16 men, 20 women) exhibited SCs (5.2%). No SCs were identified in patients age <40 years. (2) Of the 36 SCs, 9 (25%) were localized at a single spinal level, while 27 (75%) were found at neighboring spinal levels across the facet joint. Thirteen SCs (36.1%) had continuity with Modic type 1 changes around the vertebral endplate, while 23 (63.9%) were localized to the posterior elements. (3) SCs were frequently identified in the lower lumbar spine below the L4 level. (4) More than 80% of the SCs involved disc degeneration. (5) Spondylolisthesis was associated with 93% of SCs in double-level, and scoliosis was associated with SCs in unilateral side.

CONCLUSION

The prevalence of SCs in symptomatic adults was 5.2%. On the basis of observed disc degeneration, 75% of SCs were considered to indicate inflammation or bone marrow edema around the facet joint.

Imaging of Degenerative and Infectious Conditions of the Spine

: Imaging is important in the evaluation of patients with degenerative disease and infectious processes. There are numerous conditions that can manifest as low back pain (LBP) or neck pain in a patient, and in many cases, the cause may be multifactorial. Clinical history and physical examination are key components in the evaluation of such patients; however, physical examination has variable sensitivity and specificity. Although studies have demonstrated that uncomplicated acute LBP and/or radiculopathy are self-limited conditions that do not warrant any imaging, neuroimaging can provide clear anatomic delineation of potential causes of the patient's clinical presentation. Various professional organizations have recommendations for imaging of LBP, which generally agree that an imaging study is not indicated for patients with uncomplicated LBP or radiculopathy without a red flag (eg, neurological deficit such as major weakness or numbness in lower extremities, bowel or bladder dysfunction, saddle anesthesia, fever, history of cancer, intravenous drug use, immunosuppression, trauma, or worsening symptoms). Different imaging modalities have a complementary role in the diagnosis of pathologies affecting the spine. In this review, we discuss the standard nomenclature for lumbar disk pathology and the utility of various clinical imaging techniques in the evaluation of LBP/neck pain for potential neurosurgical management. The imaging appearance of spinal infections and potential mimics also is reviewed. Finally, we discuss advanced neuroradiological techniques that offer greater microstructural and functional information.

ABBREVIATIONS

ADC, apparent diffusion coefficientDTI, diffusion tensor imagingDWI, diffusion-weighted imagingDOM, diskitis-osteomyelitisLBP, low back painMRM, magnetic resonance myelographySNA, spinal neuroarthropathySPECT, single-positron emission computed tomographySTIR, short tau inversion recovery.

Prevalence and clinical features of sports-related lumbosacral stress injuries in the young

BACKGROUND

Stress injuries (stress fractures and stress reactions) of the lumbosacral region are one of the causes of sports-related lower back pain in young individuals. These injuries can be detected by bone marrow edema lesion on MRI. However, little is known about the prevalence and clinical features of early stage lumbosacral stress injuries. This study aimed to evaluate the epidemiology of lumbosacral stress injuries.

METHODS

A total of 312 patients (under 18 years of age) who complained of sports-related lower back pain that had lasted for ≥7 days underwent magnetic resonance imaging (MRI) scans. We reviewed patients' records retrospectively.

RESULTS

MRI showed that 33.0% of the patients had lumbar stress injuries and 1.6% had sacral stress injuries. Lumbar stress injuries were more common in males than in females and were found in 30% of 13- to 18-year-old patients. About 50% of the patients that participated in soccer or track and field were diagnosed with lumbar stress injuries. No clinical patterns in the frequencies of sacral stress injuries were detected due to the low number of patients that suffered this type of injury. Plain radiography is rarely able to detect the early stage lesions associated with lumbosacral stress injuries, but such lesions can be detected in the caudal-ventral region of the pars interarticularis on sagittal computed tomography scans. Thirty-three percent of young patients that complained of sports-related lower back pain for ≥7 days had lumbar stress injuries, while 1.6% of them had sacral stress injuries. Clinicians should be aware of the existence of these injuries. MRI is useful for diagnosing lumbosacral stress injuries.

Comparison of Outcomes in MRI Confirmed Lumbar Disc Herniation Patients With and Without Modic Changes Treated With High Velocity, Low Amplitude Spinal Manipulation

OBJECTIVE

The purpose of this study was to determine if there is a difference in outcomes between Modic positive and negative lumbar disc herniation (LDH) patients treated with spinal manipulative therapy (SMT).

METHODS

This prospective outcomes study includes 72 MRI confirmed symptomatic LDH patients treated with SMT. Numerical rating scale (NRS) pain and Oswestry disability data were collected at baseline. NRS, patient global impression of change to assess overall improvement, and Oswestry data were collected at 2 weeks, 1, 3, 6 months and 1 year. MRI scans were analyzed for Modic change present/absent and classified as Modic I or II when present. Chi-squared test compared the proportion of patients reporting relevant 'improvement' between patients with and without Modic changes and those with Modic I vs. II. NRS and Oswestry scores were compared at baseline and change scores at all follow-up time points using the unpaired Student t test.

RESULTS

76.5% of Modic positive patients reported 'improvement' compared to 53.3% of Modic negative patients (P = .09) at 2 weeks. Modic positive patients had larger decreases in leg pain (P = .02) and disability scores (P = .012) at 2 weeks. Modic positive patients had larger reductions in disability levels at 3 (P = .049) and 6 months (P = .001). A significant difference (P = .001) between patients with Modic I vs. Modic II was found at 1 year, where Modic II patients did significantly better.

CONCLUSION

Modic positive patients reported higher levels of clinically relevant improvement 2 weeks, 3 and 6 months compared to Modic negative patients. However, at 1 year Modic I patients were significantly less likely to report 'improvement', suggesting they may be prone to relapse.

