Antimicrobial Effect of Silver-Coated External Fixator Pins

Abstract

One major complication of external fixation is pin track infection that may result in devastating osteomyelitis for the patient. The broad antimicrobial effect of silver is well known and this study was conducted to investigate the antibacterial activity of pins coated with colloidal silver. A total of 96 pins were inserted into one tibia of 24 sheep. Four pins of either stainless steel, titanium, silver-coated, or stainless steel pins coated with a polyurethane-argentum sleeve were inserted in six sheep, respectively. After pin insertion S. aureus was inoculated into the insertion channel between skin and bone and the animals were sacrificed after four weeks. Clinical assessment, radiological evaluation, microbiological and biomechanical testing, and histological methods were used. All animals developed clinical signs of infection after three to six days. The inoculated S. aureus was identified in all animals as an infection-causing strain by the DNA-fingerprinting technique. None of the different pin types, including silver-coated pins, showed a significant reduction of infection rates. Significant differences between the groups were rare and limited to few specific tests. Colloidal silver showed no significant reduction of pin track infections. Nanoparticulate silver with a higher active surface and a more homogenous distribution within biomaterials might be able to exhibit a better antimicrobial activity in coated pins.

Key words

External fixation - pin track infection - antibacterial activity - silver

References

• 1 Alt V, Bechert T, Steinrücke P, Wagener M, Seidel P, Dingeldein E, Schnettler R. An in vitro assessment of antibacterial properties and cytotoxicity of nanoparticulate silver bone cement.  Biomaterials. 2004;  in press
• 2 Anderson D E, St-Jean G, Richardson D C. et al . Improved osteointegration of calcium phosphate-coated external fixation pins.  Acta Orthop Scand. 1997;  68 571-576
• 3 Arciola C R, Montanaro L, Moroni A. et al . Hydroxyapatite-coated orthopaedic screws as infection resistant materials: in vitro study.  Biomaterials. 1999;  20 323-327
• 4 Augat P, Claes L, Hanselmann K F. et al . Increase of stability in external fracture fixation by hydroxyapatite-coated bone screws.  J Appl Biomater. 1995;  6 99-104
• 5 Bechert T, Böswald M, Lugauer S, Regenfus A, Greil J, Guggenbichler J P. The Erlanger silver catheter: In vitro results for antimicrobial activity.  Infection. 1999;  27 Suppl 1 S 24-S 29
• 6 Behrens F, Searls K. External fixation of the tibia.  J Bone Joint Surg [Br]. 1986;  68 246-254
• 7 Burny F, Adrianne Y, Donkerwocker M. et al .The Third Conference of the International Society of Fracture Repair. Book of Abstracts 1992; 67-68
• 8 Chao E YS, Hein T J. Mechanical performance of standard Orthofix external fixator.  Orthopedics. 1988;  11 1057-1069
• 9 Cheketts R G, Otterburn M. Pin tract infection: definition, prevention, incidence. Abstracts of the 2nd Riva Congress, Riva di Garda (Italy), University of Verona, University of Montpellier 1992; I: 98-99
• 10 Chu C S, McManus A T, Pruitt B A, Mason A D. Therapeutic effects of silver nylon dressing with weak direct current on Pseudomanas aeruginosa infected burn wounds.  J Trauma. 1988;  28 1488-1492
• 11 Collinge G A, Goll G, Seligson D, Easley K J. Pin track infection: silver vs. uncoated pins.  Orthopaedics. 1994;  17 445-448
• 12 Credé K SF. Die Verhütung der Augenentzündung der Neugeborenen, der häufigsten und wichtigsten Ursache der Blindheit. A. Hirsch-wald, 1894
• 13 Donath K, Breuner G. A method for the study of undecalcified bones and teeth with attached soft tissue. The Sage-Schliff technique.  Oral Pathol. 1982;  11 318-326
• 14 Fox C L. Silver sulfadiazine - a new topical agent.  Arch Surg. 1968;  96 184-188
• 15 Green S. Complications of external skeletal fixation.  Clin Orthop. 1983;  180 109-116
• 16 McGraw J M, Lim E V. Treatment of open tibial-shaft fractures: external fixation and secondary intramedullary nailing.  J Bone Joint Surg [Am]. 1988;  70 900-911
• 17 Moroni A, Caja V L, Sabatto C. et al . Biomechanical, scanning electron microscopy, and microhardness analyses of the bone pin interface in hydroxyapatite coated versus uncoated pins.  J Orthop Trauma. 1997;  11 154-161
• 18 Moroni A, Aspenberg P, Toksvig-Larsen S, Falzarano G, Giannini S. Enhanced fixation with hydroxyapatite coated pins.  Clin Orthop. 1998;  346 171-177
• 19 Petty W, Spanier S, Shuster J J, Silverthorne C. The influence of skeletal implants on incidence of infection.  J Bone Joint Surg [Am]. 1985;  67 1236-1244
• 20 Respet P J, Kliemann P G, Meinhard B P. Pin tract infections: a canine model.  J Orthoped Res. 1987;  5 600-603
• 21 Steinfeld P H, Cobelli N J, Sadler A H, Szporn M N. Open tibial fractures treated by anterior half-pin frame fixation.  Clin Orthop. 1988;  228 208-214
• 22 Voos K, Rosenberg B, Fagrhi M, Seligson D. Use of tobramycin-impregnated polymethylmethacrylate pin sleeve for the prevention of pin-tract infection in goats.  J Orthop Trauma. 1999;  13 98-101