Evaluation of two sources of calcium sulfate for a local drug delivery system: a pilot study

Proceedings of the United Kingdom Periprosthetic Joint Infection Meeting 2022: Fracture-Related Infection Session

Implant-related infections represent a relatively common and significant challenge in the surgical management of musculoskeletal trauma patients. The third United Kingdom Periprosthetic Joint Infection (UK PJI) Meeting convened in Glasgow on 1 April 2022, and brought together over 180 delegates, representing orthopaedics, infectious diseases, microbiology, plastic surgery, anaesthetics, and allied health professions, including pharmacy and specialist nurses. The meeting comprised a plenary session for all delegates, and separate breakout sessions for fracture-related infection (FRI) and arthroplasty. The UK PJI working group prepared consensus statements in advance of each session, based upon topics that were discussed at previous meetings, and delegates engaged in an anonymous electronic voting process. This article presents the findings of the FRI session, and examines each consensus topic within the context of the contemporary literature.

Antibiotic calcium sulphate beads lower the bacterial burden and prevent infection in a mouse model of periprosthetic joint infection

Aims

Delayed postoperative inoculation of orthopaedic implants with persistent wound drainage or bacterial seeding of a haematoma can result in periprosthetic joint infection (PJI). The aim of this in vivo study was to compare the efficacy of vancomycin powder with vancomycin-eluting calcium sulphate beads in preventing PJI due to delayed inoculation.

Methods

A mouse model of PJI of the knee was used. Mice were randomized into groups with intervention at the time of surgery (postoperative day (POD) 0): a sterile control (SC; n = 6); infected control (IC; n = 15); systemic vancomycin (SV; n = 9); vancomycin powder (VP; n = 21); and vancomycin bead (VB; n = 19) groups. Delayed inoculation was introduced during an arthrotomy on POD 7 with 1 × 105 colony-forming units (CFUs) of a bioluminescent strain of Staphylococcus aureus. The bacterial burden was monitored using bioluminescence in vivo. All mice were killed on POD 21. Implants and soft-tissue were harvested and sonicated for analysis of the CFUs.

Results

The mean in vivo bioluminescence in the VB group was significantly lower on POD 8 and POD 10 compared with the other groups. There was a significant 1.3-log10 (95%) and 1.5-log10 (97%) reduction in mean soft-tissue CFUs in the VB group compared with the VP and IC groups (3.6 × 103 vs 7.0 × 104; p = 0.022; 3.6 × 103 vs 1.0 × 105; p = 0.007, respectively) at POD 21. There was a significant 1.6-log10 (98%) reduction in mean implant CFUs in the VB group compared with the IC group (1.3 × 100 vs 4.7 × 101, respectively; p = 0.038). Combined soft-tissue and implant infection was prevented in 10 of 19 mice (53%) in the VB group as opposed to 5 of 21 (24%) in the VP group, 3 of 15 (20%) in the IC group, and 0% in the SV group.

Conclusion

In our in vivo mouse model, antibiotic-releasing calcium sulphate beads appeared to outperform vancomycin powder alone in lowering the bacterial burden and preventing soft-tissue and implant infections.

Staged Treatment of Posttraumatic Tibial Osteomyelitis with Rib Graft and Serratus Anterior Muscle Autografts-Case Report

