Objectives. Temperature is known to influence muscle physiology, with the velocity of shortening, relaxation and propagation all increasing with temperature. Scant data are available, however, regarding thermal influences on energy required to induce muscle damage. Methods. Gastrocnemius and soleus muscles were harvested from 36 male rat limbs and exposed to increasing impact energy in a mechanical test rig. Muscle temperature was varied in 5°C increments, from 17°C to 42°C (to encompass the in vivo range). The energy causing non-recoverable deformation was recorded for each temperature. A measure of tissue elasticity was determined via accelerometer data, smoothed by low-pass fifth order Butterworth filter (10 kHz). Data were analysed using one-way analysis of variance (ANOVA) and significance was accepted at p = 0.05. Results. The energy required to induce muscle failure was significantly lower at muscle temperatures of 17°C to 32°C compared with muscle at core temperature, i.e., 37°C (p < 0.01). During low-energy impacts there were no differences in muscle elasticity between cold and warm muscles (p = 0.18). Differences in elasticity were, however, seen at higher impact energies (p < 0.02). Conclusion. Our findings are of particular clinical relevance, as when muscle temperature drops below 32°C, less energy is required to cause muscle tears. Muscle temperatures of 32°C are reported in ambient conditions, suggesting that it would be beneficial, particularly in colder environments, to ensure that peripheral muscle temperature is raised close to core levels prior to high-velocity exercise. Thus, this work stresses the importance of not only ensuring that the muscle groups are well stretched, but also that all muscle groups are warmed to core temperature in pre-exercise routines. Cite this article: Professor A. H. R. W. Simpson. Increased risk of muscle tears below physiological temperature ranges. Bone Joint Res 2016;5:61–65. doi: 10.1302/2046-3758.52.2000484

Abstract. Introduction. Cryocompression therapy after knee surgery is widely utilised for post-operative rehabilitation. Skin temperature should be reduced to 10–15°C to maximise the therapeutic benefits while avoiding risks of adverse events. Some cryocompression devices offer control over the temperature of the ice-water circulated through a cuff. The degree to which this corresponds to the achieved skin temperature during a treatment is unknown. Methods. 30 healthy participants volunteered for this prospective randomised crossover trial involving the use of a cryocompression device. Each underwent a 30-minute test in all of five conditions: A, B, C, D and Control. Conditions corresponded to device temperature settings of 6, 8, 10, 12°C and no ice-water circulation, respectively. Skin temperature was measured prior to the cuff being applied, then every 5 minutes during a test. Results. Groups A, B, C and D significantly reduced skin temperature relative to the Control condition (p<0.05). Mean baseline skin temperatures did not significantly differ between groups. Mean skin temperatures after 30 minutes were 13.2 ± 1.9°C (Group A), 14.4 ± 1.5°C (Group B), 16.3 ± 1.8°C (Group C), 18.3 ± 1.7°C (Group D), and 30.8 ± 2.3°C (Control). Conclusions. The cryocompression device successfully reduced the skin temperature to within the therapeutic range. However, temperature settings did not correspond to skin temperatures achieved. To optimise the therapeutic benefit of treatment with this device, the 6°C setting is recommended. (Note: these are preliminary results from on an ongoing study, comprising 72% of the final dataset. Full results will be presented at BASK 2022)

