Effect of grafting technique on the maintenance of coronal and sagittal correction in anterior treatment of scoliosis.

Abstract

A retrospective radiographic study was conducted to analyze 50 consecutive adolescents with thoracolumbar-lumbar scoliosis treated with single solid-rod anterior instrumentation and either rib strut or morsellized interbody bone grafting technique. To evaluate the effect of grafting technique on the maintenance of coronal and sagittal plane correction and alignment and the incidence of pseudarthrosis. Loss of scoliosis correction and progressive kyphosis in the instrumented segment associated with radiographic pseudarthrosis have historically been disadvantages of the anterior technique used to correct thoracolumbar-lumbar scoliosis. All the patients underwent anterior discectomy, spinal fusion, and correction with Texas Scottish Rite Hospital instrumentation, with rib strut grafts used in 18 patients to "prop open" disc spaces below L1 and simple morsellized bone graft used in 32 patients. Most of the patients were instrumented from T11-L3 or T10-L2. Maintenance of coronal and sagittal plane correction and alignment was determined from the preoperative, immediate postoperative, and final follow-up radiographs. Scoliosis correction was 72% immediately after surgery, but with an average 6 degrees loss of correction, it was 61% at follow-up evaluation. Final correction of apical vertebral translation was 69%, and trunk shift was 86%. Ten patients lost more than 10 degrees of scoliosis correction. In the sagittal plane, the instrumented segment was corrected initially from a mean of 3 degrees kyphosis to -1 degrees lordosis, but then had settled to 7 degrees kyphosis at follow-up evaluation. Progressive kyphosis exceeding 10 degrees in the instrumented segment was found in 19 patients. The technique of grafting had no effect on the maintenance of correction or sagittal alignment. Rib strut grafting did demonstrate a decreased incidence of pseudarthrosis, as compared with morsellized grafting (P = 0.029). Not unexpectedly, patients with pseudarthrosis had an increased incidence of correction loss, progressive kyphosis in the instrumented segment, instrumentation failure, and revision surgery, which was required in three cases. Although the rib strut grafting technique improves the pseudarthrosis rate, as compared with morsellized graft, it did not affect the maintenance of correction or sagittal alignment. Adjunctive measures to provide truly structural interbody support (fusion cages, allograft rings, two-rod construct) appear to be required to address the shortcomings of anterior single-rod instrumentation.