Details of a Researcher - Ozaki, Masahiro

Ozaki, Masahiro

写真a

Affiliation: School of Medicine, Department of Orthopaedic Surgery ( Shinanomachi )

Position: Senior Assistant Professor (Non-tenured)/Assistant Professor (Non-tenured)

Scopus Paper Info

Paper Count: 94 Citation Count: 573 h-index: 11

Click to view the Scopus page. The data was downloaded from Scopus API in September 06, 2026, via http://api.elsevier.com and http://www.scopus.com .

Page Top ▲

Books 【 Display / hide 】

In Vivo Imaging Analysis of an Inner Ear Drug Delivery in Mice: Comparison of Inner Ear Drug Concentrations Over Time

Kanzaki S., Shibata S., Nakamura M., Ozaki M., Okano H., Methods in Molecular Biology, 2022

　View Summary

Treatment for inner ear regeneration and protection needs local injection of steroid or new drug for inner ear regeneration into the round window membrane (RWM) in cochlea, but a systemic injection is not available due to its systemic side effects. However, pharmacokinetics of therapeutic agents or steroid locally injected into the inner ear is not well known. Hence, we introduce a new method for the real-time observation of drug delivery in transgenic animals in vivo. We exemplify mice which contain a firefly luciferase (FLuc) gene expression cassette regulated by the murine glial fibrillary acidic protein (GFAP) promoter. Luciferin delivered into the inner ear of those mice reacts with FLuc that is expressed in the GFAP-expressing cells in the cochlear nerve and spiral ganglion, and the resulting bioluminescence is detected by a camera. Using this system, we show the imaging of pharmacokinetic differences between local and systemic (intravenous and subcutaneous) injections of the inner ear.
- Access to Document (DOI)

Page Top ▲

Papers 【 Display / hide 】

Impact of surgeon experience on surgical outcomes after posterior decompression for degenerative cervical myelopathy: A prospective multicenter study

Okubo T., Nagoshi N., Yamane J., Kono H., Kobayashi Y., Yamamoto T., Kitamura K., Ikegami T., Horiuchi Y., Iga T., Takeda K., Ozaki M., Suzuki S., Matsumoto M., Nakamura M., Watanabe K.

Spinal Cord 64 ( 8 ) 678 - 685 2026.08

ISSN 13624393

　View Summary

Study Design: Prospective multicenter cohort study. Objectives: To investigate how surgeon experience influences surgical, radiologic outcomes, and patient-reported outcomes (PROMs) after posterior decompression in patients with degenerative cervical myelopathy (DCM). Setting: The multiple institutions in Japan. Methods: We prospectively enrolled 775 patients with DCM who underwent posterior decompression at 10 academic institutions in Japan. Surgeries were performed by either board-certified spine (BCS) surgeons or non-BCS (NBCS) surgeons under direct BCS supervision. Outcomes included surgical parameters, radiographic findings, physician-reported measures, and PROMs, such as the JOA score, Visual Analog Scale (VAS) for pain, JOACMEQ, and SF-36 scores, assessed preoperatively and at 2 years follow-up. Results: Baseline demographics were comparable between groups, except for a higher prevalence of diabetes in the BCS group (p = 0.044). The NBCS group had longer surgical duration (91.1 ± 33.1 minutes vs. 109.4 ± 51.8 minutes, p < 0.001) and greater blood loss (33.7 ± 56.3 mL vs. 45.9 ± 79.4 mL, p = 0.018), despite fewer operated laminae (4.1 ± 1.1 vs. 3.8 ± 1.2, p < 0.001). Perioperative complication rates and radiographic outcomes at 2 years were similar between groups. Both groups showed significant improvements in JOA scores, VAS, all JOACMEQ domains, and most SF-36 subscales, with no significant differences between groups. Conclusion: Posterior decompression for DCM can achieve favorable results when performed by NBCS surgeons under BCS supervision, with outcomes equivalent to those of BCS surgeons. These findings support the safety and educational value of supervised training in spine surgery.
- Access to Document (DOI)
A Rare Case of Thoracic Spinal Dural Arteriovenous Fistula Emerging Gradually after Lumbar Decompression, Requiring Direct Transection

Nomura T., Okubo T., Nagoshi N., Iga T., Takeda K., Ozaki M., Suzuki S., Watanabe K., Nakamura M.

Spine Surgery and Related Research 10 ( 4 ) 652 - 655 2026.07
- Access to Document (DOI)
Influence of smoking status and cumulative smoking exposure on neurological recovery after surgery for degenerative cervical myelopathy: a prospective multicenter study

Okubo T., Nagoshi N., Yamane J., Kono H., Kobayashi Y., Shibata R., Kitagawa T., Fujiyoshi K., Kitamura K., Iga T., Takeda K., Ozaki M., Suzuki S., Matsumoto M., Nakamura M., Watanabe K.

