Kinematic analysis of a posterior cruciate retaining mobile-bearing total knee arthroplasty

Using video fluoroscopy, 10 subjects having a mobile-bearing posterior cruciate-retaining total knee arthroplasty were analyzed to determine their in vivo kinematic patterns. Under weight-bearing conditions, while in extension, the average contact position was posterior to the mid-tibia sagittal plane with posterior translation of both condyles to 60 degrees of flexion, followed by anterior translation to 120 degrees of flexion. Under non-weight-bearing conditions, the average condylar contact positions were significantly more anterior from full extension to 90 degrees of knee flexion (P=.01). The average range of motion was 129 degrees under non-weight-bearing conditions and 119 degrees during weight-bearing. Although subjects in this study exhibited variable motion patterns, they are accommodated by the unconstrained optimized articulation of this highly conforming mobile-bearing implant.     

Motion of a mobile bearing knee allowing translation and rotation.

The kinematics of a mobile bearing knee, which allowed +/-20 degrees of rotation and 4.5 mm of anteroposterior translation, was measured for ascending and descending a step, deep-knee bend, normal walking, and twisting. A fluoroscopic technique was used, analyzed by 2 different methods. The rotations and displacements during the activities were similar to those of moderate-to-high constrained fixed bearing knees. The motion patterns were variable among test subjects and in general did not reproduce normal knee motion. Because of the freedom of anteroposterior translation and rotation in the design, however, each knee could determine its own neutral position and its own axis of internal-external rotation, depending on the activity.     

Kinematic comparison of posterior cruciate sacrifice versus substitution in a mobile bearing total knee arthroplasty

Interest in mobile bearing total knee arthroplasty (TKA) has increased significantly. The objective of this in vivo study was to analyze 2 different mobile bearing TKAs during gait and during a knee bend from 0 degrees to 90 degrees flexion. Femorotibial contact positions for 10 subjects, implanted by a single surgeon, were analyzed using videofluoroscopy. Five subjects were implanted with a posterior-stabilized mobile bearing TKA (PS), and 5 subjects were implanted with a posterior cruciate-sacrificing mobile bearing TKA (PCS). Each subject, while under fluoroscopic surveillance, performed 2 weight-bearing activities: i) normal gait and ii) deep-knee bend. This study showed that the kinematic patterns for subjects having either a PS or PCS mobile bearing TKA were similar during gait but different during a deep-knee bend. Subjects having a PS TKA experienced more posterior femoral rollback of the lateral condyle during the deep-knee bend. Findings of kinematic similarities in gait and differences in a deep-knee bend between these 2 mobile bearing designs are similar to previously published findings of fixed bearing posterior cruciate-retaining and PS TKA.     

Concentration and proteolysis of CX3CL1 may regulate the microglial response to CX3CL1

Fractalkine (FKN) is a membrane-bound chemokine that can be cleaved by proteases such as ADAM 10, ADAM 17, and cathepsin S to generate soluble fragments. Studies using different forms of the soluble FKN yield conflicting results in vivo. These observations prompted us to investigate the function and pharmacology of two commonly used isoforms of FKN, a human full-length soluble FKN (sFKN), and a human chemokine domain only FKN (cdFKN). Both are prevalent in the literature and are often assumed to be functionally equivalent. We observed that recombinant sFKN and cdFKN exhibit similar potencies in a cell-based cAMP assay, but binding affinity for CX3CR1 was modestly different. There was a 10-fold difference in potency between sFKN and cdFKN when assessing their ability to stimulate β-arrestin recruitment. Interestingly, high concentrations of FKN, regardless of cleavage variant, were ineffective at reducing pro-inflammatory microglial activation and may induce a pro-inflammatory response. This effect was observed in mouse and rat primary microglial cells as well as microglial cell lines. The inflammatory response was exacerbated in aged microglia, which is known to exhibit age-related inflammatory phenotypes. We observed the same effects in Cx3cr1−/− primary microglia and therefore speculate that an alternative FKN receptor may exist. Collectively, these data provide greater insights into the function and pharmacology of these common FKN reagents, which may clarify conflicting reports and urge greater caution in the selection of FKN peptides for use in in vitro and in vivo studies and the interpretation of results obtained using these differing peptides.     