Osteomyelitis of the tibia is a challenging condition, particularly when it occurs as a result of trauma. This abstract presents a case study detailing the successful staged treatment of posttraumatic tibial osteomyelitis utilizing a unique combination of rib graft and serratus anterior muscle. This medical abstract presents a case study of a 52-year-old male with a history of heavy smoking and obliterating arteriopathy of the lower limbs. The patient sustained a traumatic open fracture classified as Type IIIA Gustilo Anderson involving one-third of the distal right tibia diaphysis, with an associated right fibular malleolus fracture. The treatment approach comprised multiple stages, focusing on wound management, infection control, and limb salvage. The initial stage involved the application of an external fixation device in the emergency setting. Seven days later, an osteosynthesis procedure was performed using a Kuntscher nail and wire cerclage. However, complications emerged, with wound dehiscence and purulent secretion observed at 14 days postsurgery. Subsequently, secondary suturing was carried out at the 20-day mark. The second stage of the treatment involved implant removal, wide excisional debridement, pulse lavage, osteoclasia, and relaxation of the peroneal malleolus. A monoplane external fixation system was applied. As a part of postoperative care, aspiration therapy with a vacuum pump was administered, along with a 10-day course of vancomycin according to the antibiogram. Positive clinical signs of healing were noted, and sterile cultures confirmed the results. The third stage of the intervention focused on grafting the osteo-muscular defect, utilizing autografts from the rib and serratus anterior muscle. The external fixator was maintained in place during this phase. In the fourth and final stage, after an 8-week integration period of the musculocutaneous flap, the external fixator was removed, and internal fixation was accomplished with a blocked Less Invasive Stabilization System (LISS) plate inserted using the Minimally Invasive Plate Osteosynthesis (MIPO) technique. This case underscores the significance of a multistage approach in managing complex limb injuries, emphasizing the importance of timely intervention, infection control, and innovative techniques for limb salvage and restoration of function.

Elution profiles of metronidazole from calcium sulfate beads

BACKGROUND

Antibiotic beads are used to treat local bacterial infections by delivering high drug concentrations to infected tissue.

OBJECTIVES

This study examined the elution characteristics of metronidazole from metronidazole-calcium sulfate (MCa) and metronidazole-calcium-potassium sulfate (MCaK) beads over 20 days and the antibacterial efficacy of the beads after storage.

METHODS

The MCa and MCaK beads were prepared by mixing 250 mg of metronidazole and 10 g of calcium sulfate hemihydrate with water and a 3% potassium sulfate solution, respectively. The beads were placed in phosphate-buffered saline for the elution study. The metronidazole eluents were determined using high-performance liquid chromatography. The microstructures were examined by scanning electron microscopy (SEM), and the antimicrobial activity was evaluated by a microbioassay.

RESULTS

For the 20-day study, the total amount of metronidazole released was greater in the MCa beads than in the MCaK beads by 6.61 ± 0.48 mg (89.11% ± 3.04%) and 4.65 ± 0.36 mg (73.11% ± 4.38%), respectively. The amounts of eluted drugs from the MCa and MCaK beads were higher than the minimum inhibitory concentration at 0.5 µg/mL against anaerobic bacteria at both 20 days and 14 days. SEM showed that calcium crystals on the outer surface had dissolved after elution, and thinner calcium crystals were prominent in the MCaK beads. The MCa and MCaK beads exhibited antibacterial activity after setting, followed by storage at room temperature or 4°C for 21 days.

CONCLUSIONS

The MCa beads could release more drug than the MCaK beads, but all eluted metronidazole amounts were effective in controlling bacterial infections. Both metronidazole beads could be stored at ambient temperature or in a refrigerator.

Analysis of risk factors for serous exudation of biodegradable material calcium sulfate in the treatment of fracture-related infections

