Aim. Antibiotic-eluting calcium compounds can be used to deliver antibiotics in the management of prosthetic joint infection (PJI). Described omplications include wound drainage, heterotopic ossification(HO) as well as hypercalcaemia which is potentially life threatening. The aim of this study is to assess the incidence of hypercalcaemia and other complications between two calcium based antibiotic delivery systems. Method. A retrospective study was performed. Thirty two patients treated with Stimulan or Cerament Calcium based antibiotic delivery system between August 2014 to January 2017 were included. Seven patients received Cerament, 21 cases received Stimulan and one patient received both. The volume used as well as pre- and post-operative serum calcium were recorded as well as any wound related complications and radiologic changes suggestive of heterotopic ossification. The postoperative serum adjusted Calcium were taken weekly during the initial post operative period. Patients with overactive parathyroid disease and pre-existing renal disease were excluded. Results. Stimulan group (n=22, Mean volume 39.2ml). Mean pre-operative serum calcium was 2.48mmol/l. At 1 and 2 weeks post-surgery mean levels were 2.51 and 2.47mmol/l (patients receiving <40ml), and 2.47 and 2.50mmol/l (patients receiving >40ml – 9 cases) respectively. There was no significant difference between pre/post-operative levels at 1 (p=0.97) or 2 weeks (p=0.91) and no difference between those treated with <40ml or >40ml of Stimulan at 1 or 2 weeks (p=0.91). Cerament group (n=8, Mean volume 9.4ml). Mean pre-operative serum calcium was 2.42mmol/l. Mean post-operative levels at 1 and 2 weeks post-surgery were 2.44mmol/l (p=0.92) and 2.37mmol/l (p=0.61) respectively. One patient had prolonged wound discharge and required re operation. No HO was encountered. Conclusions. Our results suggest that hypercalcaemia and other complications are uncommon with the use calcium based antibiotic delivery systems and that calcium based antibiotic delivery systems are safe in the treatment of PJI

Introduction. When third body particles originating from bone cement or bone void fillers become trapped between articulating surfaces of joint replacements, contact surfaces may be damaged leading to accelerated wear and premature failure of the implant. In this study, the damage to cobalt chrome counterfaces by third body particles from PMMA bone cement (GMV, DePuy) and various bone void fillers was investigated; then wear tests of UHMWPE were carried out against these surfaces. Methods. Third body particles of polymerised GMV bone cement and the bone void fillers; OsteoSet (with tobramycin), Stimulan and Stimulan+ (with vancomycin and tobramycin) (provided by Biocomposites Ltd.) were trapped between an UHMWPE pin and a highly polished cobalt chrome plate. A load of 120N was applied to the pin and using an Instron materials testing machine, the plate was pulled beneath the pin to recreate third body damage [1]. The resulting surface topography of the plate was analysed using white light interferometry (Bruker NPFLEX). Pin on plate wear tests of GUR 1020 UHMWPE pins were carried out against the plates perpendicular to the direction of damage for 500,000 cycles in 25% bovine serum using a 6-station multi-axial reciprocating rig under conditions to replicate the kinematics in total knee replacement. Wear of the pins was determined by gravimetric analysis and results were compared to negative (highly polished) control plates and positive controls scratched with a diamond stylus (lip height 2µm). Statistical analysis was carried out using one-way ANOVA with significance taken at p<0.05. Results. Following damage simulation with Stimulan and Stimulan+, no scratches could be seen on the surface of the cobalt chrome plates using a stereomicroscope under 63× magnification (Figure 1). Table 1 shows that OsteoSet caused surface damage with the highest density of scratches, which had a greater mean lip height than those caused by the other third body materials. Stimulan+ caused significantly (p=0.002) fewer scratches than Osteoset and the surface damage caused by Stimulan was below the resolution of the surface analysis measurement technique used. The pin on plate wear test showed that under the test conditions used, the wear of UHMWPE was similar (p=0.108) for negative control plates and plates scratched with third body particles and a significant (p<0.001) increase in wear was only observed against the positive control plates [2]. Discussion. This study shows that third body particles originating from bone cement and bone void fillers can damage the surface of highly polished cobalt chrome plates and that materials of similar composition can cause varying severity of damage. Wear tests against plates damaged with third body particles did not significantly affect the wear of UHMWPE and to significantly increase wear, scratches needed to have a lip height of 2µm or above

Introduction. Osteomyelitis (OM) is a challenging condition to diagnose and treat. The multidisciplinary team (MDT) approach is used in managing complex diseases such as cancer and diabetes. The Hull Regional Bone Infection MDT team was established to provide coordinated care for patients suspected to have OM. This study reviews the orthoplastic treatment and outcomes of patients with non-periprosthetic OM. Materials and Methods. Retrospective review of patients presenting to the MDT team who had orthoplastic intervention with debridement and flap coverage between 1/6/2014 - 30/11/2018. We describe our MDT approach of assessment, planning for surgical intervention and antibiotic protocol. Data was obtained from electronic and paper patient records, and PACS. Results. Twenty-nine patients were identified (75.9% male). Mean age was 52.7 (23–82). Median duration of symptoms at surgery was 10 months (IQR 4.0–34.3). Cierny-Mader (CM) Host Type B. (L). (41.4%), type B. (S). (34.5%), and type B. (S+L). (17.2%). Twenty-four patients (82.8%) were CM anatomical class IV. Twenty-four patients (82.8%) had single-stage surgical treatment. Twenty-one patients received 23 free flaps. Anterolateral thigh flap (9/23) and gracilis muscle flap (7/23) were most commonly used. Tibialis anterior flap was the most commonly used local flap. Stimulan was used in 65.5%. Staphylococcus aureus was seen in 60% of patients. Mean follow-up time was 21 months (1–62). There were 2 (6.9%) OM recurrence. Both patients were CM anatomical class IV. Conclusions. Our study showed that our MDT management of patients with OM can achieve a low recurrence rate despite a high proportion of patients with severe OM. We recommend considering an MDT approach for these complex OM patients

