Use of domino connector to improve simultaneous correction of combined sagittal and coronal malalignment in adult spinal deformity surgery

Abstract

OBJECTIVE The objective was to compare the radiological and clinical outcomes of two groups of adult spinal deformity (ASD) patients categorized according to the use or not of a side-to-side domino connector (DC) as a corrective tool for malalignment. METHODS This study was a retrospective analysis of a prospective multicentric ASD database. Patients with baseline coronal (C7 to central sacral vertical line [CSVL] > 20 mm) and sagittal (pelvic tilt [PT] > 25 degrees, sagittal vertical axis [SVA] > 5 cm, thoracic kyphosis > 60 degrees, or global tilt [GT] > 25 degrees) malalignment who underwent spinal fusion with pelvic fixation and had at least 2 years of follow-up were included. Patients were classified according to the use of DC. To account for baseline differences, a propensity score-matched (PSM) analysis was conducted, matching patients for preoperative deformity magnitude and surgical invasiveness. Finally, a subanalysis of patients without pedicle subtraction osteotomy (PSO) was performed to evaluate the intrinsic corrective power of the DC. Demographic and surgical data, alignment evolution, complications, and patient-reported outcome measures were compared. RESULTS Of the 224 patients included, the DC group (n = 81) had significantly worse preoperative biplanar malalignment compared to the no-DC group (n = 143), which led to more frequent use of pedicle subtraction osteotomy (47.7% vs 21.0%, p < 0.001). The DC group achieved significantly greater biplanar correction, including C7-CSVL (29 mm vs 18.7 mm, p = 0.007), GT (22.6 degrees vs 12.0 degrees, p = 0.004), and lumbar lordosis (26 degrees vs 17 degrees, p < 0.05). This translated to superior final sagittal alignment at 2 years, with a lower GT (25.1 degrees vs 29.8 degrees, p = 0.009) and greater L1-S1 lordosis (54.9 degrees vs 48.6 degrees, p < 0.001), while final coronal alignment was comparable between groups. These superior outcomes were confirmed in the PSM analysis, where the DC group retained significantly better postoperative sagittal alignment (p < 0.05). These corrective benefits were also observed in the subgroup of patients who did not undergo 3-column osteotomy, where the DC group maintained significantly greater L1-S1 lordosis (55.5 degrees vs 47.3 degrees, p < 0.001) and thoracic kyphosis (43.1 degrees vs 37.0 degrees, p = 0.032). Despite the greater correction, there was no increase in mechanical complications and patient-reported outcome measures were comparable at the final follow-up. CONCLUSIONS The use of DC is associated with greater radiological correction of complex sagittal and coronal deformities, with no apparent increase in overall complications rates. These findings suggest that DC may represent a powerful and safe tool for optimizing biplanar correction in challenging ASD cases.