Introduction and Objective. Septic arthritis is an acute infective presentation of the joint calling for urgent intervention, thus making the differential diagnosis process difficult. An increase in temperature in the area containing the suspected septic arthritis is one of the clinically important findings. In this study, it was aimed to investigate whether or not the temperature changes obtained through thermal camera can be used as a new additional diagnostic tool in the differential diagnosis of septic arthritis. Materials and Methods. The study was approved by the local ethics committee as a prospective cohort. A total of 49 patients, 15 septic and 34 non-septic ones, both male and female ones from all ages admitted to the emergency room or evaluated with the consultation of another clinics who were also present with a pre-diagnosis of arthritis (septic or non-septic) in the knee (with complaints of redness, swelling, pain, effusion, increased temperature, edema, and inability to walk) were included in the study. The patients with non-joint inflammatory problems and a history of surgery in the same joint were excluded from the study. The temperature increase in the joint area with suspected septic arthritis was observed, and the difference in temperature changes of this suspicious area with the joint area of the contralateral extremity was compared after which the diagnosis of septic arthritis was confirmed by taking culture with routine intra-articular fluid aspiration, which is the gold standard for definitive diagnosis. Results. The mean age of the patients was 39.89 ± 27.65°C. A significant difference was found between the group with and without septit arthritis in terms of ASO, sedimentation, and leukocyte increase in the analysis of joint fluid (p <0.05). When the thermal measurements were compared, the mean temperature was 37.93°C in the septic group, while it was 36.79°C in the non-septic group, which showed a significant difference (p <0.000∗). The mean temperature difference in both joints was 3.40°C in the septic group, while 0.94°C in the non-septic group (p <0.000∗). While the mean temperature was 37.10°C in the group with septit arthritis, it was measured to be 35.89 °C in the group without (p <0.020). A very strong positive correlation was found between the difference between the mean temperatures of both groups and the values of the hottest and coldest temperature points (r = 0.960, r = 0.902). Conclusions. In the diagnosis of septic arthritis, a thermal imager can be used as a non-invasive diagnostic tool. With the help of this device, a quantitative value, in addition to palpation, can be given to the local temperature increase in the joint, which is an important finding in the clinic of septic arthritis. In future studies, specially designed thermal devices developed with special software for septic arthritis can be developed

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

Background: Muscle tears and injuries are a huge problem throughout the world. Ways of reducing these injuries are welcome, with warm-up and stretching of muscles prior to use established methodologies. Forces associated with muscles can be thought of as active (stimulated muscle: actin-myosin) and passive (relaxed muscle: elastic proteins and connective tissue). In muscle tears, the connective tissue component is damaged, but there is very little information in the literature on this component of the muscle. Objective: To examine passive (elastic) components in muscle during impact loading at differing temperatures. In particular to test the hypothesis that the connective tissue component fails at different loads according to the temperature. Methods: Gastrocnemius and Soleus were isolated from 36 male rat limbs, clamped and exposed to increasing impact loads, by dropping a known weight from increasing heights. Muscle was given one minute to recover before an increased force was applied. Temperature was varied from 17 C to 42 C (to encompass the physiological range) in 5 C increments. The height of drop causing non-recoverable deformation, and the maximum deceleration of the weight (measured using an accelerometer attached to a picoscope) at a constant height was recorded for each temperature. Results: The energy to failure, i.e. the point at which non-recoverable deformation occurred was found to increase above 32 C (p < 0.01) and the maximum deceleration at impact found to have a downward trend with increasing temperatures. At 17 C, the energy to failure was 317.7 ± 20 mJ, At 22 C, the energy to failure was 301.8 ± 29 mJ, At 27 C, the energy to failure was 317.7 ± 40 mJ, At 32 C, the energy to failure was 333.5 ± 21.2 mJ, At 37 C, the energy to failure was 460.2 ± 15.8 mJ, At 42 C, the energy to failure was 619.5 ± 21.2 mJ,. Conclusions: Muscle was shown to act in an increasingly elastic nature with temperature. At higher temperatures a larger energy is required to deform the muscle permanently, and the muscle decelerates more slowly, both in keeping with elastic properties. The same energy at a lower temperature causes significant deformation within the muscle. This has numerous clinical implications, as the temperature at which this change occurs is encountered during surgery and also by sportsmen on outdoor pitches. More research is required to look at the passive components within muscles in humans

