Clinical Benefit of Hydroxyapatite-Coated Versus Uncoated External Fixation: A Systematic Review

Abstract

AIM: Common complications of external fixators include pinloosening, infection and loss of reduction/malunion. These are increased with prolonged fixation. The main aim of this systematic review was to investigate HA-coated versus uncoated external fixator and determine benefits in terms of pin loosening, infection and loss of reduction/malunion. MATERIAL AND METHODS: A systematic literature search using PubMed, EMBASE, OVID SP, Cochrane database, ClinicalTrials.gov website and the references of the studies identified was undertaken on 26th August 2014. Comparative trials investigating HA-coated versus uncoated external fixation pins were identified. These were limited using strict eligibility criteria and critically appraised as per the CASP and CONSORT guidelines. Primary outcome measures included pin loosening and infection. Secondary outcome measures included loss of reduction/malunion. RESULTS: Seven studies were identified of which five studies demonstrated a statistically significant reduction in loosening with HA-coated pins. There was insufficient evidence to demonstrate any clinical benefits, such as numbers needed to treat to avoid early removal of pins. Review of the studies included also demonstrated insufficient evidence to determine any significant clinical benefit with regards to infection and malunion. Critical appraisal demonstrated average methodological quality of the studies. CONCLUSION: HA-coating of external fixator pins improves bone fixation and reduces loosening in patients undergoing prolonged fixation procedures, such as leg-lengthening, but the influence on infection and malunion is not clear. Further large, well-designed randomised controlled trials with observer blinding, standardized pin insertion and pin care investigating clinically relevant pin loosening, infection and malunion are recommended. Patient reported, functional outcome measures should also be considered.

Clinical outcomes in pediatric tibial lengthening and deformity correction: A comparison of the Taylor Spatial Frame with the Orthex Hexapod System

“…Orthex half-pins have extended HA coating and are attached to the rings with double-column titanium blocks. A systematic review by Patel et al 17 has shown that HA-coated half-pins show less loosening but no overall reduction in infection rate was proven due to the heterogeneity of studies. We have also seen a reduction in foot and tibial wire infections episodes with fully HA-coated Orthex wires.…”

Overview of methods for enhancing bone regeneration in distraction osteogenesis: Potential roles of biometals

“…External fixation pin coating: The application of pin coatings such as hydroxyapatite (HA), titanium, and silver to enhance fixation and reduce infection has been studied for many years [ 31 , 32 ]. HA, constituting 65% of the human bone mineral component, is widely accepted as a bone substitute and prosthetic coating [ 31 ]. Piza et al.…”

“…Piza et al. reported that HA-coating could reduce pin loosening, while no significant difference was found in the infection rate between groups with or without HA-coating [ 31 , 33 ]. Pieske ​et al.…”

Titanium Kirschner Wires Resist Biofilms Better Than Stainless Steel and Hydroxyapatite-coated Wires: An In Vitro Study

“…Hydroxyapatite has been used as a coating on stainless steel pins to improve osseointegration and reduce pin loosening, although its effects on clinical infection rates are less clear. 26 , 45 The few in vitro studies of bacterial adhesion to and biofilm formation on hydroxyapatite coatings have produced conflicting results. Oga et al found with scanning electron microscopy that S. epidermidis adhered in greater numbers to hydroxyapatite than to the uncoated metals used in this study, 46 and Ravn et al have used microcalorimetry to reach a similar conclusion with S. aureus .…”

“…Hydroxyapatite-coated pins have been shown unequivocally to improve bone contact through osseointegration which, in turn, reduces the frequency of pin loosening in both humans and animals. 25 It is unclear, however, whether the improved bone contact made by hydroxyapatite-coated pins reduces clinical infection rates, 26 despite an in vitro study showing decreased staphylococcal adherence to such pins. 27 The interpretation of in vitro studies in this area has been complicated by variation in important factors such as the bacterial species and strains selected, biofilm definition and measurement, alloy composition, and the surface treatment of the metal.…”