Are trunk muscle sizes different between acute lumbar spondylolysis and nonspecific low back pain?

INTRODUCTION: Morphological differences in the trunk muscles between adolescent athletes with lumbar spondylolysis (LS) and nonspecific low back pain (NSLBP) have not been fully elucidated. This study aimed to investigate the differences in physiological cross-sectional areas (CSA) of the trunk muscles between athletes with acute LS and those with acute NSLBP. METHODS: Magnetic resonance images of 48 patients aged 13-14 years diagnosed with acute LS or NSLBP were retrospectively evaluated. The CSA of the paraspinal, psoas major, and rectus abdominis muscles at the L4-5 intervertebral disc level were measured. RESULTS: CSA of the left and right paraspinal muscles in the acute LS group were significantly larger than those in the acute NSLBP group (left: mean difference, 276.0 mm2; 95% confidence interval [CI], 68.5-483.6 mm2; P = 0.01; right: mean difference, 228.8 mm2; 95% CI, 7.6-450.1 mm2; P = 0.04). The ratio between the left paraspinal muscles and left psoas major in the acute LS group was significantly larger than that in the acute NSLBP group (mean difference, 0.2; 95% CI, 0.0-0.4; P = 0.03). CONCLUSIONS: Trunk muscle size may differ between adolescent athletes with acute LS and those with NSLBP. Future research involving healthy controls is required to better understand the morphological characteristics of these injuries.

Comparison of maximum joint angles during pole vaulting between male pole vaulters with and without lumbar disc degeneration or lumbar spondylolysis.

BACKGROUND: Pole vaulting involves trunk flexion, extension, and rotation, which may place the lumbar spine under stress. Repeated pole vaulting may cause lumbar disc degeneration (DD) and lumbar spondylolysis (LS); however, this phenomenon is yet to be established. OBJECTIVE: This study aimed to determine the difference in the maximum joint angles of the shoulder, hip, and trunk during pole vaulting between male pole vaulters with and without lumbar DD or LS. METHODS: This retrospective study included 17 male pole vaulters. Four high-speed cameras were used to record the pole vaulters at 240 Hz. Radiography and magnetic resonance imaging were used to examine the lumbar spine in all athletes. Differences in the data between two sets of groups were analyzed using the unpaired t-test or the Mann-Whitney U test. RESULTS: There was a significant difference in the maximum joint angle of hip flexion between pole vaulters with and without lumbar DD (p= 0.03). CONCLUSION: Pole vaulters with lumbar DD may use lumbar flexion instead of hip flexion during the rock-back movement. Moreover, LS may occur due to repeated failed vaulting. Therefore, trunk stability and functional movements should be prioritized to prevent organic changes in the lower back.

The influence of spinal position on imaging findings: an observational study of thoracolumbar spine upright MRI in elite gymnasts.

PURPOSE: To investigate whether upright magnetic resonance imaging (MRI) has a role in defining thoracolumbar spine pathology in elite gymnastics. METHODS: A prospective cross-sectional observational study of National Senior and Junior Artistic gymnasts in three MRI positions (standard supine, upright flexed and extended positions). Two specialist musculoskeletal radiologists independently analysed images with neutral as a baseline with the effects of flexion and extension reported in line with Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement. RESULTS: Forty (18 males) gymnasts aged 13-24 years with a mean (SD) of 32 (5.3) training hours per week consented with 75% showing MRI abnormalities. Degenerative disc disease (DDD) was evident in 55% participants with vertebral end plate (VEP) changes in 42.5%. Spondylolysis was present in 40% with an additional 17% showing chronic bilateral complete L5 pars defects. 23% participants demonstrated different MRI findings in upright flexion compared to neutral. CONCLUSION: Findings suggest a high levels of MRI abnormalities in elite gymnastics including altered disc morphology and posterior element abnormalities. High prevalence of T11/12 DDD and VEP changes reflects the thoracolumbar junction being a transition zone. Upright MRI and varying spine position offer promise for enhanced visualisation of posterior element abnormalities.

Prevalence of lumbar spondylolysis and spondylolisthesis in patients with degenerative spinal disease.

