Thickness of fibrous capsule after implantation of hydroxyapatite in subcutaneous tissue in rats

Dong Jun Li, Katsuichiro Ohsaki, Kunio Ii, Peng Cheng Cui, Qing Ye, Kyoko Baba, Qing Chun Wang, Satoru Tenshin, Teruko Takano-Yamamoto

Research output: Contribution to journalArticlepeer-review

34 Citations (Scopus)


The present study evaluates in rats the histomorphometrical thickness of fibrous capsules that surround hydroxyapatite (HA) disks after implantation. HA disks were implanted into the subcutaneous tissue of 79 rats for 1 day to 20 months. Decalcified histological sections stained with hematoxylin and eosin were examined. Fibrous capsule thickness (FCT) was measured using an objective micrometer. On the fourteenth day, primary fibrous capsules formed around implants. From that time point FCT increased with time of implantation. Within a given sample, FCT differed from one portion of the fibrous capsule to another, depending on which site faced the disks. FCT was thickest at the upper and lower portions of the disks, thinner at the lateral portions, and thinnest at the upper and lower ring-shaped portions. Two possible explanations for the above findings are discussed in this paper: (1) The area of contact between disk and tissue differs. (2) chemical stimulation of implanted material caused by demineralization and remineralization may result from the varying thicknesses of fibrous capsules. FCT from upper and lower portions of HA disks increased by over 200% in the first 10 months and steadily increased about 20% over the next 10 months. Many studies have concluded that HA is useful for reconstructive surgery, so the long-term effects of FCT need further study.

Original languageEnglish
Pages (from-to)322-326
Number of pages5
JournalJournal of Biomedical Materials Research
Issue number4
Publication statusPublished - 1999 Jun 15


  • Fibrous capsule
  • Histomorphometry
  • Hydroxyapatite
  • Long-term reaction
  • Rats

ASJC Scopus subject areas

  • Biomaterials
  • Biomedical Engineering


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