Distal foundation augmentation enhances the "Bridge" role of single traditional growing rods in the treatment of severe early- onset scoliosis: a retrospective comparative cohort study

Background: Dual traditional growing rod (dTGR) implantation may not always be feasible for patients with severe early-onset scoliosis (EOS). The concave single traditional growing rod (sTGR) can serve as a starting construct. Distal foundation augmentation (DFA) with four pedicle screws with a cross-link can increase the spinal control provided by a dTGR. However, DFA has yet to be used with a sTGR. This study investigated the efficiency of DFA in patients with severe EOS who underwent sTGR implantation.Methods: From 2010 to 2021, 74 consecutive patients with severe EOS (major curve >= 80 degrees) who underwent traditional growing rod implantation (48 sTGR and 26 dTGR) with a minimum 24-month follow-up were recruited. The sTGR cohort was further divided into two groups by whether or not DFA was performed. In our center, patients who were admitted for sTGR implantation after 2018 routinely underwent DFA. The implantation of a dTGR was based on the severity of thoracic torsion and BMI. Baseline clinical characteristics, complications, and radiographic parameters preoperatively, postoperatively, and at the last follow-up before conversion to a dual rod instrumentation were compared between the three groups.Results: There was no significant difference in baseline clinical characteristics between the three groups (P>0.05). Twenty-four patients in the sTGR cohort underwent DFA. There was no significant difference in preoperative radiographic parameters between the DFA and non-DFA group (P>0.05). Compared with the non-DFA group, the DFA group had superior results at the last follow-up in terms of maintaining the correction of the major curve (P=0.001), maximal kyphosis correction (P=0.001), the distance between the C7 plumb line and the central sacral vertical line (P=0.036), and distracting the growing thorax (P=0.032) and trunk (P=0.044). Furthermore, the incidence of implant-related complications (P=0.019), especially at the distal foundation (P=0.033), was significantly lower in the DFA group. There was no significant difference between the DFA and dTGR groups in radiographic outcomes or complications at the final follow-upConclusions: For patients with severe EOS who undergo sTGR implantation, DFA might better maintain the deformity correction, distract the growing spine, preserve balance, and decrease the incidence of implantrelated complications. The efficiency of sTGR with DFA was comparable to that of the gold-standard dTGR treatment. Further multicenter randomized controlled trials are needed for more convincing conclusions.