Hydroxyapatite pins for external fixation: is there sufficient evidence to prove that coated pins are less likely to be replaced prematurely?

OBJECTIVE Several clinical studies have reported that the use of hydroxyapatite- (HA) coated pins enhance external fixation. Although these studies have demonstrated higher extraction torques and lower rates of pin loosening with HA coating, there is little evidence to suggest that these biomechanical advantages translate to a lower rate of pin replacement prior to healing. The research question posed was "Is there sufficient evidence to prove that hydroxyapatite coating lowers the rate of pin replacement for external fixation?" METHODS An electronic search of Medline (Ovid, 1946 - December Week 4 2011), Embase (Ovid, 1980-2011 Week 52), and the Cochrane Central Register of Controlled Trials (Issue 4 of 4, October 2011) was conducted to identify all randomized and quasi-randomized controlled trials which compared HA-coated pins with non-coated pins for external fixation, with particular emphasis on the premature replacement of pins as a consequence of loosening. RESULTS The combined search strategies retrieved 72 citations. Four randomized controlled trials (101 patients, 327 HA-coated vs. 354 uncoated pins) were included in this review. None of the studies demonstrated a clear benefit between pin types with respect to premature replacement of pins prior to healing. CONCLUSION This review did not find sufficient evidence to validate the preferential use of HA-coated pins over standard pins as a means of avoiding premature replacement of pins used for external fixation. The use of uncoated pins is justifiable, especially within the context of limited financial resources.