Discharge Behaviour and Modelling of a 1.5T REBCO Magnet With Quench Tolerant Coils Impregnated with Conductive Epoxy.

We have designed and built a small, conduction cooled, 1.5 T high-temperature superconductor (HTS) magnet. The magnet coils have been wet-wound with a novel conductive epoxy resin system to achieve a derivative of the no-insulation coil winding method. The epoxy is filled with copper powder to reliably set the turn-to-turn contact resistivity and diamond powder to accurately space the coil turns apart, as well as match the filled epoxy thermal contraction rate to that of the HTS. The magnet is designed to act as a test bed to measure sudden discharge rates and hence validate models of coil behaviour using the filled epoxy system we have developed. A lumped-element electrical model was used to predict the coil contact resistivity needed to bring the magnetic field of the 1.5 T magnet down to a near-zero level within 0.5 s. The conductive epoxy blend was tuned to give a contact resistivity of 1 × 10-6 Ω m2, based on previous measurements of coil contact resistivity at 77 K. Once the magnet was wound and tested at 40 K, we found the magnet's sudden discharge time constant was 500 ms rather than 69 ms as was predicted from the 77 K measurements. The discrepancy was traced to the temperature dependence of the contact resistivity. With further testing of the individual coils this was accounted for and the model adjusted. The predicted discharge time was 2 s, in good agreement with the measured sudden discharge time of the magnet.

Is meniscal allograft transplantation chondroprotective? A systematic review of radiological outcomes.

PURPOSE: The primary aim of this systematic review was to examine the hypothesis that meniscal allograft transplantation is chondroprotective by identifying and appraising studies that have assessed the progression of osteoarthritis following meniscal allograft transplantation. The secondary aim was to identify and appraise radiological measures of meniscal allograft integrity following surgery. METHODS: Clinical studies on human participants undergoing meniscal allograft transplantation with a minimum follow-up of 6 months were included. The primary outcome measure was any radiological osteoarthritis progression measure. Secondary outcomes included magnetic resonance measures of meniscal integrity including meniscal size, shape, healing, extrusion and signal intensity. RESULTS: Thirty-eight studies with 1056 allografts were included. The weighted mean joint space loss was 0.032 mm at 4.5 years across 11 studies. Other radiological classification systems were reported in small numbers and with variable progression rates. Meniscal extrusion was present in nearly all cases, but was not associated with clinical or other radiological outcomes. Meniscal healing rates were high, although the size, shape and signal intensity were commonly altered from that of the native meniscus. The quality of the included studies was low, with a high risk of bias. CONCLUSION: There is some evidence to support the hypothesis that meniscal allograft transplantation reduces the progression of osteoarthritis, although it is unlikely to be as effective as the native meniscus. If this is proven, there may be a role for prophylactic meniscal allograft transplantation in selected patients. Well-designed randomised controlled trials are needed to further test this hypothesis. LEVEL OF EVIDENCE: Systematic review of studies, Level IV.

Randomised controlled trial of tourniquet associated pain generated in lower limb after exsanguination by Esmarch bandage versus limb elevation.

BACKGROUND: Tourniquets are common adjuncts in the operating theatre but can be associated with post-operative pain. This study was designed to compare what effect pre-tourniquet Esmarch bandage exsanguination has on pain, compared to pre-tourniquet exsanguination by elevation alone. METHODS: 52 volunteers (104 lower limbs) were included in this study with each volunteer acting as their own matched control. The primary outcome was patient reported pain, measured in both legs simultaneously using area under curve. Secondary outcomes were pain score during inflation and deflation, cumulative pain score, duration of recovery and blood pressure during testing. RESULTS: Pain after Esmarch was superior to elevation as measured by area under pain curve (68.9 SD 26.1 vs 77.2 SD 27.3, p = 0.0010), independent of leg dominance. Cumulative pain scores demonstrated the same superiority after inflation (50.7 SD 17.1 vs 52.9 SD 17.0, p = 0.026) but not after deflation (p = 0.59). Blood pressure was not significantly different. Time to full recovery of the lower limb was the same for both groups-7.6 min (SD 2.1 min, p = 0.80). CONCLUSION: Previous studies describe a positive effect on pain when Esmarch bandage was used prior to tourniquet inflation for upper limb. Our findings suggest the same benefit from Esmarch when it was used on lower limbs-particularly during inflation of tourniquet. In addition to pain profiles, surgeon preference and patient factors need to be considered when deciding between elevation and Esmarch bandage.

