Maintaining lumbar lordosis with anterior single solid-rod instrumentationin thoracolumbar and lumbar adolescent idiopathic scoliosis

Study Design. A prospective radiographic evaluation of 20 consecutive patie nts with primary lumbar or thoracolumbar adolescent idiopathic scoliosis wh o were treated with anterior convex compressive single solid-rob spinal ins trumentation and structural titanium mesh (Harms) cages. Objectives. To evaluate a lordosis-preserving anterior single solid-rod ins trumented fusion technique for these specific adolescent idiopathic curves. Summary of Background Data. Maintaining instrumented segmental lumbar lordo sis after anterior fusion and instrumentation for thoracolumbar and lumbar curves has been difficult. Twenty consecutive patients who underwent anteri or single solid-rod fusion, aged 18 or younger with a primary thoracolumbar or lumbar curve, were observed for preservation of lordosis for a minimum of 2 years. Methods. All patients underwent an identical anterior surgical technique, i nvolving discectomies and anulectomies of all convex discs, structural tita nium mesh (Harms) cages placed in the anterior half of all disc spaces belo w T12, morselized rib autograft packed in all disc spaces to be fused and i nside the cages, and anterior single solid-rod (5.0-mm or 5.5-mm diameter) convex compressive spinel instrumentation with appropriate lordotic rod con tour and rod relation as necessary. The anterior rod was placed just poster ior to the cages to optimize lordotic contouring of the spine during compre ssion. None of the patients was braced after surgery. The lowest instrument ed vertebrae (LIV) were L2 (n = 3), L3 (n = 15), and L4 (n = 2), typically the lower end vertebra of the Cobb measurement. Results. Measurements for the primary coronal Cobb before surgery, 1 week a fter surgery, and 2 years after surgery were 48 degrees, 11 degrees, and 12 degrees; for C7 plumb line deviation from the midline: 3.6 cm, 1.9 cm, and 1.2 cm; for lowest instrumented vertebra translation: 31 mm, 15 mm, and 15 mm; and for LIV tilt: 29 degrees, 6 degrees and 6 degrees, respectively. S agittal measurements before surgery, 1 week after surgery, and 2 years afte r surgery were: T12-L2: -1 degrees, -6 degrees, and -6 degrees; T12-LIV: -8 degrees, -13 degrees, -9 degrees; T12-S1: -61 degrees, -56 degrees, -60 de grees; and entire instrumented levels: -6 degrees, -9 degrees, and -6 degre es, respectively. Coronal plane correction improved: 75% in the primary Cob b, 66% in the plumb line, 50% in LIV translation, and 80% in LIV tilt. Sagi ttal plane alignment improved in T12-L2 lordosis (P < 0.01) with preservati on of physiologic lordosis in the instrumented levels, T12-LIV, and T12-sac rum. There were no instrumentation failures, pseudarthroses, or reoperation s. Conclusions. Coronal plane correction with preservation of thoracolumbar an d lumbar lordosis 2 years after anterior convex compressive spinal instrume ntation was accomplished using a lordotically contoured single solid rod wi th structural cages placed anteriorly in the disc spaces of patients with p rimary thoracolumbar or lumbar idiopathic scoliosis.