Abstract: The invention relates to a therapeutic aid suitable for the stabilization of limb bone fractures with surgery. Minimum three radially arranged reinforcing lamellae are extending from the pin shank, the width of which is decreasing from the pin head in the direction of the pin point. The longitudinal dimension reduction of the lamellae is sectional, but continuous within each section. Number of the lamella sections is minimum two, while at junction of the adjacent lamella sections recessed steps are developed toward the longitudinal axis of the pin.The medullary cavity pin according to the invention is applicable with very good result in case of femoral fractures below the buttock, because it is well adaptable to the varying cross section of the medullary cavity, it does not damage the bone, it gives sufficient stability, while the surgery is fast and simple.