Bacterial Profile, Multi-Drug Resistance and Seasonality Following Lower Limb Orthopaedic Surgery in Tropical and Subtropical Australian Hospitals: An Epidemiological Cohort Study.

We aimed to describe the epidemiology, multi-drug resistance and seasonal distribution of bacteria cultured within 12 months following lower limb orthopaedic surgery in tropical and subtropical Australian hospitals between 2010 and 2017. We collected data from four tropical and two subtropical hospitals. Categorical variables were examined using the Pearson Chi-squared test or Fisher's Exact test, and continuous variables with the Student t-test or Mann-Whitney U test. A Poisson regression model was used to examine the relationship between season, weather and the incidence of Staphylococcus and nonfermentative species. We found that at tropical sites, nonfermenters (Pseudomonas aeruginosa and Acinetobacter baumannii) were more common (28.7% vs. 21.6%, p = 0.018), and patients were more likely to culture multi-drug-resistant (MDR) nonfermenters (11.4% vs. 1.3%, p = 0.009) and MDR Staphylococcus aureus (35.9% vs. 24.6%, p = 0.006). At tropical sites, patients were more likely to be younger (65.9 years vs. 72.0, p = < 0.001), male (57.7% vs. 47.8%, p = 0.005), having knee surgery (45.3% vs. 34.5%, p = 0.002) and undergoing primary procedures (85.0% vs. 73.0%, p = < 0.001). Species were similar between seasons in both tropical and subtropical hospitals. Overall, we found that following lower limb orthopaedic surgery in tropical compared with subtropical Australia, patients were more likely to culture nonfermenters and some MDR species.

Association between higher ambient temperature and orthopaedic infection rates: a systematic review and meta-analysis.

INTRODUCTION: Many infectious diseases display seasonal variation corresponding with particular conditions. In orthopaedics a growing body of evidence has identified surges in post-operative infection rates during higher temperature periods. The aim of this research was to collate and synthesize the current literature on this topic. METHODS: A systematic review and meta-analysis was performed using five databases (PubMed, Embase, CINAHL, Web of Science and Central (Cochrane)). Study quality was assessed using the Grading of Recommendations Assessment, Development and Evaluation method. Odds ratios (ORs) were calculated from monthly infection rates and a pooled OR was generated using the DerSimonian and Lairds method. A protocol for this review was registered with the National Institute for Health Research International Prospective Register of Systematic Reviews (CRD42017081871). RESULTS: Eighteen studies analysing over 19 000 cases of orthopaedic related infection met inclusion criteria. Data on 6620 cases and 9035 controls from 12 studies were included for meta-analysis. The pooled OR indicated an overall increased odds of post-operative infection for patients undergoing orthopaedic procedures during warmer periods of the year (pooled OR 1.16, 95% confidence interval 1.04-1.30). CONCLUSION: A small but significantly increased odds of post-operative infection may exist for orthopaedic patients who undergo procedures during higher temperature periods. It is hypothesized that this effect is geographically dependent and confounded by meteorological factors, local cultural variables and hospital staffing cycles.

Management of Simultaneous Patellar Tendon and Anterior Cruciate Ligament Ruptures-A Systematic Review of Available Literature.

