Aims. There is a lack of biomaterial-based carriers for the local delivery of rifampicin (RIF), one of the cornerstone second defence antibiotics for bone infections. RIF is also known for causing rapid development of antibiotic resistance when given as monotherapy. This in vitro study evaluated a clinically used biphasic calcium sulphate/hydroxyapatite (CaS/HA) biomaterial as a carrier for dual delivery of RIF with vancomycin (VAN) or gentamicin (GEN). Methods. The CaS/HA composites containing RIF/GEN/VAN, either alone or in combination, were first prepared and their injectability, setting time, and antibiotic elution profiles were assessed. Using a continuous disk diffusion assay, the antibacterial behaviour of the material was tested on both planktonic and biofilm-embedded forms of standard and clinical strains of Staphylococcus aureus for 28 days. Development of bacterial resistance to RIF was determined by exposing the biofilm-embedded bacteria continuously to released fractions of antibiotics from CaS/HA-antibiotic composites. Results. Following the addition of RIF to CaS/HA-VAN/GEN, adequate injectability and setting of the CaS/HA composites were noted. Sustained release of RIF above the minimum inhibitory concentrations of S. aureus was observed until study endpoint (day 35). Only combinations of CaS/HA-VAN/GEN + RIF exhibited antibacterial and antibiofilm effects yielding no viable bacteria at study endpoint. The S. aureus strains developed resistance to RIF when biofilms were subjected to CaS/HA-RIF alone but not with CaS/HA-VAN/GEN + RIF. Conclusion. Our in vitro results indicate that biphasic CaS/HA loaded with VAN or GEN could be used as a carrier for RIF for local delivery in clinically demanding bone infections. Cite this article: Bone Joint Res 2022;11(11):787–802

Aims. Dead-space management, following dead bone resection, is an important element of successful chronic osteomyelitis treatment. This study compared two different biodegradable antibiotic carriers used for dead-space management, and reviewed clinical and radiological outcomes. All cases underwent single-stage surgery and had a minimum one-year follow-up. Methods. A total of 179 patients received preformed calcium sulphate pellets containing 4% tobramycin (Group OT), and 180 patients had an injectable calcium sulphate/nanocrystalline hydroxyapatite ceramic containing gentamicin (Group CG). Outcome measures were infection recurrence, wound leakage, and subsequent fracture involving the treated segment. Bone-void filling was assessed radiologically at a minimum of six months post-surgery. Results. The median follow-up was 4.6 years (interquartile range (IQR) 3.2 to 5.4; range 1.3 to 10.5) in Group OT compared to 4.9 years (IQR 2.1 to 6.0; range 1.0 to 8.3) in Group CG. The groups had similar defect sizes following excision (both mean 10.9 cm. 3. (1 to 30)). Infection recurrence was higher in Group OT (20/179 (11.2%) vs 8/180 (4.4%), p = 0.019) than Group CG, as was early wound leakage (33/179 (18.4%) vs 18/180 (10.0%), p = 0.024) and subsequent fracture (11/179 (6.1%) vs 1.7% (3/180), p = 0.032). Group OT cases had an odds ratio 2.9-times higher of developing any one of these complications, compared to Group CG (95% confidence interval 1.74 to 4.81, p < 0.001). The mean bone-void healing in Group CG was better than in Group OT, in those with ≥ six-month radiological follow-up (73.9% vs 40.0%, p < 0.001). Conclusion. Local antibiotic carrier choice affects outcome in chronic osteomyelitis surgery. A biphasic injectable carrier with a slower dissolution time was associated with better radiological and clinical outcomes compared to a preformed calcium sulphate pellet carrier. Cite this article: Bone Joint Res 2023;12(7):412–422

Aims. There is a considerable challenge in treating bone infections and orthopaedic device-associated infection (ODAI), partly due to impaired penetration of systemically administrated antibiotics at the site of infection. This may be circumvented by local drug administration. Knowledge of the release kinetics from any carrier material is essential for proper application. Ceftriaxone shows a particular constant release from calcium sulphate (CaSO. 4. ) in vitro, and is particularly effective against streptococci and a large portion of Gram-negative bacteria. We present the clinical release kinetics of ceftriaxone-loaded CaSO. 4. applied locally to treat ODAI. Methods. A total of 30 operations with ceftriaxone-loaded CaSO. 4. had been performed in 28 patients. Ceftriaxone was applied as a single local antibiotic in 21 operations and combined with vancomycin in eight operations, and in an additional operation with vancomycin and amphotericin B. Sampling of wound fluid was performed from drains or aspirations. Ceftriaxone concentrations were measured by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Results. A total of 37 wound fluid concentrations from 16 operations performed in 14 patients were collected. The ceftriaxone concentrations remained approximately within a range of 100 to 200 mg/l up to three weeks. The median concentration was 108.9 mg/l (interquartile range 98.8 to 142.5) within the first ten days. No systemic adverse reactions were observed. Conclusion. Our study highlights new clinical data of locally administered ceftriaxone with CaSO. 4. as carrier material. The near-constant release of ceftriaxone from CaSO. 4. observed in vitro could be confirmed in vivo. The concentrations remained below known local toxicity thresholds. Cite this article: Bone Joint Res 2022;11(11):835–842

