NEW ANTERIOR INSTRUMENTATION FOR THE MANAGEMENT OF THORACOLUMBAR AND LUMBAR SCOLIOSIS - APPLICATION OF THE KANEDA 2-ROD SYSTEM

Study Design. The Kaneda multisegmental instrumentation is a new anter ior two-rod system for the correction of thoracolumbar and lumbar spin e deformities. This System consists of a vertebral plate and two verte bral screws for individual vertebral bodies and two semirigid rods to interconnect the vertebral screws. Clinical results of 25 thoracolumba r and lumbar scoliosis patients treated with this new instrumentation were analyzed. Objectives. To evaluate the efficacy of the new anterio r instrumentation in correction and stabilization of thoracolumbar and lumbar scoliosis. Summary of Background Data. Since Dwyer first intro duced the concept of anterior spinal instrumentation and fusion for sc oliosis, anterior surgery has gradually gained acceptance. In 1976, a useful modification for the anterior spinal instrumentation, which rep ortedly provided means of lordosation and vertebral body derotation, w as described. However, some authors reported a high tendency of the im plant breakage, loss of correction, progression of the kyphosis, and p seudoarthrosis as the major complications. To overcome the disadvantag es of Zielke instrumentation, the authors have developed a new anterio r spinal instrumentation (two-rod system) for the management of thorac olumbar and lumbar scoliosis. Methods. Anterior correction and fusion using Kaneda multisegmental instrumentation was performed in 25 patien ts with thoracolumbar or lumbar scoliosis. The average follow-up perio d was 3 years, 1 month (range, 2 years to 4 years, 7 months). There we re 20 patients with idiopathic scoliosis (13 adolescents and seven adu lts) and five patients with other types of scoliosis, including congen ital and other etiologies. All patients had correction of scoliosis by fusion within the major curve, and for 16 of the 25 patients, the mos t distal end vertebra was not included in the fusion (short fusion). R adiographic evaluations were performed to analyze frontal and sagittal alignments of the spine. Results. The average correction rate of scol iosis was 83%. Over the instrumented levels, the correction rate was 9 0%. Preoperative kyphosis of the instrumented levels of 7 degrees was corrected to 9 degrees of lordosis. Sagittal lordosis of the lumbosacr al area beneath the fused segments averaged 51 degrees before surgery and was reduced to 34 degrees after surgery. The trunk shift was impro ved from 25 mm before surgery to 4 mm at final follow-up evaluation. T he average improvement in the lower end vertebra tilt-angle was 97% in those patients whose lower end vertebra was included in the fusion an d 83% in patients whose lower end vertebra was not included in the fus ion. Apical vertebral rotation showed an average correction rate of 86 %. At final follow-up evaluation, all patients demonstrated solid fusi on without implant-related complications. There was 1.5 degrees of fro ntal plane and 1.5 degrees of sagittal plane correction loss within th e instrumented area at final follow-up evaluation. Conclusions. New an terior two-rod system showed excellent correction of the frontal curva ture and sagittal alignment with extremely high correction capability of rotational deformities. Furthermore, correction of thoracolumbar ky phosis to physiologic lordosis was achieved. This system provides flex ibility of the implant for smooth application to the deformed spine an d overall rigidity to correct the deformity and maintain the fixation without a significant loss of correction or imcomplant failure compare d with conventional one-rod instrumentation systems systems in anterio r scoliosis correction.