The effects of short segment stabilization on sagittal balance parameters and clinical outcomes

Objective: In our study, we aimed to investigate whether there is a correlation between changes in sagittal balance parameters and changes in clinical findings in patients who underwent short-segment stabilization surgery (single- or two-level posterior pedicle screw fixation) due to spinal stenosis and spondylolisthesis. These parameters were measured in the preoperative and postoperative periods. Materials and Methods: Between February 1, 2022, and May 31, 2024, patients who underwent surgery in the Department of Neurosurgery at our hospital were screened through the operating room database. Among these, 54 patients were included in the study based on the following criteria; having a clinical and radiological diagnosis of spinal stenosis and/or spondylolisthesis; undergoing short-segment stabilization surgery for this reason; completing at least 6 months of postoperative follow-up; and having regular access to preoperative and postoperative imaging through the hospital's PACS system. Clinically, the following data were recorded: age, sex, presence of comorbidities, length of hospital stay, operative time, and presence of postoperative complications. In addition, the following parameters were evaluated during the preoperative period, as well as at the postoperative 1st- and 6th-month follow-up visits: presence of lumbago, neurogenic claudication distance, sciatica symptoms, motor strength examination, and visual analogue scale (VAS) pain scores. All clinical data were obtained from the hospital's electronic medical record (epicrisis) system. Radiologically, the following measurements were obtained: • On preoperative standing lateral lumbar spine radiographs: lumbar lordosis, sacral slope, pelvic incidence, and L3, L4, and L5 vertebral incidence angles. • On preoperative computed tomography (CT): pelvic incidence and L3, L4, and L5 vertebral incidence angles. • On postoperative CT scans: pelvic incidence and L3, L4, and L5 vertebral incidence angles. • On standing lateral lumbar spine radiographs obtained shortly after postoperative mobilization; pelvic incidence and L3, L4, and L5 vertebral incidence angles. • On postoperative 1st-month follow-up lateral lumbar spine radiographs: pelvic incidence and L3, L4, and L5 vertebral incidence angles. • On postoperative 6th-month follow-up lateral lumbar spine radiographs: lumbar lordosis, sacral slope, pelvic incidence and L3, L4, and L5 vertebral incidence angles. All radiological measurements were performed independently and blindly by a radiology faculty member who was unaware of the patients' clinical data. Subsequently, the clinical and radiological data of these patients were statistically analyzed and compared. Findings: Among the patients included in this study, 52 (96.3%) had complaints of low back pain and sciatica preoperatively. The number of patients with sciatica decreased to 6 (11.1%) at postoperative 1-month and 7 (12.9%) at postoperative 6-month; these changes were statistically significant (p<0.0001). Neurogenic claudication was present in 49 patients (90.7%) preoperatively, and when assessed by comfortable walking distance, the average distance increased from 122.86 ± 110.91 m preoperatively to 210.83 ± 198.0 m at postoperative 1-month and 158.13 ± 172.25 m at postoperative 6-month (p<0.0001). The mean preoperative VAS score was 8.43 ± 2.03, which showed a significant reduction postoperatively, measured as 0.93 ± 1.99 at postoperative 1-month and 1.15 ± 2.08 at postoperative 6-month (p<0.0001). Regarding radiological parameters: Lumbar lordosis angle: 40.26 ± 11.98° preoperatively and 38.54 ± 11.77° at postoperative 6-month (p=0.453), Pelvic incidence angle: 60.59 ± 15.22° preoperatively and 60.19 ± 14.42° at postoperative 6-month (p=0.823), Sacral slope angle: increased significantly from 30.63 ± 9.85° preoperatively to 34.72 ± 10.92° at postoperative 6-month (p=0.043). Vertebral incidence angles: L3 incidence: 1.20 ± 10.13° preoperatively, 5.26 ± 8.59° at postoperative 1-month and 5.07 ± 9.68° at postoperative 6-month (p<0.05), L4 incidence: 10.07 ± 8.85° preoperatively, 16.52 ± 11.23° at postoperative 1-month and 16.68 ± 11.80° at postoperative 6-month (p<0.01), L5 incidence: 26.28 ± 13.26° preoperatively, 31.11 ± 14.33° at postoperative 1-month and 30.02 ± 14.67° at postoperative 6-month, with no statistically significant difference (p=0.178). Comparison of postoperative CT and mobilization radiographs showed: Pelvic incidence: no significant difference (CT: 56.81 ± 13.14°; radiograph: 59.06 ± 13.99°; p=0.393), L3 incidence: significantly higher on mobilization radiographs (CT: 0.93 ± 5.95°; radiograph: 4.61 ± 8.10°; p=0.008), L4 incidence: also significantly higher on radiographs (p=0.029), L5 incidence: significantly higher on radiographs (p=0.032). Correlation analysis between changes in radiological parameters from preoperative to postoperative 6-month and changes in VAS scores revealed no statistically significant relationships between changes in lumbar lordosis, sacral slope, pelvic incidence, L3, L4, and L5 incidence and changes in VAS scores (all p>0.05). Results: In this study, the significant increases observed in sacral slope and lower lumbar vertebral incidences indicate that the surgery reestablished regional biomechanical balance. However, no significant changes were detected in fixed morphological parameters such as pelvic incidence, suggesting that the surgery provided functional restoration while preserving anatomical integrity. Although the marked decreases in VAS scores confirm the clinical effectiveness of the surgical intervention, no significant correlation was found between these scores and changes in spinopelvic parameters. This finding suggests that pain relief and functional improvement cannot be solely explained by radiological parameters; rather, a combination of factors such as neurological decompression, soft tissue healing, and individual pain perception play a role. Keywords: Stabilization, Sagittal Balance, Vertebral Incidence, Spondylolisthesis, Spinal Stenosis, Degenerative Spine