Aims. Excision of chronic osteomyelitic bone creates a dead space which must be managed to avoid early recurrence of infection. Systemic antibiotics cannot penetrate this space in high concentrations, so local treatment has become an attractive adjunct to surgery. The aim of this study was to present the mid- to long-term results of local treatment with gentamicin in a bioabsorbable ceramic carrier. Methods. A prospective series of 100 patients with Cierny-Mader Types III and IV chronic ostemyelitis, affecting 105 bones, were treated with a single-stage procedure including debridement, deep tissue sampling, local and systemic antibiotics, stabilization, and immediate skin closure. Chronic osteomyelitis was confirmed using strict diagnostic criteria. The mean follow-up was 6.05 years (4.2 to 8.4). Results. At final follow-up, six patients (six bones) had recurrent infection; thus 94% were infection-free. Three infections recurred in the first year, two in the second year, and one 4.5 years postoperatively. Recurrence was not significantly related to the physiological class of the patient (1/20 Class A (5%) vs 5/80 Class B (6.25%); p = 0.833), nor was it significantly related to the aetiology of the infection, the organisms which were cultured or the presence of nonunion before surgery (1/10 with nonunion (10%) vs 5/90 without nonunion (5.6%); p = 0.570). Organisms with intermediate or high-grade resistance to gentamicin were significantly more likely in polymicrobial infections (9/21; 42.8%) compared with monobacterial osteomyelitis (7/79 (8.9%); p < 0.001). However, recurrence was not significantly more frequent when a resistant organism was present (1/16 for resistant cases (6.25%) vs 5/84 in those with a microbiologically sensitive infection (5.95%); p = 0.958). Conclusion. We found that a single-stage protocol, including the use of a high-delivery local antibiotic ceramic carrier, was effective over a period of several years. The method can be used in a wide range of patients, including those with significant comorbidities and an infected nonunion. Cite this article: Bone Joint J 2022;104-B(9):1095–1100

There is a lack of carriers for the local delivery of rifampicin (RIF), one of the cornerstone second defence antibiotic for Staphylococcus aureus deep bone infections (DBIs). RIF is also associated with systemic side effects, and known for causing rapid development of antibiotic resistance when given as monotherapy. We evaluated a clinically usedbi-phasic calcium sulphate/hydroxyapatite (CaS/HA) biomaterial as a carrier for dual delivery of RIF with vancomycin (VAN) or gentamicin (GEN). It was hypothesized that this combined approach could provide improved biofilm eradication and prevent the development of RIF resistance. Methods: 1) Biofilm eradication: Using a modified crystal violet staining biofilm quantification method, the antibiotics released at different time points (Day 1, 3, 7, 14, 21, 28 and 35) from the hemispherical pellets of CaS/HA(500 mg)-VAN (24.57 mg) / GEN (10.35 mg) composites with or without RIF (8.11 mg) were tested for their ability to disrupt the preformed 48-h old biofilms of S. aureus ATCC 25923, and S. aureus clinical strain P-3 in 96-well microtitre plate. For each tested group of antibiotic fractions, five separate wells were used (n=5). 2) Testing for resistance development: Similar to the method mentioned above the 48-h biofilm embeded bacteria exposed to antibiotic fractions from different time points continuously for 7 days. The biofilms remained were then tested for RIF resistant strains of bacteria. Overall, there was clear antibiofilm biofilm activity observed with CaS/HA-VAN/GEN+RIF combinations compared with CaS/HA-VAN/GEN alone. The S. aureus strains developed resistance to RIF when biofilms were subjected to CaS/HA-RIF alone but not with combinations of CaS/HA-VAN/GEN+RIF. Enhanced antibiofilm effects without development of RIF resistance indicates that biphasic CaS/HA loaded with VAN or GEN could be used as a carrier for RIF for additional local delivery in clinically demanding DBIs. Acknowledgement: We deeply acknowledge the Royal Fysiographic Society of Lund, Landshövding Per Westlings Minnesfond and the Stina and Gunnar Wiberg fond for financial support

