Risk Factors for Nonunion After Nonoperative Treatment for Pediatric Lumbar Spondylolysis: A Retrospective Case-Control Study.

BACKGROUND: Pediatric lumbar spondylolysis, a stress fracture of the lumbar spine, frequently affects young athletes, and nonoperative treatment is often the first choice of management. Because the union rate in lumbar spondylolysis is lower than that in general fatigue fractures, identifying risk factors for nonunion is essential for optimizing treatment. PURPOSE: To determine the risk factors for nonunion after nonoperative treatment of acute pediatric lumbar spondylolysis through multivariate analysis. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: We analyzed 574 pediatric patients (mean age, 14.3 ± 1.9 years) with lumbar spondylolysis who underwent nonoperative treatment between 2015 and 2022. Nonoperative treatment included the elimination of sports activities, bracing, and weekly athletic rehabilitation, with follow-up computed tomography. Patient data, lesion characteristics, sports history, presence of spina bifida occulta at the lamina with a lesion or at the lumbosacral spine excluding the lesion level, and lumbosacral parameters were examined. Differences between the union and nonunion groups were investigated using multivariate analysis to determine the risk factors for nonunion. RESULTS: Of the 574 patients, 81.7% achieved bone union. Multivariate analysis revealed that an L5 lesion and the progression of the main and contralateral lesion stages were significant independent risk factors for nonunion. An L5 lesion had a lower union rate than non-L5 lesions. As the main lesion progressed, the likelihood of nonunion increased significantly, and the progression of the contralateral lesion also showed a similar trend. Spina bifida occulta and lumbosacral parameters were not significant predictors of nonunion in this study. CONCLUSION: We identified the L5 lesion level and the progression of the main and contralateral lesion stages as independent risk factors for nonunion in pediatric lumbar spondylolysis after nonoperative treatment. These findings aid in treatment decision-making. When bone union cannot be expected with nonoperative treatment, symptomatic treatment is required without prolonged external fixation and rest, and without aiming for bone union. Individualized treatment plans are crucial based on identified risk factors.

Adolescent athlete low back pain diagnoses, characteristics, and management: A retrospective chart review.

OBJECTIVES: The aim of this study was to characterise the presentation, treatment, and management of adolescent athlete low back pain (LBP) as diagnosed in a clinical setting. The objectives were to 1) identify diagnoses associated with LBP in adolescent athletes; 2) categorise the differences in LBP diagnosis and presentation by sport, sex, BMI, and age; and 3) examine treatment and management methods of LBP in adolescent athletes. DESIGN: Retrospective chart review. METHODS: This retrospective medical chart review was conducted in the Sports Medicine Division of Boston Children's Hospital (BCH), a tertiary paediatric academic hospital. Data were collected and analysed from 363 adolescent athletes who had experienced LBP between 2015 and 2020. Chi-squared tests for association were used to assess for associations between LBP diagnoses and age, sex, BMI, and sport. Statistical analysis was conducted using SAS software version 9.4 (SAS Institute, Cary NC). RESULTS: Non-specific LBP was the most common LBP diagnosis amongst 363 adolescent athletes with LBP (34 %). This was closely followed by spondylolysis (28 %). There was a higher proportion of female athletes amongst participants diagnosed with facet-joint related pain (90 %) and SI-joint related pain (89 %) compared to the proportion of female athletes amongst participants diagnosed with spondylolysis (50 %). There was a high rate of diagnostic MRI usage in this cohort. Commonly used management techniques in this cohort were diagnostic MRI, physical therapy, relative rest, and bracing. CONCLUSIONS: An awareness of the sex-based differences in adolescent athlete LBP diagnoses may be useful for clinicians. It may be important to refine methods of diagnosis of LBP in this group, as there was a high rate of diagnostic MRI use. Future research should be directed towards the development of management guidelines specific to LBP in adolescent athletes to assist in the optimal management of this diagnosis.

[Slipped vertebrae (Spondylolysis): the underestimated weak point of the (pre)professional football player-an algorithm]. / Der Gleitwirbel: unterschätzte Schwachstelle des (prä)professionellen Fußballspielers ­ ein Algorithmus.

