The Union League Philadelphia, PA April 25 - 26
2013 Organized by:
Steven M. Kurtz, Ph.D. Research Associate Professor, Drexel University Corporate Vice President and Director, Exponent
Sponsored by:
Comparison of BIC and BV/TV values of Titanium coated and un-coated implants in an animal model Prof. Lauweryns, P. (MD, PhD)1; Schaffarczyk, D. (PhD)2; Willems, K. (MD)3 1 Campus Sint-Josef, BE-3800 Sint-Truiden, 2Orthobion GmbH, D-78467 Konstanz, 3Hospital Roeselare, BE-8800 Roeselare
[email protected] Introduction: Polyetheretherketone (PEEK) is a nontoxic, biocompatible but inert polymer. Compared to a well accepted titanium alloys as implant, PEEK materials offer the advantage to have an elastic modulus (5GPa) closer to bone (18GPa) than titanium alloys (110GPa) and a stability to high temperature as well as to chemical and radiation damage. Despite the good mechanical properties, the adhesion of PEEK implants to bone tissue proceeds slowly due to a relatively low biocompatibility: Concerns have been raised about the inertness of PEEK and limited fixation with bone. Implant complications of PEEK cages such as subsidence and cage migration could be observed. Accordingly, increasing efforts have been directed during the past decade to improve the boneimplant interface by coating PEEK implants with a thin film titanium layer (250 nm). A thin film titanium coating with a micro-porous structure provides the implant with better cell adhesion and improved cell (on-) growth. At the same time, its mechanical properties more closely resemble those of healthy bone, and assure X-ray transparency. Methods and Materials: In this study the titanium (Ti) thin film coating was carried out via Ti thin film vacuum deposition (TFVD), which has already been established in the company and has achieved CE market clearance. The surface of PEEK spinal cages is coated with a pure Tilayer in order to enhance its biocompatibility and adhesion to bone tissue. The vacuum deposition method is a low-temperature coating process that forms a dense, uniform and well crystallized Ti-layer without deteriorating the characteristics of the PEEK/implants. In this animal study the efficacy and safety was observed on Ti TFVD coated PEEK OPTIMA LT1 material and was compared to pure PEEK OPTIMA LT 1.
days post-op and as necessary based on following clinical examination. The animal study was done double blinded and comprises 3 sacrifices periods: 6weeks, 12 weeks and 26 weeks. All measurements were done by an independent company and by means of μCT. All statistical analyses have also been done blind by an independent third party reviewer. Results: The samples of uncoated PEEK show lower bone volume and bone characterized by thinner trabeculae and more trabecular space. The samples of Ti TFVD coated PEEK show higher bone volumes and dense bone with thicker trabeculae and less trabecular space.
Control (uncoated PEEK)
Ti TFVD coated PEEK
Pic. 2: Based on μCT-measurements 3D-images of the structural characteristics of the observed bone are created.
The thin film Ti coated samples show almost higher bone volume after 12 weeks compared to the pure PEEK control group. After 26 weeks the bone volume is still higher in the Ti TFVD coated group. BV/TV (%)
50 45 40 35 30 25 20 15
Pic. 1: For evaluation of the coating, sheep have been operated. They have been sacrificed after 6 weeks, 12 weeks and 26 weeks
Under general anesthesia, 2 unicortical defects have been created in both the distal lateral femur and the proximal medial tibia of left and right hind legs. This resulted in 8 defects in each sheep. Cylindrical implants, 12mm (length) x 8mm (diameter) have been placed in the defects followed by routine wound closure and postoperative care. Pain management was routinely established for 7
6 weeks
12 weeks
26 weeks
Ti TFVD
21
45
47
Control
37
29
40
Pic. 3: Ti TFVD coated samples show higher bone volume compared to the pure PEEK control group.
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