Aims. The use of local antibiotic carriers in the treatment of chronic osteomyelitis is an important adjunct in dead space management. We present the outcomes of two different biodegradable antibiotic carriers used in the management of chronic osteomyelitis. Method. A single centre series between 2006–2017. The initial cohort (2006–2010) of 137 cases, Group A, had Osteoset® T (calcium sulphate carrier containing tobramycin). The second cohort (2013–1017) of 160 cases, group B, had CeramentTM G (biphasic calcium sulphate, nano-crystalline hydroxyapatite carrier containing gentamicin). Only Cierny-Mader Grade III and IV cases were included with a minimum six-month radiographic follow-up. Infection recurrence rate, wound leakage, subsequent fracture involving the treated segment, and radiographic void filling were assessed at a minimum of 6 months following surgery. Results. Mean follow-up in Group A was 2.5 yrs (0.5–10.5) and in Group B it was 1.4 yrs (0.6–4.7). Group A had a significantly higher rate of infection recurrence (16/137 (11.7%) Vs. 7/160 (4.4%) p=0.0278), wound leakage (26/137 (19.0%) Vs. 16/160 (10.0%) p=0.0304) and subsequent fracture rate (11/137 (8.0%) Vs. 3/160 (1.9%) p=0.0143) compared to Group B. Average time to recurrence was 1.07 years (0.1–2.6) in Group A and 1.02 (0.2–2.1) in Group B. The mean bone void healing in Group B was significantly better than Group A (73.2% Vs. 40.0%, p <0.00001). Conclusions. Cerament™ G has significantly better bone healing compared to a calcium sulphate carrier and was associated with a lower rate of recurrent infection, wound leakage and subsequent fracture risk

Aims. Calcium sulphate (CaSO. 4. ) is a resorbable material that can be used simultaneously as filler of a dead space and as a carrier for the local application of antibiotics. Our aim was to describe the systemic exposure and the wound fluid concentrations of vancomycin in patients treated with vancomycin-loaded CaSO. 4. as an adjunct to the routine therapy of bone and joint infections. Patients and Methods. A total of 680 post-operative blood and 233 wound fluid samples were available for analysis from 94 implantations performed in 87 patients for various infective indications. Up to 6 g of vancomycin were used. Non-compartmental pharmacokinetic analysis was performed on the data from 37 patients treated for an infection of the hip. Results. The overall systemic exposure remained within a safe range, even in patients with post-operative renal failure, none requiring removal of the pellets. Local concentrations were approximately ten times higher than with polymethylmethacrylate (PMMA) as a carrier, but remained below reported cell toxicity thresholds. Decreasing concentrations in wound fluid were observed over several weeks, but remained above the common minimum inhibitory concentrations for Staphylococcus up to three months post-operatively. . Conclusion. This study provides the first pharmacokinetic description of the local application of vancomycin with CaSO. 4. as a carrier, documenting slow release, systemic safety and a release profile far more interesting than from PMMA. In particular, considering in vitro data, concentrations of vancomycin active against staphylococcal biofilm were seen for several weeks. Cite this article: Bone Joint J 2017;99-B:1537–44

We examined the incidence of infection with methicillin-resistant Staphylococcus aureus (MRSA) in patients admitted to the Leicester Royal Infirmary Trauma Unit between January 2004 and June 2006. The influence of MRSA status at the time of their admission was examined, together with age, gender and diagnosis, using multi-variant analysis. Of 2473 patients, 79 (3.2%) were MRSA carriers at the time of admission and 2394 (96.8%) were MRSA-negative. Those carrying MRSA at the time of admission were more likely to develop surgical site infection with MRSA (7 of 79 patients, 8.8%) than non-MRSA carriers (54 of 2394 patients, 2.2%, p < 0.001). Further analysis showed that hip fracture and increasing age were also risk factors with a linear increase in relative risk of 1.8% per year. MRSA carriage at admission, age and the pathology are all associated with an increased rate of developing MRSA wound infection. Identification of such risk factors at admission helps to target health-care resources, such the use of glycopeptide antibiotics at induction and the ‘building-in’ of increased vigilance for wound infection pre-operatively

