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Abstract After surgery for intradural lesions, dural reconstruction is essential for preventing cerebrospinal fluid (CSF) leakage, which can cause serious complications. However, there is currently no established intraoperative procedure. While hydrophobic polyglycolic acid (PGA) sheets and fibrin glue are effective for dural reconstruction, the usefulness of hydrophilic artificial dura mater made of a porous collagen matrix has also been reported. This study aimed to compare the ability of a fibrin-coated porous collagen matrix and a fibrin-coated PGA sheet to prevent CSF leakage during spinal surgery. This study included 319 patients who underwent surgery for intradural lesions requiring dural reconstruction. Patients in the PGA sheet group (group P) and the porous collagen matrix group (group C) were compared. The median age was 60 years. A total of 319 patients were included, with 219 in Group P and 100 in Group C. CSF leakage occurred in 11 patients (5.0%) in Group P and 0 patients in Group C (P

Graphical Abstract

Introduction: Studies describing the relationship between the hip and spine have reported that corrective spinal surgery for adult spinal deformity (ASD) affects the orientation of the acetabulum. However, the extent to which spinal correction in ASD affects acetabular anteversion in the standing position is unclear, especially after total hip arthroplasty, for which dislocation is a concern. The purpose of this study was to evaluate changes in anterior acetabular coverage in the upright position due to extensive correction surgery for ASD. Methods: Thirty-six consecutive patients who had undergone spinal corrective surgery from the thoracolumbar region to the pelvis were enrolled and evaluated. The ventral-central-acetabular (VCA) angle and anterior acetabular head index (AAHI) were measured with a false-profile view to evaluate the relationship between acetabular anteversion in the standing position and spinopelvic parameters before and after surgery. The spinopelvic parameters measured included thoracic kyphosis, pelvic incidence, pelvic tilt (PT), sacral slope, lumbar lordosis (LL), sagittal vertical axis, and global tilt. Results: The VCA angle and AAHI were significantly increased after spinal deformity correction (p

Objective To elucidate the patient characteristics and outcomes of emergency surgery for spinal metastases and identify risk factors for emergency surgery. Methods We prospectively analyzed 216 patients with spinal metastases who underwent palliative surgery from 2015 to 2020. The Eastern Cooperative Oncology Group performance status, Barthel index, EuroQol-5 dimension (EQ5D), and neurological function were assessed at surgery and at 1, 3, and 6 months postoperatively. Multivariate analysis was performed to identify risk factors for emergency surgery. Results In total, 146 patients underwent nonemergency surgery and 70 patients underwent emergency surgery within 48 hours of diagnosis of a surgical indication. After propensity score matching, we compared 61 patients each who underwent nonemergency and emergency surgery. Regardless of matching, the median performance status and the mean Barthel index and EQ5D score showed a tendency toward worse outcomes in the emergency than nonemergency group both preoperatively and 1 month postoperatively, although the surgery greatly improved these values in both groups. The median survival time tended to be shorter in the emergency than nonemergency group. The multivariate analysis showed that lesions located at T3–10 (p = 0.002; odds ratio [OR], 2.92; 95% confidence interval [CI], 1.48–5.75) and Frankel grades A–C (p < 0.001; OR, 4.91; 95% CI, 2.45–9.86) were independent risk factors for emergency surgery. Conclusion Among patients with spinal metastases, preoperative and postoperative subjective health values and postoperative survival are poorer in emergency than nonemergency surgery. Close attention to patients with T3–10 metastases is required to avoid poor outcomes after emergency surgery.