Objective: To explore the related risk factors of serous exudation after antibiotic-loaded calcium sulfate treatment of fracture-related infections and to provide a theoretical basis for clinical treatment and prevention of serous exudation complications. Methods: The clinical data of 145 patients with limb fracture-related infection treated with antibiotic-loaded calcium sulfate in Xi'an Honghui Hospital from January 2019 to December 2022 were retrospectively analyzed. All patients were diagnosed with fracture-related infection by preoperative magnetic resonance examination, bacterial culture and gene detection and received antibiotic-loaded calcium sulfate implantation. The postoperative serous exudation was recorded through hospitalization observation, outpatient review or follow-up. The collected clinical data were sorted out, and the patient data were divided into serous exudation groups and non-exudation groups. Firstly, the clinical data of the two groups were compared by single-factor analysis to screen out the risk factors. Then multivariate binary Logistic regression analysis determined the independent risk factors and protective factors. Results: 1) According to the inclusion and exclusion criteria, there were 145 cases with complete clinical data, including 27 cases in the non-infectious exudation group and 118 cases in the non-exudative group; 2) Univariate analysis showed that the history of diabetes, smoking history, calcium sulfate implantation, drainage time, combined flap surgery, geometric shape of implanted calcium sulfate, and thickness of soft tissue covered by the surgical area were all associated with the occurrence of non-infectious exudation after antibiotic-loaded calcium sulfate implantation (p < 0.05); 3) The amount of implanted calcium sulfate was more [OR = 5.310, (1.302-21.657), p = 0.020], combined with flap surgery [OR = 3.565, (1.195-10.641), p = 0.023], and the thickness of soft tissue coverage in the operation area was thinner [OR = 5.305, (1.336-21.057), p = 0.018]. Longer drainage time [OR = 0.210, (0.045-0.967), p = 0.045] was a protective factor for non-infectious exudation after antibiotic-loaded calcium sulfate implantation. Conclusion: 1) The probability of serous exudation in patients with fracture-associated infection after antibiotic-loaded calcium sulfate surgery was 18.62%. This complication may cause a heavier economic and psychological burden on patients; 2) With the increase of bone infection area and the application of more calcium sulfate, the incidence of serous exudation after antibiotic-loaded calcium sulfate surgery in patients with the fracture-related infection will increase, so we should use the amount of calcium sulfate reasonably on the premise of sufficient control of infection in clinical work, and the incidence of serous exudation will also increase due to the recent skin flap surgery and the thinner soft tissue coverage of calcium sulfate implantation area; 3) Under the premise of being able to drain the drainage from the surgical area, the longer drainage time of the drainage tube has a positive effect on preventing the occurrence of serous exudation.

Injectable Synthetic Beta-Tricalcium Phosphate/Calcium Sulfate (GeneX) for the Management of Contained Defects Following Curettage of Benign Bone Tumours

Benign and low-grade malignant bone tumours are often treated with curettage and filling of the resultant defect using any of a number of materials, including autologous bone grafts, allografts, or synthetic materials. The objective of this study was to report our experience using a synthetic bone graft substitute in these patients. Ten consecutive cases (four males, six females; mean age, 36 years) of benign bone tumours were treated surgically at a tertiary musculoskeletal oncology centre, between 2019 and 2021. Following curettage, the contained defects were managed with injectable beta-tricalcium phosphate/calcium sulfate (GeneX; Biocomposites Ltd., Keele, UK). The desired outcomes were early restoration of function and radiographic evidence of healing. No other graft materials were used in any of the patients. The mean follow-up was 24 months (range, 20–30 months). All patients in this series (100%) demonstrated radiographic evidence of healing and resumed their daily living activities. There were no tumour recurrences and no complications were encountered with the use of GeneX. In patients with contained defects following curettage of benign bone tumours, we found GeneX to be a safe and effective filling agent. These findings contrast with some existing studies that have reported local complications with the use of injectable beta-tricalcium phosphate/calcium sulfate.

Can Amoxicillin and Clavulanic Acid Impregnated Plaster of Paris Beads Serve as an Effective Alternative to Systemic Antibiotics for Third Molar Surgeries? A Split Mouth Randomized Clinical Trial

Purpose

The present work was a pilot study undertaken to evaluate the effectiveness of amoxicillin and clavulanic acid impregnated plaster of paris beads for prevention of infection of third molar extraction sockets.

Materials and Methods

This was a prospective, randomized, split mouth clinical trial done on 16 patients (32 sites) who required surgical extraction of mandibular third molars. Control arm patients were given Tab. amoxicillin 500 mg with clavulanic acid 125 mg (Tab. Klavimed 625 mg, Indomed, India), thrice daily for 3 days after extraction, whereas test arm patients received Antibiotic Impregnated Microbeads (AIM), containing Amoxicillin 500 mg and Clavulanic Acid 100 mg placed in situ in the extraction socket. The primary outcome parameter was infection and the secondary outcome parameters were pain, trismus, swelling and wound healing.