Spinal Cord 64 ( 7 ) 634 - 642 2026.07

ISSN 13624393

　View Summary

Study design: Prospective multicenter cohort study. Objectives: To evaluate the association of smoking status and cumulative smoking exposure with postoperative neurological outcomes in patients undergoing surgery for degenerative cervical myelopathy (DCM). Setting: Multiple institutions in Japan. Methods: A total of 935 patients with DCM were categorized as non-, past-, or current-smokers. Demographic characteristics, operative variables, and postoperative outcomes, including the Japanese Orthopaedic Association (JOA) score and recovery rate, JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), Short Form-36, visual analog scale, and Neuropathic Pain Symptom Inventory, were evaluated over a 2-year follow-up. Postoperative outcomes were analyzed across smoking categories using general linear models. Among current-smokers, cumulative smoking exposure was quantified using the Brinkman index and examined in relation to postoperative outcomes. Results: Differences in postoperative functional outcomes, including the JOA recovery rate and JOACMEQ upper and lower extremity functions, were observed across smoking categories. In contrast, neurological recovery, health-related quality-of-life measures, pain intensity, and overall neuropathic pain scores were generally comparable between the groups. Among current-smokers, cumulative smoking exposure did not demonstrate a clear association with neurological or functional outcomes; however, exploratory analyses identified differences in improvement in specific neuropathic sensory symptoms. Conclusion: Smoking status was associated with differences in postoperative functional recovery after DCM surgery. In contrast, cumulative smoking exposure among current-smokers showed exploratory associations with specific neuropathic sensory outcomes but not with overall neurological or functional recovery. These findings suggest that smoking status and cumulative exposure may influence different outcome domains, supporting smoking cessation as part of preoperative patient management.
- Access to Document (DOI)
Risk Factors and Clinical Outcomes of Perioperative Complications Following Cervical Spine Surgery

Nagoshi N., Yamane J., Okubo T., Horiuchi Y., Kamata Y., Isogai N., Kono H., Kobayashi Y., Shibata R., Iga T., Takeda K., Ozaki M., Suzuki S., Matsumoto M., Nakamura M., Watanabe K.

Global Spine Journal 16 ( 6 ) 2671 - 2682 2026.07

ISSN 21925682

　View Summary

Study Design: Prospective multicenter cohort study. Objectives: To determine the incidence and risk factors for postoperative complications following cervical spine surgery and to explore their association with long-term clinical outcomes. Methods: A total of 1482 patients with degenerative cervical disorders who underwent surgery at 10 high-volume institutions in Japan were prospectively enrolled. Perioperative complications were defined as events occurring within 30 days postoperatively. Risk factors were analyzed using univariate and logistic regression analyses. Clinical outcomes were assessed using the cervical Japanese Orthopaedic Association (JOA) score and the Physical Component Summary (PCS) of the SF-36 at baseline and 2 years postoperatively. Results: Perioperative complications occurred in 5.5% of patients: segmental motor paralysis (2.3%), neurological deficit (0.6%), dural tear (0.5%), CSF leakage (0.3%), epidural hematoma (0.9%), and surgical site infection (0.8%). Male sex (OR 3.049; 95% CI 1.045-8.929) and posterior fusion (OR 4.016; 95% CI, 1.518-10.620) were significant risk factors for segmental motor paralysis, while respiratory disease (OR 5.500; 95% CI, 1.462-20.694) was associated with surgical site infection. At 2 years, patients with complications showed variable neurological recovery, with many failing to reach the minimum clinically important difference. Conclusions: Male sex, posterior fusion, and respiratory disease were identified as significant risk factors for major complications. Awareness of these factors may support improved surgical planning and perioperative management. However, interpretation of long-term outcomes should be made with caution because of the limited number of cases and potential selection bias associated with incomplete follow-up.
- Access to Document (DOI)
Predictive factors with the growth of remnant tumor after incomplete resection of thoracic dumbbell-shaped schwannomas

Tokunaga K., Nagoshi N., Okubo T., Ozaki M., Suzuki S., Takeda K., Iga T., Matsumoto M., Nakamura M., Watanabe K.

Spinal Cord 64 ( 7 ) 623 - 627 2026.07

ISSN 13624393

　View Summary

Study design: Retrospective cohort study. Objectives: Thoracic dumbbell-shaped schwannomas (DS) often require incomplete resection (IR) because of anatomical constraints. This study aimed to compare outcomes between gross total resection (GTR) and IR and to identify factors associated with postoperative regrowth of remnant tumors after IR. Setting: Single academic institution. Methods: Patients with thoracic DS surgically treated between 2002 and 2021 were retrospectively reviewed. All patients underwent at least two postoperative MRI examinations and were followed for a minimum of 2 years. Patients were classified into GTR and IR groups; IR cases were further divided according to the presence or absence of postoperative tumor regrowth (>2 mm). Clinical variables, surgical factors, remnant margin zone, residual tumor volume, and regrowth direction were analyzed. Residual tumor volume was measured using three-dimensional volumetric analysis. Results: Thirty-eight patients were included (24 GTR, 14 IR). Postoperative improvement in visual analog scale scores was significantly greater in the GTR group. Among IR cases, 7 patients showed postoperative tumor regrowth. No significant differences were observed between regrowth and non-regrowth groups in age, Eden classification, surgical approach, or remnant margin zone. Residual tumor volume was significantly larger in cases with regrowth (p = 0.016). Tumor regrowth predominantly occurred in the extraforaminal direction. Conclusions: In thoracic DS, larger residual tumor volume is associated with postoperative regrowth, possibly reflecting complex segmental vascular anatomy. When safely feasible, GTR remains the preferred strategy to minimize the risk of remnant tumor regrowth.
- Access to Document (DOI)