Hydroxyapatite-coated external fixation pins

Antonio Moroni, Francesco Pegreffi, Matteo Cadossi, Amy Hoang-Kim, Valentino Lio, Sandro Giannini

Research output: Contribution to journalArticlepeer-review


The aim of this review is to report on studies of hydroxyapatite-coated external fixation pins as a solution to enhance pin fixation. In a highly loaded animal study, three tapered pin types were compared: Type A uncoated, Type B coated with hydroxyapatite and Type C coated with titanium. There was a 13-fold increase in the extraction torque of Type B pins compared with Type A, and a twofold increase compared with Type C pins. Extraction torque was significantly lower compared with the corresponding insertion torque in both Types A (p <0.001) and C (p = 0.003). Conversely, with the hydroxyapatite-coated pins there was no difference between extraction and insertion torque. In a clinical study of 76 external fixation pins in 19 patients treated with hemicallotasis for osteoarthritis on the medial side of the knee, pin insertion and extraction torque forces were measured. The patients were randomized to be treated with either standard tapered pins or tapered pins coated with hydroxyapatite. Extraction torque of the hydroxyapatite-coated pins was higher than the extraction torque of the standard pins in both cancellous and cortical bone (p <0.005). In a prospective, randomized clinical study of osteoporotic wrist fractures, extraction torque of the coated pins was higher than with standard pins (p <0.0001). These studies demonstrate that with the use of hydroxyapatite-coated pins, no deterioration of pin fixation occurs, and that there is no significant pin loosening and infection, regardless of bone type and loading conditions.

Original languageEnglish
Pages (from-to)465-471
Number of pages7
JournalExpert Review of Medical Devices
Issue number4
Publication statusPublished - Jul 2005


  • External fixation
  • Hydroxyapatite
  • Infection
  • Pin loosening
  • Pins

ASJC Scopus subject areas

  • Biophysics
  • Surgery
  • Reviews and References, Medical


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