Effects of synergistic reinforcement and absorbable fiber strength on hydroxyapatite bone cement

Yu Zhang, Hockin H.K. Xu

Research output: Contribution to journalArticlepeer-review


Approximately a million bone grafts are performed each year in the United States, and this number is expected to increase rapidly as the population ages. Calcium phosphate cement (CPC) can intimately adapt to the bone cavity and harden to form resorbable hydroxyapatite with excellent osteoconductivity and bone-replacement capability. The objective of this study was to develop a strong CPC using synergistic reinforcement via suture fibers and chitosan, and to determine the fiber strength-CPC composite strength relationship. Biopolymer chitosan and cut suture filaments were randomly mixed into CPC. Both suture filaments and composite were immersed in a physiological solution. After 1-day immersion, cement flexural strengths (mean ± SD; n = 6) were: (2.7 ± 0.8) MPa for CPC control; (11.2 ± 1.0) MPa for CPC-chitosan; (17.7 ± 4.4) MPa for CPC-fiber composite; and (40.5 ± 5.8) MPa for CPC-chitosan-fiber composite. They are significantly different from each other (Tukey's at 0.95). The strength increase from chitosan and fiber together in CPC was much more than that from either fiber or chitosan alone. The composite strength became (9.8 ± 0.6) MPa at 35-day immersion and (4.2 ± 0.7) MPa at 119 days, comparable to reported strengths for sintered porous hydroxyapatite implants and cancellous bone. After suture fiber dissolution, long macropore channels were formed in CPC suitable for cell migration and tissue ingrowth. A semiempirical relationship between suture fiber strength SF and composite strength SC were obtained: SC = 14.1 + 0.047 SP, with R = 0.92. In summary, this study achieved substantial synergistic effects by combining random suture filaments and chitosan in CPC. This may help extend the use of the moldable, in situ hardening hydroxyapatite to moderate stress-bearing orthopedic applications. The long macropore channels in CPC should be advantageous for cell infiltration and bone ingrowth than conventional random pores and spherical pores.

Original languageEnglish (US)
Pages (from-to)832-840
Number of pages9
JournalJournal of Biomedical Materials Research - Part A
Issue number4
StatePublished - Dec 15 2005


  • Absorbable fiber
  • Bone repair
  • Calcium phosphate cement
  • High strength
  • Hydroxyapatite
  • Macropores

ASJC Scopus subject areas

  • Ceramics and Composites
  • Biomaterials
  • Biomedical Engineering
  • Metals and Alloys


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