Comparative Analysis of Monoaxial and Polyaxial Pedicle Screws in the Surgical Correction of Adolescent Idiopathic Scoliosis.

Background: Although several biomechanical studies have been reported, few clinical studies have compared the efficacy of monoaxial and polyaxial pedicle screws in the surgical treatment of adolescent idiopathic scoliosis (AIS). This study aims to compare the radiological and clinical outcomes of mono- and polyaxial pedicle screws in the surgical treatment of AIS. Methods: A total of 46 AIS patients who underwent surgery to treat scoliosis using pedicle screw instrumentation (PSI) and rod derotation (RD) were divided into two groups according to the use of pedicle screws: the monoaxial group (n = 23) and polyaxial group (n = 23). Results: The correction rate of the main Cobb's angle was higher in the monoaxial group (70.2%) than in the polyaxial group (65.3%) (p = 0.040). No differences in the rotational correction of the apical vertebra were evident between the two groups. SRS-22 scores showed no significant differences according to the type of pedicle screws used. Conclusions: The use of polyaxial pedicle screws resulted in coronal, sagittal, and rotational correction outcomes comparable to those associated with the use of monoaxial pedicle screws for surgical treatment using PSI and RD to treat moderate cases of AIS.

Rotational Assessment of Thoracolumbar/Lumbar Curves According to Lowest Instrumented Vertebra Level.

Background: It is not clearly defined in the literature how the lowest instrumented vertebra (LIV) selection effects the rotation of lumbar vertebrae at fused and unfused levels in thoracolumbar/lumbar (TL/L) curves. The aim of this study was to evaluate the rotational profile of structural TL/L curves, corrected with rod derotation manoeuvre, according to LIV level. Methods: 82 consecutive AIS patients with structural TL/L curves who were treated with long segment posterior instrumentation and fusion were retrospectively evaluated. Patients were divided into three groups according to LIV level: lower end vertebra (LEV) group (32 patients), LEV-1 group (23 patients) and LEV + 1 group (27 patients). Cobb angles of structural curves, coronal and sagittal balance were evaluated with direct roentgenograms. Rotation of upper end vertebra, apical vertebra, LIV-1, LIV and LIV + 1 was evaluated with computerised tomography. Clinical outcomes were assessed using SRS-22 questionnaire. Results: Mean follow-up time was 31 months (range 24-42 months). Preoperative LIV rotation was measured as 16.03°, 16.08° and 12.68° in LEV, LEV-1 and LEV + 1 groups, which changed postoperatively as 13.36°, 16.52° and 9.74° respectively. Postoperative LIV-1, LIV and LIV + 1 rotation values were significantly higher in LEV-1 group compared to LEV + 1 group. None of the patients developed coronal or sagittal imbalance. No significant differences were observed between the groups in terms of SRS-22 scores. Conclusions: Axial rotation of LIV and vertebrae adjacent to LIV is higher when the fusion is stopped at LEV-1. However, higher rotation does not seem to cause poor radiologic and clinical outcomes in the last follow-up.

Rod derotation and translation techniques provide comparable functional outcomes for surgical correction of adolescent idiopathic scoliosis - A retrospective, cross-sectional study.

OBJECTIVES: To compare the functional outcome of the two most commonly used methods of Adolescence Idiopathic Scoliosis (AIS) correction surgery using rod rotation and translation techniques from a single center in Indonesia. METHOD: We performed retrospective, cross-sectional study of patients with AIS who underwent deformity correction surgery by either technique in Fatmawati General Hospital from January 2016 to March 2018. All patients were asked to complete scoliosis research society (SRS)-22 questionnaire. RESULT: Both methods of surgical correction yielded similar functional outcome as recorded in SRS-22 score, 3.67 for rod derotation technique and 3.44 for translation technique (p = 0.235). CONCLUSION: Both rod derotation and translation technique resulted in equally desirable quality of life for AIS patients, in line with what would be expected from the literatures. Neither technique can be judged superior to the other. Therefore, the decision to use rotation or translation technique, as well as to compliment it with additional correction methods, should be made by the surgeon according to personal preference, experience, and comfort.

Incidence and Radiological Risk Factors of Proximal Junctional Kyphosis in Adolescent Idiopathic Scoliosis Following Pedicle Screw Instrumentation with Rod Derotation and Direct Vertebral Rotation: A Minimum 5-Year Follow-Up Study.

Several studies have reported incidence and risk factors for the development of proximal junctional kyphosis (PJK) in patients with adolescent idiopathic scoliosis (AIS). However, there is little information regarding long-term follow-up after pedicle screw instrumentation (PSI) with rod derotation (RD) and direct vertebral rotation (DVR). Sixty-nine AIS patients who underwent deformity correction using PSI with RD and DVR were retrospectively analyzed in two groups according to the occurrence of PJK, with a minimum five-year follow-up, including a non-PJK group (n = 62) and PJK group (n = 7). Radiological parameters were evaluated at preoperative, postoperative, and last follow-up. Incidence for PJK was 10.1% (7/69 patients), with a mean 9.4-year follow-up period. The thoracolumbar/lumbar curve (TL/L curve) was proportionally higher in the PJK group. The proximal compensatory curve was significantly lower in the PJK group than in the non-PJK group preoperatively (p = 0.027), postoperatively (p = 0.001), and at last follow-up (p = 0.041). The development of PJK was associated with the TL/L curve pattern, lower preoperative proximal compensatory curve, and over-correction of the proximal curve for PSI with RD and DVR. Therefore, careful evaluation of compensatory curves as well as of the main curve is important to prevent the development of PJK in the treatment of AIS.