Lumbar paraspinal muscle morphometry and its correlations with demographic and radiological factors in adult isthmic spondylolisthesis: a retrospective review of 120 surgically managed cases

OBJECTIVE The objective of this study was to assess the cross-sectional areas (CSAs) of lumbar paraspinal muscles in adults with isthmic spondylolisthesis (IS), to compare them with those in the normative population, and to evaluate their correlations with demographic factors and MRI changes in various spinal elements. METHODS The authors conducted a retrospective study of patients who had undergone posterior lumbar interbody fusion for IS, and 2 of the authors acting as independent observers calculated the CSAs of various lumbar paraspinal muscles (psoas, erector spinae [ES], multifidus [MF]) on preoperative axial T2-weighted MR images from the L-3 to L-5 vertebral levels and computed the CSAs as ratios with respect to the corresponding vertebral body areas. These values were then compared with those in an age- and sex-matched normative population and were analyzed with respect to age, sex, duration of symptoms, grade of listhesis, and various MRI changes at the level of the listhesis (pedicle signal change, disc degeneration, and facetal arthropathy). RESULTS Compared with values in normative controls, the mean CSA value for the ES muscle was significantly higher in the study cohort of 120 patients (p = 0.002), whereas that for the MF muscle was significantly lower (p = 0.009), and more so in the patients with PSC (p = 0.002). Magnetic resonance imaging signal change in the pedicle was seen in half of the patients, all of whom demonstrated a Type 2 change. Of the variables tested in a multivariate analysis, age independently predicted lower area values for all 3 muscles (p ≤ 0.001), whereas female sex predicted a lower mean psoas area value (p < 0.001). None of the other variables significantly predicted any of the muscle area values. A decrease in the mean MF muscle area value alone was associated with a significantly increased likelihood of a PSC (p = 0.039). CONCLUSIONS Compared with normative controls, patients with IS suffer selective atrophy of their MF muscle, whereas their ES muscle undergoes a compensatory hypertrophy. Advancing age has a detrimental effect on the areas of the lumbar PSMs, whereas female sex predisposes to a decreased psoas muscle area. Multifidus muscle atrophy correlates with PSC, indicating the role of this deep stabilizer in the biomechanical stability of spondylolisthetic spines. This may be of clinical significance in targeted physiotherapy programs during the conservative management of IS.

Unilateral Pedicle Fracture Accompanying Spondylolytic Spondylolisthesis

Unilateral pedicle stress fracture accompanying spondylolytic spondylolisthesis is rare even in the elderly. Most are associated with major trauma, previous spine surgery, or stress-related activity. Here, the authors describe an unique case of unilateral pedicle fracture associated with spondylolytic spondylolisthesis at the L5 level, which was successfully treated by posterior lumbar interbody fusion with screw fixation at the L5-S1 level. As far as the authors' knowledge, no such case has been previously reported in the literature. The pathophysiological mechanism of this uncommon entity is discussed and a review of relevant literature is included.

Adaptive remodeling at the pedicle due to pars fracture: a finite element analysis study

Object

Spondylolysis is a common condition among the general population and a major cause of back pain in young athletes. This condition can be difficult to detect with plain radiography and has been reported to lead to contralateral pars fracture or pedicle fracture in the terminal stages. Interestingly, some patients with late-stage spondylolysis are observed to have radiographic or CT evidence of a sclerotic pedicle on the side contralateral to the spondylolysis. Although computational studies have shown stress elevation in the contralateral pedicle after a pars fracture, it is not known if these changes would cause sclerotic changes in the contralateral pedicle. The objective of this study was to investigate the adaptive remodeling process at the pedicle due to a contralateral spondylolysis using finite element analysis.

Methods

A multiscale finite element model of a vertebra was obtained by combining a continuum model of the posterior elements with a voxel-based pedicle section. Extension loading conditions were applied with or without a fracture at the contralateral pars to analyze the stresses in the contralateral pedicle. A remodeling algorithm was used to simulate and assess density changes in the contralateral pedicle.

Results

The remodeling algorithm demonstrated an increase in bone formation around the perimeter of the contralateral pedicle with some localized loss of mass in the region of cancellous bone.

Conclusions

The authors' results indicated that a pars fracture results in sclerotic changes in the contralateral pedicle. Such a remodeling process could increase overall bone mass. However, focal bone loss in the region of the cancellous bone of the pedicle might predispose the pedicle to microfractures. This phenomenon explains, at least in part, the origin of pedicle stress fractures in the sclerotic contralateral pedicles of patients with unilateral spondylolysis.

Sclerotic lesions of the spine: MRI assessment

Sclerotic (T2 dark) lesions of the spine are infrequent and, as a result, these are often missed or misdiagnosed. Plain films may not be always available during magnetic resonance imaging (MRI) readout. Knowledge of such lesions and their imaging appearances on MRI evaluation is essential for a reader. Additionally, a systematic approach is important to accurately diagnose these lesions. In this article we discuss the various causes of spinal sclerotic lesions, describe their MRI characteristics with relevant case examples, and outline a systematic approach to their evaluation.

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.

Imaging of lumbar degenerative disk disease: history and current state

One of the most common indications for performing magnetic resonance (MR) imaging of the lumbar spine is the symptom complex thought to originate as a result of degenerative disk disease. MR imaging, which has emerged as perhaps the modality of choice for imaging degenerative disk disease, can readily demonstrate disk pathology, degenerative endplate changes, facet and ligamentous hypertrophic changes, and the sequelae of instability. Its role in terms of predicting natural history of low back pain, identifying causality, or offering prognostic information is unclear. As available modalities for imaging the spine have progressed from radiography, myelography, and computed tomography to MR imaging, there have also been advances in spine surgery for degenerative disk disease. These advances are described in a temporal context for historical purposes with a focus on MR imaging's history and current state.

Pedicle marrow signal hyperintensity on short tau inversion recovery- and t2-weighted images: prevalence and relationship to clinical symptoms

BACKGROUND AND PURPOSE

Lumbar pedicle marrow hyperintense signal on T2- and STIR-weighted images is not an uncommon finding. We hypothesize that these marrow signal intensity changes and their behavior within the pedicle are associated with clinical symptoms and that their improvement or resolution correlates with clinical improvement. We investigated the prevalence of these pedicle marrow changes, associated morphologic abnormalities, and the relationship to symptoms over time.

MATERIALS AND METHODS

Prevalence was evaluated prospectively in 246 patients and retrospectively in 400 patients. To analyze the relationship between changes in signal intensity over time and symptoms, a third group of 30 patients was followed clinically for assessment of pain and functional limitation and with MR studies for 18 months or until signal intensity changes resolved.

