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How many cases of spinal intramedullary ependymoma surgery are required to achieve stability? - Analysis using X-bar charts

Spinal Cord volume 63, pages 372–376 (2025)Cite this article

Subjects

Abstract

Study design

Retrospective cohort study.

Objectives

To evaluate surgical consistency and clinical outcomes in intramedullary ependymoma (WHO grade II) cases by using X-bar charts as a tool to assess procedural stability.

Setting

The single institution in Japan.

Methods

This study included patients who underwent resection of intramedullary ependymomas between 2001 and 2023. All surgeries were performed by one of five board-certified spine surgeons. Operative time was analyzed for stability using X-bar charts. Neurological outcomes were assessed using the modified McCormick Scale (mMS), and regression analysis was performed to evaluate the relationship between operative time and mMS.

Results

The study included 144 patients (82 men, 62 women; average age 50.3 ± 14.6 years). Tumors were located at cervical (67.4%) or thoracic (32.6%) levels, averaging 3.0 ± 1.2 vertebrae. The surgeon who performed 71 cases was defined as the experienced surgeon, and the other surgeons performed 10–24 cases, respectively. The mean operative time was 380.6 ± 140.7 min, and 135 cases achieved gross total resection. The average follow-up duration was 6.9 ± 3.9 years. X-bar charts showed surgical stability once the average number of cases exceeded 17. No significant correlation was found between operative time and mMS for any surgeon. Perioperative complications were minimal.

Conclusions

X-bar charts are a valuable tool for objectively evaluating surgical stability. In intramedullary ependymoma surgeries, consistency in operative time was achieved after 17 cases, and longer procedures did not adversely affect neurological outcomes. This method could be extended to monitor procedural reliability in other complex surgical interventions.

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Data availability

The datasets generated and/or analyzed during the current study are available from the corresponding author on reasonable request.

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Author information

Authors and Affiliations

  1. Department of Orthopaedic Surgery, Keio University School of Medicine, 35 Shinanomachi, Shinjukuku, Tokyo, 160-8582, Japan

    Narihito Nagoshi, Toshiki Okubo, Masahiro Ozaki, Satoshi Suzuki, Kazuki Takeda, Takahito Iga, Morio Matsumoto, Masaya Nakamura & Kota Watanabe

  2. Biostatistics Unit, Clinical and Translational Research Center, Keio University Hospital, 35 Shinanomachi, Shinjukuku, Tokyo, 160-8582, Japan

    Kengo Nagashima

Authors
  1. Narihito Nagoshi
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  2. Kengo Nagashima
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  3. Toshiki Okubo
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  4. Masahiro Ozaki
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  6. Kazuki Takeda
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  7. Takahito Iga
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Contributions

N.N. and K.N. designed the research, analyzed the data, and wrote the paper; T.O. and M.N. performed data collection; T.O., M.O., S.S., K.T., T.I., M.M., M.N. and K.W. supervised the study; all authors reviewed and approved the manuscript.

Corresponding author

Correspondence to Narihito Nagoshi.

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Competing interests

All authors have no conflict to disclose.

Ethics approval and consent to participate

This study received ethical approval from the institutional review board of the Ethics Committee of the Keio University School of Medicine (20110142). We certify that all applicable institutional regulations concerning the ethical use of human volunteers were followed during the research. Informed consent was obtained from all participants.

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Nagoshi, N., Nagashima, K., Okubo, T. et al. How many cases of spinal intramedullary ependymoma surgery are required to achieve stability? - Analysis using X-bar charts. Spinal Cord 63, 372–376 (2025). https://doi.org/10.1038/s41393-025-01090-0

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