• Xuenong Zou, Haisheng Li, Mathias Bünger, Niels Egund, Martin Lind, and Cody Bünger.
• Orthopaedic Research Laboratory and Spine Section, Department of Orthopaedics, Nørrebrogade 44, Building 1A, DK-8000, Aarhus, Denmark. zxnong@hotmail.com
• Spine J. 2004 Jan 1;4(1):99-105.

Background ContextIn preclinical and clinical joint replacement applications, porous tantalum has been shown to be osteoconductive and effective for biological fixation. Relatively little research has been undertaken to investigate the porous tantalum implants for potential application in intervertebral spinal fusion.PurposeThe current study was designed to assess the radiographic and histological performance of porous tantalum and carbon fiber devices in the porcine anterior lumbar interbody fusion (ALIF) model.Study DesignA total of 10 Danish Landrace pigs underwent a three-level anterior intervertebral lumbar arthrodeses at L2-L3, L4-L5 and L6-L7. Each level was randomly allocated to one of three implants: a solid piece of porous tantalum, a porous tantalum ring packed with autograft or a carbon fiber cage, likewise packed with autograft. Two staples for fixation were supplemented in front of implant.MethodsPigs were sacrificed 3 months after operation. Specimens were evaluated by plain radiography, conventional tomography and histology.ResultsBone graft filled into the central hole of the porous tantalum ring was less than that of the carbon fiber cage (p<.001). Radiolucencies around the porous tantalum solid were significantly higher than the carbon fiber cage (p=.02) and were not different between the porous tantalum ring and the carbon fiber cage. The bone volume in the hole of implants, within the pores of the porous tantalum and in the implant interface did not differ between implants. Bone volume in the hole of the porous tantalum ring did not differ from that of the adjacent vertebral bone; however, it was significantly different in the carbon fiber cage and the adjacent vertebral bone (p=.005).ConclusionsIn this porcine ALIF model, the radiographic and histological appearances of the porous tantalum ring were equivalent to those of the carbon fiber cage. The high presence of radiolucencies and fibrous tissue layer at the vertebrae-implant interface suggests that an initial stabilizing biomechanical environment is important in order to achieve bone ingrowth in the interbody fusion devices in this ALIF model.

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