Vascular function is not impaired early in the course of bipolar disorder

ObjectiveIndividuals with bipolar disorder face a nearly two-fold increased risk of cardiovascular mortality relative to the general population. Endothelial dysfunction precedes cardiovascular disease and serves as a quantifiable phenotype for vasculopathy. We investigated whether individuals with bipolar disorder had poorer vascular function than controls using a case–control design.MethodsThe sample of 54 participants included 27 individuals with bipolar disorder and 27 age- and gender-matched controls. Participants underwent an assessment of metabolic (weight, lipids, and insulin resistance) and vascular parameters (endothelial function using flow-mediated dilation; arterial stiffness using pulse wave velocity and estimated aortic pressure).ResultsParticipants had a mean age of 32 years and 41% were female. No significant differences were found between groups in endothelial function or arterial stiffness. Individuals with bipolar disorder demonstrated 100% greater insulin resistance.ConclusionThe lack of clinically significant differences in vascular function in this young sample suggests any increased risk either occurs later in the course of illness or is largely due to behavioral risk factors, such as smoking, which was balanced between groups. Substantial insulin resistance is identifiable early in course of illness, perhaps secondary to treatment.     

Hospital mortality is associated with ICU admission time

Introduction  

Previous studies have shown that patients admitted to the intensive care unit (ICU) after “office hours” are more likely to die. However these results have been challenged by numerous other studies. We therefore analysed this possible relationship between ICU admission time and in-hospital mortality in The Netherlands.     

The evolution of urethral stricture and urethroplasty practice over 15 years: A single-center,single-surgeon, 1319 urethroplasty analysis

IntroductionThe management of urethral stricture has evolved over the last several decades. We sought to analyze urethral stricture and urethroplasty trends at a tertiary referral center over a 15-year period.MethodsPatients undergoing urethroplasty by a single surgeon from August 2003 to July 2018 were analyzed. Patient demographics, urethroplasty techniques, and outcomes were collected in a prospectively maintained database and were categorized into three five-year tertiles based on date of surgery. These tertiles were subsequently retrospectively analyzed for trends and changes in practice.ResultsA total of 1319 urethroplasties were completed over the study period. During the first five years (T1), 299 urethroplasties were performed, with 431 and 589 performed in T2 and T3, respectively. Mean overall patient age was 46.8 years, which increased significantly over time (p<0.001). Idiopathic strictures were most common (n=516, 39.1%) and unchanged over time, while proportionately radiation-induced strictures increased (n=9, 3.0% [T1], n=22, 5.1% [T2], n=51, 8.7% [T3]; p=0.001) as did iatrogenic and lichen sclerosus strictures. Mean stricture length (4.7 cm [T1], 4.8 cm [T2], 4.0 cm [T3]; p<0.001) and the mean number of prior endoscopic procedures (3.4 [T1], 3.9 [T2], and 2.5 [T3]; p<0.001] decreased over time. Single-stage urethroplasty with buccal mucosa was the most common technique performed (n=656, 49.7%) that increased in prevalence (p=0.009), while both flap and staged techniques decreased (p=0.008, p=0.004, respectively). Overall success rate was 90.1% (n=1106), which improved significantly with time (n=248, 86.7% [T1], n=359, 90.0% [T2], n=499, 93.4% [T3]; p=0.001).ConclusionsWe observed that patients and treatment of urethral stricture evolved over 15 years in practice, with an increase in patient age, radiation, and iatrogenic and lichen sclerosus strictures, while demonstrating a decrease in stricture length and the number of prior endoscopic procedures performed. Increased use of single-stage urethroplasty using buccal mucosa was observed, which may have contributed to an increase in urethroplasty success over time.

KEY MESSAGES

• Urethroplasty practice has evolved over the last 15 years likely in response to urological society guidelines, innovations in surgical technique, and locoregional referral patterns.
• With time, urethroplasty volume increased, along with changes in patient demographics, stricture etiology, and complexity.
• In the last five years, stricture length decreased, along with a reduction in the number of endoscopic procedures performed prior to referral, with a concurrent increase in urethroplasty success.
• There has been a significant trend toward wide-spread adoption of single-stage urethroplasty with buccal mucosa at the expense of staged and penile fasciocutaneous flap reconstruction.