Comparative Sagittal Plane Correction after Anterior Single Rod versus Dual Rod Instrumentation in Idiopathic Thoracolumbar and Lumbar Scoliosis

Introduction: This study aims to compare the use a single rigid rod system versus a dual rod system in their ability to maintain sagittal lumbar contour. A consecutive series of patients with AIS of the thoracolumbar and lumbar spine were reviewed in 2 centres. One centre exclusively used a dual rod system with morsellized bone graft (DR group: n=47) and the other a single rigid rod (6mm) system with structural rib grafts (SR group: n=48). Sagittal plane radiologic parameters were evaluated before surgery, immediately post-surgery and at the latest follow-up.

Methods: Mean age at surgery (16 years) and mean curve magnitude (52 ) were comparable between the 2 groups. Follow up was for a mean of 46.8 and 38.7 months in the SR and DR groups respectively (minimum 24 months). Spinal fusion rate was 100%. There was no significant change in the lumbar lordosis in both groups before or after surgery (mean angle SR = 41 : DR = 47 ). For the fusion block lordotic angle, 7/48 cases in the SR group had a loss of more than 5 (mean 9.7 ). Only 2/47 cases in the DR group lost more than 5 (mean 9.5). There was no resultant change in the sagittal balance in either groups.

Results: This is the first study to directly compare the ability of 2 anterior implant designs to maintain sagital correction and balance. No loss of correction occured in 85% and 95% of the SR and DR groups respectively. The SR group has a slightly higher risk of loosing fusion block correction, although this did not translate into sagittal imbalance.

Conclusion: Based on this study, the authors feel that both methods are valid, and would recommend that single rod systems be used with structural grafts, while dual rod systems may be particularly useful for large patients.