RESULTS

The prevalence of pedicle marrow hyperintensity on T2 and STIR-weighted sequences was 1.7%. Associated morphologic abnormalities were pars interarticularis and pedicle fractures and degenerative facets. In the longitudinal study, pedicle marrow signal hyperintensity on T2- and STIR-weighted images resolved in 17 patients and persisted in 5 patients. The extent, intensity, and resolution of signal intensity changes significantly related to the degree of functional limitation (P = .01).

CONCLUSIONS

Resolution of pedicle marrow hyperintensity on T2 and STIR-weighted images was associated with improved functional testing and a trend toward decreased pain.

Quantitative measures of modic changes in lumbar spine magnetic resonance imaging: intra- and inter-rater reliability

STUDY DESIGN

A measurement reliability study.

OBJECTIVE

To develop quantitative measures for Modic changes (MCs) on magnetic resonance (MR) images and evaluate measurement reliability.

SUMMARY OF BACKGROUND DATA

MCs have been studied for more than 20 years but the clinical significance remains controversial. Little effort has been made to improve the measurement of MCs.

METHODS

The study was approved by the responsible institutional review board. On the basis of Modic classification, a series of quantitative dimension and signal intensity measures were developed for assessing MCs. Midsagittal T1- and T2-weighted MR images from 83 lumbar spines were then qualitatively and quantitatively assessed by two observers independently. Kappa and intraclass correlation coefficient (ICC) were used to examine intra- and inter-rater reliability. Pearson correlation coefficient was used to assess the relationships between the quantitative measurements of MCs. Mean absolute deviation (MAD) and Bland-Altman plots also were used to evaluate measurement errors and limits of agreement for selected measures.

RESULTS

For Modic classification, intrarater agreement was excellent (κ = 0.88) and inter-rater agreement was substantial (κ = 0.79). Intrarater agreement also was excellent when obtaining dimension measurements (ICC = 0.82-0.96) from T1- or T2-weighted images and inter-rater agreement was slightly greater using T1-weighted images (ICC = 0.73-0.88) than T2-weighted images (ICC = 0.66-0.82). Signal intensity measurements on T2-weighted images were found to have almost perfect intra- and inter-rater reliability (ICC = 0.92-0.99). The correlation analysis demonstrated that the quantitative measures represent different constructs. The MAD and Bland-Altman Plots further confirmed the high reliability of the area ratio, MCs mean signal intensity and MCs total signal intensity measurements.

CONCLUSION

Three quantitative measures are suggested to assess the severity of MCs, which provide reliable, precise measurements for research on the etiology, pathogenesis, and clinical relevance of MCs.

Lumbar spondylolysis: a review

Spondylolysis is an osseous defect of the pars interarticularis, thought to be a developmental or acquired stress fracture secondary to chronic low-grade trauma. It is encountered most frequently in adolescents, most commonly involving the lower lumbar spine, with particularly high prevalence among athletes involved in certain sports or activities. Spondylolysis can be asymptomatic or can be a cause of spine instability, back pain, and radiculopathy. The biomechanics and pathophysiology of spondylolysis are complex and debated. Imaging is utilized to detect spondylolysis, distinguish acute and active lesions from chronic inactive non-union, help establish prognosis, guide treatment, and to assess bony healing. Radiography with satisfactory technical quality can often demonstrate a pars defect. Multislice CT with multiplanar reformats is the most accurate modality for detecting the bony defect and may also be used for assessment of osseous healing; however, as with radiographs, it is not sensitive for detection of the early edematous stress response without a fracture line and exposes the patient to ionizing radiation. Magnetic resonance (MR) imaging should be used as the primary investigation for adolescents with back pain and suspected stress reactions of the lumbar pars interarticularis. Several imaging pitfalls render MR imaging less sensitive than CT for directly visualizing the pars defects (regional degenerative changes and sclerosis). Nevertheless, the presence of bone marrow edema on fluid-sensitive images is an important early finding that may suggest stress response without a visible fracture line. Moreover, MR is the imaging modality of choice for identifying associated nerve root compression. Single-photon emission computed tomography (SPECT) use is limited by a high rate of false-positive and false-negative results and by considerable ionizing radiation exposure. In this article, we provide a review of the current concepts regarding spondylolysis, its epidemiology, pathogenesis, and general treatment guidelines, as well as a detailed review and discussion of the imaging principles for the diagnosis and follow-up of this condition.

Multiple lumbar pedicle fractures in osteopetrosis: a case report

STUDY DESIGN

Single case report.

OBJECTIVE

To report the observation of multiple lumbar pedicle fractures in a patient with osteopetrosis.

SUMMARY OF BACKGROUND DATA

Osteopetrosis is characterized by osteoclast dysfunction, impaired bone resorption, and poor bone remodeling. As a result, the bone is brittle but hard and is referred to as "marble bone disease." Although long bone fractures are relatively common, fractures of the spine are rare. Spondylolysis has been reported in the cervical and lumbar spine, and pedicle fractures have been reported in the cervical spine. We report the case of a patient with autosomal dominant osteopetrosis with multiple lumbar pedicle fractures. To the best of our knowledge, there have been no previous reports of multiple lumbar pedicle fractures in osteopetrosis.

METHODS

A 73-year-old woman, with a known history of osteopetrosis, presented with acute nonradiating low back pain following a bout of coughing. The lower limb neurology and bladder and bowel function were normal. The imaging findings, clinical course, and treatment are discussed.

RESULTS

Initial computed tomography scans of the patient revealed the presence of multiple pedicle fractures with spondylolysis. The patient was advised bed rest for the first 3 days, and when the acute pain subsided, she was permitted to ambulate with a lumbosacral corset. The patient was asymptomatic for 8 months, when she was readmitted with another episode of acute low back pain. The CT scan revealed fresh fracture of the L4 pedicle, which was not seen on the previous scan. The pain settled down again with conservative measures.

CONCLUSION

This case report discusses the rare occurrence of multiple lumbar pedicle fractures and pars interarticularis (spondylolysis) fractures in a patient with osteopetrosis.

