Open Access

Spatially resolved field emission measurements represent an important factor in further development of existing field emitter concepts. In this work, we present a novel approach that allows quantitative analysis of individual emission spots from integral current-voltage measurements using a low-cost and commercially available CMOS camera. By combining different exposure times to extrapolate oversaturated and underexposed pixels, a near congruence of integral current and image brightness is shown. The extrapolation also allows parallel investigation of all individual tips participating in the total current with currents ranging from a few nanoampere to one microampere per tip. The sensitivity, which is determined by the integral brightness-to-current ratio, remains unchanged within the measurement accuracy even after ten full measurement cycles. Using a point detection algorithm, the proportional current load of each individual tip of the field emitter array is analyzed and compared at different times during the initial measurement cycle. Together with the extracted I-V curves of single emission spots from the integral measurement, the results indicate the effect of premature burnout of particularly sharp tips during conditioning of the emitter.

We investigate the problem of path selection in radio networks for a given static set of n sites in two- and three-dimensional space. For static point-to-point communication we define measures for congestion, dilation, and energy consumption that take interferences among communication links into account. We show that energy-optimal path selection for radio networks can be computed in polynomial time. Then we introduce the diversity g(V) of a set V ⫅ ℝd for any constant d. It can be used to upper bound the number of interfering edges. For real-world applications it can be regarded as Θ(log n). A main result is that a c-spanner construction as a communication network allows one to approximate the congestion-optimal path system by a factor of O(g(V)2). Furthermore, we show that there are vertex sets where only one of the performance parameters congestion, dilation, and energy can be optimized at a time. We show trade-offs lower bounding congestion × dilation and dilation × energy. The trade-off between congestion and dilation increases with switching from two-dimensional to three-dimensional space. For congestion and energy the situation is even worse. It is only possible to find a reasonable approximation for either congestion or energy minimization, while the other parameter is at least a polynomial factor worse than in the optimal network.

Background: Due to demographic change, the number of older people in Germany and worldwide will continue to rise in the coming decades. As a result, the number of elderly and frail patients undergoing total hip and knee arthroplasty is projected to increase significantly in the coming years. In order to reduce risk of complications and improve postoperative outcome, it can be beneficial to optimally prepare geriatric patients before orthopaedic surgery and to provide perioperative care by a multiprofessional orthogeriatric team. The aim of this comprehensive interventional study is to assess wether multimorbid patients can benefit from the new care model of special orthopaedic geriatrics (SOG) in elective total hip and knee arthroplasty. Methods: The SOG study is a registered, monocentric, prospective, randomized controlled trial (RCT) funded by the German Federal Joint Committee (GBA). This parallel group RCT with a total of 310 patients is intended to investigate the specially developed multimodal care model for orthogeriatric patients with total hip and knee arthroplasty (intervention group), which already begins preoperatively, in comparison to the usual orthopaedic care without orthogeriatric co-management (control group). Patients >= 70 years of age with multimorbidity or generally patients >= 80 years of age due to increased vulnerability with indication for elective primary total hip and knee arthroplasty can be included in the study. Exclusion criteria are age < 70 years, previous bony surgery or tumor in the area of the joint to be treated, infection and increased need for care (care level >= 4). The primary outcome is mobility measured by the Short Physical Performance Battery (SPPB). Secondary outcomes are morbidity, mortality, postoperative complications, delirium, cognition, mood, frailty, (instrumental) activities of daily living, malnutrition, pain, polypharmacy, and patient reported outcome measures. Tertiary outcomes are length of hospital stay, readmission rate, reoperation rate, transfusion rate, and time to rehabilitation. The study data will be collected preoperative, postoperative day 1 to 7, 4 to 6 weeks and 3 months after surgery. Discussion: Studies have shown that orthogeriatric co-management models in the treatment of hip fractures lead to significantly reduced morbidity and mortality rates. However, there are hardly any data available on the elective orthopaedic care of geriatric patients, especially in total hip and knee arthroplasty. In contrast to the care of trauma patients, optimal preoperative intervention is usually possible.

Background: Total Hip Arthroplasty (THA) is one of the most commonly performed and successful orthopaedic surgeries. At the same time, the issue about the best surgical approach for THA remains controversial. This systematic review aims to evaluate the current evidence for the use of Minimally-Invasive Surgery (MIS) in THA. Methods: A systematic literature search of PubMed, Medline and Embase was conducted. Randomised controlled trials, comparative studies, and cohort studies were included in this systematic review. Main outcome measurements included incision length, blood loss, operating time, length of stay, complications, postoperative pain on a Visual Analogue Scale (VAS), Short Form 36/12 Health Survey (SF 36/12), Harris Hip Score (HHS) and cup inclination. Results: A total of 30 studies met the inclusion criteria. There was no significant difference between MIS and conventional approaches for THA with regards to complication rates and implant inclination angle. The average operating time in 10/24 (41%) studies was significantly (p<0.05) longer in the MIS group. MIS THA lead to an improvement, patient-centered results with reduced blood loss in 9/16 (56%), reduced use of analgesics in 4/4 (100%) and reduced myoglobin correlated muscle trauma in 3/4 (75%) of the analysed studies. Additionally, 10/10 (100%) studies reported less postoperative pain after MIS THA, 16/19 (84%) studies detected an improved postoperative Harris Hip score and 7/7 (100%) studies an improved SF36/12 score respectively. This resulted a reduced length of stay in 10/10 (100%) of the studies when compared to THA utilizing a conventional approach. Conclusion: MIS in THA is nowadays no longer seen as just cosmetically attractive but rather as a real improvement for the clinical outcome. There is evidence for improved patient related outcome following MIS THA.

Background: Total hip arthroplasty combined with the concept of enhanced recovery is of continued worldwide interest, as it is reported to improve early functional outcome and treatment quality without increasing complications. The aim of the study was to investigate functional outcome and quality of life 4 weeks and 12 months after cementless total hip arthroplasty in combination with an enhanced recovery concept. Methods: A total of 109 patients underwent primary cementless Total Hip Arthroplasty (THA) in an enhanced recovery concept and were retrospectively analyzed. After 4 weeks and 12 months, clinical examination was analyzed regarding function, pain and satisfaction; results were evaluated using Harris Hip score, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), EQ-5D-5L, EQ-VAS and subjective patient-related outcome measures (PROMs). Preoperatively, HADS (Hospital Anxiety and Depression Scale) was collected. A correlation analysis of age, American Society of Anesthesiologists (ASA), HADS and comorbidities (diabetes mellitus, art. hypertension, cardiovascular disease) with WOMAC, Harris Hip score (HHS) and EQ-5D was performed. Results: Patients showed a significant improvement in Harris Hip score 4 weeks and 12 months postoperatively (p < 0.001). WOMAC total score, subscale pain, subscale stiffness and subscale function improved significantly from preoperative to 12 months postoperative (p < 0.001). EQ-5D showed a significant improvement preoperative to postoperative (p < 0.001). The influence of anxiety or depression (HADS-A or HADS-D) on functional outcome could not be determined. There was a high patient satisfaction postoperatively, and almost 100% of patients would choose enhanced recovery surgery again. Conclusion: Cementless THA with the concept of enhanced recovery improves early clinical function and quality of life. PROMs showed a continuous improvement over a follow-up of 12 months after surgery. PROMs can help patients and surgeons to modify expectations and improve patient satisfaction.