Introduction. PEEK-OPTIMA™ has been considered as an alternative bearing material to cobalt chrome in the femoral component of total knee replacements. To better understand the tribology of UHMWPE-on-PEEK-OPTIMA™ and to find the most appropriate environmental conditions under which to test this novel bearing material combination, a series of tests under different protein lubricant concentrations at rig (∼24°C) and elevated temperature (∼35°C) were carried out in simple geometry wear and friction rigs. Under all conditions, the wear of UHMWPE-on-PEEK-OPTIMA™ was compared to UHMWPE-on-cobalt chrome (CoCr). Methods. The pins used were GUR1020 UHMWPE (conventional, non-sterile) and the plate material was either polished CoCr (Ra<0.01µm) or PEEK-OPTIMA (Ra∼0.03µm) provided by Invibio Ltd, UK. The wear simulation was carried out in a six station reciprocating rig. The kinematic conditions were consistent for all tests and reflected the average cross shear and contact pressure (3.2MPa) in a total knee replacement. Tests were carried out at either rig running temperature (∼24°C) or at elevated temperature (∼35°C) and in varying protein lubricant concentrations (0, 2, 5, 25 and 90%). Wear of the UHMWPE pins was determined by gravimetric analysis. The pin-on-plate friction rig study was carried out at rig temperature in 0, 2, 5, 25 and 90% serum and reflected the contact pressure used in the wear tests. Measurements were taken using a piezoelectric sensor and the steady state friction derived. At least 3 repeats were taken for each study, statistical analysis carried out using ANOVA with significance taken at p<0.05. Results and Discussion. The influence of protein lubricant concentration and temperature on the wear of UHMWPE was different for the two bearing couples tested. In low serum concentrations (≤5%), polymer transfer was evident on the surface of the plates suggesting insufficient boundary lubrication and a non-clinically relevant wear mechanism. In 25% serum at rig temperature, the wear factor of UHMWPE-on-PEEK-OPTIMA™ was similar (p>0.05) to UHMWPE-on-CoCr at 2.00×10. −7. ±1.08×10. −7. mm. 3. /Nm and 2.15×10. −7. ±7.44×10. −8. mm. 3. /Nm respectively. Increasing the temperature of the lubricant lowered the wear factor of UHMWPE-on-PEEK-OPTIMA (9.93×10. −8. ±2.96×10. −8. mm. 3. /Nm); there was no influence of temperature on UHMWPE-on-CoCr (1.87×10. −7. ±6.14×10. −8. mm. 3. /Nm). The lower wear rate of the all-polymer couple was attributed to the elevated test temperature coupled with the higher friction of the all-polymer combination causing protein in the lubricant to come out of solution, adhere to the articulating surfaces and protect them from wear. In high serum concentrations (90%), protein deposition was visible on the surface of the plates and protein precipitation was visible in the lubricant. Under all protein lubricant concentrations, the coefficient of friction was higher for the all-polymer bearing couple than for UHMWPE-on-CoCr, at serum concentrations ≥2%, this difference was significant (p>0.05). Conclusion. Environmental conditions such as protein concentration and lubricant temperature influence wear and the effects of these variables can differ for different material combinations. For UHMWPE-on-PEEK-OPTIMA™, testing in 25% bovine serum at rig temperature minimised test artefacts such as polymer transfer, protein deposition and protein precipitation which suggests that these may be appropriate test conditions for this material combination

Introduction. Friction between head and cup is a primary factor for survival of total hip joint replacement (THR) and its gliding surfaces. In up to 40% of all revisions, the cup or inlay must be replaced as result of friction-induced wear [1]. Aim of the study was to measure the friction-induced temperature increase in vivo in THR and to identify possible individual parameters of influence. Methods. For the in vivo measurement, an instrumented implant with an Al. 2. O. 3. /XPE-pairing and an integrated temperature sensor was used [Fig. 1] [2]. Ten patients were provided with such an instrumented implant. Up to now, long time measurements were performed on six of these patients (Ø63y, Ø89kg). During these measurements, the subjects walked Ø60min on a treadmill with 4km/h. The investigation was performed Ø61 (43–70) months post operatively. Short time (Ø3min) in vivo load measurements during walking on treadmill were already available from the other four patients. These data were used to calculate the peak temperatures after 60mins of walking by using a model, based on the long time measurements. Results. The peak values of the friction-induced temperature increase were achieved in vivo after 30min (H7R) to 70min (H2R), with peak temperatures between 1.5°C (H6R) to 4.8°C (H7R) [Fig. 2]. These maximum values were similar to those already observed in other patients [3]. The in vivo measured peak values of the friction-induced temperature increase after long time walking on a treadmill with respect to the implant orientation are shown in Fig. 3 as points and the calculated peak values as circles. First analyses have shown that the individual implant orientations seem to have an influence [Fig. 3] on the friction-induced increase of the joint temperature during walking, but also the patient's age. Discussion. The gliding partners and joint lubrication directly influence friction in artificial hip joint replacements and thus the friction- induced temperature increase. Analyses of the in vivo acting joint friction during walking have shown that there is an increase in friction over the course of each gait cycle after contralateral toe off [4]. This can be explained by a decrease in the lubricating film thickness due to the pressing out of the synovia from the joint space. During load reduction of the joint in the swing phase, the fluids are transported back into the joint space. Thus, the level of joint friction at the beginning of the next gait cycle depends on the return transport of the synovia. The influence of the sum anteversion angle (ΣAV) on friction-induced temperature increase (Fig. 3) can therefore be explained mechanically: The ΣAV determines the functional joint roofing and the position of the load-transferring zone into the joint socket. The larger the ΣAV, the more it shifts towards the edge of the socket, and the shorter the path for the return transport of the synovium

