Silver Nanoparticle (AgNP) Technology applications in trauma and orthopaedics

Recently Nanotechnology advances continue to accelerate with development of incredible new materials and products in the field of science. The Nanotechnology has evolved in the domains of prevention, diagnosis and treatment in the field of trauma and orthopaedics. It provides a spectrum of new tools such as drug delivery (chemotherapy in orthopaedic oncology), diagnosis (bone diseases, osteoporosis, metastatic osteosarcoma), improving osteointegration of implant materials (implants & total joint replacements), combating infection (trauma implants and prosthesis), tissue engineering (hydroxyapatite scaffolds, cartilage defects, stem cell regeneration) and prevention of osteoporosis. The current article highlights the role of Silver Nanoparticle (AgNP) Technology applications in Trauma and Orthopaedics.

Synthetic bone: Design by additive manufacturing

A broad range of synthetic trabecular-like metallic lattices are 3D printed, to study the extra design freedom conferred by this new manufacturing process. The aim is to propose new conceptual types of implant structures for superior bio-mechanical matching and osseo-integration: synthetic bone. The target designs are 3D printed in Ti-6Al-4V alloy using a laser-bed process. Systematic evaluation is then carried out: (i) their accuracy is characterised at high spatial resolution using computed X-ray tomography, to assess manufacturing robustness with respect to the original geometrical design intent and (ii) the mechanical properties - stiffness and strength - are experimentally measured, evaluated, and compared. Finally, this new knowledge is synthesised in a conceptual framework to allow the construction of so-called implant design maps, to define the processing conditions of bone tailored substitutes, with focus on spine fusion devices. The design criteria emphasise the bone stiffness-matching, preferred range of pore structure for bone in-growth, manufacturability of the device and choice of inherent materials properties which are needed for durable implants. Examples of the use of such maps are given with focus on spine fusion devices, emphasising the stiffness-matching, osseo-integration properties and choice of inherent materials properties which are needed for durable implants. STATEMENT OF SIGNIFICANCE: We present a conceptual bio-engineering design methodology for new biomedical lattices produced by additive manufacturing, which addresses some of the critical points in currently existing porous implant materials. Amongst others: (i) feasibility and accuracy of manufacturing, (ii) design to the elastic properties of bone, and (iii) sensible pores sizes for osseointegration. This has inspired new and novel geometrical latticed designs which aim at improving the properties of intervertebral fusion devices. In their fundamental form, these structures are here fabricated and tested. When integrated into medical devices, these concepts could offer superior medical outcomes.

A pilot trial comparing the tear-out behavior in screw-sockets and cemented polyethylene acetabular components - a cadaveric study

BACKGROUND

The removal of well-fixed acetabular components following THA (total hip arthroplasty) is a difficult operation and could be accompanied by the loss of acetabular bone stock. The optimal method for fixation is still under debate. The aim of this pilot study was to compare the tear-out resistance and failure behavior between osseo-integrated and non-integrated screw cups. Furthermore, we examined whether there are differences in the properties mentioned between screw sockets and cemented polyethylene cups.

HYPOTHESIS

Tear-out resistance and related mechanical work required for the tear-out of osseo-integrated screw sockets are higher than in non-integrated screw sockets.

PATIENTS AND METHODS

Ten human coxal bones from six cadavers with osseo-integrated screw sockets (n=4), non-integrated (implanted post-mortem, n=3) screw sockets and cemented polyethylene cups (n=3) were used for tear-out testing. The parameters axial failure load and mechanical work for tear-out were introduced as measures for determining the stability of acetabular components following THA.

RESULTS

The osseo-integrated screw sockets yielded slightly higher tear-out resistance (1.61±0.26kN) and related mechanical work compared to the non-integrated screw sockets (1.23±0.39kN, P=0.4). The cemented polyethylene cups yielded the lowest tear-out resistance with a failure load of 1.18±0.24kN. Compared to the screw cups implanted while alive, they also differ on a non-significant level (P=0.1). Osseous failure patterns differed especially for the screw sockets compared to the cemented polyethylene cups.