Modic changes: a systematic review of the literature

Modic changes (MC) are a common phenomenon on magnetic resonance imaging (MRI) in spinal degenerative diseases and strongly linked with low back pain (LBP). Histology, radiology, potential mechanisms, natural history and clinical studies of MC has formed the foundation on which our understanding of spinal degenerative diseases is built. The objective of this study was to provide a review of recent important advances in the study of MC and their clinical significance. This review article summarizes these studies, by delineating the possible mechanisms, and raising doubts and new questions. The related aspects such as discography and differential diagnosis with spinal infection and tumor on MRI are also discussed. Although most of researchers believe that MC are common findings in patients with spinal degenerative diseases and have an association with discogenic LBP, different results between studies may be produced from the differences in study design, inclusion criteria, and sample size. How the present knowledge of MC affects the management of spinal degenerative diseases remains unclear. Further studies of MC will explore therapeutic possibilities for future treatments of spinal degenerative diseases.

Radiological findings and healing patterns of incomplete stress fractures of the pars interarticularis

OBJECTIVE

The objective was to retrospectively record the CT and MRI features and healing patterns of acute, incomplete stress fractures of the pars interarticularis.

METHOD

The CT scans of 156 adolescents referred with suspected pars interarticularis stress fractures were reviewed. Patients with incomplete (grade 2) pars fractures were included in the study. Fractures were assessed on CT according to vertebral level, location of cortical involvement and direction of fracture propagation. MRI was also performed in 72 of the 156 cases. MRI images of incomplete fractures were assessed for the presence of marrow oedema and cortical integrity. Fracture healing patterns were characterised on follow-up CT imaging.

RESULTS

Twenty-five incomplete fractures were identified in 23 patients on CT. All fractures involved the inferior or infero-medial cortex of the pars and propagated superiorly or superolaterally. Ninety-two percent of incomplete fractures demonstrated either complete or partial healing on follow-up imaging. Two (8%) cases progressed to complete fractures. Thirteen incomplete fractures in 11 patients confirmed on CT also had MRI, and 92% demonstrated oedema in the pars. Ten out of thirteen fractures (77%) showed a break in the infero-medial cortex with intact supero-lateral cortex, which correlated with the CT findings. MRI incorrectly graded one case as a complete (grade 3) fracture, and 2 cases as (grade 1) stress reaction. Six fractures had follow-up MRI, 67% showed partial or complete cortical healing, and the same number showed persistent marrow oedema.

CONCLUSIONS

Incomplete fracture of the pars interarticularis represents a stage of the evolution of a complete stress fracture. The direction of fracture propagation is consistent, and complete healing can be achieved in most cases with appropriate clinical management. CT best demonstrates fracture size and extent, and is the most appropriate modality for follow-up. MRI is limited in its ability to fully depict the cortical integrity of incomplete fractures of the pars, but the presence of marrow oedema on fat-saturated T2-weighted sequences is a useful means of detecting acute spondylolysis.

Disc space-targeted angled axial MR images of the lumbar spine: a potential source of diagnostic error

OBJECTIVE

To compare the sensitivities of contiguous axial (CA) images and disc space-targeted angled axial (DSTAA) images of the lumbar spine for: (1) the detection of spondylolysis defects, and (2) the identification of disc material which has migrated away from the parent disc.

MATERIALS AND METHODS

Prospective imaging of the lumbar spine was performed over a 22-month period in 103 patients. Imaging protocols included spin-echo T1- and fast spin-echo (FSE) T2-weighted images in the sagittal and axial planes. For each patient, axial images were obtained both contiguously throughout the lumbar spine and as angled images, targeted at the region of the disc space only. Two separate data sets were compiled: one that included contiguous axial images (CA data set) and another that included targeted angled images through the disc spaces only (DSTAA data set). Identical sagittal images were included with both sets. A single radiologist independently interpreted the two data sets for a given patient following an intervening time lapse. The radiologist was blinded to the initial interpretation. Results from the two independent interpretations were then compared.

RESULTS

Spondylolysis defects were identified at 15 different levels in 14 patients (14%) using the contiguous axial imaging protocol compared with 8 (7%) identified using the disc space targeted angled axial imaging protocol (P = 0.12). Migrated disc material was identified in 12 patients (12%) using the CA protocol compared with 3 patients (3%) identified with the DSTAA protocol (P = 0.016).

CONCLUSIONS

MR imaging of the lumbar spine using contiguous axial data obtained through both the level of the disc and vertebral body demonstrates migrated disc material and spondylolysis defects better than did disc space-targeted angled data.

Lumbar degenerative disk disease

The sequelae of disk degeneration are among the leading causes of functional incapacity in both sexes and are a common source of chronic disability in the working years. Disk degeneration involves structural disruption and cell-mediated changes in composition. Mechanical, traumatic, nutritional, and genetic factors all may play a role in the cascade of disk degeneration, albeit to variable degree in different individuals. The presence of degenerative change is by no means an indicator of symptoms, and there is a very high prevalence in asymptomatic individuals. The etiology of pain as the symptom of degenerative disease is complex and appears to be a combination of mechanical deformation and the presence of inflammatory mediators. The role of imaging is to provide accurate morphologic information and influence therapeutic decision making. A necessary component, which connects these two purposes, is accurate natural history data. Understanding the relationship of etiologic factors, the morphologic alterations, which can be characterized with imaging, and the mechanisms of pain production and their interactions in the production of symptoms will require more accurate and reproducible stratification of patient cohorts.

