The authors’ goal in this study was to investigate the use of a novel, bioresorbable, osteoconductive, wet-field mineral-organic bone adhesive composed of tetracalcium phosphate and phosphoserine (TTCP-PS) for cranial bone flap fixation and compare it with conventional low-profile titanium plates and self-drilling screws.
An ovine craniotomy surgical model was used to evaluate the safety and efficacy of TTCP-PS over 2 years. Bilateral cranial defects were created in 41 sheep and were replaced in their original position. The gaps (kerfs) were completely filled with TTCP-PS (T1 group), half-filled with TTCP-PS (T2 group), or left empty and the flaps fixated by plates and screws as a control (C group). At 12 weeks, 1 year, and 2 years following surgery, the extent of bone healing, local tissue effects, and remodeling of the TTCP-PS were analyzed using macroscopic observations and histopathological and histomorphometric analyses. Flap fixation strength was evaluated by biomechanical testing at 12 weeks and 1 year postoperatively.
No adverse local tissue effects were observed in any group. At 12 weeks, the bone flap fixation strengths in test group 1 (1689 ± 574 N) and test group 2 (1611 ± 501 N) were both statistically greater (p = 0.01) than that in the control group (663 ± 385 N). From 12 weeks to 1 year, the bone flap fixation strengths increased significantly (p < 0.05) for all groups. At 1 year, the flap fixation strength in test group 1 (3240 ± 423 N) and test group 2 (3212 ± 662 N) were both statistically greater (p = 0.04 and p = 0.02, respectively) than that in the control group (2418 ± 1463 N); however, there was no statistically significant difference in the strengths when comparing the test groups at both timepoints. Test group 1 had the best overall performance based on histomorphometric evaluation and biomechanical testing. At 2 years postoperatively, the kerfs filled with TTCP-PS had histological evidence of osteoconduction and replacement of TTCP-PS by bone with nearly complete osteointegration.
TTCP-PS was demonstrated to be safe and effective for cranial flap fixation in an ovine model. In this study, the bioresorbable, osteoconductive bone adhesive appeared to have multiple advantages over standard plate-and-screw bone flap fixation, including biomechanical superiority, more complete and faster bony healing across the flap kerfs without fibrosis, and the minimization of bone flap and/or hardware migration and loosening. These properties of TTCP-PS may improve human cranial bone flap fixation and cranioplasty.
ABBREVIATIONSTTCP-PS = tetracalcium phosphate and phosphoserine.
Correspondence Brian J. Hess: LaunchPad Medical, Lowell, MA. email@example.com.INCLUDE WHEN CITING Published online February 7, 2020; DOI: 10.3171/2019.11.JNS192806.Disclosures Funding for this study was provided by Stryker. Drs. Foley, Woodard, and Slotkin are consultants to LaunchPad Medical. Mr. Hess, Mr. Brown, and Ms. Baldwin are employees of LaunchPad Medical. Mrs. Mayotte is an employee of Stryker. Other associations include the following. Dr. Foley: consultant for Medtronic; direct stock ownership in Digital Surgery Systems, Discgenics, DuraStat, Medtronic, NuVasive, nView Medical, Practical Navigation/Fusion Robotics, SpineWave, TDi, and Triad Life Sciences; patent holder with Medtronic and NuVasive; royalties from Medtronic; board of directors of Digital Surgery Systems, Discgenics, DuraStat, LaunchPad Medical, nView Medical, Practical Navigation/Fusion Robotics, TDi, and Triad Life Sciences. Dr. Woodard: ownership in LaunchPad Medical. Dr. Slotkin: direct stock ownership in LaunchPad Medical. Ms. Baldwin: employee of LaunchPad Medical. Mr. Brown: employee and stockholder in LaunchPad Medical. Mr. Hess: ownership in LaunchPad Medical.
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