Influence of bone marrow on membrane-guided bone regeneration of segmentallong-bone defects in rabbits

Defects 10 mm long were created in long bone in the diaphysis of both radii of 18 rabbits (test and control side). On the test side, ingrowth of bone marrow into the defects was hindered or delayed by: plugging the opening of the cut bone ends with gutta-percha points (n = 7); plugging with Gelfoam (n = 6); or by removing the bone marrow by flushing with saline (n = 5). Th e defects on both test and control side were covered with an expanded polyt etrafluoroethylene membrane, shaped as a tube. Healing was followed with ra diographs for four to five months, after which the animals were killed and ground sections of the areas of the defects were prepared for histological examination. On the control side, nine of 18 animals had complete osseous b ridging of the defect, and a small transverse non-mineralised zone remained in the centre of the healed defect in the other animals. This zone consist ed of loose connective and cartilagenous tissue as well as connective tissu e obviously derived from the outside of the membrane. By preventing-or dela ying the ingrowth of bone marrow we retarded the regeneration of mineralise d bone, particularly in the gutta-percha and flushed bone marrow groups. Th e principle of guided tissue regeneration may be used to achieve regenerati on of extensive long-bone defects. Any attempts to delay or prevent bone ma rrow ingrowth into the defects did retard regeneration of segmental long-bo ne defects.