Trends in incidence and average waiting time for arthroplasty from 1998-2021: an observational study of 282,367 patients from the Scottish arthroplasty project.

BACKGROUND: Current waiting times for arthroplasty are reported as being the worst on record. This is a combination of increasing demand, the COVID-19 pandemic and longer standing shortage of capacity. The Scottish Arthroplasty Project (SAP) is a National Audit that analyses all joint replacements undertaken in the Scottish NHS and Independent Sector. The aim of this study was to investigate the long-term trend in provision and waiting time for lower limb joint replacement surgery. METHODS: All total hip replacements (THR) and total knee replacements (TKR) undertaken in NHS Scotland from 1998 to 2021 were identified. Waiting times data were analysed each year to determine the minimum, maximum, median, mean and standard deviation. RESULTS: In 1998, there were 4,224 THR and 2,898 TKR with mean (range, SD) waiting time of 159.5 days (1-1,685, 119.8) and 182.9 days (1-1,946, 130.1). The minimum waiting times were both in 2013 for 7,612 THR - 78.8 days (0-539, 46) and 7,146 TKR - 79.1 days (0-489, 43.7). The maximum waiting times recorded were in 2021 with 4,070 THR waiting 283.7 days (0-945, 215) and 3,153 TKR waiting 316.8 days (4-1,064, 217). CONCLUSIONS: This is the first robust large-scale national dataset showing trends in incidence and waiting time for THR and TKR over two decades. There was an expansion of activity with a reduction in waiting time, which peaked in 2013, followed by an increase in waiting time with a plateau and modest decline in the number of procedures.

The virtual knee clinic - A tool to streamline new outpatient referrals.

INTRODUCTION: Traditionally it has been the case for orthopaedic consultants to review GP referrals for the orthopaedic outpatient clinic where possible in amongst other clinical commitments. This could sometimes lead to unsuitable patients being reviewed and both patients and clinicians becoming frustrated. Building on the virtual fracture clinic, a new screening tool was implemented to streamline new referrals. The aim of this study is to investigate the change in patients given outpatient appointments following the introduction of a new streamlining protocol. METHODS: Referrals had to meet the criteria of BMI under 40 or evidence of weight loss effort, recent radiographs and appropriate clinical details in keeping with Getting It Right First Time (GIRFT). Consultant were given dedicated clinical time to review and either triage the patient to the most appropriate clinic type, or return the referral with advice to the GP. 10 months of data was collected prior to the protocol and 10 months after implementation. RESULTS: 1781 patients were referred pre-protocol with an average of 14.2% of these being returned. Post protocol there were 2110 patients referred with 31.2% returned. There was an increase in 195% of referrals returned to the GP (p < 0.0001). The highest proportion of these was for mild to moderate osteoarthritis on the radiograph which has been proven to be unsuitable for intervention. At 12 month analysis there was no significant increase in patients re-referred to the service (p = 0.53) DISCUSSION: The new screening tool allows more appropriate referrals to be seen in clinic allowing less frustration to clinicians and patients by reducing therapeutic inertia. Furthermore it allows new referrals to be seen by the most appropriate sub-specialist. It allows advice to be given to GPs on further management for the patient. 619 appointments were saved. At a cost of £120 per appointment, this leads to a real terms cost saving of £74,280, with further savings in time and travel.

Provision of revision knee arthroplasty services across Scotland: A national audit.

BACKGROUND: There is increasing evidence that both low surgeon and centre case volumes are associated with poorer outcomes following Revision Knee Arthroplasty (rTKA). Given the unique challenges faced in Scotland relating to funding and geography, understanding details on the complexity of cases is required to guide development of future rTKA services. METHODS: Utilising the Scottish Collaborative Orthopaedic Trainee Research Network (SCOTnet) a retrospective review of all Scottish 2019 rTKA cases was undertaken. Regional leads co-ordinated local data collection using individual case note review. The number of cases performed by regions, hospitals and individual surgeons were identified. Patient demographics and case complexity (Revision Knee Complexity Classification [RKCC]) were also collected. Results were compared against current standards. RESULTS: 17 units performed rTKA, delivered by 77 surgeons. A total of 506 cases were included. The mean age was 69 years (46% male). Revision for infection accounted for 147/506 (29%) cases. Extensor compromise was present in 35/506 (7%) and 11/506 (2%) required soft tissue reconstruction. According to the RKCC - 214/503 (43%) were classified as R1 (Less complex cases), 228/503 (45%) R2 (complex cases), and 61/503 (12%) R3 (most complex / salvage cases). 5/17 (29%) units met current national guidelines for case volume/year, with only 11/77 (14%) surgeons meeting recommended individual case volumes. 37/77 (48%) surgeons performed ≤ 2 cases per year. CONCLUSIONS: Most individual centre volumes could be increased by re-organising services or locations providing rTKA within a region. This should provide better access to Multidisciplinary Team (MDT) involvement. We recorded a significant number of very low volume surgeons (≤2 year) that is contradictory to current evidence-based practice.