Modic changes, possible causes and relation to low back pain

In patients with low back pain (LBP) it is only possible to diagnose a small proportion, (approximately 20%), on a patho-anatomical basis. Therefore, the identification of relevant LBP subgroups, preferably on a patho-anatomical basis, is strongly needed. Signal changes on MRI in the vertebral body marrow adjacent to the end plates also known as Modic changes (MC) are common in patients with LBP (18-58%) and is strongly associated with LBP. In asymptomatic persons the prevalence is 12-13%. MC are divided into three different types. Type 1 consists of fibro vascular tissue, type 2 is yellow fat, and type 3 is sclerotic bone. The temporal evolution of MC is uncertain, but the time span is years. Subchondral bone marrow signal changes associated with pain can be observed in different specific infectious, degenerative and immunological diseases such as osseous infections, osteoarthritis, ankylosing spondylitis and spondylarthritis. In the vertebrae, MC is seen in relation to vertebral fractures, spondylodiscitis, disc herniation, severe disc degeneration, injections with chymopapain, and acute Schmorl's impressions. The aim of this paper is to propose two possible pathogenetic mechanisms causing Modic changes. These are: A mechanical cause: Degeneration of the disc causes loss of soft nuclear material, reduced disc height and hydrostatic pressure, which increases the shear forces on the endplates and micro fractures may occur. The observed MC could represent oedema secondary to the fracture and subsequent inflammation, or a result of an inflammatory process from a toxic stimulus from the nucleus pulposus that seeps through the fractures. A bacterial cause: Following a tear in the outer fibres of the annulus e.g. disc herniation, new capilarisation and inflammation develop around the extruded nuclear material. Through this tissue it is possible for anaerobic bacteria to enter the anaerobic disc and in this environment cause a slowly developing low virulent infection. The MC could be the visible signs of the inflammation and oedema surrounding this infection, because the anaerobic bacteria cannot thrive in the highly aerobic environment of the MC type 1.

PERSPECTIVES

One or both of the described mechanisms can - if proven - be of significant importance for this specific subgroup of patients with LBP. Hence, it would be possible to give a more precise and relevant diagnosis to 20-50% of patients with LBP and enable in the development of efficient treatments which might be antibiotics, special rehabilitation programmes, rest, stabilizing exercise, or surgical fixation, depending on the underlying cause for the MC.

Sagittal alignment of the spine and pelvis in the presence of L5-s1 isthmic lysis and low-grade spondylolisthesis

STUDY DESIGN

A radiographic study of 82 patients with L5-S1 spondylolysis or spondylolisthesis of less than 50% displacement of L5 on S1.

OBJECTIVE

To measure and describe the sagittal alignment of the spine and pelvis in patients with spondylolysis before the development of a large secondary deformity associated with progression of the spondylolisthesis.

SUMMARY OF BACKGROUND DATA

Several publications have addressed the alignment of the spine and pelvis as an important factor in the occurrence, symptomatology, progression, and treatment of spondylolysis and spondylolisthesis. To our knowledge, this is the first report to systematically document the native sagittal alignment of affected patients and compare them to a large control population.

MATERIALS AND METHODS

The sagittal alignment in this cohort of 82 patients was compared with a control population of 160 patients without symptoms of back pain or radiographic abnormalities of the spine and pelvis that was the subject of a previous study.

RESULTS

Patients with spondylolysis and low-grade spondylolisthesis demonstrate increased pelvic incidence, increased lumbar lordosis, but less segmental extension between L5 and S1 than in a normal population.

CONCLUSIONS

These data suggest that differences in the sagittal alignment of the spine and pelvis may influence the biomechanical environment that results in the development of spondylolysis and progressive spondylolisthesis.

Degenerative Erkrankungen der Wirbelsäule

GOAL

The aim of this article is to describe rare and often unrecognized causes of spinal pain syndromes.

METHOD

Intervertebral disc degeneration frequently appears in early adulthood and can have a symptomatic or asymptomatic course. This article discusses incidence, pathophysiology, imaging, and pain symptomatology involved in the origin of back pain.

RESULTS

Anulus tears are often found in asymptomatic individuals but could be implicated in lumbar pain symptomatology in correlation with the provocative discography. Transient disorders can lead to pseudarthrosis of the iliac bone and to degeneration or to a reactive hypermobility with intervertebral disc degeneration in the level above. Modic type 1 erosive osteochondrosis is characterized by bone marrow edema near the hyaline cartilage end plate, which mostly elicits severe pain and results in serious limitations in everyday activities. The most important differential diagnosis is spondylodiscitis. Schmorl's nodes can exhibit considerable surrounding bone marrow edema that can be mistaken for metastases. A combination of MRI and CT should be employed for the diagnostic work-up of fatigue fracture of the interarticular portion, which is often overlooked due to its location. Synovial cysts of the facet joints can lead to radicular symptoms. Insufficiency fracture of the sacrum is frequently mistaken for metastasis due to intense scintigraphic enhancement and its signal behavior in MRI. CT provides instructive information.

CONCLUSION

Differential diagnosis should include less common causes such as anulus tears, transient disorders, activated Schmorl's nodes, synovial cysts of the facet joints, fatigue fractures of the interarticular portion of the spine and the sacrum and distinguish from metastases in particular.

The value of fat saturation sequences and contrast medium administration in MRI of degenerative disease of the posterior/perispinal elements of the lumbosacral spine

Degenerative-inflammatory lumbar spinal pathology is one of the most common reasons why individuals seek medical care, and low back pain is the main symptom among those most commonly associated with this pathologic condition. Pain is commonly attributed to degenerative disc disease, particularly herniated discs, but many different spinal and perispinal structures may undergo degenerative-inflammatory phenomena and produce pain: discs, bone, facet joints, ligaments and muscles. In particular, in patients with non-radicular low back pain, this syndrome may arise from changes of the posterior elements/perispinal tissues of the lumbar spine (i.e., the "posterior vertebral compartment"). They include: facet joint pathology (e.g., osteoarthritis, joint effusion, synovitis and synovial cysts), spondylolysis, spinal/perispinal ligamentous degenerative-inflammatory changes and perispinal muscular changes. It is well known that magnetic resonance is the most sensitive imaging method for the evaluation of spinal degenerative pathology, even in the initial stages of the disease. T2-weighted sequences with fat saturation, and when indicated the use of contrast-enhanced T1-weighted images with fat saturation, permit the visualization of degenerative-inflammatory changes of the posterior elements of the lumbar spine that in most cases would have been overlooked with conventional non-fat suppressed imaging.