Critical size defects in ovine tibiae, stabilised with intramedullary interlocking nails, were used to assess whether the addition of carboxymethylcellulose to the standard osteogenic protein-1 (OP-1/BMP-7) implant would affect the implant’s efficacy for bone regeneration. The biomaterial carriers were a ‘putty’ carrier of carboxymethylcellulose and bovine-derived type-I collagen (OPP) or the standard with collagen alone (OPC). These two treatments were also compared to “ungrafted” negative controls. Efficacy of regeneration was determined using radiological, biomechanical and histological evaluations after four months of healing. The defects, filled with OPP and OPC, demonstrated radiodense material spanning the defect after one month of healing, with radiographic evidence of recorticalisation and remodelling by two months. The OPP and OPC treatment groups had equivalent structural and material properties that were significantly greater than those in the ungrafted controls. The structural properties of the OPP- and OPC-treated limbs were equivalent to those of the contralateral untreated limb (p > 0.05), yet material properties were inferior (p < 0.05). Histopathology revealed no residual inflammatory response to the biomaterial carriers or OP-1. The OPP- and OPC-treated animals had 60% to 85% lamellar bone within the defect, and less than 25% of the regenerate was composed of fibrous tissue. The defects in the untreated control animals contained less than 40% lamellar bone and more than 60% was fibrous tissue, creating full cortical thickness defects. In our studies carboxymethylcellulose did not adversely affect the capacity of the standard OP-1 implant for regenerating bone

During the last decades, several research groups have used bisphosphonates for local application to counteract secondary bone resorption after bone grafting, to improve implant fixation or to control bone resorption caused by bone morphogenetic proteins (BMPs). We focused on zoledronate (a bisphosphonate) due to its greater antiresorptive potential over other bisphosphonates. Recently, it has become obvious that the carrier is of importance to modulate the concentration and elution profile of the zoledronic acid locally. Incorporating one fifth of the recommended systemic dose of zoledronate with different apatite matrices and types of bone defects has been shown to enhance bone regeneration significantly in vivo. We expect the local delivery of zoledronate to overcome the limitations and side effects associated with systemic usage; however, we need to know more about the bioavailability and the biological effects. The local use of BMP-2 and zoledronate as a combination has a proven additional effect on bone regeneration. This review focuses primarily on the local use of zoledronate alone, or in combination with bone anabolic factors, in various preclinical models mimicking different orthopaedic conditions. Cite this article: I. Qayoom, D. B. Raina, A. Širka, Š. Tarasevičius, M. Tägil, A. Kumar, L. Lidgren. Anabolic and antiresorptive actions of locally delivered bisphosphonates for bone repair: A review. Bone Joint Res 2018;7:548–560. DOI: 10.1302/2046-3758.710.BJR-2018-0015.R2

Summary. Carriers for local delivery of stem cells into degenerative intervertebral discs need to be tested under physiological loading since stem cell viability, density and differentiation, as well as carrier stability are strongly affected by loading. Introduction. The success of the local delivery of mesenchymal stem cells (MSCs) to degenerative discs relies on three main factors: (i) an appropriate delivery method, (ii) a suitable carrier, (iii) resistance to loading forces. Bioreactors allow the application of loading to whole intervertebral discs and represent a useful tool to screen the potential of new regenerative therapies. We have previously shown that hydrogel delivery through the endplate (EP) leaves the annulus fibrosus (AF) intact (as opposed to an approach through the AF). Furthermore, we have found that the physiological loading needs to be adapted for nucleotomised discs. In this study we compare the behaviour of two MSCs carriers under loading in a whole IVD bioreactor. Materials & Methods. MSCs were isolated from human bone marrow after approval by the local ethical commission and written consent of the patient (age: 20–60 years). Whole IVDs were harvested from calf tails obtained from the local abattoir. Partial nucleotomies were achieved by mechanically removing the nucleus pulposus (NP) through the endplate. Firstly, hMSCs suspended in hyaluronan thermoreversible hydrogel. 2. (6×10. 6. cells/ml) were supplied to the nucleotomised IVDs and the removed EP was re-inserted. Discs were either loaded for one week at 0.06 ± 0.02 MPa, 0.1 Hz, 4 hours/day (n=4) or kept unloaded in culture medium (control). Secondly, hMSCs suspended in fibrin (100 mg/ml fibrinogen and 500 IU/ml thrombin) were applied to IVDs as above described. Discs were kept unloaded in culture medium for one week and then loaded for two weeks at 0.06 ± 0.02 MPa, 0.1Hz, 3 hours/day (n=4) or kept unloaded (control). Analyses included histology, gene expression and cell viability. Results. On the gene level, it was found that loading is required to induce aggrecan (a major component of the NP tissue) up-regulation in MSCs for both carriers. Aggrecan was up-reguled in MSCs already after one week of loading in the thermoreversible hyaluronan, but only after two weeks MSCs in fibrin. Additionally, the highest expression of keratin-19 (NP marker) was found in the loaded thermoreversible hyaluronan group. However, there was a high cell and material loss under loading in this group. Fibrin was more stable in the chosen experimental conditions, as shown in the safranin O-Fast green staining of the IVD. Indeed, the NP cavity was still filled with fibrin gel after 2 weeks of loading. No significant cell loss or decrease in cell viability was found in the fibrin gel after 2 weeks of loading. Discussion/Conclusion. The hyaluronan thermoreversible hydrogel is superior in promoting the differentiation of MSCs toward the disc phenotype, as attested by the aggrecan up-regulation. However, the fibrin gel has a better stability and is more effective at maintaining a high density of MSCs, even under loading. In conclusion, stem cell carriers need to be evaluated in a relevant setting, e.g. in an IVD under load. The study was partially supported by a NASS Research grant