Convex-Rod Derotation Maneuver on Lenke Type I Adolescent Idiopathic Scoliosis.

BACKGROUND: Convex-rod derotation may have potential advantages for adolescent idiopathic scoliosis (AIS) correction; however, study of this technique has been limited. OBJECTIVE: To compare the radiographic outcomes of Lenke type I AIS patients treated by the convex- or concave-rod derotation maneuvers. METHODS: A retrospective study was designed to compare 2 cohorts, including 81 Lenke type I AIS patients treated with convex-rod derotation (n = 38) or concave-rod derotation (n = 43), between July 2008 and September 2012. All patients had complete clinical records and radiographic data, which were collected and compared between groups. RESULTS: In comparing 9 radiographic parameters, significant differences were found in the incidence of screw misplacement, the postoperative main-curve angle, and the corrective rate between groups. The major-curve angles in both the convex- and the concave-rod derotation groups were corrected from 54.0° ± 10.6° and 53.0° ± 11.1° preoperatively, to 8.5° ± 6.9° and 12.9° ± 6.8° postoperatively, with corrective rates of 85.3% and 76.0%, respectively (P = .001). Final T5-T12 kyphosis and appropriate coronal-to-sagittal balance were achieved in both groups. The incidence of screw misplacement in the convex and concave sides of all patients was 1.8% and 3.7%, respectively (P = .047), and 1.8% and 3.6%, respectively, in the convex- and the concave-rod derotation groups (P = .044). CONCLUSION: Compared with concave-rod derotation, convex-rod derotation can potentially improve the major-curve corrective rate and tends to reduce the risk of pedicle breach in Lenke type I AIS patients.

Correction of Double Thoracic Adolescent Idiopathic Scoliosis Using PedicleScrew Instrumentation: Comparison with Translation and Rod Derotation / 대한정형외과학회잡지

PURPOSE: To compare the results of two different surgical methods (translation vs rod derotation) in a correction of double thoracic adolescent idiopathic scoliosis (AIS) using pedicle screw instrumentation. MATERIALS AND METHODS: Forty-seven patients with double thoracic AIS treated by pedicle screw instrumentation were reviewed retrospectively after a minimum follow-up of 2 years. The patients were divided into two groups; TR group (translation method, n=14) and RD group (rod derotation, n=33). There were no significant differences in the preoperative curve characteristics between the two groups. RESULTS: In the TR group, the preoperative upper thoracic curve of 37+/-4 degrees improved to 24+/-4 degrees (35% correction), and the lower thoracic curve of 52+/-9 degrees improved to 18+/-5 degrees (65% correction). In the RD group, the preoperative upper thoracic curve of 40+/-7 degrees improved to 19+/-7 degrees (51% correction), and the lower thoracic curve of 56+/-12 degrees was improved to 16+/-6 degrees (72% correction). The correction of the upper and lower thoracic curves was significantly better in the RD group (p<0.05). Thoracic sagittal kyphosis was corrected from 21 degrees to 24 degrees in the TR group and from 18 degrees to 26 degrees in the RD group. There was no significant difference in the spinal balance, shoulder height difference, T1 tilt and fusion extent. The operating time and the amount of blood loss was 231 minutes and 2050ml in the TR group and 263 minutes and 3217ml in the RD group, respectively (p<0.05). CONCLUSION: In correcting double thoracic AIS using pedicle screw instrumentation, the rod derotation method showed better correction for the upper and lower thoracic curves. The translation method showed the advantages of easier application, a shorter operation time and less blood loss.

Comparison of Apical Z-axis Derotation between Rod Derotation(RD) and Vertebrae to Rod(VTR) Methods in Idiopathic Thoracic Scoliosis / 대한척추외과학회지

STUDY DESIGN: A prospective study. OBJECTIVE: To compare the derotational effect of the two methods and to determine the effect of the position of axis of the rotation on derotation of the apical vertebrae. SUMMARY OF BACKGROUND DATA: Vertebral derotation about z-axis following a posterior instrumentation and its relation to the position of the rotational axis is still controversial. Rod derotation(RD) method rotates the vertebrae about the axis of the rod curvature located relatively anterior position whereas the vertebrae to rod(VTR) method, reducing the vertebrae to the contoured rod, rotates the vertebrae about the posteriorly located axis. MATERIALS AND METHODS: Eleven consecutive thoracic idiopathic scoliosis subjected to segmental pedicle screw instrumentation were analysed. Six were treated by RD and five by VTR. Average preoperative curve was 46.6 delta in RD and 51 delta in VTR with flexibility of 69% and 71% respectively (p>0.05). Mean preoperative relative apical vertebral rotation(RAVR) measured by computerized tomography were 11.2 delta in RD and 13.8 delta in VTR(p>0.05). RESULTS: Average postoperative curve magnitudes were 11.5 delta in RD and 12 delta in VTR with correction rates of 77% and 74% respectively (p>0.05). Postoperative relative apical vertebral rotation(RAVR) were 3.6 delta in RD and 6.1delta in VTR with correction rates of 68% and 56% respectively (p>0.05). The mean instrumentation time per vertebral segment instrumented was 4.7 minutes in RD and 8.5 minutes in VTR (p<0.05). Screw pullout during operative procedure in 8/51 screws(15%) in VTR and none(0/60) in RD. CONCLUSION: RD and VTR methods were not significantly different, both enabling a significant apical z-axis derotation and frontal curve correction. However, RD was more efficient than VTR with less operative time and intraoperative screw loosening. The position of the axis of rotation did not significantly influence the apical derotation effect of segmental pedicle screw instrumentation.