Histological Processing of CAD/CAM Titanium Scaffold after Long-Term Failure in Cranioplasty

Abstract

Cranioplasty is a frequently performed procedure after craniectomy and includes several techniques with different materials. Due to high overall complication rates, alloplastic implants are removed in many cases. Lack of implant material osseointegration is often assumed as a reason for failure, but no study has proven this in cranioplasty. This study histologically evaluates the osteointegration of a computer-aided design and computer-aided manufacturing (CAD/CAM) titanium scaffold with an open mesh structure used for cranioplasty. A CAD/CAM titanium scaffold was removed due to late soft tissue complications 7.6 years after cranioplasty. The histological analyses involved the preparation of non-decalcified slices from the scaffold’s inner and outer sides as well as a light-microscopic evaluation, including the quantification of the bone that had formed over the years. Within the scaffold pores, vital connective tissue with both blood vessels and nerves was found. Exclusive bone formation only occurred at the edges of the implant, covering 0.21% of the skin-facing outer surface area. The inner scaffold surface, facing towards the brain, did not show any mineralization at all. Although conventional alloplastic materials for cranioplasty reduce surgery time and provide good esthetic results while mechanically protecting the underlying structures, a lack of adequate stimuli could explain the limited bone formation found. CAD/CAM porous titanium scaffolds alone insufficiently osseointegrate in such large bone defects of the skull. Future research should investigate alternative routes that enable long-term osteointegration in order to reduce complication rates after cranioplasty. Opportunities could be found in mechano-biologically optimized scaffolds, material modifications, surface coatings, or other routes to sustain bone formation.

A Comparative Study of Titanium Cranioplasty for Extensive Calvarial Bone Defects

“…The use of titanium cranioplasty is now accepted as an alternative with high biocompatibility, mechanical strength, and infection resistance, which integrates with the bone and provides favorable cosmesis. With advances in 3D printing technologies, the biomechanical properties of the titanium material can be adjusted by altering the surface morphology, such as porosity and pore size, to improve osseointegration between the bone and the implant 15,16 . Compared with the titanium mesh that has been widely inspected in previous studies, few studies have reported experiences regarding the use of 3D-printed material in cranioplasty.…”

“…With advances in 3D printing technologies, the biomechanical properties of the titanium material can be adjusted by altering the surface morphology, such as porosity and pore size, to improve osseointegration between the bone and the implant. 15,16 Compared with the titanium mesh that has been widely inspected in previous studies, few studies have reported experiences regarding the use of 3D-printed material in cranioplasty. Our primary concern was the introduction of a new biomaterial, the SLM-produced titanium alloy scaffold, and its suitability for various clinical applications.…”