Bone compaction enhances implant fixation in a canine gap model

A new bone preparation technique, compaction, has increased fixation of implants inserted with exact-fit or press-fit to bone. Furthermore, a demonstrated spring-back effect of compacted bone might be of potential value in reducing the initial gaps that often exist between clinical inserted implants and bone. However, it is unknown whether the compression and breakage of trabeculae during the compaction procedure results in impaired gap-healing of compacted bone. Therefore, we compared compaction with conventional drilling in a canine gap model. Grit-blasted titanium implants (diameter 6 mm) were bilaterally inserted into cavities initially expanded to 8 mm diameters in the proximal humeri. Each dog served as its own control; thus, one humerus had the implant cavity prepared with compaction, the other with drilling. Eight dogs were euthanized after 2 weeks, and 7 dogs after 4 weeks. Humeri from additional 7 dogs represented time 0. At time 0 a spring-back effect of compacted bone was demonstrated as cavities, initially expanded to 8 mm by compaction, were reduced to a median cavity diameter of 6.6 mm. In contrast, cavities initially expanded to 8 mm by drilling, had a median cavity diameter of 8.0 mm at time 0. Compaction significantly increased all push-out parameters at 2 weeks. Compaction significantly increased peri-implant bone density at 0 and 2 weeks, and bone implant contact at 2 and 4 weeks. The faster mechanical and histological fixation with compaction indicates that the beneficial effect of reduced gap size, as compacted bone springs back, is not eliminated by an impaired gap-healing of compacted bone.