Development of Biodegradable Osteopromotive Citrate-Based Bone Putty.

The burden of bone fractures demands development of effective biomaterial solutions, while additional acute events such as noncompressible bleeding further motivate the search for multi-functional implants to avoid complications including osseous hemorrhage, infection, and nonunion. Bone wax has been widely used in orthopedic bleeding control due to its simplicity of use and conformation to irregular defects; however, its nondegradability results in impaired bone healing, risk of infection, and significant inflammatory responses. Herein, a class of intrinsically fluorescent, osteopromotive citrate-based polymer/hydroxyapatite (HA) composites (BPLP-Ser/HA) as a highly malleable press-fit putty is designed. BPLP-Ser/HA putty displays mechanics replicating early nonmineralized bone (initial moduli from ≈2-500 kPa), hydration induced mechanical strengthening in physiological conditions, tunable degradation rates (over 2 months), low swelling ratios (<10%), clotting and hemostatic sealing potential (resistant to blood pressure for >24 h) and significant adhesion to bone (≈350-550 kPa). Simultaneously, citrate's bioactive properties result in antimicrobial (≈100% and 55% inhibition of S. aureus and E. coli) and osteopromotive effects. Finally, BPLP-Ser/HA putty demonstrates in vivo regeneration in a critical-sized rat calvaria model equivalent to gold standard autograft. BPLP-Ser/HA putty represents a simple, off-the-shelf solution to the combined challenges of acute wound management and subsequent bone regeneration.

Glenoid cement mantle characterization using micro-computed tomography of three cement application techniques.

BACKGROUND: Numerous studies have documented the concern for progressive radiolucent lines, signifying debonding and subsequent aseptic loosening of the glenoid component. In this study, we compared 3 cementation methods to secure a central peg in 15 cadaveric glenoids. METHODS: Cement application techniques consisted of (1) compression of multiple applications of cement using manual pressure over gauze with an Adson clamp, (2) compression of multiple applications of cement using a pressurizer device, and (3) no compression of a single application of cement. Each glenoid was then imaged with high-resolution micro-computed tomography and further processed by creating 3-dimensional computerized models of implant, bone, and cement geometry. Cement morphology characteristics were then analyzed in each of the models. RESULTS: There were no significant differences detected between the 2 types of compression techniques; however, there was a significant difference between compression methods and use of no compression at all. All morphologic characteristics of a larger cement mantle were significantly correlated with greater cortical contact. CONCLUSIONS: We demonstrate that compression techniques create a larger cement mantle. Increased size of the cement mantle is associated with increased contact with cortical bone at the glenoid vault. This method for characterizing the cement mantle by micro-computed tomography scanning techniques and 3-dimensional analysis may also be useful in future finite element analysis studies.

Peri-implant stress correlates with bone and cement morphology: Micro-FE modeling of implanted cadaveric glenoids.

Aseptic loosening of cemented joint replacements is a complex biological and mechanical process, and remains a clinical concern especially in patients with poor bone quality. Utilizing high resolution finite element analysis of a series of implanted cadaver glenoids, the objective of this study was to quantify relationships between construct morphology and resulting mechanical stresses in cement and trabeculae. Eight glenoid cadavers were implanted with a cemented central peg implant. Specimens were imaged by micro-CT, and subject-specific finite element models were developed. Bone volume fraction, glenoid width, implant-cortex distance, cement volume, cement-cortex contact, and cement-bone interface area were measured. Axial loading was applied to the implant of each model and stress distributions were characterized. Correlation analysis was completed across all specimens for pairs of morphological and mechanical variables. The amount of trabecular bone with high stress was strongly negatively correlated with both cement volume and contact between the cement and cortex (r = -0.85 and -0.84, p < 0.05). Bone with high stress was also correlated with both glenoid width and implant-cortex distance. Contact between the cement and underlying cortex may dramatically reduce trabecular bone stresses surrounding the cement, and this contact depends on bone shape, cement amount, and implant positioning.