Results

None of the patients in either group had post operative infection. There was no significant difference in pain intensity between the two groups (1st day p = 0.41; 3rd day p = 0.38, 7th day p = 0.37). Both the groups were also similar with respect to swelling (p = 0.596, 0.146, 0.871, 0.820 on 1st, 3rd, 7th, 15th post-op day ,respectively).

Conclusion

Amoxycillin with clavulanic acid impregnated PoP beads appears to be as effective as oral 3 day amoxicillin with clavulanic acid regime for prevention of 3 M socket infection.

Identifying alternative antibiotics that elute from calcium sulfate beads for treatment of orthopedic infections

There has been increasing interest in the use of a synthetic absorbable calcium sulfate (CaSO₄ ) for local antibiotic delivery in orthopaedic infections. The purpose of this study was to quantify elution kinetics of six antibiotics (amikacin, meropenem, fosfomycin, minocycline, cefazolin, and dalbavancin) from a clinically relevant CaSO₄ bead model and compare elution and antimicrobial activity to the current clinical gold standards: vancomycin and tobramycin. Antibiotic-loaded synthetic CaSO₄ beads were immersed in phosphate buffered saline and incubated at 37°C. Eluent was harvested at eight time points over 28 days. Antibiotic concentrations were measured by high performance liquid chromatography to quantify elution rates. CaSO₄ beads demonstrated burst release kinetics. Dalbavancin, cefazolin, and minocycline all demonstrated similar elution profiles to vancomycin. Amikacin and meropenem demonstrated favorable elution profiles and durations of above-minimum inhibitory concentration when compared to tobramycin. Clinical Significance: This study provides important novel data regarding the utility of amikacin, meropenem and dalbavancin as alternative choices to place in CaSO₄ carriers when treating orthopaedic infections.

Elution Kinetics from Antibiotic-Loaded Calcium Sulfate Beads, Antibiotic-Loaded Polymethacrylate Spacers, and a Powdered Antibiotic Bolus for Surgical Site Infections in a Novel In Vitro Draining Knee Model

Antibiotic-tolerant bacterial biofilms are notorious in causing PJI. Antibiotic loaded calcium sulfate bead (CSB) bone void fillers and PMMA cement and powdered vancomycin (VP) have been used to achieve high local antibiotic concentrations; however, the effect of drainage on concentration is poorly understood. We designed an in vitro flow reactor which provides post-surgical drainage rates after knee revision surgery to determine antibiotic concentration profiles. Tobramycin and vancomycin concentrations were determined using LCMS, zones of inhibition confirmed potency and the area under the concentration-time curve (AUC) at various time points was used to compare applications. Concentrations of antibiotcs from the PMMA and CSB initially increased then decreased before increasing after 2 to 3 h, correlating with decreased drainage, demonstrating that concentration was controlled by both release and flow rates. VP achieved the greatest AUC after 2 h, but rapidly dropped below inhibitory levels. CSB combined with PMMA achieved the greatest AUC after 2 h. The combination of PMMA and CSB may present an effective combination for killing biofilm bacteria; however, cytotoxicity and appropriate antibiotic stewardship should be considered. The model may be useful in comparing antibiotic concentration profiles when varying fluid exchange is important. However, further studies are required to assess its utility for predicting clinical efficacy.

