In joint prostheses using ultra-high molecular weight polyethylene (UHMWPE) as bearing material, wear problems are not yet completely solved under severe conditions in various daily activities, although efficacious treatments such as crosslinking, addition of vitamin E and the grafting of phospholipid polymer improved the wear properties. In contrast, in healthy natural synovial joints possessing articular cartilage as biphasic bearing material lubricated with synovial fluid, minimal wear with extremely low friction has been maintained for a whole life. Therefore, the joint prosthesis with artificial hydrogel cartilage with similar properties to articular cartilage is expected to show superior tribological functions with very low friction and infinitesimal wear if the appropriate lubrication mechanism is actualized. In this study, the effectiveness of biphasic lubrication mechanism in hydrogel through significant load support by fluid phase is evaluated in finite element (FE) analysis for reciprocating motion. As biocompatible artificial hydrogel cartilage materials, two kinds of poly (vinyl alcohol) (PVA) hydrogels were prepared by the repeated freezing-thawing method and the cast-drying method, which are physically crosslinked with hydrogen bonding but different in structure and mechanical properties. To evaluate these time dependent behaviors of load-support ratio of fluid/solid phases and friction, two-dimensional biphasic FE analysis for cylindrical PVA hydrogel cartilage as 1.5 mm thick soft layer and radius of 5 mm was conducted under continuous loading of 0.2 N/mm by impermeable rigid plate in reciprocating motion in Fig. 1. The sliding speed is 4 mm/s for stroke of 8 mm at period of 4 s. A commercial package ABAQUS (6.8–4), which was appropriately evaluated for the biphasic FE analyses, was used in this study. The biphasic tissue was modeled by CPE4RP (four-node bilinear displacement and pore pressure, reduced integration with hour glass control) elements. The mechanical properties such as permeability, Young's modulus and Poisson ratio were estimated by curve fitting to stress relaxation behaviors in compression test. As indicated in Fig. 2, it is worth noting that the cast-drying PVA shows significant interstitial fluid pressurization compared with a repeated freezing-thawing PVA hydrogel at 292 s after start-up, where coefficient of friction for solid-to-solid was assumed as 0.2. Changes in friction for PVA hydrogels in reciprocating motion were estimated as shown in Fig. 3. In spite of high friction (0.2) for solid-to-solid, cast-drying PVA brought the gradual decreasing in friction, probably due to rising of load-support ratio by fluid phase from initial 74% to 80%. In human body, lubricating constituents in synovial fluids such as hyaluronic acid, proteins, glycoproteins and phospholipids can reduce the coefficient of friction for solid-to-solid. As suggested for low coefficient of friction for solid-to-solid as 0.01 in Fig. 3, rubbing friction is expected to be reduced to significantly low level. As described above, the effective biphasic lubrication can sustain low friction level and minimal wear in synergistic action with soft-elastohydrodynamic lubrication, hydration lubrication and boundary lubrication as a similar mechanism to natural cartilage in various daily activities. These results indicate the usefulness of artificial hydrogel cartilage for longer durability in joint prostheses for clinical application

Aim. In vivo studies have shown a preventive and curative effect of using an injectable vancomycin containing biphasic ceramic in an osteomyelitis model. No clinical long term pharmacokinetic release study has been reported. Inadequate concentration in target tissues results in treatment failure and selection pressure for antibiotic-resistant organisms. Our hypothesis was that vancomycin in the first week would reach high local concentrations but with low systemic levels. Method. 9 patients (6 women, 3 men) with trochanteric hip fractures classified as A1 and A2 according to the AO-classification all had internal fixations. The mean age was 75.3 years (± S.D. 12.3 years, range 44–84y). An injectable ceramic with hydroxyapatite embedded in a calcium sulphate matrix containing 66mg vancomycin per mL augmented the fixation. A mean of 9.7 mL (± S.D. 0.7 mL, range 8–10mL) was used. The elution of vancomycin was followed by collecting drain fluid, blood (4 days) and urine (4 weeks). Results. The concentration of antibiotics in the drain showed an important burst during the first 12h after surgery, with a mean value of 709.9 µmol/L (± S.D. 383.9), which decreased linearly to a mean value of 60.9 µmol/L at 2.5 days. In the urine, the vancomycin concentration reached 68.9 µmol/L (± S.D. 34.4) during the first day, which was decreased logarithmic over the first two weeks to reach zero at 20 days (see Figure). The systemic concentration of vancomycin was constantly low, not exceeding 2.6 µmol/L. Conclusions. This is the first long term pharmacokinetic study reporting vancomycin release from a biphasic injectable ceramic bone substitute. The study shows initial high targeted local vancomycin levels (wound drainage), sustained and complete release at three weeks (verified by the urine concentrations), and systemic concentrations well below toxic levels. This system should be useful in preventing and treating bone infection

To demonstrate the role of an antibiotic containing bone substitute, native bone active proteins and muscle transforming into bone.

Recurrent osteomyelitis was eradicated and filled with a gentamycin eluting bone substitute (Cerament™l G) consisting of sulphate and apatite phases and covered by a muscle flap.

A chronic, longstanding, fistulating osteomyelitis was operated with radical eradication and filling of the cavity with gentamycin eluting bone substitute. At one year, the patient had no leg pain and a healed wound. Significant bone was also seen in the overlaying muscle, at one month post-op disappearing after 6-months. Local delivery of gentamycin had a protective effect on bone formation.

Bone substitute with gentamycin leads to differentiation of mesenchymal cells into bone in-vitro.

