The Influence of Sagittal Pin Angulation on the Stiffness and Pull-Out Strength of a Monolateral Fixator Construct.

Monolateral pin-to-bar-clamp fixators are commonly used to stabilize acute extremity injuries. Certain rules regarding frame geometry have been established that affect construct stability. The influence of sagittal pin angulation on construct stiffness and strength has not been investigated. The purpose of this biomechanical study was to demonstrate the effect of a pin angulation in the monolateral fixator using a composite cylinder model. Three groups of composite cylinder models with a fracture gap were loaded with different mounting variants of monolateral pin-to-bar-clamp fixators. In the first group, the pins were set parallel to each other and perpendicular to the specimen. In the second group, both pins were set convergent each in an angle of 15° to the specimen. In the third group, the pins were set each 15° divergent. The strength of the constructions was tested using a mechanical testing machine. This was followed by a cyclic loading test to produce pin loosening. A pull-out test was then performed to evaluate the strength of each construct at the pin-bone interface. Initial stiffness analyses showed that the converging configuration was the stiffest, while the diverging configuration was the least stiff. The parallel mounting showed an intermediate stiffness. There was a significantly higher resistance to pull-out force in the diverging pin configuration compared to the converging pin configuration. There was no significant difference in the pull-out strength of the parallel pins compared to the angled pin pairs. Convergent mounting of pin pairs increases the stiffness of a monolateral fixator, whereas a divergent mounting weakens it. Regarding the strength of the pin-bone interface, the divergent pin configuration appears to provide greater resistance to pull-out force than the convergent one. The results of this pilot study should be important for the doctrine of fixator mounting as well as for fixator component design.

Thermic effect on metal body piercing by electrosurgery: An ex vivo study on pig skin and bovine liver.

BACKGROUND: Piercings are placed at different body sites often invisible to medical staff. They may cause additional injuries in trauma and emergency surgery by electro-cautery. OBJECTIVE: To clarify whether electrosurgery will have a direct damaging effect to the skin around a pierced skin area. METHODS: Metallic piercings were fixed at defined distances from the neutral and active electrode on abdominal pig skin. The distance of the active electrode was reduced by 5 mm increments to 0. The respective increases in temperature were determined with a thermal camera. A macroscopic and histological analysis of the area around the piercing to detect thermal damage was carried out. RESULTS: Significant increases in temperature and visible changes in the tissue around the piercing only occurred when the active electrode was in direct contact with the piercing (increase of 47.3∘C). Electro-cautery in distance of 5 to 10 mm to the piercing showed only temperature increases of less than 5∘C. CONCLUSIONS: If metallic piercings are not directly touched by the active electrode and the distance is more than 5-10 mm, no clinically relevant effect is created on the tissue in direct proximity to the piercings by electro-cautery. In an emergency surgery situation, a piercing not fixed in direct proximity to the surgical field may likely be ignored.

Malnutrition in geriatric trauma patients: Screening methods in comparison.

BACKGROUND: Malnutrition in geriatric patients is very common and an important outcome factor when treating injuries and fractures. There is actually no clear definition of the term malnutrition or recommendation for a screening method. OBJECTIVE: The purpose of this study was to determine the nutritional status of geriatric trauma patients using different screening procedures. We tested whether the body mass index (BMI) gives indication for malnutrition or if there is a correlation with more specific test procedures. METHODS: The BMI and the data of three specific screening procedures, Subjective Global Assessment (SGA), Nutritional Risk Screening (NRS) and Mini Nutritional Assessment (MNA) were calculated; clinical parameters were registered. RESULTS: There was proof of correlation (p< 0.001) between BMI and SGA; also between BMI and NRS was a significant correlation (p= 0.0004). There was less significant correlation between BMI and MNA (p= 0.05). All three screening methods correlated (p< 0.01). CONCLUSIONS: BMI and subjective statements provide first important information. The SGA not only correlates well with the BMI, but also complements the overall picture with individual information regarding medical history and clinical findings. Other more extensive methods, such as the NRS and the MNA, also show correlation and complement the overall picture with individual information.