Consideration of Medial Anatomical Structures at Risk when Placing Quadricortical Syndesmotic Fixation

Category: Trauma Introduction/Purpose: Surgical fixation of ankle fractures with syndesmotic instability using quadricortical fixation through the fibula and tibia is commonly performed to maintain mortise congruency. Quadricortical fixation can be achieved by screws or suture buttons however both involve unprotected drilling and placement of hardware through the medial distal tibia which places anatomic structures at iatrogenic risk. These structures may include the anterior tibialis tendon, the saphenous neurovascular bundle (SNVB) and posteriorly, the posterior tibialis tendon (PTT). This study aims to radiographically map the anatomic course of these structures at risk on a lateral radiograph as would be used intraoperatively during syndesmotic fixation. Methods: Eighteen fresh-frozen cadaveric feet were dissected with preservation of all soft tissue and neurovascular structures over the medial distal tibia. While preserving fascial and tendinous sheath attachments, the SNVB and the PTT were identified and marked with metal wiring. Standardized and calibrated lateral radiographs were obtained to determine the anatomic course of these structures. Lateral radiographs of the distal tibia and fibula were analyzed by a grid system comprised of 1 cm row-increments moving cranially from the ankle joint up to 5 cm and by 3 evenly distributed parallel columnar zones from anterior to posterior (see Figure). The anterior boundary of the columnar zone was placed at the anterior tibial shaft and the posterior boundary was placed at the posterior malleolus of the tibia. The position of respective metal wires placed within the SNVB and the anterior portion of the PTT were charted according to this grid system and results compiled. Results: The SNVB was located in zone 1 or 2 (or anterior to zone 1) in 97.3% of specimens (107/110). The SNVB traversed from proximal-posterior to distal-anterior. For the 16 specimens that crossed a columnar zone, the most common crossover was from zone 2 to zone 1 at 3-4 cm above the ankle joint which occurred in 43.8% (7 of 16) specimens. The PPT was found in zone 3 in all specimens (n=18) with only one specimen demonstrating crossover of a columnar zone into zone 2 at its most distal extent (0-1 cm). The PTT was noted to pass behind (radiographically overlap) with the tibia in 83.3% (15 of 18) of specimens between 1 and 3 cm above the ankle joint. Conclusion: Inappropriate placement of quadricortical syndesmotic fixation may place structures on the medial ankle at risk given blind drilling and hardware placement. The SNVB is at considerable risk along the anterior course of the distal tibial while the PTT is only at risk in zone 3 at the distal extent of the tibia when a true lateral radiograph is obtained. This grid system allows a simple intra-operative check to guide safer placement of quadricortical syndesmotic fixation.

On the Problems of a Migrating Hot Spot

In this work the meaning of a migrating hot spot during solidification will be discussed. Initially, just after mould filling, global as well as local thermal centres, or hot spots, are established. This occurs at mass concentrations and heavy sections as the mould wall initially is at ambient temperature. However, these hot spots are found to be migrating during solidification. This migration influences any temperature measurement and subsequent thermal analysis, introducing uncertainties. It has also been found that common casting defects such as shrinkage porosity and metal expansion penetration can be associated with a migrating hot spot. In these cases the final position of the hot spot is located across the interface between the casting and the mould. The solidification starts at the mould walls and it was found that the columnar zone is affected by the migrating hot spot. The macrostructure was preserved using DAAS technique and it was revealed that an otherwise normal columnar zone because of the migrating hot spot had been affected. Based on these findings it is suggested that the migrating hot spot is making the columnar zone weaker and more susceptible for pressure differences arising during solidification.

The Monolithic Glass-Ceramic Lined Steel Elbow Made by SHS Gravitational-Thermite Process

A monolithic glass-ceramic lined steel elbow with 900-bend angle was fabricated using a self-propagating high-temperature synthesis gravitational-thermite process (SHS G-T process). The manufacture principle and some technologies were introduced. Experiment results showed that the inner surface of the composite elbow was smooth and there were no visible cracks and pores in it. The coating layer was symmetry and was of ~ 2.5 mm thick. It consisted of two zones (glass-like zone, columnar zone) and that there existed three phases (Al2O3, glass and Fe particles) in both of the two zones. However, the Al2O3 grains were different evidently in the two zones. XRD results showed that there was no hercynite phase in the coating layer.

Depth Profiling Biaxial Stresses in Sputter Deposited Molybdenum Films; Use of the Cos2φ Method

Depth profiles of intrinsic in-plane, biaxial stresses were obtained as a function of τ, the 1/e penetration depth, in a 1.0 um thick planar d. c. magentron sputter deposited molybdenum film using asymmetric grazing incidence x-ray diffraction (GIXD). τ was varied between 20 and 276 Å. The stresses σ11 and σ22 were characterized in the directions parallel and perpendicular to the long axis of the cathode respectively using a cos2φ method. The results show that starting from τ=17Å, σ11 and σ22 are compressive and become rapidly more compressive with a minimum at τ ∼ 20 - 40 Å thereafter increasing gradually toward tensile values. The reasons for the shape of the stress gradient are not well understood but may be related to the relaxation of the stresses at the tops of the columnar Zone T-type microstructure and to the oxygen gradient in the film.

Les coupoles granitiques et rhyolitiques de la region de Fort-Lamy (Tchad)

Describes several rock masses rising above the Quaternary plain of the Chad region (French Equatorial Africa) in the vicinity of Fort-Lamy. East of Fort-Lamy, most of them consist of a cupola of normal granite capped by a columnar zone whose interstices are characterized by rhyolitic facies, above which isolated round masses of granite in rhyolite or, in some cases, pure rhyolite occur, the transition frequently taking place within 20 meters. Northwest of Fort-Lamy, the structures are similar but the rock is almost entirely rhyolitic; one of them certainly is the upper part of a volcano.