Autologous bone grafting for bone defect reconstruction is associated with complications including donor site morbidity, infection risk, pain and surgical time. Therefore, bone graft substitutes provide an alternative for distinct indications and different characteristics with regard to their mechanical properties and resorption rates. In order to fill the loss of bone substance and to control the infection, we tried the efficacy of Cerament™G, a new absorbable composite of Calcium Sulphate and Hydroxyapatite with Gentamicin.

We present 3 male patients aged between 45 and 68 years affected by post-traumatic severe septic non union of femur, tibia and foot. The first patient with femur fracture was involved in a car accident (mixed flora Acinetobacter Baumanii, MRSA and Klebsiella pneumoniae carbapenemase (KPC)-producing), the second patient with femur and foot fracture falled by height in a work accident (MRSA) and the third one had a chronic tibial osteomyelitis several years after a road accident (Pseudomonas Aeruginosa). All 3 patients had undergone previous surgery. The first patient had several operations including multiple bone resection and debridement with external fixator, occlusion of superficial femoral artery with arterial bypass and finally debridement with implantation of Cerament™ G with external fixator and long term antibiotic therapy. The other 2 patients were subjected to resection of tissue septic with debridement, implantation of Cerament™ G and soft tissue closure and systemic antibiotics. Clinical and radiographic outcome were assessed at final follow-up (mean 8 months; range 8–18)

The follow-up was 8–18 months with examining clinical, radiographic, CT scan and laboratory tests. The patients had self-limiting fluid leakage. There was no recurrence of infection during the follow-up period. Bone ingrowth occurred in all cases with limb shortening.

Cerament™ G gives good elution of antibiotic and allows bone ingrowth. The implantation of Cerament™ G was associated with good clinical outcomes and satisfactory bone consolidation.

We acknowledge Antonella Esposito for septic nursing assistance

Total hip and knee joint prostheses composed of ultra-high molecular weight polyethylene (UHMWPE) and metal or ceramics have been widely applied. Efficacious treatments such as crosslinking, addition of vitamin E and phospholipid coating to UHMWPE have reduced wear and extended the life of joint prostheses. However, wear problems have not yet been completely solved for cases involving severe conditions, where direct contact can occur in mixed or boundary lubrication. In contrast, extremely low friction and minimum wear are maintained for a lifetime in healthy natural synovial joints containing articular cartilage with superior lubricity. Accordingly, joint prostheses containing artificial hydrogel cartilage with properties similar to those of articular cartilage are expected to show superior tribological functions. In establishing the function of artificial hydrogel cartilage as a novel material for joint prostheses, the tribological properties of hydrogel materials used and synergistic performance with synovia constituents are both important. In this study, the lubrication ability and wear resistance properties of poly(vinyl alcohol) (PVA) hydrogels were evaluated by differences in friction and wear properties in reciprocating tests lubricated with saline and simulated synovial fluid. Biphasic finite element (FE) analysis was applied to elucidate the role of biphasic lubrication mechanism in hydrogels. As biocompatible artificial hydrogel cartilage materials, three PVA hydrogels were prepared using the repeated freeze-thawing (FT) method, the cast-drying (CD) method and the hybrid method for laminated gel of FT on CD, which are physically crosslinked with hydrogen bonding but differ in terms of structure and mechanical properties. First the frictional behavior of the ellipsoidal PVA hydrogel specimens was examined in reciprocating tests against a glass plate, which corresponds to simplified knee prosthesis model (Fig.1), with a sliding speed of 20 mm/s under constant continuous loading. As shown in Fig.1, the three hydrogels exhibited different frictional behaviors in a saline solution. It is noteworthy that the hybrid gel maintained very low friction until the end of test. The CD gel showed slightly higher friction and a gradual increase. Meanwhile, the FT gel showed initial medium friction and a gradual increase. Time-dependent frictional behavior was clarified with biphasic lubrication mechanism via biphasic FE analysis. Contact surface observation showed minimal wear without scratches for hybrid gel in saline. Next, simulated synovial fluid composed of 0.5 wt% hyaluronic acid (HA, molecular weight: 920,000 Da), 1.4 wt% albumin, 0.7 wt% gamma-globulin and 0.01 wt% L-alpha dipalmitoylphosphatidylcholine (DPPC), was used to evaluate tribological performance of these gels in physiological condition. As shown in Fig.2, PVA hydrogels in simulated synovial fluid exhibited very low friction, with hybrid gel showing an extremely low friction coefficient of 0.003 in the test. These friction differences were sustained by biphasic FE analysis. Hybrid gel further showed very little wear (Fig.3), which is favorable in terms of hydrogel durability. These results indicate the importance of superior lubricity and wear resistance of PVA hybrid gel for the clinical application of artificial hydrogel cartilage in joint prostheses

