When inserting a lag-screw across an arthrodesis, stress is concentrated under the screw head risking asymmetrical force distribution and fracture of the cortical bone bridge. The IO FiX (Extremity Medical, NJ USA) is a new intraosseous device comprising an X-Post on one side of and parallel to the arthrodesis and a lag-screw inserted through the head of the X-Post which reinforces the cortical bone bridge. The X-Post behaves as an internal washer improving force distribution across the arthrodesis. Being intraosseous, near to the neutral axis of bend also means the device is fatigue-resistant and soft tissue irritation is reduced. The IO FiX has not been independently verified and therefore we analysed its performance in a human cadaveric ankle model. Our null hypothesis was there is no difference in force generation and contact area in an ankle arthrodesis when the IO FiX is compared with partially-threaded lag-screws. We used ten randomized cadaver ankles with a mean age of seventy-one years (44–84 years) prepared with flat arthrodesis cuts. A Tek-scan (Boston, USA) pressure transducer was used to measure force and contact area produced when the IO FiX was compared with a standard lag-screw and washer. The median average force in the IO FiX group was 3.95 kg and 2.35 kg in the lag-screw group ( Our results suggest the IO FiX improves force generation and contact area across the arthrodesis. With the theoretical advantages of reduced soft tissue irritation and a lower risk of fatigue failure, the IO FiX offers a significant advantage compared with traditional fixation techniques.
Posterior malleolar fractures are present in up to 44% of all ankle fractures. Those involving > 25% of the articular surface have a higher rate of posterior ankle instability which may predispose to post traumatic arthritis. The posterolateral approach to the distal tibia allows direct reduction and stabilization of the posterior malleolus and concomitant lateral malleolus fractures. An anatomical study was performed to establish the safe zone of proximal dissection to avoid injury to the peroneal vessels in this uncommon approach. 26 unpaired adult lower limbs were dissected using the posterolateral approach to the distal tibia as described by Tornetta et al. The peroneal artery was identified coursing through the intraosseous membrane on deep dissestion as the flexor hallucis longus muscle was reflected medially. The level of its bifurcation was also noted over the tibia. Perpendicular measurements were made from the tibial plafond to these variable anatomical locations.Introduction
Methods
Posterolateral tibial plateau fractures account for 7 % of all proximal tibial fractures. Their fixation often requires posterolateral buttress plating. Approaches for the posterolateral corner are not extensile beyond the perforation of the anterior tibial artery through the interosseous membrane. This study aims to provide accurate data about the inferior limit of dissection by providing measurements of the anterior tibial artery from the lateral joint line as it pierces the interosseous membrane. Forty unpaired adult lower limbs cadavers were used. The posterolateral approach to the proximal tibia was performed as described by Frosch et al. Perpendicular measurements were made from the posterior limit of the articular surface of the lateral tibial plateau and fibula head to the perforation of the anterior tibial artery through the interosseous membrane.Introduction
Materials and Methods
Application of an external fixator for type B and C pelvic fractures can be life saving. Anteriorly the fixator half pins can be placed in the long and thick corridor of bone in the supra-acetabular region often referred to as the low anterior ex-fix. Pins in this location are favoured as they are more stable biomechanically. The bone tunnel for the low anterior ex-fix can be visualised with an iliac oblique projection intra-operatively. In some cases despite being outside the articular surface it may still be low enough to pass through the capsular attachment of the hip joint on the anterior inferior iliac spine. We aim to provide radiological markers for the most superior fibres of the capsule to help accurate extra-capsular pin placement within the supra-acetabular bone tunnel. Thirteen cadaveric pelves, embalmed with the method of Thiel, were used for this study. An image intensifier was positioned to acquire an iliac oblique outlet view, such that the supra acetabular bone tunnel was visualised. This was achieved by positioning the beam 30 degrees cephalad and 20 degrees medial. Both left and right hemipelves were examined in this way. A standard size metallic disc was included in all images with in the acetabulum to allow for image calibration. The proximal most fibres of the hip joint capsule were marked with a K-wire so that their relation to the bone tunnel could be clearly seen on the images. Once all images were acquired they were calibrated and analysed using ImageJ Software to estimate the height and maximum width of the bone tunnel as seen on the images and the vertical distance of the superior most fibres of the capsule from the dome of the acetabulum.Introduction
Materials and Methods