Evaluation of comparative soft tissue response to bone void fillers with antibiotics in a rabbit intramuscular model

Management of osseous and soft tissue dead space can be a significant challenge in the clinical setting. Calcium sulphate and calcium phosphate-based biomaterials are increasingly being used as alternatives to PMMA for local release of antibiotics, in particular to fill dead space following surgical debridement. This study aims to observe the in-vivo absorption characteristics and tissue response of three commercially available calcium sulphate-based materials combined with gentamicin in an established soft tissue rabbit model. The implant materials (1cc) were placed into four intramuscular sites in 18 New Zealand White rabbits (n = 6). In-life blood samples and radiographs were taken from each animal following implantation. Animals were sacrificed at 0, 1, 7, 21, 42 and 63 days post-operatively (n = 3) and implant sites analysed by micro-computed tomography and histology. Radiographically and histologically, recrystallized calcium sulphate (RCS) absorbed the fastest with complete absorption by day 21. Calcium sulphate/HA composite (CSHA) and Calcium sulphate/calcium carbonate (CSCC) absorbed slower and were detectable at day 63. Residual bead analysis revealed the presence of detectable gentamicin at 24 h and 7 days for CSHA and RCS but none in CSCC. Systemic levels of gentamicin were only detected between 1 h and 24 h. Serological inflammatory cytokine expression for IL-6, TNF-α and IL-1β indicated no unusual inflammatory response to the implanted materials. Calcium sulphate materials loaded with gentamicin are effective in resolving a surgically created dead space without eliciting any adverse host response.

The influence of a calcium sulphate bone void filler on the third-body damage and polyethylene wear of total knee arthroplasty

OBJECTIVES

Bone void fillers are increasingly being used for dead space management in arthroplasty revision surgery. The aim of this study was to investigate the influence of calcium sulphate bone void filler (CS-BVF) on the damage and wear of total knee arthroplasty using experimental wear simulation.

METHODS

A total of 18 fixed-bearing U2 total knee arthroplasty system implants (United Orthopedic Corp., Hsinchu, Taiwan) were used. Implants challenged with CS-BVF were compared with new implants (negative controls) and those intentionally scratched with a diamond stylus (positive controls) representative of severe surface damage (n = 6 for each experimental group). Three million cycles (MC) of experimental simulation were carried out to simulate a walking gait cycle. Wear of the ultra-high-molecular-weight polyethylene (UHMWPE) tibial inserts was measured gravimetrically, and damage to articulating surfaces was assessed using profilometry.

RESULTS

There was no significant difference (p  >  0.05) between the wear rate of implants challenged with CS-BVF (3.3 mm3/MC (95% confidence interval (CI) 1.8 to 4.8)) and the wear rate of those not challenged (2.8 mm3/MC (95% CI 1.3 to 4.3)). However, scratching the cobalt-chrome (CoCr) significantly (p < 0.001) increased the wear rate (20.6 mm3/MC (95% CI 15.5 to 25.7)). The mean surface roughness of implants challenged with CS-BVF was equivalent to negative controls both after damage simulation (p = 0.98) and at the conclusion of the study (p = 0.28).

CONCLUSION

When used close to articulating surfaces, a low-hardness, high-purity CS-BVF had no influence on wear. When trapped between the articulating surfaces of a total knee arthroplasty, CS-BVF did not scratch the surface of CoCr femoral components, nor did it increase the wear of UHMWPE tibial inserts compared with undamaged negative controls.Cite this article: R. M. Cowie, S. S. Aiken, J. J. Cooper, L. M. Jennings. The influence of a calcium sulphate bone void filler on the third-body damage and polyethylene wear of total knee arthroplasty. Bone Joint Res 2019;8:65-72. DOI: 10.1302/2046-3758.82.BJR-2018-0146.R1.

Careful interpretation of the wound status is needed with use of antibiotic impregnated biodegradable synthetic pure calcium sulfate beads: Series of 39 cases

