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Surgical Outcomes Research

Maintaining Lumbar Lordosis With Anterior Single Solid-Rod Instrumentation in Thoracolumbar and Lumbar Adolescent Idiopathic Scoliosis

Sweet, Fred A. MD; Lenke, Lawrence G. MD; Bridwell, Keith H. MD; Blanke, Kathy M. RN

Study Design. A prospective radiographic evaluation of 20 consecutive patients with primary lumbar or thoracolumbar adolescent idiopathic scoliosis who were treated with anterior convex compressive single solid-rod spinal instrumentation and structural titanium mesh (Harms) cages.

Objectives. To evaluate a lordosis-preserving anterior single solid-rod instrumented fusion technique for these specific adolescent idiopathic curves.

Summary of Background Data. Maintaining instrumented segmental lumbar lordosis after anterior fusion and instrumentation for thoracolumbar and lumbar curves has been difficult. Twenty consecutive patients who underwent anterior 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, involving discectomies and anulectomies of all convex discs, structural titanium mesh (Harms) cages placed in the anterior half of all disc spaces below T12, morselized rib autograft packed in all disc spaces to be fused and inside the cages, and anterior single solid-rod (5.0-mm or 5.5-mm diameter) convex compressive spinal instrumentation with appropriate lordotic rod contour and rod rotation as necessary. The anterior rod was placed just posterior to the cages to optimize lordotic contouring of the spine during compression. None of the patients was braced after surgery. The lowest instrumented 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 after surgery, and 2 years after surgery were 48°, 11°, and 12°; 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°, 6° and 6°, respectively. Sagittal measurements before surgery, 1 week after surgery, and 2 years after surgery were: T12–L2: −1°, −6°, and −6°; T12–LIV: −8°, −13°, −9°; T12–S1: −61°, −56°, −60°; and entire instrumented levels: −6°, −9°, and −6°, respectively. Coronal plane correction improved: 75% in the primary Cobb, 66% in the plumb line, 50% in LIV translation, and 80% in LIV tilt. Sagittal plane alignment improved in T12–L2 lordosis (P < 0.01) with preservationof physiologic lordosis in the instrumented levels, T12–LIV, and T12–sacrum. There were no instrumentation failures, pseudarthroses, or reoperations.

Conclusions. Coronal plane correction with preservation of thoracolumbar and lumbar lordosis 2 years after anterior convex compressive spinal instrumentation was accomplished using a lordotically contoured single solid rod with structural cages placed anteriorly in the disc spaces of patients with primary thoracolumbar or lumbar adolescent idiopathic scoliosis.

 

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Spine: 15 August 1999 – Volume 24 – Issue 16 – p 1655