Determining the porous structure for optimal soft-Tissue ingrowth: An in vivo histological study

Abstract

The success of osseointegrated transcutaneous prostheses depends on a soft-Tissue seal forming at the skin-implant interface in order to prevent infection. Current designs include a flange with drilled holes or a subdermal barrier with a porous coating in an attempt to promote soft-Tissue attachment. However, the soft-Tissue seal is not reliably achieved despite these designs and infection remains a significant problem. This study investigated soft-Tissue integration into fully porous titanium alloy structures with interconnected pores. The study aimed to determine the effect of altering pore and strut size combinations on soft-Tissue ingrowth into porous titanium alloy structures in vivo. It was hypothesized that implants with a more open porous structure with larger pore sizes would increase soft-Tissue ingrowth more than less open porous structures. Porous titanium alloy cylinders were inserted into sheep paparaspinal muscles (n = 6) and left in situ for four weeks. A histological assessment of soft-Tissue ingrowth was performed. Percentage soft-Tissue pore fill, cell nuclei density and blood vessel density were quantified. The results showed that larger pore sizes were supportive of soft-Tissue ingrowth. A structure with a pore size of 700μm and a strut size of 300μm supported revascularisation to the greatest degree. A flange with this structure may be used in future studies of osseointegrated transcutaneous prostheses in order to enhance the soft-Tissue seal.