Correlation Between Skin-to-Subarachnoid Space Depth in the Lumbar Region Measured by Ultrasound and Needle Insertion Depth

Author: Ahamed M T, et al.

Cureus 17(9): e91826, September 08, 2025. doi:10.7759/cureus.91826

This prospective observational study evaluated the accuracy of ultrasound (USG) in predicting the depth from skin to subarachnoid space (SSD) during lumbar puncture and spinal anesthesia. One hundred adult patients undergoing spinal anesthesia were assessed. The mean SSD measured with ultrasound was 4.51 cm, compared to an actual needle insertion depth of 4.57 cm. A strong positive correlation was observed (r = 0.94, p < 0.001), outperforming traditional predictive methods such as Stocker’s formula (r = 0.86).

These results demonstrate that USG provides highly reliable SSD estimates, improving procedural accuracy and minimizing risks associated with lumbar puncture and spinal anesthesia.

What You Should Know:

  • Ultrasound SSD measurements closely match actual spinal needle insertion depth.

  • Correlation with needle depth was stronger for ultrasound than for Stocker’s formula.

  • Routine use of USG can enhance safety and success in spinal anesthesia.

Thank you to Cureus for allowing us to use this article.

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