Design and realization of a multi-coil array for B0 field control in a compact 1.5T head-only MRI scanner.

PURPOSE: To design and implement a multi-coil (MC) array for B0 field generation for image encoding and simultaneous advanced shimming in a novel 1.5T head-only MRI scanner. METHODS: A 31-channel MC array was designed following the unique constraints of this scanner design: The vertically oriented magnet is very short, stopping shortly above the shoulders of a sitting subject, and includes a window for the subject to see through. Key characteristics of the MC hardware, the B0 field generation capabilities, and thermal behavior, were optimized in simulations prior to its construction. The unit was characterized via bench testing. B0 field generation capabilities were validated on a human 4T MR scanner by analysis of experimental B0 fields and by comparing images for several MRI sequences acquired with the MC array to those acquired with the system's linear gradients. RESULTS: The MC system was designed to produce a multitude of linear and nonlinear magnetic fields including linear gradients of up to 10 kHz/cm (23.5 mT/m) with MC currents of 5 A per channel. With water cooling it can be driven with a duty cycle of up to 74% and ramp times of 500 µs. MR imaging experiments encoded with the developed multi-coil hardware were largely artifact-free; residual imperfections were predictable, and correctable. CONCLUSION: The presented compact multi-coil array is capable of generating image encoding fields with amplitudes and quality comparable to clinical systems at very high duty cycles, while additionally enabling high-order B0 shimming capabilities and the potential for nonlinear encoding fields.

Nursing students' experiences of working as healthcare support workers.

BACKGROUND: Preregistration nursing students frequently seek employment as healthcare support workers (HCSWs). However, little is known about their experience of alternating between these two roles. AIM: To explore the experiences of preregistration nursing students working as healthcare support workers. METHOD: Semi-structured interviews were conducted with three preregistration nursing students working part-time as HCSWs in the NHS. The interviews were transcribed verbatim and analysed using interpretative phenomenological analysis. FINDINGS: Analysis of the interview data produced the overarching theme of 'walking the tightrope'. The overarching theme contained four subthemes: 'preparing to get on the tightrope'; 'balancing on the tightrope'; 'having the stamina to stay on the tightrope'; and 'preparing to get off the tightrope'. CONCLUSION: Nursing students gained experience and confidence while working as HCSWs, but were challenged by the limitations and demands of the role.

The HEADS: UP Development Study: Working with Key Stakeholders to Adapt a Mindfulness-Based Stress Reduction Course for People with Anxiety and Depression after Stroke.

BACKGROUND: Following stroke, rates of mood disorder are and remain high at five years (anxiety 34.4%; depression 23%). Structured mindfulness-based stress reduction (MBSR) courses are effective in a range of health conditions, but stroke survivors find adherence challenging. We aimed to adapt a standard MBSR course specifically for people affected by stroke. METHODS: We recruited stroke survivors and family members with symptoms of anxiety and/or depression to take part in a co-development study comprising two rounds of MBSR 'taster' sessions, followed by focus groups in which views were sought on the practices sampled. Data were collected in October 2017 and May 2018 and were analysed using framework analysis, informed adaptations to mindfulness materials and delivery. RESULTS: Twenty-eight stroke survivors and seven family members participated. Nineteen (76%) stroke survivors had anxiety; 15 (60%) had depression. Five (71.4%) family members reported anxiety; n = 4 (57.1%) depression. Thirty participants attended the first round of taster sessions and focus groups; twenty (66%) the second and three (10%) were unable to attend either round. Framework analysis informed adaptations to course delivery, practices, and materials, ultimately resulting in a stroke-specific MBSR course, HEADS: UP (Helping Ease Anxiety and Depression after Stroke). CONCLUSIONS: HEADS: UP may provide a feasible, appropriate, and meaningful self-management intervention to help alleviate symptoms of mood disorder.

Online Mindfulness with Care Partnerships Experiencing Anxiety and Depression Symptoms after Stroke: Mixed Methods Case Study Research.