Abstract Objectives This study aimed to investigate the relationship between postoperative reconstructed tongue flap volume (RTFV) and body mass index (BMI) and identify factors affecting the flap volume in patients with tongue squamous cell carcinoma. Methods Thirty‐two patients were evaluated for RTFV from computed tomography images and BMI. The first and second evaluations were done at 6 months and 1.5 years after surgery respectively. RTFV rate changes and BMI differences from the first and second evaluations were calculated. The correlation between RTFV rate change and BMI difference was assessed using Spearman's rank correlation coefficient. Multiple regression analysis evaluated the relationship between the flap volume rate change and age, sex, flap type, and BMI difference to identify influencing factors. Results The flap volume rate change and BMI difference correlated significantly (r = .594, p

Objective: The accurate assessment of the involvement of mandibular gingival squamous cell carcinoma (SCC) is essential for determining the extent of resection and is also useful for predicting lymph node metastasis and prognosis. The purpose of this study was to investigate the factors for predicting the prognosis. Study design: We reviewed 134 patients with mandibular gingival SCC treated between 2008 and 2017. The clinical findings, TN stage, relationship between radiographical type and histological pattern, and factors affecting the survival rate were investigated. Results: The moth-eaten radiographic type was significantly associated with histologically infiltrative pattern. For all 134 cases, the 5-year OS was 89.5 %, and 5-year DSS was 93.9 %. The 5-year DSS was 95.0 % for cN0 and/or pN0 cases and 90.3 % for pN (+) cases, with a significant difference. The significant risk factors for lymph node metastasis were teeth extractions by previous physicians and moth-eaten radiographic type. Conclusion: The risk factor for poor prognosis was lymph node metastasis. In addition, teeth extractions by previous physicians and moth-eaten radiographic type were the risk factors for lymph node metastasis. It is recommended that these cases be treated considering the possibility of cervical lymph node metastasis.

BackgroundThis study aimed to determine the patterns of invasion of oral squamous cell carcinoma (OSCC) into the bucco-mandibular space (BMS) using detailed histopathological analysis and to assess clinical outcomes.MethodsPatients with OSCC who underwent segmental mandibulectomy or hemi-mandibulectomy combined with resection of the BMS between 2012 and 2021 were included. The invasions of the BMS were classified into three patterns. Pattern A was defined as a horizontal invasion, Pattern B as a vertical invasion, and Pattern C as an expansive invasion.ResultsIn total, 109 patients were reviewed. Of these 109 patients, the primary tumor affected the lower gingiva in 78 patients, the buccal mucosa in 18 patients, and was a primary intraosseous carcinoma of the mandible in 13 patients. Invasion of the BMS was significantly associated with a higher pathological T stage, positive/close margins, and lower disease-free survival (DFS) rates. The DFS rates were 86.7% and 66.0% in the BMS non-invasion and invasion groups, respectively. The DFS rates for each type of invasion were 82.1% for Pattern A, 67.4% for Pattern B, and 48.0% for Pattern C (P=0.277).ConclusionPatients with BMS invasion have a poorer prognosis than those without invasion of the BMS. Therefore, adjuvant therapy is necessary, especially in Patterns B and C. Evaluation of preoperative BMS invasion patterns is important for predicting the prognosis of OSCC.

We investigated whether capuchin monkeys could use information about rewarded and unrewarded stimuli such that chain-ing of their response patterns would in principle generate increasingly successful performances, indicative of potential forcumulative culture. Two populations of tufted capuchin monkeys were tested using a touchscreen stimulus-selection taskrequiring subjects to learn the strategy of repeating rewarded, and avoiding unrewarded selections following demonstra-tions of varying success. Although capuchins outperformed demonstrations of chance-level performance (simulating per-formance of a nave individual), they did not consistently outperform demonstrations of above-chance-level success. Thissuggests that, in a social transmission scenario, the accumulation of beneficial information over successive transmissionevents would be relatively limited. Despite mastering the task contingencies, the capuchins did not use the informationoptimally, limiting the potential for cumulative culture. Our data may provide insights into factors constraining cumulativeculture in the natural behaviour of non-humans.

Abstract Humans communicate with each other through language, which enables us talk about things beyond time and space. Do non-human animals learn to associate human speech with specific objects in everyday life? We examined whether cats matched familiar cats’ names and faces (Exp.1) and human family members’ names and faces (Exp.2). Cats were presented with a photo of the familiar cat’s face on a laptop monitor after hearing the same cat’s name or another cat’s name called by the subject cat’s owner (Exp.1) or an experimenter (Exp.2). Half of the trials were in a congruent condition where the name and face matched, and half were in an incongruent (mismatch) condition. Results of Exp.1 showed that household cats paid attention to the monitor for longer in the incongruent condition, suggesting an expectancy violation effect; however, café cats did not. In Exp.2, cats living in larger human families were found to look at the monitor for increasingly longer durations in the incongruent condition. Furthermore, this tendency was stronger among cats that had lived with their human family for a longer time, although we could not rule out an effect of age. This study provides evidence that cats link a companion's name and corresponding face without explicit training.

