[A novel trans-muscular approach for microsurgical bilateral decompression via unilateral approach for degenerative lumbar stenosis: a series study].

To compare clinical outcomes of microsurgical bilateral decompression via unilateral approach (MBDU) between trans longissimus and iliocostalis approach, a novel lateral paraspinal approach(LPA), and classic Wiltseapproach for single level degenerative lumbar stenosis. LPA approach was researched by imaging measurement and cadaver anatomy. Retrospective analysis of a total 124 cases(male/female 75/49, aged(55±14) years) received single-level MBDU due to degenerative lumbar stenosis from 2016 to 2018 in Beijing Tiantan Hospital. Patients were categorized into two groups according to spinal canal morphology. Group A: trefoil shape (48), received MBDU via LPA; Group B: round & oval shape (76), received MBDU via Wiltse approach. Clinical parameters, including visual analogue scale (VAS) of pain, OswestryDability Index (ODI), satisfaction rate were assessed before the operation and at the latest follow-up. The internal fixation and intervertebral fusion were evaluated by X-ray and CT.The data were compared with single sample test between the two groups. The feasibility of trans longissimus and iliocostalis approach was proved by imaging measurement and anatomic study. The tube's maximum tilt angle in LPA group was 65°, and it was 40°in Wiltse group. There was no significantly difference in the operating time, bleeding and drainage volume between the two groups((120±27) min vs (115±32) min, (104±31) ml vs (110±41) ml, (50±15) ml vs (47±18) ml, respectively, 1.246,-1.917,1.730,all 0.05). In both groups, VAS and ODI scores significantly improved at the latest follow-up when compared with those before the operation (all 0.05), but those were all comparable between the two groups(all 0.05). The excellent rate of subjective satisfaction for the clinical efficacy in group A and B was 89.6%(43/48) and 86.8%(66/76) respectively (χ(2)=0.208,0.05). LPA approachfor microsurgical bilateral decompression via unilateral approach (MBDU) in degenerative lumbar stenosis is safe and effective, it has advantages in direct vison of contralateral nerve root canal decompression for trefoil shaped spinal canal.