Objectives. Sustained intra-articular delivery of pharmacological agents is an attractive modality but requires use of a safe carrier that would not induce cartilage damage or fibrosis. Collagen scaffolds are widely available and could be used intra-articularly, but no investigation has looked at the safety of collagen scaffolds within synovial joints. The aim of this study was to determine the safety of collagen scaffold implantation in a validated in vivo animal model of knee arthrofibrosis. Materials and Methods. A total of 96 rabbits were randomly and equally assigned to four different groups: arthrotomy alone; arthrotomy and collagen scaffold placement; contracture surgery; and contracture surgery and collagen scaffold placement. Animals were killed in equal numbers at 72 hours, two weeks, eight weeks, and 24 weeks. Joint contracture was measured, and cartilage and synovial samples underwent histological analysis. Results. Animals that underwent arthrotomy had equivalent joint contractures regardless of scaffold implantation (-13.9° versus -10.9°, equivalence limit 15°). Animals that underwent surgery to induce contracture did not demonstrate equivalent joint contractures with (41.8°) or without (53.9°) collagen scaffold implantation. Chondral damage occurred in similar rates with (11 of 48) and without (nine of 48) scaffold implantation. No significant difference in synovitis was noted between groups. Absorption of the collagen scaffold occurred within eight weeks in all animals. Conclusion. Our data suggest that intra-articular implantation of a collagen sponge does not induce synovitis or cartilage damage. Implantation in a native joint does not seem to induce contracture. Implantation of the collagen sponge in a rabbit knee model of contracture may decrease the severity of the contracture. Cite this article: J. A. Walker, T. J. Ewald, E. Lewallen, A. Van Wijnen, A. D. Hanssen, B. F. Morrey, M. E. Morrey, M. P. Abdel, J. Sanchez-Sotelo. Intra-articular implantation of collagen scaffold carriers is safe in both native and arthrofibrotic rabbit knee joints. Bone Joint Res 2016;6:162–171. DOI: 10.1302/2046-3758.63.BJR-2016-0193

Introduction. The treatment of chronic osteomyelitis involves a debridement of affected non-viable tissue and the use of antibiotics. Where surgery leaves a cavity, dead space management is practised with antibiotic impregnated cement. These depots of local antibiotics are variable in elution properties and need removal. We review the use of bioabsorbable synthetic calcium sulphate as a carrier of gentamicin and as an adjunct in treating intramedullary osteomyelitis. Methods. A retrospective review of cases treated consecutively from 2006 to 2010 was undertaken. Variables recorded included aetiology, previous interventions, diagnostic criteria, radiological features, serology and microbiology. The Cierney-Mader system was used to classify. Treatment involved removal of implants (if any), intramedullary debridement and local resection (if needed), lavage and instillation of the gentamicin carrier, supplemented with systemic antibiotics. Follow-up involved a survival analysis to time to recurrence, clinical and functional assessment (AOFAS-Ankle/IOWA knee/Oxford Hip) and general health outcome (SF36). Results. There were 31 patients (22 male, 9 female). The mean age was 47 years (20–67). Twenty-five cases were post-surgery (6 open fractures) and 6 were haematogenous in origin. The median duration of osteomyelitis was 1.6yrs. The bones affected were 42% femur, 45% tibia, 3% radius and 10% humerus. 11 cases had diffuse as well as intramedullary involvement. 9 cases underwent segment resection and bone transport. We identified Staph. Aureus in 16 and Coag. Neg. Staph. in 6 cases. The median follow-up was 1.7 years (0.5–5.6). The median scores attained were: AOFAS-78, DASH-32, IOWA-71, Oxford-32. There were two recurrences. Discussion. Dead space management of intramedullary infections is difficult. We describe a method for delivery of local antibiotics and provide early evidence to its efficacy. The treatment success to date is 93%. Conclusion. Bioabsorbable carriers of antibiotics are efficacious adjuncts to surgical treatment of intramedullary osteomyelitis

