Background
Endoscopic spinal surgery for lumbar foraminal lesions comes to be more popular recently. Bleedings around the foramen during extraforaminal endoscopic approach could make surgical filed turbid and more difficult to perform procedures safely. There were, however, few reports and insufficient information about vascular geometry around the foramen. Purpose: To report lumbar foraminal vascular geometry to help endoscopic spinal surgery underwent well and decrease technical complications by control of bleeding.
Materials and Methods
We reviewed operating record movie clips of extraforaminal approach using biportal endoscopic spine surgery (BESS). Several bleeding foci were matched with previously reported vascular anatomy and vascular geometry was modified to adapt to endoscopic view.
Results
There were four main arterial branches coming out from the lumbar segmental artery. Inferior articular artery, superior articular artery, inter-articular artery and radicular artery could be faced in order during extraforaminal approach using BESS. To escape heavy bleeding from the inferior articular artery and superior articular artery, the dorso-distal surface of transverse process (TP) should be exposed to make a working space without scratching the proximal area of the TP and dorsal surface of the facet. Inter-articular artery was hidden and covered under the capsule overlying superior articular process. Radicular artery was running along the midline of the root under the foraminal ligamentum flavum.
Conclusion
The information of the geometric location of the four arterial branches could help to escape heavy bleeding on extra-foraminal approach and control the bleeding foci to prevent postoperative hematoma.

Background
Lumbar Arthroscopic Spinal Surgery (LASS) has several advantages compared to conventional procedures in terms of improved visual field, versatility with instrumentation, and ease of handling. Purpose: To report the learning curve of LASS for more than 10 years by an experienced spine surgeon.
Materials and Methods
We retrospectively reviewed medical records of the patients who underwent LASS from Dec. 29th, 2017 to April 31st, 2018. Lumbar Arthroscopic Discectomy (LADi), Lumbar Arthroscopic Decompression (LAD), Lumbar Arthroscopic Foraminoplasty (LAF) were performed. Operation time, the amount of bleeding, the length of hospital stay and the degree of postoperative pain were analyzed to evaluate the learning curve.
Results
28 cases (90.3%) showed satisfactory postoperative results. The operation time per segment was 124.2±58.5 minutes (range 45~247). The mean operation time for LADi was 91.4±62.7 minutes (45~247), for LAD was 136.1±53.8 minutes (68~222 minutes) and for LAF was 135.3±50.6 minutes (72~245), and was indicating a declining trend. In the LAF, the slope of the decline of the learning curve was gentle compared to other operations.
Conclusion
The results of short-term follow-up of LASS are excellent, and it is easy to acquire skills in experienced spine surgeon.