Introduction: The use of antibiotic impregnated biodegradable synthetic high purity calcium sulfate (SHPCS) beads is frequently reported as they offer increased concentration of antibiotics locally, without need for removal. However some wound discharge following their use has been noted. The purpose of this study was to determine any correlation between wound discharge and infection remission. Methodology: Retrospective study of 39 cases of Osteoarticular infections from April 2013 to November 2016 in whom SHPCS beads were used. All patients underwent the standard staged protocol of aggressive debridement, deep tissue biopsy, implant removal where indicated and early soft tissue cover. SHPCS beads were used locally in the second stage combined with appropriate antibiotics based on tissue culture. All patients received systemic antibiotics for a period of 6 weeks and followed up for a minimum period of six months. The study analysed the patient demographics, etiology, surgical procedures, culture patterns, local antibiotics used, radiological status of beads, incidence and characteristics of wound discharge and outcome. Results: There were 25 cases of chronic osteomyelitis, eight infected non unions, three peri prosthetic joint infections, two soft tissue infections and one case of acute osteomyelitis. 17 of these infections were following osteosynthesis. The cultures were negative on eight occasions in seven patients. A total of 40 organisms were isolated in the other patients; commonest being Staphylococcus aureus (n=16) and E coli (n=7). SHPCS beads were mixed with vancomycin in 17 cases, colistin in 11, vancomycin with colistin in eight and vancomycin with gentamicin in four. Voriconazole was used in one case with fungal infection. Eight cases (20.51 %) developed discharge from the wound at an average of 6 days after inserting the beads. The discharge was serous with no foul smell in six and purulent in two inflamed wounds. Four cases underwent re-debridement; two cases with purulent discharge and subsequent positive cultures; two with serous discharge early in the series and no evidence of infection on re-exploration with negative cultures. The remaining four patients with serous wound discharge were observed without any further surgical intervention, with the discharge stopping spontaneously between 15 to 36 days post operatively. There was no correlation between antibiotic used and wound discharge. Radiographic analysis showed dissolution of all the beads at an average of 36 days in the 39 cases. Heterotrophic ossification was not observed. Clinical and radiological remission of infection was observed in 37 cases (94.9%). Two patients died during the course of hospitalization, secondary to septicaemia and multi organ failure. Three patients had an infection recurrence within six months, managed successfully by re-debridement and appropriate antibiotics. Radiological union was achieved in seven of the eight infected non unions. Conclusions: With the encouraging rates of infection remission we have observed, we continue to use antibiotic loaded SHPCS as an alternative for local antibiotic delivery in the treatment of osteoarticular infections. However, wound discharge is a known potential observation following implantation of calcium sulfate beads, subsiding typically within four to six weeks. The appearance of wound discharge can vary, ranging from purulent discharges to non-purulent, serous/ sero sanguineous fluid wound discharges. The presence of a wound discharge alone does not necessarily imply a failure to treat the infection. It is important to be aware of this side effect and guard against unnecessary re- operations, by careful consideration and monitoring all of the available clinical signs of infection, in addition to blood test results and radiographic evidence. Further research is needed to determine the relationship between the implantation of antibiotic loaded calcium sulfates and the incidence and duration of drainage.

Elution profiles of tobramycin and vancomycin from high-purity calcium sulphate beads incubated in a range of simulated body fluids

The aim of this study was to characterise the elution profiles of antibiotics in combination with pharmaceutical grade calcium sulphate beads in phosphate buffered saline and other physiological solutions which more closely mimic the in vivo environment. Synthetic recrystallised calcium sulphate was combined with vancomycin hydrochloride powder and tobramycin sulphate solution and the paste was formed into 3 mm diameter hemispherical beads. Then 2 g of beads were immersed in 2 ml of either phosphate buffered saline, Dulbecco's Modified Eagle Medium or Hartmann's solution and incubated at 37℃ for up to 21 days. At a range of time points, eluent was removed for analysis by liquid chromatography-mass spectrometry (LC-MS). Tobramycin sulphate and vancomycin hydrochloride release was successfully quantified against standard curves from solutions eluted in all three physiological media (phosphate buffered saline, Dulbecco's Modified Eagle Medium and Hartmann's solution) during incubation with calcium sulphate beads. One hour eluate concentrations were high, up to 2602 µg/ml for tobramycin in phosphate buffered saline and 7417 µg/ml for vancomycin, whereas in DMEM, the levels of tobramycin were 2458 µg/ml and 4401 µg/ml for vancomycin. The levels in HRT were 2354 µg/ml for tobramycin and 5948 µg/ml for vancomycin. The results show highest levels of antibiotic elution over the first 24 h, which gradually diminish over the following 21 days.

