Long-Term Changes in Sagittal Balance After Microsurgical Decompression of Lumbar Spinal Canal Stenosis in Elderly Patients: A Follow-Up Study for 5-Years After Surgery

Abstract

The purpose of this study is to investigate long-term changes in spinal sagittal balance after microsurgical decompression in lumbar canal stenosis (LCS). Fifty-two patients who underwent microsurgical decompression for symptomatic single level L4/5 spinal canal stenosis at our hospital were included in the study. All patients had standing full spine radiographs taken preoperatively, 1year postoperatively, and 5years postoperatively. Spinal parameters including sagittal balance were measured from the obtained images. First, preoperative parameters were compared with 50 age-matched asymptomatic volunteers. Next, the parameters before and after surgery were compared to examine long-term changes. Sagittal vertical axis (SVA) was significantly increased in the LCS cases compared to the volunteers (P= 0.03). Postoperative lumbar lordosis (LL) was significantly increased (P= 0.03). Postoperative mean SVA decreased but the difference was not significant (P= 0.12). Although there was no correlation between preoperative parameters and the Japanese Orthopedic Association score, postoperative pelvic incidence (PI)-LL and pelvic tilt changes correlated with changes in Japanese Orthopedic Association score (PI-LL; P= 0.0001, pelvic tilt; P= 0.04). However, after 5years of surgery, LL decreased and PI-LL increased (LL; P= 0.08, PI-LL; P= 0.03). Sagittal balance began to deteriorate but was not significant (P= 0.31). At 5years postoperatively, 18 of 52 patients (34.6%) were found to have L3/4 adjacent segment disease. Cases with adjacent segment disease showed significantly worse SVA and PI-LL (SVA; P= 0.01, PI-LL; P < 0.01). In LCS, lumbar kyphosis improves and sagittal balance tends to improve after microsurgical decompression. However, after 5years, adjacent intervertebral degeneration occurs more frequently and sagittal balance begins to deteriorate in about one third of cases.