Abstract
Some surgical strategies can maintain or restore thoracic kyphosis (TK); however, next-generation surgical schemes for adolescent idiopathic scoliosis (AIS) should consider anatomical corrections. A four-dimensional correction could be actively achieved by curving the rod. Thus, anatomically designed rods have been developed as notch-free, pre-bent rods for easier anatomical reconstruction. This study aimed to compare the initial curve corrections obtained using notch-free rods and manually bent, notched rods for the anatomical reconstruction of thoracic AIS. Two consecutive series of 60 patients who underwent anatomical posterior correction for main thoracic AIS curves were prospectively followed up. After multilevel facetectomy, except for the lowest instrumented segment, either notch-free or notched rods were used. Patient demographic data, radiographic measurements, and sagittal rod angles were analyzed within 1 week after surgery. Patients with notch-free rods had significantly higher postoperative TK than patients with notched rods (P < .001), but both groups achieved three-dimensional spinal corrections and significantly increased postoperative rates of patients with T6–T8 TK apex (P = .006 for notch-free rods and P = .008 for notched rods). The rod deformation angle at the concave side was significantly lower in the notch-free rods than in the notched rods (P < .001). The notch-free, pre-bent rod can maintain its curvature, leading to better correction or maintenance of TK after anatomical spinal correction surgery than the conventional notched rod. These results suggest the potential benefits of anatomically designed notch-free, pre-bent rods over conventional, manually bent rods.
Highlights
Some surgical strategies can maintain or restore thoracic kyphosis (TK); next-generation surgical schemes for adolescent idiopathic scoliosis (AIS) should consider anatomical corrections
There was no significant difference in age, sex, curve type, number of instrumented vertebrae, screw density, number of facetectomy levels, or operative time between the groups (Table 1)
The most important findings of the present study were that patients with notch-free, pre-bent rods had a significantly higher postoperative TK than patients with conventional, manually bent, notched rods and that both groups achieved three-dimensional spinal corrections and significantly increased postoperative rates of patients with T6–T8 TK apex
Summary
Some surgical strategies can maintain or restore thoracic kyphosis (TK); next-generation surgical schemes for adolescent idiopathic scoliosis (AIS) should consider anatomical corrections. The apex of the TK is located at T6–T8 in healthy humans[10], the postoperative apex of the TK was almost identical with the apex of the preoperative MT scoliosis in some patients with k yphosis[10] This non-anatomical TK is mainly generated by the rod-bending procedure, in which the configuration of the rods is approximated by rotation on the alignment of scoliosis before performing maneuvers in curve c orrections[9]. From the spatiotemporal point of view, we recently documented that four-dimensional correction could be actively achieved by bending the rod under multilevel facetectomy[9] In this surgical strategy, two rods were bent identically to guide postoperative anatomical TK without reference to the intraoperative coronal alignment of the Scientific Reports | (2021) 11:12622. This medical device, which is the first in the world, has been approved by a national agency in Japan (Fig. 1)
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