Lumbar spondylolysis generally occurs in adolescent athletes. Bony union can be expected with conservative treatment, however, the fracture does not heal in some cases. When the fracture becomes a pseudoarthrosis, spondylolysis patients have the potential to develop isthmic spondylolisthesis. A cross-sectional study was performed to determine the incidence of spondylolysis and spondylolisthesis, and to elucidate when and how often spondylolisthesis occurs in patients with or without spondylolysis. Patients undergoing computed tomography (CT) scans of abdominal or lumbar regions for reasons other than low back pain were included (n = 580). Reconstruction CT images were obtained, and the prevalence of spondylolysis and spondylolisthesis were evaluated. Of the 580 patients, 37 patients (6.4%) had spondylolysis. Of these 37 patients, 19 patients (51.4%) showed spondylolisthesis, whereas only 7.4% of non-spondylolysis patients showed spondylolisthesis (p < 0.05). When excluding unilateral spondylolysis, 90% (18/20) of spondylolysis patients aged ≥60 years-old showed spondylolisthesis. None of the patients with isthmic spondylolisthesis had received fusion surgery, suggesting that most of these patients didn't have a severe disability requiring surgical treatment. Our results showed that the majority of bilateral spondylolysis patients aged ≥60 years-old show spondylolisthesis, and suggest that spondylolisthesis occurs very frequently and may develop at a younger age when spondylolysis exists.

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.

Phenotypic characterization of Slc26a2 mutant mice reveals a multifactorial etiology of spondylolysis.

Confusion persists over pathogenesis of spondylolysis. To confirm pathogenicity of the previously identified causative mutation of spondylolysis and investigate the genetic etiology, we generate a new mouse line harboring D673V mutation in the Slc26a2 gene. D673V mutation induces delayed endochondral ossification characterized by transiently reduced chondrocyte proliferation in mice at the early postnatal stage. Adult D673V homozygotes exhibit dysplastic isthmus and reduced bone volume of the dorsal vertebra resembling the detached vertebral bony structure when spondylolysis occurs, including the postzygopophysis, vertebral arch, and spinous process, which causes biomechanical alterations around the isthmic region of L4-5 vertebrae indicated by finite element analysis. Consistently, partial ablation of Slc26a2 in vertebral skeletal cells using Col1a1-Cre; Slc26a2 fl/fl mouse line recapitulates a similar but worsened vertebral phenotype featured by lamellar isthmus. In addition, when reaching late adulthood, D673V homozygotes develop an evident bone-loss phenotype and show impaired osteogenesis. These findings support a multifactorial etiology, involving congenitally predisposed isthmic conditions, altered biomechanics, and age-dependent bone loss, which leads to SLC26A2-related spondylolysis.

Biomechanical analysis of spino-pelvic postural configurations in spondylolysis subjected to various sport-related dynamic loading conditions.

PURPOSE: To study the risks of spondylolysis due to extrinsic loading conditions related to sports activities and intrinsic spino-pelvic postural parameters [pelvic incidence (PI) and sacral slope (SS)]. METHODS: A comprehensive osseo-disco-ligamentous L4-S1 finite element model was built for three cases with spondylolysis representing three different spino-pelvic angular configurations (SS = 32°, 47°, 59° and PI = 49°, 58°, 72°, respectively). After simulating the standing posture, 16 dynamic loading conditions were computationally tested for each configuration by combining four sport-related loads (compression, sagittal and lateral bending and axial torque). For each simulation, the Von Mises stress, L5-S1 facet contact force and resultant internal loads at the sacral endplate were computed. Significant effects were determined with an ANOVA. RESULTS: The maximal stress and volume of cancellous bone in the pars with stress higher than 75% of the ultimate stress were higher with 900 N simulated compression (2.2 MPa and 145 mm3) compared to only the body weight (1.36 MPa and 20.9 mm3) (p < 0.001). Combined compression with 10 Nm of flexion and an axial torque of 6 Nm generated the highest stress conditions (up to 2.7 MPa), and L5-S1 facet contact force (up to 430 N). The maximal stress was on average 17% higher for the case with the highest SS compared to the one with lowest SS for the 16 tested conditions (p = 0.0028). CONCLUSIONS: Combined flexion and axial rotation with compression generated the highest stress conditions related to risks of spondylolysis. The stress conditions intensify in patients with higher PI and SS. These slides can be retrieved under Electronic Supplementary Material.

The prevalence of lumbar spondylolysis in young children: a retrospective analysis using CT.

