Biportal Endoscopic Decompression of Exiting and Traversing Nerve Roots Through a Single Interlaminar Window Using a Contralateral Approach: Technical Feasibilities and Morphometric Changes of the Lumbar Canal and Foramen.

BACKGROUND: Endoscopic surgery for lumbar stenosis is gaining acceptance because of the minimal muscle damage, short recovery times, reduced blood loss, and good clinical results. We report a novel technique of decompressing contralateral traversing and exiting nerve roots through a single interlaminar window, avoiding separate incision for foraminal decompression with minimal damage to facet joints and comparing morphometric changes after decompression. METHODS: Between March and December 2017, 30 patients were evaluated retrospectively for clinical, radiologic, and morphometric outcomes. Patients with unilateral radiculopathy and magnetic resonance imaging (MRI) showing spinal stenosis at 2 levels (lateral recess and cranial level foraminal compression) were included. Clinical evaluation used a numerical rating scale (NRS) for leg pain and Oswestry Disability Index (ODI) scores, and radiologic evaluation used MRI. For morphometric analysis, the cross-sectional area of the intervertebral foramen (CSA-IVF), spinal canal (CSAC), and facet joint (CSA-FJ) was measured on MRI. RESULTS: Thirty levels were decompressed (no adverse events). NRS leg pain and ODI scores improved from 7.5 ± 0.86 and 67.9 ± 9.7 preoperatively to 1.53 ± 0.86 and 15.7 ± 6.6 at last follow-up, respectively. CSAC improved from 99.34 ± 34.01 to 186.83 ± 41.41, indicating good canal decompression. CSA-IVF improved from 56.40 ± 19.28 to 97.60 ± 28.46, indicating good foraminal decompression. CSA-FJ improved from 231.37 ± 62.53 to 194.96 ± 50.56, indicating good foraminal decompression with less damage to facet joint. Morphometric changes were statistically significant (P < 0.05). CONCLUSIONS: Biportal endoscopic decompression of the lateral recess and cranial foramen through a single interlaminar window can be performed using a contralateral approach. In view of the good clinical and radiologic outcomes of patients, with notable improvements in morphometric measurements at stenosed segments, this surgical technique is worthy of further evaluation and application.