DISCUSSION

Osseo-integration did not greatly influence the tear-out stability in cementless screw sockets following axial loading. Furthermore, the strength of the bone-implant-interface of cementless screw sockets appears to be similar to cemented polyethylene cups. However, given the high failure load, high mechanical load and because of the related bone failure patterns, removal should not be performed by means of tear-out but rather by osteotomes or other curved cutting devices to preserve the acetabular bone stock.

LEVEL OF EVIDENCE

Level III, case-control-study.

Experience of bone-anchored hearing aid implantation in children younger than 5 years of age

OBJECTIVE

To assess the practicality and benefit of Bone-anchored hearing aid (BAHA(®)) implantation in children younger than 5 years of age. FDA approval for use of BAHA(®) only exists for children 5 years of age and older. Their use in Australia is also rare, however their use for younger children is approved by the European Union. We wish to share our experience of implantation in an antipodean setting in this age group.

METHODS

Institutional board approval was obtained for this study. All children undergoing BAHA(®) implantation under 5 years old were included from our prospective database. We examined the variety of surgical techniques, (including skin grafting, limited soft tissue reduction and no soft tissue reduction), BAHA(®) implants and abutments used, and use of the new series 400 hydroxyapatite coatings. Demographic data obtained included age at surgery, follow up duration, gender, ethnicity and indication for surgery. Anonymous benefit questionnaires (Glasgow children's benefit inventory (GCBI) and parents' evaluation of aural performance of children (PEACH)) were completed online as well as a questionnaire on device use. Complications recorded included soft tissue reactions, implant loss/removal, abutment replacement/removal. We also assessed whether patient weight, ethnicity or socioeconomic status were risk factors for these complications.

RESULTS

24 Children (26 ears/26 implants) under five years were identified from the database and included in the study. There was a 14:10 male to female ratio. Patient caregivers reported subjective benefit and improved quality of life (QOL) despite setbacks and complications related to BAHA(®) usage. 10/24 (42%) of children required treatment for significant peri-implant skin reactions whilst 25% required replacement of their abutments and/or implants. An increased risk of major complication was associated with socioeconomic deprived backgrounds and in patients of New Zealand Maori and Pacific Island ethnicity but not in patients with increased weight centiles.

CONCLUSIONS

The BAHA(®) implant and hearing aid system is of value to children under age 5 years. Parents tolerate the skin reactions and complications because of the perceived benefit in hearing and quality of life. Careful counselling of parents of potential young BAHA(®) implant candidates is necessary in light of this.

Nanotechnology: current concepts in orthopaedic surgery and future directions

Nanotechnology is the study, production and controlled manipulation of materials with a grain size < 100 nm. At this level, the laws of classical mechanics fall away and those of quantum mechanics take over, resulting in unique behaviour of matter in terms of melting point, conductivity and reactivity. Additionally, and likely more significant, as grain size decreases, the ratio of surface area to volume drastically increases, allowing for greater interaction between implants and the surrounding cellular environment. This favourable increase in surface area plays an important role in mesenchymal cell differentiation and ultimately bone-implant interactions. Basic science and translational research have revealed important potential applications for nanotechnology in orthopaedic surgery, particularly with regard to improving the interaction between implants and host bone. Nanophase materials more closely match the architecture of native trabecular bone, thereby greatly improving the osseo-integration of orthopaedic implants. Nanophase-coated prostheses can also reduce bacterial adhesion more than conventionally surfaced prostheses. Nanophase selenium has shown great promise when used for tumour reconstructions, as has nanophase silver in the management of traumatic wounds. Nanophase silver may significantly improve healing of peripheral nerve injuries, and nanophase gold has powerful anti-inflammatory effects on tendon inflammation. Considerable advances must be made in our understanding of the potential health risks of production, implantation and wear patterns of nanophase devices before they are approved for clinical use. Their potential, however, is considerable, and is likely to benefit us all in the future.