Progressive Changes in Sagittal Contour After Anterior Spinal Fusion With Instrumentation of Different Sizes for Thoracic Adolescent Idiopathic Scoliosis: Is Continued Posterior Spinal Growth an Issue in Skeletally Immature Children?

Abstract Study Design Retrospective analysis of radiographs for a prospective group of 196 adolescent patients with thoracic idiopathic scoliosis after anterior spinal fusion with instrumentation. Objectives To analyze progressive changes in the sagittal profile of immature and mature patients during the first 2 postoperative years. Summary of Background Data In a previous study of similar patients, a flexible 3.2-mm rod construct was used. An additional 15° (average) of kyphosis was seen in 60% of Risser 0 patients. The current patient group had fusion with solid rod (>4.0-mm) instrumentation. Methods All included patients had single anterior rod instrumentation, clinical and radiographic evidence of solid fusion, a minimum follow-up of 2 years, and a coronal progression of ≤5° including adequate biplanar standard radiographs at preoperative, immediate postoperative, and 2-year follow-up visits. Patients were stratified by skeletal maturity and preoperative thoracic kyphosis. Significant sagittal progression was defined as >10°. Results Significant sagittal progression that caused the patient to be hyperkyphotic (T5–T12 > 40°) occurred in 18.37% of the 196 study patients. A total of 55 who were group I Risser 0 at the time of surgery and 141 were group II Risser 1–5. Progression occurred much more frequently in Risser 0 patients who had a preoperative T5–T12 of ≥30° (67.67%) versus Risser 1–5 patients (25.00%). Conclusions Compared with the authors' previous work, solid rod instrumentation (>4.0 mm) for anterior spinal fusion for thoracic scoliosis is better at preventing progressive thoracic kyphosis than the flexible rod (3.2 mm). However, when performing a thoracic anterior spinal instrumented fusion in skeletally immature patients when the preoperative T5–T12 sagittal curve is >30° it is recommended to leave a low normal kyphosis (20°) in the instrumented region of T5–T12.