= Abstract = A Study on the Potential of Hydroxyapatite Based Bioactive Bone Cement Jung-Woog Shin, Seok Bong Kim, Taek Lim Yoon*, Young Kon Kim, Ki Dong Park, Jin Woo Lee, Su-A Park, Young Jick Kim Department of Biomedical Engineering, Inje University, Department of Orthopaedic Surgery, College of Medicine, Chunnam National University*, Department of Molecular Science and Technology, Ajou University, Department of Orthopaedic Surgery, College of Medicine, Yonsei University Study on the Potential of Hydroxapatite Based Bioactive Bone Cement Purpose: The purpose of this study is to propose a new bioactive bone cement (BBC) composed of bone powder (hydroxyapatite; HA), chitosan powder, and currently available polymethylmethacrylate (PMMA) bone cement for use in orthopaedic surgeries such as vertebroplasty or bone filler. Materials and Methods: Three types of proposed BBCs and a currently available commercial PMMA were tested. In vitro studies the surface morphology, chemical composition, changes in ph value along the time, exothermic temperatures, intrusion and cellular responses were investigated. SEM, radiological and histological examinations were performed in animal studies. R e s u l t s: The major components of BBCs were C, O, Ca, P, Cl, Si, S, Ba and Mg. The ph values in BBCs decreased after 1 day, however they eventually reached 7.2-7.4. The water absorbency, weight loss, and porosity in BBCs increased more than PMMA more than during degradation (p<0.05). However, the compressive Young s moduli and ultimate compressive strength (UCS) of BBCs were lower than those of PMMA (<0.05). The exothermic temperatures of the BBCs were considerably lower than that of PMMA (p<0.05). In view of setting time, it takes relatively longer for BBCand to be solidified than PMMA (p<0.05). The intrusion tests showed that the BBCs were more intrusive than PMMA (p<0.05). The cell proliferation test on B B Cshowed that the BBCwas more preferable than the PMMA. No cytotoxic characteristics were
found in all BBCs. In the animal test, BBC II was more biocompatible as well as osteoconductible than the PMMA. Conclusion: The results of in vitro and animal studies indicated that the proposed BBCs have a potential of clinical application as replacement of the current PMMA bone cements. Key Words: Hydroxyapatite, Chitosan, PMMA bone cement, Bioactive, Biocompatibility
Table 1. Compositions of the specimens Bone cements Powder (wt%) PMMA Bone (HA) Chitosan Simplex P 100 0 0 BBC 50 40 10 BBC 40 50 10 BBC 30 60 10
Fig. 1. The average size of the particles and their distribution provided by a sieve analyzer. (a) PMMA powder(300) (b) HA powder(300) (c) Chitosan powder(300) Fig. 2. SEM morphologies of powders consisting of BBCs.
Fig. 3. The chemical composition of powders analyzed by EDX.
Fig. 4. The change in ph values of the specimens: The solution was replaced everyday. (A) a. PMMA(300) b. BBC(300) c. BBC(300) d. BBC(300) (B) a. PMMA(300) b. BBC(300) c. BBC(300) d. BBC(300) Fig. 5. The micro-structure of each specimen(sem): A. Before degradation, B. After degradation (8 weeks).
Fig. 6. The change in ph values during the degradation: The solution was not replaced. Fig. 7. The change in water absorbency during the degradation for each specimen. Fig. 8. The percentage in weight loss during the degradation for each specimen. Fig. 9. The change in porosity during the degradation for each specimen.
A B Fig. 10. The typical mechanical properties of each specimen during the degradation: (A) Compressive Young s moduli, (B) Ultimate Compressive Strength(UCS). Fig. 11. The change in exothermic temperature during polymerization with setting time. Fig. 12. Comparision of intrusive lengths of PMMA and BBC. This was more intrusive than that.
Fig. 13. Comparision of cell proliferations of PMMA and BBC II. The MTT assay showed that the cells were more proliferative on BBC II. Fig. 14. Radiological examinations of tibia and femur with injected PMMA and BBC. They revealed the radiopacity of the BBC. A a. 0 weeks b. 2 weeks c. 4 weeks d. 4 weeks (3.5k) (10.0k) (500) (10.0k). B a. 0 weeks b. 2 weeks c. 4 weeks d. 4 weeks (3.5k) (10.0k) (500) (10.0k) Fig. 15. The observations of the interfaces between the bone and bone cements: (A) bone-pmma, (B) bone-bbc II.
A B a. 2 weeks(20) b. 4 weeks(20) a. 2 weeks(20) b. 4 weeks(20) Fig. 16. The histological examinations of the interfaces between the bone and bone cements after 2 and 4 weeks implantation. After 4 weeks of implantation, new bone formations were observed more in this than that (H E stain).
A B
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