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: Aseptic loosening is the commonest complication of cemented total hip arthroplasy. Gaseous voids within the cement mantle are thought to act as stress concentrators and points of origin and preferential fracture propagation at the cement stem interface. Assuming a bone tempereature of 37°C, Bishop recommended heating the prosthesis to 44°C, thereby effecting a reduction in cement-prosthesis interface porosity. The aim of this study was to (I) determine the intra-operative temperature of the femoral cancellous bed prior to insertion of prosthesis, (II) to investigate whether the magnitude of the temperature gradient effects interface porosity (III) to develop clinically relevant recommendations. Materials and Methods: (I) The intra-operative determination of femoral cancellous boney bed temperature. Sterile, single use thermocouples (Mon-a-therm) were used to record interface temperature in six patients, after canal preparation and lavage. (II) A simulated femoral model was designed consisting of a waterbath, set at temperature determined by (I) with an inner water-tight chamber formed by 19mm diameter polyethylene tubing. Cement (Palacos) was non-vacuum mixed (to exaggerate porosity) for 1 minute and injected in a retrograde manner into the inner tube at 3 minutes. Femoral stems (Exeter) were pre-heated in a second waterbath to 18, 32,35,37,40,44°C, were thoroughly dried and lowered into the inner tube by a Lloyd universal testing machine via a custom jig. The cement was left to polymerise. The cement mantle was sectioned transversely, then longitudinally to expose the cement-prosthesis interface. This was stained with acrylic dye to facilitate image analysis. Three mantles for each temperature were produced. Results: (I) The mean femoral canal temperature was 32.3°C, (II) the effect of stem temperature on interface porosity is shown in fig1. Conclusions: Bone temperature is 32°C after canal preparation using contemporary cementing techniques. Heating to 35°C reduces interface porosity, heating to 40°C is optimal

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

Purpose: The aim of our study was to establish the pattern of knee skin temperature following uncomplicated TKA. Methods and Materials: It was a prospective study that was carried out between 2001 and 2004. A pocket digital surface thermometer was used. A preliminary study established the site and time of temperature measurement.. 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 preoperatively and daily during the first six weeks postoperatively. 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. Results: Thirty-two patients completed the main study. Following surgery, systemic and both knees temperatures increased. Whereas systemic and contralateral knee temperature 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. o. C at 7 days. This mean value decreased to +1.6. o. C at 6 weeks, +1.3. o. C at 3 months, +0.9. o. C at 6 months +0.3°C at 12 months and +0.04°C at 24 months. Conclusion: Following uncomplicated TKA, the operated knee skin temperature increases compared to the contra-lateral knee. This increase diminishes slowly over several months; however, it remains statistically significant up to 6 months

Thermostability is a key property in determining the suitability of local delivery of antibiotics in the treatment of orthopaedic infections. Herein, we aimed to assess the thermal stability and antibacterial activity of ciprofloxacin, ceftriaxone, gentamycine and vancomycine in high temperature conditions. Using a standardized E-test method, minimally inhibited concentration of each antibiotic substance against Staphylococcus aureus cultures were determined. The solutions of antimicrobial drugs ciprofloxacin 2 mg/ml, ceftriaxone 200 mg/ml, gentamycine 40 mg/ml and vancomycine 200 mg/ml were diluted twofold in deionised water. Acquired solutions were divided into three aliquots. The first aliquot was held at 40°C for 30 min in a waterbath, the second and the third aliquots were exposed to 80 and 100°C for 30 min in hot-air sterilizer, respectively. The treated solutions were tested for residual activity against S. aureus using a standardized disk diffusion method. Mediums with untreated antibiotic solutions and S. aureus were used as control. Plates were incubated at 37°C, at which time zones of inhibition (ZoI) were measured to the nearest whole millimeter for 14 days. The investigation indicated that the temperature elevation impacted considerably on antimicrobial activity and antibiotic stability overall. The in vitro temperature-response curves showed that ZoI diameter decreases logarithmically with elevated temperatures. Gentamicin was the only drug that was found to be affected to some extent. Results from the study provides a valuable dataset for orthopaedic surgeons considering local application of antibiotics and methods of antibiotic impregnation

