Localization of L5–S1 disc space by utilizing simple on table surface marking in posterior lumbar spine surgery without any radiological assistance: An observational study

Background: Localization of the spinal levels is an important task during any spinal surgery. The purpose of the study is to assess the accuracy and reliability in identifying L5–S1 disc space by surface localization using Venus of dimple as a landmark in posterior spinal surgery without undertaking any radiological assistance. Methodology: We prospectively analyzed 39 patients, who had undergone primary posterior spine surgery, especially for Prolapsed intervertebral disc mostly affecting the lumbosacral region. Following surface marking using Venus of dimple as a landmark, patients were subjected to surgery with or without prior X-ray evaluation solely on surface localization of L5–S1 disc space. Intraoperatively, the accuracy and reliability of the surface marking were determined. Results: Sixty-four percent of the patients had accurate L5–S1 spine level localization utilizing the above clinical palpatory methods, while 23% of the cases identified L5 spine intraoperatively. On analyzing this surface topographical method with that of X-ray in standing position, the sensitivity and specificity came to be 93.3% and 49%, respectively, with a positive predictive value of 77.8%. Conclusion: The method of localization of L5–S1 space described although cannot fully replace the role of fluoroscopic assistance during spinal surgery, still it is an important, simple, and reliable alternative method of localization which demands its application by the spine surgeons, especially in the beginning of their carrier and in certain specific situations.