No correlation between patient outcome and abnormal lumbar MRI findings 21 years after posterior or posterolateral fusion for isthmic spondylolisthesis in children and adolescents

Between 1977 and 1987, posterior (n=29) or posterolateral (n=73) fusion was performed for mild to moderate (slip <50%) isthmic spondylolisthesis on 102 patients (46 females, 56 males). The patients' average age at the time of operation was 15.9 (range, 8.1-19.8) years. Clinical (physical examination and Oswestry disability index (ODI)) and radiological (MRI and plain radiographs) examinations were performed on these patients after an average follow-up time of 21.0 (range, 26.2-15.1) years. In the radiographs, the mean slip preoperatively was 27% (range, 5-50%) and at the last follow-up visit 26% (range, 5-78%). Inside the fusion, there were a total of 148 intervertebral discs, 121 (82%) of them had decreased signal intensity in T2-weighted MR images and 113 (76%) were narrowed. Above the fusion level, 27 (27%) discs were speckled and 27 (27%) were black; 21 (21%) intervertebral disc spaces were narrowed. Two levels above the fusion level the numbers were 8 (8%), 16 (16%) and 16 (16%), respectively. Six (6%) patients had a prolapse. Degenerative facet joint hypertrophy above fusion was seen at 80 (79%) of the levels studied. When compared to healthy subjects higher frequency of disc and facet joint degeneration was found. In MR images, none of the patients had lumbar spinal stenosis inside or above the fusion. Narrowing of one or both of the neural foramina at the level of the L5-S1 interververtebral disc was noted in 32 (31%) patients. Seventeen (17%) of the patients had, usually mild, muscular atrophy of the psoas and 33 (32%) of the paraspinal muscles. There was no difference in frequency of abnormal MRI findings between patients (n=93) with ODI 20 or less compared with patients (n=9) with ODI more than 20. In situ fusion due to isthmic spondylolsthesis at adolescence is associated with moderate degenerative changes in the lumbar spine during a 20-year follow-up. Changes were most commonly found at the level of the spondylolisthesis and above fusion level. Neural foramina stenosis seems to be associated with spondylolisthesis and its severity to severity of the slip. Muscle atrophy tended to be mild. However, there was no correlation between patient outcome (ODI) and abnormal lumbar MRI findings.

Imaging features of spinal osteoid osteoma with emphasis on MRI findings

A retrospective evaluation of the imaging of 13 patients with a diagnosis of osteoid osteoma (OO) of the spine was undertaken. Available imaging included radiographs (n=10), computed tomography (CT) (n=13), bone scintigraphy (n=5) and magnetic resonance imaging (MRI) (n=13). MRI features evaluated were pattern of neural arch and vertebral body oedema and the presence of an identifiable nidus. MRI features were correlated with other available imaging. There were seven males and six females with an age range of 8-59 years. On radiographs, scoliosis was present in ten and a sclerotic pedicle in nine patients. Focal increased uptake on bone scintigraphy consistent with OO was seen in all five patients where scintigraphy was available. On CT, a nidus was identified in all patients and reactive sclerosis was seen in 12. MRI demonstrated the nidus in eight patients and unilateral neural arch oedema with anterior extension to involve the ipsilateral posterolateral vertebral body in 11. When MRI is performed in the evaluation of back pain, the presence of unilateral neural arch oedema extending to involve the posterolateral vertebral body raises the possibility of spinal OO and should prompt CT to confirm the presence of a nidus.

Juvenile spondylolysis: a comparative analysis of CT, SPECT and MRI

OBJECTIVE

To evaluate whether MRI correlates with CT and SPECT imaging for the diagnosis of juvenile spondylolysis, and to determine whether MRI can be used as an exclusive image modality.

DESIGN AND PATIENTS

Juveniles and young adults with a history of extension low back pain were evaluated by MRI, CT and SPECT imaging. All images were reviewed blindly. Correlative analyses included CT vs MRI for morphological grading and SPECT vs MRI for functional grading. Finally, an overall grading system compared MRI vs CT and SPECT combined. Statistical analysis was performed using the kappa statistic.

RESULTS

Seventy-two patients (mean age 16 years) were recruited. Forty pars defects were identified in 22 patients (31%), of which 25 were chronic non-union, five acute complete defects and ten acute incomplete fractures. Kappa scores demonstrated a high level of agreement for all comparative analyses. MRI vs SPECT (kappa: 0.794), MRI vs CT (kappa: 0.829) and MRI vs CT/SPECT (kappa: 0.786). The main causes of discrepancy were between MRI and SPECT for the diagnosis of stress reaction in the absence of overt fracture, and distinguishing incomplete fractures from intact pars or complete defects.

CONCLUSIONS

MRI can be used as an effective and reliable first-line image modality for diagnosis of juvenile spondylolysis. However, localised CT is recommended as a supplementary examination in selected cases as a baseline for assessment of healing and for evaluation of indeterminate cases.

Symptomatic spondylolysis: diagnosis and treatment

PURPOSE OF REVIEW

Approximately 35% of adolescents experience back pain. In athletic adolescents, spondylolysis is the most common offending cause. With growing numbers of adolescents participating in sports with higher levels of intensity, spondylolysis is becoming an increasingly common clinical problem.

RECENT FINDINGS

A recent report demonstrated the benign natural history of asymptomatic spondylolysis. However, long-term follow-up studies of patients who experience painful spondylolysis as adolescents remain unavailable. Modern imaging modalities have led to earlier diagnosis with greater accuracy. Conservative management with bracing continues to be a mainstay of treatment. In patients who are not helped by conservative therapy, recent studies have demonstrated the satisfactory long-term results of surgical repair.

SUMMARY

The long-term sequelae of symptomatic spondylolysis and unhealed pars defects require investigation. MRI promises to be a valuable tool for diagnosis and clinical stratification, but further studies are necessary to demonstrate its clinical utility.

Bilateral pedicle stress fractures in a female athlete: case report and review of the literature

STUDY DESIGN

Clinical case report of bilateral stress fractures of the pedicle in a female athlete presenting with back pain.

OBJECTIVES

To report this unusual case and surgical treatment and to review the relevant literature.

