Correlation of clinical outcome and spinopelvic sagittal alignment after surgical treatment of low-grade isthmic spondylolisthesis.

The aim of this prospective study was to assess the sagittal alignment of the spine and pelvis before and after surgical treatment of isthmic spondylolisthesis with flat sacrum. At the same time, the functional outcome was analyzed and correlation examined. This study comprises analysis of 30 subjects (mean age 43 years) with isthmic spondylolisthesis and an average follow-up of 2.5 years after posterior spinal fusion. Radiological spinopelvic parameters were measured and functional evaluation was made using the Oswestry Disability Index. Significant improvement toward more normal values for PT and SS in relation to PI was observed after surgery. Pelvic incidence was unaffected by surgery. Correction of the spinosacral angle shows that the anterior tilt with anterior sagittal imbalance due to spondylolisthesis may be corrected by reduction and fusion of the slipped level. Functional outcome was satisfactory with a statistically significant difference between preoperative values and final follow-up values. The sub-group of patients with insufficient restoration of sagittal balance parameters had less good outcomes than the others. Surgical management of low- and mid-grade isthmic spondylolisthesis showed good clinical outcome with restoration of correct values for the pelvic position-dependent parameters, i.e., pelvis tilt, sacral slope, C7 plumb line position and SSA.