Hydroxyapatite-coated Schanz pins in external fixators used for distraction osteogenesis : a randomized, controlled trial.
BACKGROUND
Complications of external fixation include loosening of the fixation pins and pin-track infection. Laboratory studies and clinical trials have suggested that hydroxyapatite coating improves the osteointegration of various orthopaedic implants. The purpose of this study was to determine whether the prevalence of pin-related complications can be reduced by the use of hydroxyapatite-coated pins in fixators applied for distraction osteogenesis.


METHODS
Forty-six consecutive patients undergoing segmental transport or lengthening of the tibia were randomized to the use of either standard titanium Schanz pins or hydroxyapatite-coated stainless-steel Schanz pins. The fixators were used for an average of thirty-eight weeks (range, fourteen to seventy-two weeks). All patients were closely monitored for pin loosening and infection, and digitized radiographs were assessed for bone resorption around all pins. When the external fixator was removed, the torque required to extract the pins was determined with use of an electronic torque wrench.


RESULTS
In the control group (titanium pins), twenty-two pins (13%) loosened and an infection occurred at the site of twenty pins. An extensive infection of the canal developed in one patient. Twenty-two pins were removed or replaced because of these complications. In the hydroxyapatite group, no clinical or radiographic signs of pin loosening or infection were observed and no pins required early removal or exchange. The mean torque (and standard deviation) required to remove the hydroxyapatite-coated pins was 0.43 0.18 N-m compared with 0.10 0.09 N-m for the uncoated pins (p < 0.001).


CONCLUSIONS
Coating pins with hydroxyapatite increases their fixation to bone and reduces the rate of infection and loosening during external fixation for distraction osteogenesis. Use of hydroxyapatite-coated pins should be considered in clinical situations requiring prolonged external fixation.
Pommer
Axel
A
Department of Surgery, Klinikum Bergmannsheil Bochum, Rurh-University, Bochum, Germany.
Muhr
Gert
G
Dávid
Andreas
A
D000293:Adolescent; D000328:Adult; D001672:Biocompatible Materials; D001858:Bone Nails; D020099:Coated Materials, Biocompatible; D017886:Durapatite; D004867:Equipment Design; D016267:External Fixators; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D019857:Osteogenesis, Distraction / Q000295:instrumentation*; D015995:Prevalence; D011446:Prospective Studies; D011475:Prosthesis Failure; D016459:Prosthesis-Related Infections / Q000453:epidemiology; D013977:Tibia / Q000601:surgery*
D001672:Biocompatible Materials; D020099:Coated Materials, Biocompatible; D017886:Durapatite