Comparison of extramedullary versus intramedullary referencing for tibial component alignment in total ankle arthroplasty.

BACKGROUND: The majority of total ankle arthroplasty (TAA) systems use extramedullary alignment guides for tibial component placement. However, at least 1 system offers intramedullary referencing. In total knee arthroplasty, studies suggest that tibial component placement is more accurate with intramedullary referencing. The purpose of this study was to compare the accuracy of extramedullary referencing with intramedullary referencing for tibial component placement in total ankle arthroplasty. METHODS: The coronal and sagittal tibial component alignment was evaluated on the postoperative weight-bearing anteroposterior (AP) and lateral radiographs of 236 consecutive fixed-bearing TAAs. Radiographs were measured blindly by 2 investigators. The postoperative alignment of the prosthesis was compared with the surgeon's intended alignment in both planes. The accuracy of tibial component alignment was compared between the extramedullary and intramedullary referencing techniques using unpaired t tests. Interrater and intrarater reliabilities were assessed with intraclass correlation coefficients (ICCs). RESULTS: Eighty-three tibial components placed with an extramedullary referencing technique were compared with 153 implants placed with an intramedullary referencing technique. The accuracy of the extramedullary referencing was within a mean of 1.5 ± 1.4 degrees and 4.1 ± 2.9 degrees in the coronal and sagittal planes, respectively. The accuracy of intramedullary referencing was within a mean of 1.4 ± 1.1 degrees and 2.5 ± 1.8 degrees in the coronal and sagittal planes, respectively. There was a significant difference (P < .001) between the 2 techniques with respect to the sagittal plane alignment. Interrater ICCs for coronal and sagittal alignment were high (0.81 and 0.94, respectively). Intrarater ICCs for coronal and sagittal alignment were high for both investigators. CONCLUSIONS: Initial sagittal plane tibial component alignment was notably more accurate when intramedullary referencing was used. Further studies are needed to determine the effect of this difference on clinical outcomes and long-term survivability of the implants. LEVEL OF EVIDENCE: Level III, retrospective comparative study

EXPERIMENTAL STUDY ON THE EFFECTIVENESS OF AN ENERGY DISSIPATION CONFIGURATION IN AN OPEN CHANNEL OF STEEP SLOPE

Στην παρούσα εργασία μελετάται πειραματικά η ροή σε σήραγγα υπό συνθήκες ελεύθερης επιφάνειας και έντονης κλίσης πυθμένα 1:10. Διερευνάται η δυνατότητα μείωσης της ταχύτητας ροής μέσω συνδυασμού κατακόρυφων, πλευρικών στοιχείων τραχύτητας και λεκανών καταστροφής ενέργειας με οδοντώσεις. Η μελετώμενη διάταξη στηρίζεται στην ύπαρξη επαναλαμβανομένων τμημάτων (modules) εντός των οποίων επιτυγχάνεται επαναληψιμότητα της ροής. Η αποτελεσματικότητα του σχεδιασμού διερευνήθηκε σε υδραυλικό ομοίωμα κλίμακας 1:12,5 που βασίσθηκε σε συνθήκες δυναμικής ομοιότητας κατά Froude για χαρακτηριστικές τιμές παροχής. Η επεξεργασία των μετρήσεων έδειξε ότι με κατάλληλη διάταξη πλευρικών στοιχείων τραχύτητας και διαμόρφωση της λεκάνης καταστροφής ενέργειας ελέγχεται η τιμή της ταχύτητας, ικανοποιείται η απαίτηση μεγίστου βάθους ροής σε σχέση με τις διαστάσεις της σήραγγας και επιτυγχάνεται επαναληψιμότητα της ροής σε κάθε module.The free-surface flow in a tunnel of steep bed slope 1:10 is studied experimentally. The effectiveness of vertical roughness elements on the side walls and energy dissipation basins with blocks is investigated, with the aim to reduce flow velocity in the tunnel. The design is based on the concept of repeated modules in order to achieve flow repeatability. The scale of the physical model was 1:12.5 under Froude similarity conditions. The analysis of measurements indicates that a suitable arrangement of vertical roughness elements on the side walls and a suitable design of the energy dissipation basin can control the flow velocity magnitude, satisfy the maximum flow depth requirement with respect to the tunnel dimensions, and achieve flow repeatability in each modul