Introduction. Infections affect 1–3% of Total Knee Arthroplasty (TKA) patients with severe ramifications to mobility. Unfortunately, reinfection rates are high (∼15%) suggesting improved diagnostics are required. A common strategy to treat TKA infection in North America is the two-stage revision procedure involving the installation of a temporary spacer in the joint while the infection is treated for 6–12 weeks before permanent revision. Subdermal temperature increases during infection by 1–4°C providing a potential indicator for when the infection has been cleared. We propose an implantable temperature sensor integrated into a tibial spacer for telemetric use. We hypothesized that suitable sensing performance for infection monitoring regarding precision and relative accuracy can be attained using a low power, compact, analog sensor with <0.1ºC resolution. Materials & Methods. An experimental sensor was selected for our implanted application due to its extremely low (9 μA) current draw and compact chip package. Based upon dynamic range it was determined that the analog/digital converter must be a minimum of 11 bits to deliver suitable (<0.1ºC) resolution. A 12-bit ADC equipped microcontroller was selected. The MCP9808 (Microchip Technology, Chandler, AZ, USA) delivers manufacturer characterized thermal data in decimal strings through serial communication to the same microcontroller. The rated accuracy of the MCP9808 sensors in the required temperature range is max/typ +/− 0.5/0.25ºC with a precision of +/− 0.05ºC delivered at a resolution of 0.0625ºC. Within a thermally insulated chamber with a resistive heating element, the following experiment was conducted: Using empirical plant modelling tools, simulation and implementation an effective PI control scheme was implemented to create a highly precise temperature chamber. With MCP9808 as reference, the temperature in the thermal chamber was driven to 20 different temperatures between 35 and 40ºC for 10 minutes each and sampled at 5 Hz. This trial was repeated three times over three days. Transient data was discarded so as only to evaluate the steady state characteristics, wavelet denoising was applied, and a regression between the reference MCP9808 temperature response vs the experimental sensor intended for implantation was tabulated in Matlab. Results. Compared to reference values, the experimental temperature sensor displayed relative accuracy of +/− 0.275ºC (with 95% confidence) and precision of +/−0.135ºC over a 35–40ºC range as determined over 190,212 relevant samples. Note that in practice, the precision is independent of reference, but the absolute accuracy is relative to the gold standard's accuracy. Conclusion. Infection frequently results in permanent mobility issues in the context of total knee arthroplasty. This has led to an ongoing call for better treatments. Analysis suggests that the proposed experimental sensor offers high precision and reasonable relative accuracy in temperature sensing, substantially tighter than the expected stimulus from infection, while also offering desirable characteristics for implantation. This sensing platform will be integrated into an instrumented tibial spacer in future work. For any figures or tables, please contact authors directly

INTRODUCTION. Experience with Metal on Metal (MoM) hip resurfacing devices has shown adequate cementation of the femoral head is critical for implant survival. Bone necrosis can be caused by the temperature change in the peri-prosthetic bone whilst the cement cures during implantation. This can lead to implant loosening, head/neck fracture and implant failure. During the implantation it is known that implants change shape potentially altering joint clearance and causing loosening. Given the history of Metal on Metal implant failure due adverse tissue reactions from Cobalt and Chromium particles we sought to test a novel Ceramic on Ceramic (CoC) bearing which may mitigate such problems. AIM. We set out to compare the behaviour of a novel ceramic femoral head component to a standard metal component in a hip resurfacing system after cemented implantation in a physiological warmed cadaveric model. Our first aim was to perform heat transfer analysis: To document time to, and extent of, maximum temperature change on the metal/ceramic surface and inside the resurfaced femoral head bone. Our second aim was to perform a dimensional analysis: To document any resulting deformation in the metal/ceramic femoral head bearing diameter during cementation. METHODS. Femurs were removed from four fresh frozen cadavers and placed into a vice. One surgeon with extensive experience in hip resurfacing surgery (JH) prepared all the femoral heads for implantation. Cadaveric warming was performed using a thermostatic silicone heating element to achieve near physiological conditions (28–32°C). The femur components were then implanted onto the femur head using Simplex P (Stryker) low viscosity bone cement. We used four ceramic (ReCerf™) and four metal implants (ADEPT®) of equal and varying size. (2 × (42mm, 46mm, 48mm, 50mm). Temperature change was measured using a thermometer probe placed into femur neck and head from the lateral side with position check using an image intensifier. Implant surface temperature was measured using a calibrated infrared thermometer at a standard 30cm distance. Head bearing surface diameter was measured using a micro-meter. Measurements were taken 2mins pre-implantation and sequentially at 1, 5, 10, 15, 20, 25 and 30 minutes after implantation. RESULTS. The bone temperature change for both metal and ceramic implants fell after implantation and then increased. The implant surface temperature increased and then stabilised for both implants. There was no significant difference in the bone or surface temperature change between metal and ceramic implants. The bearing surface diameter change was greater in the metal implants, although this was not significant. All implants returned to within one µm of initial surface diameter at 30 minutes. CONCLUSIONS. The femoral head component of a ceramic resurfacing has similar properties for surface temperature change following implantation to conventional MOM resurfacing. The periprosthetic bone is not at risk of significant heat necrosis during cementation (max temp 32°C). The deformation following implantation was similar for both metal and ceramic components. All implants returned to near initial diameter. The deformation and temperature changes following implantation of a ceramic resurfacing are similar to a metal implant