Comparison of temperature and doping dependence of elastoresistivity near a putative nematic quantum critical point.

Strong electronic nematic fluctuations have been discovered near optimal doping for several families of Fe-based superconductors, motivating the search for a possible link between these fluctuations, nematic quantum criticality, and high temperature superconductivity. Here we probe a key prediction of quantum criticality, namely power-law dependence of the associated nematic susceptibility as a function of composition and temperature approaching the compositionally tuned putative quantum critical point. To probe the 'bare' quantum critical point requires suppression of the superconducting state, which we achieve by using large magnetic fields, up to 45 T, while performing elastoresistivity measurements to follow the nematic susceptibility. We performed these measurements for the prototypical electron-doped pnictide, Ba(Fe1-xCox)2As2, over a dense comb of dopings. We find that close to the putative quantum critical point, the elastoresistivity appears to obey power-law behavior as a function of composition over almost a decade of variation in composition. Paradoxically, however, we also find that the temperature dependence for compositions close to the critical value cannot be described by a single power law.

Coherent Modulation of Quasiparticle Scattering Rates in a Photoexcited Charge-Density-Wave System.

We present a complementary experimental and theoretical investigation of relaxation dynamics in the charge-density-wave (CDW) system TbTe_{3} after ultrafast optical excitation. Using time- and angle-resolved photoemission spectroscopy, we observe an unusual transient modulation of the relaxation rates of excited photocarriers. A detailed analysis of the electron self-energy based on a nonequilibrium Green's function formalism reveals that the phase space of electron-electron scattering is critically modulated by the photoinduced collective CDW excitation, providing an intuitive microscopic understanding of the observed dynamics and revealing the impact of the electronic band structure on the self-energy.

Nonequilibrium charge-density-wave order beyond the thermal limit.

The interaction of many-body systems with intense light pulses may lead to novel emergent phenomena far from equilibrium. Recent discoveries, such as the optical enhancement of the critical temperature in certain superconductors and the photo-stabilization of hidden phases, have turned this field into an important research frontier. Here, we demonstrate nonthermal charge-density-wave (CDW) order at electronic temperatures far greater than the thermodynamic transition temperature. Using time- and angle-resolved photoemission spectroscopy and time-resolved X-ray diffraction, we investigate the electronic and structural order parameters of an ultrafast photoinduced CDW-to-metal transition. Tracking the dynamical CDW recovery as a function of electronic temperature reveals a behaviour markedly different from equilibrium, which we attribute to the suppression of lattice fluctuations in the transient nonthermal phonon distribution. A complete description of the system's coherent and incoherent order-parameter dynamics is given by a time-dependent Ginzburg-Landau framework, providing access to the transient potential energy surfaces.

AC elastocaloric effect as a probe for thermodynamic signatures of continuous phase transitions.

Studying the response of materials to strain can elucidate subtle properties of the electronic structure in strongly correlated materials. Here, we focus on the elastocaloric coefficients, forming a second rank tensor quantity describing the relation between entropy and strain. In contrast to the better-known elastoresistivity, the elastocaloric effect is a thermodynamic quantity. Experimentally, elastocaloric effect measurements are demanding since the thermodynamic conditions during the measurement have to be well controlled. In this work, we present a technique to measure the elastocaloric effect under quasiadiabatic conditions. The technique is based on oscillating strain, which allows for increasing the frequency of the elastocaloric effect above the thermal relaxation rate of the sample. We apply the technique to Co-doped iron pnictide superconductors and show that the thermodynamic signatures of second order phase transitions in the elastocaloric effect closely follow those observed in calorimetry experiments. In contrast to heat capacity, elastocaloric effect measurements allow for the electronic signatures to be measured against a small phononic background even at high temperatures and in addition give information on the symmetry of the involved order parameters. This establishes the technique as a powerful complimentary tool for extracting the entropy landscape as a function of strain proximate to a continuous phase transition.

