Prosthetic Joint Infection (PJI) is a devastating complication that can occur after total joint replacement surgery. With increasing antimicrobial resistance, there is a need for non-antibiotic approaches to treat and prevent PJI. Doping calcium phosphates with antimicrobial ions shows promise for these purposes. This systematic review aims to search and summarise the evidence-base for the potential of calcium phosphates doped with different antimicrobial ions.

A systematic review was conducted on PubMed, Embase, Web-Of-Science, Cochrane Library and Emcare of in vitro and animal studies on the antimicrobial activity of (co)substituted calcium phosphates according to PRIMSA guidelines.. The research protocol, listing search terms and in/exclusion criteria, was registered a priori at https://doi.org/10.7910/DVN/HEP18U. Data was extracted regarding ions, micro-organisms and antimicrobial activity.

The search retrieved 1017 hits of which 148 papers were included. The substitution of 33 different ions was reported. Silver (n= 46), zinc (n=39), copper (n=18) and magnesium (n=14) were the most commonly doped ions. 36 different micro-organisms were studied of which E. coli (n=109), S. aureus (n=99), and C. albicans (n=22) were the most common. 6 different outcomes were reported, most commonly the K-ratio (n=53), the log CFU (n=41) and the bacterial inhibition zone (n=39). A validated outcome for the evaluation of biofilm prevention was lacking.

There was considerable heterogeneity in studied ions, micro-organisms and reported outcomes. A lack of clearly defined reporting guidelines in the field of antimicrobial materials has led to the use of clinically irrelevant micro-organisms and a general lack of consistency of the methods used and the reported results. Currently, there is no universally accepted measure for the effectiveness required from biomaterials for treatment and prevention of PJI.

Aims

The aim of this meta-analysis is to assess the association between exchange of modular parts in debridement, antibiotics, and implant retention (DAIR) procedure and outcomes for hip and knee periprosthetic joint infection (PJI).

The main problem of infected orthopaedic implants is that the presence of microorganisms in an organized biofilm making them difficult accessible for antibiotics. This biofilm consists of a complex community of microorganisms embedded in an extracellular matrix that forms on surfaces such as an implant. Non-contact induction heating uses pulsed electromagnetic fields to induce so-called ‘eddy currents’ within metal objects which causes them to heat up. This heat causes thermal damage to the bacterial biofilm hence killing the bacteria on the metal implant. The purpose of this study is to determine the effectiveness of induction heating on killing Staphylococcus epidermidis in a biofilm. S. epidermidis biofilms were grown on Titanium alloy (Ti6Al4V) coupons and subsequently were heated with a custom-built induction heater to temperatures of 60°C, 70°C, 80°C and 90°C for 3.5 minutes. Temperature was controlled with an infra-red thermal sensor and micro-controller. We also included two control conditions without induction heating: C1 without induction heating and C2 with chlorhexidine 0.5% in 70% alcohol without induction heating. Experiments were repeated 5 times. In the C1 group (no induction heating), 1.3 * 10(7) colony forming units (CFU)/cm(−2) of S. epidermidis were observed. For 60°C, 70C, 80 C and 90C, a 3.9-log reduction, 5.3-log reduction, 5.5-log reduction and 6.1-log reduction in CFU/cm(−2) were observed, respectively. For the C2 (chlorhexidine) there was a 6.7-log reduction CFU/cm(-2). We concluded that induction heating of Titanium coupons is effective in reducing bacterial load in vitro for S. epidermidis biofilms.

Introduction

The Kaplan Meier estimator is widely used in orthopedics. In situations where another event prevents the occurrence of the event of interest, the Kaplan Meier estimator is not appropriate and a competing risks model has to be applied. We questioned how much bias is introduced by erroneous use of the Kaplan Meier estimator instead of a competing risks model in a hip revision surgery cohort.

We present the rationale and design of the DynaPort KneeTest. The test aims at measuring knee patients’ functional abilities in an unobtrusive, user-friendly way. Test persons wear several belts around their trunk and legs. The belts contain accelerometers, the signals of which are stored in a recorder, embedded in one of the belts. The knee test consists of a set of 29 tasks related to activities of daily life (“test items”). Accelerometer signals are analysed in terms of 30 “movement features” (accelerations, angles, durations, frequencies, and some dimensionless numbers). In data analysis, the beginning and end of each test item is marked by hand; otherwise, analysis is automatic.

We compared 140 knee patients with 32 healthy controls and found 541 of the 29 x 30 =870 test item movement feature combinations differed significantly between the two groups. From these 541 combinations the DynaPort knee score is calculated by the weighted averages of movement features per item, then weighted averages of items per cluster (locomotion, rising and descending, transfers, lifting and moving objects), and finally the average of the clusters. In an initial study the test-retest reliability of the knee test proved high, and the test turned out to be sufficiently responsive (0.7 patients’ standard deviations improvement after 24 months). However, it remains difficult to interpret the scores in more meaningful terms than merely “better” or “worse”. Extensive reliability studies in the future will further assess the validity of the test and provide more insight into the meaning of the scores.

The DynaPort knee test may thus become an important instrument for evaluating patients’ functional abilities in knee-related clinical practice and research.