Introduction. Dl-α-Tocopherol (VE)-blended non-crosslinked UHMWPE has been developed as a bearing surface material for knee prostheses due to the radical scavenging capabilities of vitamin E and has demonstrated a low wear rate in knee simulator testing [1,2]. In previous our study, VE-blended, crosslinked UHMWPE has demonstrated a low wear rate in hip simulator testing [3, 4]. As the radical scavenging capabilities also reduce the crosslinking degree of the material, multiple dose crosslinking has been investigated. However, these crosslinked UHMWPE materials may have different mechanical properties, as each crosslinking process, especially the annealing condition, is different. Additionally, there is little information about VE-blended, crosslinked UHMWPE with different annealing conditions. In this study, the effect of annealing temperature was investigated with regard to tensile strength, crosslink density, and crystallinity of VE blended, crosslinked UHMWPE. Method. VE blended samples were manufactured via direct compression molding following the blending of UHMWPE resin powder (GUR1050, Ticona Inc.) with VE (dl-α-tocopherol, Eisai Co. Ltd.) at 0.3wt%. The virgin samples were derived similarly, but without the addition of VE. Both materials underwent crosslinking by irradiation via a 10MeV electron beam at 300kGy and were then heat treated at several temperatures (25, 80, 110, 130 and 150 °C) for 24 hours. Gel content, which can be interpreted as cross-link density, was determined by measuring the weight of the samples before and after soaking in decahydronaphthalene at 150 °C for twelve days. Tensile tests were carried out following JIS K 7113, with the cross head speed set at 50 mm/min. Crystallinity was determined by using DSC and integrating over the enthalpy curve from 80 to 150 °C and normalizing with the enthalpy of melting for 100% crystalline polyethylene. Result. Fig. 1 shows the gel content of UHMWPE samples after crosslinking. Raising the annealing temperature caused an increase in the gel content regardless the VE content. Additionally, among samples with the same annealing temperature, VE samples had the lower gel content. Fig. 2 shows the yield strength of UHMWPE samples. Higher annealing temperature decreased the yield strength, and increased elongation. Fig. 3 shows the crystallinity of each UHMWPE sample. Higher annealing temperature decreased the crystallinity of UHMWPE. Discussion. In this study, the effect of annealing temperature on the mechanical properties of crosslinked UHMWPE was investigated. The results indicated that a greater volume of crystalline UHMWPE melted and reformed at the higher annealing temperatures. This was thought to occur due to the fact that UHMWPE consists of a range of different molecular weight chains, allowing for melting below 135°C. Therefore, the crystallinity and crosslink density changed for each annealing temperature. The annealing is a simple but effective method for designing the crystallinity and crosslinking of UHMWPE

Knee warmth is a common clinical observation following total knee arthroplasty (TKA). This can cause concern that infection is present. The purpose of our study was to establish the pattern of knee skin temperature following uncomplicated TKA. It was a prospective study carried out between 2001 and 2004. A pocket digital surface thermometer was used. A preliminary study established that the best site to measure knee skin temperature was superomedial to the patella and the best time was 12 noon. Patients with an increased risk of infection and those with a contralateral knee pathology or a previous surgery were excluded. Forty-eight patients fulfilled the inclusion criteria and consented to participate; the skin temperature of operated and contralateral knees was measured pre-operatively and daily during the first six weeks post-operatively. Measurements were also taken at 3, 6, 12 and 24 months following surgery. During the course of the study, patients developing complications of the operated knee or any pathology of the contralateral knee were excluded. Thirty-two patients completed the main study. Following surgery, systemic and both knees temperatures increased. Whereas systemic and contralateral knee temperatures settled within one week, the operated knee temperature took a longer time. The difference in temperature between the two knees had a mean value of +2.9°C at 7 days. This mean value decreased to +1.6°C at 6 weeks, +1.3°C at 3 months, +0.9°C at 6 months +0.3°C at 12 months and +0.04°C at 24 months. Following uncomplicated TKA, the operated knee skin temperature increases compared to the contralateral knee. This increase peaks at day 3 and diminishes slowly over several months; however, it remains statistically significant up to 6 months. These results correlate with the findings of previous studies that showed a prolonged elevation of inflammatory markers