Introduction. Wear and corrosion of metal-on-metal (MM) bearings releases (a) soluble metal ions which collect locally and pass into the systemic circulation and (b) insoluble particles which undergo local deposition and lymphoreticular dissemination. Debris-related failures from osteolysis, metallosis and pseudotumours warrants revision of these MM bearing devices to non-MM bearing arthroplasties with the expectation that both the systemic and local effects will be reversed with time since the source of metal ion release is removed. The purpose of the present study is to determine (a) whether metal ion levels in blood and urine decrease after revision of a MM bearing arthroplasty to a non-MM bearing device and (b) the rate at which this decrease is effected. Methods. Blood and urine levels of cobalt and chromium ions are studied prospectively over two years in 15 patients whose MM resurfacings were revised to cross-linked polyethylene containing total hip replacements (THRs). Specimen collection was started before and periodically after the revision at 2, 4 and 6 days and 2 months, 6, 12 and 24 months after operation. None of the patients had other MM devices or compromised renal function. Results. Pre-revision mean urine-cobalt was 676 nmol/day (range 84 to 1691 nmol/day) and urine-chromium 348 nmol/day (range 68 to 804 nmol/day). As anticipated these are higher than the expected levels in patients with well-functioning metal-on-metal bearings. Post-revision metal levels decrease in a biphasic manner. Over the first week there is a rapid decline to 235 nmol/day cobalt and 217 nmol/day chromium followed by a period of slow decrease over the next 24 months to 10 nmol/day cobalt and 44 nmol/day chromium. Blood cobalt also shows a similar biphasic decrease from a preoperative level of 151 nmol/L to 79 nmol/L during the first week and further reduction to 13 nmol/L over the following 2 years and with blood chromium the reduction is from 103 nmol/L preoperative to 64 in the first week and on to 14 nmol/L at 2 years. Discussion and Conclusion. A limitation of the study is the small cohort of 15 patients with a wide range of pre-revision blood and urine levels. However the same biphasic trend as seen in the group is evidenced in each individual patient which gives us confidence that the trend will not be different in much larger groups of patients. The early steep reduction following revision supports the reported short half-life of cobalt. The later protracted trend is explainable through progressive corrosion from deposited particles. This trend is also not sustained indefinitely and tends to approach control levels at 2 years

Osteoarthritis (OA) is a debilitating disease characterised by degradation of articular cartilage and subchondral bone remodeling. Current therapies for early or midstage disease do not regenerate articular cartilage, or fail to integrate the repair tissue with host tissue, and therefore there is great interest in developing biological approaches to cartilage repair. We have shown previously that platelet-rich plasma (PRP) can enhance cartilage tissue formation. PRP is obtained from a patient's own blood, and is an autologous source of many growth factors and other molecules which may aid in healing. This raised the question as to whether PRP could enhance cartilage integration. We hypothesise that PRP will enhance integration of bioengineered cartilage with native cartilage. Chondrocytes were isolated from bovine metacarpal-phalangeal joints, seeded on a porous bone substitute (calcium polyphosphate) and grown in the presence of FBS to form an in vitro model of osteochondral-like tissue. After 7 days, the biphasic constructs were soaked in PRP for 30 minutes prior to implantation into the core of a ring-shaped biphasic explant of native bovine cartilage and bone. Controls were not soaked in PRP. The resulting implant-explant construct was cultured in a stirring bioreactor in serum free conditions for 2 weeks. The integration zone was visualised histologically. A push-out test was performed to assess the strength of integration. Matrix accumulation at the zone of integration was assessed biochemically and the gene expression of the cells in this region was assessed by RT-PCR. Significance (p<0.05) was assessed by a student's t-test or one-way ANOVA with tukey's post hoc. PRP soaked bioengineered implants, integrated with the host tissue in 73% of samples, whereas control bioengineered implants only integrated in 19% of samples based on macroscopic evaluation (p<0.05). The integration strength, as determined by the normalised maximum force to failure, was significantly increased in the PRP soaked implant group compared to controls (219 +/− 35.4 kPa and 72.0 +/− 28.5 kPa, respectively, p<0.05). This correlated with an increase in glycosaminoglycan and collagen accumulation in the region of integration in the PRP treated implant group, compared to untreated controls after 2 weeks (p<0.05). Immunohistochemical studies revealed that the integration zone was rich in collagen type II and aggrecan. The cells at the zone of integration in the PRP soaked group had a 2.5 fold increase in aggrecan gene expression (p=0.05) and a 3.5 fold increase in matrix metalloproteinase 13 expression (p<0.05) compared to controls. PRP soaked bio-engineered cartilage implants showed improved integration with native cartilage compared to non-treated implants, perhaps due to the increased matrix accumulation and remodeling at the interface. Further evaluation is required to determine if PRP improves integration in vivo

Introduction. Novel hydrogel implants, TRUFIT® bone plugs, have been developed by Smith & Nephew to replace worn-out cartilage surfaces, restoring mobility and relieving joint pain. There is limited information, however, on the biomechanical properties of the implants. Therefore, appropriate mechanical testing and modelling must be carried out to assess their mechanical properties for load bearing applications. In this study, compressive properties of TRUFIT® bone and dual layer implants were examined under selected physiological loading conditions. The bone layer of the implant was also modelled using a biphasic poroviscoelastic (BPVE) material constitutive law and the results from the model are compared with those from the experiments. Materials and Methods. TRUFIT® CB plugs, with diameters of 11 and 5mm, were sectioned to obtain single layer bone and dual layer samples, with an aspect ratio of 0.86. Specimens were tested in confined and unconfined compressions at two constant strain rates of 0.002/sec (walking) and 0.1/sec (impact) [1-3] on a MTS servo-hydraulic test machine equipped with a bionix envirobath. All samples were tested in phosphate buffered saline (PBS) solution at 37 °C. A preload of 0.1 MPa was applied and preconditioning (10 cycles of 0.008 strain) at a constant strain rate of 0.005 sec. −1. [4] was used. The compressive modulus was calculated from the slope of the linear part of the stress-strain curve. In addition, whilst stress relaxation tests were performed on the bone samples in unconfined compression up to 5% strain, at a strain rate of 0.01/s (running) [1-2]. Biphasic Modelling. The bone implant was modelled as a biphasic poroviscoelastic (BPVE) material assuming constant permeability and linear viscoelasticty. An axisymmetric finite element model of the implant in unconfined compression was built using FEBio [5], with 8-node tri-linear displacement and pore pressure elements. The governing equations for linear BPVE theory are summarized in [6]. Six material coefficients were obtained to describe the model, as shown in Table 1. E and µ are the Young's modulus and Poisson coefficient of the solid matrix; k is the hydraulic permeability; G∗, t. 1. and t. 2. represent the discrete relaxation spectrum magnitude and time relaxation constants used to describe the intrinsic viscoelastic nature of the solid matrix. The Young's modulus of the solid matrix was calculated from the equilibrium stress versus strain in the linear range. The Poisson coefficient of the porous solid matrix was determined also from 3D in situ step-wise compressive tests using Digital Volume Correlation. Permeability measurements were performed, where steady state flow rate versus pressure gradient was measured and the hydraulic permeability was calculated using the Darcy's law. An inverse iterative FE technique was used to identify the remaining coefficients from the stress relaxation experiments. Results & discussion. The compressive moduli are summarized in Fig 1. The preliminary results seem to suggest that strain rate seems to have a dominant effect on compressive modulus. Higher strain rate would always result in higher modulus. On the other hand, the influence of confinement seems to be small. Higher moduli were observed for bones. Smaller sized (5mm) bone samples seem to have a higher modulus at both strain rates. For plugs, significantly higher modulus was found for 5mm samples in walking but similar results were obtained in impact. Fig. 2 shows a typical curve fitting exercise of the BPVE model using the experimentally determined stress relaxation curve (R. 2. =0.95), from which model parameters were obtained. The BPVE model is able to account for the initial, transient and stationary regime of stress relaxation. Moreover, the model is able to reproduce the monotonic unconfined compressive responses at two strain rates (walking and impact), as illustrated in Fig. 3. Acknowledgements. The authors would like to thank Smith & Nephew for providing the samples