Bone and joint infections of the lower limbs cause significant morbidity for patients. Infection is a devastating complication for prosthetic joint replacements. In this large case series from a single centre in the NE of England, we present our experience of using antibiotic impregnated dissolvable synthetic pure calcium sulphate beads [Stimulan R]1 for local elution of antibiotics at the site of infection. At our centre, from August 2012 to Jan 2015, antibiotic impregnated dissolvable synthetic pure calcium sulphate beads [Stimulan R]1 was used for local elution of antibiotics in 45 patients with lower limb bone or joint infections. Tailored plans were made by Orthopedic surgeon and Microbiologist MDTs based on bacteria and sensitivities. Cases included 20 THR, 13 TKR, 5 Hemiarthroplasties, 4 tibial nonunions, 1 infected femoral plate and 2 paediatric osteomyelitis. Organisms isolated – Coagulase negative Staphs, Staph aureus, MRSA, E coli, Enterococcus, Enterobacter cloacae, Serratia and 1 Salmonella typhimurium!!. In our cases, a combination of Vancomycin and Gentamicin was added to Stimulan beads following manufacturer's mixing guide. In 2 cases, we added Ceftazidime to the beads and Daptomycin in 1 case. In bone infections, surgical debridement and systemic antibiotics were also needed. All arthroplasty infections underwent explantation with addition of antibiotic impregnated beads either at single stage or both stages of 2 stage revisions and systemic antibiotics. Follow up (ranging 9months to 2 years) indicates no failure so far. The beads caused no excessive wound drainage. There was no need to remove beads as they dissolve. In the cases where a staged revision was performed, the beads were inserted at first stage and there was microbiological clearance of infection at 2nd stage. Our series includes some experince in paediatric cases too. As far as we are aware, this is the largest series in the UK from a single centre reporting experience with Stimulan in infected bone and joints of the lower limbs. Our experience suggests use of dissolvable pure Calcium sulphate beads impregnated with carefully selected antibiotics, works as an effective adjunct to current treatments and offers flexibility with choice of antiobiotics that can be added locally. Acknowledgements. Biocomposites UK for supporting attendance at EBJIS. Authors control ownership of all data and analysis

Aim. Bacterial biofilms play a key role in prosthetic infection (PI) pathogenesis. Establishment of the biofilm phenotype confers the bacteria with significant tolerance to systemic antibiotics and the host immune system meaning thorough debridement and prosthesis removal often remain the only possible course of treatment. Protection of the prosthesis and dead-space management may be achieved through the use of antibiotic loaded cements and beads to release high concentrations of antibiotics at the surgical site. The antibacterial and antibiofilm efficacy of these materials is poorly understood in the context of mixed species models, such as are often encountered clinically. Methods. A P. aeruginosa and S. aureus in vitro co-culture biofilm model was grown using 1/5th BHI supplemented with 20 µM hemin. The ability of beads made from a synthetic calcium sulfate (CaSO4) loaded with vancomycin, tobramycin and vancomycin & tobramycin in combination to prevent biofilm formation and kill established co-culture biofilms were assessed using viable cell counts and confocal scanning laser microscopy (CSLM) over a 7 day time course. To assay for genetic changes to the individual species as a result of their presence together within a biofilm, mutation rates were measured using fluctuation analysis following growth as planktonic and biofilm cultures, alone or in co-culture. Mutants were determined based on their ability to grow on agar plates containing an inhibitory concentration of rifampicin. Mutation rates were calculated using the Ma-Sandri-Sarkar Maximum Likelihood Estimator and 94% confidence intervals compared for significance. Results. Mixed species biofilms displayed differential sensitivity to vancomycin alone and tobramycin alone CaSO4-loaded beads relative to single species biofilms. Preliminary data suggests 10- and 100-fold increase in mutation rates of P. aeruginosa and S. aureus, respectively, when in a co-culture relative to monospecies biofilm which, while further work is needed, may directly or indirectly contribute to the differing antibiotic sensitivities observed. A broad-spectrum intervention of CaSO4-loaded vancomycin & tobramycin beads was able to prevent bacterial colonisation and attenuate P. aeruginosa and S. aureus mixed species biofilm formation for multiple days. Conclusions. Synthetic antibiotic-loaded CS beads, with a broad-spectrum antibiotic combination, have potential to reduce or eliminate mixed species biofilm formation on implant material by providing locally high concentrations over sufficient time periods to aid in the management of PIs. * Stimulan, Biocomposites Ltd

Aims

The standard of wide tumour-like resection for chronic osteomyelitis (COM) has been challenged recently by adequate debridement. This paper reviews the evolution of surgical debridement for long bone COM, and presents the outcome of adequate debridement in a tertiary bone infection unit.