PURPOSE: Although lumbar spondylolysis is encountered in general population with an incidence estimated to be 3-10%, limited information is available for children. The aim of the study is to determine the prevalence of spondylolysis according to associated vertebral bony malformation and spinopelvic parameters in children under eight requiring CT evaluation for unrelated lumbar conditions. METHODS: Seven hundred and seventeen abdominal and pelvic multi-detector CT scans were obtained in patients under 8 years of age were reviewed. Two board certificated radiologists and two resident radiologists retrospectively evaluated CT scans for lumbar spondylolysis and associated malformations. Pelvic incidence and spondylolisthesis were reported. RESULTS: Our analysis included 717 CT scans in 532 children (259 girls and 273 boys). Twenty-five cases of spondylolysis were diagnosed (16 bilateral and 9 unilateral, 64 and 36%, respectively) in 14 boys (56%) and 11 girls (44%), associating with 12 grade I spondylolisthesis. The mean normal pelvic incidence was 45° (median 44°, SD 7°). The prevalence of spondylolysis was 1% in children under age 3 (n = 3 among 292 patients), 3.7% in children under age 6 (n = 17 among 454 patients) and 4.7% among the 532 patients. Unilateral spondylolysis was significantly associated with a spinal malformation (p = 0.04, Fisher's exact test), with normal pelvic incidence. Half of the patients with bilateral spondylolysis had high pelvic incidence. CONCLUSIONS: We observed a prevalence peak of unilateral spondylolysis in the context of a specific malformation in young infants under age 4 with normal pelvic incidence, and, then, a progressive increase in the prevalence of bilateral isolated spondylolysis.

Spondylolysis in the past: A case study of hunter-gatherers from Southern Patagonia.

Spondylolysis is a fracture of the pars interarticularis, the portion of the neural arch that lies between the superior articular facets and the inferior articular facets. Clinical evidence has suggested repetitive trauma to be the most probable cause, even though morphological weakness of the vertebra is probably also involved. Prevalence is between 3% and 8% in modern populations, while in archaeological samples it varies from 0% to 71.4%. Considering that very little data about this condition is available in past populations from the southern extreme of South America, the aim of this paper is to analyze the spondylolysis in a human skeletal sample from Southern Patagonia and, at the same time, to explore the prevalence of spondylolysis in archaeological contexts around the world to gain a better understanding of the results presented here. The Southern Patagonian skeletal series analyzed here showed a prevalence of 20%, with lower prevalence in the pre contact sample (11.1%) than in the contact period (23.1%). Skeletons from the Salesian Mission "Nuestra Señora de La Candelaria" showed a higher prevalence (25%) than the sample of skeletal remains recovered from outside the mission (20%), suggesting that changes in lifestyle of hunter-gatherers during contact could be implicated in the development of spondylolysis in this sample. A worldwide survey displays a wide range of prevalence figures in American and Asian samples and low diversity between African and European populations. Hunter-gatherers from Southern Patagonia showed similar values to those observed in other American samples.

[Analysis of Forensic Identification on 32 Cases of Lumbar Spondylolysis].

OBJECTIVES: To explore the casual relationship and the significance of identification among the injury, disease and damage consequence in the disability evaluation of lumbar spondylolysis by the standard for identifying grading of disability caused by work-related injuries. METHODS: The general data, injury manner, clinical treatment and the imaging examination of 32 lumbar spondylolysis cases were collected and retrospectively analyzed. According to the degree of participation in the injury and damage consequence, the identification and assessment of casual relationship was made, and the grading of disability was assessed. RESULTS: For 32 cases, injury had no effect on damage consequence in 7 cases, slight effect in 5 cases, secondary effect in 13 cases, equivalent effect in 4 cases, and complete effect in 3 cases. According to the related items in the standard for identifying grading of disability caused by work-related injuries, 3 cases were rated level 7, 5 cases were level 8, 6 cases were level 9, 11 cases were level 11 among the cases which existed causal relationship. CONCLUSIONS: The formation of lumbar spondylolysis is connected to the factors of age, anatomy, occupation and injury manner etc. The degree of disability should be accessed comprehensively after the analysis of the casual relationship among the injury, disease and damage consequence.

Vertebral body bone mineral density in patients with lumbar spondylolysis: a quantitative CT study.

