Prosthetic joint infections (PJI) occur infrequently, but they represent the most devastating complication with high morbidity and substantial cost. Staphylococcus aureus and coagulase-negative S. epidermidis are the most commonly infecting agents associated with PJI. Nowadays, Gram-negative species like Escherichia coli and Pseudomonas aeruginosa are gaining relevance.

The use of TiO2 conical nanotubular doped with fluorine and phosphorous (FP-cNT) surfaces is an interesting approach to prevent surface bacterial colonization during surgery and favouring the osseointegration. Despite of there are serum markers related with PJI, to date there is described no biomaterial-related marker that allows detecting PJI. Here we describe the adherence and the bactericidal effect of FP-cNT and its capacity of marking the non-fermenting bacteria that have been in contact with it by Al. This metal is delivered by FP-cNT in non-toxic concentrations (between 25 and 29 ng/mL).

F-P-cNT layers on Ti6Al4V alloy were produced as described previously by our group. Ti6Al4V chemical polishing (CP) samples without nanostructure were used as control and produced as described previously.

S. aureus 15981, S. epidermidis ATCC 35984, E. coli ATCC 25922, and P. aeruginosa ATCC 27853 strains adherence study was performed using the protocol described by Kinnari et al. in 0.9% NaCl sterile saline with a 120 min incubation. After incubation, the samples were stained with LIVE/DEAD BacLight Bacterial Viability Kit. Proportion of live and dead bacteria was calculated and studied by using ImageJ software. The experiments were performed in triplicate. The aluminum concentration was estimated in the supernatant after incubation and in the 0.22 µm filtered supernatant by atomic absorption in graphite furnace.

The statistical data were analyzed by nonparametric Kruskal-Walis test and by pairwise comparisons using the nonparametric unilateral Wilcoxon test with a level of statistical significance of p<0.05. The values are cited as medians.

Our results show that the bacterial adherence of all tested species significantly decreased on FP-cNT compared to CP except P. aeruginosa ATCC 27853: 19.8% for S. aureus 15981, 45.3% for S. epidermidis ATCC 35984 and 8.1% for E. coli ATCC 25922. The bacterial viability decreased 2-fold for S. aureus 15981, and 5-fold for S. epidemidis ATCC 35984, but increased 95% for P. aeruginosa ATCC 27853 and there no was variation for E. coli ATCC 25922 on FP-cNT compared to CP. Only supernatant P. aeruginosa ATCC 27853 shows significant Al detection after 120 min incubation (p<0.05).

In summary, F-P cNT is a promising biomaterial that besides favoring osseointegration and potential usefulness as drug carrier, present bactericidal, non-stick ability (at least for staphylococci and E. coli) and is able to mark P. aeruginosa with Al, which could be potentially monitored in serum and urine in patients with PJI.

Abstract. Approximately 20% of primary and revision Total Knee Arthroplasty (TKA) patients require multiple revisions, which are associated with poor survivorship, with worsening outcomes for subsequent revisions. For revision surgery, either endoprosthetic replacements or metaphyseal sleeves can be used for the repair, however, in cases of severe defects that are deemed “too severe” for reconstruction, endoprosthetic replacement of the affected area is recommended. However, endoprosthetic replacements have been associated with high complication rates (high incidence rates of prosthetic joint infection), while metaphyseal sleeves have a more acceptable complication profile and are therefore preferred. Despite this, no guidance exists as to the maximal limit of bone loss, which is acceptable for the use of metaphyseal sleeves to ensure sufficient axial and rotational stability. Therefore, this study assessed the effect of increasing bone loss on the primary stability of the metaphyseal sleeve in the proximal tibia to determine the maximal bone loss that retains axial and rotational stability comparable to a no defect control. Methods. to determine the pattern of bone loss and the average defect size that corresponds to the clinically defined defect sizes of small, medium and large defects, a series of pre-operative x-rays of patients with who underwent revision TKA were retrospectively analysed. Ten tibiae sawbones were used for the experiment. To prepare the bones, the joint surface was resected the typical resection depth required during a primary TKA (10mm). Each tibia was secured distally in a metal pot with perpendicular screws to ensure rotational and axial fixation to the testing machine. Based on X-ray findings, a fine guide wire was placed 5mm below the cut joint surface in the most medial region of the plateau. Core drills (15mm, 25mm and 35mm) corresponding to small, medium and large defects were passed over the guide wire allowing to act at the centre point, before the bone defect was created. The test was carried out on a control specimen with no defect, and subsequently on a Sawbone with a small, medium or large defect. Sleeves were inserted using the published operative technique, by trained individual using standard instruments supplied by the manufacturers. Standard axial pull-out (0 – 10mm) force and torque (0 – 30°) tests were carried out, recording the force (N) vs. displacement (mm) curves. Results. A circular defect pattern was identified across all defects, with the centre of the defect located 5mm below the medial tibial base plate, and as medial as possible. Unlike with large defects, small and medium sized defects reduced the pull-out force and torque at the bone-implant interface, however, these reductions were not statistically significant when compared to no bony defect. Conclusions. This experimental study demonstrated that up to 35mm radial defects may be an acceptable “critical limit” for bone loss below which metaphyseal sleeve use may still be appropriate. Further clinical assessment may help to confirm the findings of this experimental study. This study is the first in the literature to aim to quantify “critical bone loss” limit in the tibia for revision knee arthroplasty. Declaration of Interest. (a) fully declare any financial or other potential conflict of interest

