Abstract
Purpose: Four external fixation pin types differing in coating, design and implantation technique were tested in an animal study.
Methods: Forty tapered pins were divided into 4 Groups according to pin design type: Group A consisted of 10 standard self-tapping pins (ø5–6mm, pitch 1.75mm), Group B 10 hydroxyapatite (HA)-coated self-tapping (ø5–6mm, pitch 1.75mm), Group C 10 standard, self-drilling, self-tapping (ø5–6mm, pitch 1.25mm) and Group D 10 HA-coated, self-drilling, self-tapping (ø5–6mm, pitch 1.25mm). Four pins were randomly implanted into the femoral diaphysis of 10 sheep. The pins were implanted at 2-cm intervals apart. Pre-drilling was used for Groups A and B but not for Groups C and D. Sheep were euthanized 6 weeks after surgery.
Results: There were no major complications. Mean pin insertion torque was 3100 ± 915 Nmm in Group A, 2808 ± 852 Nmm in Group B, 2589 ± 852 Nmm in Group C and 2180 ± 652 Nmm in Group D. Mean pin extraction torque was 1570 ± 504 Nmm in Group A, 2128 ± 1159 Nmm in Group B, 1599 ± 809 Nmm in Group C and 2200 ± 914 Nmm in Group D. Insertion torque of the coated groups was lower than insertion torque of the standard groups (p < 0.05). However, extraction torque of Groups B and D was higher than Groups A and C (p < 0.05). No differences in pin fixation were found between the two coated pin groups (Group B and D). Morphologic analysis showed extensive bone to pin contact without fibrous tissue interposition in the coated pin groups and fibrous tissue interposition in the uncoated pin groups.
Conclusion/Significance: This study demonstrated that coating pins with hydroxyapatite is effective regardless of the pin design and the implantation technique.
Theses abstracts were prepared by Professor Roger Lemaire. Correspondence should be addressed to EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