Evidence of Incoherent Carriers Associated with Resonant Impurity Levels and Their Influence on Superconductivity in the Anomalous Superconductor Pb_{1-x}Tl_{x}Te.

We present a combined experimental and theoretical study of the evolution of the Fermi surface of the anomalous superconductor Pb_{1-x}Tl_{x}Te as a function of thallium concentration, drawing on a combination of magnetotransport measurements (Shubnikov-de Haas oscillations and the Hall coefficient), angle resolved photoemission spectroscopy, and density functional theory calculations of the electronic structure. Our results indicate that for Tl concentrations beyond a critical value, the Fermi energy coincides with resonant impurity states in Pb_{1-x}Tl_{x}Te, and we rule out the presence of an additional valence band maximum at the Fermi energy. A comparison to nonsuperconducting Pb_{1-x}Na_{x}Te implies that the presence of these impurity states at the Fermi energy provides the enhanced pairing interaction and thus also the anomalously high temperature superconductivity in this material.

Surgery performed by supervised registrars does not adversely affect medium-term functional outcomes after total knee replacement.

Introduction Although total knee arthroplasty (TKA) is an index procedure for orthopaedic registrars, there is a lack of published research as to the effects of surgery when performed by supervised trainees. The aim of this study was to compare functional outcomes up to five years after primary TKA performed by consultants and trainee surgeons. Methods A retrospective analysis was conducted of prospectively collected data for 609 consecutive patients (339 female, 270 male) undergoing TKA. Patients were assessed preoperatively as well as at 18 months, three years and five years postoperatively, and American Knee Society objective knee and functional scores (AKSK and AKSF) were recorded. Results Surgery was performed by a consultant in 465 cases and a supervised trainee in 144 cases. There were no significant differences between the two groups in preoperative patient characteristics, operative time (p=0.15), transfusion rates (p=0.84), length of stay (p=0.98), manipulation under anaesthesia (p=0.69), or mortality rates at one year (p=0.73) or five years (p=0.81). Postoperatively, the median magnitude of improvement in AKSK (48 points for consultant group vs 45 points for trainee group, p=0.74) and in AKSF (both groups 15, p=0.995) was similar between the groups. AKSK and AKSF scores were similar at all timepoints up to five years following surgery, and there was no difference in the median range of motion (both groups 100°, IQR: 18°) at five years (p=0.43). Conclusions TKA performed by supervised registrars gives functional outcomes that are equivalent to consultant performed TKA, without affecting postoperative range of movement, or increasing operative time, length of stay or transfusion rates. Rates of postoperative MUA and mortality are also comparable.

Determination of the resistivity anisotropy of orthorhombic materials via transverse resistivity measurements.

Measurements of the resistivity anisotropy can provide crucial information about the electronic structure and scattering processes in anisotropic and low-dimensional materials, but quantitative measurements by conventional means often suffer very significant systematic errors. Here we describe a novel approach to measuring the resistivity anisotropy of orthorhombic materials, using a single crystal and a single measurement that is derived from a π4 rotation of the measurement frame relative to the crystallographic axes. In this new basis, the transverse resistivity gives a direct measurement of the resistivity anisotropy, which combined with the longitudinal resistivity also gives the in-plane elements of the conventional resistivity tensor via a 5-point contact geometry. This is demonstrated through application to the charge-density wave compound ErTe3, and it is concluded that this method presents a significant improvement on existing techniques, particularly when measuring small anisotropies.

Coexistence of Quantum and Classical Flows in Quantum Turbulence in The T=0 Limit.

Tangles of a quantized vortex line of initial density L(0)∼6×10^{3} cm^{-2} and a variable amplitude of fluctuations of flow velocity U(0) at the largest length scale are generated in superfluid ^{4}He at T=0.17 K, and their free decay L(t) is measured. If U(0) is small, the excess random component of the vortex line length first decays as L∝t^{-1} until it becomes comparable with the structured component responsible for the classical velocity field, and the decay changes to L∝t^{-3/2}. The latter regime always ultimately prevails, provided the classical description of U holds. A quantitative model of coexisting cascades of quantum and classical energies describes all regimes of the decay.