Introduction. UHMWPE articulating against PEEK-OPTIMA® has the potential for use as a novel bearing couple in joint arthroplasty due to its potentially low wear rates and the bioinertness of its wear debris. The aim of this study was to investigate the role of protein in the lubricant on the wear of UHMWPE articulating against PEEK at both room and physiological temperature. Methods. The wear of GUR1020 UHMWPE pins articulating against PEEK plates (R. a. ∼0.06µm) was compared to highly polished cobalt chrome plates (R. a. <0.01µm) in a 6-station multi-axial pin-on-plate rig using kinematics to replicate those in total knee arthroplasty. Tests were carried out at either ∼20°C or ∼36°C and wear was investigated under varying concentrations of bovine serum (0, 25 or 90%). Studies were carried out for 1 Million cycles with wear of the UHMWPE pins assessed gravimetrically using unloaded soak controls to compensate for moisture uptake. Statistical analysis was carried out using ANOVA with significance taken at p<0.05. Results. Figure 1 shows wear factors for the UHMWPE pins. In 0% serum, the wear of UHMWPE against both PEEK and cobalt chrome tested at room and physiological temperatures was very low. When lubricated with 25% serum and tested at room temperature as per standard practice at Leeds, the wear of UHMWPE against cobalt chrome was comparable to previously published data (2.13×10. −7. mm. 3. /Nm) and the wear of UHMWPE articulating against PEEK was 3.53×10. −7. mm. 3. /Nm. At physiological temperatures, the wear of UHMWPE against cobalt chrome was similar to tests at room temperature but against PEEK, there was a significant (p=0.017) decrease in wear factor [1]. The wear of UHMWPE against cobalt chrome was significantly (p=0.003) higher when tested in 90% serum compared to 25% serum at room temperature but this effect was not seen in UHMWPE articulating against PEEK (p=0.38). Testing at elevated temperature in 90% serum significantly (p=0.007) decreased the wear of UHMWPE against cobalt chrome and a deposition, likely to be protein, was evident on the surface of the plates. However, against PEEK, there was no significant difference in wear under the different temperature conditions. Discussion. In pin-on-plate tests of UHMWPE against smooth metal counterfaces, the low wear rate and polymer deposition in tests lubricated with water has previously been observed. A similarly low wear rate has now been observed for UHMWPE against PEEK. Water does not produce adequate boundary lubrication. At 25% and 90% serum and varying temperatures the wear behaviour of UHMWPE against PEEK is not the same as UHMWPE against cobalt chrome. There may be a number of factors contributing to these differences, including surface topography, protein precipitation, protein deposition, differing wear mechanisms and lubrication regimes. For example, UHMWPE-PEEK is a higher friction bearing couple than UHMWPE-CoCr and when tested at elevated temperatures, frictional heating at the bearing surfaces may accelerate protein precipitation and adsorption of protein onto the articulating surfaces which may affect wear. This study shows that testing under different lubricant and environmental conditions can have a significant effect on wear

Introduction. Hypothermia is the drop in body temperature under 35°C (95°F), It has implications in immunological function and healing process, increasing the infection and the cardiovascular risk. During hip arthroscopy patients are exposed to several risk factors that may lead to hypothermia. Objective. to determinate if there are hypothermia and which are the factors contributing to hypothermia during hip arthroscopy. Methods and materials. we developed an prospective observational analytical study in a cohort group of patients that went to a hip arthroscopy, all operated by a single surgeon for treatment of femoroacetabular impingement, all were done under general anesthesia in supine position, with vair hugher warmer body air convection system always in 43.3°C; and we registered central body temperature (esophagical) during the entire procedure, we also recorded operation room temperature, volume (liters) and temperature of the saline solution used for the arthroscopy, age of the patient, body mass index (BMI), arterial tension, pump pressure, and surgical time. We analyzed the results with STATA 10.0 statistical software. Results. we performed 12 cases, 30 years old in average (14 – 46), BMI 24.0 in average (18.7 – 30.4), and hypothermia was founded in 16% (2/12) of cases. There are a direct assosiation between hypothermia and operating time over 120 minutes (p <0,001) (fig.1). Despite the rest of the parameters we didn't find any other correlation. Conclusion. Hypothermia is present in 16,67% of the patients, during hip arthroscopy for the treatmemt of femoroacetabular impingement, are group is small but we demonstrated a direct correlation between operating time and hypothermia, further studys with larger groups should be performer to identify the correlations and risk factors for hypothermia in these patients

