Editorial in the autumn issue of Spinal Surgery News
The spine represents the most common location for secondary tumors (Fehlings 2016). In the decision for surgical treatment, decompression of spinal structures and subsequent stabilization of the spinal column with implants is essential. The removal of the tumor will be considered in parallel. For pain control and local control of the tumor, supplemental radiation therapy utilizing photons or protons is often applied postoperatively. Recent studies have shown the combination of surgical treatment combined with radiotherapy leads to better clinical outcomes than radiotherapy alone (Fehlings 2016).
In radiation therapy, the presence of metal spinal implants will cause significant artifacts in the dose planning CT images. The artifacts make it much more difficult to delineate anatomic structures during dose planning and require more time to correctly calculate the proper dose distributions. In contrast to metal implants, BlackArmor® material is a nonmetallic, high-strength composite material, made of continuous carbon fibers and embedded in a PEEK-polymer matrix. Due to its radiolucent nature, BlackArmor® material causes only negligible imaging artifacts, thus enabling a precise demarcation of the tumor and planning of the doses in radiation therapy. The time-consuming manual corrections known from metallic implants are obsolete.
During radiation therapy, metal implants will shield remaining tumor cells from the radiation and cause scattered radiation into the surrounding healthy tissue and organs. Therefore, in some cases, patients with metal implants must be excluded from curative proton therapy. In contrast, BlackArmor® Carbon/PEEK implants allow the radiation beam to pass unimpeded through the material into the initially planned tumor tissue, without shielding or beam scattering. This minimizes the risk of a radiation dose that is either too high or too low and thereby protects sensitive tissue. During follow-up control for recurrent disease in peri-implant tissues, which is usually difficult in areas adjacent to metal implants, the nonmetallic BlackArmor® biomaterial also facilitates significantly better diagnostic images (CT and MRI).
New data (Schneider 2016) from the Center for Proton Therapy at Paul Scherrer Institute have shown for the first time that patients with metal implants who were treated with protons have a significantly (p < 0.05) lower overall survival rate (49%) than those without any metal implant (66%). It is currently unclear if this difference originates from metal implants compromising proton radiation or if the more aggressive disease is a cofactor. Radiation studies by Kashua (2016) and Gademann (2017) compared spinal constructs made of titanium versus those made of BlackArmor® Carbon/PEEK material in a radiation-oncology setup. Both groups found significantly reduced artifacts for BlackArmor® material which resulted in a more accurate and homogenous dose planning and subsequent application of the dose with less beam scattering.
Recently published clinical results utilizing BlackArmor® Carbon/PEEK pedicle screws in spinal tumor surgery show comparable results to metal spinal hardware, but with significantly improved imaging characteristics and suitability for radiotherapy (Eicker 2017, Ringel 2017, Choi 2017 and Hartmann 2017).
BlackArmor® Carbon/PEEK material is utilized in CE-marked products since 2000 and obtained FDA clearance in 2005. The material is the result of a unique combination of continuous, high-strength carbon fibers and icotec’s Composite Flow Molding (CFM) process. As such, complex-shaped implants for load-bearing applications like pedicle screws or vertebral body replacements can be made from BlackArmor® material.
References are available upon request.