BACKGROUND: Isthmic spondylolysis represents the most common cause of spinal pain in adolescent athletes. This article provides an overview of the classification, diagnosis, and treatment options for these conditions, including conservative and operative measures. It also provides a treatment pathway to how young athletes with spondylolysis should be treated. DIAGNOSTICS: Diagnostic imaging techniques are essential for an accurate diagnosis, with CT scans providing additional information for surgical planning. TREATMENT: Conservative treatment focuses on activity modification and physiotherapy, with a phased approach tailored to individual patient needs. Operative intervention may be considered if conservative measures fail, with minimally invasive techniques such as Buck's screw fixation showing promising results. The decision between conservative and operative management should consider factors of the patients' individual profile. In this paper, we present the first treatment algorithm for the treatment of isthmic spondylolysis. Long-term prognosis varies, with most athletes able to return to sport following treatment.

Correlation of Radiographic Healing on Advanced Imaging in Young Adults and Adolescents With Symptomatic Spondylolysis Before and After Treatment: A Retrospective Study.

STUDY DESIGN: Retrospective chart review. OBJECTIVE: To determine the effect of conservative measures on radiographic outcomes in those with isolated spondylolysis. SUMMARY OF BACKGROUND DATA: Spondylolysis is a common cause of low back pain in pediatric patients, affecting between 4.4% and 4.7% of all pediatric patients. This rate is even higher in high-level athletes, with recent studies suggesting a rate of 47% in this population. Conservative measures are recommended for treating symptomatic spondylolysis and are effective in controlling symptoms, but there is little evidence regarding their effect on radiographic outcomes. METHODS: A retrospective review was conducted of patients diagnosed with spondylolysis who were treated at a single academic institution between January 1, 2012, and January 1, 2022. Data collected included demographics, presentation characteristics, pretreatment and post-treatment radiologic findings, types of treatments employed, and final symptomatic status at follow-up. The Student t test and the Wilcoxon rank sum test were used to compare continuous variables. The χ 2 test was used to compare categorical variables. RESULTS: A total of 119 patients were included in the study. There was an 81.5% rate of healing on advanced imaging for those treated with conservative measures. When comparing those with healing on advanced imaging to those without, those with healing were more likely to have an acute fracture ( P= 0.04), have symptomatic improvement ( P <0.01), and return-to-play ( P= 0.02) compared with those without. Those with healing also had an odds ratio of 6.9 ( P <0.01) and 4.5 ( P =0.02) to achieve symptomatic improvement and return to their sport, respectively, compared with those who did not. CONCLUSION: Our study found those with isolated spondylolysis who were treated with conservative measures had a high healing rate on advanced imaging and those with healing had significantly higher odds of having symptomatic improvement and returning to play compared with those without. LEVEL OF EVIDENCE: 4.

Characteristics of lumbar spondylolysis: L5 versus non-L5.

BACKGROUND: Fifth lumbar vertebra (L5) spondylolysis has a lower bone union rate than non-L5 spondylolysis, but the reason for this is unknown. This study aimed to evaluate the differences in patient and lesion characteristics between L5 and non-L5 spondylolysis. METHODS: A total of 410 patients with lumbar spondylolysis aged 18 years or younger who were treated conservatively were enrolled. Patients and lesions were divided into L5 and non-L5 (L2-L4) spondylolysis. Factors, including sex, age, presence of spina bifida occulta, stage of the main side lesion, whether the lesion was unilateral or bilateral, presence and stage of the contralateral side lesion and treatment duration, were evaluated at the first visit and compared between the two groups. RESULTS: A total of 250 patients with 349 lesions were included. The bone union rate of L5 lesions was lower than that of non-L5 lesions (75% vs. 86%, p = 0.015). Patients with L5 spondylolysis were more likely to be male (86% vs. 66%) and younger (14.0 vs. 14.6 years) than patients with non-L5 spondylolysis. Lesions of L5 spondylolysis were more likely to be in a progressive stage (28% vs. 15%), less likely to be in a pre-lysis stage (28% vs. 43%) and more likely to be in a contralateral terminal stage (14% vs. 5.3%, p = 0.013) compared with lesions of non-L5 spondylolysis. CONCLUSIONS: L5 spondylolysis was characterised by a lower bone union rate, more males, younger age, more progressive stage and more contralateral pseudarthrosis than non-L5 spondylolysis.

Main and contralateral side stages of lesion affected bone union in the conservative treatment of adolescent lumbar spondylolysis: a multivariable analysis of 217 patients and 298 lesions in a retrospective cohort study.