Introduction & aims. Osteonecrosis may be triggered by bone temperature above 45°C during routine orthopaedic bone cuts using power-driven saws, with potentially negative impacts on bone healing. A new oscillating-tip saw blade design (Precision; Stryker, Kalamazoo, Mich) has been recently developed but the saw blade design may influence the amount of heat generated. We have therefore sought to compare the bone temperature during a standardised cutting task with two different saw blade designs. Method. Three pairs of human cadaveric femora were obtained. Each femur was clamped and a distal femoral cutting jig was applied. An initial cut was performed to visualise the distal metaphyseal bone. The cutting block was then moved 2 mm proximal and a further cut performed, measuring the temperature of the bone with an infra-red camera. This was repeated, moving the block 2 mm proximal with each cut, alternating between a standard oscillating saw blade and the “Precision” saw blade. The density of the cut bone was then established from a CT scan of each specimen performed prior to the experiment. Results. The 2 blades did not differ with respect to the integrated mean temperature calculated for each cut. (p = 0.89) The average peak temperatures were not significantly different between blades (p = 0.14). There was no significant difference between blades for peak heating rate (p = 0.7) but the blades differed with respect to the proportion of pixels heated above the 45 deg osteonecrotic threshold, with a significant difference in the integrated curve between blades (p = 0.046) in favour of the standard saw blade. Conclusions. The “Precision” blade may have advantages over standard oscillating blade but reduced heat generation was not found in our study. On the contrary, the “precision” blade potentially reaches the bony osteonecrosis threshold more often, questioning its use for osteotomy or uncemented knee arthroplasty. Further work should examine modifications to the blade design to better optimise the requirements of speed, accuracy and heat generation

Introduction. Implant-cement debonding at the knee has been reported previously [1]. The strength of the mechanical interlock of bone cement on to an implant surface can be associated with both bone cement and implant related factors. In addition to implant surface profile, sub-optimal mixing temperatures and waiting times prior to cement application may weaken the strength of the interlock. Aims. The study aimed to investigate the influence of bone cement related factors such as mixing temperature, viscosity, and the mixing and waiting times prior to application, in combination with implant surface roughness, on the tensile strength at the interface. Materials and Methods. Tensile tests were carried out on two types of hand-mixed cement, high (HV) and medium viscosity (MV), sandwiched between two cylindrical Cobalt-Chrome coupons with either smooth (60 grit) or rough (20 grit) surface finishes. 144 Specimens were prepared with a cement thickness layer of 2.5 mm in customised rigs (Figure 1). The samples were grouped and tested at two mixing temperatures (23 and 19 degrees), at different mixing times (HV-30s, MV-45s). Waiting times after mixing were varied between early (1.5 min), optimal (4.5 min) or late (8 min); for HV and 4 min, 7.5 min and 11 min for MV cements. All the samples were cured for 24 hours prior to testing. The peak force and stress was calculated for all specimens. Results and Conclusion. Surface Finish: Rough surfaced samples had significantly higher (p < 0.05) mean tensile forces and stress than smooth samples at both 19 and 23 degrees across HV and MV cement types. Cement Type: MV cements, when applied to rough samples with waiting times of 4 minutes at 23 degrees, and 11 minutes at 19 degrees, resulted in the highest peak tensile forces, followed by 7.5 minutes at 23 and 19 degrees respectively (Figure 2). Temperature at different application times for rough and smooth samples: for MV cement, rough samples prepared at 23 degrees, 4 minutes, and smooth samples at 19 degrees, 7.5 minutes were found to be significantly better (p < 0.05) than their counterparts. For HV cement, 23 degrees was found to be better (p < 0.05) for smooth samples at applications times of 4.5 and 8 minutes and 19 degrees for application times of 1.5 minutes. No significant difference was noted for rough samples for the same. Application times at different temperatures for rough and smooth samples: at both 19 and 23 degrees, there were no differences between application times within the rough sample groups for HV or MV. However, for smooth samples, HV cement, tensile forces were significantly higher (p < 0.05) at 23 degrees in the following order; 8 minutes > 4.5 minutes > 1.5. The results show that implant surface roughness and cement mixing time, temperature, viscosity and application times affect the strength of the interlock at the interface

Aim

Thermal stability is a key property determining the suitability of an antibiotic agent for local application. Long-term data describing thermal stability without interference from carrier materials are scarce.

Multiple studies have established an inverse relationship between ambient theatre temperatures and polymethyl methacrylate (PMMA) cement setting times. It is also known that allowing cement to equilibrate to ambient theatre temperatures restores expected setting characteristics. One overlooked entity is the transport and storage conditions of cement. This is important in tropical regions, where extreme temperature and humidity may cause rapid cement setting times, resulting in potentially significant intra-operative complications. This study investigated the relationship between extreme transport and storage conditions of Antibiotic Simplex cement (Stryker), and the effect on setting times at Cairns Hospital, Far North Queensland, Australia. Fifty units of cement were divided evenly into a control arm and four experimental arms. The experimental arms were designed to mimic potential transport and storage conditions. They included seven days of storage in a medication fridge, on the hospital loading dock, in a cane shed, and in a Toyota Landcruiser parked outdoors during January 2022. Humidity and temperature readings were recorded. The samples in each group were evenly distributed to equilibrate to theatre conditions for 1 hour and 24 hours. Setting time was recorded when a no. 15 scalpel blade was unable to mark the surface. All three ‘hot’ exposures setting times were significantly faster for both 1 hour (ρ=0.001) and 24 hours (ρ=0.024) equilibration times. The difference in setting times for the ‘cold’ exposure was not significant for either equilibration times (ρ=1). To our knowledge, this is the first study investigating cement setting times in tropical climates. Further studies are required to address the effect of these conditions on biomechanical strength of PMMA cement. We conclude that extreme heat and humidity during transport and storage have a statistically significant effect on cement setting times