Purpose: To investigate the experience and outcomes for care partnerships (e.g., spouses, caregivers) who have post-stroke anxiety and/or depression symptoms and used an online mindfulness-based intervention (MBI) together. Design: Explanatory sequential mixed methods case study research. Methods: 5 care partnerships (10 participants) received online MBI, and data was collected in weeks 0, 4, and 8. Data collection involved the Hospital Anxiety Depression Scale, the Mutuality Scale, the Mindful Attention Awareness Scale, and post-intervention interviews. Clinical effectiveness was evaluated using minimal clinically important difference (MCID). Findings: Participants improved mindfulness (80%) and mutuality (30%). MCID was achieved for anxiety symptoms (50%) and depression symptoms (20%). IPA found evidence of conflicting and contradictory experiences so dialectical tension was used to articulate the continuum of perspectives and themes produced in the analysis. Conclusion: Care partnerships using online MBIs can experience improvements in mindfulness, mutuality, anxiety symptoms, and depression symptoms. The findings are complex but show the potential value of online MBI for some care partnerships living with stroke.

No Difference in Revision Rate Between Low Viscosity and High Viscosity Cement Used in Primary Total Knee Arthroplasty.

BACKGROUND: Loosening remains one of the most common reasons for revision total knee arthroplasty (TKA). Cement viscosity has a potential role in reducing revision rates for loosening. The aim of this study was to assess the outcome for loosening of the 5 most used cemented knee prostheses by constraint type, based on the cement viscosity type used. METHODS: There were 214,708 TKA procedures performed between 1999 and 2020 for a diagnosis of osteoarthritis using the 5 most commonly used minimally stabilized, posterior stabilized, and medial pivot design cemented tibial components. Only procedures with a cemented tibial component were included. Outcomes for two different cement viscosities, 140,060 high viscosity and 74,648 low viscosity cement, were compared for each fixation type within each of the three stability groups. RESULTS: There was no difference in a risk of all-cause revision when high viscosity cement was used compared to low viscosity cement for minimally stabilized prostheses (hazards ratio [HR] 1.07 [95% CI 0.99-1.15], P = .09), posterior stabilized prostheses (HR 1.03 [95% CI 0.95-1.11], P = .53), and medial pivot design prostheses (HR 1.06 [95% CI 0.80-1.41], P = .67). No difference was observed between cement viscosity types for any of the prosthesis constraint types when aseptic loosening was assessed. CONCLUSIONS: We found no difference in the risk of revision for any reason, or for loosening, with cement viscosity for the most commonly used minimally stabilized, posterior stabilized, and medial pivot TKA. The role of cement viscosity in the risk of TKA revision remains unclear and further research is required. LEVEL OF EVIDENCE: Level III Retrospective comparative study.

Intraosseous Regional Prophylactic Antibiotics Decrease the Risk of Prosthetic Joint Infection in Primary TKA: A Multicenter Study.

BACKGROUND: Recent studies have demonstrated that the administration of regional prophylactic antibiotics by intraosseous (IO) injection achieves tissue concentrations around the knee that are 10- to 15-fold higher than intravenous (IV) delivery of prophylactic antibiotics. It is currently unknown whether the use of regional prophylactic antibiotics for primary TKA would result in a lower risk of prosthetic joint infection (PJI). QUESTIONS/PURPOSES: (1) Is IO injection of prophylactic antibiotics associated with a decreased risk of early (< 12 months) deep PJI compared with traditional IV prophylactic antibiotics? (2) What other patient factors are associated with an increased risk of early PJI after TKA, and do regional prophylactic antibiotics influence these risk factors? (3) Can IO antibiotics be administered to all patients, and what complications occurred from the delivery of IO prophylactic antibiotics? METHODS: A retrospective comparative study of all primary TKAs (1909 TKAs) over a 5-year period (January 2013 to December 2017) was performed to determine the risk of early PJI. Three primary TKAs did not meet the study inclusion criteria and were excluded from the study, leaving a total of 1906 TKAs (725 IO, 1181 IV) for analysis at a minimum of 12 months after index procedure. Both cohorts exhibited similar ages, BMI, and American Society of Anesthesiologists (ASA) grades; however, a greater proportion of patients in the IO cohort were smokers (p = 0.01), while a greater proportion of patients were diabetic in the IV cohort (p = 0.006). The PJI risk between IO and IV delivery techniques was compared while adjusting for patient demographics and medical comorbidities. Complications related to IO delivery-inability to administer via IO technique, compartment syndrome, fat embolism, and red man syndrome with vancomycin use-were recorded. RESULTS: The delivery of regional prophylactic antibiotics by the IO technique resulted in a lower PJI risk than IV prophylactic antibiotics (0.1% [1 of 725] compared with 1.4% [16 of 1181]; relative risk 0.10 [95% CI 0.01 to 0.77]; p = 0.03). BMI (ß = -0.17; standard error = 0.08; p = 0.02), diabetes (ß = -1.80; standard error = 0.75; p = 0.02), and renal failure (ß = -2.37; standard error = 0.84; p = 0.01) were factors associated with of PJI, while smoking, sex, and ASA score were not contributing factors (p > 0.05). Although BMI, diabetes, and renal failure were identified as infection risk factors, the use of IO antibiotics in these patients did not result in a lower PJI risk compared with IV antibiotics (p > 0.05). IO antibiotics were able to be successfully administered to all patients in this cohort, and there were no complications related to the delivery of IO antibiotics. CONCLUSION: Surgeons should consider administering regional prophylactic antibiotics in primary TKA to reduce the risk of early PJI. Future randomized prospective clinical trials are needed to validate the efficacy of regional prophylactic antibiotics in reducing the PJI risk in primary TKA. LEVEL OF EVIDENCE: Level III, therapeutic study.

