The Comparison of Rigid and Semi-rigid Rod for the Correctability of the Thoracic Hypokyphosis of the Idiopathic Scoliosis / 대한척추외과학회지

ABSTRACT

STUDY DESIGN: The analysis was based on the sagittal and coronal correction of 64 cases of thoracic hyphokyphosis that were due to idiopathic scoliosis. PURPOSE: We wanted to compare the three pedicle screws and rod systems (using either a semirigid and rigid rod) from the view points of the coronal and sagittal plane correction during the surgical treatment of idiopathic scoliosis. SUMMARY OF LITERATURE REVIEW There haven't been any reports that have compared the differences and their significance between the semirigid and rigid rod systems for correcting the thoracic hypokyphosis of idiopathic scoliosis. MATERIALS AND METHODS: After a minimum follow-up of 1 year, the results of the frontal and sagittal correction of each study group were compared. There were a total of 52 females and 12 males. The mean age at the time of surgical intervention was 16.4 (age range 12~24). CD instrumentation with a rigid stainless steel rod (7 mm in diameter and 1200 N/mm for its stiffness) was used in group I (36 patients), and 4-CI instrumentation with a titanium alloy rod (6.35 mm in diameter and 1200 N/mm for its stiffness) was used in group II (18 patients). Xia instrumentation with a semi-rigid rod (6 mm in diameter and 600 N/mm for its stiffness) was used in group III (10 patients). For all patients undergoing the segmental pedicle screw fixation procedure, pedicle screws were inserted into every vertebra on the concave side, in the end of each vertebra and then alternately in every other vertebra on the convex side. We measured the preoperative and postoperative magnitude of the major and compensatory curves, the thoracic kyphotic angle on the standing radiographs and the flexibility of the curve. We statistically compared the correctability of thoracic kyphotic angle between the rigid and semi-rigid rods. RESULTS: The differences of preoperative and postoperative major curves in groups I, II and III were 47.3 degrees/12.7 degrees, 51.6 degrees/12.3 degrees and 49.6 degrees/13.3 degrees respectively. The thoracic kyphotic angle was 22.6 degrees/26.6 degrees, 22.0 degrees/26.9 degrees and 23.8 degrees/22.8 degrees, respectively. There was no significant difference for the correction of the coronal angle in each group, but groups I and II were superior to group III for the rate of correcting the kyphotic angle. CONCLUSION: The rod should be stiff enough to pull the spine posteromedially when using the derotation technique for the surgical treatment of idiopathic scoliosis.