Akinobu Suzuki

Study Design: Retrospective multicenter cohort study.Purpose: This study aimed to evaluate the incidence of cage subsidence and its impact on the clinical outcomes of anterior–posterior spinal fixation (APSF) for osteoporotic vertebral fractures (OVFs). It also aimed to identify the risk factors for cage subsidence.Overview of Literature: The risk factors for cage subsidence after APSF for OVFs remain unclear.Methods: This multicenter retrospective cohort study included patients who underwent combined APSF using an expandable cage system, with a minimum 1-year follow-up at multiple centers. Patients were divided into cage subsidence (n=53) and non-subsidence (n=47) groups. Demographic data, surgery-related factors, and radiographic parameters were analyzed. After univariate analysis of factors associated with cage subsidence, multivariate logistic regression was used to identify related factors.Results: The demographic data showed a significant difference in Hounsfield unit (HU) (102.6±28.3 vs. 80.0±30.6, p=0.005) and endplate injury (p<0.001). Furthermore, 1A1B fixation was significantly more common in the subsidence group (p<0.001). Radiographic data showed significant differences in Δlocal kyphosis (supine-standing) (−7.1°±9.2° vs. −14.6°±11.5°, p=0.001). Multivariate analysis showed that Δlocal kyphosis (supine-standing) (adjusted odds ratio [aOR], 12.8; p=0.010), HU (aOR, 8.1; p=0.033), fixation range (aOR, 8.2; p=0.020), and endplate injury (aOR, 18.8; p=0.011) were significant risk factors for subsidence.Conclusions: Intraoperative endplate injury, low HU (<87.5), short fusion, and preoperative vertebral instability (Δlocal kyphosis [supinestanding] <−14) were identified as risk factors for cage subsidence in APSF. Therefore, extending the fusion levels in patients with low HU values and significant preoperative vertebral instability should be considered to avoid intraoperative endplate injury.

Study Design.: Retrospective cohort study Objective.: This study aimed to evaluate the prevalence of patient-reported bladder dysfunction in individuals with degenerative cervical myelopathy (DCM), its impact on quality of life (QOL), and postoperative bladder function and QOL improvements. Summary of Background Data.: DCM frequently causes bladder dysfunction, in addition to limb neurological deficits, which substantially impair QOL. Although it is well established that posterior decompression surgery improves neurological function, its effect on patient-reported bladder function remains unclear. Methods.: We retrospectively analyzed prospectively collected data from 163 patients who underwent cervical laminoplasty for DCM during 2019–2021. Bladder dysfunction and QOL were assessed using the Japanese Orthopaedic Association Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), particularly its bladder dysfunction (CMEQ-BD) and QOL (CMEQ-QOL) domains. Patients with a preoperative CMEQ-BD score of 20-point increase or 2-year postoperative CMEQ-BD score of ≥90. Results.: Preoperative patient-reported bladder dysfunction was identified in 123 of the 163 patients. Compared with patients without bladder dysfunction, those with bladder dysfunction were significantly older and had worse QOL. Multivariate analysis showed that bladder dysfunction was independently associated with lower preoperative QOL (β=−0.167, P =0.031). At postoperative 2 years, only 27 of the 123 patients (22.0%) experienced postoperative bladder function improvement. No demographic or clinical factors were significantly associated with postoperative bladder function recovery. However, patients with improved bladder function showed significantly greater improvements in neurological function (JOA score, P =0.007) and QOL ( P <0.001) than those without improvement. Conclusions.: Patient-reported bladder dysfunction was highly prevalent in patients with DCM and was independently associated with impaired QOL. However, bladder dysfunction rarely improved postoperatively. These findings suggest that considering bladder dysfunction may be helpful when determining the optimal surgery timing in patients with DCM. Level of Evidence.: Level Ⅲ

Study Design: Multicenter prospective registry study. Objective: To classify patients according to whether they achieved the minimum clinically important difference (MCID) in health-related quality of life (HRQoL) after surgery for metastatic spinal tumors and to identify preoperative factors associated with clinically meaningful improvement. Summary of Background Data: As survival in patients with metastatic spinal tumors continues to improve, evaluating clinically meaningful changes in HRQoL has become increasingly important. However, factors associated with achieving clinically meaningful postoperative improvement remain unclear. Methods: Between 2018 and 2021, 413 patients undergoing surgery for metastatic spinal tumors were prospectively enrolled from 35 centers in Japan. Patients with available preoperative and 6-month postoperative EQ-5D-5L data were included in the MCID analysis (n=171). Patients were classified into the MCID improvement and non-MCID improvement groups according to the previously established MCID threshold for the EQ-5D-5L index. Patient-reported outcomes (PROs), clinical characteristics, and functional measures were compared between groups, and multivariable logistic regression analysis was performed to identify preoperative factors associated with clinically meaningful improvement. Results: Patients in the MCID improvement group demonstrated significantly greater improvements in the EQ-5D-5L index, EQ-VAS, and other PRO measures than those in the non-MCID improvement group. Compared with the non-MCID improvement group, they had poorer baseline HRQoL, poorer functional status, greater pain, and lower independence in activities of daily living. Exploratory multivariable analysis identified lower independence in dressing and greater impairment in the mobility, pain/discomfort, and anxiety/depression domains as candidate factors associated with clinically meaningful improvement. Conclusion: Patients with poorer baseline HRQoL and functional status were more likely to achieve clinically meaningful improvement after surgery for metastatic spinal tumors. These findings suggest that baseline HRQoL should be considered when interpreting postoperative outcomes and counseling patients regarding the expected benefits of surgical treatment.