BACKGROUND: Factors affecting bone union in the conservative treatment of adolescent lumbar spondylolysis remain controversial. We aimed to examine these factors along with advances in diagnostic imaging using multivariable analysis of a sufficient number of patients and lesions. METHODS: In this retrospective study, high-school-aged patients or younger (n = 514) who were diagnosed with lumbar spondylolysis from 2014 to 2021 were investigated. We included patients with acute fractures who showed signal changes around the pedicle on magnetic resonance imaging and who completed conservative treatment. The following factors were investigated at the initial visit: age, sex, level of lesion, main side stage, presence and stage of contralateral side lesion, and presence of spina bifida occulta. The association of each factor with bone union was evaluated through a multivariable analysis. RESULTS: Altogether, 298 lesions in 217 patients (174 boys and 43 girls; mean age: 14.3 years) were included in this study. Multivariable logistic regression analysis of all factors showed that the main side progressive stage was more likely associated with nonunion as compared to the pre-lysis (OR: 5.86; 95% confidence interval [CI]: 2.00-18.8; p = 0.0011) and early stages (OR: 3.77; 95% CI: 1.72-8.46; p = 0.0009). Regarding the contralateral side stage, the terminal stage was more likely to be associated with nonunion. CONCLUSION: In the conservative treatment of lumbar spondylolysis, the factors affecting bone union were the main and contralateral side stages. Sex, age, level of lesion, or spina bifida occulta had no significant effects on bone union. The main, progressive, and contralateral side terminal stages were negative predictors of bone union. Trial registration This study was retrospectively registered.

Elastic Lumbar Support Versus Rigid Thoracolumbar Orthosis for Acute Pediatric Spondylolysis: A Prospective Controlled Study.

STUDY DESIGN: A prospective study on clinical, radiographic, and health-related quality of life (HRQoL) outcomes in children with acute spondylolysis treated with a rigid thoracolumbar orthosis or with an elastic lumbar support. OBJECTIVE: To compare outcomes of pediatric spondylosysis treated with a hard brace or an elastic lumbar support. SUMMARY OF BACKGROUND DATA: The benefits of the use of a rigid orthosis in treatment of spondylolysis are not clear. MATERIALS AND METHODS: Fifty-seven consecutive children with acute spondylolysis (mean age: 14.1 yr, range: 9-17 yr) were prospectively enrolled. Patients were treated with a rigid thoracolumbar orthosis (Boston brace) or with a low-profile, elastic lumbar support. First 14 patients were randomized the remaining 43 chose brace type themselves. Treatment period was four months. Treatment outcomes included bony union of the spondylolysis assessed with a computed tomography at four months and HRQoL using the Scoliosis Research Society-24 outcome questionnaire filled out before and after the treatment. RESULTS: Of the 57 patients, 54 completed the treatment protocol. Twenty-nine patients were treated using the Boston brace and 25 patients the elastic lumbar support. Bony union was obtained in 69.0% (20/29) of the Boston brace and in 60.0% (15/25) of the elastic lumbar support group patients. Difference in union rates was not significant (relative risk=1.14, 95% confidence interval: 0.44-2.98, P =0.785). There was no difference in the Scoliosis Research Society-24 total or domain scores at the end of follow-up between the treatment groups ( P >0.159 for all comparisons). In the whole cohort, the bony union did not predict better HRQoL in the end of the treatment ( P =0.869), although the pain domain improved significantly in the whole cohort ( P <0.001). CONCLUSIONS: A rigid thoracolumbar orthosis did not provide any benefits over an elastic lumbar support in terms of bony union or HRQoL outcomes in children with acute spondylolysis. LEVEL OF EVIDEN: 2.

Clinical Practice Patterns of Isthmic Spondylolysis in Young Athletes: A Survey of Pediatric Research in Sports Medicine Members.

ABSTRACT: Isthmic spondylolysis is a common cause of back pain in young athletes. The condition presents to numerous medical providers who employ a variety of different practices in diagnosis and management. The purpose of this study was twofold: to review the literature of diagnosis and management of the young athlete with isthmic spondylolysis and to survey Pediatric Research in Sports Medicine (PRiSM) members during the 2021 PRiSM Annual Meeting on practice patterns of diagnosis and management of the young athlete with isthmic spondylolysis. The response rate was 27%. Per respondents: 24% obtain oblique radiographs; 90% use magnetic resonance imaging as the advanced imaging modality; 60% treat with bracing; 57% recommend rest prior to physical therapy (PT); 53% prescribe return to sport activity restrictions. Although there are similarities in the diagnosis of isthmic spondylolysis in young athletes, this survey confirmed variability in management, especially bracing, timing of PT and return to sport activity restrictions.