Arthroscopic electrosurgical tools for ablative, desiccating or coagulative effect are delivered as monopolar or bipolar probes. Monopolar electrosurgery delivers various profiles of heat energy directly to the tissue within a non-conductive irrigant (such as water or glycine) whereas bipolar electrosurgery creates an energy source by producing an electrical arc between the bipolar electrodes on the instrument head within an electro-conductive irrigation solution (saline) - and the heat generated is then transferred to the target tissues. This study investigated the heat generation within the simulated in-vitro test model to review the level of local heat production and potential local tissue heat. In a simulated In-vitro testing environment the local heat generation using bipolar or monopolar electrosurgical probes at standard power setting in either saline or water was tested, both touching and not touching a simulated tissue target, and for variable on-times. Monopolar generated relatively little heat when used in water and not touching the tissue. By contrast the bipolar wand generated potentially damaging local tissue temperature rises when used in saline and not touching the tissue. Both probes generated high local tissue heat when touching the tissue in their recommended irrigation solution. Monopolar electrosurgery delivered high localized temperature to the simulated tissue surface, but produced relatively little heat when not touching the tissue in a water solution. Bipolar however created high local temperature within the fluid adjacent to the probe irrespective if it was touching the tissue or not. Activation of the bipolar probe away from the tissue in saline irrigation may create a potential harmful temperature within the fluid medium without delivering therapeutic thermal effect to the target tissues. Monopolar electrosurgery appears to deliver a more controlled thermal effect, and only when in contact with the target tissues – potentially creating a reduced collateral thermal footprint

Aims. The microbiological detection of microorganisms plays a crucial role in the diagnosis as well as in the targeted systemic and local antibiotic therapy of periprosthetic infections (PJI). Despite extensive efforts to improve the sensitivity of current culture methods, the rate of culture-negative infections is approximately 10–20% of all PJI. This study investigates an preanalytical algorithm (culture collection and direct processing in the OR) to potentially increasing culture yield in patients with PJI. Methods. Patients undergoing staged revision arthroplasty for PJI in our hospital between October 2021 and 2022 were included in this prospective pilot study. Intraoperatively twenty tissue samples were collected and distributed among 4 groups. Tissue samples were prepared according to standard without medium and in thioglycolate medium at 3 different temperatures (room temperature, 4°C, 37° for 24h before transport to microbiology) directly in the OR. The removed implants were sonicated. Cultures were investigated on days 1, 3, 7, 12, 14 for possible growth. All grown organism, the number of positive samples and the time to positivity were recorded and compared. Results. 71 patients were included (age, gender). Compared to the standard procedure the thioglycolate broth at 37°C was significantly more often culture-negative (p=0.031). No significant differences in the frequency of culture-negative samples were detected in the other groups. 8.4% (6/71) patients were culture negative in the standard culture but positive in the thioglycolate samples. In contrast, 7% (5/71) were culture negative in the thioglycolate samples but had bacterial detection in the standard approach. In 4.7% (3/63) of the patients, only the sonication showed growth, whereas 25.4% (16/63) had no growth in sonication fluid but in one of the cultures. For S. caprae, there was a significantly different distribution (p=0.026) with more frequent detection in the group with thioglycolate at 37°C. The standard procedure (p=0.005) and sonication (p=0.023) showed a shorter time to positivity of the culture compared to the thioglycolate approach at 4°C. Conclusions. No general differences could be shown between the standard preparation and the thioglycolate preparation; in particular, storage at different temperatures does not seem to result in any difference. For individual cases (8% in this study), bacterial growth was detected in the thioglycolate group that would have been culture-negative otherwise. There might be organism dependent differences in growth in different media

Introduction. Osteotomy is a key step in distraction osteogenesis. Various techniques of osteotomy have been described with its own benefits and pitfalls. Percutaneous osteotomy using multiple drill holes is one of the most widely used osteotomy techniques. It still remains a challenge however to keep the drill holes aligned prior to the osteotomy. Moreover, the efficacy of percutaneous irrigation practice to keep the temperature low during drilling with this technique is also debatable. With an aim to overcome these challenges, we are introducing a device called the Double Barrel Drill Sleeve (DBDS) to perform percutaneous osteotomies. We attempted to compare this method to the conventional multiple drill holes technique using laboratory experiments and clinical data. Materials & Methods. DBDS has two adjacent parallel barrels that can fit 3.2 to 3.5 mm diameter drill bits. It has a guide member at the drilling end that can be inserted through a pre drilled hole at the near and far cortices of a bone. This provides a constant rotating point for drilling of holes through the barrels. An osteotomy simulation was performed to compare percutaneous drilling with DBDS vis-a-vis a conventional single drill sleeve (SDS) by qualified orthopaedic surgeons, mainly to assess the drilling patterns of both techniques. Percutaneous drilling was done on PVC pipes wrapped in thick sponge to simulate tubular bone with surrounding soft tissue. We also assessed the effect of indirect irrigation on temperature during drilling using the DBDS against a control group on a cadaveric bone model. Ultimately we reviewed our patients who had undergone osteotomy for distraction osteogenesis with DBDS and the conventional technique, and compared their outcomes. Results. Completion time for the osteotomy simulation in the DBDS group was significantly faster than the conventional drilling group; 74 seconds to 179 seconds. There was significantly less drilling deviation from the midpoint in the DBDS group as compared to the SDS group. Mean bone temperature during drilling with indirect irrigation using DBDS was significantly lower (32.6'C) compared to the control group (48.4'C). There was no significant difference in healing index between patients treated with DBDS and the conventional method. None of these patients developed non union. Conclusions. Percutaneous drilling with DBDS was quicker and more linear compared to the conventional method. Its double-barreled feature allows effective indirect irrigation during drilling. A comparable healing index in both of the techniques shows its clinical efficacy. These attributes make DBDS a usefull tool to overcome some of the pitfalls associated with the conventional multiple drill holes technique