Introduction: Two stage revision procedures is the gold standard in management of periprosthetic infections. Cement spacers impregnated with antibiotics have long been used to preserve the space created during resection procedure and to release antiobiotics within the created dead space. However, the problems related to cement as an antibiotic carrier are well recognised (random porosity, thermal necrosis, unspecified antibiotic delivery rate). The rationale of this study is that calcium hydroxyapatite antibiotic carrier (PerOssal) overlaps the known disadvantages of cement spacers, and leads to better outcome in terms of clinical parameters and re-infection rate. Purpose: Our purpose was to identify specific clinical and laboratory differences between cases submitted to conventional two stage revision arthroplasty vs cases treated with PerOssal as an antibiotic carrier. Material & Methods: During 2004 to 2008, 46 patients (38 females and 8 males, mean age 65.3 years, range 32 to 84) with infected TKR were revised using a two-stage revision protocol. In 31 patients (group A – 25 females and 6 males) a conventional articulating spacer impregnated with antibiotics was used, whereas in the remaining 15 patients (group B – 13 females, 2 males) a combination of an articulating spacer and PerOssal as antibiotic carrier was used. All patients were reviewed with laboratory exams (WBC, ESR, CRP) every 7 days and joint fluid aspiration prior to re-implantation, which was performed at mean 8 months post 1st stage (range, 6 to 12 months). Results: At a mean follow-up of 36 months (range, 8 to 60 months) no patient was lost or died. WBC count and ESR showed no statistically significant differences at any time interval (p> 0.05). However, CRP values had a statistically significant difference between the two groups after the second week postoperatively (p3rd week= 0.042) and group B had significantly lower CRP values compared to group A at every check point thereafter (p4th week=0.038, p5th week=0.031, p6th week=0.034). Re-infection rate was 16.12% in group A and 6.6% in group B (p=0.192). Conclusions: PerOssal can be used as an additional antibiotic carrier in cases of periprosthetic infections of TKR. It is associated with more rapid reduction of CRP levels, probably due to greater porosity and better antibiotic delivery comparing to impregnated cement. Larger series of patients could reveal potential differences in the re-infection rates as indicated by our study

Aim. Chronic osteomyelitis often requires surgical debridement and local antibiotic treatment. Disadvantages of PMMA carriers include low dose release and the requirement of surgical removal in the case of PMMA-beads. Synthetic nanocrystalline calcium phosphate (nCP) materials, which mimic the chemical structure of the mineral composition of bone, have been well accepted as bone grafting materials due to their consistent osteoconductivity, ease of use, and mechanical properties. Such a material which remodels into native bone is a much more attractive option. The aim of this study is to investigate the release of gentamicin from CaP in vitro and in vivo when implanted in a rabbit femoral condyle defect. Method. Three formulations of nCP were evaluated in this study: putty, paste and porous. Four cylindrical dowels were made for each group with gentamicin sulphate at a concentration of 20mg/cc of paste. Material was eluted in PBS at 37C and pH 7.0 and elutions were tested every day up to 30 days. Eighteen New Zealand white rabbits will undergo surgeries. Briefly, a drill defect will be created in the metaphyseal bone of the lateral femoral condyle. The formulations will be implanted in the created defect at time of surgery and the wound will be closed. Blood will be collected regularly and analysed for gentamicin titers. Animals will be sacrificed at 6wk, 12wk or 24wk. Explanted femurs will be fixed, sectioned and stained. Results. At 7 days the in vitro elution, showed a continued release of gentamicin. A large amount of gentamicin is released within the first day followed by a slow controlled release. The nCP putty shows the slowest release, followed by the paste and porous formulations respectively. There is a significant increase in the elution with an increase in porosity of the material. We expect to observe a similar trend in the rabbit study with an improved healing. At 6wk we expect the implant material to be still present at the site of implantation, which would remodel by 12wk and 24wk to significant levels due to active ossification. Conclusions. nCP materials, which undergo remodelling, can be used an effective carrier for gentamicin or other antibiotic agents. Because of its potentially prolonged release of high levels of antimicrobial agents, this system could maintain long-term antibacterial effectiveness locally

