FIG. 1 E THE MONTEGGIA FRACTURE WITH POSTERIOR DISLOCATION OF THE RADIAL HEAD

There are two varieties of the fracture-dislocation originally described by Monteggia (1814), according to whether the head of the radius is dislocated anteriorly or posteriorly. The anterior variety, which is the more common, has received a prominent place in all text-books on fractures, chiefly on account of the frequency with which the dislocation is overlooked (Speed and Boyd 1940, \\‘atson-Jones 1943). The posterior variety, however, has received much less attention and there are few references to it in the literature. Most authorities put the incidence of the posterior variety at 10 to 15 per cent but in a series of ten Monteggia fractures treated during the last year at the Bristol Royal Infirmary no fewer than seven had posterior dislocations of the radial head. The typical injury. Note the fracture of the ulna with anterior comminution andl posterior angulation, the posterior and lateral displacement of the upper end of the radius, and the fracture of the head of the radius. Age and sex incidence-There were five women and two men in the group. In all five women the radiographic appearances were almost identical, but the two men did not follow the pattern so closely. The average age was forty-eight years. Unlike the anterior Monteggia fracture, which occurs frequently in children, this is essentially an injury of middle age, and women seem particularly susceptible. PATHOLOGY The fracture of the ulna-There is a fracture of the ulna about one inch distal to the coronoid process, with a separate triangular or quadrilateral fragment displaced anteriorly (Fig. 1). Several smaller fragments also are usually present on the subcutaneous aspect, but are seldom well seen in the radiograph. There is posterior angulation at the site of fracture, and the distal fragment is displaced towards the radius. (In the more usual anterior type of Monteggia fracture it is the proximal fragment that is displaced towards the radius.) In the five femal