SUMMARY OF BACKGROUND DATA

Low back pain is a frequent complaint in athletes, with the majority of cases being related to muscular or soft tissue etiology. Spondylolysis, or pars fracture, is the most common injury of the neural arch. Stress fracture of the pedicle is a much less common occurrence. Bilateral pedicle fractures in an otherwise healthy athlete has not been previously reported in the orthopedic literature.

METHODS

A 19-year-old female athlete presented with low back pain limiting sports and daily activities. Radiographic workup revealed bilateral stress fractures of the pedicles of the L5 vertebra. Circumferential fusion of the L5-S1 segment was performed after failure of conservative treatment. Anterior interbody structural allograft and a vertical mesh cage were combined with instrumented posterolateral fusion using segmental pedicle screws and autogenous iliac crest bone graft.

RESULTS

The patient achieved complete pain relief, solid fusion, and return to normal function.

CONCLUSIONS

In this uncommon case of bilateral stress fractures of the pedicle, circumferential fusion assures full immobilization of the injured motion segment and assures a high probability of successful healing.

The biomechanical effects of spondylolysis and its treatment

STUDY DESIGN

Biomechanical analysis of the level above pars defects was performed using calf lumbar spines.

OBJECTIVES

To evaluate whether complete spondylolysis contributes to the pathology of the upper adjacent motion segment to the pars defect.

SUMMARY OF BACKGROUND DATA

It is well recognized that patients with spondylolysis show a higher incidence of spondylolisthesis or degenerative disc changes at the level of the pars defects. However, some authors have referred to the fact that disc damage may occur at the level above the defect and give rise to symptoms. However, no previous studies have been directed to the kinematic influence on the upper adjacent segment to pars defects.

METHODS

Nine fresh-frozen calf lumbar spines were used for this study. The bony defects were created on the L4 pars articularis bilaterally. Three linear extensometers and one specially designed angular extensometer were mounted across the L3-L4 and L4-L5 motion units. Nondestructive static loads, including axial compression, flexion-extension, and axial rotation, were applied on the specimens in four different conditions as follows: 1) intact spine; 2) bilateral pars defects on the L4 laminae; 3) pars defect repair with Buck technique; and 4) pedicle screw-rod fixation at L4-L5 after removal of the interarticular screws. Testing was performed on a material testing machine (MTS 858 Bionix test system, Minneapolis, MN), and load-displacement curves were recorded with the extensometers. Each test was performed for over five full sinusoidal loading cycles, and data from the fifth cycle were collected and analyzed.

RESULTS

After creating the pars interarticularis defects at L4, mobility at both the L3-L4 and L4-L5 motion units were increased in all loading conditions. The normalized range of motion (% ROM) as compared with the intact specimens showed that the pars defects increased the mobility at the upper adjacent level (L3-L4) to 106.4% in flexion-extension and to 120.1% in axial rotation; the differences were significant (P < 0.01). Consequently, the increased mobility was stabilized by applying Buck screws through the defects on both sides; however, the effect was not statistically significant. Furthermore, pedicle screw-rod fixation applied at the L4-L5 segment increased the intervertebral motion at the upper adjacent level, and % ROM in axial rotation was significantly increased to 119.2% of the intact spine (P < 0.05). Comparing the treatments' effects on the L3-L4 segment and that on L4-L5, the Buck screws restored the stability of both segments to the level of the intact spine, whereas the pedicle screw system limited the motion of L4-L5 motion and, on the contrary, increased the L3-L4 motion.

CONCLUSIONS

This biomechanical study exhibited that bilateral pars interarticularis defects increased the intervertebral mobility, not only at the involved level but also at the upper adjacent level to the lysis. The increased mobility at the upper segment was reduced by the Buck screw technique. However, this was increased again by the pedicle screw system applied on the involved segment. If clinically applicable, fixation of the pars defect alone appears to cause less adjacent level mechanical stress than pedicle screw-rod motion segment fixation.

Magnetic resonance imaging of sports injuries of the spine

Spinal injuries are relatively frequent events in professional athletes. Greater popularity of recreational athletic activities has increased the occurrence of sports-related spinal injuries in the general population. The demand of high-intensity sports places a constant load on the vertebral column. Several studies have demonstrated higher prevalence of spinal abnormalities in athletes than nonathletes. Direct correlation of the number and extent of injuries with the length in years of sports activity has been established. Diagnostic imaging, particularly magnetic resonance imaging (MRI), plays a crucial role in evaluating and detecting sports-related spinal injuries. Subtle bone marrow, soft-tissue, and spinal cord abnormalities, which may not be apparent on other imaging modalities, can be readily detected on MRI. Early detection often leads to prompt accurate diagnosis and expeditious management, in many cases avoiding unnecessary procedures. This article reviews the technical aspects of MRI for evaluation of the spine and the role of MRI in the assessment of sports-related spinal injuries.

Stress reactions of the lumbar pars interarticularis: the development of a new MRI classification system

STUDY DESIGN

In a retrospective study, multiple examiners reviewed lumbar magnetic resonance imaging scans to develop a new grading system for lumbar pars interarticularis stress reaction and spondylolysis. The resulting system can be used as a mechanism for classifying patients, and as a measurement tool for future studies assessing the outcome efficacy of lumbar magnetic resonance imaging in patients with abnormalities of the pars interarticularis.

OBJECTIVE

To determine the reliability of patient assignment to five different grades of bone stress reaction involving the lumbar pars interarticularis.

SUMMARY OF BACKGROUND DATA

Injury to the lumbar pars interarticularis (spondylolysis) is reported to be a common cause of low back pain in young patients. High-field-strength magnetic resonance imaging using fat saturation techniques and dedicated coil technology is sensitive in detecting bone stress injuries of the lumbar pars interarticularis, and thus is an excellent method for diagnosis. It also may be useful in prognostic decision making for these patients. A reliable classification system is a fundamental requirement for performing the research assessing the relationship between lumbar MRI findings and prognosis.

METHODS

For this study, 55 young athletic patients undergoing evaluation for low back pain with suspected stress injury to the lumbar pars interarticularis underwent standardized lumbar magnetic resonance imaging using a 1.5-T scanner. Magnetic resonance images were reviewed by three readers using a new magnetic resonance classification system developed for lumbar spondylolysis. The findings were assessed for both interobserver and intraobserver reliability for five possible combinations in a 5-grade classification system.

