Alzheimer's disease (AD) is associated with aberrant neuronal activity, which is believed to critically determine disease symptoms. How these activity alterations emerge, how stable they are over ...time, and whether cellular activity dynamics are affected by the amyloid plaque pathology remains incompletely understood. We here repeatedly recorded the activity from identified neurons in cortex of awake APPPS1 transgenic mice over four weeks during the early phase of plaque deposition using in vivo two-photon calcium imaging. We found that aberrant activity during this stage largely persisted over the observation time. Novel highly active neurons slowly emerged from former intermediately active neurons. Furthermore, activity fluctuations were independent of plaque proximity, but aberrant activity was more likely to persist close to plaques. These results support the notion that neuronal network pathology observed in models of cerebral amyloidosis is the consequence of persistent single cell aberrant neuronal activity, a finding of potential diagnostic and therapeutic relevance for AD.
Purpose
An accurate fit of a patient-specific instrument guide during an intervention is one of the critical factors affecting accuracy of the surgical procedure. In this study, we investigated how ...well osteophytes, which are abnormal bone growths that form along joints, are depicted in clinical preoperative CT scans and estimated the influence of such depiction errors on the intraoperative accuracy of the guide.
Methods
In 34 hip resurfacing patients, 227 osteophyte surface points on the anterior aspect of the femoral neck were collected intraoperatively, using an optoelectronic navigation system. These points were registered to a preoperative CT scan of the patient, and distances between collected points and segmented virtual bone surface, as well as Hounsfield units for these points, were determined. We simulated the registration error of a patient-specific guide, using a modified registration algorithm, to test placement on the anterior aspect of the femoral neck without removing any osteophytes. This error was then applied to the surgical plan of the femoral central-pin position and orientation for evaluation.
Results
The average distance between the collected points and the segmented surface was 2.6 mm. We estimated the average error for the entrance point of the central-pin to be 0.7 mm in the distal direction and 3.2 mm in the anterior direction. The average orientation error was
2
.
8
∘
in anteversion.
Conclusions
The depiction of osteophytes in clinical preoperative CT scans for proximal femurs can be unreliable and can possibly result in significant intraoperative instrument alignment errors during image-guided surgeries.
In lower-extremity surgery there are significant risks associated with the use of tourniquets. This prospective study was done to assess to what extent these risks may be offset by the potential ...advantages of tourniquets, namely reductions in blood loss, length of hospital stay and complication rates.
A prospective case study.
A major urban hospital.
Sixty-three consecutive patients scheduled for primary cemented total knee arthroplasty (TKA) were blindly randomized into tourniqet (n = 33) and non-tourniquet (n = 30) groups.
TKA during which a pneumatic tourniquet was applied or not applied to control blood loss.
Perioperative blood loss, operating time, complication rates, hospital stay and transfusion needs.
Differences in the total measured blood loss, intraoperative blood loss and the Hemovac drainage blood loss between the 2 groups were not significantly different (p > 0.25). The calculated total blood loss was actually lower in the non-tourniquet group (p = 0.02). Between the groups there were no statistical differences in surgical time, length of hospital stay, transfusion requirements or rate of complications (although there was a trend to more complications in the tourniquet group (p = 0.06)).
The effectiveness of a pneumatic tourniquet to control blood loss in TKA is questionable.
: This study was designed to test in a laboratory setting a novel computer-assisted fluoroscopic technique and a conventional fluoroscopic technique for open reduction and internal fixation (ORIF) of ...hip fractures. Our hypothesis is that a novel computer-assisted fluoroscopic technique will achieve acceptable guidewire placement in one pass, with decreased fluoroscopic time and with accuracy and precision better than conventional technique.
Prospective, randomized trials.
Laboratory.
Thirty, Sawbone, femur phantoms.
Dynamic hip screw guidewires were inserted into 15 femur phantoms under fluoroscopic guidance by using computer-assisted fluoroscopic ORIF technique, and 15 femurs were inserted by using a conventional fluoroscopic-assisted ORIF technique.
Ideal guidewire placement was defined as the center of the femoral head, 5 mm from the apical bone edge on anteroposterior and lateral views. Accuracy was measured as distance to ideal placement, and the number of passes and fluoroscopic time were noted for each trial.
The computer-assisted technique achieved an average guidewire placement that was as accurate as the conventional technique in fewer passes, 1.1 +/- 0.2 (mean +/- standard deviation) compared with 2.4 +/- 1.1 (P < 0.0001), respectively, and with fewer fluoroscopic images, 2 +/- 0 compared with 13.5 +/- 3 (P < 0.0002), respectively. Guidewire placement in both groups was within the tip-apex distance defined by Baumgaertner et al.
The computer-assisted technique was significantly more accurate and precise than conventional technique. It also required fewer drill tracks through the femur and exposed the patient and the surgical team to significantly less ionizing radiation.