Study design. Multicenter case-control study. Objective. To identify imaging characteristics of the cervical spine in patients with retro-odontoid pseudotumor (ROP) without rheumatoid arthritis (RA) and determine the pathogenesis of ROP. Background. ROP results from proliferative changes in the soft tissue of the atlantoaxial junction surrounding the region of the transverse ligament, and is commonly seen in RA patients. However, the pathogenesis of ROP caused by mechanical instability of the upper cervical spine in patients without RA is yet to be explained. Materials and Methods. We collected imaging data [preoperative radiographs, magnetic resonance imaging (MRI), and computed tomography (CT)] of patients who underwent surgery between April 2011 and March 2022 at the three university hospitals for ROP (cases) and cervical spondylotic myelopathy (as age, sex, and institution matched controls). The two groups were compared for different parameters on cervical dynamic radiographs, MRI, and CT. Results. The ROP group consisted of 42 patients, and the control group comprised 168 patients. C2-C7 range of motion was significantly smaller in the ROP group (25.8 ± 2.6°) compared with the control group (33.0 ± 1.0°). C2-C7 sagittal vertical axis was significantly larger in the ROP group than the control group (39.3 ± 3.6 vs. 32.2 ± 1.3 mm). MRI and CT assessment showed progressive degeneration at all intervertebral levels in the ROP group. A significant positive correlation was observed between the thickness of the soft tissue posterior to the dental process and the atlantodental interval in the flexion position (r = 0.501). Conclusions. The development of ROP was associated with degeneration of facet joints and intervertebral disks in the middle and lower cervical spine. Our findings suggest that decreased mobility of the middle and lower cervical spine may cause instability in the upper cervical spine, leading to the formation of ROP. [ABSTRACT FROM AUTHOR]

Across the world, more and more cats are being kept in captive spaces such as homes, animal shelters, and cat cafés. There is a growing need to understand whether cross-cultural differences influence human–animal interactions in these human-controlled environments. Cats are one of the world's most popular companion animals, and both the US and Japan have high rates of cat ownership. However, cultural differences may account for differences in how people feel about cats and how humans and cats behave toward one another. The research aim was to examine whether differences exist between the US and Japan across multiple facets of the human–cat relationship. Study 1 examined each country's attitude toward pet cats. Results indicate US citizens have significantly more positive attitudes toward pet cats than Japanese citizens. Study 2 examined owner attachment to their cat and pet cat social behavior. Results indicate owners in both countries were highly attached to their cats. In the US, but not Japan, owner attachment level predicted pet cat sociability toward the owner. Study 3 examined cat social behavior in cat cafés. The results of studies 2 and 3 indicate that pet cats and café cats in the US spend a greater proportion of time in proximity to people compared with pet and café cats in Japan. In all, differences and similarities were seen between the US and Japan. In humans, differences in childhood cat experiences and lower rates of cat ownership may impact attitudes toward cats. In pet cats, owner characteristics, the size of the cat's environment, cat care practices, and attitudes toward cats may impact cat social behavior. Future exploration in this area can benefit our understanding of cross-cultural human–animal interactions and how to apply these findings to improve captive-cat welfare. [ABSTRACT FROM AUTHOR]

