THE REPEATED SAMPLING BONE CHAMBER - A NEW PERMANENT TITANIUM IMPLANTTO STUDY BONE-GRAFTS IN THE GOAT

We developed a repeated sampling bone chamber (RSBC) and tested its su itability for studying various aspects of the bone allograft incorpora tion process under reproducible nonload-bearing experimental condition s in a large vertebrate, Our chamber is made of commercially pure tita nium and is designed to allow bone or tissue ingrowth into a removable hollow inner core, Three chambers per animal were randomly implanted in the tibias of 10 goats and were harvested every 8 weeks, In experim ent 1, two chambers were filled with a fresh-frozen structural allogra ft or a chip allograft, and one was left empty, In experiment 2, all c hambers were left empty to measure intra-and interanimal variation. Th e results were evaluated by histomorphometry. Clinical results of four growth factor experiments also are presented. Using this model, we co nducted 60 harvest operations (median, 4/animal; range, 2 to 8), In ex periment 1, more: soft tissue ingrowth and osteoclasts were measured i n the chambers with allograft (P < 0.005 and P < 0.03 respectively), B one ingrowth was scant, with no significant differences between chip g raft, structural graft;, and empty control chamber, Thus, the bone gra ft did not show any osteoinductive or osteoconductive properties, Expe riment 2 indicated consistent tissue ingrowth, with greater interanima l variation than variations among the chambers in any goat, Our method forms a means of studying gradual tissue and bone ingrowth th into bo ne grafts, The inherent low amount of bone ingrowth makes this model s uitable for studying bone-inductive substances, Repeated sampling in t he same animals lowered the intersample variability and reduced the nu mber of animals that were required.