Hematopoietic stem cells (HSCs) maintain balanced blood cell production in a process called hematopoiesis. As humans age, their HSCs acquire mutations that allow some HSCs to disproportionately ...contribute to normal blood production. This process, known as age‐related clonal hematopoiesis, predisposes certain individuals to cancer, cardiovascular and pulmonary pathologies. There is a growing body of evidence suggesting that factors outside cells, such as extracellular vesicles (EVs), contribute to the disruption of stem cell homeostasis during aging. We have characterized blood EVs from humans and determined that they are remarkably consistent with respect to size, concentration, and total protein content, across healthy subjects aged 20–85 years. When analyzing EV protein composition from mass spectroscopy data, our machine‐learning‐based algorithms are able to distinguish EV proteins based on age and suggest that different cell types dominantly produce EVs released into the blood, which change over time. Importantly, our data show blood EVs from middle and older age groups (>40 years) significantly stimulate HSCs in contrast to untreated and EVs sourced from young subjects. Our study establishes for the first time that although EV particle size, concentration, and total protein content remain relatively consistent over an adult lifespan in humans, EV content evolves during aging and potentially influences HSC regulation.
Despite hematopoietic stem cells losing functionality over time, the production of blood cells is continuously maintained as humans age. We report here that circulating extracellular vesicles are continuously produced over adulthood, but change in composition. Functional data support that individuals over 40 years possess extracellular vesicles that stimulate hematopoietic stem cell proliferation and potentially help support blood production as humans age.
A mathematical model for studying the passive kinematics of total knee prostheses can be useful in computer-aided planning and guidance of total joint replacement. If the insertion location and ...neutral length of knee ligaments is known, the passive kinematics of the knee can be calculated by minimizing the strain energy stored in the ligaments at any angular configuration of the knee. Insertions may be found intraoperatively, or may come from preoperative 3D medical images. The model considered here takes into consideration the geometry of the prosthesis and patient-specific information. This model can be used to study the kinematics of the knee joint of a patient after total joint replacement. The model may be useful in preoperative planning, computer-aided intraoperative guidance, and the design of new prosthetic joints.
One hundred twenty-eight knees in 107 patients with osteoarthrosis treated by valgus high tibial osteotomy were clinically reviewed. Patients were reviewed from three to 15 years postoperatively ...(mean, 7.5 years). The revision rate in the osteoarthrotic population was 10.9%. Patients who were older than 60 years of age at the time of surgery had results comparable to those patients who were younger than 60 years of age at the time of surgery. Women and men appeared to have a similar prognosis; 79.6% good and excellent results up to nine years; at ten to 15 years, 70% good and excellent.
To develop an accurate and reproducible technique for inserting Oxford Unicompartmental arthroplasties.
A protocol was developed to accurately position the femoral component of the Oxford ...Unicompartmental arthroplasty using computer-enhanced techniques. A dynamic reference body (DRB) is inserted into the femur, then antero-posterior (AP) and lateral fluoroscopic images are taken of the proximal femur. These images are digitized and entered into 3D space using a registered fluoroscopy machine. The femoral guide from the Oxford system is then placed on the medial femoral condyle in the standard manner. Holes are drilled directly towards the center of the femoral head using a registered drill. The femoral cuts are then made using the standard instruments from the Oxford set.
This procedure was carried out on 15 sawbone femurs. Component position was determined by measuring radiographs after a trial component had been inserted. The average lateral error was 1.2 degrees (standard deviation SD = 1.207), compared to 4.1 degrees (SD = 2.875) with the standard technique. The average AP error was 2.5 degrees (SD = 1.767), compared to 5.1 degrees (SD = 2.219) with the standard technique. The differences in accuracy in both planes were statistically significant (p = 0.002 for AP, 0.001 for lateral).
Using a Fluoroguide-assisted technique, we were able to insert the femoral component more precisely than when using the standard technique as described by the manufacturer.
In a prospective clinical and roentgenographic analysis of 79 knees treated by a valgus closing wedge high tibial osteotomy, the average follow-up period was 5.8 years (three to nine years); 80% of ...the patients had good or excellent results. Correction to a femorotibial angle between 6 degrees and 14 degrees of femorotibial valgus was associated with an optimal clinical result. Undercorrection to less than 5 degrees of femorotibial valgus was associated with a high (62.5%) failure rate. Patients whose distal femur had a femoral shaft-transcondylar (FS-TC) angle of less than 9 degrees have an increased incidence of undercorrection. A poor prognosis was noted in knees whose patellofemoral joint preoperatively had moderate or severe roentgenographic evidence of osteoarthritis (OA) when compared to the group whose patellofemoral compartment had no or mild roentgenographic evidence of OA. Accurate femorotibial realignment was essential for success. The slope of the distal femoral articular surface, the FS-TC angle, affects the degree of correction and should be considered in preoperative planning.
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