In vivo evaluation of the effect of intramedullary nail microtopography on the development of local infection in rabbits.
OBJECTIVE
Fractures of the tibia and femoral diaphysis are commonly repaired by intramedullary (IM) nails, which are currently composed of either electropolished stainless steel (EPSS) or standard, non-polished titanium-aluminum-niobium (TAN). Once the fracture has fully healed, removal of IM nails is common, but the strong adhesion of bone to standard TAN complicates removal. Polishing the surface of TAN IM nails has been shown to reduce bony adhesion and ease implant removal without compromising fixation. Polished TAN nails are, therefore, expected to have significant clinical benefit in situations where the device is to be removed. The aim of the present study was to determine the effect of polishing TAN IM nails on susceptibility to infection in an animal model.


METHODS
Solid IM nails (Synthes, Betlach, Switzerland) composed of standard TAN were compared with polished equivalents and also to clinically available EPSS nails. The surface chemical and topographical properties of the materials were assessed by X-ray photon spectroscopy (XPS), white light profilometry, and scanning electron microscopy (SEM). An in vivo infection study was performed using a clinical isolate of Staphylococcus aureus that was characterized with respect to various virulence factors.


RESULTS
Polishing TAN IM nails caused no significant change to the chemistry of the nails, but the topography of the polished TAN nails was significantly smoother than standard TAN nails. In the infection study, the rank order based on descending infectious dose 50 (ID(50)) was: standard TAN, polished TAN, and finally EPSS. The ID(50) values did not differ greatly between any of the groups.


CONCLUSIONS
Polishing the surface TAN IM nails was not found to influence the susceptibility to infection in our animal model.
Moriarty
Thomas F
TF
AO Research Institute Davos, AO Foundation, Davos, Switzerland. fintan.moriarty@aofoundation.org
Campoccia
Davide
D
Nees
Stephanie K
SK
Boure
Ludovic P
LP
Richards
Robert G
RG
D000818:Animals; D001858:Bone Nails / Q000009:adverse effects*; D015169:Colony Count, Microbial; D003722:Dental Alloys; D004195:Disease Models, Animal; D005594:Fracture Fixation, Intramedullary / Q000295:instrumentation*; D008297:Male; D008855:Microscopy, Electron, Scanning; D056951:Photoelectron Spectroscopy; D011474:Prosthesis Design; D016459:Prosthesis-Related Infections / Q000382:microbiology*; D011817:Rabbits; D013193:Stainless Steel; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000254:growth & development / Q000472:pathogenicity*; D013499:Surface Properties; D013977:Tibia / Q000601:surgery*; D013997:Time Factors
D003722:Dental Alloys; C516027:titanium-niobium-aluminum alloy; D013193:Stainless Steel