Background and Objectives: Adenoid cystic carcinoma (ACC) of the head and neck is generally slow-growing but has a high potential for local recurrence and metastasis to distant organs. There is currently no standard pharmacological treatment for recurrent/metastatic (R/M) ACC, and there are cases in which immune checkpoint inhibitors (ICIs) are administered for ACC according to head and neck squamous cell carcinoma (HNSCC). However, the efficacy of ICIs for ACC remains unclear, and the predictive biomarkers need to be elucidated. Materials and Methods: The Center for Cancer Genomics and Advanced Therapeutics (C-CAT) database enabled the retrospective but nationwide analysis of 263 cases of ACC of the head and neck. Then, we examined and reported four cases of ACC that received ICIs and comprehensive genomic profiling (CGP) in our institution. Results: The C-CAT database revealed that 59 cases out of 263 received ICIs, and the best response was 8% of objective response rate (ORR) and 53% of disease control rate (DCR) (complete response, CR 3%, partial response, PR 5%, stable disease, SD 44%, progressive disease, PD 19%, not evaluated, NE 29%). The tumor mutational burden (TMB) in ACC was lower overall compared to HNSCC and could not be useful in predicting the efficacy of ICIs. Some cases with MYB structural variants showed the response to ICIs in the C-CAT database. A patient with MYB fusion/rearrangement variants in our institution showed long-term stable disease. Conclusions: ICI therapy is a potential treatment option, and the MYB structural variant might be a candidate for predictive biomarkers for immunotherapy in patients with R/M ACC.

Abstract Background Diffuse large B-cell lymphoma (DLBCL) is the most common type of lymphatic tumor; however, extranodal DLBCLs that exhibit initial symptoms in the maxilla and mandible are rare. Moreover, DLBCL is clinically classified as a moderate to highly malignant lymphatic tumor that can progress rapidly; therefore, early diagnosis is crucial. However, diagnosis is difficult as the disease causes a diverse range of clinical symptoms with no characteristic imaging findings. We conducted a clinical investigation to clarify the clinical characteristics of DLBCL that exhibits initial manifestation in the maxilla and mandible. Methods Of the 2748 patients with malignant tumors of the oral and maxillofacial region examined at our hospital during a period of 11 years between January 2006 and December 2016, 27 primary cases diagnosed with DLBCL based on the chief complaint of symptoms in the gingiva and bone of the maxilla and mandible were enrolled in this study. Evaluations were based on sex, age, whether treatment was provided by a previous physician, symptoms, duration of disease until treatment was sought, clinical diagnosis, laboratory findings, and imaging results. Results There were 15 cases that involved the maxilla and 12 that involved the mandible. The median duration of disease until treatment was sought was 60 d (3–450 d). All cases exhibited a tumor or a mass, and hypoesthesia of the chin was confirmed in eight cases wherein the mandible was involved. The clinical stages were stage I in eight cases, stage II in ten cases, and stage IV in nine cases. Serum lactate dehydrogenase (LDH) levels were elevated in 13 of 22 patients. The overall survival rate was 63%. Conclusions Symptoms associated with nontender swelling and numbness of the lip or chin in the absence of other findings such as dental infections should raise suspicions about DLBCL. Patients should be provided appropriate imaging and accurate biopsy assessments to improve prognosis.

Abstract Background Metastasis of infradiaphragmatic tumors to the left supraclavicular lymph node is reported to be rare. When metastasis is detected in the left supraclavicular node in patients with head and neck carcinoma, locating the primary cancer remains a difficult and time-consuming challenge despite the dramatic development of screening technologies and treatment methods. Case presentation We report three cases of malignant infradiaphragmatic tumor diagnosed following an initial finding of left supraclavicular node metastasis after surgery for tongue squamous cell carcinoma (follow-up period, range 18–62 months). In these cases, adenocarcinoma was diagnosed based on left supraclavicular node biopsies, and a second primary tumor was found, in a 78-year-old Japanese woman with a diagnosis of cholangiocarcinoma, a 64-year-old Japanese man with a diagnosis of bladder carcinoma, and a 61-year-old Japanese man with a diagnosis of prostate carcinoma. In the cholangiocarcinoma case, carbohydrate antigen 19-9 and alpha-fetoprotein levels helped to diagnose cholangiocarcinoma. Palliative care only was given, with survival for 11 months after diagnosis of lymph node metastasis. In the bladder carcinoma case, pathological analysis of fine-needle aspiration biopsy specimen of the metastatic cervical lymph node showed atypical cells with slight squamous differentiation. Hematoxylin–eosin staining of the bladder lesion did not identify a clear glandular or squamous component, and we could not make a definitive diagnosis of whether the lesion was poorly differentiated squamous cell carcinoma, adenocarcinoma, or high-grade urothelial carcinoma. GATA3 staining aided in the diagnosis of urothelial bladder cancer with left supraclavicular node metastasis. He survived for 2 months after diagnosis of left supraclavicular lymph node metastasis. In the prostate carcinoma case, 18F‐fluorodeoxyglucose uptake was weak. Prostate-specific antigen levels and magnetic resonance imaging findings aided the diagnostic process. This patient underwent bilateral orchiectomy and adjuvant hormonal therapy and survived for 47 months after diagnosis of left supraclavicular node metastasis. Conclusions Pathological diagnosis on the basis of immunohistochemistry and specific diagnosis methods such as radiological and serological assessments are important for providing rapid diagnosis and appropriate treatment.

