Seiji Ohtori

Study Design: Retrospective cohort study.Purpose: To identify whether the presence and features of epidural metastases are risk factors for metastatic spinal cord compression (MSCC).Overview of Literature: Several factors are associated with the development of MSCC in patients with spinal metastases. However, the relationship between epidural metastasis and the development of MSCC is not well understood.Methods: Among patients with spinal metastases at the spinal cord level treated at a single institution from 2017 to 2023, 191 cases (age: 66.4±12.9 years; sex: 120 male patients) were studied. We defined MSCC as a decrease of one or more grades in the American Spinal Injury Association (ASIA) impairment scale due to spinal metastases. Patients were diagnosed with epidural metastasis at the level of spinal metastasis. When the features of epidural metastases could be evaluated, the epidural spinal cord compression (ESCC) scale and circumferential angle of spinal cord compression (CASCC) were assessed. The risk factors for developing MSCC and high-risk epidural metastases were analyzed.Results: Of the patients with spinal metastases who developed MSCC during follow-up, 97.6% had epidural metastases before the onset of MSCC. Multivariate logistic regression analysis identified the presence of epidural metastasis as an independent risk factor for MSCC. In patients with evaluable epidural metastases, multivariate logistic regression analysis identified the ESCC scale and CASCC as high-risk factors. The cutoffs were determined to be 3 for the ESCC scale and 180° for CASCC.Conclusions: Epidural metastasis was identified as a risk factor for MSCC in patients with spinal metastases. Additionally, epidural metastases in those with an ESCC scale of 3 and a CASCC greater than 180° were categorized as high-risk tumors.

Purpose The epidemiology and treatment pathways of benign bone tumours remain poorly understood. Using the Bone and Soft Tissue Tumor Registry of the Japanese Orthopaedic Association, we aimed to clarify nationwide diagnostic and surgical practices and factors associated with postoperative local recurrence. Methods We retrospectively analysed registry data from 2006 to 2019. Logistic regression models were used for biopsy and surgery, and Cox proportional hazards models for local recurrence. Results We identified 28,075 cases across 19 histological subtypes. Biopsy was performed in 14.9% and surgery in 39.9%. Diagnostic and surgical management varied according to age, anatomical site, and subtype. Local recurrence occurred in 2.4% of surgical cases and was more common in children, cases referred after prior treatment, and specific subtypes, with the strongest association observed for aneurysmal bone cyst. Conclusion These nationwide data provide a benchmark for current clinical practice in benign bone tumours.

Psychological stress affects the immune system and exacerbates autoimmune diseases such as rheumatoid arthritis (RA), but the mechanisms underlying tissue inflammation during remission remain unclear. Here, we show that tube restraint stress exacerbates joint inflammation in a murine arthritis model during remission. This exacerbation required interleukin-6 (IL-6) produced by brown adipose tissue (BAT) following sympathetic activation. Fibroblast-like synoviocytes expressing the IL-6 receptor subunit gp130 were critical mediators, as IL-6 stimulated these cells to produce the neutrophil chemoattractant CXCL1. Pharmacological blockade of the β3-adrenergic receptor significantly attenuated stress-induced arthritis flares. In patients with RA, carriers of the hypofunctional Trp64Arg variant of ADRB3 showed no positive correlation between psychological stress and disease activity, whereas noncarriers did. These findings identify a BAT–IL-6–fibroblast axis that reactivates inflammatory memory in arthritis and suggest that targeting stress-responsive pathways may provide a complementary therapeutic strategy alongside current RA treatments without broadly suppressing systemic immunity.

