We have developed precision-engineered strontium eluting nanopatterned surfaces. Nanotopography has been shown to increase osteoblast differentiation, and strontium is an element similar to calcium, which has been proven to increase new bone formation and mineralization. This combination has great potential merit in fusion surgery and arthroplasty, as well as potential to reduce osteoporosis. However, osteoclast mediated osteolysis is responsible for the aseptic failure of implanted biomaterials, and there is a paucity of literature regarding osteoclast response to nanoscale surfaces. Furthermore, imbalance in osteoclast/osteoblast resorption is responsible for osteoporosis, a major healthcare burden. We aimed to assess the affect of strontium elution nanopatterned surfaces on osteoblast and osteoclast differentiation.

We developed a novel human osteoblast/osteoclast co-culture system without extraneous supplementation to closely represent the in vivo environment. We assessed the surfaces using electron microscopy (SEM), protein expression using immunofluorescence and histochemical staining and gene expression using polymerase chain reaction (PCR).

In complex co-culture significantly increased osteoblast differentiation and bone formation was noted on the strontium eluting, nanopatterned and nanopatterned strontium eluting surfaces, suggesting improved osteointegration. There was a reduction in macrophage attachment on these surfaces as well, suggesting specific anti-osteoclastogenic properties of this surface.

Our results show that osteoblast and osteoclast differentiation can be controlled through use of nanopatterned and strontium eluting surface features, with significant bone formation seen on these uniquely designed surfaces.

Nanotopographical cues on Ti surfaces have been shown to elicit different cell responses such as differentiation and selective growth. Bone remodelling is a continuous process requiring specific cues for optimal bone growth and implant fixation. In addition, the prevention of biofilm formation on surgical implants is a major challenge. We have identified nanopatterns on Ti surfaces that would be optimal for both bone remodelling and for reducing risk of bacterial infection. We used primary human osteoblast/osteoclast co-cultures and seeded them on flat Ti and three Ti nanosurfaces with increasing degrees of roughness, manufactured using anodisation under alkaline conditions (for 2, 2.5 and 3 hours). Cell growth and behaviour was assessed by scanning electron microscopy (SEM), immunofluorescence microscopy, histochemistry and quantitative RT-PCR methods. Bacterial growth on the nanowire surfaces was also assessed by confocal microscopy and SEM. From the three surfaces tested, the 2 h nanowire surface supported osteoblast and, to a lesser extent, osteoclast growth and differentiation. Bacterial viability was significantly reduced on the 2h surface. Hence the 2 h surface provided optimal bone remodelling conditions while reducing infection risk, making it a favourable candidate for future implant surfaces. This work was funded by EPSRC grant EP/K034898/1.

Background

Aseptic loosening remains the primary reason for failure of orthopaedic implants. Therefore a prime focus of Orthopaedic research is to improve osteointegration and outcomes of joint replacements. The topography of a material surface has been shown to alter cell adhesion, proliferation and growth. The use of nanotopography to promote cell adhesion and bone formation is hoped to improve osteointegration and outcomes of implants. We have previously shown that 15nm high features are bioactive. The arrangement of nanofeatures has been shown to be of importance and block-copolymer separation allows nanopillars to be anodised into the titania layer, providing a compromise of control of order and height of nanopillars. Osteoblast/osteoclast stem cell co-cultures are believed to give the most accurate representation of the in vivo environment, allowing assessment of bone remodelling related to biomaterials.

Allogenic blood is a finite resource, with associated risks. Previous studies have shown intra-operative cell salvage (ICS) can reduce allogenic transfusion rates in orthopaedic surgery. However, recent concerns regarding the efficacy and cost-effectiveness of ICS mean we must continually re-assess its usefulness in current practice. This study was carried out to review the use of ICS, to establish if its use has led to a reduction in patient exposure to post-op allogenic transfusion.

All orthopaedic patients who underwent ICS and re-infusion between 2008–2010 in the Southern General Hospital (SGH) were audited. The Haemoglobin (Hb) drop, volume of blood re-infused and post-op allogenic transfusion rates were recorded. The revision hip group was compared to a similar SGH cohort, who underwent surgery by the same surgeons between 2006–2008, and a pre-2005 control group. The Cell Saver (Haemonetics) machine was used.

The proportion of patients who received a post-op allogenic transfusion fell by 55% in the 2008–2010 ICS cohort compared with the control, and by 40% compared with the previous ICS study group. In both instances, this was accompanied by a statistically significant (p<0.001) reduction in mean number of units transfused per patient.

ICS has been shown to be effective in reducing rates and volume of post-op allogenic transfusion in patients undergoing revision hip surgery at the SGH. ICS has been used with increasing efficiency over time.