Prosthetic Joint Infections (PJIs) are increasing with the use of orthopedic devices on an ageing population. Cutibacterium acnes is a commensal organism that plays an important role in the ecosystem healthy human skin, yet this species is also recognized as a pathogen in foreign body infection: endocarditis, prostatitis and specifically in PJIs. C. acnes is able to escape the immune system. This phenomenon could reflect two bacterial behaviour: the bacterial internalization by host cells and the biofilm formation. In this study, we studied different clinical strains of C. acnes. We noticed that C. acnes isolated from PJIs form 2 fold-more biofilm than the strains isolated from a normal skin in two models (Crystal violet staining and fluorescent microscopy (p=0.04 and p=0.02, respectively, Mann-Whitney test). We did not observe any difference in the internalization rate of those strains by osteoblasts. However, the quantity of biofilm formed by C. acnes before and after the internalization was compared. A significant increase in biofilm formation was observed for the strains isolated from the skin (x2.3±0.07; p=0.008, Mann-Whitney test). However, the hydrophobicity of the skin strains is significantly less important than for the PJIs strains (24.8±13% vs 56.6±12% respectively; p=0.003, Mann-Whitney test) but this did not change after internalization suggesting that there is no cell wall evolution. In conclusion, we studied for the first time the impact of bacterial internalization by osteoblasts on the virulent behaviour of C. acnes, which could explain the hided pathogenicity of this commensal bacterium

Summary. There is little knowledge in surgeons about the guidelines for prophylactic antibiotics in patients with prosthetic joints when undergoing a dental procedure. This study confirms this and there is need for robust and universal guidelines given the disastrous nature of prosthetic infection. Introduction. Infection as an indication for revision has increased to 12 % of the total revisions (NJR 9. th. report). However, it is next to impossible to find out the cause for a delayed prosthetic infection. With increasing number of arthroplasty procedures, is there a need for prophylactic antibiotics in patients with prostheses?. Methods. At London Knee Meeting 2012, a total of 163 surgeons were asked to take part in a survey. This was to find out if they knew of any existing guidelines for prophylaxis for dental procedures, if there was a need to practice more uniformly, and if they recommend such prophylaxis to their patients routinely. The grade of the surgeon and their experience in years was also noted. Results. Among the 163 surgeons who participated, 102 (62.6%) were arthroplasty surgeons. Of these, 73 (71.5%) were consultants with 3 or more years of experience. For this study, responses from these 102 surgeons were taken into consideration. Out of the 102 surgeons, only 39 (38%) were aware of AAOS recommendations. However, only 26 (25.5%) felt the need for such prophylaxis, other 37 (36%) were not sure if such prophylaxis was necessary. The remaining 39 (38.5%) did not think the prophylaxis was necessary. There was no difference found in the responses between the consultant and non-consultant surgeons. Conclusions. From this survey, it is clear that there is no uniformity of the knowledge of existing recommendations for prophylaxis of such patients with prostheses. There is probably a need to develop robust guidelines for prophylaxis, given the devastating nature of an infected prosthesis