Surgeons respond to growing evidence by performing less knee arthroscopic surgery in older patients.

BACKGROUND: Recent research has shown that knee arthroscopy does not provide a meaningful clinical benefit for degenerative knee changes in the older population. The 2016 Australian Orthopaedic Association (AOA) Annual Scientific Meeting held a plenary session on this topic to educate surgeons about these research findings and communicate their clinical practice statement on this issue. This paper set out to find if there has been a change in clinical practice since this meeting. METHODS: The analysis consisted of all knee arthroscopies performed in a single city of Far North Queensland, Australia, over an 8-year period. The number and type of arthroscopies performed in patients <50 and ≥50 years of age was compared before and after the 2016 AOA plenary session. RESULTS: After the 2016 AOA educational session, there was a significant reduction in the number of debridement procedures performed in patients aged 50 years or older (275 vs. 142 per year, P < 0.01) but not in patients under 50 years of age (192 vs. 135 per year, P = 0.91). The annual number of repair procedures for all ages combined, increased from 11 per year to 60 per year (P < 0.01). CONCLUSION: The surgeons of this city have changed their knee arthroscopy clinical practice in line with the evidence and advice from their professional body.

Development and validation of 3D MP-SSFP to enable MRI in inhomogeneous magnetic fields.

PURPOSE: We demonstrate the feasibility of MRI with missing-pulse steady-state free precession (MP-SSFP) in a 4T magnet with artificially degraded homogeneity. METHODS: T1 , T2 , and diffusion contrast of MP-SSFP was simulated with constant and alternate radiofrequency (RF) phase using an extended phase graph. To validate MP-SSFP performance in human brain imaging, MP-SSFP was tested with two types of artificially introduced inhomogeneous magnetic fields: (1) a pure linear gradient field, and (2) a pseudo-linear gradient field introduced by mounting a head-gradient set at 36 cm from the magnet isocenter. Image distortion induced by the nonlinear inhomogeneous field was corrected using B0 mapping measured with MP-SSFP. RESULTS: The maximum flip angle in MP-SSFP was limited to ≤10° because of the large range of resonance frequencies in the inhomogeneous magnetic fields tested in this study. Under this flip-angle limitation, MP-SSFP with constant RF phase provided advantages of higher signal-to-noise ratio and insensitivity to B1+ field inhomogeneity as compared with an alternate RF phase. In diffusion simulation, the steady-state magnetization in constant RF phase MP-SSFP increased with an increase of static field gradient up to 8 to 21 mT/m depending on simulation parameters. Experimental results at 4T validated these findings. In human brain imaging, MP-SSFP preserved sufficient signal intensities, but images showed severe image distortion from the pseudo-linear inhomogeneous field. However, following distortion correction, good-quality brain images were achieved. CONCLUSION: MP-SSFP appears to be a feasible MRI technique for brain imaging in an inhomogeneous magnetic field.

Survivorship of highly constrained prostheses in primary and revision total knee arthroplasty: analysis of 6070 cases.

