An implant describes any tissue or material that can be placed in a living organism.

Strip-like outer table/diploe grafts are particularly well suited for filling bone defects in the midface. These are preferably harvested from the parietal bone of the skull, as the bone is thickest in this region and has an often desirable convex contour.

The calvaria forms as a type of connective tissue bone through a process of intramembranous ossification. Calvarial bone is characterized by a highly rigid form and a low resorption rate of only 17–19%. Pelvic bone, by way of comparison, is formed by endochondral ossification, which involves preliminary cartilaginous stages, and has a high resorption rate of 60–80%.

Indications for an outer table graft are:

primary reconstruction of the trajectory system of the mid-face (primary osteoplasty of midfacial buttresses), requiring primary autogenous bone grafting to replace lost bone and;

secondary correction of extensive orbital wall defects, especially with associated enophthalmos (retrobulbar, intraorbital grafting).

Grafts must be contoured to the diploe layer of the spongy bone in the underlying bone, before fixation with osteosynthesis techniques. The formation of new bone tissue (early osteogenesis) is activated by surviving osteoblasts in the graft tissue. Mucopolysaccharides in the graft induce the formation of new osteoblasts from un-differentiated mesenchymal cells of the invading host tissue.

The harvest site is readily accessible with a bicoronal incision. Preferably, the parietal bone of the nondominant side of the brain, sufficiently lateral to the sagittal sinus, is used. After forming a periosteal flap, a portion of bone of predetermined size can be elevated using an oscillating saw and chisel.

Septal and auricular cartilage are also important, for example, for reconstruction of the orbital floor, as are facia grafts, for example, of the temporalis muscle.

Preserved fascia lata and pericardium (secured with fibrin adhesive) remain the most commonly used materials for closing smaller and more moderately sized skull base defects due to trauma or tumor. A number of other grafts (costal, bone) are also available.

The advantages of these materials include:

good biocompatibility without graft rejection;

avoidable second surgery;

no extrusion as these implants are replaced by the individual’s own connective tissue.

The disadvantage is the risk of disease infection (e. g., Creutzfeldt-Jakob disease), which cannot be completely ruled out.