... Asian Spine Journal 2026;20(4):825-826.

Study Design.: Multicenter prospective cohort study; secondary analysis. Objective.: To evaluate predictors associated with 1-year survival after surgery for spinal metastases by comparing a comprehensive 50-variable deep learning (DL) model with a previously published 5-variable LASSO-based machine learning (ML) model and applying DL-based permutation feature importance as an exploratory analytic lens. Summary of Background Data.: Surgical decision-making for spinal metastases requires reliable survival estimates. Traditional scores such as those of Tokuhashi and Tomita and contemporary tools such as SORG and NESMS support prognostication, but performance and calibration may vary across cohorts. A parsimonious 5-variable JASA ML model is clinically practical, whereas DL may help identify prognostic signals embedded in detailed activities of daily living (ADLs), patient-reported outcomes (PROs), and scoring-system components. Methods.: We analyzed 401 complete-case patients who underwent surgery for spinal metastases at 35 Japanese institutions (2018-2021). A feed-forward neural network incorporating 50 preoperative variables was evaluated using five repeated random 8:2 train-test splits. Accuracy, AUROC, Brier score, and calibration summaries were reported and descriptively compared with the previously published 5-variable LASSO-based ML model. Results.: At 1 year, 269 of 401 patients were alive. The DL model achieved 75.5+/- 3.0% accuracy (95% confidence interval [CI], 71.8%-79.2%), held-out AUROC 0.789 (95% CI, 0.681-0.886), and Brier score 0.214. The ML model achieved 71.8% accuracy (Wilson 95% CI, 67.2%-76.0%) and apparent AUROC 0.762. Because the comparison was descriptive rather than paired, formal statistical superiority was not claimed. DL feature importance highlighted Vitality Index-On and Off Toilet, EQ-5D-5L total score and pain/discomfort, and individual Tokuhashi/Tomita components; the ML-selected Vitality Index-Wake Up item ranked 38th. Conclusions.: The 50-variable DL model provided reasonable prediction and generated clinically plausible feature-importance hypotheses, but it did not demonstrate a clearly meaningful performance advantage over the simpler 5-variable ML model. DL may be most useful for research-based feature discovery and refinement of future parsimonious prognostic tools, whereas validated simple models remain more practical for bedside prognostication. Level of Evidence.: 2

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Dear Editor, We thank Yamaguchi and Jamil for their careful reading of our article ( Hijikata et al. 2025a), which examined the association between occupational testicular radiation exposure among spine surgeons and the sex ratio of their offspring and for their thoughtful methodological and radiation protection perspectives. In our study, exposure was defined according to the type of personal protective equipment (PPE) used during the conception period; specifically, coat-type protectors covering the testes versus apron-type protectors not covering the testes. We observed a higher proportion of female offspring in the apron group than in the coat group. Yamaguchi and Jamil suggested that the observed association may be driven primarily by a lower proportion of female births in the control group rather than by an excess in the exposed group. They further raised concerns about potential selection bias and reverse causation, proposing that fathers who already have daughters may be more likely to adopt coat-type protectors, as well as differential recall, whereby fathers of daughters may report prior protective practices differently.

Purpose Lateral lumbar interbody fusion (LLIF) achieves indirect decompression by restoring disc height; however, excessive cage elevation may increase the risk of adjacent segment disease (ASD). This relationship remains unclear. Therefore, this study aimed to identify ASD risk factors following LLIF by focusing on intervertebral height gain and comparing outcomes of LLIF and decompression using propensity score matching (PSM). Methods Seventy-six patients who underwent single-level LLIF for lumbar stenosis with instability were analyzed to identify ASD-related risk factors. Univariate and multivariate Cox regression analyses were used to determine independent predictors. A receiver-operating characteristic analysis identified the optimal cage elevation threshold. PSM of 69 patients with LLIF and 69 patients with decompression was performed. ASD-free survival was evaluated using a Kaplan–Meier analysis. The LLIF cohort was divided into low and high elevation groups based on a cutoff of 3.7 mm. Results A multivariate analysis identified posterior cage placement (hazard ratio [HR], 1.06; p = 0.032) and greater cage elevation (HR, 1.28; p = 0.012) as independent risk factors. The 5-year ASD-free survival rates were 81.1%, 72.9%, and 46.9% for decompression, low-elevation LLIF, and high-elevation LLIF, respectively. Compared to decompression, high-elevation LLIF significantly increased the ASD risk (HR, 3.81; p < 0.001), but low-elevation LLIF did not (HR, 1.79; p = 0.279). Low-elevation LLIF resulted in greater leg numbness improvement (16.65 vs. 41.90; p = 0.023). Conclusion Excessive intervertebral elevation with LLIF increased the ASD risk. Decompression and LLIF with moderate elevation improved symptoms without a significantly different ASD incidence.