Introduction & Aims. In other medical fields, smart implantable devices are enabling decentralised monitoring of patients and early detection of disease. Despite research-focused smart orthopaedic implants dating back to the 1980s, such implants have not been adopted into regular clinical practice. The hardware footprint and commercial cost of components for sensing, powering, processing, and communicating are too large for mass-market use. However, a low-cost, minimal-modification solution that could detect loosening and infection would have considerable benefits for both patients and healthcare providers. This proof-of-concept study aimed to determine if loosening/infection data could be monitored with only two components inside an implant: a single-element sensor and simple communication element. Methods. The sensor and coil were embedded onto a representative cemented total knee replacement. The implant was then cemented onto synthetic bone using polymethylmethacrylate (PMMA). Wireless measurements for loosening and infection were then made across different thicknesses of porcine tissue to characterise the sensor's accuracy for a range of implantation depths. Loosening was simulated by taking measurements before and after compromising the implant-cement interface, with fluid influx simulated with phosphate-buffered saline solution. Elevated temperature was used as a proxy for infection, with the sensor calibrated wirelessly through 5 mm of porcine tissue across a temperature range of 26–40°C. Results. Measurements for loosening and infection could be acquired simultaneously with a duration of 4 s per measurement. For loosening, the debonded implant-cement interface was detectable up to 10 mm with 95% confidence. For temperature, the sensor was calibrated with a root mean square error of 0.19°C at 5 mm implantation depth and prediction intervals of ±0.38°C for new measurements with 95% confidence. Conclusions. This study has demonstrated that with only two onboard electrical components, it is possible to wirelessly measure cement debonding and elevated temperature on a smart implant. With further development, this minimal hardware/cost approach could enable mass-market smart arthroplasty implants

Shoulder septic arthritis is uncommon and frequently misdiagnosed, resulting in severe consequences. This study evaluated the demographics, bacteriological profile, antibiotic susceptibility, treatment regimens, and clinical outcomes. This is a 10-year retrospective observational analysis of 30 patients (20 males and 10 females) who were treated for septic arthritis of the shoulder. The data collecting process utilised clinical records, laboratory archives, and x-ray archives. We gathered demographic information, pre- and post-intervention clinical data, serum biochemical markers, and the results of imaging examinations. All patients had a surgical arthrotomy and joint debridement in the operating room, and specimens were taken for culture and sensitivity testing. The specimens were cultivated for at least seventy-two hours. Shoulder joint ranges of motion, comorbidities, and the presence of osteomyelitis were assessed clinically to determine the outcome. All statistical analyses were conducted using the STATA 17 statistical software. Analysis of correlation between categorical variables was performed using the chi-squared test. The majority of the study patients were black Africans (97%). The age range of the group was from 8 days to 17 years. At presentation, 33% of patients had a low-grade fever, whereas the majority (60%) had normal body temperature. The average length of symptoms was 3.9 days (ranged from 1 day to 15 days), and the majority of patients had an increased white cell count (83%) and C-reactive protein (98%). There was accumulation of fluid in the joint of all individuals who received shoulder ultrasound imaging. We noted a significant incidence of gram-positive cocci, which were mostly susceptible to first-line antibiotics. Shoulder stiffness affected 63% of patients and chronic osteomyelitis affected 50% of individuals. Neither the severity nor the duration of the symptoms was related to an increased risk of osteomyelitis. The results of this study revealed that the clinical characteristics and bacterial profile of septic arthritis of the shoulder conform to typical patterns. The likelihood of osteomyelitis and an unfavourable prognosis is considerable

Introduction. Compartment syndrome can be a life changing consequence of injury to a limb. If not diagnosed and treated early it can lead to permanent disability. Neurovascular observations done on the ward by nursing staff, are often our early warning system to those developing compartment syndrome. But are these adequate for detecting the early signs of compartment syndrome? Our aim was to compare the quality and variability of charts across the UK major trauma network. Materials & Methods. All major trauma centres in England and Scotland were invited to supply a copy of the neurovascular chart routinely used. We assessed how such charts record relevant information. Specific primary data points included were pain scores, analgesia requirements, pain on passive stretch and decreased sensation in the first web space specifically. As secondary objectives, we assessed how late signs were recorded, whether clear instructions were included, quantitative scores and the use of regional blocks recorded. Results. A response rate of 46% was achieved. Of the charts reviewed, 25% documented pain scores or pain on passive movement. Pain on movement and analgesia requirements were documented in 33% and 8% respectively. Specific sensation within the 1. st. webspace was recorded in 16%. No charts recorded use of regional block. All charts recorded global sensation, movement (unspecified), pulse and colour whilst 66% documented capillary refill and 83% temperature. Instructions were included in 41% of charts. Conclusions. In 2016, the BOA supported publication of an observation chart for this purpose however, it is not widely used. In our study, late signs of compartment syndrome were generally well recorded. However, documentation of early signs and regional blocks was poor. This may lead to delays in diagnosis with significant clinical and medicolegal consequences. Standardisation of documentation by updating and promoting the use of the pre-existing chart would ensure highest quality care across the network

