A digital anatomic investigation of the safe triangle areas for L1-5 percutaneous minimally invasive discectomy.

Purpose: To reconstruct the three-dimensional safe triangle areas at L1-5 based on the computed tomography digital data, analyze the safe scopes for the puncture location and angles, and provide anatomic references for percutaneous lumbar discectomy.

Methods: Computed tomography data from patients and control group were imported from the database and anatomical reference parameters were measured in Mimics software. The rebuilt model was rotated clockwise along the M-axis to measure the inscribed circle radius of the safe triangle at different angles. Based on the outer diameter of the largest cannula, the safe angles were calculated. The distances between points on the projection of safe triangle-inscribed circle and the upper lumbar spinous process were measured. Similarly, while the safe triangle was on the left side, the model was contra-rotated to measure all the parameters.

Results: There was no significant difference between the patient and control group in both the least distance between the selected anatomical reference locations and the safe triangle-inscribed circle radius at L4-5. According to the series which had a largest cannula of 2.5 mm, the safe puncture angles increased with the descending disc levels. The optimal angles were 40°-45° for L1-2, 45°-50° for L2-3, 50° for L3-4, and 55° for L4-5 separately. The differences between genders in the distances of paired reference points were significant.

Conclusions: Individual safe localization of the percutaneous puncture could be obtained by analyzing the three-dimensional relationship between the puncture localization and anatomical landmarks.