Quantitative Effect of Pelvic Position on Radiographic Assessment of Acetabular Component Position.

BACKGROUND: Intraoperative fluoroscopy aims to improve component position in total hip arthroplasty. Measurement bias related to image quality, however, has not been quantified. We aim to quantify measurement bias in the interpretation of acetabular component position as a function of pelvis and fluoroscopic beam position in a simulated supine total hip arthroplasty model. METHODS: Posterior-anterior pelvis and hip images were obtained using a previously described pelvic model with known acetabular component position. Pelvic position was varied in 5° increments of pelvis rotation (iliac-obturator) and tilt (inlet-outlet), and in 1 cm increments from beam center in cranial-caudal and medial-lateral planes. Multiple regression analyses were conducted to evaluate the relationship between the resulting bias in interpretation of component position relative to pelvis position. RESULTS: Anteversion and abduction measurement bias increased exponentially with increasing deviation in rotation and tilt. Greater bias occurred for anteversion than for abduction. Hip centered images were less affected by pelvis malposition than pelvis centered images. Deviations of beam center within 5 cm in the coronal plane did not introduce measurement bias greater than 5°. An arbitrarily defined acceptable bias of ±5° for both abduction and anteversion was used to identify a range of optimum pelvic positioning each for hip and pelvis centered imaging. CONCLUSION: Accurate measurement of acetabular component abduction and anteversion, especially anteversion, is sensitive to proper pelvic position relative to the chosen radiographic plane. An acceptable measurement bias of ±5° is achieved when the pelvis is oriented within a newly identified range of optimum pelvic positioning.

Defined populations of bone marrow derived mesenchymal stem and endothelial progenitor cells for bladder regeneration.

PURPOSE: Autologous sources of bone marrow mesenchymal stem cells and endothelial progenitor cells are attractive alternatives to cells currently used for bladder tissue regeneration. To evaluate the potential use of these cells we determined whether mesenchymal stem cells have contractile protein profiles and physiological functions similar to those of normal bladder smooth muscle cells, and determined the angiogenic potential of endothelial progenitor cells. MATERIALS AND METHODS: Mesenchymal stem cells and smooth muscle cells (Lonza, Gaithersburg, Maryland) underwent proliferation and Western blot analyses. Immunofluorescence imaging was performed using antibodies against smooth muscle cell epitopes. Contractility was assessed by intracellular Ca(2+) release assays and confocal microscopy after carbachol stimulation. Endothelial progenitor cells were evaluated using a chicken chorioallantoic membrane model to determine neo-angiogenic potential. RESULTS: Western blot and immunofluorescence data showed that mesenchymal stem cells endogenously expressed known smooth muscle cell contractile proteins at levels similar to those of smooth muscle cells. Ca(2+) release assays revealed that smooth muscle cells and mesenchymal stem cells responded to carbachol treatment with a mean +/- SD of 8.6 +/- 2.5 and 5.8 +/- 0.8 RFU, respectively, which was statistically indistinguishable. Proliferation trends of mesenchymal stem cells and control smooth muscle cells were also similar. Chorioallantoic membrane assay showed the growth of vasculature derived from endothelial progenitor cells. CONCLUSIONS: Data demonstrate that mesenchymal stem cells and smooth muscle cells express the same contractile proteins and can function similarly in vitro. Endothelial progenitor cells also have the ability to form vasculature in an in vivo chorioallantoic membrane model. These findings provide evidence that mesenchymal stem cells and endothelial progenitor cells have characteristics that may be applicable for bladder tissue regeneration.

Do current bladder smooth muscle cell isolation procedures result in a homogeneous cell population? Implications for bladder tissue engineering.

PURPOSE: Conventional techniques used to harvest and culture bladder smooth muscle cells (SMCs) have been thought to yield homogeneous populations of SMCs. In order to delineate the cellular composition of tissue derived bladder cells, this study was conducted to determine whether current culturing techniques result in a uniform population of bladder SMCs that may be utilized for bladder tissue engineering. METHODS: Patient derived bladder muscle was isolated and manually minced followed by enzymatic digestion. Cells were cultured in D: -valine alpha-MEM with decreasing levels of fetal bovine serum then fixed and permeabilized for flow cytometric and immunofluorescent analyses. Antibody staining of cultured cells consisted of alpha-SMA, von Willebrand factor, pan-cytokeratin, CD31, and CD90. Cells were visualized using directly conjugated fluorescein isothiocyanate primary or IgG-Alexa-555 conjugated secondary antibodies. RESULTS: Flow cytometric analyses revealed mixed populations of cells expressing non-SMC epitopes as corroborated by immunofluorescent studies. High density oligonucleotide array analysis revealed expression levels of known bladder SMC genes and the expression of endothelial and fibroblast related markers (P < 0.005). CONCLUSIONS: Phenotypic analyses demonstrate cell heterogeneity when SMCs are acquired and cultured through conventional methods. Standardized criteria based upon objective experimentation need to be established in order to better characterize bladder SMCs that are to be utilized for bladder tissue engineering.