Influence of third-body particles originating from bone void fillers on the wear of ultra-high-molecular-weight polyethylene

Calcium sulfate bone void fillers are increasingly being used for dead space management in infected arthroplasty revision surgery. The presence of these materials as loose beads close to the bearing surfaces of joint replacements gives the potential for them to enter the joint becoming trapped between the articulating surfaces; the resulting damage to cobalt chrome counterfaces and the subsequent wear of ultra-high-molecular-weight polyethylene is unknown. In this study, third-body damage to cobalt chrome counterfaces was simulated using particles of the calcium sulfate bone void fillers Stimulan^® (Biocomposites Ltd., Keele, UK) and Osteoset^® (Wright Medical Technology, TN, USA) using a bespoke rig. Scratches on the cobalt chrome plates were quantified in terms of their density and mean lip height, and the damage caused by the bone void fillers was compared to that caused by particles of SmartSet GMV PMMA bone cement (DePuy Synthes, IN, USA). The surface damage from Stimulan^® was below the resolution of the analysis technique used; SmartSet GMV caused 0.19 scratches/mm with a mean lip height of 0.03 µm; Osteoset^® led to a significantly higher number (1.62 scratches/mm) of scratches with a higher mean lip height (0.04 µm). Wear tests of ultra-high-molecular-weight polyethylene were carried out in a six-station multi-axial pin on plate reciprocating rig against the damaged plates and compared to negative (highly polished) and positive control plates damaged with a diamond stylus (2 µm lip height). The wear of ultra-high-molecular-weight polyethylene was shown to be similar against the negative control plates and those damaged with third-body particles; there was a significantly higher (p < 0.001) rate of ultra-high-molecular-weight polyethylene wear against the positive control plates. This study showed that bone void fillers of similar composition can cause varying damage to cobalt chrome counterfaces. However, the lip heights of the scratches were not of sufficient magnitude to increase the wear of ultra-high-molecular-weight polyethylene above that of the negative controls.

Sternoclavicular Joint Infection Treated with Debridement, Vancomycin-Loaded Calcium Sulfate, and Partial Pectoralis Muscle Flap: A Case Report

CASE

We report the case of a forty-six-year-old man with a left sternoclavicular joint infection that was treated effectively with surgical debridement, the implantation of vancomycin-loaded calcium sulfate, a partial pectoralis major muscle flap, and two weeks of intravenous antibiotics.

CONCLUSION

Sternoclavicular joint infection is a rare problem that has received little attention in the orthopaedic literature. The combined surgical procedure detailed here provided good soft-tissue coverage, avoided the potential toxic effect of prolonged systemic antibiotic therapy, and resulted in a good clinical outcome.

Local release of antibiotics for surgical site infection management using high-purity calcium sulfate: an in vitro elution study

BACKGROUND

The aim of this study was to characterize the elution of four antibiotics from pharmaceutical-grade calcium sulfate beads and show that the eluted antibiotics retained efficacy.

METHODS

Calcium sulfate was combined with gentamicin, tobramycin, vancomycin, or rifampicin (ratio: 20 g of calcium sulfate, to 240 mg, 500 mg, 900 mg, and 600 mg of antibiotic, respectively). Three grams of beads were immersed in 4 mL of sterile phosphate-buffered saline (PBS) at 37°C. At each time point (4, 8, 24 h; 2, 7, 14, 28, 42 d), eluates were removed for analysis by liquid chromatography-mass spectrometry. The antimicrobial efficacy of antibiotics combined with calcium sulfate beads after 42 d was tested by a modified Kirby-Bauer disc diffusion assay.

