Biomechanical analysis of anterior versus circumferential spinal reconstruction for various anatomic stages of tumor lesions

Study Design. Spinal reconstruction procedures for metastasis were evaluate d biomechanically using human cadaver specimens. Objective. To investigate the stiffness of anterior versus circumferential spinal reconstructions for different anatomic stages of tumor lesions. Summary of Background Data. Metastatic tumors predominantly involve the ver tebral bodies. Although anterior instrumentation and strut grafts provide e xcellent stability, it remains unclear to what extent vertebral destruction requires anterior reconstructions alone versus combined anterior and poste rior procedures. Methods. Ten human cadaveric thoracolumbar spines were used. The L1 vertebr al body and posterior elements were resected sequentially based on Weinstei n's anatomic zone classification for tumor lesions. Anterior reconstruction was performed between T12 and L2 using an iliac strut graft and the Kaneda SR system (AcroMed, Cleveland, OH). For circumferential reconstruction, th e Cotrel-Dubousset hook and rod system was combined with the anterior recon struction procedure. Experimental groups included the intact condition and five reconstruction stages: anterior reconstructions for corpectomy, subtot al and total spondylectomies, and circumferential reconstructions for subto tal and total spondylectomies. Nondestructive biomechanical testing was per formed under four different loading modes. Results. All the reconstruction groups except anterior instrumentation alon e for total spondylectomy returned stiffness to a level equivalent or highe r to that of the intact spine. There were no statistical differences observ ed between anterior and circumferential reconstruction for subtotal spondyl ectomy, Anterior instrumentation alone for total spondylectomy did not rest ore stiffness to the intact level, and demonstrated significantly lower sti ffness than that of circumferential reconstruction. Conclusions, For corpectomy or subtotal spondylectomy, anterior reconstruct ion alone can provide stiffness equivalent to circumferential reconstructio n. However, total spondylectomy significantly reduces the anterior reconstr uction stiffness, suggesting the need for combined anterior and posterior p rocedures.