Reciprocal Changes in Sagittal Alignment in Adolescent Idiopathic Scoliosis Patients Following Strategic Pedicle Screw Fixation

Abstract

Study DesignRetrospective observational study.PurposeTo analyze the effect of low-density (LD) strategic pedicle screw fixation on the correction of coronal and sagittal parameters in adolescent idiopathic scoliosis (AIS) patients.Overview of LiteratureLD screw fixation achieves favorable coronal correction, but its effect on sagittal parameters is not well established. AIS is often associated with decreased thoracic kyphosis (TK), and the use of multi-level pedicle screws may result in further flattening of the sagittal profile.MethodsA retrospective analysis was performed on 92 patients with AIS to compare coronal and sagittal parameters preoperatively and at 2-year follow-up. All patients underwent posterior correction via LD strategic pedicle screw fixation. Radiographs were analyzed for primary Cobb angle (PCA), coronal imbalance, cervical sagittal angle (CSA), TK, lumbar lordosis (LL), pelvic incidence, pelvic tilt (PT), sacral slope (SS), C7 plumb line, spino-sacral angle, curve flexibility, and screw density.ResultsPCA changed significantly from 57.6°±13.9° to 19°±8.4° (p <0.0001) with 67% correction, where the mean curve flexibility was 41% and screw density was 68%. Regional sagittal parameters did not change significantly, including CSA (from 10.76° to 10.56°, p =0.893), TK (from 24.4° to 22.8°, p =0.145), and LL (from 50.3° to 51.1°, p =0.415). However, subgroup analysis of the hypokyphosis group (<10°) and the hyperkyphosis group (>40°) showed significant correction of TK (p <0.0001 in both). Sacro-pelvic parameters showed a significant decrease of PT and increase of SS, suggesting a reduction in pelvic retroversion SS (from 37° to 40°, p =0.0001) and PT (from 15° to 14°, p =0.025).ConclusionsLD strategic pedicle screw fixation provides favorable coronal correction and improves overall sagittal sacro-pelvic parameters. This technique does not cause significant flattening of TK and results in a favorable restoration of TK in patients with hypokyphosis or hyperkyphosis.

Sagittal Plane Deformities in Children with SMA2 following Posterior Spinal Instrumentation

“…In doing so, we demonstrated that these deformities are relatively common and that they are not associated with changes in lumbar lordosis (Table 6 and Figure 4). Similar changes in sagittal alignment have been described cephalad [33][34][35][36][37][38][39] and/or caudal [40][41][42] to posterior instrumentation in children with adolescent idiopathic scoliosis. However, we are not aware of any other reports describing these changes we have observed in the SMA population.…”

A Retrospective Study of Factors Associated with Restoration of Thoracic Kyphosis in 43 Patients with Adolescent Idiopathic Scoliosis with Lenke Type 1 Curvature

“…Nevertheless, Tao et al [ 18 ] reported that TK increased from before to after surgical correction, although the position of terminal fusion was different [ 18 ]. Similarly, a review of 92 cases by Dumpa et al [ 32 ] showed satisfactory recovery of TK in all groups of studies. The results of the current study showed that TK increased in comparison with preoperative and postoperative TK, and the sagittal plane was effectively restored.…”

Sagittal profile modifications in hybrid versus all screw technique in adolescent idiopathic scoliosis

“…In contrast with these statements, in a recent retrospectively observational study, Srikanth Reddy Dumpa et al stated that screw fixation provides favorable coronal correction and improves overall sagittal parameters causing a restoration of TK in patients with hypokyphosis and hyperkyphosis preoperatively 16 .…”

“…Furthermore, the three-dimensional direct segmental derotation of the vertebrae provided by pedicle screws is considered another feature that decreases thoracic kyphosis as Kota Watanabe et al studied in a 3D simulation 27 . In contrast with these statements, in a recent retrospectively observational study, Srikanth Reddy Dumpa et al stated that screw fixation provides favorable coronal correction and improves overall sagittal parameters causing a restoration of TK in patients with hypokyphosis and hyperkyphosis preoperatively 16 .…”

“…For this reason, the superior power of coronal curve correction of this technique has been thought to be at the expense of sagittal balance, leading to a higher decompensation rate. In last years, however, some studies began to deny this statement showing how pedicle screws can be used without flattening the thoracic spine 16 , 17 . Different studies have underlined as the restoration of a proper thoracic kyphosis depends not only on the type of anchor points but also on the applied correction maneuvers and stiffness of the rod.…”