Good day. These are my disclosures. Titanium plates and screws are an effective means for cranial bone flap fixation, but they can loosen, resulting in hardware protrusion, cosmetic disfiguration, or pain. Currently available bone cements lack sufficient strength for stand-alone bone flap fixation, and they're not chemically adhesive. TTC-PPS is a novel, bioresorbable bone adhesive. Here, we investigated the use of TTC-PPS for cranial bone flap fixation compared to conventional titanium plates and screws in an ovine craniotomy model. Bilateral parietal trephine craniotomies were performed in 41 female sheep. The bone flaps were secured in one of three manners. In test group 1, the kerf, or the gap between the bone flap edge and the surrounding skull, was completely filled with TTC-PPS. In test group 2, the kerf was half-filled with the experimental bone cement. In the control group, conventional titanium plates and screws were used to secure the flaps. At specific time points, tissues were harvested. All sites were used for mechanical testing or histological examination. The sites were randomly assigned and allocated by permutation. The extent of bone healing, local tissue effects, and remodeling were analyzed using macroscopic observations, histopathology, and histomorphometry. Flap fixation strength was evaluated biomechanically. At necropsy, all craniotomy sites were observed for evidence of flap migration from the original position and hardware loosening. A fixation score of 0 to 4 was assigned. For specimens randomized to biomechanical testing, the push-out performance was evaluated utilizing a tinneous Olsen machine and a 5 kilonewton load cell. Fixation strength was tested to failure. For specimens randomized to histopathology and histomorphometry, samples were prepared and labeled so that the histopathologist was blinded to the treatment group. The control group sites demonstrated significantly greater bone flap movement from the original position than did the T1 and T2 sites. In multiple control group sites, screws had backed out or hardware had migrated. For the T1 and T2 sites, there was no visual evidence of TTCPPS diffusion, disintegration, or breakage. Mean push-out strengths of the bone flaps fixated with the experimental cement exceeded those of the flaps fixated with plates and screws at 12 weeks and 1 year. These differences were statistically significant. The histology results are enumerated here. I'd like to bring your attention to the results at 2 years. There in the control group fixed with plates and screws, the kerfs were completely healed in only 13 of 32 flaps, fibrous tissue-filled, remaining non-fully healed kerfs. In contrast, the flaps fixed with the TTCPPS cement nearly completely osteointegrated, and within the kerfs were signs of replacement of the cement by bone and osteoconduction without signs of cytotoxicity or osteolysis. The histology is shown here. Note on the lower right, a kerf and a control flap fixated with plates and screws with soft tissue still within the kerf at 2 years. Histomorphometry helped quantify the histology. Where kerfs were filled with TTCPPS, there was minimal soft tissue volume at all time points. In contrast, for the control group bone flaps, the kerfs had more than 50% of their volume filled with soft tissue at 12 weeks and 1 year. TTCPPS yielded better bone flap fixation and better bone healing than plate and screw fixation. Hardware loosening, including instances of screw migration, was commonly observed with the bone flaps secured by plates and screws. Kerfs treated with TTCPPS had a high degree of osteointegration and minimal fibrosis. Soft tissue remained in the control group kerfs and hindered complete bone healing. In summary, an osteoconductive, wet-field, and bioresorbable bone adhesive can be produced by combining tetracalcium phosphate and phosphoserine. In this study, TTCPPS appeared to have multiple advantages over standard plate and screw bone flap fixation. These properties of TTCPPS may provide improved means for human cranial bone flap fixation and cranioplasty. Thank you.

bone adhesive

TTC-PPS

cranial bone flap fixation

titanium plates and screws

bone healing