Shame can be defined as the emotional response to one's violations of rules being exposed to others. However, it is difficult to objectively measure this concept. This study examined the psychophysiological indicators of shame in young children using behavioral methods and thermography, which measures facial temperatures that reflect blood flow changes related to emotions. Four- to six-year-old children participated in an "animal guessing game," in which they lied about having violated a rule. They were assigned to either the exposure or the non-exposure group. In the exposure group, participants' lies were exposed by the experimenter, whereas in the non-exposure group, their lies were not. Results showed that at the behavioral level, participants in the exposure group expressed characteristic behaviors of shame (e.g., embarrassed smiles) more often than those in the non-exposure group. Moreover, the nasal temperatures of participants in the exposure group were higher than those of participants in the other group after the lie was exposed. These results suggest that participants' lies being exposed induced psychophysiological responses and consequently raised their nasal temperature. This finding indicates that psychophysiological responses can enable us to objectively measure higher-order emotions in young children.

Abstract Squamous cell carcinoma (SCC) of the tongue rarely metastasizes to the lingual lymph nodes (LLNs), which are inconstant nodes and often situated outside the areas of basic tongue tumor surgery. The current study evaluated the clinicopathological features and prognostic impact of LLN metastasis (LLNM), compared to that of cervical lymph node metastasis, in patients with tongue SCC. A total of 608 patients underwent radical surgery for tongue SCC at our department between January 2001 and December 2016. During neck dissection, we scrutinized and resected lateral LLNs, when present. Of the 128 patients with lymph node metastasis, 107 had cervical lymph node metastasis and 21 had both cervical lymph node metastasis and LLNM. Univariate analysis demonstrated that LLNM was significantly associated with the adverse features of cervical lymph node metastasis. The 5-year disease-specific survival (5y-DSS) was significantly lower in patients with LLNMs than in those without LLNMs (49.0% vs. 88.4%, P

Abstract The purpose of this study was to evaluate which radiological depth of invasion (r-DOI) measurement is the most concordant to clinical DOI (c-DOI) derived from correction for the shrinkage rate of the histopathological specimens. We retrospectively reviewed 128 patients with tongue carcinoma who had undergone glossectomy between 2006 and 2019. At first, the width shrinkage rate during formalin fixation and preparation process of histopathological specimens was evaluated. From the shrinking rates, a formula to calculate c-DOI from pathological DOI (p-DOI) was developed. The correlation between c-DOI and r-DOI was evaluated. The specimen shrinkage rate during the histopathological specimen preparation process was 10.3%. Based on that, we yielded the correct formula for c-DOI based on p-DOI and preparation shrinkage rate: c-DOI = p-DOI × 100/89.7. The regression equations for the association of c-DOI with r-DOI measured by ultrasound (n = 128), MRI before biopsy (n = 18), and MRI after biopsy (n = 110) were y = 1.12 * x + 0.21, y = 0.89 * x − 0.26, and y = 0.52 * x + 2.63, respectively, while the coefficients of determination were 0.664, 0.891, and 0.422, respectively. In conclusion, r-DOI using MRI before biopsy most strongly correlated with c-DOI.