Various treatments for ultra-high molecular polyethylene (UHMWPE) such as cross-linking, addition of vitamin E and the grafting of phospholipid polymer improved the wear properties. However, wear problems still occur in joint prostheses in mixed or boundary lubrication modes under severe conditions. As an alternate method, the joint prosthesis with artificial hydrogel cartilage with similar properties to articular cartilage is expected to show superior tribological functions with very low friction and low wear if the adaptive multimode lubrication mechanism is actualized. In this study, the effectiveness of hydrogel structure and adsorbed film formed on artificial cartilage surfaces is examined in reciprocating tests in related to biphasic, hydration and boundary lubrication modes. The frictional behaviors of artificial cartilage materials against flat glass plate in the reciprocating test were observed. As upper specimens, poly(vinyl alcohol) (PVA) hydrogel ellipsoidal specimen as 2 mm soft layer were prepared. PVA hydrogel specimens were prepared by the repeated freezing-thawing method and the cast-drying method. The sliding speed and stroke length were 20 mm/s and 35 mm, respectively. Applied load was 2.94 N or 9.8 N. The lubricants are saline or saline solutions containing L-α-Dipalmitoyl phosphatidyl-choline (DPPC), serum protein and/or hyaluronate(HA). As shown in Fig. 1, the repeated freezing-thawing PVA shows gradual increase in friction from initial medium value immediately after loading of 2.94 N to high level. For the same test condition, the articular cartilage exhibited similar time-dependent frictional behavior from initial lower friction to high level as estimated by biphasic lubrication theory. On the contrary, it is noticed that a low friction is maintained for cast-drying PVA hydrogel, particularly two-layer laminated PVA hydrogel until 140 m sliding. The improvement of frictional behaviors in cast-drying PVA hydrogel is considered to have been brought about by the improvement of water retention ability of the hydrogel with uniform microstructure controlled by hydrogen bond. Next, the influence of lubricant constituents on tribological behaviors of freezing-thawing PVA hydrogel was examined in repeated reciprocating test including unloading-restarting process at each 36 m sliding at 9.8 N. The frictional behavior for the freezing-thawing PVA hydrogel could be improved with supplying appropriate lubricant constituents as shown in Fig. 2. In lubricated condition with HA solution containing 0.01 wt% DPPC, 1.4 wt% albumin and 0.7 wt% γ-globulin, low friction was maintained and very little visible wear was confirmed in micrograph. Adsorbed films appear to contribute to the effective synergistic lubrication even under high load of 9.8 N in reciprocating test. As described above, the effectiveness of synergistic lubrication for PVA hydrogel specimens is shown for improvement of tribological behaviors of artificial cartilage as a superior mechanism to natural cartilage. These results indicate the possibility of artificial hydrogel cartilage for longer durability in joint prostheses for clinical application

Introduction. Hip implant research has been carried out for decades using hip simulators to reflect situations in vivo. With regards to metal on metal (MoM) implant testing, it has been reported that there is no significant difference between the wear generated by various cobalt chromium (CoCr) microstructures. On the contrary, higher wear, metal ion levels and subsequent failures have been reported in heat treated (high carbon, low carbide) devices compared to as cast (high carbon, high carbide) devices in vivo. During testing, the bearing surfaces may be masked from the effect of microstructure on wear under fast and continuous cycles, while in vivo, the extensive range of kinetics and kinematics, stop/start motion, varying walking frequencies could break down the fluid film, resulting in a less favourable lubrication regime. The aims of this study were to develop a more physiologically relevant hip simulator test protocol, and investigate the effect of microstructure on wear. Materials & Methods. Three pairs of 50mm as cast (AC) and four pairs of 50mm double heat treated (DHT) CoCr MoM devices were tested in a ProSim hip simulator. In order to determine the frequency for testing, Patients' activities have been monitored using a Step Activity Monitor (SAM) device. The data showed a relatively slower walking pace (frequency) than that used in the hip simulator studies. The new frequency, along with stop/start motion and various kinetics and kinematics profiles have been used in putting together a more physiologically relevant hip simulator test protocol. The lubricant used in this study was new born calf serum with 0.2 % (w/v) sodium azide concentration diluted with de-ionised water to achieve an average protein concentration of 20 g/l. Gravimetric measurements have been taken at 0.5, 1, 1.5 & 2 million cycle (Mc) stages and ion analysis has been carried out on the serum samples. Results & Discussions. A biphasic wear pattern similar to the parts in vivo was observed. Under the newly developed physiologically relevant test conditions, the DHT CoCr devices generated 40% higher wear than the AC CoCr devices (Figure 1). The metal ion analysis results also showed a similar biphasic wear trend, however, the difference between the AC and DHT devices was further increased by approximately 30 % at 2 Million cycle stage (Figure 2). It has been reported that the DHT devices generate smaller size particles and in much larger numbers compared to those generated by the AC devices. This would result in a larger net surface area of the wear particles exposed to corrosion and thus would contribute to a higher amount of metal ion levels with the DHT devices compared to AC devices. Conclusion. The in vitro results obtained with the new test protocol correlate well with the in vivo results. The higher wear, metal ion levels observed with double heat treated CoCr devices compared to as cast CoCr in vivo were also represented in vitro, highlighting the effect of microstructure on wear