BACKGROUND: Combined rupture of the anterior cruciate ligament (ACL) and patellar tendon (PT) is a rare injury pattern. Currently, little evidence exists to help guide management decisions for these patients. METHODS: A systematic literature search was conducted using PubMed (MEDLINE) and Scopus (EMBASE and MEDLINE) for all articles reporting on combined rupture of the ACL and PT. The characteristic injury mechanisms, common presentation findings, and outcomes of simultaneous and staged treatment strategies were determined to provide guidance for the management of this uncommon injury pattern. An additional case report from our institution is also reported. RESULTS: Overall, 17 studies met the inclusion criteria and were included in our qualitative review. The mean age at injury was 30 years (range, 15-50 years). A high-energy injury with a rapid deceleration event through a flexed knee on a fixed foot is commonly described as the mechanism of injury. Anterior cruciate ligament rupture was missed on initial clinical examination in 24.1% compared with 17.2% for PT rupture. Injuries to the medial collateral ligament and menisci occured in 65.5% of cases. Outcome scores were reported in 41.4% (12/22) of patients undergoing staged or simultaneous repair. The Lysholm score postoperatively was 96 ± 3.3 for the staged group compared with 85.3 ± 18.6 for simultaneous repair. There were no clear differences between range of motion, time to return to sport, and complication rates between the groups. CONCLUSIONS: A high index of suspicion is required to detect concomitant ACL injuries when assessing high-energy PT ruptures. Simultaneous or staged protocols to address both injuries are safe and effective management strategies for this rare combined injury pattern. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Humidity a potential risk factor for prosthetic joint infection in a tropical Australian hospital.

BACKGROUND: Many pathogens of importance, including the staphylococcal species of concern in orthopaedics, demonstrate seasonal variations influenced by environmental factors. The aim of this study was to investigate the role of humidity as a risk factor for deep prosthetic joint infection following total knee arthroplasty (TKA) in a tropical Australian hospital. METHODS: A retrospective cohort study of all TKAs performed over a 13-year period was conducted at the author's institution. Univariate analysis was used to individually assess for a range of risk factors including humidity >60% and apparent temperature >30°C (86°F). Odds ratios (ORs) were reported. P-values <0.25 were considered as potentially important risk factors and P-values <0.05 were considered statistically significant. RESULTS: A total of 1058 primary TKAs were performed with a deep prosthetic joint infection incidence of 2.7%. Four potential risk factors were identified with P-values <0.25: (i) humidity >60% (OR 1.4; 95% confidence interval (CI) 0.68-3.04; P = 0.221); (ii) apparent temperature >30°C (86°F) (OR 2.4; 95% CI 0.56-10.1; P = 0.174); (iii) male gender (OR 2.2; 95% CI 1.02-4.81; P = 0.057); and (iv) American Society of Anesthesiologists score of III or IV (OR 2.1; 95% CI 1.00-4.49; P = 0.064). CONCLUSION: Humidity and apparent temperature may be potentially important risk factors for infection following TKA.

Nothing to sneeze at! A study into intra-operative contamination.

PURPOSE: We performed a prospective study of sneezes from orthopaedic registrars to assess the potential for intra-operative contamination from a masked surgeon, and to determine if head position can alter the potential for contamination. TYPE OF STUDY: Prospective controlled trial. METHODS: Four orthopaedic registrars from the Gold Coast Hospital each inhaled pepper to precipitate a sneeze. Cultures were taken with and without standard Smith & Nephew surgical masks, in positions directly in front and to the sides of a masked registrar. The process was repeated three times for each registrar. A control plate was left exposed to the atmosphere. A control plate and sneeze plate was cultured on blood agar. Three masks were subsequently swabbed to exclude contamination from the masks. RESULTS: 2/24 (8.33%) of the side with mask cultures returned significant bacterial growths. Also, 1/12 (8.33%) of the front with mask cultures returned significant growths. In addition, 9/12 (75%) of the direct sneezes resulted in significant bacterial counts. The control plate failed to return any growth. Subsequent culture of the exterior of three surgical masks failed to yield significant growth. There was a statistically significant odds ratio of 0.03 comparing the front and side group with the unmasked direct group. There was no statistically significant difference comparing front and side sneeze growth. CONCLUSIONS: While the use of surgical face masks significantly reduces bacterial counts following a sneeze, it fails to eliminate the potential for surgical field contamination completely. The fact that significant bacterial counts can be returned from direct culture through a mask and to the sides of a mask suggests that head position is irrelevant and contamination is possible in any direction. It is, therefore, suggested that, if possible, a sneezing surgeon distances himself/herself as much as possible from the sterile field. We also recommend following a sneeze; surgeons should re-gown and glove, given the risk of contamination of the sterile field. LEVEL OF EVIDENCE: Level II.