Types of displacement in fractures of the femoral neck and observations on impaction of fractures.

In fractures of the femoral neck there may be displacement of different types accounting for the well recognised abduction and adduction fractures with valgus and varus displacement (Nystrom 1938). Between these types there is a transitional form that was described by Waldenstr#{246}m (1924) as the “ fracture impacted in adduction “ and by this author as “ the intermediary type “ (Linton 1944). The title intermediary fracture, which was intended to emphasize the mid-position of displacement between abduction and adduction, has been criticised because the term “ medial fracture “ has already passed into general use as an indication of the level of injury in the femoral neck, a medial fracture being the equivalent of an intracapsular fracture. In the German language intermediary fractures would be described suitably as Ubergangsfrakturen, but it is difficult to find a comparable term in English. This type of displacement is of great significance, and insufficient attention has been paid to it in the literature. The fact that it does indeed exist calls for emphasis. Figure 1 illustrates the displacements in five fractures of the femoral neck. It is evident, from this manner of presentation, that they form a graduated series. All radiographs in the upper row have been taken in the frontal plane and they range from the first, which shows no displacement, to the second which shows valgus displacement, the third which shows the intermediary position, the fourth in which there is an incipient varus position, and finally to the fifth in which there is such varus displacement that the fragments have slipped apart. An increasing degree of outward rotation of the femoral shaft is evident in the progressive prominence of the lesser trochanter. The lateral projections, illustrated in the lower row, show clearly how this recurvation has increased steadily as we progress from the first to the fifth type. These radiographs, selected from different patients, and showing in each case the primary displacement, illustrate different stages in the displacing movement beginning with a valgus position and passing, under increasing recurvation, into a varus position. In adduction fractures the fragments are not actually in varus relationship to each other. The fact is that the peripheral fragment is rotated outwards, round the longitudinal axis of the femur, while the neck is directed forwards so that the femoral head lies on its posterior aspect. This is shown in Fig. 2. All outlines in the upper row show the femoral shaft in an unchanged position; displacement of the femoral head occurs progressively backwards and downwards on the posterior aspect of the neck. This dislocating movement is the same as in Fig. 1, though the projection of the pictures is different. Thus, neither the term “adduction fracture,” nor “varus fracture,” can be considered adequate if it is intended to denote the mutual position of the fragments. In a review of 323 fractures of the femoral neck in which the direction of original displacement was known and analysed by this writer (Linton 1944), forty-seven were abduction fractures (14.6 per cent.), twenty-eight were intermediary fractures (8.6 per cent.), and two hundred and forty-eight were adduction fractures (76.8 per cent.). That these three types of fractures, each with different displacement, were due to different types of injury is often assumed, and if we are to judge from the literature such a conception is widely entertained. Nevertheless, it is probably incorrect and the assumption has been made too readily. In support of this contention, which was first discussed in the author’s article of 1944, certain observations may now be made.