Aims. Dead space management is an important element in the surgical management of chronic osteomyelitis and can be addressed with the use of a biodegradable local antibiotic carrier. We present the clinical and radiographic outcomes in two different biodegradable antibiotic carriers used in the management of chronic osteomyelitis. Method. A single centre series reviewed between 2006–2017. The initial cohort (2006–2010) of 180 cases (Group A) had a calcium sulphate carrier containing tobramycin (Osteoset. ®. T, Wright Medical). The second cohort (2013–1017) of 162 cases (Group B) had a biphasic calcium sulphate, nano-crystalline hydroxyapatite carrier containing gentamicin (Cerament. TM. G, Bonesupport AB). All cases were Cierny-Mader Grade III and IV and had a minimum of one-year clinical follow-up. Clinical outcomes reviewed included infection recurrence rate, wound leak, and subsequent fracture involving the treated segment. All cases with a minimum one-year radiographic follow-up were reviewed and bone void filling was assessed as percentage filling on the final follow-up radiograph to the nearest five percent increment. Results. Mean follow-up in Group A was 4.2 years (range 1.3–10.5 years) and in Group B it was 1.8 years (1–4.7 years). Group A had a significantly higher rate of infection recurrence (19/180 (10.6%) Vs. 7/163 (4.4%) p=0.030), wound leak (33/180 (18.3.%) Vs. 16/162 (9.9%) p=0.026) and subsequent fracture rate (11/180 (6.1%) Vs. 3/162 (1.9%) p=0.047) compared to Group B. Of the cases with a minimum of one-year radiographic follow-up Group A had 96 cases (mean follow-up 3.3 years, range 1.0–10.5 years) and Group B had 137 cases (mean follow-up 1.6 years, range 1.0–4.7 years). The mean bone void healing in Group B was significantly better than Group A (74.0% Vs. 41.7%, p <0.00001). Conclusions. Cerament. TM. G has significantly better bone healing compared to a calcium sulphate carrier and was associated with a lower rate of recurrent infection, wound leak and subsequent fracture risk

Aim. The optimal treatment of displaced intra-articular calcaneal fractures (DIACF) remains controversial. The operative treatment group has better anatomical recovery, functional outcome scores and less pain than non operative treatment patients, but it may lead to a higher incidence of complications, such as delayed wound healing and surgical site infections. The aim of this study was to analyze the prophylactic effect using a biphasic bone substitute (BS) eluting antibiotic on calcaneal implant-related infections. Methods. We conducted a retrospective non-randomized review of all patients with DIACF (type Sanders 2, 3, 4) from 2009 to 2017; 103 calcaneal fractures of 90 patients (13 bilaterally) were treated with plates. All cases received the same systemic antibiotic prophylaxis; BS was used on more complex cases with large bone defect and BS was added with antibiotic on higher risk patients. We collected data including complications: major (deep infections, osteomyelitis) and minor complications (wound dehiscence, superficial infection). We considered the absence of deep infections after 6 months. We compared statistically the outcomes of 3 operative groups: the first was treated with plates only (A), the second with plates and BS (B) and the third with plates added with BS eluting antibiotic (vancomicine or gentamicine) (C). Results. We examined 99 cases (group A: n33, B: n52, C: n14), 4 patients were lost; the mean age was 47,8 years (range 18–83 years). Minimal follow up was 6 months (range: 6 – 42 months). We have observed 8 (8,1%) implant-related infection (A:4, 12,1%; B:4, 7,7%), 2 (2%) superficial infection (B:2, 3,8%), 20 (20,2%) wound healing defects (A:11, 33,3%; B:7, 13,5%; C:2, 14,2%). We found a relevant reduction of the rates in the group C regarding the major complications without a statistic evidence. Conclusion. The three groups are uneven; particularly the group C has a high concentration of more severe risk patients. The low number of cases in the group C, which limited the statistic evidence, represents a second limit. The absence of major infection on group C found in this study, needs larger data to confirm this result. The open surgery has an intrinsic rate of skin complications but the use of BS eluting local antibiotic is an additional tool to manage difficult complex fractures and to prevent implanted-related infection, inhibiting bacterial colonization and biofilm protection, particularly in those patients that have suffered from a minor complication, which could lead to a deep infection