The pre-operative levels of haemoglobin in the blood can be used to predict the risk of allogenic blood transfusion after total knee arthroplasty.

AIMS: The pre-operative level of haemoglobin is the strongest predictor of the peri-operative requirement for blood transfusion after total knee arthroplasty (TKA). There are, however, no studies reporting a value that could be considered to be appropriate pre-operatively. This study aimed to identify threshold pre-operative levels of haemoglobin that would predict the requirement for blood transfusion in patients who undergo TKA. PATIENTS AND METHODS: Analysis of receiver operator characteristic (ROC) curves of 2284 consecutive patients undergoing unilateral TKA was used to determine gender specific thresholds predicting peri-operative transfusion with the highest combined sensitivity and specificity (area under ROC curve 0.79 for males; 0.78 for females). RESULTS: Threshold levels of 13.75 g/dl for males and 12.75 g/dl for females were identified. The rates of transfusion in males and females, respectively above these levels were 3.37% and 7.11%, while below these levels, they were 16.13% and 28.17%. Pre-operative anaemia increased the rate of transfusion by 6.38 times in males and 6.27 times in females. Blood transfusion was associated with an increased incidence of early post-operative confusion (odds ratio (OR) = 3.44), cardiac arrhythmia (OR = 5.90), urinary catheterisation (OR = 1.60), the incidence of deep infection (OR = 4.03) and mortality (OR = 2.35) one year post-operatively, and increased length of stay (eight days vs six days, p < 0.001). CONCLUSION: Uncorrected low pre-operative levels of haemoglobin put patients at potentially modifiable risk and attempts should be made to correct this before TKA. Target thresholds for the levels of haemoglobin pre-operatively in males and females are proposed. TAKE HOME MESSAGE: Low pre-operative haemoglobin levels put patients at unnecessary risk and should be corrected prior to surgery.

Dissipation of Quasiclassical Turbulence in Superfluid

We compare the decay of turbulence in superfluid ^{4}He produced by a moving grid to the decay of turbulence created by either impulsive spin-down to rest or by intense ion injection. In all cases, the vortex line density L decays at late time t as L∝t^{-3/2}. At temperatures above 0.8 K, all methods result in the same rate of decay. Below 0.8 K, the spin-down turbulence maintains initial rotation and decays slower than grid turbulence and ion-jet turbulence. This may be due to a decoupling of the large-scale superfluid flow from the normal component at low temperatures, which changes its effective boundary condition from no-slip to slip.

Enhanced recovery programmes can reduce length of stay after total knee replacement without sacrificing functional outcome at one year.

INTRODUCTION: Enhanced recovery programmes (ERPs) are being widely adopted in total knee replacement (TKR) procedures but studies confirming that they have no adverse effects on functional outcomes are lacking. The aim of this study was to compare length of stay, postoperative functional outcome and range of motion at one year postoperatively between patients undergoing TKR with an ERP and those with traditional rehabilitation. METHODS: A total of 165 consecutive patients undergoing primary unilateral TKR were included in the study. Overall, 84 patients undergoing TKR with an ERP were compared with a series of 81 patients undergoing primary unilateral TKR with traditional rehabilitation, immediately before the introduction of the ERP. RESULTS: The median postoperative length of stay was 3 days in the ERP cohort and 4 in the traditionally rehabilitated cohort (p<0.001). There were no significant differences in the preintervention characteristics of the groups and there was no significant difference in operative time, transfusion or rates of manipulation under anaesthesia. There was no difference in magnitude of improvement in American Knee Society score (p=0.12) or range of motion (p=0.81) between the groups. CONCLUSIONS: ERP can reduce length of stay after TKR while offering improvements in knee function equivalent to those experienced by patients undergoing TKR with traditional rehabilitation. Furthermore, ERP can be implemented successfully in the setting of a district general hospital.

Validation of a prediction model that allows direct comparison of the Oxford Knee Score and American Knee Society clinical rating system.

