The purpose of this study was to compare the diagnostic accuracy for the detection of infection between the culture of fluid obtained by sonication (SFC) and the culture of peri-implant tissues (PITC) in patients with early and delayed implant failure, and those with unsuspected and suspected septic failure. It was hypothesised that SFC increases the diagnostic accuracy for infection in delayed, but not early, implant failure, and in unsuspected septic failure. The diagnostic accuracy for infection of all consecutive implants (hardware or prostheses) that were removed for failure was compared between SFC and PITC. This prospective study included 317 patients with a mean age of 62.7 years (9 to 97). The sensitivity for detection of infection using SFC was higher than using PITC in an overall comparison (89.9% versus 67%, respectively; p < 0.001), in unsuspected septic failure (100% versus 48.5%, respectively; p < 0.001), and in delayed implant failure (88% versus 58%, respectively; p < 0.001). PITC sensitivity dropped significantly in unsuspected compared with suspected septic failure (p = 0.007), and in delayed compared with early failure (p = 0.013). There were no differences in specificity.

Sonication is mainly recommended when there is implant failure with no clear signs of infection and in patients with delayed implant failure. In early failure, SFC is not superior to PITC for the diagnosis of infection and, therefore, is not recommended as a routine diagnostic test in these patients.

Cite this article: Bone Joint J 2013;95-B:244–9.

Aims

A higher failure rate has been reported in haematogenous periprosthetic joint infection (PJI) compared to non-haematogenous PJI. The reason for this difference is unknown. We investigated the outcome of haematogenous and non-haematogenous PJI to analyze the risk factors for failure in both groups of patients.

This prospective study evaluates the role of new laboratory markers in the diagnosis of deep implant infection in 78 patients (41 men and 37 women) with a revision total knee or hip replacement. The mean age at the time of operation was 64.0 years (19 to 90). Intra-operative cultures showed that 21 patients had a septic and 57 an aseptic total joint replacement. The white blood cell count, the erythrocyte sedimentation rate and levels of C-reactive protein, interleukin-6, procalcitonin and tumour necrosis factor (TNF)-α were measured in blood samples before operation. The diagnostic cut-off values were determined by Received Operating Characteristic curve analysis. C-reactive protein (> 3.2 md/dl) and interleukin-6 (> 12 pg/ml) have the highest sensitivity (0.95). Interleukin-6 is less specific than C-reactive protein (0.87 vs 0.96). Combining C-reactive protein and interleukin-6 identifies all patients with deep infection of the implant. Procalcitonin (> 0.3 ng/ml) and TNF-α (> 40 ng/ml) are very specific (0.98 vs 0.94) but have a low sensitivity (0.33 vs 0.43). The combination of C-reactive protein and interleukin-6 measurement provide excellent screening tests for infection of a deep implant. A highly specific marker such as procalcitonin and pre-operative aspiration of the joint might be useful in identifying patients with true positive C-reactive protein and/or interleukin-6 levels

We have assessed the different adhesive properties of some of the most common bacteria associated with periprosthetic joint infection on various types of ultra high molecular Weight Polyethylene (UHMWPE). Quantitative in vitro analysis of the adhesion of biofilm producing strains of Staphylococcus aureus and Escherichia coli to physically and chemically characterised standard UHMWPE (PE), vitamin E blended UHMWPE (VE-PE) and oxidised UHMWPE (OX-PE) was performed using a sonication protocol. A significant decreased bacterial adhesion was registered for both strains on VE-PE, in comparison with that observed on PE, within 48 hours of observation (S. aureus p = 0.024 and E. coli p = 0.008). Since Vitamin E reduces bacterial adhesive ability, VE-stabilised UHMWPE could be valuable in joint replacement by presenting excellent mechanical properties, while reducing bacterial adhesiveness.

Cite this article: Bone Joint J 2014;96-B:497–501.

The aim of this study was to evaluate whether coating titanium discs with selenium in the form of sodium selenite decreased bacterial adhesion of Staphylococcus aureus and Staph. epidermidis and impeded osteoblastic cell growth.

In order to evaluate bacterial adhesion, sterile titanium discs were coated with increasing concentrations of selenium and incubated with bacterial solutions of Staph. aureus (ATCC 29213) and Staph. epidermidis (DSM 3269) and stained with Safranin-O. The effect of selenium on osteoblastic cell growth was also observed. The adherence of MG-63 cells on the coated discs was detected by staining with Safranin-O. The proportion of covered area was calculated with imaging software.

The tested Staph. aureus strain showed a significantly reduced attachment on titanium discs with 0.5% (p = 0.011) and 0.2% (p = 0.02) selenium coating. Our test strain from Staph. epidermidis showed a highly significant reduction in bacterial adherence on discs coated with 0.5% (p = 0.0099) and 0.2% (p = 0.002) selenium solution. There was no inhibitory effect of the selenium coating on the osteoblastic cell growth.

Selenium coating is a promising method to reduce bacterial attachment on prosthetic material.

Cite this article: Bone Joint J 2013;95-B:678–82.

Primary arthroplasty may be denied to very elderly patients based upon the perceived outcome and risks associated with surgery. This prospective study compared the outcome, complications, and mortality of total hip (TKR) and total knee replacement (TKR) in a prospectively selected group of patients aged ≥ 80 years with that of a control group aged between 65 and 74 years. There were 171 and 495 THRs and 185 and 492 TKRs performed in the older and control groups, respectively. No significant difference was observed in the mean improvement of Oxford hip and knee scores between the groups at 12 months (0.98, (95% confidence interval (CI) −0.66 to 2.95), p = 0.34 and 1.15 (95% CI −0.65 to 2.94), p = 0.16, respectively). The control group had a significantly (p = 0.02 and p = 0.04, respectively) greater improvement in the physical well being component of their SF-12 score, but the older group was more satisfied with their THR (p = 0.047). The older group had a longer hospital stay for both THR (5.9 versus 9.0 days, p < 0.0001) and TKR (6.2 versus 8.3 days, p < 0.0001). The rates of post-operative complications and mortality were increased in the older group.

Allografts of bone from the femoral head are often used in orthopaedic procedures. Although the donated heads are thoroughly tested microscopically before release by the bone bank, some surgeons take additional cultures in the operating theatre before implantation. There is no consensus about the need to take these cultures. We retrospectively assessed the clinical significance of the implantation of positive-cultured bone allografts. The contamination rate at retrieval of the allografts was 6.4% in our bone bank. Intra-operative cultures were taken from 426 femoral head allografts before implantation; 48 (11.3%) had a positive culture. The most frequently encountered micro-organism was coagulase-negative staphylococcus. Deep infection occurred in two of the 48 patients (4.2%). In only one was it likely that the same micro-organism caused the contamination and the subsequent infection.

In our study, the rate of infection in patients receiving positive-cultured allografts at implantation was not higher than the overall rate of infection in allograft surgery suggesting that the positive cultures at implantation probably represent contamination and that the taking of additional cultures is not useful.