Effects of low-intensity pulsed ultrasound on pain and functional disability in patients with early-stage lumbar spondylolysis: A randomized controlled trial.

BACKGROUND: Low Intensity Pulsed Ultrasound (LIPUS) is beneficial in accelerating fracture recovery, enhancing their capacity to execute tasks of daily life and, as a result, their autonomy. OBJECTIVE: To compare the outcomes of routine physical therapy and routine physical therapy along with LIPUS in patients with early-stage lumbar spondylolysis. METHODS: Thirty-four (29 males and 5 females) patients exhibiting symptomatic low back pain for at least four weeks were recruited and randomly divided into control group (CG) and intervention group (IG) group. Randomization was done by using goldfish bowl method and allocation was done by using sealed envelope method. Parallel assignment was done. Numeric Pain Rating Scale (NPRS) was utilized for the measurement of pain and Oswestry Disability Index (ODI) for functional disability. Patients were assessed at baseline, at the end of 12th and 20th week. Interventions were applied by two physical therapists (one male and one female) having more than eight years of clinical experience for 10 weeks on alternate days. RESULTS: Intervention group reported significant percentage change of 47% at 12th week and 65% at 20th week for pain and 42% at 12th week and 81% at 20th week for functional disability compared with 40% at 12th week and 37% at 20th week for pain and 3% at 12th week and 25% at 20th week follow-up for functional disability from baseline in control group. CONCLUSION: Low-intensity pulsed ultrasound has significantly reduced pain and functional disability in patients with early-stage lumbar spondylolysis by using following parameters; 1.1-MHz oscillation frequency, 1-kHz pulsed frequency, 100-mW/cm2 spatial intensity, 2 ms pulse duration, 100Hz pulse repetition rate, 20% pulse duty cycle, and 20-min duration on alternate days.

Management of lumbar spondylolysis in the adolescent athlete: a review of over 200 cases.

BACKGROUND: Spondylolysis is a defect of the pars interarticularis of vertebrae, most commonly seen at L5 and L4. The etiology of spondylolysis and isthmic spondylolisthesis is generally considered to be a result of repetitive mechanical stress to the weak portion of the vertebrae. A higher incidence of spondylolysis is observed in young athletes. Symptomatic spondylolysis can be successfully treated conservatively, but there is currently a limited consensus on treatment modalities and a lack of large-scale clinical trials. PURPOSE: The purpose of the present study was to investigate the optimal treatment algorithm for symptomatic spondylolysis in adolescent athletes and evaluate the functional outcomes of those undergoing the nonoperative treatment. STUDY DESIGN: A retrospective review. PATIENT SAMPLE: Two hundred one adolescent patients ranging from age 10 to 19 involved in athletics OUTCOME MEASURES: Injury characteristics (age, mechanism, time), sports played, bone stimulator use, bony healing at 3 months on computed tomography (CT) scans, return to sports, corticosteroid injection use. METHODS: Two hundred one adolescent athlete patients (62 females and 139 males) diagnosed with spondylolysis between 2007 and 2019 were retrospectively reviewed. Diagnosis was based on plain radiography followed by magnetic resonance imaging. All patients were treated conservatively with cessation of sports activity, thoracolumbosacral orthosis, and external bone stimulator for three months after diagnosis. CT scans were obtained for the 3-month follow-up visits to assess bony healing. Subsequently the patients received 6 weeks of rehabilitation focused on core strengthening. Symptomatic patients after the treatment were referred for steroid injections and continued with the rehabilitation protocol. RESULTS: The most common age of injury was 15 years old, following a strong normal distribution. The most commonly played sport was football, followed by baseball/softball. The primary mechanism of injury was weight training closely followed by a football injury. The first quarter of the calendar year had the highest incidence of injuries with the most injuries occurring in March and the least occurring in December. One hundred fifty-two athletes reported using bone stimulators as prescribed, and these patients showed a significantly higher rate of bony healing on follow-up CT scans than those who did not use bone stimulators. One hundred ninety-seven patients (98%) returned to sports or similar level of activities. Thirty-seven patients (18%) received facet or epidural steroid injections due to continued pain and one patient underwent a surgical procedure. Follow-up CT scans showed 49.8% bony healing. CONCLUSIONS: Conservative treatment of spondylolysis in adolescent athletes with cessation of sports, thoracolumbosacral orthosis, and bone stimulator followed by rehabilitation was associated with excellent outcomes in terms of return to sports.

Characteristics of recurrent cases after conservative therapy in adolescent lumbar spondylolysis.