To validate the Modified Forgotten Joint Score (MFJS) as a new patient-reported outcome measure (PROM) in hip and knee arthroplasty against the UK's gold standard Oxford Hip and Knee Scores (OHS/OKS). The original Forgotten Joint Score was created by Behrend et al to assess post-op hip/knee arthroplasty patients. It is a new assessment tool devised to provide a greater discriminatory power, particularly in the well performing patients. It measures an appealing concept; the ability of a patient to forget about their artificial joint in everyday life. The original FJS was a 12-item questionnaire, which we have modified to 10-items to improve reliability and missing data. Postal questionnaires were sent out to 400 total hip/knee replacement (THR/TKR) patients who were 1–2 years post-op, along with the OHS/OKS and a visual pain analog score. The data collected from the 212 returned questionnaires (53% return rate) was analysed in relation to construct and content validity. A sub-cohort of 77 patients took part in a test-retest repeatability study to assess reliability of the MFJS. The MFJS proved to have an increased discriminatory power in high-performing patients in comparison to the OHS and OKS, highlighted by its more normal frequency of distribution and reduced ceiling effects in the MFJS. 30.8% of patients (n=131) scored 42–48 (equivalent to 87.5–100 in the MFJS) or more in the OKS compared to just 7.69% in the MFJS TKR patients. The MFJS proved to have an increased test-retest repeatability based upon its intra-class correlation coefficient of 0.968 compared to the Oxford's 0.845. The MFJS provides a more sensitive tool in the assessment of well performing hip and knee arthroplasties in comparison to the OHS/OKS. The MFJS tests the concept of awareness of a prosthetic joint, rather than pain and function and therefore should be used as adjunct to the OKS/OHS

A three-dimensional computer model of a total hip replacement was used to examine the relationship between the position of the components, the range of motion and the prosthetic joint contact area. Horizontal acetabular positions with small amounts of acetabular and femoral anteversion provide the largest contact areas, but result in limited joint movement. These data will allow surgeons to select implant positions that will provide the largest possible joint contact area for a given joint range of motion although these are conflicting goals. In some component positions a truncated spherical prosthetic head resulted in smaller contact areas than a completely spherical head

Aseptic loosening and osteolysis around prosthetic joints are the principal causes of failure and consequent revision. During this process activated macrophages produce cytokines which are thought to promote osteolysis by osteoclasts. Changes in pressure within the space around implants have been proposed as a cause of loosening and osteolysis. We therefore studied the effect of two different regimes of cyclic pressure on the production of interleukin-1β (IL-1β), IL-6 and tumour necrosis factor-α (TNF-α) by cultured human monocyte-derived (M-D) macrophages. There was a wide variation in the expression of cytokines in non-stimulated M-D macrophages from different donors and therefore cells from the same donor were compared under control and pressurised conditions. Both regimes of cyclic pressure were found to increase expression of IL-6 and TNF-α. Expression of IL-1β was increased by a higher-frequency regime only. Our findings suggest that M-D macrophages are activated by cyclic pressure. Further work will be required to understand the relative roles of frequency, amplitude and duration of applied pressure in the cellular effects of cyclic pressure in this system

Objectives

The objective of this study was to develop a test for the rapid (within 25 minutes) intraoperative detection of bacteria from synovial fluid to diagnose periprosthetic joint infection (PJI).

High-intensity narrow-spectrum (HINS) light is a novel violet-blue light inactivation technology which kills bacteria through a photodynamic process, and has been shown to have bactericidal activity against a wide range of species. Specimens from patients with infected hip and knee arthroplasties were collected over a one-year period (1 May 2009 to 30 April 2010). A range of these microbial isolates were tested for sensitivity to HINS-light. During testing, suspensions of the pathogens were exposed to increasing doses of HINS-light (of 123mW/cm² irradiance). Non-light exposed control samples were also used. The samples were then plated onto agar plates and incubated at 37°C for 24 hours before enumeration. Complete inactivation (greater than 4-log₁₀ reduction) was achieved for all of the isolates. The typical inactivation curve showed a slow initial reaction followed by a rapid period of inactivation. The doses of HINS-light required ranged between 118 and 2214 J/cm². Gram-positive bacteria were generally found to be more susceptible than Gram-negative.

As HINS-light uses visible wavelengths, it can be safely used in the presence of patients and staff. This unique feature could lead to its possible use in the prevention of infection during surgery and post-operative dressing changes.

Cite this article: Bone Joint J 2015;97-B:283–8.