WRITTEN TRANSCRIPT
0:00 Title Page
This video article is a surgical technical note with a case presentation to demonstrate safe ligamentum flavum resection via osteotomy in biportal endoscopic spine surgery (ESS).
0:13 Introduction
Recently, ESS has been employed to address wide range of degenerative spinal diseases because of its minimally invasive characteristics [1.2]. However, beginning endoscopic spinal surgeons may confront few hurdles before performing successful ESS [3]. Safe decompressive laminectomy is the first yet the most crucial step for a successful endoscopic spinal surgery. Quick and safe decompression involving laminectomy followed by flavectomy is a fundamental procedure to expose the targeted lesion.
This technique has already been employed by a number of surgeons, however it has not been elaborated in literature. The authors would like to coin the term, “crescent osteotomy” technique utilizing mallet and chisel during decompression. This technique is a simple and safe technique which allows surgeons to achieve additional laminectomy and easier flavectomy to gain access to the epidural space for further manipulation.
1:08 Importance of Safe Decompression
In addition to easier flavectomy, crescent osteotomy technique also enables surgeons to safely perform 2-piece or en bloc flavectomy. This may minimize incidental iatrogenic dural injury by leaving ligamentum flavum intact as a protective layer during decompression [4]. Furthermore, crescent osteotomy technique makes decompression process more anatomically comprehensive, preventing unnecessary facet violation, especially for beginning endoscopic spinal surgeons.
1:39 Case Presentation
This is a case of 85-year-old male patient with gait disturbance symptom and preoperative evaluation revealed visual analog scale 5 pain in left leg and Frankel scale D.
1:52 Preoperative Magnetic Resonance Imaging
The preoperative magnetic resonance imaging (MRI) showed central stenosis and hypertrophy of ligamentum flavum at L4–5 level.
2:04 Intraoperative Footage
Biportal endoscopic unilateral laminectomy and bilateral decompression from the left side at L4–5 level was performed for this patient.
2:32 Exposure of Spinolaminar Junction
After exposure of spinolaminar junction of L4 vertebra, high speed drill is used to perform laminectomy. The lamina is drilled from spinolaminar junction to medial margin of left inferior articular process of L4 vertebra.
2:51 Midline Cleft of Ligmanetum Flavum
Midline cleft of ligmanetum flavum is identified. This step is crucial in navigating the whole procedure as it serves as an anatomical landmark.
3:30 Chisel and Mallet
After sufficient drilling of lamina, chisel, and mallet is prepared. First, ligamentum flavum is gently detached from the edge of lamina using the tip of a chisel.
3:51 Osteotomy
After the surgeon has secured the position of chisel, the assistant lightly hammers the chisel using mallet. And just before the bony structure breaks off, the surgeon rotates the chisel to perform safe osteotomy. This process is repeated from right superior articular process around the upper lamina to left superior articular process of L5 vertebra. In this video article, a 4-mm wide straight chisel is utilized, however, the dimension and type of chisel can vary depending on surgeon’s preferences.
5:05 Crescent Osteotomy
Due to the distinct crescent-shaped bone chips remaining on the resected ligamentum flavum tissue, the technique is termed 'crescent osteotomy'.
5:24 Access to Epidural Space
The surgeon has now gained access to epidural space in which targeted lesion can be manipulated.
5:34 Postoperative MRI
The postoperative MRI showed sufficient decompressive laminectomy without unnecessary postoperative facet violation on computed tomography scan.
5:46 Operation Summary
The estimated blood loss was 50 mL during a 56-minute operation. The patient was discharged from hospital on postoperative day 4 with visual analog scale 0 pain and recovered to Frankel scale E.
6:05 Conclusion
In conclusion, "crescent ostetotomy" technique using mallet and chisel can be suggested as a feasible option for performing safe laminectomy and flavectomy. Since flavectomy is one of the most common procedures that can cause incidental dural tear during endoscopic spinal surgery [5], this technique can be employed by beginning endoscopic spinal surgeons to minimize unwanted complications including iatrogenic dural tear. Thus, utilizing crescent ostetotomy technique can potentially enhance favorable postoperative clinical outcome in endoscopic spinal surgery.
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