Occasionally lumbar spondylolysis in adolescents will recur after conservative treatment. The goal of this study was to retrospectively review the conditions in which recurrence transpired in a subset of adolescent patients diagnosed with acute lumbar spondylolysis. A retrospective survey was conducted in 141 patients who had been treated for spondylolysis and had obtained bone union. Twenty subjects were selected who had recurrent lumbar spondylolysis after returning to sports activity following the initial spondylolysis treatment. There were 18 males and two females with an average age at the time of initial visit of 13.3 years and 14.1 years at the time of recurrence. The average period of initial treatment was 101 days, and the average time to recurrence after healing was 149 days. There were three cases at L3, two cases at L4 and 15 cases at L5. At recurrence, 18 patients had unilateral involvement and two patients presented with bilateral occurrence. Four cases did not achieve bony union. In this study, the recurrence rate was 13.2%. Eighty percent of cases had recurrence within six months after healing. After recurrence, 20% of the cases reached pseudoarthrosis. It is useful to take regular MRI images to detect recurrence within six months after returning to sports.

Role of low-intensity pulsed ultrasound on lumbar spondylolysis: A systematic review.

OBJECTIVE: To systematically review the role of low-intensity pulsed ultrasound on lumbar spondylolysis. METHODS: Literature search was conducted on PubMed, Embase, CINAHL, Web of Science, PEDro and Scopus databases to identify relevant studies published between 2010 and 2020 by using medical subject headings and applying Booleans, such as low-intensity pulsed ultrasound OR interventional ultrasound AND lumbar spine OR lumbar region AND spondylolysis OR stress fracture. Unpublished studies were hand-searched in the journals, abstracts of conferences were reviewed, and citation index was used for searching experts in the field and then contacting them for information. Studies included were the ones that had at least one of the following outcomes: bone union rate, treatment period to bone union and time to return to previous activities. RESULTS: Of the 243 studies identified, 228(94%) were full text articles and only 2(0.8%) studies were critically appraised for qualitative synthesis based on bone union rate, treatment period to bone union, and time to return to previous activities. CONCLUSIONS: Low-intensity pulsed ultrasound was found to be effective for bone union and a useful therapy for quick return to playing sports in patients with lumbar spondylolysis.

Conservative treatment of spondylolysis involving exercise initiated early and sports activities resumed with a lumbar-sacral brace.

BACKGROUND: Conservative treatment including the use of a brace and cessation of sports activities is known to be effective in spondylolysis. However, there is some controversy regarding [1] the type of brace, and [2] the endpoint for bracing, and [3] the timing of resumption of sports activities. The aim of the current study was to investigate the appropriateness of early exercise and resumption of sports activities with a lumbar-sacral brace in very early- and early-stage lumbar spondylolysis. METHODS: This prospective cohort study enrolled 45 patients with very early- and early-stage lumbar spondylolysis. A lumbar-sacral brace, structured to be a hard brace in the back and a mesh brace in the front, was used. Isometric exercises/stretching was started immediately after the initial visit. The number of patients for whom bone fusion was fully achieved on CT and the disappearance of signal intensity change on MRI were investigated. RESULTS: In 12 cases of very early-stage spondylolysis, the average elapsed time until signal intensity disappearance as confirmed on MRI was 4.3 ± 1.6 months. Bony union on CT was confirmed in all cases. In 33 cases of early spondylolysis, signal intensity change disappeared on MRI within 5.2 ± 2.4 months. The rate of bony union was 94.3%, and the average period required to achieve bony union observable on CT was 3.7 ± 1.0 months. CONCLUSIONS: Sufficient bony union can be achieved by conservative treatment with early exercise and a lumbar-sacral brace in cases of very early and early spondylolysis.

Union evaluation of lumbar spondylolysis using MRI and CT in adolescents treated conservatively.

