Hollow implantsin soft tissues allowing quantitative studies of cells and fluidat the implantinterface AS. Eriksson,L.M. Bjursten,L.E.Ericsonand P. Thomsen Depattmenr of Anatomy, University of Gorhenburg, PO Box 3303 1, S-400 33 Gorhenburg, Sweden Presented at Bioinreracrions ‘87. Cambridge, UK in July 198 7 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA In order to study the early cellular response in the fluid phase found close to implants in soft tissues, an experimental method using a hollow implant was developed. The fluid present in an interior chamber communicating with the exterior of the implant was analysed. Polymorphonuclear granulocytes (PMNGs) were predominant during the study (l-9 days). In titanium implants a slight increase in cell numbers with time was noted, whereas in polytetrafluoroethylene (PTFE) implants, a sharp increase in cell numbers was observed. Preliminary studies showed that sufficient amounts of fluid and cells could be retrieved for analysis of protein composition and inflammatory cell activation. Keywords: Hollow implant, riranium, PTFE, inflammatory cells. fluid phase Implantation of a prosthetic device is used to restore the functional capacity of the patient. Knowledge of the basic biological mechanisms of the healing-in process and of the long-term persistence of different types of implants in tissues is still to a large extent lacking. Implants of non-alloyed titanium have been used successfully by Branemark et al, for the long-term clinical treatment of edentulousness’. These titanium implants become integrated into the jaw bone without any intervening reactive fibrous or inflammatory capsule. In experimental studies in soft tissues, titanium implants are surrounded by less inflammatory cells and by smaller amounts of fibrous tissue than implants of polyacetal and polytetrafluoro- ethylene (PTFE)‘. Nevertheless, insertion of a titanium implant is accompanied by an acute transient inflammatory response, which is less intense than the inflammatory reaction around PTFE implants3. We have earlier suggested that the interaction between an implant and the inflammatory cells present at the site of implantation during the early phase of healing-in is of great importance for the subsequent structural development of the surrounding tissues3*4. Using a new preparation method5 which enables ultrastructural observations of the intact tissue-implant interface leucocytes have been shown to be present during the first week after implantation, not only in the reorganizing surrounding tissue but also in a narrow (1 O-l 00 pm), fluid- containing space, immediately adjacent to the implant surface6. The aim of the present study was to develop a method whereby the cells and fluid present in this space around implants in soft tissues could be sampled and further analysed. This was achieved by creating a hollow implant Correspondence to Dr P. Thomsen. with communication between the outer and the interior surfaces of the implant. EXPERIMENTAL PROCEDURE Animals Adult, male Sprague-Dawley rats, weighing about 250 g and kept according to Good Laboratory Practice (GLP), were used. The rats were anaesthetised by intraperitoneal injection of a mixture of Nembutal, (Mebumal vet@.,ACO, Solna, Sweden, 50 mg/ml), Diazepam, (Stesolid@, Dumex, Copenhagen, Denmark, 5 mg/ml) and saline in a 1 : 2 : 1 volume proportion (0,15 ml/l 00 g body weight). Test chamber In order to sample the exudate close to the surface of a material implanted in vivo, a test chamber was developed (Figures 1 and 2). The upper part of all the chambers was made of non-alloyed titanium. The removable part of the plate portion was made of various materials (in this study titanium and PTFE, Teflon@, DuPont Chemical, USA). All implants were ultrasonically cleaned for 15 min in trichloroethylene once and ethanol twice. The chambers were kept in sterile isotonic saline before insertion. Surgical procedure An about 15 mm long incision was made through the shaved and cleaned abdominal skin (0.1% Jodopax in ethanol, Ferrosan, Malmo, Sweden) and through the ventral layer of the rectus sheath to the right of linea alba. The rectus muscle was divided longitudinally by careful dissection. The peritoneum was separated from the rectus muscle by blunt dissection and the chamber placed with its bottom plate in 0 1988 Butterworth Et Co (Publishers) Ltd. 0142-9812/88/01 OOBB-06$03.00 86 Biomarerials 1988, Vol9 January