Radiological Assessment of Bilateral Decompression through Unilateral Approach for the Treatment of Lumbar Spinal Canal Stenosis

Abstract

Introduction Various surgical techniques have been introduced to establish less invasive procedure for the treatment of lumbar spinal canal stenosis (LSCS). Bilateral decompression through a unilateral approach (BDUA) is one of those techniques. This retrospective study was designed to evaluate radiological changes of lumbar spinal alignment after BDUA and to compare with those of conventional fenestration. Material and Methods A consecutive 73 patients (53 males, 20 females; mean age, 71yrs.) underwent BDUA from 2004 to 2012 were included in this study and conventional fenestration (CF) group consisted of 25 patients (12 males, 13 females; mean age, 72yrs.) treated from 2000 to 2012 at the same hospital. Mean number of decompressed level were 2.5 in BDUA and 2.0 in CF. To investigate radiological change of lumbar spine, following parameters were measured on X-rays of pre-op, one year (1Y), and two year (2Y) after surgery: Disc angle and ROM of L4–5, Lumbar lordosis (LL, sagittal angle of L1–5), coronal alignment of L4–5, and L1–5. Clinical results were assessed by Japananese Orthopaedic Association Scoring System (JOAS). Results Preoperative disc angle of L4–5 was 7.4 degrees in BDUA and 7.3 degrees in CF and changed to 8.1 degrees, 8.3 degrees at 1Y, 7.6 degrees, 8.8 degrees at 2Y, respectively. A comparison between two groups showed no significant difference at each point. ROM of L4–5 in both group also showed no significant difference at each point; pre-op: 7.3 degrees, 6.9 degrees, 1Y: 6.1 degrees, 6.0 degrees, 2Y: 7.0 degrees, 5.7 degrees. Preoperative LL was 18.7 degrees in BDUA and 21.8 degrees in CF and changed to 19.5 degrees, 23.7 degrees at 1Y, 19.5 degrees, 23.5 degrees at 2Y, respectively. There was no significant difference between two groups at each point. In the coronal plane, L4–5 wedging angle varied from 0 degrees to 7 degrees in BDUA and from 0 degrees to 4 degrees in CF preoperatively. The amount of L4–5 wedging change in two years was 1.4 degrees in BDUA and 1.1 degrees in CF, showing no significant difference. There was no peculiar tendency in coronal change of L4–5 or L1–5 lumbar alignment depending on approach side. JOAS improved significantly after surgery in both group (Recovery rate: 62.5% in BDUA, 56.5% in CF) and was well maintained at 2Y. A comparison of JOAS revealed no significant difference in two groups preoperatively and 2Y; pre-op: 12.7, 2Y: 23.7 in BDUA, pre-op:11.9, 2Y: 21.5 in CF. Conclusions Decompression through unilateral approach has been widely accepted for the treatment of LSCS. This method spares dissection of paraspinal muscle of contralateral side and has an advantage of preservation of contralateral facet joints. On the other hand, especially in multiple decompression, the influence to the muscle balance or to alignment change remains concerns. Current study showed favorable clinical results in both group. There was no particular tendency of alignment change in the coronal plane. These changes seemed to be mainly based on the degeneration process of lumbar spine.