Effect of Distal Tibial Varus and Valgus Deformity on Tibiotalar Joint Contact

Category: Ankle; Basic Sciences/Biologics Introduction/Purpose: To study the effect of different degrees of distal tibial varus and valgus deformities on the tibiotalar joint contact, and to understand the role of fibular osteotomy. Methods: Eight cadaveric lower legs were used for biomechanical study. Nine conditions were included: normal ankle joint (group A), 10° varus (group B), 5° varus (group C), 5° valgus (group D), 10° valgus (group E) with fibular preserved, and 10° varus (group F), 5° varus (group G), 5° valgus (group H), and 10° valgus (group I) after fibular osteotomy. The joint contact area, contact pressure, and peak pressure were tested; and the translation of contact force center was observed. Results: The joint contact area, contact pressure, and peak pressure had no significant difference between group A and groups B to E (P>0.05). After fibular osteotomy, the contact area decreased significantly in groups F and I when compared with group A (P<0.05); the contact pressure increased significantly in groups F, H, and I when compared with group A (P<0.05); the peak pressure increased significantly in groups F and I when compared with group A (P<0.05). There were two main anterior-lateral and anterior-medial contact centers in normal tibiotalar joint, respectively; and the force center was in anterior-lateral part, just near the center of tibiotalar joint. While the fibula was preserved, the force center transferred laterally with increased varus angles; and the force center transferred medially with increased valgus angles. However, the force center transferred oppositely to the medial part with increased varus angles, and laterally with increased valgus angles after fibular osteotomy. Conclusion: Fibular osteotomy facilitates the tibiotalar contact pressure translation, and is helpful for ankle joint realignment in suitable cases.

Creation of National Strike Force Center of Expertise: U. S. Coast Guard Deployable Specialized Forces “Stem-to-Stern” Review

The United States Coast Guard conducted a review of the National Strike Force’s alignment with the Coast Guard organization following direction from Admiral Papp, Commandant of the Coast Guard, for a “Stem to Stern” review of all Deployable Specialized Forces. The Deployable Specialized Force program and its support structure has made significant progress building and sustaining a highly specialized community. Some of these successes include the Incident Management Assist Team. The full purpose and integration of all Deployable Specialized Force units has still not completely achieved full operational capability. One of the recommended courses of action for Coast Guard Deployable Specialized Forces is to maintain proficiency and provide value across the Coast Guard’s mission spectrum included: Establish Centers of Expertise for disaster/incident response with functionality to include standardization teams, external assessment, and Tactics, Techniques and Policy integration. The review concluded that a separate unit should be established to conduct third party assessment of the National Strike Forces’ three Strike Teams. As a result, the National Strike Force Center of Expertise was created under the oversight of the Coast Guard Force Readiness Command. This paper will review the reasons for creation of the National Strike Force Center of Expertise and why it was placed under the Coast Guard Force Readiness Command as a detachment of Training Center Yorktown. Several functional statements of the National Strike Force Center of Expertise will be presented regarding managing environmental response and equipment standardization among the Strike Teams and how the National Strike Force Center of Expertise concept of operations will support future progress for the NSF mission.

Analysis of Hydrostatic Guideway Error Based on Multi-Head Pump

Base on the force balance theory, a model is set up to analyze the hydrostatic guideway with the closed four pads. Each oil pocket force is calculated, which is caused by the gravity center and the driving center of a slide carriage. According to the hydrostatic theory, the oil film variation that is generated during the movement is obtained. It is composed of linear and angle errors. The results show the driving force center and the geometrical center of the slide carriage have an effect on each oil film thickness, as well as the size and the location of the driving force. The article states their relationship and supplies the theoretical foundation for the design and employment of the hydrostatic guideway.

A QUASI-EXACTLY SOLVABLE N-BODY PROBLEM WITH THE sl(N+1) ALGEBRAIC STRUCTURE

Starting from a one-particle quasi-exactly solvable system, which is characterized by an intrinsic sl (2) algebraic structure and the energy-reflection symmetry, we construct a daughter N-body Hamiltonian presenting a deformation of the Calogero model. The features of this Hamiltonian are (i) it reduces to a quadratic combination of the generators of sl (N+1); (ii) the interaction potential contains two-body terms and interaction with the force center at the origin; (iii) for quantized values of a certain cohomology parameter n it is quasi-exactly solvable, the multiplicity of states in the algebraic sector is (N+n)!/(N!n!); (iv) the energy-reflection symmetry of the parent system is preserved.

Generalizing the Analysis of Shoe-Type Brake-Clutch Systems

The equations used in the analysis of asymmetrically pivoted shoe-type brake-clutch systems are derived. The equations include the pressure function, average pressure, torque, energizing effect, and parameters for locating the resultant force center. These equations are shown to be valid also in the analysis of both symmetrically pivoted and “floating” shoe type systems as well as short shoe systems, thus providing the designer with one set of equations that can be used for these common types of shoes used in brake-clutch systems. A table summarizing derived equations is given and typical graphical representations of relationships are shown.