Comparative Study of Sagittal Spinopelvic Parameters and Clinical Outcomes After Minimally Invasive Versus Open Fusion in Mild Isthmic Lumbar Spondylolisthesis.

STUDY DESIGN: Retrospective comparative study. OBJECTIVE: This study evaluated the radiologic and clinical outcomes of minimally invasive versus open fusion surgery using a computer-assisted image analysis tool. BACKGROUND: Lumbar spondylolisthesis, isthmic in nature, tends to interfere with sagittal balance and results in chronic back pain and disability. Operationally, the primary aim is to correct sagittal imbalance and restore functional stability. METHODS: Patients with single-level mild isthmic lumbar spondylolisthesis who underwent treatment with minimally invasive transforaminal lumbar interbody fusion (MIS-TLIF) or open posterior lumbar fusion were evaluated retrospectively. Sagittal spinopelvic parameters, such as pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), lumbar lordosis (LL), disc height (DH), and spondylolisthesis degree (SD), were measured preoperatively and postoperatively at 3 months with quantitative image-processing software. Functional outcomes were assessed using the Oswestry Disability Index (ODI), and the connection between radiographic and clinical changes was analyzed. RESULTS: Both methods significantly restored PT, SS, LL, DH, and SD (all P=0.021-0.038), without changing PI (P=0.412). Greater restoration of LL and DH was associated with improved ODI scores (r=0.64 and 0.59; P=0.001 and 0.003, respectively). Clinical outcomes were comparable between groups (P=0.284); however, the minimally invasive group demonstrated shorter hospital stay and faster early recovery (P=0.018). Quantitative imaging showed high reproducibility (ICC=0.93). CONCLUSION: Minimally invasive and open fusion methods both restored sagittal spinopelvic parameters and improved functional outcome in mild isthmic spondylolisthesis. Minimally invasive fusion provided similar radiographic correction at decreased perioperative morbidity. Quantitative image-based evaluation offers a consistent method for assessing spinal alignment and improving surgical planning. LEVEL OF EVIDENCE: Level II.