Clinical and Radiological Outcomes of Unilateral Biportal Endoscopic Decompression by 30° Arthroscopy in Lumbar Spinal Stenosis: Minimum 2-Year Follow-up

BACKGROUND: Open microscopic laminectomy has been the standard surgical method for degenerative spinal stenosis without instability till now. However, it is associated with complications such as paraspinal muscle injury, excessive bleeding, and wound infection. Several surgical techniques, including microendoscopic decompression, have been introduced to solve these problems. METHODS: Authors analyzed retrospectively 55 patients presenting with neurological symptoms due to degenerative lumbar spinal stenosis refractory to conservative treatment. Patients with foraminal stenosis requiring foraminal decompression were excluded. Two or three portals were used for each level. One portal was used for viewing purpose and the others for instrument passage. Unilateral laminotomy was followed by bilateral decompression under the view of 30° arthroscopy. Clinical outcomes were evaluated using modified Macnab criteria, Oswestry disability index (ODI), and visual analogue scale (VAS). Postoperative complications were checked during the 2-year follow-up. Plain radiographs before and after surgery were compared to analyze the change of disc height decrement and alignment. RESULTS: ODI scores improved from 67.4 ± 11.5 preoperatively to 19.3 ± 12.1 at 2-year follow-up (p < 0.01). VAS scores of the leg decreased from 7.7 ± 1.5 to 1.7 ± 1.5 at the final follow-up (p < 0.01). Per the modified Macnab criteria, 81% of the patients improved to good/excellent. No cases of infection occurred. The intervertebral angle was significantly reduced from 6.26° ± 3.54° to 5.58° ± 3.23° at 2 years postoperatively (p = 0.027) and the dynamic intervertebral angle changed from 6.54° ± 3.71° to 6.76° ± 3.59°, which was not statistically significant (p = 0.562). No significant change in slippage was observed (3.76% ± 5.01% preoperatively vs. 3.81% ± 5.28% at the final follow-up [p = 0.531]). The dynamic percentage slip did not change significantly, from 2.65% ± 3.37% to 2.76% ± 3.71% (p = 0.985). However, intervertebral distance decreased significantly from 10.43 ± 2.23 mm to 10.0 ± 2.24 mm (p = 0.000). CONCLUSIONS: Full endoscopic decompression using a 30° arthroscopy demonstrated a satisfactory clinical outcome at the 2-year follow-up. This technique reduces wound infection rate and did not bring about postoperative segmental spinal instability. It could be a feasible alternative to conventional open microscopic decompression or fusion surgery for degenerative lumbar spinal stenosis.