In vivo evaluation of defined polished titanium surfaces to prevent soft tissue adhesion Jessica S. Hayes,* Joanne L. Welton,* Ronald Wieling, R. Geoff Richards AO Research Institute Davos, AO Foundation, Davos, Switzerland Received 28 March 2011; revised 12 July 2011; accepted 12 July 2011 Published online 27 January 2012 in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/jbm.b.31967 Abstract: Soft tissue-implant adhesion is often required for implant integration into the body; however, in some situa- tions, the tissue is required to glide freely over an implant. In the case of distal radius fracture treatment, current litera- ture describes how titanium and its alloys tend to lead to more intra-tendon inflammatory reactions compared with stainless steel. This leads to tendon-implant adhesion and damage possibly causing limited palmar flexion and even tendon rupture. The goal of this study was to analyze the effect of different surface polishings of titanium and titanium molybdenum implants on soft tissue reactions in vivo, with the aim to prevent direct soft tissue adhesion. Using a non- fracture model, to allow for study of the soft-tissue-implant surface interactions only, six surface variants of the same plate design were implanted onto the tibia of 24 New Zea- land white rabbits and left in situ for 12 weeks. Results indi- cate that paste polished commercially pure titanium and titanium molybdenum alloy had the least soft tissue adhe- sion, with the concomitant development of a soft tissue cap- sule. Surface topography did not appear influence the thickness of the connective tissue surrounding the plate. Therefore, suitable surface polishing could be applied to plates for clinical use, where free gliding of tissues is required. V C 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 100B: 611–617, 2012. Key Words: soft tissue capsule, liquid filled void, in vivo, bio- material, soft tissue adhesion How to cite this article: Hayes JS, Welton JL, Wieling R, Richards RG. 2012. In vivo evaluation of defined polished titanium surfaces to prevent soft tissue adhesion. J Biomed Mater Res Part B 2012:100B:611–617. INTRODUCTION Formation of restrictive adhesions surrounding flexor ten- dons is one of the a difficult problem in hand surgery 1,2 and can result in the inflammatory condition, tenosynovitis, and in extreme cases tendon rupture. Lowry et al. 3 suggest that the difficulty in avoiding these complications lies in provid- ing appropriate soft tissue coverage between the plate and the tendons. One of the major identifiable factors contribut- ing to tissue adhesion at the implant interface is implant surface microtopography. 4–6 The two main materials used in internal fixation to date are stainless steel [electropolished stainless steel (EPSS); ISO 5832/1] and commercially pure titanium (cpTi; ISO 5832/2) and its alloys. Thus far, cpTi and its alloys are fabricated for clinics with a ‘‘standard’’ mi- crorough surface finish which has been widely shown to be a major determinant in the extent of bony integration. 4–7 In contrast, EPSS is produced with a smooth mirror-like finish with minimal micro-discontinuities, which generally results in the formation of a very thin fibrous layer surrounding the implant preventing direct bony integration. 4,6,8 It is these differences in microtopography that are believed to be attributable for the significantly higher intra- tendon inflammation observed for cpTi and it alloys compared with steel. Sinicropi et al. 9 describe the effect of distal radius titanium implants on the functioning of exten- sor tendons in the beagle dog. The results show 100% free gliding of tendons over steel implants but only 43% over cpTi and 80% over titanium alloys. Furthermore, an increased occurrence of liquid-filled capsule formation adja- cent to EPSS implant is believed to be attributable to the smooth surface of EPSS. 10 For nonpermanent implants, such as those used in frac- ture fixation the presence of a very thin fibrous tissue inter- face material may be advantageous as it can prevent the complete integration of an implant by bone allowing for eas- ier removal when the purpose of the implant, aiding the fracture repair is complete. 4–6 Importantly, where muscles, tendons, or even nerves are concerned an aseptic, nonad- hering thin fibrous capsule on the soft tissue side of an implant may reduce the chance of these free or gliding tissues adhering to the plate. EPSS has been shown to have the ability to support thin fibrous tissue attachment (with concomitant liquid filled void formation) compared with cpTi and its alloys. Due to titanium and its alloys’ inertness in biological conditions, does not appear to cause metal sensitivity reactions and *J. S. H. and J. L. W. contributed equally to this work Correspondence to: R. G. Richards; e-mail: geoff.richards@aofoundation.org V C 2012 WILEY PERIODICALS, INC. 611