Aim. Open fractures with bone defects and skin lesions carry a high risk of infection potentially leading to prolonged hospitalization and complication requiring revision procedures. Treatment options for diaphyseal fractures with soft tissue lesions are one- or two-stage approaches using external fixation or intramedullary nailing. We describe a surgical technique combining intramedullary nailing with an antibiotic-eluting biphasic bone substitute (BBS) applied both at the fracture site, for dead-space management and infection prevention, and on the nail surface for the prophylaxis of implant-related infection. Method. Adult patients with an increased risk of bony infection (severe soft tissue damage and open fractures of Gustilo-Anderson grades I and II) were treated with debridement followed by application on the intramedullary nail surface, in the canal and at the fracture site of a BBS with prolonged elution (to 28 days) of either gentamicin or vancomycin. All patients also received systemic antibiotic prophylaxis following surgery. Data on infections and other adverse events were collected throughout the follow-up period. Bone union was determined by radiographic assessment of 4 cortices in radiographs obtained 1 year after surgery. Results. In this prospective, non-randomized case series a total of 6 patients were treated: 4 tibia (2 male, 2 female), 1 femur (female) and 1 humerus (male). The mean age of the patients was 28 years (range 18–51 years). Two patients had a history of smoking and 1 patient had a history of diabetes. Minimal Follow up was 12 months (range: 12 – 30 months). One to two weeks postoperatively, partial load bearing (20 kg) was allowed with free mobility of joints. Bone samples from the fracture site following debridement showed the presence of bacteria in 2 cases. No infections were observed during follow-up. Radiographs showed that the bone substitute was resorbed and also a gradual bony union of the fractures. All patients had good clinical outcomes. Conclusions. The addition of a BBS which elutes antibiotic locally in the dead-space of exposed fractures and at the implant surface prevents bacterial colonization and biofilm formation. The injectable composite we used enhances safety in higher risk patients, is easy to use in combination with intramedullary nailing and offers the opportunity for a one-stage procedure. Local administration of antibiotics at the fracture site provides an additional tool to manage difficult-to-treat complex fractures and implant-related infections. Larger studies are needed to confirm these results. *CERAMENT G or V, BONESUPPORT AB

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.

Endoprosthetic reconstruction for pathologic acetabular fractures is associated with a high risk of periprosthetic joint infection. In this setting, bone defect reconstruction utilising co-delivery of a synthetic bone substitute with an antibiotic, is an attractive treatment option from both, therapeutic and prophylactic perspective. We wished to address some concerns that remain regarding the possible presence of potentially wear inducing particles in the periprosthetic joint space subsequent to this procedure. We analysed a drain fluid sample from an endoprosthetic reconstruction of a pathologic acetabular fracture with implantation of a gentamicin eluting, biphasic bone graft substitute, consisting of 40% hydroxyapatite (HA) and 60% calcium sulphate (CERAMENT G), into the residual peri-acetabular bone defect. This sample was divided into two 1.5ml subsamples, to one of which 100mg HA particles were added as control before burning off all organic substance at very high temperature. These heat treated samples were then examined with scanning electron microscopy (SEM) and energy dispersive x-ray analysis (EDAX) and compared to a reference sample consisting of HA particles only. On SEM, hydroxyapatite particles were readily recognisable in the control and reference samples, whereas only very few particles over 2μm were apparent in the ”pure” drain sample. EDAX revealed that very large amounts of salts were present in both drainage samples. The pure drainage sample however, contained markedly lower amounts of calcium and phosphate compared to reference and control samples. No HA particles as such, were seen in the pure sample, however their presence cannot be excluded with absolute certainty, as some particles might have been hidden within the large salt conglomerates. We could not find clear evidence that the drain fluid really contained HA particles. More thorough investigations are needed and future analyses with prior removal of the high salt content would likely yield more conclusive results

Introduction. Geometric variations of the hip joint can give rise to abnormal joint loading causing increased stress on the articular cartilage, which may ultimately lead to degenerative joint disease. In-vitro simulations of total hip replacements (THRs) have been widely reported in the literature, however, investigations exploring the tribology of two contacting cartilage surfaces, and cartilage against metal surfaces using complete hip joint models are less well reported. The aim of this study was to develop an in-vitro simulation system for investigating and comparing the tribology of complete natural hip joints and hemiarthroplasties with THR tribology. The simulation system was used to assess natural porcine hip joints and porcine hemiarthroplasty hip joints. Mean friction factor was used as the primary outcome measure to make between-group comparisons, and comparisons with previously published tribological studies. Method. In-vitro simulations were conducted on harvested porcine tissue. A method was developed enabling natural acetabula to be orientated with varying angles of version and inclination, and natural femoral heads to be potted centrally with different orientations in all three planes. Acetabula were potted with 45° of inclination and in the complete joint studies, natural femoral heads were anatomically matched and aligned (n=5). Hemiarthroplasty studies (n=5) were conducted using cobalt chrome (CoCr) heads mounted on a spigot (Figure 1), size-matched to the natural head. Natural tissue was fixed using PMMA (polymethyl methacrylate) bone cement. A pendulum friction simulator (Simulator Solutions, UK), with a dynamic loading regime of 25–800N, ± 15° flexion-extension (FE) at 1 Hertz was used. The lubricant was a 25% (v/v) bovine serum. Axial loading and motion was applied through the femoral head and frictional torque was measured using a piezoelectric transducer, from which the friction factor was calculated. Results. The correct anatomical orientation and positioning was achieved enabling in-vitro simulation testing to be conducted on hemiarthroplasty and complete hip joint samples for two-hours. Mean friction increased rapidly followed by a continued gradual increase to ≈0.03 ± 0.00 in the complete joints, with the hemiarthroplasty group plateauing at ≈0.05 ± 0.01 (Figure 2). Mean friction factor was significantly lower (t-test; p < 0.05) in the complete natural joint group. Discussion. An in-vitro simulation system for the natural hip joint with controlled orientation of the femur and acetabulum was successfully developed and used to measure friction in complete porcine hip joints and porcine hip hemiarthroplasties. A non-linear increase in friction indicative of biphasic lubrication was observed in both groups with slower exudation of fluid from the complete joints compared to the hemiarthroplasties, inferring a quicker move towards solid-phase lubrication. Higher friction in the hemiarthroplasties, which was similar to that measured in-vitro in metal-on-polyethylene THRs, was most likely due to variable clearances between the non-conforming spherical metal head and aspherical acetabulum, causing poorer congruity and distribution of the load. This could in time lead to abrasive wear and cartilage degradation. This methodology could have an important role when investigating associations between hip geometric variations, interventions for hip disease/pathology, and risk factors for cartilage degeneration