Spinal fusion surgery is a common procedure for the treatment of various spinal diseases. Several growth factors, including bone morphogenic protein-2 (BMP-2) and osteogenic protein-1 (OP-1) have been used in spinal fusion for the induction of bone formation. But complications have been reported due to the lack of suitable carrier. Here we hypothesis that Insoluble Bone Gelatin (ISBG) may be a good carrier for OP-1 in the induction of bone formation during spinal fusion. The aim of this study is to examine the efficacy of osteoconductive carrier, ISBG, for OP-1 in rabbit lumbar inter-transverse process fusion model. Adult New Zealand White rabbits (n=32) underwent bilateral lumbar intertransverse process fusion at L5-L6. The animals were divided into four groups based on the materials implanted:. Autograft group,. ISBG group,. OP-1 group and. ISBG+OP-1 group. Spinal fusion masses were evaluated by manual palpation, biomechanical testing, radiographic examination, micro-CT Scanning, and histological analysis six weeks after surgery. ISBG+OP-1 group demonstrated significantly higher fusion rates (7/7) than autograft (3/7), ISBG (2/8), and OP-1 groups (2/7) (P< 0.05) based on manual palpation. In biomechanical testing, given the same moment, the fusion masses of ISBG+OP-1 group had less range of motions than those of other groups (P< 0.05) in main direction motion. Radiographic examination and micro-CT demonstrated that continuous trabecular pattern within intertransverse process area in ISBG+OP-1 group than other groups, and radiographic scores and bone volume base on micro-CT were also higher than other groups. Mature new bone formation was observed covering the surface of transverse processes in all four groups in histological findings. Continuous trabeculae connected two transverse processes and endochondral bone formation was observed attached the surface of ISBG in ISBG+OP-1 group. However, in other three groups, obvious gaps were noted in fusion masses and fibrous tissue was filled in these gaps. In conclusion, OP-1 carried by ISBG results in more effective spinal fusion in posterolateral lumbar transverse fusion in rabbit model than autograft, ISBG or OP-1 alone

Purpose: Bone morphogenetic proteins (BMP) are fragile products that must be protected from degradation and released progressively to achieve maximal efficacy. Release of quantities to the order of 10μg are required at ectopic sites in the rat; in humans 50 mg is required to induce new bone formation. Use of high-dose BMP is costly and the risk of overestimulating mesenchymatous cells remains to be determined. Functional dextranes, or DMCBSU, are inert biological derivatives with random substitution of carboxymethyl, benzylamide and sulfonate units. The affinity of these products for other growth factors led us to propose their use as specific carriers of BMP extracted from bovin bone. Material and methods: Three different gels (CMDB2, OM27, LS8) and the native dextranes from which they are derived (T40, T500) were tested by to determine their capacity to adsorb and release BMP. Uptake and releasing kinetics were studied by fluorimetry using fluoresceine-labelled BMP. CMDB2 and its native dextrane T500, OM27 and LS8 and their native dextrane TT40, and collagen sponge (control) were implanted in the paravertebral grooves of the rat after impregnating the products with different concentrations of BMP (5 μg, 500 ng, 50 ng, 5 ng). The animals were sacrificed at six weeks. The presence of bone tissue was determined by microradiography and histomorphometry. Results: The more porous gels (OM27 and LS8) adsorbed the greatest quantities of BMP (96.6 and 95.7 ng/ml respectively). Implantation of BMP associated with certain DMBCSU enabled elaboration of bony tissue in an ectopic site for quantities of BMP starting from 50 ng. This bony tissue formation was obtained for collagen sponge controls with doses 100-fold higher (5 μg). Bony tissue obtained with the BMP:DMCBSU combination was endochondral bone presenting cartilaginous lines, followed by mature bony tissue. Conclusion: This preliminary study demonstrates that by choosing the right specific carrier for bone growth factors, it is possible to considerably reduce the minimal dose required to induce formation of new bone at an ectopic site. Implantations in bone defects of a critical size are under investigation to validate these results in a model closer to the clinical situation

We report our experience using a biodegradable calcium sulphate antibiotic carrier containing tobramycin in the surgical management of patients with chronic osteomyelitis. The patients were reviewed to determine the rate of recurrent infection, the filling of bony defects, and any problems with wound healing. A total of 193 patients (195 cases) with a mean age of 46.1 years (16.1 to 82.0) underwent surgery. According to the Cierny–Mader classification of osteomyelitis there were 12 type I, 1 type II, 144 type III and 38 type IV cases. The mean follow-up was 3.7 years (1.3 to 7.1) with recurrent infection occurring in 18 cases (9.2%) at a mean of 10.3 months post-operatively (1 to 25.0). After further treatment the infection resolved in 191 cases (97.9%). Prolonged wound ooze (longer than two weeks post-operatively) occurred in 30 cases (15.4%) in which there were no recurrent infection. Radiographic assessment at final follow-up showed no filling of the defect with bone in 67 (36.6%), partial filling in 108 (59.0%) and complete filling in eight (4.4%). A fracture occurred in nine (4.6%) of the treated osteomyelitic segments at a mean of 1.9 years (0.4 to 4.9) after operation. We conclude that Osteoset T is helpful in the management of patients with chronic osteomyelitis, but the filling of the defect in bone is variable. Prolonged wound ooze is usually self-limiting and not associated with recurrent infection. Cite this article: Bone Joint J 2014; 96-B:829–36

