The Biological Effects of Combining Metals in a Posterior Spinal Implant: In Vivo Model Development Report of the First Two CasesReportar como inadecuado

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Advances in Orthopedic Surgery - Volume 2014 2014, Article ID 761967, 9 pages -

Research Article

Division of Orthopedics, Rady Children’s Hospital-San Diego, 3020 Children’s Way, MC 5054, San Diego, CA 92123, USA

Department of Orthopaedic Surgery, University of California San Diego, San Diego, CA 92103, USA

Department of Pathology, Rady Children’s Hospital San Diego, San Diego, CA 92123, USA

Department of Orthopaedic Surgery, Chonbuk National University Hospital, Jeonbuk 561-712, Republic of Korea

San Diego Center for Spinal Disorders, La Jolla, CA 92037, USA

Received 17 September 2013; Revised 8 January 2014; Accepted 11 January 2014; Published 26 February 2014

Academic Editor: Federico Canavese

Copyright © 2014 Christine L. Farnsworth et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Study Design. Combinations of metal implants stainless steel SS, titanium Ti, and cobalt chrome CC were placed in porcine spines. After 12 months, tissue response and implant corrosion were compared between mixed and single metal junctions. Objective. Model development and an attempt to determine any detriment of combining different metals in posterior spinal instrumentation. Methods. Yucatan mini-pigs underwent instrumentation over five unfused lumbar levels. A SS rod and a Ti rod were secured with Ti and SS pedicle screws, SS and Ti crosslinks, SS and CC sublaminar wires, and Ti sublaminar cable. The resulting 4 SS-SS, 3 Ti-Ti, and 11 connections between dissimilar metals per animal were studied after 12 months using radiographs, gross observation, and histology foreign body reaction FBR, metal particle count, and inflammation analyzed. Results. Two animals had constructs in place for 12 months with no complications. Histology of tissue over SS-SS connections demonstrated 11.1 ± 7.6 FBR cells, 2.1 ± 1.7 metal particles, and moderate to extensive inflammation. Ti-Ti tissue showed 6.3 ± 3.8 FBR cells, 5.2 ± 6.7 particles, and no to extensive inflammation 83% extensive. Tissue over mixed components had 14.1 ± 12.6 FBR cells and 13.4 ± 27.8 particles. Samples surrounding wires-cables versus other combinations demonstrated FBR 12.4 ± 13.5 versus 12.0 ± 9.6 cells, P = 0.96, particles 19.8 ± 32.6 versus 4.3 ± 12.7, P = 0.24, and inflammation 50% versus 75% extensive, P = 0.12. Conclusions. A nonfusion model was developed to study corrosion and analyze biological responses. Although no statistical differences were found in overlying tissue response to single versus mixed metal combinations, galvanic corrosion between differing metals is not ruled out. This pilot study supports further investigation to answer concerns when mixing metals in spinal constructs.

Autor: Christine L. Farnsworth, Peter O. Newton, Eric Breisch, Michael T. Rohmiller, Jung Ryul Kim, and Behrooz A. Akbarnia



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