Introduction. Hemiarthroplasty is an attractive technique for young and active patients as it preserves more bone stock. Polycarbonate urethane (PCU) has recently been introduced as an alternative bearing material. DSM Biomedical BV (Geleen, The Netherlands) has modified Bionate. ®. PCU 80A (80AI) with C18 groups and produce Bionate. ®. II PCU 80A (80AII) to create a different biointerface and enhance its tribological properties. The aim of this study was to compare friction performance of the articulation of the cartilage against 80AI and 80AII in various lubricants. Materials and Methodology. A customised multidirectional pin-on-plate reciprocating rig (Fig. 1) was used to perform friction tests of ovine femoral condyles as they articulated against PCU 80A discs (diameter 38 mm, thickness 3.2 mm). The average surface roughness of the cartilage and the PCU discs was approx. 450 nm and 10 nm respectively. 30% (v/v) bovine calf serum (BCS) and bovine synovial fluid (BSF) were used as lubricants. Prior to testing, each disc was fully hydrated in its test lubricant for 6 days. During testing, a static compressive load of 20 N was applied (an average stress of approx. 0.95 MPa). The sliding distance was 25 mm with ±15° rotation over the length of the stroke to produce cross shear. Each test lasted 15 h at a frequency of 1 Hz. Lubricant was kept at 37±1 °C throughout testing. The friction force was measured using full-bridge circuit strain gauges (Fig. 1). Results. The COF steadily increased during the first hour of testing due to the biphasic nature of the cartilage and then stabilized. Fig. 2 shows the average COF (mean ± 95% confidence limits, n=6) over 15 h. When BSF was used, the average COF decreased from 0.379±0.015 to 0.286±0.039 for 80AI and from 0.316±0.014 to 0.190±0.029 for 80AII, which found to be statistically significant (p = .004 and p < .0005 respectively). In both lubricants, the average COF for 80AII was statistically lower than that for 80AI (p < .0005 for BCS and p = .004 for BSF). Conclusion. Under the clinically-relevant conditions, the average COF varied with tested lubricants and polymers. The average COF reduced for both polymers when BSF was used. This might be because proteoglycan 4 (PRG4) adsorbs on cartilage surface [1], and thus possibly lowered the COF outcomes. In addition to PRG4, other molecules present in BSF (i.e. hyaluronan and lipids) might also have roles in reduced COF. Moreover, 80AII had a lower friction than 80AI as either lubricant was used. This can be attributed to the higher protein adsorption nature of 80AII, though further investigation is required. Furthermore, when BCS was used the mean COF for 316L stainless steel (0.358±0.032) was lower than that for 80AI (0.379±0.015), which was not statistically different (p = 0.277), and it was greater than that for 80AII (0.316±0.014), which was statistically significant (p = 0.039). In conclusion, 80AII showed statistically superior friction performance over 80AI and SS316L, which would be a potential hemiarthroplasty material among these three

Introduction. Currently, there is a focus on the development of novel materials to articulate against cartilage. Such materials should either eliminate or delay the necessity of total joint replacement. While cobalt-chromium (CoCr) alloy is still a material of choice and used for hemi-arthroplasties, spacers, and repair plugs, alternative materials are being studied. Pyrolytic carbon (PyC) is a biocompatible material that has been available since the 1980s. It has been widely and successfully used in small joints of the foot and the hand, but its tribological effects in direct comparison to cobalt-chromium (CoCr) remain to be investigated. Methods. A four station simulator (Figure 1), mimicking joint load and motion, was used for testing. The simulator is housed in an incubator, which and provides the necessary environmental conditions for cartilage survival. Articular cartilage disks (14mm in diameter) were obtained from the trochleas of six to eight months old steer for testing and free-swelling controls. Disks (n=8 per material) were placed in porous polyethylene scaffolds within polypropylene cups and mounted onto the simulator to articulate against 28mm balls of either PyC or CoCr. Each ball was pressed onto the cartilage disk with 40N. In order to allow fluidal load support, the contact migrated over the biphasic cartilage with a 5.2 mm excursion. Concomitantly, the ball oscillated with ±30° at 1 Hz. Testing was conducted for three hours per day over 10 days in Mini ITS medium. Media samples were collected at the end of each three hour test. Upon test commencement, media was pooled (days 1, 4, 7, 10) and analyzed for proteoglycans/sGAGs and hydroxyproline. In addition, total material release into media was estimated by determining the dry weight increase of media samples. For this purpose, 1 ml aliquots of fresh and test media were dialyzed, lyophilized and weighed on a high precision balance. Disk morphology and cell viability were histologically examined. Results. During each day of testing, cartilage control, CoCr and PyC samples released an average of 0.236, 0.253, re 0.268 mg/mL of glycol-proteins into the medium. After running-in (day 1), the increase was highly linear (R. 2. >0.99) and similar for all three testing conditions. Proteoglycan/GAG (Figure 2) and hydroxyproline release (Figure 3) were also similar for both materials (p=0.46 re. p=0.12), but significantly different from control (p<0.01). Histological and cell viability images support the hypothesis of superficial zone damage of the cartilage disks for both materials. Cell viability was not different from control (p>0.33). Discussion. The performance of PyC and CoCr was comparable using this in vitro simulation model, however appears not optimal. The observed surface fibrillation may lead to tissue breakdown in the long-term. The wear mechanism has yet to be elucidated but appears to be of adhesive nature. The lack of proteins in the medium might have suppressed boundary lubrication and thus may have played a role in the non-optimal performance of these materials. In summary, a live tissue model of articular cartilage found no difference comparing pyrolytic carbon with the current clinical gold standard CoCr

