Fixation strength of tapered versus bicylindrical hydroxyapatite-coated external fixation pins: An animal study

✍ Scribed by Moroni, Antonio ;Faldini, Cesare ;Pegreffi, Francesco ;Giannini, Sandro

• Publisher: John Wiley and Sons
• Year: 2002
• Tongue: English
• Weight: 176 KB
• Volume: 63
• Category: Article
• ISSN: 0021-9304
• DOI: 10.1002/jbm.10088

✦ Synopsis

Abstract

The purpose of this study was to comparatively measure the bone–pin interface strength in two types of hydroxyapatite‐coated pins that differed in shape, diameter, and implantation technique. Both pin types are commonly used for tibia fixation. Thirty bicylindrical 5/4‐mm stainless‐steel pins (Group A) and 30 tapered 6/5‐mm stainless‐steel pins (Group B) were implanted in the left tibiae of 10 adult sheep. A monolateral fixator was mounted on the pins after implantation. A 5‐mm‐long bone segment was removed from the tibial mid‐diaphysis to ensure high load at the bone–pin interface. Pin insertion torque was 830 ± 446 N/mm in Group A and 3415 ± 743 N/mm in Group B (p<0.0001, one‐way ANOVA). Six weeks after surgery, the sheep were euthanized and pin extraction torque measured. Pin extraction torque was 1237 ± 499 N/mm in Group A and 3367 ± 1512 N/mm in Group B (p<0.0001, Mann‐Whitney test). Morphological analysis performed at 60× magnification showed a direct bone–pin contact in both groups. Despite challenging biomechanical conditions, this study showed both pin types to be well‐fixed and osteointegrated. Therefore, both pin types are recommended for tibial fixation. However, the tapered pins showed higher extraction torque, an important result for external fixation treatments. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 61–64, 2002