In the new textbook OPERATIVE TECHNIQUES IN CRANIOFACIAL SURGERY I wrote a chapter on skull reconstruction entitled ‘Three- Dimensional Implant Reconstruction of the Cranial Vault’. In this chapter I describe my experience of over 25 years of designing and placing computer-generated skull implants for a wide variety of defects.
The use of a computer design process in implants dates back to the 1990s. The easiest type of custom implant to make at that time was for the skull because of its relatively non-complex contours. Patients who had lost their craniotomy flaps from neurosurgery procedures and skull tumors to be resected that had known boundaries for which an immediate skull replacement could be made where the common types of patients treated. Implants at that time were made exclusively of HTR polymer, a unique porous material that had a hydrophilic property. This permitted good tissue ingrowth into the material. Having placed over 75 HTR skull implants I never yet have seen an infection with the material.
Today the computer designing process, like that of 3D CT scans from which they are made, has improved. Scans and implant fits are more accurate and the turn around time from design, fabrication and delivery to surgery is shorter. Newer synthetic materials, such as PEEK and PEKK, are being used. Whether they are superior to HTR polymer can be debated but they are newer synthetic materials.
But one of the basic principles of 3D designed skull implants for reconstructive surgery is that the tissue quality of the recipient site must have good vascularity. Implants work in the skull due to the tremendous blood supply of the overlying scalp and bone. When this is affected by prior irradiation, a history of chronic bone infections or scarred or inadequate scalp coverage, the vascular quality of the tissues and/or available soft tissue coverage must be improved. This need is most commonly met by free tissue transfer techniques which are done first and then followed secondarily by implant placement.
Dr. Barry Eppley
Indianapolis, Indiana