Simultaneous translation on two rods improves the correction and apex translocation in adolescent patients with hypokyphotic scoliosis

OBJECTIVE The objectives of this study were to apply the simultaneous translation on two rods (ST2R) maneuver involving rods contoured with a convexity at the desired thoracic kyphosis (TK) apex level and to assess the effects on the ability to support triplanar deformity corrections, including TK apex improvement, in patients with hypokyphotic adolescent idiopathic scoliosis (AIS). METHODS Using retrospective analysis, the authors examined the digital records that included 2- to 4-week, 1-year, and 2-year postoperative radiographic follow-up data of female hypokyphotic (TK < 20°) AIS patients (Lenke type 1–3) treated with ST2R. The authors assessed the corrections of triplanar deformities by examining the main Cobb angle, TK, rib hump, apical vertebral rotation, Scoliosis Research Society 22-item questionnaire scores, and TK apex translocation. In order to better grasp the potential of ST2R, the outcomes were compared with those of a historical matched case-control cohort treated with a standard rod rotation (RR) maneuver. RESULTS Data were analyzed for 25 AIS patients treated with ST2R and 27 patients treated with RR. The ST2R group had significant improvements in the main Cobb angle and TK, reduction in the rib hump size at each time point, and a final correction rate of 72%. ST2R treatment significantly increased the kyphosis apex by an average of 2.2 levels. The correction rate was higher at each time point in the ST2R group than in the RR group. ST2R engendered favorable TK corrections, although the differences were nonsignificant, at 2 years compared with the RR group (p = 0.056). The TK apex location was significantly improved in the ST2R cohort (p < 0.001). At the 1-month follow-up, hypokyphosis was resolved in 92% of the ST2R cohort compared with 30% of the RR cohort. CONCLUSIONS Resolving hypokyphotic AIS remains challenging. The ST2R technique supported significant triplanar corrections, including TK apex translocation and restoration of hypokyphosis in most patients. Comparisons with the RR cohort require caution because of differences in the implant profile. However, ST2R significantly improved the coronal and sagittal corrections. It also allowed for distribution of correctional forces over two rod implants instead of one, which should decrease the risk of screw pullout and rod flattening. It is hoped that the description here of commercially available reducers used with the authors’ surgical technique will encourage other clinicians to consider using the ST2R technique.

Cobalt-chromium versus titanium alloy rods for correction of adolescent idiopathic scoliosis based on 1-year follow-up: a multicenter randomized controlled clinical trial

OBJECTIVE For instrumented correction surgery for adolescent idiopathic scoliosis (AIS), surgeons are increasingly switching from titanium (Ti) alloy rods to stiffer cobalt-chromium (CoCr) rods. The authors conducted the first multicenter randomized controlled clinical trial to investigate whether these materials affect the outcomes in terms of spine correction and quality of life (QOL). This trial was registered at UMIN Clinical Trials Registry on September 3, 2012, under the identifier UMIN000008838 (level of evidence 1). METHODS Female AIS patients (Lenke types 1–3, patient age 10–19 years) were recruited at 5 Japanese institutions and randomized into two cohorts: 6.0-mm-diameter Ti rods were placed in one group, and 6.0-mm-diameter CoCr rods were placed in the other. Patients were followed up at 2 weeks and 3, 6, and 12 months with radiographic examination to quantify the sagittal and coronal correction (Cobb angle, thoracic kyphosis, rib hump, and apical vertebral rotation). Patients completed questionnaires (Scoliosis Research Society–22r, 12-Item Short-Form Health Survey, and Scoliosis Japanese Questionnaire–27) at 6 and 12 months to assess QOL. RESULTS A total of 69 AIS patients were randomized to the demographically similar Ti (n = 37) or CoCr (n = 32) cohort. Four adverse events were recorded, two in each cohort, but these were not related to the rod material. At the final follow-up, both Ti and CoCr cohorts showed significant improvement in spinal correction, including the Cobb angle, thoracic kyphosis, and rib hump size. The correction rates were 68.4% and 67.1% for the Ti and CoCr cohorts, respectively. No parameters differed significantly between the cohorts at any time. Survey data showed improved but similar outcomes in both cohorts. CONCLUSIONS Both treatments (Ti and CoCr) produced similar results and were efficient in engendering clinically significant spine corrections. Clinical trial registration no.: UMIN000008838 (UMIN Clinical Trials Registry)