The University Hospital Giessen and Marburg in Giessen (Univ.- Prof. Dr. med. Christian Heiß) and in collaboration with the Advanced Ceramics Group, Faculty of Production Engineering, University of Bremen (Prof. Dr.-Ing. Kurosch Rezwan) has developed a novel hydroxyl apatite based screw (HA-Screw) for the treatment of ACL injuries. The screw's properties of enhanced biocompatibility and osteointegration were examined in vitro in Bremen. Nonetheless, the study is investigating the biocompatability and stability of the HA-screw compared with a market leading ploylactate screw (PLA-screw).
28 female Merino sheep of at least 4 years of age were utilized to study and validate the screws. The healing behavior of implants was investigated postoperative at 6 and 52 weeks. 6 weeks postoperatively marks the phase of the maximum conversion, and thus the least stable of the graft implant-bone complex. However, after 52 weeks postoperatively the osteointegration of both HA- and PLA screws marks a solid the implant healing. In order to keep the number as low as possible, the animals were operated on both knees. The first operation is at week 0, and the second 6 weeks prior to euthanasia (46th week), so that the right knee healed for 52 weeks and the left knee for 6 weeks. These sequential operations are selected to reduce the burden of the joint procedures. Each knee joints was analyzed using in vivo DEXA to ensure similarity of bone mineral density prior to surgery. Further, µCT radiological examination of bone-implant interface and resorption degree was carried out ex vivo. Differences in bone tisssue mineralization are in favor of the HA screw. In addition in vivo and ex vivo biomechanical testing was performed showing a comparative stability of the HA screw to market leading PLA screw. Histological evaluation is curently being assessed using Movate Pentachrome staining and will be quantified and statistically analyzed using SPSS program.
The study showed a promising alternative to titan and PLA screws that can maintain stability and has potential to resorb.