RESULTS

All samples showed a generally exponential decay in the eluted antibiotic concentration. At the first time point, both gentamicin and tobramycin had eluted to a peak concentration of approximately 10,000 mcg/mL. For rifampicin, the peak concentration occurred at 24 h, whereas for vancomycin, it occurred at 48 h. The eluted concentrations exceeded the minimum inhibitory concentration for common periprosthetic joint infection pathogens for the entire span of the 42 study days. Mass spectrometry confirmed all antibiotics were unchanged when eluted from the calcium sulfate carrier. Antimicrobial efficacy was unaltered after 42 d in combination with calcium sulfate at 37°C.

CONCLUSIONS

Pharmaceutical-grade calcium sulfate has the potential for targeted local release of tobramycin, gentamicin, vancomycin, and rifampicin over a clinically meaningful time period.

Development of an injectable bioactive bone filler cement with hydrogen orthophosphate incorporated calcium sulfate

Calcium sulfate cement (CSC) has emerged as a potential bone filler material mainly because of the possibility of incorporating therapeutic agents. Delivery of the cement through a needle or cannula will make it more useful in clinical applications. However, it was not possible to make CSC injectable because of the inherent lack of viscosity. The present work demonstrates the design development of a viscous and fully-injectable CSC by incorporating hydrogen orthophosphate ions, which does not hamper the biocompatibility of the material. The effect of addition of hydrogen orthophosphate on the rheological properties of the CSC paste was studied using a custom made capillary rheometer. The physicochemical changes associated with cement setting process were examined using X-ray diffraction and Fourier transform infrared spectroscopy and the thermal changes were measured through isothermal differential scanning calorimetry. Micromorphological features of different compositions were observed in environmental scanning electron microscopy and the presence of phosphate ions was identified with energy dispersive X-ray spectroscopic analysis and inductively coupled plasma-optical emission spectroscopy. The results indicated that HPO4 (2-) ions have profound effects on the rheological properties and setting of the CSC paste. Significant finding is that the HPO4 (2-) ions are getting substituted in the calcium sulfate dihydrate crystals during setting. The variations of setting time and compressive strength of the cement with the additive concentration were investigated. An optimum concentration of 2.5 % w/w gave a fully-injectable cement with clinically relevant setting time (below 20 min) and compressive strength (12 MPa). It was possible to inject the optimised cement paste from a syringe through an 18-gauge needle with thumb pressure. This cement will be useful both as bone filler and as a local drug delivery medium and it allows minimally invasive bone defect management.

Tetracycline nanoparticles loaded calcium sulfate composite beads for periodontal management

BACKGROUND

The objective of this study was to fabricate, characterize and evaluate in vitro, an injectable calcium sulfate bone cement beads loaded with an antibiotic nanoformulation, capable of delivering antibiotic locally for the treatment of periodontal disease.

METHODS

Tetracycline nanoparticles (Tet NPs) were prepared using an ionic gelation method and characterized using DLS, SEM, and FTIR to determine size, morphology, stability and chemical interaction of the drug with the polymer. Further, calcium sulfate (CaSO4) control and CaSO4-Tet NP composite beads were prepared and characterized using SEM, FTIR and XRD. The drug release pattern, material properties and antibacterial activity were evaluated. In addition, protein adsorption, cytocompatibility and alkaline phosphatase activity of the CaSO4-Tet NP composite beads in comparison to the CaSO4 control were analyzed.

RESULTS

Tet NPs showed a size range of 130±20nm and the entrapment efficiency calculated was 89%. The composite beads showed sustained drug release pattern. Further the drug release data was fitted into various kinetic models wherein the Higuchi model showed higher correlation value (R(2)=0.9279) as compared to other kinetic models. The composite beads showed antibacterial activity against Staphylococcus aureus and Escherichia coli. The presence of Tet NPs in the composite bead didn't alter its cytocompatibility. In addition, the composite beads enhanced the ALP activity of hPDL cells.

CONCLUSIONS

The antibacterial and cytocompatible CaSO4-Tet NP composite beads could be beneficial in periodontal management to reduce the bacterial load at the infection site.

GENERAL SIGNIFICANCE

Tet NPs would deliver antibiotic locally at the infection site and the calcium sulfate cement, would itself facilitate tissue regeneration.