Abstract A 49‐year‐old man, who had not been vaccinated against COVID‐19 visited the hospital for fever and cough, and a PCR test for COVID‐19 was positive on the Day X. Initially, there was no decrease in oxygen saturation and the patient was under observation as a mild case without medication. Five days after the onset (Day X + 5), chest pain appeared. Electrocardiogram showed widespread ST‐segment elevation, and blood tests showed high levels of troponin I. However, given that there was no stenotic lesion on coronary computed tomography, myocarditis was suspected, and he was transferred to our hospital on the Day X + 6. We started treatment with lemdesivir and dexamethasone. On the Day X + 7, the patient developed decreased left ventricular ejection fraction, hypotension, and hyperlactatemia. We decided that mechanical circulatory support was necessary and an Impella 5.0 was inserted under ventilator management. The patient was successfully weaned from the Impella 5.0 on the Day X + 17, was transferred to the general ward on the Day X + 24, continued rehabilitation, and was discharged home on the Day X + 39 with no heart failure symptoms. In this case, we performed daily bedside echocardiography and chose the Impella 5.0 instead of extra corporeal membrane oxygenation (ECMO) because there were no findings of severe pneumonia or right heart failure. The Impella 5.0 device was inserted via an axillary artery approach, given that it provides more assisted flow than the Impella CP inserted through the inguinal route. Furthermore, early rehabilitation was possible due to the lack of restriction of the lower body.

Background: There are a few reports on antibody responses after a two-dose BNT162b2 vaccination in non-epidemic areas. We evaluated this phenomenon. Methods: A total of 344 healthcare workers were vaccinated, and the serum anti-receptor-binding domain (RBD) antibody concentrations before and after two weeks following the two-dose BNT162b2 vaccination were measured using electro chemiluminescence immunoassay system. Results: Before vaccination, the antibody titers of all participants were less than 0.6 U/mL. After two doses of the BNT162b2 vaccine injection in 342 participants (2 excluded), a high seroconversion rate (99.7%) was observed. The average (±standard deviation) serum anti-RBD antibody titers were 2324 ± 1739 U/mL. Antibody levels in females and males were 2443 ± 1833 U/mL and 1908 ± 1287 U/mL, respectively (p = 0.037). Conclusion: In a non-epidemic area, two BNT162b2 doses induced a satisfactory antibody response, and the antibody concentrations in females were higher than in males.

Abstract Background Medication-related osteonecrosis of the jaw (MRONJ), which was first reported as bisphosphonate-related osteonecrosis of the jaw (BRONJ) in bisphosphonate users, is a rare but severe soft and hard tissue disease induced by several types of medications. There has been a deluge of information about MRONJ, such as epidemiology, risk factors, clinical recommendations for dental treatment to prevent it, and treatment strategies in medication-prescribed users. The aim of this study was to comprehensively review recent articles and provide the current scientific information about MRONJ, especially clinical considerations or recommendations for dental treatment to prevent its occurrence. Materials and methods The current literature review was mainly based on 14 systematic reviews with or without meta-analysis, 4 position papers, 1 consensus statement, 1 clinical guideline, and 2 clinical reviews regarding MRONJ after a PubMed database and manual searches according to inclusion and exclusion criteria. Moreover, 53 articles were selected by manual search in regard to all references from selected articles and other articles identified on the PubMed search, irrespective of publication date, and inclusion and exclusion criteria. Results The incidence and prevalence of MRONJ are relatively low, although they are clearly higher in cancer patients receiving high-dose antiresorptive agents or angiogenesis inhibitors rather than osteoporosis patients receiving oral bisphosphonates or denosumab. There are many types of local, systemic, and other risk factors for the development of MRONJ. Clinical recommendations are provided for each clinical situation of patients to prevent MRONJ. There are also treatment strategies for MRONJ in each stage. Conclusions General dentists should perform appropriate dental treatment to prevent MRONJ in the patients prior to or when receiving medications that could induce MRONJ. Moreover, there are treatment strategies for MRONJ in each stage that oral surgeons could follow. Adequate and updated clinical information regarding MRONJ based on scientific data is required whenever possible.

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. [ABSTRACT FROM AUTHOR]