Introduction. Ceramic composites have been developed to further improve the mechanical properties, reduce risk of fracture, and increase the survivorship of ceramic-on-ceramic bearings in total hip replacement. 1. . The aim of this study was to evaluate the wear of two novel ceramic composite materials under edge loading conditions due to translational mal-positioning when used in both like-on-like and mixed pairing configurations; and to compare their performance to earlier generation ceramic-on-ceramic bearings. Materials and Methods. The head-on-cup configurations of three ceramic materials (see Figure 1), were ATZ-on-ATZ, ZTA-on-ZTA, Al. 2. O. 3. -on-Al. 2. O. 3. , ATZ-on-ZTA, ZTA-on-ATZ, Al. 2. O. 3. -on-ATZ, ATZ-on-Al. 2. O. 3. and Al. 2. O. 3. -on-ZTA. All combinations were size 28mm and were supplied by Mathys Orthopädie GmbH (Morsdorf, Germany). They were tested for four million cycles on the Leeds II hip simulator under microseparation. 2,3,4. conditions representing translational mal-positioning. The gait cycle comprised extension/flexion (−15º/+30º), internal external rotation (+/−10º) and a twin peak load with a maximum of 3kN. Microseparation was achieved by applying a 0.5mm dynamic medial/lateral displacement using a spring load resulting in edge loading at heel strike. New-born calf serum (25%) was used as a lubricant. Wear was assessed gravimetrically every million cycles. Statistical analysis was performed using one-way ANOVA (significance taken at p<0.05). Results. The wear of ATZ-on-ZTA, ATZ-on-Al. 2. O. 3. and Al. 2. O. 3. -on-Al. 2. O. 3. was biphasic with a bedding in wear rate between zero and one million cycles under translational malpositioning conditions and a lower steady state wear rate between one and four million cycles. The bedding in and steady state wear rates of ATZ-on-ZTA (1.16mm. 3. /million cycles bedding in and 0.18mm. 3. /million steady state) and ATZ-on-Al. 2. O. 3. (0.66mm. 3. /million cycles bedding in and 0.20mm. 3. /million steady state) were lower than that of Al. 2. O. 3. -on-Al. 2. O. 3. (1.54mm. 3. /million cycles bedding in and 0.55mm. 3. /million steady state) bearing combination (see Figure 2). However, there was statistically no significant difference (p=0.35) between the wear rates. The wear rates of the other bearing combinations under these adverse microseparation conditions, ZTA-on-ZTA and ATZ-on-ATZ, Al. 2. O. 3. -on-ATZ, Al. 2. O. 3. -on-ZTA, and ZTA-on-ATZ were very low with no clear bedding in and steady state phases (see Figure 1). The wear rates of these combinations, over the four million cycles of test under adverse microseparation conditions, were all lower than 0.14mm. 3. /million cycles. Discussion and Conclusion. The mixed material combinations (ATZ-on-ZTA, ATZ-on-Al. 2. O. 3. , Al. 2. O. 3. -on-ATZ, Al. 2. O. 3. -on-ZTA and ZTA-on-ATZ) tested in this study have shown slightly higher wear rates when compared to ATZ in like-on-like configuration, but superior wear resistance when compared to Alumina BIONIT® (Mathys) and BIOLOX® forte (CeramTec) Al. 2. O. 3. -on-Al2O. 3. bearings tested under the same adverse microseparation conditions

Carpal tunnel syndrome (CTS) is said to be a condition of middle-aged women. Our experience is that it more commonly occurs in older people and also in a younger working population. The aim of this study is to describe the epidemiology of CTS requiring carpal tunnel decompression (CTD). Over a 10.5 year period 3073 CTD were performed on 2309 patients aged 15 – 93 years. This included all public, private and ACC funded cases in our region. During this period we had no restriction to access to CTD as all publicly funded cases were performed under local anaesthetic in a day surgery unit. Neurophysiological studies were performed pre-operatively by the same neurophysiologist. Population data from the national census (2006) was used to calculate the annual incidence of patients requiring CTD for each 5 year age band. There were 1418 females (61.4%) and 891 males (38.6 %). In contrast females comprised 116 of 306 (37.8%) patients who had their surgery funded by ACC. The mean age at surgery was 45 years for ACC cases compared with 56 years for non-ACC funded cases. The incidence of males having surgery funded by ACC was 1.7 times higher than females. There was a biphasic pattern in females with an incidence of 3.0/1000 at age 50–54 years, and a second higher peak of 3.1 to 3.4/1000 from 70 to 5 years. Males had a linear increase in incidence peaking at 3.1/1000 for age 65–69 years declining slightly to 2.8/1000 for age 70–85 years. The incidence was significantly higher in females than males overall (1.8 v 1.1/1000) and in patients under 65 years (1.4 v 0.8/1000). In patients over 65 years there was no significant difference in incidence (female 2.8, male 2.5/1000). Within our region, the incidence of surgically treated carpal tunnel syndrome increases with age. The highest rates are seen over the age of 70 in women and 65 years in men with no significant difference in rates between men or women over 65 years