BACKGROUND: Concerns exist about the survival and complication rates of highly constrained total knee arthroplasty (TKA) prostheses. The aims of this study were to determine if there were differences between the revision and complication rates of fully stabilized (FSTKA) and hinged (HTKA) TKA, when used in both primary and revision procedures. METHODS: Survivorship of all highly constrained TKA prostheses implanted over a 17 year period were analysed by the Australian Orthopaedic Association National Joint Replacement Registry. The primary outcome measure was time to first revision using Kaplan Meier estimates of survivorship. RESULTS: In the primary setting, the cumulative percent revision at 11 years was higher for HTKA than for FSTKA prostheses (P = 0.014). However, this finding was only significant for patient >75 years. In the revision setting, there were no differences in the revision rates for either category of prosthesis for any age group. For the indication of periarticular/periprosthetic fracture, HTKA resulted in a lower revision rate than FSTKA in both primary and revision cohorts. There were no differences in the rates of revision for infection and aseptic loosening for either prosthesis type in primary or revision settings. The revision risk for periprosthetic fracture was higher after HTKA prostheses. CONCLUSION: Both FSTKA and HTKA prostheses provide similar outcomes in primary and revision procedures except for the setting of periarticular/periprosthetic fracture, where a HTKA should be used. In elderly patients, a FSTKA prosthesis is recommended as the risk of periprosthetic fracture is higher with a HTKA.

Use of regional administration of prophylactic antibiotics in total knee arthroplasty.

Prosthetic joint infection after total knee arthroplasty is an infrequent, yet serious complication. Antimicrobial prophylaxis plays an important role in reducing the rate of surgical site infections. To be effective as an antimicrobial prophylaxis, the serum, tissue and bone concentrations of the antibiotic must be greater than the target organism's minimum inhibitory concentration. As antibiotic resistance increases current intravenous prophylactic dosing has been shown to be subtherapeutic for some patients. Intravenous regional administration and intraosseous regional administration of prophylactic antibiotics are novel methods used to increase the antibiotic tissue concentrations, which may enhance the efficacy of prophylactic antibiotics in total knee arthroplasty. Currently, literature has shown both intravenous regional administration and intraosseous regional administration to be safe and effective techniques. However, there is no clinical evidence to show that it results in a reduction of prosthetic joint infection rates. This study summarizes the current knowledge base on the use of regional administration of prophylactic antibiotics in total knee arthroplasty.

Is Climate Associated With Revision for Prosthetic Joint Infection After Primary TKA?

BACKGROUND: Climate factors have been shown to be associated with spontaneous musculoskeletal and some surgical site infections with increased rates of infection during warmer periods. To date, little research has been performed to determine if this phenomenon is associated with differences in the risk of revision for prosthetic joint infection (PJI) in primary TKA. QUESTIONS/PURPOSES: (1) Does the rate of revision for early PJI within the first year after primary TKA differ between tropical and nontropical regions? (2) Is there a seasonal variation in the rate of revision for PJI? (3) Is the geographic and seasonal variation (if present) associated with the sex, age, and/or American Society of Anesthesiologists (ASA) grade of the patient? METHODS: All 219,983 primary TKAs performed for osteoarthritis over a 5-year period (2011-2015) in the Australian Orthopaedic Association National Joint Replacement Registry were examined based on the month of the primary procedure to determine the rate of revision for PJI within 12 months. The data were analyzed to determine the differences in the risk of revision for PJI based on geographic region and season of the primary procedure adjusting for sex, age, and ASA grade of the patient. RESULTS: The early revision rate for PJI was higher in the tropical compared with the nontropical region of Australia (0.73% versus 0.37%; odds ratio [OR], 1.87; 95% confidence interval [CI], 1.44-2.42; p < 0.001). The tropical region of Australia demonstrated a seasonal variation in the rate of revision for PJI with a higher rate during the warmer monsoon wet season of summer and fall (summer/fall 0.98% versus winter/spring 0.51%; OR, 1.88; 95% CI, 1.12-3.16; p = 0.02). A seasonal variation was not seen in the nontropical region (OR, 1.03; 95% CI, 0.90-1.19; p = 0.64). The regional and seasonal changes were independent of sex, age, and ASA grade. CONCLUSIONS: Climate factors are associated with the risk of early revision for PJI in patients undergoing primary TKA with rates of such revisions approximately double in tropical regions compared with nontropical regions. Additionally, tropical regions demonstrate a seasonal variation with the risk of PJI doubling during the warmer, monsoonal wet season of summer and fall. These findings should be confirmed in further studies that can better control for possible confounding variables. The mechanism for this phenomenon is not clear, and further research into this subject is also indicated. LEVEL OF EVIDENCE: Level III, therapeutic study.