BACKGROUND: This study evaluated the union rate of acute lumbar spondylolysis in patients treated conservatively, according to the protocol. METHODS: The subjects included high school students and younger patients who were diagnosed with lumbar spondylolysis presenting bone marrow edema. We investigated the union rate, the period until union, unilateral or bilateral, vertebral level, laterality (right or left), and pathological stage at the first visit. Some unilateral cases included bilateral spondylolysis with contralateral pseudarthrotic lesion; therefore, the union rate of the "true" unilateral case in which the contralateral side was normal was calculated. We excluded multi-level lesions. RESULTS: With conservative treatment for lumbar spondylolysis of 189 lesions in 142 cases, 144 healed and 45 were considered as nonunion. The average treatment period until union was 106 days. The union of "true" unilateral cases in which the contralateral side was normal was noted in 68/71 lesions, but that of bilateral cases was noted in 71/94 lesions. The union in L3, L4, and L5 vertebrae was noted in 15/17, 40/49, and 89/123 lesions, respectively. The union was observed in 63/87 on the right and 86/102 on the left. The union was noted in the pre-lysis, early, and progressive stages in 36/39, 81/97, and 27/53 lesions, respectively. Furthermore, the union was noted in stages 0, 1a, 1b, 1c, and 2 in 13/15, 47/52, 30/36, 34/42, and 20/44 lesions, respectively. CONCLUSION: Accurate union evaluation using CT and MRI showed a union rate of 76% with conservative treatment for spondylolysis. The union rate of the "true" unilateral cases in which the contralateral side was normal was 96%, which was significantly higher than that of the bilateral cases. Moreover, the union rate of lesions in the axial progressive stage and sagittal stage 2 was significantly lower than that of lesions in other stages. STUDY DESIGN: clinical retrospective study.

Direct medical costs after surgical or nonsurgical treatment for degenerative lumbar spinal disease: A nationwide matched cohort study with a 10-year follow-up.

OBJECTIVE: The demand for treating degenerative lumbar spinal disease has been increasing, leading to increased utilization of medical resources. Thus, we need to understand how the budget of insurance is currently used. The objective of the present study is to overview the utilization of the National Health Insurance Service (NHIS) by providing the direct insured cost between patients receiving surgery and patients receiving nonsurgical treatment for degenerative lumbar disease. METHODS: The NHIS-National Sample Cohort was utilized to select patients with lumbar disc herniation, spinal stenosis, spondylolisthesis or spondylolysis. A matched cohort study design was used to show direct medical costs of surgery (n = 2,698) and nonsurgical (n = 2,698) cohorts. Non-surgical treatment included medication, physiotherapy, injection, and chiropractic. The monthly costs of the surgery cohort and nonsurgical cohort were presented at initial treatment, posttreatment 1, 3, 6, 9, and 12 months and yearly thereafter for 10 years. RESULTS: The characteristics and matching factors were well-balanced between the matched cohorts. Overall, surgery cohort spent $50.84/patient/month, while the nonsurgical cohort spent $29.34/patient/month (p<0.01). Initially, surgery treatment led to more charge to NHIS ($2,762) than nonsurgical treatment ($180.4) (p<0.01). Compared with the non-surgical cohort, the surgery cohort charged $33/month more for the first 3 months, charged less at 12 months, and charged approximately the same over the course of 10 years. CONCLUSION: Surgical treatment initially led to more government reimbursement than nonsurgical treatment, but the charges during follow-up period were not different. The results of the present study should be interpreted in light of the costs of medical services, indirect costs, societal cost, quality of life and societal willingness to pay in each country. The monetary figures are implied to be actual economic costs but those in the reimbursement system instead reflect reimbursement charges from the government.

Conservative treatment for lumbar spondylolysis in children of elementary school age.

PURPOSE: Lumbar spondylolysis in children of elementary school age has different characteristics from those of junior or senior high school patients. The purpose of the present study was to investigate the outcomes of conservative treatment for lumbar spondylolysis in patients of elementary school age. METHODS: We included 46 lesions in 32 consecutive patients of elementary school age with fresh cases of lumbar spondylolysis (5 girls and 27 boys; mean age, 11.3 years). We examined the relationship between bone union after conservative treatment and factors such as the CT axial staging, whether the lesion was unilateral or bilateral, whether the contralateral lesion was terminal stage, and the presence of spina bifida occulta. RESULTS: Bone union was achieved in 33 lesions (72%) in 23 patients, whereas 13 lesions (28%) in 9 patients could not obtain bone union. The proportion of unilateral lesions with bone union was 13 of 13 (100%), significantly higher than that for bilateral lesions (20/33 lesions, 61%, p = 0.009). Of the 33 bilateral lesions, bone union was attained in 20 of 28 (71%) lesions without contralateral terminal stage, whereas bone union was not attained in any of 5 (0%) lesions with contralateral terminal stage, showing a significant difference between those with or without contralateral terminal stage (p = 0.005). CONCLUSION: Bilateral lesions and contralateral terminal stage are possible unfavorable factors to bone union in conservative treatment for patients of elementary school age with lumbar spondylolysis. Early diagnosis and treatment before the lesions become bilateral or progressive stage are important.