Severe Osteogenesis Imperfecta in Cyclophilin B–Deficient Mice

Osteogenesis Imperfecta (OI) is a human syndrome characterized by exquisitely fragile bones due to osteoporosis. The majority of autosomal dominant OI cases result from point or splice site mutations in the type I collagen genes, which are thought to lead to aberrant osteoid within developing bones. OI also occurs in humans with homozygous mutations in Prolyl-3-Hydroxylase-1 (LEPRE1). Although P3H1 is known to hydroxylate a single residue (pro-986) in type I collagen chains, it is unclear how this modification acts to facilitate collagen fibril formation. P3H1 exists in a complex with CRTAP and the peptidyl-prolyl isomerase cyclophilin B (CypB), encoded by the Ppib gene. Mutations in CRTAP cause OI in mice and humans, through an unknown mechanism, while the role of CypB in this complex has been a complete mystery. To study the role of mammalian CypB, we generated mice lacking this protein. Early in life, Ppib-/- mice developed kyphosis and severe osteoporosis. Collagen fibrils in Ppib-/- mice had abnormal morphology, further consistent with an OI phenotype. In vitro studies revealed that in CypB–deficient fibroblasts, procollagen did not localize properly to the golgi. We found that levels of P3H1 were substantially reduced in Ppib-/- cells, while CRTAP was unaffected by loss of CypB. Conversely, knockdown of either P3H1 or CRTAP did not affect cellular levels of CypB, but prevented its interaction with collagen in vitro. Furthermore, knockdown of CRTAP also caused depletion of cellular P3H1. Consistent with these changes, post translational prolyl-3-hydroxylation of type I collagen by P3H1 was essentially absent in CypB–deficient cells and tissues from CypB–knockout mice. These data provide significant new mechanistic insight into the pathophysiology of OI and reveal how the members of the P3H1/CRTAP/CypB complex interact to direct proper formation of collagen and bone

Plethon and the Maltese Dogs

George Gemistos, also known as Plethon (c. 1355/1360-1452 or 1454), is widely acknowledged for his extensive and profound knowledge of ancient Greek and Byzantine literature. A meticulous examination of the numerous instances of his engagement with this literary tradition offers a promising avenue for achieving a deeper understanding of his philosophical thought. In this study, the sources and implications of Plethon’s use of the simile of Maltese dogs – originating from ancient Greek and Byzantine contexts – in two specific instances during his lifetime are identified and analyzed. The first instance of this metaphor appears in one of his earliest works, the Συμβουλευτικὸς πρὸς τὸν δεσπότην Θεόδωρον περὶ τῆς Πελοποννήσου (commonly referred to as De Rebus Peloponnesiacis Oratio I). The second occurs in one of his later writings, his Reply to George Scholarios (c. 1400-1472 or slightly later), which was a response to Scholarios’s refutation of Plethon’s De Differentiis (Πρὸς τὰς Σχολαρίου ὑπὲρ Ἀριστοτέλους ἀντιλήψεις). In both cases, Plethon employed the simile to critique specific moral and intellectual shortcomings. The first critique targeted the greed of the Christian courtiers of Mistras, a vice that significantly undermined the stability of the despotate of Mistras. The second critique addressed the boastfulness of George Scholarios, coupled with his inability to articulate and implement a coherent philosophical program.George Gemistos, also known as Plethon (c. 1355/1360-1452 or 1454), is widely acknowledged for his extensive and profound knowledge of ancient Greek and Byzantine literature. A meticulous examination of the numerous instances of his engagement with this literary tradition offers a promising avenue for achieving a deeper understanding of his philosophical thought. In this study, the sources and implications of Plethon’s use of the simile of Maltese dogs – originating from ancient Greek and Byzantine contexts – in two specific instances during his lifetime are identified and analyzed. The first instance of this metaphor appears in one of his earliest works, the Συμβουλευτικὸς πρὸς τὸν δεσπότην Θεόδωρον περὶ τῆς Πελοποννήσου (commonly referred to as De Rebus Peloponnesiacis Oratio I). The second occurs in one of his later writings, his Reply to George Scholarios (c. 1400-1472 or slightly later), which was a response to Scholarios’s refutation of Plethon’s De Differentiis (Πρὸς τὰς Σχολαρίου ὑπὲρ Ἀριστοτέλους ἀντιλήψεις). In both cases, Plethon employed the simile to critique specific moral and intellectual shortcomings. The first critique targeted the greed of the Christian courtiers of Mistras, a vice that significantly undermined the stability of the despotate of Mistras. The second critique addressed the boastfulness of George Scholarios, coupled with his inability to articulate and implement a coherent philosophical program