Factors That Predict Failure in Anatomic Single-Bundle Anterior Cruciate Ligament Reconstruction.

BACKGROUND: Anatomic graft placement in anterior cruciate ligament (ACL) reconstruction has become the preferred technique for many surgeons. The predictive factors for graft failure in anatomic single-bundle ACL reconstruction are relatively unknown. PURPOSE: To determine the risk factors for graft failure and the relative importance of those factors in anatomic single-bundle ACL reconstruction. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: All primary anatomic ACL reconstructions undertaken at a single institution over a 2-year period were evaluated for subjective and objective measures of graft failure. Risk factors evaluated included time since ACL rupture, age, sex, body mass index, intact or deficient medial and lateral meniscus, meniscal repair, hamstring graft size, and femoral and tibial tunnel position as assessed by 3D computed tomography (CT) scan. The significant factors predicting failure and the relative importance of those factors were determined. RESULTS: At a median follow-up of 26 months, 123 patients were available for analysis. Ninety-seven patients underwent postoperative 3D CT for tunnel positions, including all 20 cases with graft failure. The significant predictors of graft failure were medial meniscal deficiency (hazard ratio [HR] 15.1; 95% CI, 4.7-48.5; P < .001), lateral meniscal deficiency (HR 9.9; 95% CI, 3-33; P < .001), shallow nonanatomic femoral tunnel positioning (HR 4.3; 95% CI, 1.6-11.6; P = .004), and younger patient age (HR 0.9; 95% CI, 0.9-1; P = .008). CONCLUSION: Meniscal deficiency is the most significant factor to predict graft failure in single-bundle anatomic ACL reconstruction. Shallow nonanatomic femoral tunnel positioning and younger patient age are additional risk factors for failure, but their relative importance is less.

Factors Predicting Meniscal Allograft Transplantation Failure.

BACKGROUND: Meniscal allograft transplantation (MAT) is performed to improve symptoms and function in patients with a meniscal-deficient compartment of the knee. Numerous studies have shown a consistent improvement in patient-reported outcomes, but high failure rates have been reported by some studies. The typical patients undergoing MAT often have multiple other pathologies that require treatment at the time of surgery. The factors that predict failure of a meniscal allograft within this complex patient group are not clearly defined. PURPOSE: To determine predictors of MAT failure in a large series to refine the indications for surgery and better inform future patients. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: All patients undergoing MAT at a single institution between May 2005 and May 2014 with a minimum of 1-year follow-up were prospectively evaluated and included in this study. Failure was defined as removal of the allograft, revision transplantation, or conversion to a joint replacement. Patients were grouped according to the articular cartilage status at the time of the index surgery: group 1, intact or partial-thickness chondral loss; group 2, full-thickness chondral loss 1 condyle; and group 3, full-thickness chondral loss both condyles. The Cox proportional hazards model was used to determine significant predictors of failure, independently of other factors. Kaplan-Meier survival curves were produced for overall survival and significant predictors of failure in the Cox proportional hazards model. RESULTS: There were 125 consecutive MATs performed, with 1 patient lost to follow-up. The median follow-up was 3 years (range, 1-10 years). The 5-year graft survival for the entire cohort was 82% (group 1, 97%; group 2, 82%; group 3, 62%). The probability of failure in group 1 was 85% lower (95% CI, 13%-97%) than in group 3 at any time. The probability of failure with lateral allografts was 76% lower (95% CI, 16%-89%) than medial allografts at any time. CONCLUSION: This study showed that the presence of severe cartilage damage at the time of MAT and medial allografts were significantly predictive of failure. Surgeons and patients should use this information when considering the risks and benefits of surgery.

Arthroscopic Meniscal Allograft Transplantation With Soft-Tissue Fixation Through Bone Tunnels.

Meniscal allograft transplantation improves clinical outcomes for patients with symptomatic meniscus-deficient knees. We describe an established arthroscopic technique for meniscal allograft transplantation without the need for bone fixation of the meniscal horns. After preparation of the meniscal bed, the meniscus is parachuted into the knee through a silicone cannula and the meniscal horns are fixed with sutures through bone tunnels. The body of the meniscus is then fixed with a combination of all-inside and inside-out sutures. This technique is reliable and reproducible and has clinical outcomes comparable with those of bone plug fixation techniques.