Introduction. Continuous compression implants (CCIs) are small memory alloy bone staples that can provide continuous compression across a fracture site, which change shape due to temperature changes. Reviews of CCIs in orthopaedics have documented their use in mainly foot and ankle surgery, with very limited descriptions in trauma. They could be beneficial in the management of complex or open injuries due to their low profile and quick insertion time. The aim of this case series were to clarify the use of CCIs in modern day limb reconstruction practice. Materials & Methods. This was a single centred study looking retrospectively at prospective data for patients who were treated for an acute fracture or non-union with a CCI between September 2019 and May 2023. Primary outcome was to determine the function and indication of the CCI as judged retrospectively and secondary outcomes investigated unplanned returns to theatre for infection or CCI failure. Results. Sixty patients were eligible with a mean age of 44.2 (range 8–89). Fifty-one patients were treated for acute fractures, nine for non-unions; and almost half (27 patients) had open injuries. There were seven different sites for treatment with a CCI, the most common being tibia (25 patients) and humerus (14 patients). Of the 122 CCIs used, 80 were used as adjuncts for fixation in 48 patients. Their indication as an adjunct fell into three distrinct categories – reduction of fracture (39 CCIs), fixation of key fragments (38 CCIs) and compression (3 CCIs). Of these 48 patients, 4 patients had a frame fixation, 19 had a nail fixation, 24 patients had a plate fixation. Forty-two CCIs were used in isolation as definitive fixation, all were for midfoot dislocations expect an open iliac wing fixation from a machete attack and an isolated paediatric medial malleolus fixation. Two patients returned to theatre for infection and two due to CCI failure. Conclusions. This series has demonstrated the versality of CCIs across multiple sites of the body and for a large variety of injuries. It has identified, when not used in isolation, three main indications to support traditional orthopaedic fixations. Given the unpredictability in limb reconstruction surgery, the diversity and potential of CCIs could form part of the staple diet in the modern-day practice

Tissue engineering by self-assembly is a technique that consists of growing cells on surfaces made of thermoresponsive polymers, that allow the production of contiguous cell sheets by simply lowering the temperature below the polymer's low critical solution temperature. In this approach cell-cell junctions and deposited extracellular matrix (ECM) remain intact, which provides a better cell localisation at the site of injury. However, these systems lack the possibility to fabricate multi-layered and three-dimensional cell sheets that would better recapitulate native tissues. Moreover, the fabrication of ECM-rich cell sheets would be highly desirable. This limitation could be overcome by inducing macromolecular crowding (MMC) conditions. Herein we venture to fabricate electrospun thermoresponsive nanofibres to sustain the growth and detachment of ECM-rich tissue substitutes in the presence of a MMC microenvironment. A copolymer of 85% poly-N-isopropylacrylamide and 15% N-tert-butylacrylamide (pNIPAAm/NTBA) were used for all experiments. To create aligned nanofibers, the polymer was electrospun and collected on a mandrel rotating at 2000 rpm. Human adipose derived stem cells (hADSC) were treated with media containing macromolecular crowders to enhance matrix deposition. Cell viability and morphology were assessed, and immunocytochemistry was conducted in order to estimate matrix deposition and composition. Adipogenic, osteogenic and chondrogenic assays were performed both with and without the presence of MMC. Non-invasive cell detachment was enabled by decreasing the temperature of culture to 10 °C for 20 minutes. The electrospinning process resulted in the production of pNIPAm/NTBA fibres in the diameter range from 1 to 2 µm and an overall alignment of 80%. Cell viability, proliferation and metabolic activity revealed that hADSCs were able to grow on the thermoresponsive scaffold. The cells were able to detach as an intact cell sheet in presence of MMC. Moreover, it was demonstated that MMC, by a volume extrusion effect, enhances Collagen type I deposition, which is one of the main components of the ECM. Histological analysis revealed that in the presence of MMC the cells were able to self-assembled into three dimensional multi-layers. The cells were able to differentiate towards the osteogenic and adipogenic lineage in the presence of MMC. Interestingly we were able to fabricate three-dimensional chondrogenic cell sheet both with and without MMC. Collectively the pNIPAm/NTBA thermoresponsive fibres were able to sustain the growth and the detachment of ECM-rich multi-layered cell sheets. The pNIPAm/NTBA fibres were able to successfully sustain growth and detachment of ECM-rich tissue equivalents. We believe that replacement, repair and restoration of tissue function can be accomplished best using cells that create their own tissue-specific extracellular matrix with a precision and stoichiometric efficiency still unmatched by man-made devices