This study demonstrates a significant correlation between the American Knee Society (AKS) Clinical Rating System and the Oxford Knee Score (OKS) and provides a validated prediction tool to estimate score conversion. A total of 1022 patients were prospectively clinically assessed five years after TKR and completed AKS assessments and an OKS questionnaire. Multivariate regression analysis demonstrated significant correlations between OKS and the AKS knee and function scores but a stronger correlation (r = 0.68, p < 0.001) when using the sum of the AKS knee and function scores. Addition of body mass index and age (other statistically significant predictors of OKS) to the algorithm did not significantly increase the predictive value. The simple regression model was used to predict the OKS in a group of 236 patients who were clinically assessed nine to ten years after TKR using the AKS system. The predicted OKS was compared with actual OKS in the second group. Intra-class correlation demonstrated excellent reliability (r = 0.81, 95% confidence intervals 0.75 to 0.85) for the combined knee and function score when used to predict OKS. Our findings will facilitate comparison of outcome data from studies and registries using either the OKS or the AKS scores and may also be of value for those undertaking meta-analyses and systematic reviews.

Anomalous critical fields in quantum critical superconductors.

Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs remains poorly understood. The iron-pnictide superconductor BaFe2(As(1-x)P(x))2 is perhaps the clearest example to date of a high-temperature quantum critical superconductor, and so it is a particularly suitable system to study how the quantum critical fluctuations affect the superconducting state. Here we show that the proximity of the QCP yields unexpected anomalies in the superconducting critical fields. We find that both the lower and upper critical fields do not follow the behaviour, predicted by conventional theory, resulting from the observed mass enhancement near the QCP. Our results imply that the energy of superconducting vortices is enhanced, possibly due to a microscopic mixing of antiferromagnetism and superconductivity, suggesting that a highly unusual vortex state is realized in quantum critical superconductors.

Reconnections of quantized vortex rings in superfluid 4He at very low temperatures.

Collisions in a beam of unidirectional quantized vortex rings of nearly identical radii R in superfluid 4He in the limit of zero temperature (0.05 K) were studied using time-of-flight spectroscopy. Reconnections between two primary rings result in secondary vortex loops of both smaller and larger radii. Discrete steps in the distribution of flight times, due to the limits on the earliest possible arrival times of secondary loops created after either one or two consecutive reconnections, are observed. The density of primary rings was found to be capped at the value 500 cm-2R-1 independent of the injected density. This is due to collisions between rings causing the piling up of many other vortex rings. Both observations are in quantitative agreement with our theory.

A compact rotating dilution refrigerator.

We describe the design and performance of a new rotating dilution refrigerator that will primarily be used for investigating the dynamics of quantized vortices in superfluid (4)He. All equipment required to operate the refrigerator and perform experimental measurements is mounted on two synchronously driven, but mechanically decoupled, rotating carousels. The design allows for relative simplicity of operation and maintenance and occupies a minimal amount of space in the laboratory. Only two connections between the laboratory and rotating frames are required for the transmission of electrical power and helium gas recovery. Measurements on the stability of rotation show that rotation is smooth to around 10(-3) rad s(-1) up to angular velocities in excess of 2.5 rad s(-1). The behavior of a high-Q mechanical resonator during rapid changes in rotation has also been investigated.

Quasiparticle mass enhancement close to the quantum critical point in BaFe2(As(1-x)P(x))2.

We report a combined study of the specific heat and de Haas-van Alphen effect in the iron-pnictide superconductor BaFe2(As(1-x)P(x))2. Our data when combined with results for the magnetic penetration depth give compelling evidence for the existence of a quantum critical point close to x=0.30 which affects the majority of the Fermi surface by enhancing the quasiparticle mass. The results show that the sharp peak in the inverse superfluid density seen in this system results from a strong increase in the quasiparticle mass at the quantum critical point.

Excimers He2* as tracers of quantum turbulence in 4He in the t = 0 limit.

We have studied the interaction of metastable 4He2* excimer molecules with quantized vortices in superfluid 4He in the zero temperature limit. The vortices were generated by either rotation or ion injection. The trapping diameter of the molecules on quantized vortices was found to be 96±6 nm at a pressure of 0.1 bar and 27±5 nm at 5.0 bar. We have also demonstrated that a moving tangle of vortices can carry the molecules through the superfluid helium.