The purpose of the study was to evaluate if use of the ArthroCare Radiofrequency Ablation Wand caused excess heating and collateral damage to the surrounding tissues during Arthroscopic Subacromial Decompression. Cadaveric studies have shown worryingly high temperatures are reached when using Radiofrequency Ablation Wands in arthroscopic shoulder surgery. We are unaware of any published literature which assesses these temperature rises in the clinical setting. 10 patients were recruited to participate in the study. A standard Arthroscopic Subacromial Decompression was performed using continuous flow irrigation with intermittent use of the Radiofrequency Ablation Wand for soft tissue debridement. The temperature of the irrigation fluid in the subacromial bursa and the outflow fluid from the suction port of the wand were measured continuously during the procedure using fibre-optic thermometers. Temperatures above 45oC in the subacromial bursa were deemed to be unsafe. The mean peak temperature recorded in the subacromial bursa was 28.6oC (23.49 – 31.94oC) with a mean rise from baseline of 6.1oC. The mean peak temperature recorded from the outflow fluid from the wand was 73.1oC (69.09 – 76.1oC) with a mean rise from baseline of 47.66oC. Significantly high temperatures were noted in the outflow fluid from the wand but this was not evident in the subacromial bursa itself. Although high temperatures are generated at the tip of the wand this does not appear to be transmitted to the surrounding irrigation fluid in the subacromial bursa. We therefore conclude that safe temperatures are maintained within the bursa when using this device, thereby minimizing damage to the surrounding tissues, meaning collateral thermal damage is unlikely

Heat generation during bone cutting operations inorthopaedics may cause thermal damage to the bone. During the bone cutting, the maximum temperature occurs on the contact surface between the bone and tool. Because of the low thermal conductivity and diffusivity, the temperature gradient of the bone interior is very high around the cutting site and the measurement of maximum temperature is difficult at the contact surface. While many researchers tried to measure the temperatures, they may have underestimated the temperatures of bone on account of measurement limitations. To solve this problem, we investigated the temperature distribution model of the bone interior during the milling operation and verified the model with a cutting experiment. During the bone milling, most of the cutting energy is converted into the heat energy near the contact surface between the bone and tool. If the cutting tool moves on the bone surface, we can assume that a heat source moves on the bone surface at the speed of the feed rate. To predict the maximum temperature, we performed a milling experiment with fresh bovine cortical femurs. The feed rate were 2~9.8mm/s, the cutting depth were 0.3~1mm and the rotational speed were 30,000~50,000RPM. No irrigation solutions were applied. To measure the local temperatures around the tool, two infrared thermometers were attached behind the bur at 10mmintervals from the bur center. We calculated the maximum temperatures and errors from the measured temperatures. The predicted maximum temperature increment was 55~131& #8451; as the cutting conditions change. The mean errors and standard deviation errors were several degrees. The increased feed rate and decreased cutting-depth reduced the maximum temperature. Our observed temperature is quite higher than those in the previous studies. Because of the high temperature-gradient(57& #8451;/mm), the thermocouple alone will likely yield large errors and generally underestimate the temperatures of the bone interior. With a thermal damage criterion of 50& #8451;(& #916; T=13& #8451;), thermal damage may reach 1mm in depth. To reduce the thermal damage, it is recommended to increase feed rate and decrease cutting depth

Introduction: Cementing technique is one of the important factors which determines the longevity of cemented joint replacements. There are a number of variables which determine good cementation. We hope to standardise one of the variable which is cement working and setting time. Methods: Cement was stored in a controlled temperature refrigerators at 20 degree centigrade and brought out just before mixing. Theatre temperature, cement mixing start time and time at which cement was set were recorded for 20 hip and knee replacements. These recordings were also done for 20 hip and knee replacements where cement was stored in the theatre and was used as a control. Results: Cement stored in the controlled temperature refrigerator had a more predictable working and setting time as opposed to controls. Discussion: Cement stored in the controlled temperature refrigerator eliminates one of the variables in cemented arthroplasty and may prevent complication which could occur if cement sets unpredictably

