Implant-associated infection is a major source of morbidity in orthopaedic surgery. There has been extensive research into the development of materials that prevent biofilm formation, and hence, reduce the risk of infection. Silver nanoparticle technology is receiving much interest in the field of orthopaedics for its antimicrobial properties, and the results of studies to date are encouraging. Antimicrobial effects have been seen when silver nanoparticles are used in trauma implants, tumour prostheses, bone cement, and also when combined with hydroxyapatite coatings. Although there are promising results with in vitro and in vivo studies, the number of clinical studies remains small. Future studies will be required to explore further the possible side effects associated with silver nanoparticles, to ensure their use in an effective and biocompatible manner. Here we present a review of the current literature relating to the production of nanosilver for medical use, and its orthopaedic applications.

Cite this article: Bone Joint J 2015; 97-B:582–9.

We developed a method of applying vibration to the impaction bone grafting process and assessed its effect on the mechanical properties of the impacted graft. Washed morsellised bovine femoral heads were impacted into shear test rings. A range of frequencies of vibration was tested, as measured using an accelerometer housed in a vibration chamber. Each shear test was repeated at four different normal loads to generate stress-strain curves. The Mohr-Coulomb failure envelope from which shear strength and interlocking values are derived was plotted for each test. The experiments were repeated with the addition of blood in order to replicate a saturated environment.

Graft impacted with the addition of vibration at all frequencies showed improved shear strength when compared with impaction without vibration, with 60 Hz giving the largest effect. Under saturated conditions the addition of vibration was detrimental to the shear strength of the aggregate. The civil-engineering principles of particulate settlement and interlocking also apply to impaction bone grafting. Although previous studies have shown that vibration may be beneficial in impaction bone grafting on the femoral side, our study suggests that the same is not true in acetabular revision.

Introduction: At the time of revision hip surgery, large bony defects are often encountered. The traditional method of replacing this lost bone is by the impaction bone grafting technique. Vibration is commonly used in civil engineering to improve compaction of aggregate particles and to increase the compressive and shear strengths of the aggregate. Studies on soil mechanics have established that vibration applied to an aggregate results in more efficient alignment of particles and reduces the energy required to impact the aggregate. In this in-vitro study we have developed a novel method of applying vibration to the bone impaction process.

Methods: 60 Bovine femoral heads were cut into quarters and then milled using the Noviomagnus manual bone mill. Fat and blood were then removed using a pulsed lavage normal saline system over a sieve tower. A vibration impaction device was developed which housed two 15V DC motors with eccentric weights attached inside a metal cylinder. A weight was dropped onto this from a set height 72 times so as to replicate the bone impaction process. The bone graft underlying this was thus impacted into a pellet, with or without the aid of vibration. A range of frequencies of vibration were tested, as measured using an accelerometer housed in the vibration chamber.

Each shear test was then repeated at four different normal loads so as to generate a family of stress-strain graphs. The Mohr-Coulomb failure envelope from which the shear strength and interlocking vales are derived was plotted for each test.

Results: Graft impacted with the addition of vibration at 60Hz was significantly more resistant to shearing force than graft impacted without vibration (p< 0.03). Testing at 20 and 40 Hz showed no statistical difference (p=0.62, p=0.42).

Conclusion: Civil engineering principles hold true for the impaction bone grafting procedure. The best frequency of vibration to enhance the mechanical properties of the aggregate is in the region of 60Hz.