Currently, no clinical options are available to prevent infections on uncemented orthopedic implants. Therefore we investigated the efficacy of DAC-hydrogel (disposable antibacterial coating(1), Novagenit, Italy) as carrier for various agents to prevent infections in an in vivo implant-model. Titanium rods were implanted in the left tibiae in New Zealand White rabbits. Prior to implantation, the implant bed was contaminated with 10∧5 colony forming units S. aureus. In the experimental groups, the hydrogel was loaded prior to be coated on the rods with: 2%(w/v) vancomycin (Van2 group, N=6), 5%(w/v) vancomycin (Van5 group, N=6), 10%(w/v) bioactive glass (BonAlive, Finland) (BAG group, N=6), which is antibacterial(2) and osteoconductive(3), or 0.5%(w/v) N-acetyl cysteine (NAC group, N=6), which inhibits bacterial growth and decreases biofilm formation(4). In the control group, empty hydrogel was applied (Gel group, N=12). Blood values were measured weekly. Following explantation on day 28, the anterior tibia was processed for bacterial culture. The posterior tibia and rod were used for measuring bone-implant contact using micro-CT and for histopathology. Results of the experimental groups were compared to the Gel group results. The blood values in the Van2 and Van5 groups were lower on day 7. Moreover, culture results demonstrated less animals with an infection in both groups at day 28. In accordance, these groups showed lower grades for infection. Further, the Van2 group demonstrated more bone-implant contact. These results suggest that infection was reduced in the Van2 and Van5 groups. In contrast, blood values, histological grades, and bone-implant contact of the BAG and NAC groups were comparable with the Gel group. These results suggest that infection was not prevented in the BAG and NAC groups. Local application of vancomycin-loaded DAC-hydrogel successfully reduced implant-related infections. Loading of the hydrogel with BAG or NAC did not prevent infection. It is possible that BAG in powder form, as used in the present study, dissolved before the antibacterial effect could take place. Instead, BAG granules may be a viable alternative. Next, it is possible that the NAC concentration was too low to prevent infections in an in vivo environment, although this concentration was proven effective in vitro for its antibacterial properties

The clinical application of bone morphogenetic proteins (BMPs) offers solutions to many challenging problems in orthopaedics. However, a practical clinical problem is to obtain a controlled release of the BMPs. The attachment of heparin to biomaterials may result in an appropriate matrix for the binding, and sustained release of BMPs. Binding of growth factors to heparin stabilizes these growth factors, protects them from proteolytic degradation, and prolongs the half-life of BMPs in culture media 20-fold. We created a carrier based delivery system with a localized sustained release by loading a tricalciumphosphate/hydroxyapatite (TCP/HA) bone substitute coated with cross-linked collagen and heparin, with BMP-7. TCP/HA granules (BoneSave. ™. , Stryker Orthopaedics) were coated with collagen, and subsequently the collagen was cross-linked in the presence (TCP/HA-Col-Hep) and absence (TCP/HA-Col) of heparin. BMP-7 was loaded onto the coated TCP/HA granules. Morphology of the coated collagen with and without heparin, and release kinetics of BMP-7 from the granules were analyzed. TCP/HA granules without coating were used as controls. Analysis showed a highly porous collagen network on both TCP/HA-Col and TCP/HA-Col-Hep granules. Immersion of the granules in BMP-7 solution, resulted in the binding of 54±3% (62.9±5.4 ng BMP-7/mg granule) to the TCP/HA granules, 64±8% (69.0±9.6 ng BMP-7/mg granule) to the TCP/HA-Col granules, and 78±1% (92.9±4.8 ng BMP-7/mg granule) to the TCP/HA-Col-Hep granules. TCP/HA granules showed a burst release of BMP-7 within the first 4 h. TCP/HA-Col granules showed an initial burst release, followed by a more gradual release. In contrast, BMP-7 release from the TCP/HA-Col-Hep granules was sustained up to 21 days. The sustained delivery system for BMP-7 developed in this study may provide a powerful tool for bone regeneration. This system could probably also be applied to deliver multiple growth factors that have affinities for heparin, which could for instance synergistically enhance osteogenesis by increasing vascularity