Physicochemical Properties and Biocompatibility of Injectable Hydroxyapatite Cement and Its Application in Compressive Tibial Plateau Fractures

Injectable carbonated hydroxyapatite (ICHA) cement was developed by adding 2% Hydroxypropyl methylcellulose (HPMC) to carbonated hydroxyapatite (CHA) cement, improving its rheological properties and injectability for minimally invasive orthopedic use. The cement's physical and chemical properties, including curing time, strength, porosity, and consistency, were tested in vitro. Scanning electron microscopy, X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) were used to analyze the cured cement. Bone marrow stromal cells were cultured with ICHA cement extracts and specimens to test cell growth (MTT assay) and cytotoxicity. In vivo, the cement was implanted into rabbit muscles to assess inflammation and capsule formation, along with other biocompatibility tests, including hemolysis and pyrogen testing. ICHA cement sets without heat generation, with a 9-min initial setting time and a 15-min final setting time, similar to CHA cement. The strength reaches 20 MPa after 1 day and peaks at 35 MPa after 7 days. Its porosity is slightly higher than CHA cement, and it resists dilution well, preventing disintegration in water. The consistency of ICHA cement is lower than CHA cement at different time points (p < 0.001), showing a logarithmic change pattern. With adjustable setting time, good resistance to dilution, and compressive strength similar to cancellous bone, ICHA cement is well suited for clinical use. Its composition closely resembles natural bone, offering strong fixation and stability for tibial plateau healing, which supports early movement and reduces the risk of joint stiffness and post-traumatic arthritis.