Accumulation of uremic toxins may lead to the life-threatening condition “uremic syndrome” in patients with advanced chronic kidney disease (CKD) requiring renal replacement therapy. Clinical evaluation of proximal tubular secretion of organic cations (OC), of which some are uremic toxins, is desired, but difficult. The biomedical knowledge on OC secretion and cellular transport partly relies on studies using the fluorescent tracer 4-dimethylaminostyryl)- N-methylpyridinium (ASP+), which has been used in many studies of renal excretion mechanisms of organic ions and which could be a candidate as a PET tracer. This study is aimed at expanding the knowledge of the tracer characteristics of ASP+ by recording the distribution and intensity of ASP+ signals in vivo both by fluorescence and by positron emission tomography (PET) imaging and at investigating if the fluorescence signal of ASP+ is influenced by the presence of albumin. Two-photon in vivo microscopy of male Münich Wistar Frömter rats showed that a bolus injection of ASP+ conferred a fluorescence signal to the blood plasma lasting for about 30 minutes. In the renal proximal tubule, the bolus resulted in a complex pattern of fluorescence including a rapid and strong transient signal at the brush border, a very low signal in the luminal fluid, and a slow transient intracellular signal. PET imaging using ¹¹C-labelled ASP+ showed accumulation in the liver, heart, and kidney. Fluorescence emission spectra recorded in vitro of ASP+ alone and in the presence of albumin using both 1-photon excitation and two-photon excitation showed that albumin strongly enhance the emission from ASP+ and induce a shift of the emission maximum from 600 to 570 nm. Conclusion. The renal pattern of fluorescence observed from ASP+ in vivo is likely affected by the local concentration of albumin, and quantification of ASP+ fluorescent signals in vivo cannot be directly translated to ASP+ concentrations.

Background: Femoral neck fractures (FNF) have high mortality rates. Surgical delay likely contributes. Dynamic hip screw (DHS) fixation is common for FNF, and the tip–apex distance (TAD) measures screw position in the femoral head. A TAD >20–25 mm is considered a risk factor for screw cut-out. This study investigated the association between (1) surgical delay and complication/mortality rates within two years post-surgery and (2) TAD and postoperative complications following DHS in FNF. Methods: This retrospective study included 325 FNF patients who underwent DHS osteosynthesis at Regional Hospital Randers, Denmark from 2015–2021. The primary composite outcome included complications measured on radiographs (e.g., screw cut-out, avascular necrosis), reoperation, or death within 2 years. Radiographs were evaluated for TAD and postoperative complications/reoperations. Surgical delay was defined as the time from the diagnostic radiograph to the start of the operation. TAD was measured based on radiographs. Electronic patient journals and national SSN registers were used to assess reoperation and death rates. Results: The mortality rate was 16% within 1 year and 26% within 2 years. The complication rate was 16% within 2 years. The median surgical delay was 7.9 h (IQR 5; 14). Surgical delay was significantly associated with the 1-year mortality rate (p < 0.01), but not with the 1-year complication rate (p = 0.77). Surgical delay was associated with complication rates 2 years post-surgery only for undisplaced fractures, p = 0.046. The median TAD was 16.3 mm (13.8; 18.7); no association with complications <1 year (p = 0.56) or 20 mm, six of whom had complications, and 6/59 with TAD >25 mm, none of whom had complications. Conclusions: We report a significant association between surgical delay and mortality rates in FNF, despite surgical delays <24 h. Additionally, there was a significant association between surgical delay and risk of complication/reoperation 2 years post-surgery for undisplaced fractures. No association was found between TAD and complication rates following DHS fixation for FNF; however, only a few TAD outliers were observed.

Introduction: Orthopedic drilling and screw placement require precision to obtain the effect of bicortical screwing and avoid complications such as soft tissue damage. Traditional manual depth gauges, while effective, are prone to human error. This study evaluates the usability and acceptability of an automated electronic depth gauge compared to a conventional manual depth gauge in a preclinical setting. Methods: A randomized controlled cross-over trial was conducted with 45 participants of varying clinical experience (12 medical students, 11 resident doctors, and 22 consultants, 14/22 were senior consultants) at Aarhus University Hospital. According to randomization, participants used either the “electronic -> manual” or “manual -> electronic” depth gauge and subsequently the sequence “with -> without” or “without -> with” soft tissue protector to measure screw length in sawbones. Efficiency was assessed by measuring time (savings), and usability was evaluated using the System Usability Scale (SUS). Results: The electronic depth gauge significantly reduced the time required to measure screw length, with medical students saving the most time, p < 0.001. 65/331 (20%) of screws were changed, with no difference in the rate of screw changes between manual and electronic depth gauges, p = 0.76. Level of experience was significantly correlated with the rate of screw changes, p = 0.03. Resident doctors changed fewer screws than medical students, with no difference between the remaining groups. The median SUS score was 87.5, indicating excellent usability. Most participants rated the tool as “best imaginable” or “excellent.” Conclusion: The electronic depth gauge was time-efficient and surgeons rated it as highly usable. However, screw exchanges were not significantly minimized in this study, which might be mitigated by proper training and awareness of device-specific recommendations. The effect of electronic depth gauges on screw exchange rates and its clinical applicability warrents further research.