PURPOSE: Spondylolysis is known to be a part of a disease process, which describes a defect in the pars interarticularis of vertebra. We aimed to use quantitative computed tomography (QCT) to measure vertebral body bone mineral density (BMD) in patients with lumbar spondylolysis and compare it with readings in controls. METHODS: Forty symptomatic patients with lumbar spondylolysis aged 18-52 years and 40 matched controls of same sex and approximate age (±2 years) were included in the study. Measurements of BMD were performed by QCT analysis for each vertebral body from T12 to L5 and mean BMD was calculated for each case. RESULTS: Of 40 patients, 22 (55%) demonstrated L5 spondylolysis, 14 (35%) L4 spondylolysis, three (7.5%) L3 spondylolysis, and one (2.5%) L2 spondylolysis. Spondylolisthesis was found in 29 patients (73%). Patients with spondylolisthesis were significantly older than patients without spondylolisthesis (42±6.9 vs. 37.2±5.4, P = 0.024). Mean BMD value of the patient group was significantly lower than that of the controls (105±24 mg/cm³ vs. 118.7±25.6 mg/cm³, P = 0.015). Subgroup analysis of 19 patients and 19 controls under the age of 40 revealed that the mean BMD value of the patients was significantly lower than that of the controls in the younger age group as well (108.7±23.5 mg/cm³ vs. 130±25.8 mg/cm³, P = 0.009). CONCLUSION: This study demonstrated that patients with spondylolysis had significantly lower mean vertebral body BMD compared with controls.

Sharp Force Trauma Death in a Young Individual From Medieval Gloucester.

The authors of the present work evaluate the trauma observed on the skeletal remains of an individual from medieval Gloucester and reconstruct the events that led to his death. The almost complete skeleton was recovered from the cemetery of St Owen and dates to the late medieval period. Several methods were used to determine the sex and age of the individual. The anthropological examination showed that the remains belonged to a young male, between the ages of 17 and 19 years. The young man also had antemortem pathologies that were related to his diet and lifestyle, as he appears to have had iron-deficiency anemia and Schmorl nodes. The trauma observed on the remains consisted of 3 cut marks located on the cranium, left radius, and right scapula. The cuts seem to have been inflicted by a heavy weapon, such as a sword. The trauma pattern observed is consistent with defensive action, and the fact that this skeleton was the only one in the collection that has evidence of trauma suggests that this was a case of interpersonal violence.

Spondylolysis and End Plate Arthrosis at L5-S1: A Cadaveric Study.

This study examined the effect of bilateral and unilateral L5 pars defects on the degree of disk degeneration at the L5-S1 level in cadaveric specimens. An observational study was performed of 690 cadaveric specimens selected at random. These specimens represent individuals who died between 1893 and 1938. The study included 558 male and 132 female cadavers. Of the 120 specimens with L5 spondylolysis, 95 cases were bilateral and 25 were unilateral. The remaining 544 specimens were used as the control cohort. Degenerative disk disease was measured by the classification of Eubanks et al. According to this classification, degenerative disk disease was graded from no arthrosis (grade 0) to complete ankylosis (grade IV). Linear regression analysis corrected for age, sex, and race showed that subjects with bilateral spondylolysis at L5 had a statistically significant increase in the amount of disk degeneration (P=.02) compared with those with unilateral lesions. Student's t tests showed significant differences (P<.001 and P=.002, respectively) in the amount of degeneration seen with both bilateral and unilateral spondylolysis above what would be predicted in the normal control population. A positive correlation was found between the number of pars defects at L5 and the degree of disk degeneration at L5-S1. These results support the idea that individuals with spondylolysis at these levels may be at increased risk for development of low back pain and reduced quality of life. [Orthopedics. 2017; 40(1):e59-e64.].

Analysis of Forensic Identification on 32 Cases of Lumbar Spondylolysis / 法医学杂志

OBJECTIVES@#To explore the casual relationship and the significance of identification among the injury, disease and damage consequence in the disability evaluation of lumbar spondylolysis by the standard for identifying grading of disability caused by work-related injuries.@*METHODS@#The general data, injury manner, clinical treatment and the imaging examination of 32 lumbar spondylolysis cases were collected and retrospectively analyzed. According to the degree of participation in the injury and damage consequence, the identification and assessment of casual relationship was made, and the grading of disability was assessed.@*RESULTS@#For 32 cases, injury had no effect on damage consequence in 7 cases, slight effect in 5 cases, secondary effect in 13 cases, equivalent effect in 4 cases, and complete effect in 3 cases. According to the related items in the standard for identifying grading of disability caused by work-related injuries, 3 cases were rated level 7, 5 cases were level 8, 6 cases were level 9, 11 cases were level 11 among the cases which existed causal relationship.@*CONCLUSIONS@#The formation of lumbar spondylolysis is connected to the factors of age, anatomy, occupation and injury manner etc. The degree of disability should be accessed comprehensively after the analysis of the casual relationship among the injury, disease and damage consequence.