The study objective was to assess if the mechanical properties of Polylactic Acid (PLA) bio-absorbable suture anchors vary with temperature? Bio-absorbable suture anchors may offer advantages over metal anchors. However, their performance at body temperature has been questioned in recent literature (Meyer et al). In particular, constant tension at body temperature caused early failure at the anchor eyelet. Using a previously validated mechanical jig, 15 standard locked sliding arthroscopic knots (Duncan Loop + three alternate hitches) were tied by the senior author using PAN-ALOK anchors (DEPUY MITEK, Edinburgh, UK) and ETHIBOND sutures (ETHICON) and placed under a standard constant tensile load reproducing the action of the surgically repaired rotator cuff. All anchors were loaded for at least five days to match previous studies. Eight were incubated at a constant 37°C and six were kept at room temperature. The elongation of the suture knot/anchor construct was assessed by a rheostat within the mechanical jig. Sample unused, room temperature and body temperature anchors were blindly analysed using plane polarized light microscopy with a graticule to assess deformation, concentrating on the eyelet region. Mean elongation of body temperature anchors = 0.461mm (0.159 – 0.952) Mean elongation of room temperature anchors = 0.278mm (0.159 – 0.793) Unpaired t-test: p=0.24 Microscopic analysis of the anchor material showed no difference in structural deformation in the three anchors. Our model suggests no significant increase in elongation at body temperature for this commonly used arthroscopic suture anchor / knot construct. This counters previous work. It gives us confidence to continue to use such devices

Alumina and zirconia have been extensively used for orthopedic implants, such as hip and knee joint replacements. In 1982, Dr Hironobu Oonishi and Kyocera Corp. put the world’s first ceramic knee component, KOM, to practical use. This ceramic knee component shows excellent clinical results for long-time use. Now, the ceramic material of the knee component is changed from the alumina to the zirconia, and over 5000 ceramic components have been used in Japan so far. The 3 mol% yttria stabilized polycrystalline zirconia (3Y-TZP) has been used as surgical grade zirconia. The 3Y-TZP possesses higher fracture strength and toughness as compared to monolithic alumina. However, it is generally known that spontaneous transformation may also occur at relatively low temperatures in hydrothermal environment as in the case of human body for the 3Y-TZP. Therefore, there is a concern of the degradation of mechanical and wear properties as a consequence of the transformation (low temperature degradation). Our previous studies confirmed that low temperature degradation can be prevented by optimizing sintering temperature and adopting a Hot Isostatic Press process. In this study, we evaluated the effects of surface nature of ceramic material and heat treatment. Since grinding and polishing of the ceramic implants (e.g. femoral heads) might induce phase transformation, residual stress and microcracks, it is needed to examine the validity of the manufacturing process. At first, the 3Y-TZP samples with grinded (#400) and mirror polished surfaces were prepared and exposed in saturated vapor in an autoclave at 121°C for 150 h (aging test). Some of the samples were subjected to a heat treatment and then to aging test. Before and after aging test, change in crystal structure was evaluated by X-ray diffraction. Then, for evaluation of the aging effects for microscopic area of the ceramic, a Vickers indentation was introduced on the surface before the aging test. Changes in crystal structure and residual stress were evaluated by a Raman spectroscopic technique. In the results of the aging test, it was found that the degree of the increase in monoclinic fraction of both grinded and polished surfaces was lower in the samples with heat treatment than in those without heat treatment. These results indicate that the phase stability of the 3Y-TZP was improved by the heat treatment after machining. Around the indentation, circular-like deformation zone and cracks extending from the four corners of the indentation were observed. After the aging test, the transformed area gradually spread towards neighborhood regions depending on the aging time. Besides, a distinct progress of phase transformation at around the crack was also observed. On the other hand, in the samples subjected to the heat treatment, no transformed area was observed around the indentation. These results suggest that low temperature degradation could be prevented by the heat treatment after the machining. The residual stress fields induced in phase-transformed areas increased during aging test, and heat treatment after the machining was also able to prevent phase transformation even if surface damages, such as indentation or machining, were introduced on the samples