The Measurement of the Stratum Corneum Reservoir. A Predictive Method for In Vivo Percutaneous Absorption Studies: Influence of Application Time

The relation existing in vivo between the reservoir function of the stratum corneum following a 30-mm application time and the total percutaneous absorption of molecules applied for a longer time was studied on hairless rats. One thousand nanomoles of 4 radiolabeled molecules (theophylline, nicotinic acid, acetyl salicylic acid, benzoic acid) were applied on 1 cm2 of back skin for 0.5, 2, 4 and 6 h. The total recovery in excreta and the whole animal body were measured 4 days later in order to determine the level of absorption. A direct proportionality (r = 0.99) between the total percutaneous absorption of these compounds and the duration of their application was observed. This suggests that a constant flux of penetration does exist in vivo. The reservoir function of the stratum corneum was measured by successive stripping of the treated area. Following a 30-mm application, a strict correlation (r = 0.99) between the total amounts of molecules penetrated in 4 days and the amounts found in the reservoir of the horny layer was demonstrated.All together these findings show that the simple knowledge of the reservoir effect of the stratum corneum for a molecule applied for 30 mm allows the predictive assessment of its total penetration resulting from various times of application

Entry Point Variation in the Osseous Fixation Pathway of the Anterior Column of the Pelvis—A Three-Dimensional Analysis

Fractures of the superior pubic ramus can be treated with screw insertion into the osseous fixation pathway (OFP) of the anterior column (AC). The entry point determines whether the screw exits the OFP prematurely. This can be harmful when it enters the hip joint or damages soft tissues inside the lesser pelvis. The exact entry point varies between patients and can be difficult to ascertain on fluoroscopy during surgery. The aim of this study was to determine variation in the location of the entry point. A retrospective single center study was performed at a level 1 trauma center in the Netherlands. Nineteen adult patients were included with an undisplaced fracture of the superior pubic ramus on computer tomography (CT)-scan. Virtual three-dimensional (3D) models of the pelvises were created. Multiple screws were placed per AC and the models were superimposed. A total of 157 screws were placed, of which 109 did not exit the OFP prematurely. A universally reproducible entry point could not be identified. A typical crescent shaped region of entry points did exist and was located more laterally in females when compared to males. Three-dimensional virtual surgery planning can be helpful to identify the ideal entry points in each case

True accuracy, intersystem accuracy and repeatability measurements.

Schematic overview of measurements performed using 3dMD and SPENTYS imaging systems.</p

Intersystem accuracy.

Two 3D imaging systems (A, B) with accompanying surface meshed (C, D). Section (E) shows the color-coded-heat map of the intersystem accuracy of the left arm of one of the particpants.</p

Boxplots of the intersystem accuracy and repeatability.

Outcomes of both 3D imaging 207 systems are represented in mm. Outliers are represented by circles.</p

Boxplots of mean distances.

Mean distances measured by the SPENTYS system, 3dMD 186 system and digital calliper. The mean and variance are given for measurement paths A, B and 187 C of the phantom.</p

Three-dimensional printed phantom.

Letters between geometrical markers indicate measurement paths.</p

S1 Data -

Table 1: Intersystem accuracy per patient and scanned arm. Table 2: Repeatability 3dMD system per patient and scanned arm. Table 3: Repeatibility 3dMD system per patient and scanned arm. Figures: Histograms of the Mean absolute difference of Intersystem accuracy and 3D scanner Repeatability. (PDF)</p