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.

Errores diagnósticos en la columna / Diagnostic errors in examinations of the spine

El error radiológico más frecuente en la columna vertebral es la omisión de fracturas. Se considera la principal causa de demanda por negligencia al radiólogo tras la omisión del cáncer de mama y de pulmón. De los miles de informes de columna emitidos anualmente dependen, aparte de la salud de los pacientes, sus bajas laborales e indemnizaciones. Es por lo tanto nuestra responsabilidad conocer por qué se producen los errores y cómo detectarlos para evitar su repetición. En este artículo mostramos un espectro de los errores más frecuentes según nuestra experiencia en dobles lecturas de la columna vertebral, intentando en lo posible determinar su etiología (AU)

The most common radiological error in examinations of the spine is the failure to diagnose fractures. This is the third most frequent reason for lawsuits brought against radiologists for negligence, after the failure to diagnose breast cancer and the failure to diagnose lung cancer. The thousands of radiological reports of spinal examinations done every year affect not only patients’ health, but also their permission to be off work and their compensation. For this reason, it is our responsibility to know why errors are committed and how to detect them in order to avoid their repetition. In this article, we show the spectrum of the most common errors in our experience in double reading spinal examinations, and we try to determine what causes these errors (AU)

Clinical features of patients with pars defects identified in adulthood.

PURPOSE: Lumbar spondylolysis is considered a stress fracture of the pars interarticularis that occurs during growth. However, it is sometimes insidious and identified in adults as pseudoarthrosis, the terminal-stage of spondylolysis. The purpose of this study was to identify the clinical features of patients with terminal-stage spondylolysis that first manifested during adulthood. PATIENTS AND METHODS: Thirty-six patients (21 men, 15 women; mean age 55.8 years; age range 25-77 years) with low back pain (LBP) were studied. In all patients, lumbar spondylolysis had not been diagnosed until the first visit to our hospital. Patient data collected were history of athletic activity and LBP during their growth period and radiological findings, such as spinal level, displacement, and spina bifida occulta (SBO). RESULTS: Among the 36 patients, including a patient with multi-level spondylolysis (L4 and L5), a total of 37 vertebrae with terminal-stage spondylolysis were identified. Twenty-three (89.2 %) of the 37 vertebrae had L5 spondylolysis. Sixteen patients (44.4 %) had no history of athletic activity, 26 (72.2 %) had no experience of LBP during their growth period, and 14 (38.9 %) had neither. Twenty of the 37 vertebrae (70.4 %) involved displacement (grade 1 = 14; grade 2 = 6). In nine patients (25.0 %; eight men, one woman), SBO of the sacrum was accompanied by L5 spondylolysis. CONCLUSIONS: Approximately 90 % of patients with terminal-stage spondylolysis that was first diagnosed in adulthood involved the L5. Also, about 40 % had no history of athletic activity or experience of LBP during their growth period. In addition, only some patients with L5 spondylolysis had SBO, and all but one of these patients was male. This suggests that male patients with L5 spondylolysis may have some congenital predisposition.

Bilateral Pars Defects at the L4 Vertebra Result in Increased Degeneration When Compared With Those at L5: An Anatomic Study.

