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Logic And Clinical Application Of Intramedullary Blocking Screws (Visit this link)
AAOS Annual Meeting Abstract 2004 Logic and Clinical Application of Intramedullary Blocking Screws Scientific Exhibitor Number: SE058 Hans-Werner Stedtfeld, MD, Nurnberg, Germany Peter Landgraf, MD, Nurembeg, Germany Mr. Andreas Ewert, Rostock, D Germany Thomas W F Mittlmeier, MD, Rostock, Germany Following intramedullary fixation of metaphyseal long bone fractures high rates of axial malalignment have been reported. Blocking screws have been recommended to enhance primary stability. The logic of positioning these screws, however, and the option to use them as a reduction tool have not been analysed, yet. A 2-D model of an idealized fractured long bone consists of 3 essential elements: the diaphyseal and metaphyseal fragments and a rubber band simulating soft-tissue imbalance and axial deformity. A plastic rod representing an intramedullary nail can be introduced from both sides. Plastic sticks representing blocking screws can be plugged into holes at various positions of the two 'fragments'. The model allowed to derive general rules for positioning of blocking screws valid in any metaphyseal long bone fracture. The standard position of the blocking screw is: 1. in the metaphyseal fragment 2. close to the fracture 3. at the concave side of the axial deformity. In selected situations of high-degree instability an additional screw can be placed at the short fragment, on the convex side of the deformity and distant from the fracture. The basic biomechanical effect is an intramedullary three-point fixation. Clinical application has proven validity of the rules in fractures of the proximal humerus (n = 7), the subtrochanteric area (n = 5), the distal femur (n = 9), the proximal (n = 12) and distal tibia (n = 15) which all healed uneventfully within the limits of <5° of axial deformity.
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Added: Mon Apr 10 2006
Last Modified: Fri Dec 22 2006