Background: MRI T2 mapping provides quantitative information on muscle tissue properties without ionizing radiation. We investigated whether preoperative paravertebral muscle T2 relaxation time was associated with early clinical improvement after decompression for lumbar spinal stenosis.Methods: This retrospective cohort study included 78 consecutive patients who underwent decompression without fusion between April 2020 and April 2024. Preoperative imaging at L4/5 included T2 relaxation times of the paravertebral and psoas major muscles, CT number, CT-derived cross-sectional area, and MRI fat infiltration grade. The primary outcome was improvement in the Japanese Orthopaedic Association (JOA) score at 3 months. Secondary outcomes included improvements in numeric rating scale scores for leg pain and low back pain. Associations were examined using Spearman correlation and multivariable linear regression adjusted for age, sex, the corresponding baseline outcome score, and multilevel decompression. A sensitivity analysis additionally adjusted for whether L4/5 was included in the decompression. Secondary analyses were exploratory.Results: Higher paravertebral muscle T2 relaxation time was associated with less JOA score improvement (Spearman ρ = -0.521; p < 0.001). This association remained after adjustment (regression coefficient per millisecond [β] = -0.130; 95% confidence interval [CI], -0.195 to -0.065; p < 0.001). Additional adjustment for L4/5 inclusion yielded a similar estimate (β = -0.129; 95% CI, -0.201 to -0.056; p < 0.001). In secondary adjusted analyses, higher paravertebral muscle T2 relaxation time was associated with less leg pain improvement (β = -0.050; 95% CI, -0.098 to -0.001; p = 0.047), but not with low back pain improvement (p = 0.357). Higher psoas major T2 relaxation time was also associated with less JOA score improvement in a separate adjusted model (β = -0.109; 95% CI, -0.203 to -0.016; p = 0.023).Conclusions: Preoperative paravertebral muscle T2 relaxation time was associated with 3-month JOA score improvement after lumbar decompression, with a consistent association after adjustment for clinical and surgical factors. T2 mapping may complement preoperative assessment by providing radiation-free quantitative information on muscle condition relevant to early postoperative recovery.

Background: Conventional safe zones are defined by the proximity of acetabular cup screws to intrapelvic vessels; however, this relationship varies among individuals. This study aimed to define the intraosseous safe zone in which the screws remain entirely within bone without penetrating the medial wall. Methods: Three-dimensional computed tomography data for 30 hips of female patients with normal acetabular morphology were analyzed. A hemispherical cup was positioned virtually, and screw trajectories were evaluated in 24 directions using a clock-face coordinate system referenced to the ipsilateral anterior superior iliac spine. Bone thickness was measured in each direction, and intraosseous safe zones were defined for screw lengths of 15, 20, 25, 30, 40, and 50 mm. Heatmaps were generated to visualize the distribution of safe regions, and the angular range in which screws remained intraosseous in all cases was determined. Results: The median patient age was 50.1 years. The intraosseous safe zone was consistently located in the posterosuperior region for all screw lengths. The extent of the safe zone significantly decreased as the screw length increased (p < 0.01), whereas shorter screws expanded the safe zone toward the posteroinferior region. The angular range of the intraosseous safe zone was consistently the greatest at the 11 and 11:30 o’clock positions for 15, 20, and 25 mm screws. Conclusions: The findings provide a useful framework for preoperative planning and conceptualizing safe screw trajectories in total hip arthroplasty. Clinical Relevance: Directing screws toward the posterosuperior acetabulum, particularly around the 11 o’clock region, may enhance safety by maintaining intraosseous fixation and avoiding intrapelvic neurovascular injury. Shorter screws may expand safe fixation options toward the posteroinferior region.

Study Design.: Retrospective single-center cohort study. Objective.: To determine whether baseline modified Lenke classification (MLC), assessed from standing whole-spine radiographs, stratifies brace initiation risk and longitudinal Cobb-angle trajectories in female patients with adolescent idiopathic scoliosis (AIS) before reaching the conventional bracing threshold. Summary of Background Data.: AIS progression is heterogeneous. Baseline Cobb angle and skeletal maturity are established risk factors, but whether simple baseline curve-pattern classification adds risk-stratification information during nonoperative follow-up remains unclear. Methods.: We included female AIS patients aged 10 to P =0.002) and reduced AICc, although BIC increased. At baseline Cobb 20°, adjusted 2-year risk ranged from 23.3% in MLC 1 to 55.9% in MLC 4. Longitudinal Cobb-angle trajectories differed according to MLC. Conclusion.: Baseline MLC may provide complementary information for stratifying brace-initiation risk and longitudinal Cobb-angle trajectories before the conventional bracing threshold.