BACKGROUND: Cadaveric studies have examined disc degeneration at the L4-L5 and L5-S1 motion segments; however, we are not aware of another study that has examined the relationship between bilateral spondylolysis and its effect on degenerative disc disease at those levels. This may have been overlooked by researchers owing to the majority of spondylolysis occurring at the L5 vertebra. QUESTIONS/PURPOSES: Using osteologic specimens from a collection that included individuals who died in one city in the USA between 1893 and 1938, we asked: (1) do specimens with bilateral spondylolysis (bilateral pars defects) have increased levels of disc degeneration, at their respective motion segments, when compared with matched controls without spondylolysis, and (2) is the finding of a bilateral pars defect associated with more severe arthritis at L4-L5 than at L5-S1? METHODS: An observational study was performed on 665 skeletal lumbar spines from the Hamann-Todd Osteologic Collection at the Cleveland Museum of Natural History (Cleveland, OH, USA). The specimens included 534 males and 131 females ranging from 17 to 87 years old, with a nearly bell-shaped distribution of ages for males and a larger proportion of younger ages in the female specimens. Of those with spondylolysis, 81 had a defect at L5 and 14 had a defect at L4. The gross specimens were examined subjectively for evidence of arthrosis. At the time of examination, specific attention was not paid to the coexisting presence or absence of spondylolysis nor was the examiner blinded to the age of the specimens. Disc degeneration was measured by the classification of Eubanks et al., a modified version of the Kettler and Wilke classification. Linear regression was performed to derive a formula that would predict the amount of disc degeneration at L4-L5 and L5-S1 for the normal control population given a specimen's age, sex, and race. We then used this formula to evaluate the difference in disc degeneration at the corresponding level of the pars defect that is greater than the predicted amount for a control without spondylolysis. This allowed us to conclude that any significant differences found between the L4-L5 and L5-S1 cohorts were attributable to factors not simply inherent to their functional position in the spine of an individual without a bilateral pars defect. RESULTS: L4 spondylolysis and L5 spondylolysis showed greater amounts of degeneration compared with that of matched controls (L4 controls: mean = 1.52, SD = 0.74; L4 spondylolysis: mean = 3.21, SD = 0.87; p < 0.001; L5 controls: mean = 0.97, SD = 0.48; L5 spondylolysis: mean = 2.06, SD = 0.98; p < 0.001). When we controlled for the expected amount of degenerative disc disease at each level in controls, the observed degeneration was more severe at L4-L5 than at L5-S1 (p = 0.008, R-squared = 18.6). CONCLUSIONS: L4-L5 and L5-S1 bilateral spondylolysis groups had increased presence of degenerative disc disease compared with those without bilateral spondylolysis. For the same degree of spondylolysis, the observed amount of disc degeneration was greater at the L4-5 motion segment compared with L5-S1. CLINICAL RELEVANCE: Although not as common as the spondylolysis at L5-S1, we believe that our findings support that patients with L4-L5 spondylolysis can expect a greater degree of degenerative disc disease and increasing clinical symptoms. Multiple factors in the sacropelvic geometry of an individual, facet morphologic features at L4-L5, and the absence of the iliolumbar ligament at this level are possible contributing factors to the findings of this study.

Characteristics of lumbar spondylolysis in elementary school age children.

PURPOSE: Lumbar spondylolysis, a stress fracture of the pars interarticularis in the lumbar spine, is often precipitated by trauma, but there may be a congenital predisposition to this condition. There have been few studies on spondylolysis in young children, despite their suitability for studies on congenital defects. The aim of this study was to identify the clinical features of lumbar spondylolysis in elementary school age children in order to elucidate its pathogenesis. METHODS: Thirty lumbar spondylolysis patients (23 boys, 7 girls, including a pair of twins; mean age 9.5 years, age range 5-12 years) were studied. Patient data on history of athletic activity, symptoms at first consultation, and radiological findings such as spinal level, stage of the stress fracture, and skeletal age were collected. RESULTS: Among the 30 patients, 27 (21 boys, 6 girls) had L5 spondylolysis (90.0 %). Only 2 patients had no history of athletic activity at the first consultation. All patients, except for 2 whose diagnosis was incidental, complained of low back pain. In the 27 patients with L5 spondylolysis, 17 (63.0 %) had terminal-stage fracture and 25 (92.6 %) had spina bifida occulta (SBO) involving the S1 lamina. Sixteen of the 27 (59.3 %) had SBO involving the affected lamina (L5) and S1 lamina. In contrast, the 3 patients with L3 or L4 spondylolysis had no evidence of SBO. With respect to skeletal age, 23 of the 27 L5 spondylolysis patients (85.2 %) were in the cartilaginous stage while the remaining 4 patients were in the apophyseal stage. CONCLUSION: Lumbar spondylolysis in elementary school age children was commonly a terminal-stage bone defect at L5, which was not necessarily related to history of athletic activity and was sometimes asymptomatic. It was often associated with SBO, indicating a possible congenital predisposition. These findings may provide further insight into the pathogenesis of lumbar spondylolysis.