Introduction: Surgical methods for degenerative lumbar scoliosis (DLS) range from decompression alone to long corrective fusion. Short fusion is frequently indicated in case that neurological symptoms are predominant rather than those related to spinal deformity. However, there are controversies regarding the postoperative curve progression and additional surgery. The aim of this study was to evaluate the change of spinal alignment and the rate of additional surgery after short fusion for DLS.
Methods: A total of 68 patients who had undergone a short fusion for DLS from 2009 to 2019 were included in this study. DLS was defined as more than 20 degrees of scoliosis in this study. They were 16 men and 53 women with a mean age of 73 years. Mean follow-up period was 4.2 years. Number of fusion segments were one segment in 24, two in 29, and three in 15 patients. Radiographic parameters included coronal Cobb angle, coronal upper and lower intervertebral angle, lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), sagittal vertical axis (SVA), and T1 pelvic angle (TPA). These parameters were evaluated using standing whole spine radiographs preoperatively (pre), immediately after surgery (post), and at the final follow-up (final). The pathologies for additional surgery were also reviewed.
Results: Mean coronal Cobb angle was 26 degrees preoperatively. Forty-nine patients (72%) had less than 30 degrees of scoliosis. Coronal Cobb angle was improved to 18 degrees immediately after surgery, and 23 degrees at the final follow-up. Eleven patients (16%) developed more than 10 degrees of coronal curve progression. Among those, only 3 patients (4.4%) developed more than 20 degrees of curve progression. No patients developed more than 10 degrees of coronal upper and lower intervertebral angle. Also, no remarkable changes were observed in the other angular parameters (pre/post/final): LL (26/31/23 degrees), SS (23/26/23 degrees), PT (24/23/27 degrees), PI (46/47/49 degrees), and TPA (24/21/28 degrees). SVA was 6.7 cm before surgery, 5.5 cm immediately after surgery, and 8.7 cm at the final follow-up. Additional surgeries were required in 10 patients (15%). The pathologies were adjacent segmental disease (ASD) in seven patients (10%), aggravation of spinal alignment in two (2.9%) and infection in one (1.5%). In six of eight patients (75%) who needed additional surgery for ASD, the pathology was radiculopathy due to foraminal stenosis at concave side.
Discussion: The current results showed that residual coronal curve and global sagittal alignment were unlikely to deteriorate after short fusion for DLS. Additional surgery for aggravation of spinal alignment was required in only two patient (2.9% of entire cohort). Neurological deterioration at adjacent segment (10% of entire cohort) predominantly occurred at concave-side neuroforamen. Although neurological deterioration after short fusion for DLS did not frequently occur, concave-side foraminal stenosis adjacent to fusion might be a potential risk for additional surgery. Careful observation of postoperative clinical and radiographic changes might be required.