RESULTS

On magnetic resonance imaging, 42% of the patients demonstrated signal abnormalities of the lumbar pars interarticularis. The intraobserver and interobserver reliability coefficients for assigning the grade of pars interarticularis abnormality ranged, respectively, from 0.766 (95% confidence interval [CI], 0.62-0.91) to 0.906 (95% CI, 0.80-1), and from 0.706 (95% CI, 0.55-0.86) to 1.

CONCLUSIONS

Magnetic resonance findings of stress reactions and spondylolysis of the lumbar pars interarticularis can be reliably classified into five grades by experienced readers. Further study is needed to determine the role of these findings in the management of young athletic patients with low back pain.

Pedicle fracture after instrumented posterolateral lumbar fusion: a case report

STUDY DESIGN

The case report of a 60-year-old man with late onset back pain after lumbar spine fusion is presented.

OBJECTIVE

To report the rare complication of bilateral pedicle stress fractures after instrumented posterolateral lumbar fusion.

SUMMARY OF BACKGROUND DATA

A 56-year-old man underwent revision spinal surgery for ongoing back pain secondary to pseudoarthroses. A posterolateral L4-S1 instrumented fusion using pedicle screws was performed. Autologous bone graft was applied to the decorticated lateral masses. The internal fixation was removed 2 years later, at which time plain radiographs showed that the fusion mass was solid. At the age of 60 years, the man presented with worsening back pain. Plain radiographs and computed tomographic scans demonstrated bilateral L4 pedicle stress fractures. A bone scan indicated that these were recent in origin.

METHOD

The clinical assessment was undertaken by the senior author and surgeon. Investigations included plain radiography, computer tomography, and scintographic imaging. A systematic literature review of the relevant publications was performed.

RESULTS

In the reported patient, bilateral pedicle stress fractures developed 2 years after pedicle screw removal from an L4-S1 instrumented posterolateral lumbar spine fusion. This occurred at the uppermost level of the fusion mass.

CONCLUSIONS

The pedicle is the weakest point in the neural arch after posterolateral fusion. Although movement continues at the level of the disc space anteriorly, the pedicle is susceptible to fracture. Pedicle fracture is a rare late complication of posterolateral lumbar spine fusion.

Magnetic resonance imaging of injuries in the child athlete

Sports related injuries in children and adolescents are an increasingly frequent clinical problem. Soft tissue injury is relatively less common in children than in adults and radiographs suffice in most situations. However there are specific clinical circumstances where MR imaging is of value. We discuss and demonstrate a variety of acute and chronic sports related conditions where MR imaging has contributed to the diagnosis and management. Some conditions such as apophysitis, osteochondritis and chronic physeal injuries are unique to childhood while others including spondylysis and stress fractures are unusual conditions outside the context of sport in this age group.

Routine thin slice MRI effectively demonstrates the lumbar pars interarticularis

AIM

To confirm that routine thin slice sagittal magnetic resonance imaging (MRI) of the lumbar spine effectively demonstrates the lumbar pars interarticularis.

METHOD

A retrospective review of 100 MRI examinations was carried out and the appearance of the pars interarticularis at L4 and L5 bilaterally was assessed and classified as Type 1 - normal, Type 2 - sclerotic pars, Type 3 - not assessable and Type 4 - pars defect. A total of 400 pars were assessed. Those with known or obvious lytic spondylolysis were excluded from the study. All MRI examinations had both sagittal T1- and T2- weighted sequences and both were assessed. Sagittal T1 sequences were carried out with a 3 mm slice thickness and T2 image sequences with a 4 mm slice thickness.

RESULTS

The total number of pars assessed as normal (Type 1) was 299 (75%) of the T1-weighted images; 80 (20%) were classified Type 2. On T2-weighted imaging 290 (72.5%) were Type 1 and 66 (16.5%) were Type 2. Both of these types of appearances correlate well with the finding of a normal pars interarticularis. Thus, 379 (95%) of the pars appeared normal on T1-weighting and 356 (89%) on T2-weighting.

CONCLUSION

Contrary to previous findings with 5 mm thick slices, routine thin slice sagittal T1 and T2 images effectively demonstrate the pars interarticularis, with acceptable data acquisition times and image quality. We believe this is mainly due to the thinner slices obtained in our series.

Retrodural cysts bridging a bilateral lumbar spondylolysis: a report of two symptomatic cases

We report the MR features in two patients presenting with symptomatic thecal impingement by posterior epidural cysts linking a bilateral lumbar spondylolysis. Large fluid-filled channels bridging the ruptured partes interarticulares were present in spite of the absence of significant arthritic changes within the adjacent facet joints.

The radiological investigation of lumbar spondylolysis

Lumbar spondylolysis represents a stress fracture of the pars interarticularis and occurs most commonly at the L5 level. Pars defects can be imaged with plain radiography, bone scintigraphy, computed tomography (CT) and magnetic resonance imaging (MRI). Plain radiographic projections of particular value include the coned lateral view of the lumbosacral junction, which displays the majority of defects, and the anteroposterior view with 30 degrees cranial angulation. The value of oblique radiography is unproven. Planar bone scintigraphy (PBS) is more sensitive than radiography and single photon emission computed tomography (SPECT) more sensitive and specific than PBS. Both these techniques, however, are less specific than radiography and CT. CT, when performed with a reverse gantry angle and thin sections, is the investigation of choice for identifying radiographically occult lyses. Conventional lumbar spine MRI techniques are valuable for demonstrating normality of the pars, but may be associated with a high false positive rate for the diagnosis of pars defects.

Magnetic resonance imaging of the musculoskeletal system. Part 8. The spine, section 2

Magnetic resonance imaging has revolutionized the noninvasive evaluation of degenerative disc disease and its complications. Compared with computed tomography and computed tomographic myelography, magnetic resonance allows specific determination of the nature of disc protrusions and other degenerative related soft tissues about the spine. Magnetic resonance offers the most complete evaluation of specific degenerative disorders including degenerative facet disease, spondylolysis, spondylolisthesis, spontaneous lumbar epidural hematomas, and juvenile discogenic disease.